Effect of stimulation of the medial geniculate body on the motor polarization dominant in rabbits

Studies were carried out on the effects of stimulation of the medial geniculate body on the course and recovery of a cortical motor polarization dominant created in the sensorimotor cortex of the right hemisphere in rabbits. Stimulation of the medial geniculate body, on a background of an optimum dominant, elicited a movement response of the “dominant” limb. Spectral-coherent analysis of the electrical activity of the sensorimotor cortex and medial geniculate body showed that stimulation produced changes characteristic of the dominant state in the power spectra of the total activity of these structures of the right “dominant” half of the brain, as well as in the coherence spectra. Insitute of Higher Nervous Activity and Neurophysiology, Russian Academy of Sciences, Moscow. Translated from Zhurnal Vysshei Nervnoi Deyatel'nosti, Vol. 46, No. 1, pp. 100–107, January–February, 1996.     

Postnatal Development of Conditioned Reflex Behavior: Comparison of the Times of Maturation of Plastic Processes in the Rat Hippocampus

The formation of conditioned reflex fear, escape responses, and conditioned avoidance responses during acquisition of a conditioned two-way avoidance reflex was studied in rats of different ages. Rats aged 16–17 days acquired the conditioned reflex but not the escape reaction or the conditioned avoidance response; acquisition efficiency was higher than in adult rats. Escape responses appeared from postnatal day 18. The ability to acquire this type of learning was complete by age 3–4 weeks. Maturation of the mechanisms of the “classical” (the fear phase) and operant (transfer to another sector in response to the unconditioned stimulus) components did not facilitate acquisition of the conditioned two-way avoidance reflex until the middle of postnatal week 4. Learning efficiency in four-week-old rats was lower than in adults. It is suggested that the maturation of different types of memory may be associated with the periods at which plastic processes develop in the hippocampus. __________ Translated from Zhurnal Vysshei Nervnoi Deyatel'nosti imeni I. P. Pavlova, Vol. 54, No. 5, pp. 666–672, September–October, 2004.     

Effects of microinjection of scopolamine into the neostriatum of rats on performance of a food conditioned reflex at different levels of fixation

Chronic experiments performed on 32 Sprague-Dawley rats using a movement-feeding operant reflex (Skinner box) model showed that microinjection of scopolamine into the neostriatum had effects on this reflex which depended on the stage of learning. In animals with weakly fixed reflexes (prior to reaching the stage of memory consolidation), bilateral microinjection of 0.3 μg of scopolamine into the caudate nucleus completely inhibited the reflex for a prolonged period of time. When the operant habit was well fixed, bilateral microinjection of the same doses of scopolamine into the neostriatum had no effect on the reflex. These results suggest that the neostriatum cholinergic system is critically involved in forming the motor engram. The cholinergic system of the caudate nucleus either takes no part in realizing the well-fixed conditioned reflex movement response and/or other forebrain structures are involved in the reflex, compensating for the disturbance in neostriatal cholinergic function. I. P. Pavlov Institute of Physiology, Russian Academy of Sciences, St. Petersburg. Translated from Fiziologicheskii Zhurnal im. I. M. Sechenova, Vol. 81, No. 8, pp. 139–146, August, 1995.     

Formation of the conditioned reflexes to a complex signal in ontogenesis under alternate choice conditions

The formation of a conditioned reflex to a complex signal, “light+sound,” and its components under alternate choice conditions was studied in kittens aged 1.5–10 months. A preference for one of the food dispensers and a low percent of correct reactions (48–57%) was characteristic during the process of training for kittens aged from 1.5 to 5 months. Successful training using the alternate choice, method was achieved in kittens whose training began at six months of age. A lesion of the sensorimotor region of the cortex in the same kittens following the achievement of a high level of correct reactions (75–80%) led to a disturbance in the previously developed reflex to the complex signal and its components. The latter was expressed in the manifestation of unidirectional motoric reactions and a sharp decrease in the percent of correct reactions. The question of the confinement of the development of different forms of interaction of the sensory and motor systems to specific age periods and the participation in this process of the sensorimotor region of the cortex is discussed. A. A. Ukhtomskii Scientific Research Institute of Physiology, Saint Petersburg State University. Translated from Zhurnal Vysshei Nervnoi Deyatel'nosti imeni I. P. Pavlova, Vol. 45, No. 2, pp. 289–296, March–April, 1995.     

