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Biomedical subjects

H Gemba

Publications and source records attributed to H Gemba.

At least 37 records · Page 2Linked to original sources
PubMed1993

Action of the cerebello-thalamo-cortical projection upon visually initiated reaction-time hand movements in the monkey.

Electrophysiological characterization of thalamo-cortical projections and cerebello-thalamo-cortical pathways was shown by acute experiments in which laminar field potential analysis of responses evoked in the cortex by stimulation of thalamic and cerebellar nuclei was performed in anesthetized monkeys. Based on the results, dynamic activities of cerebro-cerebellar interconnections on voluntary movements were recorded with electrodes chronically implanted in various cortical areas in unanesthetized monkeys and were correlated with their behaviours. Cortical field potentials change in learning processes of visually initiated reaction-time hand movement and in compensating processes after cerebellar hemispherectomy.

Animals↗
PubMed1990

Potential related to no-go reaction in go/no-go hand movement with discrimination between tone stimuli of different frequencies in the monkey.

Monkeys were trained for go/no-go reaction-time hand movement with discrimination between tone stimuli of different frequencies, and field potentials related to the discriminative movement were recorded with electrodes implanted in various cortical areas and analysed by averaging procedure. In the cortex of the dorsal bank of the principal sulcus, surface-negative, depth-positive (s-N, d-P) potentials were recorded specifically on the no-go trial. The same monkey was also examined for go/no-go reaction-time hand movement with color discrimination. In the same monkey, the potentials related to the no-go reaction on the auditory stimulus were recorded in the rostral part of the dorsal bank of the principal sulcus, whereas the s-N, d-P potentials on the no-go visual stimulus were observed in the caudal part of the same bank. It is suggested that the dorsal bank of the principal sulcus is essentially related to the integrative functions such as judgement not to move and suppression of motor execution, and that different loci in this cortical area are respectively active for the functions of different sensory modalities.

Acoustic Stimulation↗
PubMed1990

Cortical field potential associated with hand movement on warning-imperative visual stimulus and cerebellum in the monkey.

Latent time of the hand movement in response to a visual stimulus was found to be very short when a monkey was enough trained with a visual imperative stimulus preceded by a visual warning stimulus at a fixed time interval. Cerebellar hemispherectomy scarcely prolonged the reaction time of the warning-imperative, visually initiated (W-VI) movement in contrast to its marked delaying action upon the simple visually initiated reaction-time (S-VI) movement. Between the warning and imperative stimuli, sustained surface-negative, depth-positive field potentials were recorded in various areas of the prefrontal and premotor cortices and the supplementary motor area of both cerebral hemispheres, besides gradually increasing surface-negative, depth-positive deflections in the motor and somatosensory cortices contralateral to the moving hand. These observations suggest that the sustained activities in the prefrontal and premotor cortices elicited by the warning stimulus overcome deficiency of the cerebellar function for performing fast and stable timing movements.

Animals↗
PubMed1990

Cortical field potentials associated with hand movements triggered by warning and imperative stimuli in the monkey.

Monkeys were trained to move the hand in response to imperative visual stimulus (IS) given 1 s after warning visual stimulus (WS). With implanted electrodes in the cortices, surface-negative (s-N), depth-positive (d-P) sustained potentials between WS and IS were recorded in the prefrontal, premotor and supplementary motor areas in both hemispheres, and gradually increasing s-N, d-P potentials were seen in the forelimb areas of motor and somatosensory cortices contralateral to the hand. It is suggested that the sustained and gradually increasing potentials are related respectively to cortical activities associated with expectation and anticipation of the IS, and to those with a preparatory process for the movement. The latter appeared to be similar to the case of self-paced movements. These potentials may correspond respectively to the early and late components of CNV in the human.

Animals↗
PubMed1989

Suppression of visually initiated hand movement by stimulation of the prefrontal cortex in the monkey.

