Formation of cognitive structures in conditioned-reflex behavior in monkeys: Relationship with type of visual information.

The characteristics of learning processes and long-term memory (LTM) were studied in rhesus macaques discriminating visual stimuli (geometrical figures of different shapes, sizes, and orientations, and with different spatial relationships between image components). Trained monkeys were tested for the ability to perform invariant recognition after stimulus transformation, i.e.

[Forming of the visual cognitive structures in the monkey conditioned-reflex behaviour: the dependence on the sensory information].

In monkeys, changes in size and shape of figures led to a significant decrease of correct solutions in training and a considerable increase of refusals from solution of tasks as well as the time of their motor response. The invariance of differentiation in this case was achieved after additional training. The data obtained show that, based on the stimulus sensory processing in conditioned-reflex training, in the long-term memory some differentiating signs are formed: the cognitive structures (the functional neurophysiological mechanisms) maintaining the classification of visual images.

Disorders of learning and memory processes in a monkey model of Alzheimer's disease: the role of the associative area of the cerebral cortex.

The processes of learning and storage of the results of learning were studied in a model of Alzheimer's disease in two groups of rhesus macaques (three individuals in each group). Studies were performed after injection of neurotoxins (group I) and physiological saline (group II, controls). Two months after injections (stage C1), learning parameters were studied in monkeys of both groups using a new stimulus discrimination test (filled geometrical figures versus outline figures).

[Disorders in learning and memory processes in the monkey model of Alzheimer's disease: the role of the cerebral cortex associative areas].

Processes of novelty learning and keeping the results in Alzheimer's disease in two groups of rhesus-monkeys (three monkeys in each group), were studied: following neurotoxins administrati- on (I group) and saline administration (II group). In two months after the injections (the C1 stage), considerable differences between the groups were revealed in the task of differentiation among contour shapes. For the I group monkeys the learning was difficult: the correct decision making did not reach 85 %, and the probability of refusing to make a decision increased.

Interaction of sensory and cognitive processes during visual recognition: the role of the associative areas of the cerebral cortex.

The first part of the present study used a model of Alzheimer's disease in two groups of animals (three monkeys in each), given injections of neurotoxins (monkeys of group I) and physiological saline (monkeys of group II). Before injections, all monkeys were trained to discriminate stimuli containing different types of information (spatial frequency grids and geometrical figures of different colors and with different spatial relationships between objects) and to perform spatial selection. The dynamics of impairments in the characteristics of working memory were identified using delayed differentiation tasks in monkeys of both groups before injections and every two months after injections.

Functional characteristics of the associative areas of the cortex involved in visual information discrimination learning processes in monkeys.

Experiments on three groups of rhesus macaques (intact and with bilateral removal of field 7 and the sulcus principalis) were performed to study the functional characteristics of the associative areas of the cortex while the monkeys learned visual discrimination. Significant differences in learning processes associated with removal of structures and the properties of the stimuli were seen in all animals, in the form of different types of learning curves. As compared with intact monkeys, removal of field 7 had no effect on learning processes for images with properties such as spatial frequency, color, and animal images, though there was a significant worsening in the characteristics of learning during visual discrimination of spatial relationships between objects.

[Interaction between sensory and cognitive processes in visual recognition: the role of the associative areas of the cerebral cortex].

Monkeys were taught to differentiate stimuli with different types of information and to perform a spatial choice. Development of Alzheimer's disease in experimental monkeys entailed a deficit of operative memory, a considerable enhancement of entropy related to correct decisions. In control monkeys, no significant changes of these characteristics occurred.

[Disorders of cognitive processes in simulation of Alzheimer's disease in monkeys].

Two groups of monkeys were learned to differentiate stimuli with different types of information and to make a spatial choice. Characteristics of the operative memory were revealed in the delayed differentiation tasks prior to and after administration of p75-saporin (I group) and saline (II group). For the first time the Alzheimer disease in monkeys was shown to entail a deficit of operative memory due to disorders in the sensory and cognitive components of the memory.

Organization of working memory processes in monkeys: the effects of a dopamine receptor agonist.