Formation of the conditioned reflexes to a complex signal in ontogenesis under alternate choice conditions

The formation of a conditioned reflex to a complex signal, “light + sound,” and its components under alternate choice conditions was studied in kittens aged 1.5–10 months. A preference for one of the food dispensers and a low percent of correct reactions (48–57%) was characteristic during the process of training for kittens aged from 1.5 to 5 months. Successful training using the alternate choice method was achieved in kittens whose training began at six months of age. A lesion of the sensorimotor region of the cortex in the same kittens following the achievement of a high level of correct reactions (75–80%) led to a disturbance in the previously developed reflex to the complex signal and its components. The latter was expressed in the manifestation of unidirectional motoric reactions and a sharp decrease in the percent of correct reactions. The question of the confinement of the development of different forms of interaction of the sensory and motor systems to specific age periods and the participation in this process of the sensorimotor region of the cortex is discussed. A. A. Ukhtomskii Scientific Research Institute of Physiology, Saint Petersburg State University. Translated from Zhurnal Vysshei Nervnoi Deyatel'nosti imeni I. P. Pavlova, Vol. 45, No. 2, pp. 289–296, March–April, 1995.     

Activation of the cholinergic system of the striatum improves attention to conditioned reflex stimuli

Chronic experiments were performed on 16 dogs using a model of an operant defensive reflex associated with maintenance of a flexion pose to study the effects of uni-and bilateral microinjections of the acetylcholine agonist carbacholine (0.05–0.4 μg) and the choline receptor blocker scopolamine (0.5 μg) into the dorsolateral part of the head of the caudate nucleus andCM-Pf intralaminar thalamic nuclei. These experiments produced data showing that the cholinergic system of the striatum has an important role in realizing the sensory and motor components of the learned movement. Activation of the cholinergic system of the dorsal striatum led to general calming of behavior and inhibition of intersignal limb elevation and the phasic components of the movement, along with ordering and stabilizing of the pose and an increase in the tonic component of the operant response. This suggests that the cholinergic system of the striatum receives an indirect efferent output via motor structures and takes part in preparing the motor apparatus needed for transferring attention to significant stimuli. Microinjections of scopolamine had the opposite effects. Use of differential signals in the same behavioral model, along with special tests for attention, showed that the cholinergic system of the striatum plays an important role in the sensory control of attemtion. Activation of the strital cholinergic system led to a significant improvement in responses to differential signals and defensive signals of intensity 2–3 times slower than normal signals, and these changes were accompanied by clearer responses in special tests for attention. Scopolamine microinjections had the opposite effects. Carbacholine microinjections into the intralaminar thalamic nuclei potentiated the effects of cholinergic activation of the striatum. These data indicate that the dorsal striatum can be regarded not only as a parallel level of information processing, but also as a control system for passing this information to various levels of both sensory and motor structures. One important result of this type of control may be that of improving attention to significant stimuli.     

Long-term potentiation of the late NMDA-dependent components of neuron responses in the cat motor cortex to stimulation of the direct cortical input from field 5 of the parietal cortex

Bicuculline-filled microelectrodes were used to record responses to weak stimulation of the parietal cortex in field 5 of the motor cortex of anesthetized cats, and revealed late excitatory responses of neurons similar to those seen in the motor cortex of conscious cats in response to conditioned stimulation of the parietal cortex triggering a conditioned reflex consisting of placing the paw on a support. Tetanic stimulation of the parietal cortex (10–20 sec, 100 Hz) in the same conditions evoked long-term potentiation of late responses, resulting in the formation and enhancement of responses, along with decreases in the latent period of responses. Translated from Zhurnal Vysshei Nervnoi Deyatel'nosti, Vol. 49, No. 2, pp. 279–286, March–April, 1999.     

Coherence analysis of electrical activity in the rabbit brain during the process of substitution of dominants

Coherence analysis was used to study intercenter relationships between biopotentials in the sensorimotor cortex (forelimb and blink representation areas) and the visual cortex in both hemispheres and the ventrolateral nucleus of the thalamus (VPL) of the left and right thalami during the formation of a motor defensive dominant (electrical stimulation of the limb skin) on a background of an induced (by stimulation of the cornea with an air jet) blink dominant. Characteristic electrophysiological measures of the dominant state (increases in the mean coherence level of potentials in the delta frequency range in, structures involved in the functional defensive limb reflex system), along with the absence of behavioral manifestations of the motor dominant in the blink dominant, indicated that a cryptic potential dominant focus was created in the CNS in these conditions, and that this affected ongoing animal activity. Translated from Zhurnal Vysshei Nervnoi Deyatel'nosti imeni I. P. Pavlova, Vol. 48, No. 4, pp. 616–622, July–August, 1998.     