Five adult monkeys (Macaca fuscata) were trained for the go/no-go hand movement task with discrimination between two different color stimuli. The go stimulus was accompanied by a reward when a monkey lifted a lever by wrist extension within the stimulus duration (500 ms). Whereas the no-go stimulus was not. The monkey revealed the potential specific to the no-go response in the prefrontal cortex, called 'no-go potential', i.e. surface-negative, depth-positive deflexions in the cortex of the dorsal bank of the principal sulcus and of the rostroventral corner of the prefrontal region. Effects of electrical stimulation of these prefrontal areas upon the go response were observed and analyzed in order to study functional significances of the no-go potential. The surface and depth (2.0-3.0 mm) electrodes chronically implanted respectively in various cortical areas of both hemispheres, originally used for recording cortical field potentials, were utilized for bipolar stimulation of the cortical area. A train of brief electrical pulses was delivered to the loci producible of the no-go potential at different times after the onset of go visual stimulus. The stimulation suppressed the go movement by cancelling and delaying. The grade of the suppressor effect depended on the timing of electrical stimulation after the onset of visual stimulus, and was maximal at around the time of appearance of the no-go potential. The suppressor effect was compared with that produced by stimulating some other areas in the prefrontal cortex and the premotor cortex, and was found rather unique in those areas producible of the no-go potential.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Potential related to no-go reaction of go/no-go hand movement task with color discrimination in human.

Twenty-three human subjects were asked to perform a go/no-go reaction-time hand movement task with discrimination between different color light signals, and potentials related to the discrimination task were recorded with plate electrodes placed on the scalp and analyzed by averaging procedures. A negative potential was found to be recorded specifically to no-go trials in the frontal-parietal part of 21 subjects out of 23 tested. In referring to our recent experiments with monkeys, it is suggested that the potential is related to the judgement not to move and/or the suppression of motor execution.

Adult↗
PubMed1988

Changes in cortical field potentials associated with learning processes of audio-initiated hand movements in monkeys.

Field potentials on the surface and at a depth of 2.0-3.0 mm in the cerebral cortex were recorded with chronically implanted electrodes in various areas of a monkey. The potentials associated with movements in response to auditory stimuli (audio-initiated hand movement) were observed during the learning process of the movement. The monkey had to lift a lever by wrist extension within the duration of the stimulus (tone of 1000 Hz) lasting for about 900, 700 or 500 ms depending on the stage of the learning process. On the first training day, potentials appeared in the primary auditory, auditory association, prefrontal and premotor cortices of a naive monkey. The potentials of the auditory association, prefrontal and premotor cortices became less marked on the next and following days. After a few weeks of training, the potential of the auditory association cortex started to increase again, while the monkey still lifted the lever randomly. When the potential of the auditory association cortex grew to a certain extent, the monkey began to respond to the stimulus with the movement, and potentials appeared in the motor cortex in response to the auditory stimulus. After this process, the potentials in the auditory association and motor cortices gradually increased with further training, and the movement became shorter and less variable in reaction time. The potential in the motor cortex was shown to be mediated by the neocerebellum and superficial thalamo-cortical projection.(ABSTRACT TRUNCATED AT 250 WORDS)

Acoustic Stimulation↗
PubMed1987

Effects of cooling the prefrontal and prestriate cortex upon visually initiated hand movements in the monkey.

Local cooling of the prefrontal and prestriate cortex was performed in a monkey which was trained for visually initiated reaction-time hand movement, and effects of the cooling were examined by observing changes of the movement and of field potentials that were recorded with chronically implanted electrodes in various areas of the cerebral cortex. Cooling of the inferior arcuate areas and its rostral extension ('prearcuate' area) in the bilateral hemispheres made reaction times longer and more variable than the control state, and it depressed the cerebellar-mediated potential in the forelimb motor cortex. Cooling of the prestriate cortex induced effects similar to, but weaker than those of the prearcuate area. However, simultaneous cooling of the prearcuate and prestriate areas added considerable influences to the sole cooling of the prearcuate area. In the monkey well-trained for visually initiated conditioned movements, the prearcuate area may be assumed to be center for the sending of motor commands to the motor cortex through the cerebellum and thalamus, and the prestriate area may have a similar albeit weak influence.

