Commissural neurons (CNs) mutually connecting the bilateral spinal cord (SC) are essential neural elements for generating the reciprocal left-right locomotor rhythm. To know characteristics of such mutual connections, we analyzed the projection patterns of single CN axons in the cat lumbar SC with a neural tracing technique using biotinylated-dextran amine (BDA). A small volume of BDA (5-10 nl, 20%) was focally injected into lamina VIII at L5-6 segments. After 2-4 weeks, animals were perfused and fixed, and serial transverse 50 μm sections of L1-S2 segments were made. To visualize BDA labelings, they were processed according to ABC/DAB procedure. At the injection level, many labeled CN axons crossed the midline to the opposite ventral funiculus. Then, they ascended rostrally and/or descended caudally, giving off multiple axon collaterals. Trajectories of single CN axons were traced in continuity from serial sections, and their collateral branching was reconstructed. Although each branching pattern of individual CN axons varied, the axons we identified could be clearly divided into 2 major groups according to their innervation areas. Axon collaterals from the first group always innervated laminae VIII-VII (interneuronal nuclei), whereas those from the second one innervated lamina IX (motor nuclei). Further, axon collaterals arising from a given CN axon in both groups commonly terminated in similar regions at all SC levels along the course of that axon. These findings suggest that the morphology of each CN axon is differentiated in a specific fashion so as to meet its functional role necessitated. [Jpn J Physiol 55 Suppl:S174 (2005)]

View full abstract

The striatum consists mainly of principal neurons, which receive excitatory cortical inputs and project to other basal ganglia structures. The interneurons of the striatum are limited, but rich in variety and complexity. For example, GABA/parvalbumin-contaning interneurons are connected each other by gap junctions, receive cortical inputs and project on the projection neurons. To clarify the functions of the GABAergic interneurons in the striatum, we studied the effect on the activity of striatal projection neurons by the blockade of GABAergic neurotransmission. Using Japanese monkeys, pairs of stimulating electrodes were implanted in the forelimb regions of the primary motor cortex (M1) and the supplementary motor area (SMA) after identification of each area by electrophysiological methods. Single-unit recordings of striatal neurons in combination with local application of drugs were performed with an electrode assembly consisting of an elgiloy microelectrode and a silica tube. The spontaneous activity and the evoked responses by M1- or SMA-stimulation were observed, and then GABAA agonist gabazine (1mM) was injected through the silica tube (0.03μL/min). The duration of excitation evoked by cortical stimulation increased after gabazine injection, while spontaneous activity remained unchanged. These results suggest that GABAergic microcircuits in the striatum have a function of feed-forward inhibition on the firing of striatal projection neurons. [Jpn J Physiol 55 Suppl:S174 (2005)]

View full abstract

Previously we showed that repetitive, high frequency stimulation of the lateral vestibular nucleus induced membrane potential oscillation in hindlimb extensor motoneurons located in the side ipsilateral to the stimulation in decerebrate rats. The frequency of the motoneuronal oscillation was nearly the same as stimulus frequencies, about 30 Hz. To know if the neuronal oscillation was generated in the brain stem, we examined unit activities of various brain stem neurons immediately after cessation of repetitive stimulation in decerebrate rats. It was found some neurons discharged spikes with a time series that had some temporal relation to stimulus pulse series even though stimulation had been terminated. We supposed motoneuronal oscillation evoked by vestibular nucleus stimulation may be in part due to brain stem mechanisms. [Jpn J Physiol 55 Suppl:S174 (2005)]

View full abstract

In Japanese monkeys, our PET study has shown that the primary motor cortex (M1) is activated bilaterally during quadrupedal (Qp) locomotion. We have also shown that unilateral injection of muscimol into M1 hindlimb region produced claudication in the hindlimb contralateral to the injection side. To further examine M1 mechanisms related to the control of Qp locomotion in primates, we recorded neuronal activity in M1 of a monkey walking quadrupedally on the treadmill. Four micro-electrodes were simultaneously implanted into M1 hindlimb region using 4-channel, custom-made micromanipulator. Each electrode was advanced independently and screened daily for single-unit action potentials for up to 2 weeks. Extracellular recordings were made during the execution of quadrupedal locomotion. The treadmill speed was increased or decreased over a range of 0.4-1.6 m/s. The walking animal was videotaped to determine stance and swing phases within a single step cycle. Most units were recordable for more than 2 hours. We found that M1 neurons phasically modulated their discharge time-locked to the step cycle. Most of them showed a roughly linear relationship between peak discharge rate and treadmill speed. These results suggest that M1 output in monkeys directly and/or indirectly acts on spinal circuitries generating a basic pattern of rhythmic activity during simple Qp locomotion in a manner different from that in subprimates. [Jpn J Physiol 55 Suppl:S175 (2005)]

View full abstract

The direct corticomotoneuronal connection, which is highly developed in primates, is supposed to play a role in the control of individual finger movements. To clarify the neuronal mechanism of the functional recovery from the lesion of corticospinal tract (CST), we measured the regional cerebral blood flow (rCBF) by positron emission tomography (PET) using H215O in two monkeys before and after CST lesion at the C5 level. After CST lesion, pre-shaping with both the index finger and thumb was impaired and, therefore, precision grip was triggered by touching the object with the index finger. The dexterous finger movements such as precision grip started to recover in 1-4 weeks and success rate of precision grip totally recovered in 1-3 months. One month after the lesion, significant increases of rCBF in bilateral sensorymotor cortex, contralesional SMA, ipsilesional putamen and cerebellum were observed when the lesional hand was used. After 3 months, rCBF in bilateral ventral premotor cortex and bilateral senorymotor cortex were increased as compared with preoperation. These results indicate that individual finger movements such as precision grip could recover without direct corticomotoneuronal connection, and also suggest that bilateral sensorymotor cortex might be involved in compensatory mechanisms of functional recovery after the CST lesion at C5. [Jpn J Physiol 55 Suppl:S175 (2005)]

View full abstract

The interaction between the fastigial and the Deiters' nuclei may be important substrates for adaptive postural control. To understand information processing through the two nuclei, we investigated effects of vestibular stimulation on fastigial nucleus (FN) neurons with their axons projecting to the lateral vestibular nucleus (LVN), and compared their response characteristics with those of LVN neurons. In decerebrate, immobilized Wistar rats, fastigial neurons were searched for by antidromic stimulation of the lateral vestibular nucleus, which was identified by field potential evoked from the lower thoracic spinal cord. Vestibular stimulation was performed by tapping of the stereotaxic apparatus in which the animals were fixed. For each neuron, tapping was applied to various directions, including fore-, back-, left-, right-, up-, and down-ward directions, and spatial properties of responses were determined.FN neurons responded to tapping of several directions with phasic bursts, of which the shortest latencies were distributed between 3-13 msec. Responding neurons were found mainly in the rostral part of the nucleus. Among FN neurons antidromically excited from the LVN, about half of the cells were responsive to vestibular stimulation. We supposed that these neurons may contribute to adaptive postural control. [Jpn J Physiol 55 Suppl:S175 (2005)]

View full abstract

Human psychophysical studies proposed that the control system of convergence eye movement included both feedback and open-loop controllers. The neuronal basis of this hypothesis was sought in the lateral suprasylvian cortex (LS), one of the extrastriate visual cortex of cat where microstimulation evoked convergence eye movement. Cats (n=5) were trained by a set of stimuli: an alarm signal (blinks of an LED, and buzz sound) preceding the target movement by 4 sec. After training, open-loop convergence (convergence eye movement elicited after buzz sound but before the target onset) was found in 60% of trials. Then GABA_A agonist, muscimol (4μg/μl,0.5μl x 3) injected locally into their LS. Amplitudes of ordinary convergence were significantly reduced by muscimol injection, while neither those nor probabilities occurence of open-loop convergence were changed significantly. We also employed buzzer only or LED only alarm signal instead of visuo-audio combined alarm signal. Cat (n=2) could learn to evoke open-loop convergence as well as training with combined alarm signal. These results suggest that GABA_A inhibition plays a different influence on the neuronal circuits in the LS, controlling the ordinary and open-loop convergence in response to multimodal alarm signal. [Jpn J Physiol 55 Suppl:S175 (2005)]