Sensory and motoric components of various forms of learned movement with change in the activity of the cholinergic system of the neostriatum

The participation of the cholinergic system of the neostriatum in the regulation of sensorily-monitored movements and the differentiation of sensory signals were investigated in 12 Wistar rats, 27 Sprague-Dawley rats, and 6 mongrel dogs, using the following models: 1) the maintenance of learned extension of the forelimb for a specified time (rats); 2) prolonged conditioned reflex flexion of the hind limb (dogs); and 3) active avoidance in a T-maze (rats). It was demonstrated that the injection of carbacholine (0.03 μg) into the dorsolateral division of the caudate nucleus of the rats does not bring about significant changes in the performance of movements associated with the maintenance of tonus of the forelimb, whereas the injection of carbacholine (0.05–0.1 μg) into the same division of the caudate nucleus of the dogs improves the realization of movement associated with the maintenance of tonus of the hind limbs. The injection of a blocker of the cholinergic system (scopolamine in the rats and atropine in the dogs) in both the first and the second instance disturbed the performance of the movement by the animals. Bilateral microinjections of carbacholine (0.03 μg) into the neostriatum of the rats significantly improves the development of a differentiated active avoidance conditioned reflex in a T-maze on the first three days of testing. The differentiation of acoustic signals by dogs also signicicantly improved against the background of the injection of carbacholine (0.05–0.1 μg) into the caudate nucleus. Thus, the data obtained in the various behavioral models and different animals suggest that the cholinergic system of the neostriatum participates in the regulation of both motor and sensory mechanisms in connection with the realization of learned movement. Laboratory of Physiology of Higher Nervous Activity, I. P. Pavlov Institute of Physiology, Russian Academy of Sciences, Saint Petersburg. Laboratory of the Comparative Physiology and Pathology of the Central Nervous System, I. M. Sechenov Institute of Evolutionary Biochemistry and Physiology, Russian Academy of Sciences, Saint Petersburg. Translated from Fiziologicheskii Zhurnal imeni I. M. Sechenova, Vol. 80, No. 12, pp. 34–44, December, 1994.     

The effects of vasopressin on memory processes in java monkeys

The roles of vasopressin (arginine-vasopressin) in controlling conditioned operant food-procuring reflexes and various types of memory were studied in monkeys. Types of memory were: conditioned reflex, image (Hunter-Kerr test), short-term, and long-term. The effects of vasopressin were assessed in terms of objective measures of higher nervous activity: movement and autonomous functions. These studies showed that administration of vasopressin to monkeys had different effects on simple operant food-procuring responses and memory processes. Vasopressin had greater effects on memory processes and the restoration of memory after functional derangements of higher nervous activity. The question of the formation of the two types of effect of vasopressin on higher nervous activity is discussed in relation to the evolution of mammals. Translated from Zhurnal Vysshei Nervnoi Deyatel'nosti, Vol. 49, No. 2, pp. 234–244, March–April, 1999.     

Mechanisms of the formation of reactions of cat motor cortex neurons associated with the triggering of the conditioned placing reflex: A hypothesis

The possible physiological mechanisms of the generation of reactions by neurons of the cat motor cortex during the triggering of a conditioned placing reflex are examined. It is hypothesized that neurons of the motor cortex function as a neuronal generator similar to the spinal generator of locomotion, which can be triggered through ion channels that are controlled by NMDA-type glutamate receptors. The conditions necessary for the opening of these channels under the influence of glutamate are achieved by the conditioned “arousal reaction”, the neurochemical equivalent of which is an intensification of the cholinergic and noradrenergic and/or serotoninergic afferentation to the cortex. M. V. Lomonosov Moscow State University. Translated from Zhurnal Vysshei Nervnoi Deyatel'nosti imeni I. P. Pavlova, Vol. 44, No. 6, pp. 963–973, November–December, 1994.     

Comparison of the depression of H-reflexes following previous activation in upper and lower limb muscles in human subjects

 When conditioning-testing (C-T) stimuli are applied to Ia afferents to elicit H-reflexes, the test reflex is abolished immediately following the conditioning reflex. As the C-T interval is increased, the test response slowly begins to recover, taking several hundred milliseconds to attain control values. The time course of this recovery is known as the H-reflex recovery curve. H- reflex recovery curves were compared using surface EMG and single motor unit activities in lower limb soleus and upper limb flexor carpi radialis (FCR) muscles in seven healthy human subjects. Under rest conditions, the recovery of H-reflexes and single motor unit activity was slow for soleus; the recovery was not complete even in 1 s. In comparison, the recovery was very fast for FCR motor units, occurring in 200–300 ms. The effects of rate of stimulation (0.1–10.0 imp/s) were also examined on the magnitude of H-reflex responses. The reflex response declined with increasing rate of stimulation, the decline being slightly greater in soleus than in FCR. When these phenomena were examined with voluntary facilitation of the spinal cord, the time of recovery shortened and the effect of stimulus rate also diminished. Changes with background facilitation were greater in FCR than in soleus. The differences between the two muscles are attributed mainly to differences in presynaptic inhibition in the two spinal segments, and/or to the differences in dynamics of the transmitter release in terminals of Ia afferents synapsing with slow soleus motoneurons and those synapsing with the fast FCR motoneurons. Received: 23 April 1998 / Accepted: 6 November 1998     

