Operant controlled neural event: functional independence in behavioral coding by early and late components of visual cortical evoked response in cats

In vitro analog of operant conditioning in aplysia. II. Modifications of the functional dynamics of an identified neuron contribute to motor pattern selection

Previously, an analog of operant conditioning was developed using the buccal ganglia of Aplysia, the probabilistic occurrences of a specific motor pattern (i.e., pattern I), a contingent reinforcement (i.e., stimulation of the esophageal nerve), and monotonic stimulation of a peripheral nerve (i.e., n.2,3). This analog expressed a key feature of operant conditioning (i.e., selective enhancement of the probability of occurrence of a designated motor pattern by contingent reinforcement). In addition, the training induced changes in the dynamical properties of neuron B51, an element of the buccal central pattern generator. To gain insights into the neuronal mechanisms that mediate features of operant conditioning, the present study identified a neuronal element that was critically involved in the selective enhancement of pattern I. We found that bursting activity in cell B51 contributed significantly to the expression of pattern I and that changes in the dynamical properties of this cell were associated with the selective enhancement of pattern I. These changes could be induced by an explicit association of reinforcement with random depolarization of B51. No stimulation of n.2,3 was required. These results indicate that the selection of a designated motor pattern by contingent reinforcement and the underlying neuronal plasticity resulted from the association of reinforcement with a component of central neuronal activity that contributes to a specific motor pattern. The sensory stimulus that allows for occurrences of different motor acts may not be critical for induction of plasticity that mediates the selection of a motor output by contingent reinforcement in operant conditioning.

State dependent activity in monkey visual cortex. I. Single cell activity in V1 and V4 on visual tasks

This study examined the extent to which the responses of single cells in the striate cortex (V1) and the extrastriate cortex (V4) of the alert rhesus monkey are modulated by visual stimuli whose relevance in a behavioral task is varied. The animal had to detect the repetition of a visual pattern (i.e. detect similarity), preceded by a randomized number of alternations between two different patterns. The responses produced by the last, reward contingent stimulus were compared with responses obtained to that same stimulus earlier in the sequence. Modulatory effects in V1 were moderate: 31% of the cells (63 of 200) showed response increments of 20% or more to the last, reward contingent stimulus. In V4 the effects were much more pronounced: 72% of the cells (110 of 154) showed modulatory effects of more than 20%. In V4 but not in V1 orientation tuning curves showed a significant narrowing as well as a peak response increment to the behaviorally salient stimulus, suggesting a feature specific mechanism associated with the detection of similarity. Although a response decrement was observed in many cells during the repeated alternations, this effect was significantly smaller than the modulation produced by the detection of similarity. Controls included the presentation of novel stimuli during the presentation sequence which did not produce an enhanced response. It is hypothesized that the feature specific effects reported here are produced by higher order feedback systems.

Operant conditioning of the short-latency cervical somatosensory evoked potential in quadriplegics

Operant conditioning of short-latency cervical somatosensory evoked potentials (CSEP) was demonstrated in five cervical cord injury subjects. Subjects were conditioned to augment the N14 potential, thought to originate from the dorsal column nucleus. Increased N14 potential was associated with an increase in N19 and P22 potentials, and either a decrease (base) or no change (train) in the brachial plexus potential. The N19 potential was correlated with significant reductions in the sensation-twitch (S/T) ratio during conditioning sessions, indexing improved sensation to low-intensity percutaneous stimulation. Moreover, S/T ratios decreased significantly during conditioning sessions, and were reduced significantly relative to initial baseline values. The results do not appear to be associated with trivial mediating influences.

Simple spike activity of Purkinje cells in the posterior vermis of awake cats during spontaneous saccadic eye movements

Extracellular recordings were made from 151 cerebellar cortical cells in the posterior vermis of 12 awake cats. Thirty-two percent (n = 48) of these cells modulated their activity with respect to the onset of spontaneous saccadic eye movements. Thirty-five cells in this group were positively identified as Purkinje cells and manifested changes in simple spike activity that were related to saccade onset. These included short excitatory, inhibitory, or biphasic changes that were superimposed on background tonic firing rates (avg. = 54 spikes/sec). Such changes were recorded before as well as after the onset of a saccade. Sixty-five percent (n = 22) of these cells were related to horizontal and vertical saccades in more than one direction of motion. These cells were randomly distributed throughout the posterior vermis and manifested no anatomical topographic organization with respect to the direction of saccadic eye movement. The results of this study suggest that lobules VI and VII of the cerebellar vermis participate in both the initiation and execution of spontaneous saccades in preferred directions.

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.

Evolution of average evoked potentials in cats during conditioning before and after tegmental lesions

Sensory-specific and modality nonspecific average evoked potentials (AEPs) were recorded from the cortical areas and subcortical structures in two groups of cats: (1) normal cats which after conditioning were subjected to brainstem lesions and reconditioning; (2) cats with brainstem lesions and subsequent conditioning. A new waveshape of the visually evoked potenials developed in the visual cortex in the course of conditioning to light flashes (LF) in both groups of cats. In normal cats, a new component, with a peak latency from 80-100 msec and with reversed polarity, was observed in place of the late, longlasting, component of the preconditioning AEP. The latency of the new component is longer in cats with brainstem lesions. The first signs of waveform modification occurred relatively early in the process of learning, well before the animal learned to react consistently to the conditioned stimulus. Also, there seemed to be no clear relationship between the modified waveshapes of the AEPs and performance level during a particular session of conditioning. The modifications did not depend on habituation to the long-lasting exposure to light flashes presented alone. The new waveshape was preserved to a variable degree after brainstem lesions, that is, reconditioning never started with a potential characteristic for a naive animal. AEPs to licks in the auditory cortex, also changed during conditioning, although this modification was not so evident as in visual responses. In contrast to evident modifications of evoked responses in sensory specific structures during the process of conditiong, there were very small if any, changes in modality nonspecific structures, including brainstem reticular formation. Modality nonspecific responses were obtained from the brainstem reticular formation and motor cortex to light flashes and clicks, from the visual cortex to auditory stimuli and from the auditory cortex to light flashes. Only poorly developed evoked responses could be detected in the motor-sensory cortex during conditioning to light flashes although rhythmic EEG activity related to presentation of the conditioned stimulus (CS) was observed from this arena - thus indicating that they were not the same phenomena.

Operant-controlled evoked responses: discrimination of conditioned and normally occurring components

Rats were rewarded for signaling large and small sensory evoked components with appropriate bar presses. Most rats operantly generated large components and correctly signaled only these. Two rats correctly signaled successful and unsuccessful attempts to generate large waves. One rat discriminated component amplitudes without operantly attempting to generate specific wave types.

Operant conditioning of specific patterns of neural and muscular activity

In awake monkeys we recorded activity of single "motor" cortex cells, four contralateral arm muscles, and elbow position, while operantly reinforcing several patterns of motor activity. With the monkey's arm held semiprone in a cast hinged at the elbow, we reinforced active elbow movements and tested cell responses to passive elbow movements. With the cast immobilized we reinforced isometric contraction of each of the four muscles in isolation, and bursts of cortical cell activity with and without simultaneous suppression of muscle activity. Correlations between a precentral cell and specific arm muscles consistently appeared under several behavioral conditions, but could be dissociated by reinforcing cell activity and muscle suppression.