View full abstract

To understand the functional differentiation between dominant and non-dominant limbs in human upright standing, electromyographic (EMG) activities were analyzed while subjects stood on a rocking platform. EMG activities were recorded from ankle and knee joints muscles of both limbs. Subjects were instructed to stand on the rocking platform so that they rocked in the saggital plane. Movements of the platform, equivalent to fore and back movements of the subjects, were recorded by a force plate (center of pressure, COP). Mean EMG amplitudes of ankle extensors (m. triceps surae, GS) and flexor (m. tibialis anterior, TA) were higher in the dominant side than in the non-dominant side. Nevertheless mean EMG amplitudes of knee joint muscles were rather complicated; some muscles of the dominant side could show lower amplitude than those of the non-dominant side. When the COP marked the most fore and back points, muscles of the front side and those of back were activated 50-300 msec prior to the respective times. Between dominant and non-dominant limbs, the activities of the dominant muscles preceded about 10 ms to those of the non-dominant ones. It was supposed that dominant limb muscles were primarily used in dynamic postural control of human upright standing. [Jpn J Physiol 55 Suppl:S176 (2005)]

View full abstract

When rats are dropped from the supine position, the animals rotate their body in the air, and land on their feet (the air righting reflex). Vestibular input is thought to play crucial roles for elicitation of the air righting reflex. Nevertheless precise mechanisms inducing the reflex were unknown. To understand of functional roles of vestibular afferent input in eliciting the air righting reflex, we examined effects of vestibular lesions and stimulation on air righting movements. Furthermore, affected air righting movements were examined in detail by myographic activities. Lesions and stimulation were applied to vestibular nerves, and the lateral vestibular nuclei in Wistar male rats, in which electrodes for lesion and stimulation were implanted. Electromyographic activities were recorded from bilateral back muscles at the neck and lumbar. Unilateral lesions of the lateral vestibular nucleus elicited air righting movements with body rotation in too much extent (overshooting); in some cases repetitive rotation was observed. In such animals stimulation of the lateral vestibular nucleus of the intact side modified righting movements. In some cases, rotatory movements of the righting was facilitated, but in others they were weakened. The air righting movements with repetitive rotation was characterized by rhythmic bursts of back muscles, of which interburst intervals corresponded to the body rotation. It was suggested that vestibular input and the lateral vestibular nucleus could play important roles with complicated manners. [Jpn J Physiol 55 Suppl:S176 (2005)]

View full abstract

We have suggested that lamina VII interneurons in the lower lumber segments, which receive inhibition from flexor reflex afferents and a group of Ib interneurons, can mediate a generalized motor inhibition that is induced by stimulating the medullary reticular formation (MRF; Takakusaki et al., 2001, 2003). Here we examined whether the interneurons satisfying above criteria could exert inhibitory effects upon hindlimb motoneurons in the lumbosacral segments. Twenty four lamina VII interneurons in the L6 segment were antidromically excited by stimulating the motoneuron pools at L7 and S1 segments. The minimum latency for the antidromic responses was 1.10 + 0.29 ms. Stem axons of 10 and 3 interneurons were located in the ventral and ventrolateral funiculi, respectively. Effects of single interneurons upon hindlimb motoneurons were studied by spike-triggered averaging. Among the combinations of 38 interneurons and 203 motoneurons, monosynaptic inhibitory connections were revealed between 21 interneurons and 37 motoneurons. Ten and eleven interneurons were identified to inhibit extensor and flexor motoneurons, respectively. Although eleven interneurons induced IPSPs in plural motoneurons, each interneuron did not induce IPSPs in motoneurons of antagonistic relationship. These results suggest that a group of lamina VII interneurons in L6 segment descend through ventral or ventrolateral funiculi and inhibit either extensor or flexor hindlimb motoneurons. Signals from the MRF can simultaneously activate these lamina VII interneurons so that generalized motor inhibition (muscular atonia) is induced. [Jpn J Physiol 55 Suppl:S176 (2005)]

View full abstract

To pursue objects of interest moving slowly in space, smooth pursuit requires precise control of vergence angles and interacts with vestibulo-ocular reflex (VOR). The floccular region plays a crucial role in generating smooth pursuit and modifying rotational VOR, and contains vergence signals (Miles et al. 1980). To examine discharge characteristics of floccular Purkinje (P) cells further, we first examined simple spike activity of 112 P cells during smooth pursuit and vergence at 0.5Hz (±5°) in 3 Japanese macaques. The majority (63%) responded to both eye movements, 24% responded only during vergence, and 13% responded only during smooth pursuit. Activity of the majority of P cells was modulated in proportion to vergence eye velocity and position. We also examined P cell discharge during sinusoidal linear (fore/aft) translation at 0.3Hz (±10cm) while the target moved in space with the same amplitude and phase as the chair (LVOR cancellation) or remained stationary in space (LVOR x1). Most P cells did not respond during LVOR cancellation but responded during LVOR x1 and their responses were correlated with compensatory vergence eye velocity. Some of these P cells responded during rotational VOR cancellation in yaw or pitch plane as reported previously. These results indicate that the majority of floccular P cells carry both smooth pursuit and vergence eye movement signals but do not receive otolith inputs. [Jpn J Physiol 55 Suppl:S176 (2005)]

View full abstract

Smooth pursuit is an ocular function that allows us to have a good vision of a moving stimulus. It has been demonstrated that the latency of pursuit is affected by introducing a temporal gap between the extinction of the central fixated target and the appearance of the eccentric, moving target (Krauzlis and Miles, 1996). Here, we examined whether the presence of temporal gaps affects the gain of visuo-motor transmission, by comparing ocular responses to a brief motion (perturbation) of a visual stimulus with and without a preceding gap in 3 human subjects. At the beginning of each trial, a stationary, green spot (fixation target) was appeared on the center of the screen. After the subject established a fixation, a red spot turned on at 1 deg right/left of the green spot. Then the green spot turned off and the red spot moved at 20 deg/s for 0.6 s. In perturbation trials, a brief motion (perturbation) of the red spot (sinusoidal motion of 10 Hz at the peak velocity of 20 deg/s for 0.1 s) was inserted before the ramp motion. These trials allowed us to measure the gain of visuo-motor transmission at the initiation of pursuit. In gap-perturbation trials, the green spot was blinked for 0.2 s immediately before the perturbation, to measure the gain of visuo-motor transmission in the presence of a preceding gap. We found that the ocular responses to the perturbations were significantly larger when there was a blink than when there was no blink. This result suggests that the presence of temporal gaps increases the gain of visuo-motor transmission. [Jpn J Physiol 55 Suppl:S177 (2005)]

