Sensory Transmission in Visual Pathway in Various Arousal States of Cat
1962 年 78 巻 1 号 p. 76-96
詳細
1962 年 78 巻 1 号 p. 76-96
Transmission of sensory messages under reticular activation was investigated at the three levels of the visual pathway in locally anesthetized cats, immobilized with Flaxedil, using as indicators unitary and mass responses to localized visual stimuli. The degree of alertness was judged by the EEG recorded from the visual cortex and pupillary size of one intact eye. Non-visual sensory stimuli or electrical stimuli applied to the mesencephalic reticular formation served as alerting stimuli.
1. Radiation units were identified by the shape of spikes and discharge pattern as well as the latency of response to electrical stimulation of the optic tract or optic radiation and refractory period. These units were classified into “on” and “off” type units in the dark-adapted state. They showed the background discharge of 10-20/sec in the non-alerted state and increased their discharge rate in the alerted state. A response increase in discharge rate fluctuated remarkably in a series of trials with constant stimuli in the non-alerted state, but the fluctuation decreased definitely in the alerted state.
2. The photically evoked potential in the lateral geniculate which varied in the shape and amplitude in the non-alerted state showed a reduction of fluctuation in the alerted state.
3. In optic tract units no such difference as observed in the radiation units could be found between the non-alerted and alerted states.
4. Most visual cortical neurons were facilitated by reticular activation to respond intensively and regularly to repeated presentation of visual stimuli. Inhibition also was observed in one unit.
5. The photically evoked potential in the visual area was more stable in the shape and amplitude under the alerted than non-alerted conditions.
6. From the results described above it was concluded that the effect of reticular activation is to increase the regularity of response above the lateral geniculate level. In other words, the reliability of information is increased under reticular activation.
