The functional role of the motor area of the cortex in the formation of riddance reactions in dogs

A model of instrumental conditioning similar to the classical model (Pavlovian) is proposed. Flexion of the ipsilateral forelimb was elicited while EDS was applied to the hind limb by stimulation of the motor area of the cortex (M1); both stimuli ceased during the raising of the forelimb. Uniform combinations of this kind led to the development of forepaw flexion reactions in response to the EDS of the hind paw. Prolongation of EDS by 3 sec following cortical stimulation led to rapid extinction of the developed reactions. Thus, the possibility of the effective instrumentalization of movements induced by stimulation of the M1 is proven. This argues that the forming “instrumental” connection (drive-motor structures) is addressed directly to the M1. Translated from Zhurnal Vysshei Nervnoi Deyatel'nosti imeni I.P. Pavlova, Vol. 43, No. 3, pp. 478–486, May–June, 1993.     

Effect of csf from animals with damage to the motor cortex on compensation of motor disorders

Rat recipients were trained to cling to a rotating bar, after which the section of the motor cortex in which the right posterior extremity is represented was removed. On the second day after the operation a lyophilizate of CSF taken from the donors on day 7 following an analogous operation was injected suboccipitally into the recipients. The degree of restoration of the motor function in recipients was assessed from the time of clinging to a rotating bar and the number of slips by the right posterior paw. We determined the optimum dose of the lyophilizate of the liquor from the operated donors whose administration to the recipients with an analogous trauma accelerates restoration of the motor function.Translated from Fiziologicheskii Zhurnal SSSR imeni I. M. Sechenova, Vol. 73, No. 12, pp. 1608–1614, December, 1987.     

The inhibitory influence of an acquired escape strategy on subsequent avoidance learning in gerbils

In gerbils an acquired non-avoidance strategy as pre-experience in a shuttle-box was studied in its influence on the learning of a standard avoidance paradigm. Thereby the same cue stimuli, frequency modulated tones (CS) and electric footshocks (US) were used in different behavioral paradigms. In the preexperience sessions the interstimulus interval between CS and US and on the other hand the escapability or inescapability of the US was varied. It was found that the experience with a relatively long interstimulus interval led to a prolonged maintenance of an acquired escape strategy during subsequent standard avoidance learning. This effect increased with the preexperience of an inescapable US. Additional insights into the temporal inhibition of avoidance learning by the pre-experience were provided by behavioral events like attention responses and orienting responses reflecting components of information processing.     

The influence of microiontophoretic application of acetylcholine on the formation of conditioned reactions of neurons of the motor cortex

The activity of neurons of the motor cortex with simultaneous application to them of acetylcholine was recorded in awake rabbits in the process of the development of a conditioned defense reflex. The conditioned reflex changes were found primarily in cholinosensitive neurons. It was shown that iontophoretic application of the mediator promotes the establishment of the conditioned neuronal responses and leads to an increase in their magnitude as compared with reactions recorded in the absence of acetylcholine. It is hypothesized that the influence of acetylcholine on the conditioned reflex cellular process is accomplished through an effect on the state of excitability of the cortical neurons.Translated from Zhurnal Vysshei Nervnoi Deyatel'nosti imeni I. P. Pavlova, Vol. 39, No. 4, pp. 691–698, July–August, 1989.     

Monoamine content in the motor cortex after injury to the opposite motor cortex

In chronic experiments on eight cats a spectrofluorometric study was made of the serotonin, dopamine, and noradrenalin content in the sigmoid cortex of the left cerebral hemisphere 2, 3, 4, and 5–8 days after removal of the symmetrical cortex of the right hemisphere. A decrease in the dopamine content and a tendency for a decrease in the noradrenalin and serotonin content were observed on the 2nd day, at the time of maximal disturbances of locomotor function. On the 3rd–4th and 5th–8th days, during the period of recovery of motor activity, the serotonin level increased, the dopamine content remained low, whereas the noradrenalin level rose considerably. The role of biochemical changes in the motor cortex in the mechanisms of recovery of locomotor function after injury to the symmetrical cortical region is discussed.Laboratory of Pathophysiology of Neurohumoral Regulation, Institute of General Pathology and Pathophysiology, Academy of Medical Sciences of the USSR, Moscow. (Presented by Academician of the Academy of Medical Sciences of the USSR A. M. Chernukh.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 86, No. 9, pp. 270–271, September, 1978.     