Network Activity in Neurons of the Motor and Prefrontal Areas of the Cortex in Trained Cats in Conditions of Systemic Administration of m-Cholinoreceptor Blockers

Experiments on five cats already trained to an operant conditioned food-procuring reflex to light were used to study the network activity of cells in the frontal and motor areas of the cortex accompanying disruption of conditioned reflex behavior in conditions of systemic administration of m-cholinoreceptor blockers. The activity of cortical neurons and their network properties were assessed using auto- and cross-correlation histograms. Doses of central m-cholinoreceptor blockers (the non-selective blocker scopolamine and the relatively selective m1-cholinoreceptor blocker trihexyphenidyl) disrupted performance of the operant motor reflex but had no effect on the appearance of contextual behavior and responses to switching on of the conditioned signal (standing up, elevating the paw). This was accompanied by 1) changes in the patterns of neuron activity in the moor and frontal areas of the cortex, with increases in train, rhythmic, and rhythmic train activity in cortical cells; 2) appearance of synchronicity in the operation of cortical neurons; 3) decreases in the numbers of direct interneuronal connections in the motor and frontal areas of the cortex and in the numbers of connections between these structures.     

The role of the pineal gland in forming a conditioned reflex to time in rats

The effects of pinealectomy and melatonin on time-associated conditioned reflex behavior were studied. Removal of the pineal gland hindered the formation of a conditioned reflex in conditions of a fixed time interval in rats. This was accompanied by a shortening of latency and excursions and an increase in the number of intersignal responses. Administration of melatonin (0.1 mg/kg) had the opposite effects, facilitating the development of the conditioned response to time and limiting motor activity. Translated from Zhurnal Vysshei Nervnoi Deyatel'nosti, Vol. 48, No. 1, pp. 54–59, January–February, 1998.     

Monoaminergic control by amygdalar nuclei of the reinforcing action of conditional stimuli

The influence of microinfusion of 5-HT, NE, and DA into the amygdalar nuclei on the accomplishment of conditioned reinforcing and conditioned trigger reflexes which are constituents of the CADR was studied in cats with a developed conditioned alimentary discrimination reflex (CADR) in response to two conditional light stimuli set apart on different sides of a box. It was established that 5-HT in doses of 30–50 μg in a volume of 5 μl elicits inhibition; the same doses of NE, by contrast, induces the “hanging-up” of the animals on conditional and conditional—unconditional stimuli which possess the property of reinforcement during the execution of the CADR. The microinfusion of DA in doses of 30–60 μg recalls, from animal to animal, the action of 5-HT and NE. It is hypothesized that the inhibitory functions of 5-HT and the activating actions of NE in the amygdalar nuclei support this structure's control of reinforcing conditional and conditional—unconditional reflexes and the perception of the reinforcing action of conditional stimuli. It is hypothesized that the DAergic innervation of the amygdala does not participate directly in conditioned reflex activity. A. I. Karaev Institute of Physiology, Academy of Sciences of the Azerbaidzhan, Baku. Translated from Zhurnal Vysshei Nervnoi Deyatel'nosti imeni I. P. Pavlova, Vol. 44, No. 2, pp. 254–260, March–April, 1994.     

Morphochemical changes in brain structures and their correction by tuftsin in rats with hypofunction of the dopamine system

Chronic administration of haloperidol to Wistar rats induces specific changes in protein metabolism at the cortical-subcortical level (sensorimotor cortex—caudate nucleus), in associative and integrative triggering neurons, and in the cytoplasm and nucleus of the same neuron, judging from the state of structural proteins and aminopeptidase activity. Tuftsin reduces these changes only in the sensorimotor cortex. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 122, No. 10, pp. 381–383, October, 1996     

Comparative study of the roles of ACTH and β-endorphin in regulating conditioned reflex activity in the hedgehog