View full abstract

In daily life, smooth pursuit is performed by coordination of eyes and head movements (i.e. gaze pursuit). Previous studies indicate that caudal parts of FEF contain pursuit related neurons and that the majority of them carry gaze velocity signals during passive whole body rotation. However, because these studies were performed in head-fixed conditions, it is unknown whether their signals are related to active gaze pursuit. To dissociate gaze from eye and/or head pursuit, in this study 2 monkeys were trained to move their heads to pursue a reward feeder during eye pursuit of a laser spot while their heads were free to rotate about a vertical axis. As a search task, the feeder and spot moved together at 0.3 Hz (±15°) and the monkeys tracked the feeder and spot by gaze pursuit. Responding neurons were tested for eye pursuit for spot motion while the feeder was stationary and head pursuit for tracking the feeder while the spot was stationary. Of 99 responding neurons in the caudal FEF, the majority (62%) were modulated during gaze, eye and head pursuit similarly. The second group (25%) was modulated during gaze and eye pursuit similarly but only weakly during head pursuit when gaze was stationary. Their activity was similar to passive gaze velocity neurons. A minority of neurons was modulated only during head pursuit with minimal modulation during eye pursuit (8%) or only during gaze pursuit (5%). These results suggest that the majority of FEF pursuit neurons are modulated during both eye and head pursuit. [Jpn J Physiol 55 Suppl:S177 (2005)]

View full abstract

We re-focused on a basic question: what kind of information is encoded by primary motor cortical (M1) neurons during arm movements. While preceding studies used time-averaged neuronal activity for answering the question, we have focused on temporal neuronal activity to correlate it with time-varying variables related to arm movements. Two Japanese monkeys were trained to perform a traditional center-out task on a horizontal plane with holding a handle of a manipulandum. The hand trajectory was recorded together with M1 neuronal activity. We applied multiple linear regression analysis to correlate temporal unit activity with the following 4 different sets of movement variables; 1) kinematics variables (acceleration, velocity and position) in Cartesian (or extrinsic) coordinates (Ks), 2) kinematics variables in joint (or intrinsic) coordinates (Kj), 3) dynamics variables (inertial force, centrifugal force + Coriolis force and friction around the joints) in the extrinsic coordinates (Ds), and 4) dynamics variables in the intrinsic coordinates (Dj). Out of 191 task-related units which were responded to passive movements of elbow and/or shoulder joints, 125 (65%), 42 (22%), 16 (8%) and 8 (4%) units were best fitted with the Dj, Ds, Ks and Kj, respectively. This suggests that a majority of the M1 neurons encode dynamics variables of arm movements, with preference of joint torque variables in the intrinsic coordinates to hand force variables in the extrinsic coordinates. [Jpn J Physiol 55 Suppl:S177 (2005)]

View full abstract

The STN provides glutamatergic projections to both pallidal segments and SN. In these experiments we examined the prevalence of excitatory and inhibitory responses to STN stimulation in the primate SN, and mapped the topography of these responses by systematically changing the stimulation location in the STN. Two monkeys received chronic recording chambers directed at STN and SN. One chamber was used to carry out electrical stimulation of the STN with a microelectrode (monophasic stimulation at 1/s, pulse width 50 μs, amplitude < 300 μA), and the other to simultaneously record the neuronal activity in SN, using standard extracellular single-unit recording techniques. Peristimulus histograms were used to evaluate responses to stimulation. Excitatory responses were scattered in a broad area of the SN when the stimulation electrode was in the medial part of the STN. However, responses were confined to portions of the SN when the stimulation electrode was in the lateral part of the STN. Same tendency was found for inhibitory responses. The results suggest that total output of the SN evoked by stimulation changes significantly depending on the stimulation location in the STN. [Jpn J Physiol 55 Suppl:S177 (2005)]

View full abstract

The role of presynaptic inhibition in normal behavior is largely unknown. We recently reported that the monosynaptic input from cutaneous afferents to spinal interneurons is suppressed during active movement by presynaptic inhibition. To further investigate this phenomenon, we examined the modulation of primary afferent depolarization (PAD) in monkeys performing a wrist flexion-extension task. We delivered microstimuli (1-20μA: 3-10Hz) continuously to the intraspinal sites where orthodromic monosynaptic response were evoked from the superficial radial (SR) nerve (containing purely cutaneous afferents), and recorded antidromic volleys (AVs) in the SR through a tripolar cuff electrode. We calculated the average size (area) of individual volleys in each behavioral epoch. Single stimuli sometimes evoked multiple (2-8) AVs with different latencies, possibly by activating afferent fibers with different conduction velocities. Task-dependent modulation of the volley size was found in 56% of recorded AVs, usually in shorter latency volleys. Facilitation during active movement (flexion and extension) was most common (p< 0.05). Suppression of PAD was also found during active extension. Facilitation of PAD started before EMG onset in both flexion and extension trials, suggesting that PAD is induced in part by descending commands. These data suggest that low-threshold cutaneous input can be modulated presynaptically in a behaviorally relevant way by central control of PAD. [Jpn J Physiol 55 Suppl:S178 (2005)]

View full abstract

It is necessary to coordinate the movement of multiple limbs in various tasks in daily life, such as clapping hands, walking, swimming or driving a car. As a model of the multi-limb coordination, we analyzed the rhythmic flexion/extension of hand and foot of two limbs. Eight normal subjects (4 females and 4 males) lay in supine position. Rotation angles of hands and feet were measured with potentiometers. EMGs were recorded from the flexor and extensor muscles. Subjects performed in-phase (isodirectional) or anti-phase oscillations of two limbs of all possible pairs of hands and feet for 10 sec to the sound of metronome at 5 different rates from 1 to 3.3Hz. Each trial was evaluated with the cross-correlation of the movement of two limbs. The higher the rate of oscillation, the lower the performance for all tasks. The movement of homologous limbs (a pair of hands, or feet) could be done better than that of inhomologous limbs (hand and foot) both in in-phase and anti-phase conditions. The performance of the movement of hand and foot depended greatly on the combination of limbs and in/anti-phase condition. In the case of in-phase condition, movements of ipsilateral limbs and contralateral limbs are equally easy. But in the case of anti-phase condition, the movement of ipsilateral hand and foot is more difficult than the movement of contralateral hand and foot. EMG activity showed that the extensor muscles mainly worked during these movements. [Jpn J Physiol 55 Suppl:S178 (2005)]

View full abstract

Mastication is consisted of various jaw movements commencing with ingestion and ending with swallowing. The progress of mastication is dependent on the interaction of the motor mechanism with variable characteristics of chewed food. In the guinea pig, jaw movement patterns with the progress of mastication have not been clarified under freely moving condition. In this study we recorded EMG activities bilaterally from the masseter and the digastric muscles and simultaneously the jaw movements using a magnetic sensor system. The recordings were made for 1-hour ad libitum fed after 5 hours fast. Masticatory behavior was divided into two stages, (1) an intake-stage representing food intake and transport, and (2) a chewing-stage, food chewing. During the intake-stage, vertical jaw movements were associated with synchronous activations of bilateral masseter muscles. The chewing-stage was characterized mostly by alternate lateral jaw excursions with alternate EMG activity in right and left masseter muscles. Within the chewing-stage, jaw movement patterns altered along with the progress of mastication. These data suggests that masticatory stages in guinea pigs can be estimated by the EMGs and jaw movements. [Jpn J Physiol 55 Suppl:S178 (2005)]

View full abstract

A surface-negative (s-N), depth-positive (d-P) premovement potential was recorded by electrodes implanted on the surface and at a 2.0-3.0 mm depth in areas 5 and 7, and in the premotor, motor and somatosensory cortices in monkeys on self-paced hand movements. The monkeys were also tasked with visuo-initiated hand movements. Cortical field potentials were recorded by the above-mentioned electrodes while they were learning to accomplish the movements, and then analyzed. It was found that in the early learning period (association of stimulus with movement), an s-N, d-P potential, at about 80 ms latency from stimulus, appeared in the left prefrontal cortex and a few days later also in the left area 7, both potentials gradually increased in amplitude. On the other hand, in the late learning period (making movement quicker and more appropriate), an s-N, d-P potential appeared in the motor cortex, and also in the somatosensory cortex and area 5 at a longer latency from that in the motor cortex, in all cases contralateral to the operating hand, and these potentials gradually increased in amplitude. Aligning the data by movement onset indicated that these s-N, d-P potentials in the motor and somatosensory cortices and in area 5 were premovement potentials related to motor execution, but this was not the case in area 7. It is suggested that area 7 is related to different functions: visual processing or selective attention on visuo-initiated hand movements and motor functions on self-paced hand movements. [Jpn J Physiol 55 Suppl:S179 (2005)]