Selective modulation of interactions between ventral premotor cortex and primary motor cortex during precision grasping in humans

In humans, the rostral part of the ventral premotor cortex (PMv), the homologue of F5 in monkeys, is known to be critically involved in shaping the hand to grasp objects. How does information about hand posture, that is processed in PMv, give rise to appropriate motor commands for transmission to spinal circuits controlling the hand? Whereas PMv is crucial for skilled visuomotor control of the hand, PMv sends relatively few direct corticospinal projections to spinal segments innervating hand muscles and the most likely route for PMv to contribute to the control of hand shape is through cortico-cortical connections with primary motor cortex (M1). If this is the case, we predicted that PMv–M1 interactions should be modulated specifically during precision grasping in humans. To address this issue, we investigated PMv–M1 connections by means of paired-pulse transcranial magnetic stimulation (TMS) and compared whether they were differentially modulated at rest, and during precision versus power grip. To do so, TMS was applied over M1 either in isolation or after a conditioning stimulus delivered, at different delays, over the ipsilateral PMv. For the parameters of TMS tested, we found that, at rest, PMv exerted a net inhibitory influence on M1 whereas, during power grip, this inhibition disappeared and was converted into a net facilitation during precision grip. The finding that, in humans, PMv–M1 interactions are selectively modulated during specific types of grasp provides further evidence that these connections play an important role in control of the hand.     

Activity in rostral motor cortex in response to predictable force-pulse perturbations in a precision grip task

The purpose of this investigation was to characterize the discharge of neurons in the rostral area 4 motor cortex (MI) during performance of a precision grip task. Three monkeys were trained to grasp an object between the thumb and index finger and to lift and hold it stationary for 2-2.5 s within a narrow position window. The grip and load forces and the vertical displacement of the object were recorded on each trial. On some trials a downward force-pulse perturbation generating a shear force and slip on the skin was applied to the object after 1.5 s of static holding. In total, 72 neurons were recorded near the rostral limit of the hand area of the motor cortex, located close to the premotor areas. Of these, 30 neurons were examined for receptive fields, and all 30 were found to receive proprioceptive inputs from finger muscles. Intracortical microstimulation applied to 38 recording sites evoked brief hand movements, most frequently involving the thumb and index finger with an average threshold of 12 microA. Slightly more than one-half of the neurons (38/72) demonstrated significant increases in firing rate that on average began 284 +/- 186 ms before grip onset. Of 54 neurons tested with predictable force-pulse perturbations, 29 (53.7%) responded with a reflexlike reaction at a mean latency of 54.2 +/- 16.8 ms. This latency was 16 ms longer than the mean latency of reflexlike activity evoked in neurons with proprioceptive receptive fields in the more caudal motor cortex. No neurons exhibited anticipatory activity that preceded the perturbation even when the perturbations were delivered randomly and signaled by a warning stimulus. The results indicate the presence of a strong proprioceptive input to the rostral motor cortex, but raise the possibility that the afferent pathway or intracortical processing may be different because of the slightly longer latency.     

Stimulation of the trunk area of the motor cortex elicits straining in dogs.

To clarify the cortical portion of dogs which corresponds to the portion to perform voluntary straining in human, the posterior sigmoid gyrus of anesthetized dogs was systematically stimulated. When reflex-straining was elicited at constant intervals (10-20 s) by stimulation of pelvic afferents, extra-straining (cortical straining) intervening between reflex-straining was elicited after a latent period (0.2-1.0 s) by pulse train stimulation of a focal portion in the trunk area of the motor cortex (M1). Cortical straining reset cycles of reflex-straining. The minimum threshold intensity was observed in the fifth or sixth layer of the focal portion. No difference was recognized between the firing patterns exhibited during cortical and reflex-straining by the phrenic and rectus abdominis muscle nerves, and by the nerves innervating the glottis adductors and external urethral sphincter. Pulse train stimulation of the focal portion, however, interrupted reflex-straining when it was applied during reflex-straining. Pulse train stimulation of the focal portion also elicited burst firings in the phrenic and abdominal muscle nerves after short latencies (20 and 12 ms). The short-latency bursts disappeared after severance of the medulla pyramis ipsilateral to the stimulated focal portion, but cortical straining induced by stimulation of the same cortical site persisted. Stimulation of the focal portion still elicited straining after severance of the ipsilateral hypothalamus, but not after severance of the cerebral peduncle at the midbrain level. However, the cortical stimulation intensified to about three times occasionally induced straining after severance of the peduncle. From these results, it may be concluded that stimulation of the focal portion in the trunk motor area induces straining through the cerebral peduncle, midbrain tegmentum, and pontine straining reflex center.     

