In the present study, a novel procedure of non-matching-to-place (NMTP) task in the radial maze was devised and the effects of lesions of the entorhinal cortex and hippocampus on spatially guided working/reference memory were investigated. Both groups of rats with the entorhinal and hippocampal lesions showed severe impairment of performance on the NMTP task at delay of 0 min, whereas sham lesioned rats rapidly reacquired the task. Overtraining of the NMTP task before lesion considerably ameliorated behavioral performance of rats with the entorhinal cortex lesion, although hippocampal lesioned rats showed no improvement of performance. When various delay intervals (0, 1, 3, and 9 min) were randomly interposed between the information run and the choice run in the delayed NMTP test, delay-dependent impairments were shown in the entorhinal lesioned rats which reacquired postoperative NMTP task. These results indicate the possibility of differential effects of overtraining on the entorhinal cortex and hippocampus, in that the entorhinal-hippocampal system is initially involved in both spatially guided working and reference memory, and after overtraining, reference memory as well as spatially guided working memory is left on the function of the hippocampus, but the entorhinal cortex becomes to play a critical role of spatially guided working memory.

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The present study examined pigeons' discrimination and categorization of paintings using a liquid crystal display (LCD) and a cathode ray tube (CRT). First, pigeons learned to discriminate 40 paintings by Monet and Picasso. Each painting was presented successively for 30-s separated by a 5-s blackout period. Responses to S+ were reinforced according to a variable-interval (VI) 15-s schedule, whereas responses to S- were not reinforced. After pigeons successfully discriminated the paintings, novel stimuli including paintings by Monet, Picasso, Cezanne, Renoir, Matisse, and Delacroix were presented under extinction. The results from discrimination training and generalization tests showed that pigeons' categorization performance was better with LCD than with CRT. The results indicate that LCD is more suitable for behavioral experiments than CRT.

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Rats have been reported to choose B among BD pair after being trained with four pairs of olfactory discrimination in a five-item series (A+B-, B+C-, C+D-, D+E-). The present research examined rats in a similar transitive inference task with visual stimuli. Rats trained in the Upward order (D+E-, C+D…: group Upward) demonstrated transitive responding, but rats trained in the Downward order (i. e., A+B-, then B+C-…: group Downward) did not. However, after retraining of the four original pairs of stimuli, both groups showed transitive responding. These results suggest that the ability to solve transitive inference tasks is not limited to the olfactory sensory domain in rats.

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A new device and a surgical procedure for placing electrodes in goldfish are described. They are used in stereotaxic surgery that is performed in lesion and electrophysiology studies. We modified DKI's stereotaxic apparatus in which the subject is fixed on a mouthpiece and two rubber plates in order to produce highly localized lesions in fish. A body holder and a new method of administering anesthesia were also developed. By stabilizing the water flow into the subject's gill using a three-pronged pump, we were able to maintain the anesthetic effect.

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The neural base of the bat's biosonar system is discussed here. The bat emits complex biosonar sounds (pulses) and listens to echoes for orientation and hunting flying insects. Different types of biosonar information are carried by different parameters characterizing pulse-echo pairs. For example, distance information is conveyed by echo delay, while velocity information is carried by Doppler shift. In the auditory cortex of the bat, not only frequency but also other information baring parameters such as echo delay and Doppler shift are systematically mapped as subareas. These computational maps greatly depend on subcortical signal processing. The subcortical auditory nuclei create delay lines and multipliers (or AND gates) for processing distance (echo delay) information, and also create level-tolerant frequency tuning and multipliers (or AND gates) for processing velocity (Doppler shift) information. These multipliers are called FM-FM and CF/CF combination sensitive neurons, respectively. The neurophysiological investigations of the bat's biosonar system provide an excellent database for neural computational models and sonar systems. Application of an agonist of inhibitory neurotransmitter to DSCF or FM-FM area behaviorally revealed the functions of these auditory subareas. Findings made by an on-board telemetry microphone from flying bats confirmed Doppler-shift compensation.

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