View full abstract

It was reported that a surface-negative, depth-positive (s-N, d-P) cortical field potential (no-go potential) appeared in the dorsal bank of the principal sulcus with suppression of movements in the monkey [1]. The s-N, d-P potential is due to the activation of superficial thalamo-cortical (T-C) projections. In the monkey, we identified thalamic nuclei which sent superficial T-C projections to the prefrontal cortex by recording cortical field potentials induced by thalamic stimulation under pentobarbital anesthesia with electrodes implanted on the surface and at a 2.5–3.0 mm depth of the cortex. The stimulation of the ventral anterior nucleus (VA) or mediodorsal nucleus (MD) evoked superficial T-C responses in dorsal parts of areas 8 and 46, which included the dorsal bank of the principal sulcus. The distribution of superficial T-C responses by the VA stimulation in the dorsal bank of the principal sulcus was restricted within the caudal part. These results suggest that the no-go potential was generated by superficial T-C projections from the VA or MD. In addition, the stimulation of the cingulate cortex (area 23, 24) also induced an s-N, d-P potential in much the same cortical area as that in which superficial T-C responses by the stimulation of the VA or MD distributed. This indicates that the VA, MD-prefrontal projection, a putative circuit responsible for the no-go potential was possible to be activated by the cingulate-thalamic projection. [1] Sasaki K, Gemba H, Exp Brain Res 64: 603-606, 1986 [Jpn J Physiol 55 Suppl:S179 (2005)]

View full abstract

We have reported that tongue and jaw movements in cats were controlled by pyramidal neurons in area P (the lateral wall of the presylvian sulcus) (Hiraba et al., 1993; Hiraba et al., 2000; Hiraba and Sato, 2005a). Namely, many mastication-related neurons (MRNs) that were recorded in the area P, related to movements of jaw and tongue, and intracortical microstimulation at MRN recording sites evoked tongue protrusion and jaw-opening without deviation. In comparison with the normal cat, cats with lesion in the unilateral area P produced the abnormal tongue protrusion and wide jaw-opening during mastication. Furthermore, callosal connection of bilateral area P was examined by the WGA-HRP. Thus, I assume from these results that pyramidal cells with the commissural fibers may exist between bilateral area P. To investigate these suggestions, changes in orofacial behaviors and in the regional cerebral blood flow (rCBF) of the unilateral area P during mastication were examined after each injection of GABA agonist (1.0μg/μl muscimol, .2μl) and GABA antagonist (1.0μg/μl bicucurine, 4μl) into the contralateral area P. Based on these findings, the adequate condition of tongue and jaw movements during licking may be conducted by GABAergic interneuron between the commissural fiber and pyramidal neuron. [Jpn J Physiol 55 Suppl:S179 (2005)]

View full abstract

Mirror neurons in the ventral premotor cortex (F5) and a part of the inferior parietal cortex (area PF) of the monkey were active during execution of the hand or mouth action and observing same action made by another individual. However, function of the mirror neurons of the macaque is still uncertain. In this experiment, we studied whether neurons in area PF, especially mirror neurons, correlate to monitoring self-generated action or not. We recorded single cell activity from area PF during the hand manipulation task. The monkey was presented image of the hand and object on a screen which was taken by a video camera and required to manipulate the object seeing them. Further, we also presented movies of monkey’s hand movement or experimenter’s hand action, and the monkey just fixated on it without any hand movement. Some neurons related to the hand manipulation task responded to the movie of own hand movement. This visual response may reflect visual feedback during hand movement. Many of them responded with the movie of hand action by the experimenter. These results suggested that mirror neurons in area PF were also responsive to the view of own hand action. We also found this visual response was less active in the delayed feedback than in the real time. We found that the movement time was extended in the human grasping movement with the delayed visual feedback. In conclusion, area PF may be correlated with self-generated action monitoring. Time contingency of the sensory feedback to hand action is very important for activity of the neurons. [Jpn J Physiol 55 Suppl:S180 (2005)]

View full abstract

The neural stem cells (NSCs) possess the self-renewal and multipotential abilities and are located not only in the development mammalian brain but also in the adult brain, especially abundant in the anteior subventricular zone (aSVZ) and subgranular zone (SGZ) of hippocampal dentate gyrus. In the present study, we examined the effects of sleep deprivation and rebound sleep after sleep deprivation on the proliferation and the differentiation of the NSCs in aSVZ and SGZ of adult rats. Male SD rats were deprived of total sleep for 96 hr by treadmill method and some rats were thereafter returned to their home cages. Rats were injected with BrdU (200 mg/kg i.p.) at the midpoint (48 hr after) or the endpoint (96 hr after) of treadmill and their brain were removed 48 hr or 6 hr after, respectively. The number of BrdU-incorporated cells in the aSVZ and the SGZ were quantified by BrdU-immunohistochemistry. We found that sleep deprivation failed to affect the number of BrdU-positive cells in the aSVZ and SGZ. However, rebound sleep after sleep deprivation increased the number of BrdU-positive cells in the SGZ, but not in the aSVZ. These results suggest that sleep changes the proliferative activity of the NSCs in the SGZ of the dentate gyrus. [Jpn J Physiol 55 Suppl:S180 (2005)]

View full abstract

The weakly electric fish, Gnathonemus petersii, emits electric organ discharges (EOD) from the tail electric organ. In the electrosensory systems, variations in the discharge rate and amplitude of each EOD enable the fish to detect local distortions of the electric field as ‘electrolocation’, and broad distortions evoked by other fish as ‘electrocommunication’. In the present work, we examined how sensory stimuli changed the frequency of EOD in electrolocation and communication. In the behavioral experiments, each fish had it’s own specific frequency during free swimming. When a metal rod was placed near the side of the fish, the frequency of EOD transiently increased from 5-10 Hz to c.20 Hz, while with the broad stimuli applied between the head and tail, the fish responded with a interval of EOD tuned to the stimulus frequency, with a minimum latency of c.11 ms. In the presence of propofol or strychnine, EOD frequency decreased, but with a sharp tuning. The minimum latency for the EOD did not change. In the presence of Ketamine frequency tuning still remained, but the fixed latency became unclear. With the broad stimulation, the ratio of tuned EOD against untuned EOD was larger than that with local stimulation. The evidence suggests that GABAeargic pathways modulate the frequency tuning of EOD, while the glutamatergic neurons modulate the latency. [Jpn J Physiol 55 Suppl:S180 (2005)]

View full abstract

We have shown that monkeys can learn the sequential movements of reaching and grasping tweezers placed at their front-right with their right hand, bringing the tips of tweezers to a piece of food placed at their front-left, and picking it up with them. In the task, the tweezers were placed with the tips facing left toward the food (9 o’clock). When the tweezers were placed in the reverse direction (3 o’clock), monkeys initially picked them up backwards and brought the reverse end to the food in a vain attempt to grasp the food. They repeated the same action, suggesting that they did not understand that the tip end must be used, and sometimes threw the tweezers away, probably due to accumulated stress. With continued training, monkeys were able to foresee the outcome and aborted the reach movement on the way to the food. Then, suddenly they showed a new strategy of first rotating the tweezers by 90-180 degrees with their fingers, which enabled them to grasp the tweezers properly and pick up food successfully. When the tweezers were placed facing different directions, monkeys developed strategies that were most efficient for the situation, substituting wrist rotation rather than tweezer rotation when appropriate. These findings show that monkeys can understand tweezers as an object used for picking up food and can invent strategies to use them in various situations, demonstrating that monkeys can use tweezers as a “tool”. [Jpn J Physiol 55 Suppl:S180 (2005)]

