The organization of instrumental food-procuring movements in rats]

The roles of the lateral hypothalamus, basolateral nucleus of the amygdalar complex, the second field of the frontal cortex, and ventromedial thalamic nucleus in organization of the fast ballistic food-procuring movements were studied in albino rats. Sequences of uni- and bilateral destruction of the brain structures were assessed by photorecording. Movement-related neuronal activity in these structures was recorded in freely moving animals. A specific involvement of each of the above listed structures in organization of food-procuring movements was shown. The lateral hypothalamus seems to participate in initiation of the motor program and its efficient realization, the basolateral amygdala appears to produce activatory, training, and stabilizing effects. The second field of the motor cortex leads in movement acquisition (i.e., in memorizing) and decision making about triggering the program. The idea about the relay role of the thalamic motor nucleus is supplemented by understanding of its more complex integrative function.     

Role of frontal cortex in the organization of rapid ballistic movements of rats

We have studied the characteristics of rapid ballistic food-procuring movements in nonpedigree albino rats and have established that after ablation of the second area of the frontal cortex contralaterally to the preferred extremity the number of attempts increased, the duration of the movements decreased, and the phase structure of the movements was reorganized. After bilateral ablation of the cortex the animals completely lost their skill at procuring food. Our results indicate involvement of the frontal cortex in the development and achievement of the motor programs produced.N. I. Pirogov Medical Institute. Ukrainian Ministry of Public Health. Translated from Neirofiziologiya, Vol. 24, No. 2, pp. 186–192, February, 1992.     

Electrical activity of the lateral hypothalamus related to food-procuring movements of rats

On freely moving albino rats we demonstrated that, when fast food-procuring movements are performed, the mass electrical activity of the lateral hypothalamus (LH) is suppressed 1.6–2.0 sec before the movement beginning recorded with a photoelectrical device. Videorecording of the movements and recording of the spike activity of LH units showed that the latter are activated 1.0–0.1 sec before the movement initiation. The LH is considered a motivation-related structure, which serves as a source providing an increase in the excitability of the structures involved in the control of food-procuring movements and, further on, supporting this increased excitability. The LH is also a component of the mechanisms providing formation of the motor program. The role of the LH in the ensemble of motor centers, which organize and control voluntary movements, is discussed.     

Neuronal activity of the medial wall of the frontal cortex of the rat during performance of delayed reactions

Unit activity of the medial wall of the rat prefrontal cortex was studied during delayed response in the U-shaped maze. Prefrontal units were shown to be polysensory. Rhythmical stimulation induced habituation of unit responses. Spatio-selective neurones were found which means that medial part of the prefrontal area is involved in short-term memory. The role of the area is discussed in relation to the goal-directed behaviour.     

Neuronal organization of field 4 of the motor cortex of the cat brain

By means of the silver nitrate impregnation method after Golgi-Kopsch in kittens and young cats the field 4 in the cerebral motor cortex has been studied. The motor cortex of the field 4 possesses certain heteromorphism. Besides usual stellate and pyramidal neurons, that differ from real ones by some morphological signs: their body is often round, the apical dendrite is much thinner than the corresponding dendrite of a pyramidal neuron, it does not produce oblique branches along the course, never gets into the I layer, the spines arrange less densely. According to the mode of dendrites setting off, the atypical pyramidal neurons can be divided into multipolar and spindle-like with horizontal or vertical branching of the dendrites. According to the spines distribution, the multipolar atypical neurons can be divided into spinous, rare-spinous and aspinous. With respect to various cellular forms and distribution of various types of neurons in layers, every of the areas (gamma, alpha, sfu, fu) possesses specific peculiarities. The greatest variability of the neurons have the field 4 gamma and 4 alpha, where, besides stellate and pyramidal, atypical neurons can be found. The stellate neurons of the field 4 gamma are characterized with a deep arrangement, their number is essentially less, than in other areas of the field 4. In the field 4 alpha they are situated in the layers II-III. Suprafundal and fundal parts of the field do not possess pyramidal atypical neurons and are characterized with presence of large amount of the stellate neurons. In respect to the axonal branching in the suprafundal part of the field 4, 2 types of the stellate cells are distinguished.     

Neuronal correlates of metacognition in primate frontal cortex

Humans are metacognitive: they monitor and control their cognition. Our hypothesis was that neuronal correlates of metacognition reside in the same brain areas responsible for cognition, including frontal cortex. Recent work demonstrated that nonhuman primates are capable of metacognition, so we recorded from single neurons in the frontal eye field, dorsolateral prefrontal cortex, and supplementary eye field of monkeys (Macaca mulatta) that performed a metacognitive visual-oculomotor task. The animals made a decision and reported it with a saccade, but received no immediate reward or feedback. Instead, they had to monitor their decision and bet whether it was correct. Activity was correlated with decisions and bets in all three brain areas, but putative metacognitive activity that linked decisions to appropriate bets occurred exclusively in the SEF. Our results offer a survey of neuronal correlates of metacognition and implicate the SEF in linking cognitive functions over short periods of time.     

Functional organization of the medial frontal cortex

The anterior cingulate cortex (ACC) and adjacent areas of the medial frontal cortex (MFC) have been implicated in monitoring behaviour and in detecting errors. Recent evidence, however, suggests that the ACC not only registers the occurrence of errors but also represents other aspects of the reinforcement history that are crucial for guiding behaviour. Other studies raise the possibility that dorsal MFC areas not only monitor behaviour but also actually control response selection, particularly when the task in hand is changing. Many decisions are made in social contexts and their chances of success depend on what other individuals are doing. Evaluation of other individuals is therefore crucial for effective action selection, and some ACC regions are implicated in this process.     