Animals↗
PubMed1987

Plasticity of cortical function related to voluntary movement motor learning and compensation following brain dysfunction.

Processes of motor learning and of compensation after localized brain dysfunction were studied in the monkey tasked with conditioned (visually-initiated, reaction-time) hand movements. Field potentials in various cortical areas of the cerebral hemisphere were recorded successively for many months with electrodes implanted on the surface and in the depth of the cortex. The potentials associated with the conditioned movement were found to change during processes of learning the movement and during courses of degradation as well as recovery after the brain dysfunction. Motor learning of the reaction-time movement can be categorized into "recognition" and "skill" learnings. The former is the process for associating the visual stimulus with the movement and accompanied mainly by increasing activities of prefrontal, premotor and prestriate cortices. The latter is attaining better performances in executing the movement, particularly with shorter and more fixed reaction time, and is accompanied by recruitment of the cerebro-cerebellar interaction. The conditioned movements which had been well established were experimentally disturbed by transient, local cooling of different cortical areas or by cerebellar hemispherectomy. Three possible mechanisms of compensation are proposed as follow: 1. Substitution: Compensation occurring immediately through substitutional neuronal circuits. On transient cooling of the forelimb motor cortex, the somatosensory cortex became predominant in motor function and replaced the disabled motor cortex in executing the reaction-time movement, although activity was weak and slow (paretic but not paralytic). Resection of the cerebellar hemisphere also induced the compensatory motor function of the somatosensory cortex so that the movement could be performed although it was weak, slow and clumsy. 2. Relearning: Compensation by relearning through normally unused neuronal circuits. Prolonged and variable reaction times after cerebellar hemispherectomy persisted when the operation included both dentate and interpositus nuclei but recovered within about three weeks when the interpositus nucleus was preserved. It is suggested that the information processing for the well accomplished reaction-time movement is mainly mediated by the cerebro-cerebellar neuronal circuit including the dentate nucleus but is gradually relearned through the normally unused circuits involving the interpositus nucleus after the dentate nucleus lesion. 3. Rebuilding: Compensation by rebuilt neuronal circuits, e.g., by sprouting and/or regeneration (see S. Kawaguchi in this book).

Action Potentials↗
PubMed1987

Cortical field potentials associated with audio-initiated hand movements in the monkey.

Monkeys were trained to respond to auditory stimulus by lifting a lever (audio-initiated hand movement), and field potentials were recorded from various cortical areas with electrodes implanted on the surface and at a depth of 2.0-3.0 mm, depending on the area. Tones of 500, 1000 and 2000 Hz were given to the monkey for about 500 or 10 ms, as auditory stimuli. In association with the movement, potentials of different configurations were recorded respectively in the primary auditory, auditory association, prefrontal, premotor, motor and somatosensory cortices. Initial surface-positive (s-P), depth-negative (d-N) potentials appeared in the primary auditory and auditory association cortices about 20 ms after the onset of the auditory stimulus, and they were often followed by s-N, d-P potentials. In the forelimb area of the motor cortex contralateral to the moving hand, s-N, d-P potentials appeared at a latency of about 100 ms. Following cerebellar hemispherectomy ipsilateral to the moving hand, the s-N, d-P potentials in the forelimb motor cortex were eliminated and reaction times prolonged. The same monkeys were also trained to perform a visuo-initiated movement, and results were compared with each other. Primary sensory and sensory association areas activated during such movements were certainly different, and the prefrontal association cortex appeared to participate much less predominantly in the audio- than in the visuo-initiated movement. Reaction times were generally longer and more variable for the audio- than for the visuo-initiated movement. Nevertheless the cerebello-thalamo-motor cortical projection was found to be recruited in the same manner prior to both movements.

Acoustic Stimulation↗
PubMed1986

'Error' potentials in limbic cortex (anterior cingulate area 24) of monkeys during motor learning.