The effects of the dopamine receptor agonist agroclavin on cognitive processes associated with mechanisms of visual recognition and long-term and working (short-term) memory were studied in delayed visual differentiation and delayed spatial selection tasks in monkeys (rhesus macaques). Measurements made before and after p.o.

[Functional specifics of cortical associative regions participating in learning to differentiate visual information in monkeys].

In 3 groups of monkeys: intact, those with their 7th field bilaterally removed, and those with bilateral removal of the sulcus principalis, functional specifics of the cortex' associative areas were studied. Removal of the 7th field practically does not affect processes of training for images with such features as spatial frequency, colour, and images of animals, but considerably impairs the learning characteristics in visual differentiation of objects' size and spatial interrelationships among objects. Removal of the sulcus principalis considerably impairs the characteristics of differentiation of objects' size and spatial interrelationships among them, as well as differently coloured stimuli.

[Effect of a dopamine agonist on working memory in monkeys].

Prior to and after pharmacological effect of Agroclavine (a dopamine receptors' agonist) following its per os administration, its optimal dose (5 mg/kg) for cognitive processes was established in monkeys. Psychotropic effect of Agroclavine resulting in cognitive dysfunction manifested itself to a greater of lesser extent in all the experimental animals. Correctness of visual differentiation, probability of refusal to solve a task, time of a correct motor response were assumed as the behavioural criteria.

Neurophysiological correlates of delayed visual differentiation tasks in monkeys: the effects of the site of intracortical blockade of NMDA receptors.

A delayed visual differentiation task using stimuli of different colors was used in rhesus macaques to study the characteristics of visual recognition, short-term memory, and the responses of neurons recorded simultaneously in the visual and prefrontal areas of the cortex, along with their relationships with the site of intracortical (fields 17 or 46) perfusion of the glutamate receptor antagonist 2-amino-5-phosphonovaleric acid (APV). The behavioral characteristics and spike activity of individual cells in cortical fields 17 and 46 were recorded before and after perfusion with APV and after washing away of traces of APV. Multifactor dispersion analysis showed that the effect of APV in monkeys consisted of decreases in the probability of correct responses, leading to a decrease (two-fold) in the duration of short-term storage of information and a significant increase in the motor reaction time.

The effects of an NDMA receptor antagonist on delayed visual differentiation in monkeys and rearrangements of neuron spike activity in the visual and prefrontal areas of the cortex.

The effects of perfusion of field 17 with the glutamate receptor antagonist 2-amino-5-phosphonovaleric acid (APV) on the characteristics of visual recognition and short-term memory were studied, along with the effects of APV on the responses of neurons in the visual and prefrontal areas of the cortex in rhesus macaques. In the test for delayed visual differentiation of stimuli of different colors, behavioral data were recorded simultaneously with multichannel recordings of the spike activity of single cells in cortical field 17 (directly within the microdialysis zone) and field 8. Multifactor dispersion analysis (ANOVA) showed that APV significantly worsened the behavioral characteristics in monkeys, with significant reductions in the duration of short-term storage of information (by factors of 2-4) and significant increases in the motor response times.

[The role of the prefrontal and parietal cortex in learning and memory in monkeys].

Removal of the 7th field of parietal cortex and sulcus principalis of prefrontal cortex did not affect learning processes for images with such properties as spatial frequency, orientation, geometrical form, but worsen learning characteristics in visual differentiation of spatial information making the learning processes unstable, longer and below the 85% level. Removal of sulcus principalis also affects learning of differentiation among various colour stimuli. The short-term memory in these monkeys are also much worse than in intact animals.

[Neurophysiological correlates of delayed visual differentiation in monkeys: effect of location of the NMDA-receptor intracortical blockade].

A multi-factor variance analysis revealed that the 2-amino-5-phosphonovalerian acid (APV) effect was manifested in monkeys by a decrease in the number of correct responses entailing a two-fold shortening of the short-term information storage, as well as by an augmentation of the motor responses' time. The correct responses' probability depended on the APV diffusion localisation in the cortex whereas the motor responses' time did not depend on it. The APV effect was accompanied by a desynchronisation of the unit activity in fields 46 and 17.