View full abstract

Anatomical studies have shown that there are reciprocal connections between the insular cortex and the amygdala. In the present study, we examined the effect of the chemical stimulation of the amygdala on the neuronal activity in the insular cortex in anesthetized rats. Fifteen neurons in the insular cortex were recorded by using extracellular recording technique. Of the 15 neurons, 12 showed evoked responses (evoked spikes and/or field potentials) to electrical stimulation of the superior laryngeal nerve, which conveys afferent information from the sensory organs in the larynx (taste buds and free nerve endings). The mean latency of the evoked responses was 38.5 ms. Eleven of these 15 insular cortex neurons showed evoked spikes or field potentials to electrical stimulation of the amygdala. The mean latency of the evoked responses was 24.5 ms. No neurons recorded in the present study were the projection neuron to the amygdala; the responses were not identified as an antidromic response. All neurons showed an excitatory and/or inhibitory response to chemical stimulation of the amygdala (microinjection of glutamate). Most neurons (10 of 15) were inhibited. Three showed an excitatory response, and then were inhibited. Two showed an excitatory response to chemical stimulation. These results indicate that neuronal activity in the insular cortex was influenced (mostly inhibition) by activation of the amygdala neurons. [Jpn J Physiol 55 Suppl:S181 (2005)]

View full abstract

We investigated interaction between neural activities (I- or C-response) in rat somatosensory cortex evoked by ipsi-(I-stim) or contra-lateral electrical stimulation (C-stim) of the whisker face area, by recording electric field potentials (FP), fluorescence of voltage-sensitive dye or local changes in cerebral blood flow (reflection of 605 nm light). Stimulation are one single square pulses (0.2-3.0 mA, 0.5ms duration). Latencies [or latency of peak value] were 6.3-16 ms [9.5-26 ms] in C-response and 14-19 ms [15-35 ms] in I-response, decreased in parallel with intensity of C-stim, but were almost constant (16.4 ± 1.7ms) [23.5 ± 4.2] with I-stim. Peak value increased in parallel with intensity of both I- and C-stimulation, but their time course differed between I- and C-responses. Area of the FP increased proportionally with intensity of C-stim, but they dispersed much with I-stim. When used at intensity of a half of max value of stimulation (1/2 T), C-response (or I-response) were suppressed for 90-100 ms after I-stim (or C-stim), and recovered within 150-200 ms. Similar results were obtained with fluorescence-recording and 605nm light reflection. [Jpn J Physiol 55 Suppl:S181 (2005)]

View full abstract

Many investigators have demonstrated the association between anxiety and motor performance (balance, posture control and/or coordination) in human. Physiological mechanism of the anxiety-motor linkage, however, remains completely unknown. In this study, we determined whether the anxiety induced by the A2aR-knockout or injection of caffeine which is a non-selected adenosine antagonist would affect the motor performance in mice. The anxious state was evaluated by elevated plus-maze, and the motor performance was measured using the rota-rod. In results, anxiety was stronger and motor performance was lower in both the A2aR-knockout and caffeine-treated mice in comparison to the wild-type and vehicle-injected mice respectively. On the other hand, wire hang test, by which the neuromuscular strength was estimated, showed no differences among A2aR-knockout, caffeine-treated and control mice. Furthermore, EEG power analysis also showed no significant differences among them. These findings suggest that the inhibition of the A2aR function induces the impaired motor performance in parallel with the anxiety without affecting the muscle strength and vigilance state. [Jpn J Physiol 55 Suppl:S181 (2005)]

View full abstract

To support an understanding of neural basis of time perception, we attempted a duration discrimination task, and recorded single-unit activity from the striatum in the monkey. In front of a Japanese monkey (Macaca fuscata), two visual cues (C1 and C2; a blue or red-colored square for each) were successively displayed for different duration from each other. Each cue (C1 or C2) was followed by a delay period (D1 or D2, respectively). Longer and shorter cues were presented in random order, and the subject was required to choose the longer-presented colored cue. The greater probability of correct response was associated with a decrease in short cue duration. We found striatal neurons that showed significantly phasic activity in D1 or D2 after shorter cue, and those that showed increasing responses during C2 in C2-longer trials. The results suggest that striatum neurons closely relate to the monitoring and/or judgement in the duration discrimination. [Jpn J Physiol 55 Suppl:S181 (2005)]

View full abstract

The prefrontal cortex (PFC) is an important structure for working memory. However, it is not the only brain structure responsible for working memory. Other brain areas, including the mediodorsal nucleus (MD) of the thalamus and the hippocampus (HP) have also been found to play significant roles in working memory, and both areas send monosynaptic projections to the medial prefrontal cortex (mPFC) in rats. To gain an understanding of the neural mechanisms of working memory, it is necessary to examine the functional interactions between the PFC and other brain structures. As we have observed that both HP-mPFC and MD-mPFC pathways express long-term potentiation (LTP), thought to be a model for learning and memory processes, this study focuses on interactions of synaptic plasticity in the MD-mPFC and HP-mPFC projections in an evoked potential level. Under the condition that recording either the MD or HP stimulation evoked field potential in the mPFC, twenty or fifty 100 µs-pulses at 250 Hz were applied 12 times at 10 s intervals to induce weak LTP in the MD-mPFC or strong LTP in the HP-mPFC pathway, respectively. When the weak LTP induction of the MD-mPFC was synchronized with strong LTP induction of the HP-PFC, the MD-mPFC revealed the cooperative effect of the LTP (about +10%). Our results suggest that the mPFC allows MD information to be positively associated with that of the HP. [Jpn J Physiol 55 Suppl:S182 (2005)]

View full abstract

Although the neuronal spike counts across repeats of single condition often vary considerably, it has been considered suitable to describe the responses according to mean and variance because the distributions have been considered unimodal. Recently, Wiener and Richmond (2003) pointed out that even unimodal distributions (V1 neuronal responses) are not consistent with simple, single Poisson processes, and could be fit nicely as mixtures of a few Poisson processes, raising the question of whether such fits to the firing rate distribution arose as a computational tool, or as a consequence of some state change in the neuronal responses. We have recorded single neuronal responses from anterior insula, anterior cingulate cortex, and ventral striatum that we conceptualize as part of a system related to the balance between work and reward. The raster plots of those responses seem to have trials falling into 2 or 3 groups based on the spike counts in single task condition. Here, we report that more than 95 percent of those neuronal responses were well fit by mixtures of 3 or fewer Poisson processes. Moreover, substantial number of them showed changes in the ratio of each Poisson process in relation to the task states (progress through trials toward reward in this case). These mode changes of the neurons might be related to behavioral or cognitive factors. [Jpn J Physiol 55 Suppl:S182 (2005)]