Two monkeys were trained to lift a lever with wrist extension in response to a visual cue. The animals were chronically implanted with electrodes for recording transcortical field potentials. Unique 'error' potentials were observed in the anterior cingulate cortical area 24 during a transitional learning-stage when the animals were uncertain about fulfilling the required task appropriately. At that stage (III) about 40-60% of the movements were made appropriately within the required cue-time. Error potentials followed inappropriate lever lifts made with wrist movements that were self-paced and hence non-rewarded, but such potentials did not follow appropriately made, i.e. visually initiated, and rewarded lifts.

Animals↗
PubMed1986

Effects of premotor cortex cooling upon visually initiated hand movements in the monkey.

The premotor cortex was temporarily impaired with a local cooling method and effects of the cooling upon visually initiated hand movement and upon cortical field potentials associated with the movement were examined in the monkey. Bilateral cooling of the premotor cortex (the dorsolateral part of presumed area 6) disorganized the well-trained reaction-time movement, in which a lever was lifted within duration of the light stimulus (about 0.5 s) delivered at random time intervals. Accordingly the monkey showed nearly self-paced, random movements with little regard to the light stimulus during the cooling. To obtain a certain number of appropriate reaction-time movements, about twice as many as trials in normal conditions were required during the premotor cooling. Unilateral (contralateral to the moving hand) cooling of the premotor cortex produced similar but weak effects. No appreciable paresis was observed by cooling. Such effects of cooling the premotor cortex faded in successive experimental days of several weeks or even in successive cooling sessions on the same day. This was in contrast with effects of motor cortex cooling which were reported to be almost unfaded on repetition. It is suggested that compensatory actions are quickly elicited in some other structures even on temporal impairment of the premotor cortex and that the actions are gradually accumulated on repetitive cooling with days and weeks.

Animals↗
PubMed1986

Electrical activity in the prefrontal cortex specific to no-go reaction of conditioned hand movement with colour discrimination in the monkey.

Monkeys were trained to perform hand movements in a reaction time task with discrimination between positive (go) and negative (no-go) light signals, and field potentials in various cortical areas were recorded and analysed with chronically implanted cortical electrodes. As previously reported, areas such as the prefrontal, premotor and motor cortices were active in association with simple visually-initiated, reaction-time hand movements. The caudal part of the dorsal bank of the principal sulcus was found to be activated specifically on no-go trials during discrimination, and revealed a relatively sharp surface-negative, depth-positive potential. The potential appeared at a latency of 110-150 ms, which was 150-210 ms earlier than the movement onset on go trials. With reversal of the go and no-go signals, this potential was found to be recorded only on no-go trials, irrespective of the colour used for the stimulus. It is suggested that the activity in the dorsal bank of the principal sulcus is related to the judgement not to execute the movement and/or the suppression of motor execution.

Animals↗
PubMed1984

Distribution of potentials preceding visually initiated and self-paced hand movements in various cortical areas of the monkey.

A monkey was trained to lift a lever by its hand in response to a light stimulus or at self-pace; field potentials preceding, respectively, visually initiated and self-paced movements were recorded in various areas on the dorso-lateral and mesial surface of the cerebral hemisphere, with electrodes implanted chronically on the surface and at 2.5-3.0 mm depth of respective cortical areas. Slowly rising, surface-negative, depth-positive (s-N, d-P) potentials were obtained prior to the self-paced movement in the bilateral premotor cortex, and in the contralateral forelimb motor, somatosensory and mesial premotor areas, resembling 'readiness potentials'. Potentials preceding the visually initiated movement occurred in more cortical areas than the self-paced movement, with characteristic potential features to respective areas. In bilateral prefrontal and prestriate cortices, early s-P, d-N and following s-N, d-P potentials were obtained. Only early s-P, d-N potentials occurred bilaterally in the premotor cortex. In the contralateral forelimb motor area, early s-P, d-N and late s-N, d-P premovement potentials were observed. In the mesial premotor area, s-P, d-N and following s-N, d-P potentials were recorded at a little longer latency and with smaller amplitude than in the motor cortex.