Role of the amygdalar complex in programing of fast food-procuring movements in rats

Effects of uni- and bilateral electrolytic destruction of the basolateral nuclei of the amygdalar complex on the main parameters of fast food-procuring movements of albino rats were studied in the course of rearrangement of the motor programs; modifications of the parameters were observed both throughout the entire experiment and within each experimental day. The accuracy of the movements was significantly modified, which was manifested in an increase in the number of trials necessary for successful food capturing. An increase in the duration and a decrease in the frequency of the movements were also observed. The studied parameters underwent no complete recovery even on the tenth experimental day. Thus, the basolateral nuclei of the amygdalar complex occupy an important position in the system responsible for rearrangement of motivated automatized movements; when these nuclei are Injured, their function cannot be completely compensated by other brain structures.     

Fast ballistic food-procuring movements in rats: Phenomenology and probable controlling mechanisms

Parameters of fast ballistic food-procuring movements were studied in albino rats. With the use of video and photorecording, the number of attempts used by an animal, to get the food globula, duration of the movements, and their phasic structure were analyzed within the whole learning period and certain experimental days. When the motor skill had been formed, programed ballistic components characterized by hard-to-modify parameters and components with a considerable impact of reverse afferentation in their formation and performance were analyzed. The experimental data are interpreted in terms of the expediency of using the operant motor reactions performed by rats getting food from a narrow manger as a model of voluntary motor activity in electrophysiological, behavioral, neurochemical, and morphological studies. The regularities in formation of motor programs, initiation, realization, and control of the movements, and central mechanisms of these phenomena are discussed.     

Neuronal organization of the periamygdaloid cortex in the cat brain

Neuronal organization of the fields Pmm, Pml2, Pe and epm of the periamygdaloid cortex of the cat brain has been studied by means of Golgi and Nissl methods. The field Pmm essentially differs from other fields of this cortex by primitiveness of its cytoarchitectonic an neuronal organization (two layers uniform by the composition of their neurons are distinguished, the structure of the latter is relatively primitive). In the medial part of this field long axonal rarely branching short dendritic, and in the lateral part--poorly differentiating pyramidal and spindle-like cells predominate. The field Pmm can be considered as a transitional formation between the subcortex (the medial nucleus of the amygdaloid body) and other fields of the periamygdaloid cortex. The fields Pml2, Pe and epm are built more complexly: the cells are organized in 4 layers, more complexly differentiated by their form and size than in the field Pmm and correspondingly more various (long axonal densely branching cells are observed: pyramidal and spindle-like--of the cortical type and bushy--of the subcortical type, as well as long axonal rarely branching reticular cells). The short axonal cells in the fields Pml2, Pe and epm are rather variable in their form, size and direction of axons; in the field Pmm they are less numerous. The field Pmm and the complex of the fields Pml2, Pe and epm are perhaps different in their function, this is evident from different projection of their neurons. Axons of the cells in the field Pmm get into less differentiated and the most ancient medial nucleus of the amygdaloid body and into the ancient system of connections of the latter--terminal strip, and neurons of the fields Pml2, Pe and epm are projected into the basolateral part of the amygdaloid body and into the external capsule--phylogenetically younger structures. Besides, poverty of the axonal collateralies in the long axonal neurons and a small amount and uniformity of the forms of the short axonal cells in the field Pmm and contrary, rich collateralies and variety of short axonal cells in the composition of other fields demonstrate more complex internal integrative function, performing in that composition.     

Neuronal activity related to spontaneous and capsaicin-induced rhythmical jaw movements in the rat

Intraoral capsaicin induced rhythmical jaw movements (RJM) in anesthetized rats. Neurons in the trigeminal spinal nucleus caudalis or the cortico-peduncular (CP) axons were extracellularly recorded. Capsaicin excited dose-dependently most caudalis neurons, which were activated by stimulation of the oral cavity and/or the tooth pulp and activated during spontaneous or induced RJM. Ten of 55 CP axons were antidromically activated by stimulation of the contralateral trigeminal motor nucleus. All antidromic and 29 other CP axons discharged prior to the spontaneous RJM, but most of them did not during capsaicin-induced RJM. These neuronal activities possibly initiate spontaneous RJM although the activities of caudalis neurons are necessary for capsicin-induced RJM.     

Neuronal representations of reward-predicting cues and outcome history with movement in the frontal cortex

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Neuronal responses related to long-term recognition memory processes in prefrontal cortex

Much evidence indicates that prefrontal cortex plays an important role in long-term recognition memory processes. Here, we report primate prefrontal neuronal responses carrying information necessary for long-term visual recognition memory. The responses of many neurons signaled stimulus familiarity even when the period over which stimuli had to be remembered extended to 24 hr. Such responses occurred frequently in ventromedial, orbitofrontal, and anterior cingulate but not dorsolateral prefrontal cortex. Prefrontal information processing, as indicated by the response latencies, started after that in inferior temporal cortex and might be related to retrieval processes, as responses were typically larger for familiar than for novel stimuli.     

Neuronal correlates of motor performance and motor learning in the primary motor cortex of monkeys adapting to an external force field

The primary motor cortex (M1) is known to control motor performance. Recent findings have also implicated M1 in motor learning, as neurons in this area show learning-related plasticity. In the present study, we analyzed the neuronal activity recorded in M1 in a force field adaptation task. Our goal was to investigate the neuronal reorganization across behavioral epochs (before, during, and after adaptation). Here we report two main findings. First, memory cells were present in two classes. With respect to the changes of preferred direction (Pd), these two classes complemented each other after readaptation. Second, for the entire neuronal population, the shift of Pd matched the shift observed for muscles. These results provide a framework whereby the activity of distinct neuronal subpopulations combines to subserve both functions of motor performance and motor learning.