Data on the relative effects of the neurohormone ACTH_1–39 and the opioid peptide β-endorphin on conditioned reflex activity in the hedgehog are presented. It was demonstrated that administration of ACTH (30–50 μg/kg s.c.) led to facilitation of learning and strengthening of memory processes (conditioned reflex traces). ACTH promoted strengthening of movement, orientational-investigative, and intersignal activities, produced hyperalgesia, and blocked the effects of naloxone. Administration of β-endorphin (30–40 μg/kg s.c.) lengthened the latent periods of conditioned reflexes, produced a pronounced analgesic effect, and reduced movement and intersignal activities. The effects of β-endorphin were eliminated by dosage with naloxone. Administration of β-endorphin blocked the inhibitor effects of stimulation of the limbic cortex; doses of ACTH produced partial release of inhibitory effects. The differences between the effects of ACTH and β-endorphin on higher nervous activity are discussed, as are the possible mechanisms of these effects. Laboratory for Comparative Cerebellar Physiology (Director R. A. Grigor'yan), I. M. Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, St. Petersburg. Translated from Fiziologicheskii Zhurnal imeni I. M. Sechenova, Vol. 81, No. 12, pp. 20–30, December, 1995.     

Effects of hippocampectomy on the development and recovery of a conditioned reflex to time in rats

Experiments were carried out on rats to study the dynamics of recovery of a conditioned reflex to time after electrolytic lesioning of the dorsal hippocampus and the effects of hippocampectomy on the development of this response. Lesioning of the hippocampus deranged the restoration of a conditioned reflex to time which had been fixed before surgery. In conditions of limited hippocampal damage, the conditioned reflex to time recovered earlier than in sham-operated animals. Animals with more significant damage showed delays in the recovery of the response to time. After hippocampectomy without initial training, the conditioned reflex to time could not be developed regardless of the extent of damage to the hippocampus. This process was also not affected by doses of phenamine of 0.05 mg/kg. Department of Physiology, State University, Stavropol’. Department of Pharmacology, Medical Academy, Stavropol’. Translated from Zhurnal Vysshei Nervnoi Deyatel’nosti imeni I. P. Pavlova, Vol. 47, No. 3, pp. 480–486, May–June, 1997.     

Preparatory band specific premotor cortical activity differentiates upper and lower extremity movement

Event related desynchronization (ERD) allows evaluation of brain signals in multiple frequency dimensions. The purpose of this study was to determine left hemispheric non-primary motor cortex differences at varying frequencies of premovement ERD for similar movements by end-effectors of the upper and lower extremities. We recorded 32-channel electroencephalography (EEG) while subjects performed self-paced right ankle dorsiflexion and wrist extension. Electromyography (EMG) was recorded over the tibialis anterior and extensor carpi ulnaris. EEG was analyzed for premovement ERD within the alpha (8–12 Hz), low beta (13–18 Hz) and high beta (18–22 Hz) frequencies over the premotor, motor, and sensory areas of the left and mesial cortex from −1.5 to 0 s before movement. Within the alpha and high beta bands, wrist movements showed limited topography, but greater ERD over posterior premotor cortex areas. Alpha ERD was also significantly greater over the lateral motor cortex for wrist movements. In the low beta band, wrist movements provided extensive ERD differences to include the left motor and mesial/lateral premotor areas, whereas ankle movements showed only limited ERD activity. Overall, alpha and high beta activity demonstrated distinctions that are consistent with mapping of wrist and ankle representations over the sensorimotor strip, whereas the low beta representation demonstrated the clearest distinctions between the limbs over widespread brain areas, particularly the lateral premotor cortex. This suggests limited leg premovement activity at the dorsolateral premotor cortex. Low beta ERD may be reflect joint or limb specific preparatory activity in the premotor area. Further work is required to better evaluate the extent of this low beta activity for multiple comparative joints.     

The facilitatory and depressive effects of iontophoretically applied acetylcholine on different components of neuron responses in the motor cortex of the cat during performance of a conditioned paw positioning reflex

Iontophoretic application of acetylcholine to neurons in the motor cortex of cats during performance of a conditioned reflex consisting of placing the paw on a support increased neuron excitability and facilitated “extrinsic” connections, resulting in increases in primary responses to electrical stimulation of the parietal region of the cortex, and which was independent of the first effect of suppression, which was seen only in relation to the long-latency components of the response. The functional significance of the differently directed effects of acetylcholine application is indicated by the statistically significant changes in motor reaction times seen in some experiments, which were in the same direction as changes in neuronal responses in the same experiments. Translated from Zhurnal Vysshei Nervnoi Deyatel'nosti, Vol. 48, No. 1, pp. 99–112, January–February, 1998.