[Effect of the NMDA receptor antagonist on parameters of delayed visual differentiation and rearrangement of the impulse activity of neurons in visual and prefrontal cortices in monkeys].

With the aid of a multichannel leads the unit activity was recorded in the 17th and 8th cortical fields along with registering behavioural data in Rhesus monkeys. Multi-factor variance analysis revealed that the 2-amino-5-phospho-valeric acid (APV) effect involved a significant worsening of the monkeys' behavioural characteristics: duration of the short-term memory shortened (2-4-fold), motor reactions' time increased, and the changes of cognitive characteristics were always followed by significant rearrangements of the unit activity in the above areas. The data obtained suggest that these cognitive dysfunctions are due to a desynchronisation of unit activity in different areas of the cortex including the neuronal assemblies maintaining the short-term memory mechanisms associated with the glutamatergic structures.

Short-term memory processes in delayed visual differentiation in rhesus macaques after bilateral removal of field 7 of the parietal cortex.

Monkeys (Macaca mulatta) with preliminary removal of field 7 of the lower parietal cortex and previously trained to differentiate images differing in shape, color, size, orientation, and spatial relationships were used to study the processes involved in short-term storage of different types of information required for a delayed (by 0-8 sec) visual differentiation task and the effects on these processes of the antioxidant Oxymetacil. Significant differences were found in comparison with intact animals. Removal of field 7 sharply worsened short-term storage processes during visual differentiation of different types of images, including those differing in terms of properties such as color, geometrical shape, and the spatial relationships between image elements.

Relationship between learning characteristics and the properties of visual objects in rhesus macaques with bilateral removal of parietal cortex field 7.

Behavioral experiments were used in rhesus macaques with bilateral excision of field 7 of the lower parietal cortex to study the relationship between visual differentiation learning processes and a variety of stimulus properties. All animals showed significant differences associated with stimulus properties, which produced different types of learning curves. For each monkey, visual stimuli were divided into compact groups in terms of the "similarity" of their learning characteristics.

Specific characteristics of cholinergic mechanisms of short-term memory in monkeys for different types of visual information: the effects of amizil.

Experiments on rhesus macaques were used to study the relationship between the characteristics of delayed visual differentiation and stimulus properties in conditions of pharmacological treatment with the m-cholinoreceptor blocker amizil, with the aim of identifying how modification of cholinergic structures affects different types of information. Disturbances to short-term memory for all stimuli consisted of reductions in the duration of retention and increases in motor reaction times, but occurred at different doses of the blocker: amizil at a dose of 0.3 mg/kg significantly decreased the retention duration for information relating to spatial relationships.

Relationship between the characteristics of visual short-term memory in monkeys and the spatial properties of images.

Experiments were performed on Rhesus macaques to study the relationship between delayed visual differentiation processes and stimulus properties. These investigations showed that the processes of short-term storage of visual information in monkeys has significant features associated with differences in stimulus properties. These consisted of different durations of storage and motor response times.

[Short-term memory processes during delayed visual differentiation after bilateral removal of the 7th field of the parietal cortex in Rhesus macaca].

Extirpation of the parietal cortex area 7 aggravated delayed visual discrimination of all visual attributes including shape, colour and spatial relationship in adult rhesus monkeys. Oxymetacil improved the shape and colour discrimination alone.

[Dependence of learning characteristics on visual object properties in Rhesus macaca by bilateral removal of the 7th field of the parietal cortex].

Removal of the rhesus monkey parietal cortex 7th field exerted no effect on learning processes involving visual discrimination of images united in their colour and geometrical form, but the learning of differentiating the spatial information did suffer. The data obtained suggests that, in the process of learning visual differentiation, spatial differentiating signs are formed, the process involving neuronal structures of the 7th field of the inferior cortex. Removal of the 7th field disrupts mechanisms of the body scheme assession and egocentric orientation resulting from visual-vestibular interrelationships.