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.

The results of experiments on dogs with dysfunction of the dopaminoreactive system of the brain suggest the nonidenticality of its different divisions (cortical, striatal, mesencephalic) in the organization of situational conditioned reflexes. It was demonstrated that the nigrostriatal system is involved to a greater degree in the spatial analysis of signals, while the mesocortical system is more involved in the analysis of their biological significance. The dopaminoreactive system of the caudate nucleus is associated to a greater degree with the realization of cognitive, while that of the putamen is associated with the realization of motor programs of situational conditioned reflexes. The thesis of the necessity of the coordinated functioning of the DA-reactive systems for the organization of goal-directed behavior is substantiated.

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.

The organization of a behavioral act as a systemic process is always the result of an interaction between the cerebral cortex and many subcortical formations. Experiments carried out in our laboratory [8, 10, 16, 19, 22, 24] have demonstrated an important role for the striato-nigro-thalamic system in the structural-functional organization of behavioral acts. In particular, experiments have shown that anodic polarization of the sensorimotor and orbital cortex and thalamus temporarily switches off the functions of these structures, leading to a disturbance in conditioned reflexes and alteration in neuronal activity in the neostriatum [10, 16]. This is accompanied by a slowing of the process of forming a program of conditioned reflex behavior and encoding it via efferent pathways. Analogous results have been obtained in experiments with pharmacological blockade of outputs to the neostriatum from the substantia nigra, the medial center of the thalamus, and the ventral field of the tegmentum. In dogs subjected to these conditions, there is a disturbance in the formation of motor feeding and operant-defensive conditioned reflexes, and there is failure to produce previously developed programs of behavior linked with the analysis of environmental signals [4, 5, 23].Studies were carried out on the correlates of neuronal rearrangements in the caudate nucleus and parafascicular nuclei of the thalamus during the development of operant-defensive reflexes [15][16][17]. The spatial organization of many subcortical projections of the striopallidum have been determined, these involving interactions of the striato-nigro-thalamic structures during the formation of food and defensive reflexes of different levels of complexity; this is the classical model for the study of behavior in experimental conditions [8].Intensive studies are under way in a number of Russian and foreign laboratories on these questions of the structural-functional organization of behavioral acts [2, 6, 18, 26, 27, 29]. Despite numerous investigations of the subcortical mechanisms of behavior, particularly those aimed at elucidating the role in these processes of the neostriatum and its associated thalamic nuclei and the substantia nigra, many aspects of the interactions of these structures during the formation and execution of behavioral acts remain unclear. Thus, there has been insufficient study of the role of the neurochemical mechanisms of the neostriatum in the organization of conditioned feeding reflexes during free behavior. Additionally, the topical organization of dopamine-containing connections in the midbrain with the neostriatal nuclei in cats has not received full study. In dogs, these afferents have not been studied at all. The nature of the relationship between the spike activity of the caudate nucleus and the ventral anterior and ventrolateral nuclei of the thalamus during operant-defensive behavior remains unclear.The aim of the present work was to study these questions, which are linked to an understanding of the function of striato-nigro-tha...

This report describes studies of the interaction of the integrative dopaminergic and corticoliberin systems in the neostriatum during performance of situational food-related conditioned reflexes. Studies were performed in dogs with chemotrodes implanted in the substantia nigra and the head of the caudate nucleus. 6-Hydroxydopamine was injected into the substantia nigra at a dose of 50 microg, and 10 microg of corticoliberin was injected into the caudate nucleus. Blood cortisol and catecholamine levels were determined. Analysis of the result showed that an interaction takes place in the neostriatum between the corticoliberin and dopaminergic systems, and that in conditions in which dopaminergic structures are excluded, the efficacy of corticoliberin in the performance of behavioral acts decreases by 30-40%, i.e., complete expression of its regulatory role of motor situational conditioned reflexes is lost.