View full abstract

To evaluate the role of visceral vagal afferent fibers and glucocorticoid in CIS-induced anorexia, we observed the food intake and body weight in intact or vagotomized rats after twice administration of 2 mg/kg/day CIS via the intraperitoneal (ip) route with or without methylpredonisolone (MPN). Vagotomy was performed by one of three ways: (a) selective vagotomy in hepatic (HVX), gastric (GVX), or celiac (CVX) branches; (b) combined serective vagotomy; (c) total vagotomy under diaphragm. HVX attenuated significantly the CIS-induced feed suppression and body weight loss. However, neither GVX nor CVX changed the CIS-induced impairment of food intake and loss of body weight. When animals were received with combined selective vagotomy such as hepatic plus either celiac (HVX+ CVX) or gastric branches (HVX+GVX), the CIS-induced anorexia was markedly recovered to 83% and 78%, respectively, of that seen in intact animals administered with saline. The anorexia and weight-loss evoked by CIS was prevented markedly in rats given either 30 mg/kg MPN via ip route or 100 μg/kg MPN via icv route. However, 100 μg/kg MPN given via the ip route did not attenuate the CIS-induced anorexia. We conclude 1) that afferent signals via the hepatic vagus branches play an important role in the feed-suppression induced by CIS, 2) that both of gastric and celiac vagal afferent signal may be involved in the CIS-induced feed suppression, and 3) that ameliorating action of MPN to the CIS-induced anorexia would be triggered within both visceral regions and the central nervous system. [Jpn J Physiol 55 Suppl:S182 (2005)]

View full abstract

The prefrontal cortex (PC), hippocampus (HP) or amygdala (AM) reportedly control locomotor activity, which is an essential index of the standardized animal test for several neurotoxicity studies. To investigate the relationship between the brain regions/pathways and locomotor control, we compared the effects of bilateral and crossed unilateral lesions induced by ibotenic acid on locomotor and rearing activities, and studied the effect of repetitive measurement at a 24-h interval by applying footshock (below 0.3 mA, reportedly insufficient to condition fear) at the first measurement. In an open-field cage (45 cm square) equipped with shock grids, all the sham-operated groups gradually decreased their locomotor or rearing counts to 30% during the first measurement for 1 h. During the second measurement, each curve was consistently lower than the initial version. Remarkably, HP-AM disconnection increased the initial curves for locomotor and rearing activities to about 200 and 400% of the sham group but not to the extent of the second ones. We will report on other lesion effects on locomotor and rearing activities and discuss the relationship among these brain regions/pathways, locomotor/rearing control, and learning/memory/emotion. [Jpn J Physiol 55 Suppl:S182 (2005)]

View full abstract

It has been demonstrated that music has beneficial effect on various types of performance in human. In the present study, we examined the effect of early music exposure on behavior in adult mice, and measured brain-derived neurotrophic factor (BDNF) and its receptor, tyrosine kinase receptor B (TrkB), which play a critical role in synaptic plasticity, learning and memory. Additionally, we measured 3-phosphoinositide dependent protein kinase-1 (PDK1) and mitogen-activated protein kinase (MAPK), which are downstream targets of two main pathways in BDNF-TrkB signaling. For prenatal 7 days plus postnatal 60 days, mice were exposed to either music (Mozart Sonata, K. 448), white noise or silence, and were then tested for 8 days in a cross maze. The music-exposed mice completed the maze with fewer errors than the other groups. BDNF protein in the cortex, hippocampus, cerebellum and brainstem were assessed by ELISA kit. In the cortex, BDNF in music-exposed mice was significantly decreased compared to white-noise exposed mice. Using Western blotting, we found that the protein of TrkB and PDK1 were significantly increased by the exposure to music, while MAPK was not changed. These results suggest that repeated exposure to music during perinatal period has an influence on BDNF-TrkB signaling and their intracellular signaling pathway including PDK1, and thus may induces the improved learning and memory functions in mice. [Jpn J Physiol 55 Suppl:S183 (2005)]

View full abstract

We reported that gonadal steroid hormones sustain the stress-induced acetylcholine (ACh) release in the hippocampus in both sexes of rats. Since aromatase in the brain converts testosterone to estradiol, circulating testosterone activates both androgen and estrogen receptors in male rats. In the present study, to further determine the steroid hormone receptor which contributes to sustain the ACh release in male rats, an in vivo microdialysis study was performed after the letrozole (an aromatase inhibitor) or flutamide (an androgen receptor antagonist) treatment in male rats. Daily treatment with letrozole (5 mg/kg), flutamide (15 mg/kg), or vehicle was performed orally for 1 weeks. ACh concentrations in dialysates were assayed by the HPLC system, and the restraint stress was applied from 1200 h to 1300 h. Prior to the stress exposure, the ACh release was low in all male rats, and neither letrozole nor flutamide treatment showed significant effects on the basal ACh release. The ACh release in the hippocampus in male rats showed a prompt increase within 15 min after the onset of the restraint stress, but the increase in ACh release in letrozole- or flutamide- treated male rats was of a significantly smaller magnitude than vehicle-treated male rats. This decrease in the stress response was equivalent to that in gonadectomized rats. These results suggest that both androgen and estrogen receptors contribute to sustain the stress-induced acetylcholine release in the hippocampus in male rats. [Jpn J Physiol 55 Suppl:S183 (2005)]

View full abstract

Many reports have shown the presence of D-serine in the forebrain and the co-localization of D-serine with N-methyl-D-aspartate (NMDA) receptor. D-Serine is thought to activate the NMDA receptor, which has important role in the long-term potentiation (LTP) and learning. To evaluate the role of D- serine, spatial learning using the Morris water maze and LTP in the CA1 area of hippocampal slice preparation were compared between the wild-type mice and mutant mice lacking D-amino-acid oxidase, an enzyme which metabolizes D-serine. The platform search times in the water maze were not different in the initial phase of training. However, in later phase of training, the platform search time was significantly shorter in the mutant mice than in the wild-type mice. Furthermore, platform quadrant search time was significantly longer in the mutant mice than in the wild-type mice. Tetanus-induced LTPs, measured as the increase of the field EPSP slope after tetanus stimulation, were observed in the CA1 area of both type mice. However, tetanus-induced LTPs were significantly larger in the mutant mice than in the wild-type mice. We suggest that D-serine rich in the mutant mouse brain increases hippocampal LTP and then facilitates spatial learning. [Jpn J Physiol 55 Suppl:S183 (2005)]

View full abstract

We conducted the 2-back test on 15 young student volunteers in order to investigate the effects of different loads of exercise on the working memory. Subjects exercised 10 min. on an ergometer cycle with loads in such a way that their heart rate attained 10, 30, or 60% of the predicted maximal heart rate (HRmax). The experiment consisted of a pre-2-back test, then exercise and then a post-2-back test with the intervals between experiments longer than one day apart. The order of exercise was distributed evenly among subjects. The 2-back test consisted of showing one three-lettered card after another on a PC screen with a given time interval to each subject. Three letters of every card were chosen randomly from a 71 letter pool which consisted of 26 English alphabetical letters and 45-Japanese syllabary ones so that the three-letter composition was meaningless and had a rather low probability for the subject to guess the composition as well. They were then asked to answer the exact lettered serial sequencing presented on the screen two back for five minutes. Mean results of the 2-back test after each exercise was compared with that before exercise using a dually tailed t test. After 10, 30 and 60% exercise, the results were significantly augmented (p=0.01, p=0.002 and 0.00003, respectively). Present results suggest that exercise could have activating influences on the cognitive power in young normal humans. [Jpn J Physiol 55 Suppl:S183 (2005)]

View full abstract

Enumeration includes two cognitive processes. One is subitizing (enumeration of small number of objects at once) and the other is counting (a serial process for enumeration of items or events). However the neural mechanism underlying these processes remains unclear. To investigate a cortical mechanism of enumeration, we measured brain activity using functional MRI during performing enumeration tasks. Twenty-six right-handed healthy volunteers participated in this study. In an enumeration task, random dots from one to four were repeatedly displayed on a screen. Subjects were required to count events of stimulus presentation (counting condition) or enumerate the number of dots on the screen (subitizing condition) depending on instructions. We found that the prefrontal cortex (PFC), the dorsal premotor cortex (PMd) and the superior and inferior parietal lobe (PL) were mainly active during both subitizing and counting. Most of these regions overlapped between the two processes. However, different parts of the PFC were active during each process. These results suggest that a common parietofrontal network is involved in both subitizing and counting, and that the PFC plays a role for control of the two enumerative processes. [Jpn J Physiol 55 Suppl:S184 (2005)]

