[Inhibitory reactions of the motor cortex neurons in the triggering of conditioned reflex organization in cats].

The neuronal impulse reactions of the motor cortex neurons (field 4) which are involved in the reflex realization were studied on the awakening cats trained to perform conditioned movement after the influence of two stimuli (the preliminary and the conditional). Slow cortex potential in vertex was registered simultaneously. It was established that before the response to the triggering signal (interstimuli period) high amplitude negative shift in the slow cortex potential is present.

Modulation of the spike activity of neocortex neurons during a conditioned reflex.

Experiments were conducted on cats to study the effects of iontophoretic application of glutamate and a number of modulators on the spike activity of neurons in the sensorimotor cortex during a conditioned reflex. These studies showed that glutamate, as well as exerting a direct influence on neuron spike activity, also had a delayed facilitatory action lasting 10-20 min after iontophoresis was finished. Adrenomimetics were found to have a double modulatory effect on intracortical glutamate connections: inhibitory and facilitatory effects were mediated by beta1 and beta2 adrenoceptors respectively.

[The modulation of the pulse activity of neocortical neurons during a conditioned reflex].

Spontaneous and evoked activity of neurons in the sensorimotor cortex was recorded in cats with learned conditioned placing reaction before, during, and after the iontophoretic application of synaptically active substances. It was shown that apart from direct excitatory effect on the cortical neurons during its application, glutamate (Glu) exerted some modulatory influence on unit activity in subsequent 20 min. Noradrenaline suppressed the background and evoked activity through beta 1 adrenoreceptors.

Interaction between dopamine and glutamate in the sensorimotor cortex during conditioned placing reaction.

Changes in impulse activity of sensorimotor cortex neurons associated with interaction of glutamate and dopamine during conditioned placing reaction were investigated in experiments on cats. Application of either glutamate or levodopa as a dopamine precursor increased background and evoked impulse activity in many of sensorimotor cortex neurons. It occurred occasionally that an increased impulse activity of cortical neurons produced by joint application of glutamate and levodopa could be much more intense than that produced by one of these substances.

[Variations of neuronal responses in cat cerebral cortex to somatic stimulation in the presence of additional stimulants].

Neuronal responses (areas 3, 4, 5) were registered in awake cats after electric stimulation of the contralateralis limb. External stimuli, food and defensive motivation inhibit short-latency neuronal reactions which were registered in control. When in the experiment there was electric stimulation of another limb instead of an external stimuli the neuronal reaction did not change.

[Inhibition of neuronal responses in the cat motor cortex, associated with attainment of a conditioned reflex when waiting for a flash of light].

Inhibition of neuronal spike reactions associated with reflex movements and induced by the light flare at different moments during the conditioned stimulation (1 s.) has been found in chronic experiments on cats. The light flare in the interval of maximum probability of the reflex realization has promoted a rise in the neuronal latency by 300-400 ms and a decrease of their duration almost twice.

[Inhibiting effect of the presentation of additional stimuli on neuronal responses in the cat sensorimotor cortex during a conditioned reflex].

Conditional responses of the sensomotor cortex neurons were registered in awake cats which were trained to respond to presentation of conditional stimuli (a single sound click) by instrumental conditional movement. Those neuronal responses were registered 50-150 ms before realization of reflex movements. During external stimulation after the reflex beginning, conditional neuronal reactions appeared 50-250 ms later, but the latencies of conditional movements did not change.

[Changes in neuronal responses of area 7 of the cat cerebral cortex to unconditional and conditional stimulation with additional stimuli].

Influence of external stimuli and food motivation on neuronal spike responses (area 7) induced by conditional and unconditional stimulation were studied in the awake cats. The beginning of external stimuli and food motivation inhibited neuronal responses after electro-cutaneous stimulation. During external stimulation after the reflex onset conditional neuronal reactions were later by 50-250 ms, but the latencies of conditional movements did not change.

[The inhibitory effect of the presentation of extraneous stimuli on the neuronal impulse reactions of the cat parietal cortex in a conditioned reflex].

