In this study the results of behavioral, neurophysiological, and morphological investigations in relation to the participation of the corticostriatonigral system in the organization of conditioned reflexes are presented. It was demonstrated in experiments on dogs that blockade of N-methyl-D-aspartate receptors of the caudate nucleus disrupts the realization of consolidated conditioned reflexes and renders their development more difficult. The blockade of quisqualate receptors facilitates the process of differentiation. Switching off of the dopaminergic input makes the development of positive conditioned reflexes more difficult. The reversible switching off of the substantia nigra leads to the reorganization of the neuronal activity of the caudate nucleus in response to the presentation of the conditional signal. Inhibitory nigral influences are directed primarily to the ventromedial divisions of the nucleus, while activating influences are directed to its dorsal segments. The topically organized connections of the motor regions of the cortex with the dorsal region of the caudate nucleus, and of the limbic regions with its ventromedial divisions were studied in morphological investigations on cats. A certain distinctiveness was identified of the spatial organization of the nigrostriatal projections. The data obtained are discussed from the point of view from the systemic organization of behavior.
A comparative investigation has been carried out for the first time of the receptor binding of glutamate with synaptic membranes and coarse fractions of the postsynaptic enlargements isolated from the striatum of rats differing in their capacity to develop an alimentary instrumental reflex. It was demonstrated that the number of that glutamate binding sites on the postsynaptic enlargements isolated from the striatum of rats capable of rapidly developing an alimentary instrumental reflex was increased as compared with animals not subjected to training. This relationship is maintained two months after the termination of training.
This article presents the results of three series of experiments on cats, dogs, and lower primates, performed to investigate the structural, neurophysiological, and mediator mechanisms of the corticostriatal systems involved in the organization of behavior. Morphological studies of corticostriatal connections showed that along with the diffuse distribution of afferent terminals within the striatum, there were also elements of topical organization defined by anteroposterior and mediolateral gradients. Neurophysiological experiments on dogs and lower primates were used to study the spike activity of the prefrontal region of the cortex and the head of the caudate nucleus during training to conditioned first- and second-order reflexes and during the solution of complex problems involving delayed spatial selection. Studies demonstrated that while in dogs, most of the neurons recorded showed a transition to responses to the conditioned signal at a particular stage of carrying out a conditioned response, in monkeys all cells recorded showed specific responses at different periods of solving the task at all stages of the study. Neuropharmacological experiments on dogs showed that agents blocking glutamine receptors in the caudate nucleus had more pronounced effects at the phase of developing conditioned movement reflexes. Administration of these agents during the reflex reinforcement phase affected only the differentiation of inhibition. These results lead to the conclusion that the prefrontal area of the cortex and, to some extent, the caudate nuclei, act on incoming information specifying the current dominant need and the states of the external and internal environments, to carry out programmed actions and assess the results of these actions.
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