View full abstract

To investigate the neuronal mechanism for selection process of a target from an array of stimuli, we analyzed neuronal activity of lateral prefrontal cortex during the response period of a serial probe reproduction task. Monkeys were trained to memorize two sequentially presented objects, retrieve one target object from two memorized objects based on the color stimulus and then select that target object from an array of three objects presented during the response period. Of 611 recorded neurons, 92 showed visual response during the response period. Forty-five neurons showed array selectivity, and 20 showed both array and target selectivities. Most neurons with visual response were recorded from the ventrolateral prefrontal cortex (VLPFC). On the other hand, 78 neurons showed presaccadic activity. Of these, activities of 55 neurons were determined by the direction of saccadic eye movement. Neurons with presaccadic activity were recorded from both the dorsolateral prefrontal cortex (DLPFC) and the VLPFC. These results suggest that the VLPFC plays a role in selection process of a target object from an array of stimuli, and the DLPFC and VLPFC play a role in generation of saccadic movement. [Jpn J Physiol 55 Suppl:S184 (2005)]

View full abstract

In the primary visual cortex (V1), a neuronal response to the stimulation of the classical receptive field (CRF) is suppressively modulated by the stimulus concurrently or successively presented at the receptive field surround (SRF). In the present study, we addressed whether SRF effects are spatially additive and also whether they vary according to spatial configuration of stimuli placed in SRF in V1 neurons of anesthetized cats. Stationary flashes of sinusoidal gratings were used as stimuli. The CRF stimulus was a circular grating patch with optimal size, orientation, spatial frequency and phase. For SRF stimulus, we divided SRF into eight flanks (45deg step) and presented all eight flanks (all flanks) or oppositely-faced two flanks (2-flanks) or any one flank (1-flank). Even though the predominant effect of SRF stimulation on CRF response was suppression, a fast and transient facilitation of CRF response was also occasionally observed. In ten neurons so far analyzed, when the CRF and SRF stimuli were simultaneously presented, 2-flanks SRF stimulus induced suppression with a strength comparable to that of all flanks SRF stimulus suggesting that there is a localization of suppressive field in SRF as previously reported by Walker and colleagues (1999). In some neurons, co-linear configuration of CRF and SRF gratings induced stronger suppression than other configurations, and in other neurons, parallel configuration induced stronger effect. We will also show results of changing stimulus-onset-asynchrony of stimulus presentation. [Jpn J Physiol 55 Suppl:S184 (2005)]

View full abstract

Male SPORTS (Spontaneously Running Tokushima Shikoku) run voluntarily in a running wheel 6 times longer than male control Wistar rats. To test whether running habit is related to hippocampal catecholamine dynamics, we investigated the level of monoamines in the brain of SPORTS rats. Release of hippocampal norepinephrine (NE) was assessed with in vivo microdialysis, and concentration of NE and monoamine oxidase A (MAOA) expression were measured using tissue homogenate. The extracellular NE levels were higher whereas intracellular NE levels lower in the hippocampus of SPORTS rats compared to those of controls. The mRNA level of MAOA, a critical enzyme for the degradation of monoamines, in hippocampus was not different between SPORTS and control rats. However, the protein levels and activity were lower in the SPORTS strain without any mutation in the nucleotide sequences. Intraperitoneal administration of clorgyline (1 mg/kg BW/day), a specific MAOA inhibitor, to the control rats decreased MAOA activity in hippocampus and increased wheel running activity. Our results suggest that the decreased activity of MAOA and subsequent increase in the extracellular NE levels in the hippocampus are closely linked to the hyper-running phenotype of SPORTS rats. [Jpn J Physiol 55 Suppl:S184 (2005)]

View full abstract

Activity of striatal projection neurons represents reward expectation, and that dopamine neurons code reward expectation error and an incentive to work for reward, the basal ganglia have been supposed to be involved in adaptive reward-based action mechanisms. However, it remains to be revealed that how the tonically active neurons (TANs), participate in the adaptive reward-based action mechanisms. Thus, we studied the activity of TANs during learning of reward-based decision-making task. Monkey learned to depress a hold button after illumination of the button (start cue), and choose one of 3 target buttons by trial-and-error. If monkey chose a correct button, high-beep occurred and water was given. But low-beep indicate no reward (incorrect choices). The correct choice probabilities were 30% in first choice (N1), 50% at second choice (N2), around 90% at third choice (N3) and at repetition trials (R1). The monkey, first, learned 2 target task, then learned 3 target task. TANs responded to start cue and beep by suppression and/or facilitation of tonic discharges. Beep responses were similar in all trial types during the initial stage. But, through behavioral learning, responses became strong in N1 and N2 trials but very small in R1 trials. In contrast, start cue responses were stronger in N1 and R1 trials after learning. Thus, reward probability of decision strongly influenced activity of TANs, different from dopamine neurons. These results suggested that TANs modify their activity through behavioral learning of reward-based decision-making strategy. [Jpn J Physiol 55 Suppl:S185 (2005)]

View full abstract

The patterns of the multisynaptic inputs from the prefrontal areas to the primary motor cortex (MI) were studied by means of retrograde transsynaptic transport of rabies virus. Previous studies revealed that transsynaptic labeling of 1st-, 2nd-, and 3rd-order neurons with the virus occurs at 2, 3, and 4 days postinjection periods. In the present study, the virus was injected into the hindlimb, proximal forelimb, or distal forelimb representation of the MI of macaque monkeys, and, 4 days after the injection, the distribution of labeled neurons was examined in the prefrontal cortex. After the viral injection into the hindlimb representation, prefrontal labeling was observed mainly in the medial prefrontal cortex that is located on the medial wall of the hemisphere. After the injection into the proximal forelimb representation, a large number of neurons were labeled in the dorsolateral prefrontal cortex, mainly in its dorsal sector. After the injection into the distal forelimb representation, very dense labeling was observed in the ventral sector of the dorsolateral prefrontal cortex. The present results suggest that there may be a somatotopic organization in the prefrontal cortex. Functional implications for this organization will be discussed in terms of intracortical inputs to the prefrontal areas. [Jpn J Physiol 55 Suppl:S185 (2005)]

View full abstract

Background and purpose: Acupuncture has a longstanding use in traditional Chinese medicine including for rehabilitating of stroke patients. Its possible beneficial effects in acute stroke have as yet not been established. We therefore studied the effect of manual acupuncture and electroacupuncture in rat stroke model of a temporary and local ischemia. Methods: Infarction size was measured one week after the ischemia in four groups of rats; a control group receiving no treatment, a sham group, an electroacupuncture group and a manual acupuncture group. Results: The infarct area was similar in the control and sham groups whereas the area was 58% smaller in the electroacupuncture group and 57% smaller in the manual acupuncture group compared to the control group. Furthermore, electroacupuncture almost completely inhibited the cortical localisation of the infarction seen in the control and sham groups. Conclusion: The decreased infarction size in response to acutely administered acupuncture may be due to increased cerebral blood flow or to changes in neuroprotective growth factors induced by acupuncture treatment. It is unfortunate that acupuncture usually is administered days and weeks after the debut of the stroke symptoms and not at their beginning of the symptoms. [Jpn J Physiol 55 Suppl:S185 (2005)]