Role of the motor cortex in the rearrangement of a natural movement coordination in dogs

Chronic experiments on dogs were performed to study the activity of the shoulder muscles involved in elevating the forelimb used by the animal to lift a food-containing cup and keep it elevated during eating. At the early stage of acquisition of this operant reaction, limb-lifting occurred with an anticipatory upward head movement; lowering of the head to the feeder was associated with lowering of the lifted limb. The new coordination required for food to be obtained, i.e., maintaining the elevated limb in a posture with the head lowered, could only be achieved as a result of learning. In untrained dogs with the natural coordination, elevation of the limb occurred with activation of the deltoid and teres major muscles, teres minor being active on standing but ceasing its activity before limb elevation. During training the activity of the teres minor muscle changed to the opposite pattern. Limb elevation in the learned coordination was accompanied by activation of all three shoulder flexors. Lesioning of the motor cortex in the projection area of the "working" limb, but not in other areas, led to impairments of the acquired coordination and a new pattern of shoulder muscle activity. These data led to the conclusion that rearrangement of the initial coordination was linked with the formation of a new means of elevating the limb in which the muscle pattern was supported by the motor cortex.     

Anticipatory postural adjustment before bimanual unloading reactions: The role of the motor cortex in motor learning

The role of the motor cortex in forming a learned coordination (stabilization of the forearm on unloading) was studied in humans. Subjects maintained a 1-kg weight with the right (postural) forearm, the weight being attached via an electromagnet. Unloading of the postural arm was initiated by the subjects by lifting a similar load with the left arm. In control experiments, lifting of the load did not lead to unloading of the postural arm. Changes in motor cortex excitability were studied by transcranial magnetic stimulation applied to the representation area of the right biceps muscle in the motor cortex at the beginning and end of the experiments. Repeated unloading tests showed progressive decreases in the amplitude of the movement of the unloaded forearm, which were accompanied by increases in the anticipatory inhibition of the electromyogram of the biceps muscle of the unloaded arm (learning). Muscle responses to transcranial magnetic stimulation during the learning process showed no significant changes. Analysis of normalized muscle responses to transcranial magnetic stimulation (response/baseline) showed that these increased at the end of training and reached a significantly higher level than seen at the beginning of training. These results lead to the conclusion that the motor cortex plays a fundamental role in inhibiting synergies and coordinations which would interfere with the formation of the new coordination during motor learning. __________ Translated from Zhurnal Vysshei Nervnoi Deyatel’nosti imeni I. P. Pavlova, Vol. 56, No. 5, pp. 603–610, September–October, 2006.     

Cardiac changes to signalled shock avoidance in dogs

Alterations in heart rate (HR), left ventricular pressure (LVP), and maximum left ventricular dp/dt (LVdp/dt max) during a signalled avoidance task were studied in eight chronically prepared dogs. Four of these animals comprised a non-shock control group. In experimental animals, HR increased during the first two days of the avoidance task but did not change significantly during the last two days, while LVP remained at the supranormal post-training levels and LVdp/dt max increased over the course of the experiment. Control animals showed no change in HR or LVP, but LVdp/dt max decreased over the four experimental days. Changes in LVdp/dt max in experimentals reflect a consistent increase in cardiac sympathetic activation. However, HR changes indicate an initial increase and a subsequent decrease in sympathetic activity. It was therefore postulated that either differential activation of sympathetic cardiac fibers occurred such that during non-stress periods and subsequent exposure to stress, sympathetic influences predominate which are reflected only in LVdp/dt max changes, or sympathetic and parasympathetic fibers differentially control cardiac function during stress and non-stress conditions.     

The influence of acetylcholine and atropine on the temporary connection in neuronal populations of the motor cortex

The activity of neurons of the sensorimotor cortex during the paired combination of stimulations of brain structures (the medial lemniscus, the reticular nucleus of the midbrain tegmentum, and the pyramidal tract), with an interstimulus interval of 1.2 sec, was investigated in awake nonimmobilized rabbits. During the omission of the reinforcing stimulus at a place of its expected delivery, a complicated complex of reorganizations of the impulse activity of the neurons develops, consisting of the reproduction of responses and changes in impulse activity which differ in configuration from them, and which usually appear at later periods. The direct application of acetylcholine to the cortex facilitates the manifestation of both types of reorganizations of the neuronal activity. The application, on the other hand, of atropine suppresses primarily the second type of reorganizations. In addition, acetylcholine increases the total duration of these electrical indices of the temporary connection of the developed reactions, while atropine decreases it.Translated from Zhurnal Vysshei Nervnoi Deyatel'nosti imeni I. P. Pavlova, Vol. 41, No. 6, pp. 1193–1203, November–December, 1991.