Operant conditioning of short latency components evoked by electrical stimulation optic radiation fibers

Operant conditioning of trigeminal nuclear evoked potentials

The purpose of this study was to demonstrate operant conditioning of potentials in the rat's trigeminal complex evoked by stimulation of the primary descending trigeminal tract. The amplitude of the prominent component of the potential, with a peak at 10 to 22 msec after the stimulus, was conditioned. Reinforcement was electrical stimulation of the medial forebrain bundle. A bidirectional conditioning paradigm was used to control for noncontingent effects of the reinforcer. Eight of the thirteen animals demonstrated control of the evoked potential. Application of the neural conditioning paradigm to the investigation of loci of neuronal plasticity is discussed.

The rhythm of cortical excitability

Evidence has been gained which suggests that the spectral properties of the excitability cycle are other than those first proposed or assumed to exist in a number of experiments and theories. Instead of appearing as a sinusoidal cycle at the alpha frequency, the excitability cycle seems to be irregular and slower on the average than the EEG alpha rhythm. The rhythm appears to be continuously operative. It is not very sensitive in its spectral composition to the conditions of illumination or the level of behavioral activity. The rhythm operates synchronously in the right and left visual cortex. Methods similar to those described here could be used to map the extent to which synchrony is maintained in structures throughout the brain. They also suggest new approaches for psycho-physical studies which are aimed at establishing relationships between behavioral or perceptual phenomena and measures of neural activity.

Operant conditioning of vertical eye movements without visual feedback in the midpontine pretrigeminal cat

An operant conditioning of vertical eye movements was achieved in the midpontine pretrigeminal cat in total darkness by contingent reinforcement of spontaneous eye movements with lateral hypothalamic (LHT) reward stimulation, when each movement (upward direction was chosen in this experiment) exceeded a preset amplitude. However, the response rates in the dark were lower than those in the light and the time to reach the peak response rate was much longer. Recording of evoked potentials to optic chiasma (OC) stimulation revealed enhancement of late components of the visual cortex (VC) and superior colliculus (SC) responses in relation to eye movements. Sequential records of the averaged evoked responses associated with eye movements indicated that the amplitudes of the late components of the VC and SC waves gradually increased in the course of establishment of the operant conditioning, and decreased gradually during extinction. In a yoked control test, increase in amplitudes of the late components was much less significant during non-contingent reinforcement given independently of the eye movements. These results suggest that 'corollary discharge' may play a critical role as a cue in acquisition of the operant conditioning of vertical eye movements when visual feedback is absent in total darkness.