View full abstract

We have previously found that inspiration phase-locked alpha oscillation (I-α) during odor stimuli was found in the averaged potential triggered by inspiration onset in normal subjects (NS). EEG dipole tracing method (DT) of the scalp-skull-brain head model (SSB)(SSB/DT)identified the location of dipole from I-α in the entorhinal cortex (ENT), hippocampus(HI), amygdala, and centroposterior orbitofrontal gyrus (CP OFG) subserve odor threshold, and the rostomedial orbitofrontal gyrus (RM OFG) subserve odor recognition. It has been reported that impaired olfaction occurs in patients with Parkinson’s disease (PD). The present study was performed to determine whether the I-α and their dipole locations in PD are different from those observed in normal subjects. Recognition level of odor were lower than normal age matched subjects according to the T & T olfaction test (NS, 1.93 ± 0.28; PD, 3.88 ± 0.88; P<0.05). I-α consists of three positive waves (I-α1, I-α2, I-α3) in normal subjects, however, I-α2, I-α3 were less active in PD. SSB/DT identified the location of dipole in the ENT and HI of the I-α1 component, but dipoles were not estimated in the CP OFG and RM OFG. The OFC is connected with the perihinal and ENT areas and plays an important role in odor recognition memory in animals and humans. PD are capable to detect odor threshold level, but having difficulty in discrimination because of the connection between ENT and OFG may be affected by pathological changes. [Jpn J Physiol 55 Suppl:S185 (2005)]

View full abstract

'Blindsight' is a condition associated with damage to human primary visual cortex (V1), which causes phenomenal blindness while retaining some visually-guided behaviors. As an animal model of the blindsight, we investigated residual vision of macaque monkeys with unilateral lesion of V1 using saccade tasks. Two monkeys were preoperatively trained with various saccade tasks: (1) visually-guided saccade task, (2) visually-guided saccade task with a gap (∼100ms) introduced between the offset of fixation spot and the onset of saccadic target and (3) peripherally-cued attention task. Then, V1 of the monkeys was unilaterally removed. After some recovery period, visual capacity of the monkeys was examined using the saccade tasks descried above. In (1), the monkeys correctly made a saccade toward a target appeared in the affected hemifield, with increased detection threshold as compared to the intact hemifield. In (2), the gap reduced the saccadic reaction time, some of those within the range of express saccade (∼120ms). In (3), the monkeys' success rate was increased in the valid condition in which a precue is appeared in the same position as the upcoming saccade target, as compared to the invalid condition in which the precue appeared in the hemifield opposite to the target. These results suggest that the pathway that bypasses V1, possibly extrageniculate pathway, is responsible for the residual capacity of visually-guided saccade and for the gap effect. These results also suggest that the residual capacity of visually-guided saccade is influenced by spatial attention. [Jpn J Physiol 55 Suppl:S186 (2005)]

View full abstract

In the primary visual cortex (V1), a neuronal response to stimulation of the classical receptive field (CRF) is suppressively modulated by the stimulus presented at the receptive field surround (SRF), depending on the relationship among the parameters of stimuli at CRF and SRF. In this study, we tested the effect of stimulus size (Exp.1) and orientation-contrast between CRF and SRF stimuli (Exp.2) in V1 neurons of anesthetized cats, and analyzed temporal properties of the surround suppression. Stationary flash of sinusoidal grating was used as stimulus. In Exp.1, neurons were stimulated by a varying diameter of circular grating patch with optimal orientation and spatial frequency for CRF. A mean CRF size of analyzed 54 neurons was 5º, and 46 neurons were suppressed by more than 25% by stimuli larger than CRF. As an increment of the outer diameter of stimulus up to 20º, the suppression became stronger and also the latency for the maximal suppression was progressively reduced. These results suggest that neurons with large receptive field and fast conduction velocity contribute to the surround suppression. In Exp.2, CRF and SRF were stimulated with the optimal grating patch and the annulus with either iso- or cross-oriented to the CRF stimulus, respectively, and stimulus onset asynchrony (SOA) was changed from -120 to +120 ms. On average, the suppression was strongest at 0 ms of SOA regardless of the orientation-contrast. However, specificity to orientation-contrast, temporal tuning to SOA and magnitude of suppression varied widely from neuron to neuron. [Jpn J Physiol 55 Suppl:S186 (2005)]

View full abstract

Metacontrast is a visual illusion, in which visibility of a briefly presented stimulus (target) is reduced by a spatially adjacent and temporally following brief stimulus (mask). In our previous psychological study in human, the strength of metacontrast changed depending on the relationship of stimulus parameters between the two stimuli and the stimulus-dependency varied with timing of the mask presentation. The suppressive effects of metacontrast would be caused via interactions among visual pathways with different stimulus specificities and temporal properties. In the present study, we recorded V1 neurons of anesthetized cats to explore the neural mechanisms underlying metacontrast. Stationary flashes of sinusoidal grating were used as stimuli. Receptive field was stimulated with circular grating patch (target) and its surround was stimulated with annular grating (mask) with varying stimulus onset asynchrony (SOA)(-120–+120 msec). Orientation and contrast were identical between two stimuli, and spatial frequency (SF) of the mask was varied while that of the target was fixed at the optimal. Predominant effect of the mask was suppression of target responses when the mask was presented with SOAs between 0 and 120 msec. Time course and strength of the suppression were dependent on the relationship of SFs of two stimuli, and the mask with SF same as that of target exhibited the strongest and most prolonged suppression. These results suggest that suppressive response modulation by a stimulation of receptive field surround underlies the perceptual metacontrast. [Jpn J Physiol 55 Suppl:S186 (2005)]

View full abstract

We have demonstrated that perinatal six weeks exposure to Bisphenol A (BPA) impairs the sexual differentiation of brain and behaviors even if the dosage is below the tolerable daily intake level (TDI, 50μg/kg/day) (Kubo et al. 2003). In addition, we reported recently that a low dose of BPA during the last one week of prenatal period abolished the sex difference of the exploratory behavior and enhanced depressive behavior (Fujimoto et al. 2004). In this study, 0.1ppm of BPA was exposed to mother rats just after delivery until postnatal day 7 (PND7). We examined sexually dimorphic behaviors (exploratory behavior, locomotor activity) and emotional behaviors (anxiety, depression). In the open field test at 6 weeks of age, control females explored more frequently than males, this sex difference was also shown in BPA-treated rats. BPA exposure increased the time spent in open arms in the elevated plus maze test in female rats but sex difference (female>male) was also shown in both control and BPA-treated groups. In the forced swimming test, BPA exposure increased the immobility time in male rats and reduced the latency to induce immobility in both sexes. These findings suggest that a low dose of BPA during a neonatal period was less effective on sexual differentiation of exploratory behavior, but this chemical enhanced depressive behavior in a similar manner as the case of prenatal exposure. [Jpn J Physiol 55 Suppl:S186 (2005)]

View full abstract

Visual cognitive functions are under the influence of different physiological conditions as well as stress conditions. In this study we examined the effects of fasting-, sex hormone- and stress-related signals on the performance of visually-guided category discrimination tasks in rhesus monkeys, (Macaca mulatta). Task-related neuron activities were also investigated in the orbitofrontal cortex (OFC). Each trial of the task was started with a visual presentation of one of the following pictures. In food/non-food discrimination task, a picture of either food or non-food object was presented. In male/female task, a picture from one of the sexes of Japanese monkeys was presented. Simple figures and letters were also used as the control task. The visual performance was facilitated by fasting-induced endogenous substance, 2-buten-4-olide, but suppressed during menstrual period. Mechanical pain or restraint stress transiently suppress task performance with rapid recovery to original level or late facilitation of the responses. In contrast, social stress such as confrontation of rivals disturbed visual discrimination without adaptation. Neurons of the OFC mainly involved in discrimination of food/non-food and reward-related processing. The results suggest that visual discrimination of food or sex is under the influence of energy- and reproduction- and stress-related signals in different manner and OFC is the one of the possible candidate to integrate these information. [Jpn J Physiol 55 Suppl:S187 (2005)]

View full abstract