Animals↗
PubMed1984

Compensatory motor function of the somatosensory cortex for dysfunction of the motor cortex following cerebellar hemispherectomy in the monkey.

Electrical activities of the motor and somatosensory cortices preceding visually-initiated hand movements were recorded with electrodes chronically implanted on the surface and at 2.5-3.0 mm depth in the cortex of monkeys, and changes in field potentials in these cortices after cerebellar hemispherectomy were observed for many weeks. As previously reported, a unilateral cerebellar hemispherectomy including the lateral and interpositus nuclei eliminates the cerebellar-mediated superficial thalamo-cortical (T-C) responses recorded in the forelimb motor cortex contralateral to the hemispherectomy. These T-C responses normally precede the hand movement, and the operation results in the delay of movement initiation. The electrodes in the forelimb area of the contralateral primary somatosensory cortex showed an enhancement of superficial T-C responses of the somatosensory cortex for 30-40 days after the operation. The enhanced potentials preceded the delayed movement as do the cerebellar-mediated superficial T-C responses of the motor cortex in normal situations. Local cooling of the somatosensory cortex following the cerebellar hemispherectomy disturbed the reaction time movement for a few weeks after the operation. This effect was rarely encountered in normal monkeys. The present study suggests the compensatory motor function of the somatosensory cortex for the dysfunction of the motor cortex in early weeks after cerebellar hemispherectomy.

Adaptation, Physiological↗
PubMed1984

Studies on cortical field potentials recorded during learning processes of visually initiated hand movements in monkeys.

A monkey was trained to lift a lever by wrist extension in response to a light stimulus. During the learning process of the task over several months, field potentials related not only to the task performance but also to substitution and stimulation experiments were recorded with chronically implanted electrodes on the surface and at a depth of 2.5-3.0 mm in the prefrontal, premotor, motor and prestriate cortices. In the substitution experiment, an examiner lifted a lever for the monkey so that it was watching the light and rewarded without the hand movement. In the stimulation experiment, the same light stimulus was simply delivered to the monkey. In a naive monkey which lifted the lever independently of the stimulus, stimulus-locked potentials were evoked by the task experiment in those cortices except the motor cortex, but none was elicited by the substitution or stimulation experiment. In a well-trained monkey, the substitution and stimulation experiments induced almost the same potentials as those prior to the task movement in respective cortices except the motor cortex, in which the component of cerebellar-induced premovement potential was not observed during the substitution and stimulation experiments. At an intermediate stage of learning, the situation was intermediate between the naive and well-trained stages and most premovement potentials except those in the motor cortex were elicited by the substitution experiment in reduced sizes, but nothing by the stimulation experiment.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Compensatory motor function of the somatosensory cortex for the motor cortex temporarily impaired by cooling in the monkey.

The motor cortex was temporarily impaired by local cooling during repeated execution of visually initiated hand movements in monkeys. The effects of cooling were examined by recording premovement cortical field potentials in the forelimb motor and somatosensory cortices and by measuring reaction time and force exerted by the movement. The cortex was cooled by perfusing cold water (about 1 degree C) through a metal chamber placed on the cortical epidural surface. Cooling of the forelimb motor area lowered temperature of the cortex under the chamber to 20-29 degrees C within 4-5 min. Recording electrodes for cortical field potentials were implanted chronically on the surface and at 2.5-3.0 mm depth of various cortical areas including that being cooled. Spread of cooling to surrounding cortical areas was prevented by placing chambers perfused with warm water (38-39 degrees C) on the areas. Cooling of the forelimb motor area greatly reduced its premovement cortical field potentials, followed by prolonged reaction times of weakened contralateral wrist muscles. Simultaneous recording from the primary somatosensory cortex revealed an enhancement of its premovement field potentials. All changes were completely reversible by rewarming of the motor cortex. Concomitant cooling of the motor and somatosensory cortices entirely paralysed the contralateral wrist muscles. These results suggest that the motor function of the somatosensory cortex becomes predominant and compensates for dysfunction of the motor cortex when it is temporarily impaired.

Afferent Pathways↗