Spike activity of neurons (area 7) was studied during conditioned placing reflex in the rest, during appearance and extinction of the orienting reaction in trained cats. Spike activity was studied also during unconditioned electro-cutaneous stimulation of the contralateral forelimb in untrained cats. Conditioned movements and electrocutaneous stimulation occurred without specific spike reactions of neurons due to the effect of the external stimulation on attention of animals.

[Neuronal reactions of the reticular nucleus and adjacent thalamus structures in the cat to natural stimulation in a chronic experiment].

Spike responses of 104 neurons of the nucleus reticularis thalami (R) and neighbouring thalamic nuclei to the acoustic stimuli, tactile and visual stimulation were studied in the chronic experiment. 29% of neurons responded to the acoustic stimulation and 11% of them were not specific to different acoustic stimuli. The minimal latency of the excitation to the acoustic stimulation was 12-37 ms and that of the inhibition--18-27 ms.

[Effect of food motivation on the impulse activity of neurons of the somatic cortex of the cat].

Spike reactions of the same somatic cortex neurons (areas 3 and 4) were analyzed during unconditioned stimulation. They were registered in the untrained hungry cats under conditions of rest and with food motivation. A decrease of the intensity of initial spike reactions, disappearance of the late neuronal responses following electro-cutaneous stimulation as well as changes in the level of the background activity were observed during emergence of food motivation.

[Effect of food motivation on the neuronal reaction of the somatic cortex in the cat during instrumental reflex].

Spike activity of neurons (areas 3, 4) was studied in cats during conditioned placing reaction before and after food satiation. After feeding the background activity increased in 2/3 of recorded neurons, tonic component of neuronal reaction decreased considerably and repeated contraction of m. biceps disappeared.

[Activity of neurons of the motor cortex of the cat during inhibition of a postural change conditioned reflex].

Spike reactions were recorded from motor cortex neurons in cats in the forelimb projection area during external and internal inhibition of the conditioned postural adjustment (transfer of the body weight) of the same limb. Spike responses evoked by external stimulation were of the same character as the responses during conditioned stimulation. As a rule, they were determined by the state of the animal and its habituation to the applied stimulus.

[Analysis of the spike activity of the neuronal population of the motor cortex in the cat during a postural change conditioned reflex].

In experiments on untrained and trained cats the impulse activity of cortical neurons (area 4) was studied in response to long (1s) acoustic stimulus (conditioned stimulus for trained animals) and to a fall of the platform under the studied limb (unconditioned stimulus). Only those neurons were studied which responded to the appearance of passive movement after the fall of the platform. In trained animals the number of neurons responding to conditioned stimuli in case of realization of the reflex was 100% and in the absence of conditioned movements--70%.

[Activity of motor cortex neurons in the cat during a conditioned postural change reflex].

Spike activity of unitary motor cortex (area 4) neurons was recorded during performance of conditioned reflex postural adjustment in cats. Changes in activity of most neurons (increase of discharge frequency) correlated with conditioned-reflex supporting movement of the forelimb. These neuronal reactions had specific polycomponent patterns and preceded the conditional movements by 50-600 ms.

[Reactions of the cat cortical field 7 during elaboration of a defensive conditioned reflex].

Neuronal activity of the parietal association cortex (field 7) was recorded in waking cats during and after defensive conditioning to sound. In 68% of neurons changes in impulse activity were observed with the appearance of first conditioned limb movements. The impulse responses of the neurons were stable only in the presence of conditioned limb movements; they disappeared during extinction of the reflex.

[Responses of neurons in the SI zone during a defensive conditioned reflex to sound].

Responses of single neurons in the primary projection zone of the somatosensory cortex to conditioned and electrocutaneous reinforcing stimuli were investigated in chronic experiments on cats with a preliminary developed sound conditioned defensive reflex. Five types of neuronal responses to reinforcing stimulus during application of combination were separated; such differentiation was impossible for neuronal responses appearing in the place of the absent reinforcing stimulus. A comparison of neuronal spike activity with the conditioned movement reaction revealed strict correlation between these processes.