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H Gemba

Publications and source records attributed to H Gemba.

At least 19 recordsLinked to original sources
PubMed2001

Cerebello-thalamo-cortical projections to the posterior parietal cortex in the macaque monkey.

The cerebello-thalamo-posterior parietal cortical projections were investigated electrophysiologically and morphologically in macaque monkeys. In anesthetized monkeys, electrical stimulation of every cerebellar nucleus evoked marked surface-positive, depth-negative (s-P, d-N) cortical field potentials in the superior parietal lobule and the cortical bank of the intraparietal sulcus, but no responses in the inferior parietal lobule. Tract-tracing experiments combining the anterograde method with the retrograde one indicated that the interposed and lateral cerebellar nuclei projected to the posterior parietal cortex mainly through the nucleus ventral lateralis caudalis of the thalamus. The significance of the projections is discussed in connection with cognitive functions.

Animals↗
PubMed1999

Cortical field potentials associated with audio-initiated vocalization in monkeys.

Five monkeys vocalizing at self-pace (self-paced vocalization) were well trained to vocalize in response to a monkey call (audio-initiated vocalization). Field potentials associated with audio-initiated vocalizations were recorded by using electrodes which were implanted chronically on the surface and at a 2.0-3.0 mm depth in various cortical areas. A surface-negative (s-N), depth-positive (d-P) potential (at about 70 ms latency after stimulus onset) was recorded in the rostral bank of the inferior limb of the arcuate sulcus in the left hemisphere, in which an insignificant potential was associated with self-paced vocalizations. An s-N, d-P slow potential which occurred in the motor and somatosensory cortices with a latency of about 300 ms after stimulus, started about 700 ms before vocalizations. The duration and amplitude of this potential was substantially the same with those of the potential which occurred with self-paced vocalizations. Reaction times from stimulus onset to vocalization start were variable, but were about 0.9s on the average. The findings were discussed in connection with reaction-time hand movements.

Acoustic Stimulation↗
PubMed1999

Injection of orphanin FQ/nociceptin into the periaqueductal gray suppresses the forebrain-elicited vocalization in the guinea pig.

Electrical stimulation of the caudoventral part of the anterior cingulate cortex (AC) evokes a species-specific vocalization in the guinea pig. After injections of glutamate receptor antagonists into the periaqueductal gray (PAG) regions where the AC projected, the forebrain-elicited vocalization (FEV) was suppressed completely. This result indicated that the FEV was induced at least partly by glutamatergic activation of PAG neurons. Injection of orphanin FQ/nociceptin (OFQ/N) into the PAG profoundly suppressed the FEV. This inhibitory effect of OFQ/N was not antagonized by naloxone, an opioid receptor antagonist. Since OFQ/N was reported to modify the glutamatergic transmission, the present results suggest that OFQ/N exerts influences upon the vocalization by regulating the glutamatergic inputs into the PAG.

Animals↗
PubMed1999

The role of astrocytes in the development of hepatic encephalopathy.

Thioacetamide (TAA), a hepatotoxin used to ascertain the role of astrocytes in hepatic encephalopathy, was administered to prepare four experimental groups of rats. (The TAA1D, TAA1.5D, TAA2D, and TAA2.5D group rats were perfusion fixated with formalin at 1, 1.5, 2, and 2.5 days, respectively, after initial administration of TAA. In addition, TAA was readministered to the TAA2D and TAA2.5D rats 24 h after the first dose.) Abnormalities of higher brain function and equilibrium that progressed with time were apparent in the rats receiving TAA. On the other hand, innate reflexes (e.g. pupillary reflex) were similar to those in the normal control group. Astrocyte cell areas in the hippocampus, neocortex, hypothalamus, cerebellum, and basal ganglia (striatum) from the TAA rats were significantly larger than in corresponding sites from the normal rats (maximum in TAA1D and TAA1.5D groups). However, there were no differences with respect to the midbrain. Any morphological difference was not observed in neurons between the hepatic encephalopathy and normal rats. Administration of TAA caused hepatic tissue injury that progressed over time. Surprisingly, encephalopathy was apparent even when hepatic injury was mild. These findings suggest that abnormalities in astrocytes, which precede any abnormal change in neurons, play a role in the development of hepatic encephalopathy.

Animals↗
PubMed1998

Two vocalization-related subregions in the midbrain periaqueductal gray of the guinea pig.

Vocal communications are well-developed in guinea pigs: they emit a separation call when isolated from the conspecifics, and vocalize mating calls during sexual activities. Similar calls were induced by the electrical stimulation of the midbrain periaqueductal gray (PAG) and the locations where the separation and mating calls were induced were segregated in the PAG. The morphological findings demonstrated that the PAG subregion where the separation call was induced receives massive input from the anterior cingulate cortex (which is related to social attachment behavior), while the subregion where the mating call was emitted has inputs mainly from the medial hypothalamus (related to sexual behaviors), suggesting that guinea pigs used multiple neuronal networks for various species-specific calls.

Animals↗
PubMed1997

Cerebello-cerebral projections onto the ventral part of the frontal cortex of the macaque monkey.

The cerebellar projections to the ventral part of the frontal cortex were investigated in the Japanese monkey (Macaca fuscata). In anesthetized monkeys, stimulation of either the lateral or interposed cerebellar nucleus evoked marked surface-negative and depth-positive potentials in the face motor area (Mf) and the upper part of the ventral premotor area (PMv) on the contralateral side; responses were hardly recorded in the lower part of PMv including the areas related to the laryngeal movements. Stimulation of the medial cerebellar nucleus induced no significant responses in these areas. The results of the combined anterograde and retrograde tracing study indicated that the cerebellar nuclei projected to Mf and the upper part of PMv mainly through the nucleus ventralis posterior lateralis pars oralis and area X of the thalamus, respectively.

Animals↗
PubMed1997

Motivation-dependent activity in the dorsolateral part of the prefrontal cortex in the monkey.

Field potentials were recorded on self-paced hand and mouth movements with implanted electrodes on the surface and at 2.0-3.0 mm depth in respective cortical areas in seven monkeys. Surface-negative (s-N), depth-positive (d-P) premovement slow potentials were recorded in the prefrontal cortex only when the movements were performed with an intense motivation for a reward. Such a motivation-dependent activity was mainly obtained in the rostral bank of the arcuate sulcus on both sides (except for the inferior limb of the arcuate sulcus in the left hemisphere). Three of the seven monkeys were also tasked with visuo-initiated hand movements. As motivation for reward decreased, s-N, d-P potentials at a latency of about 80 ms after stimulus onset became gradually smaller in the rostral bank of the arcuate sulcus in the right hemisphere. These facts suggest that motivation-dependent activity is represented in the dorsolateral part of the prefrontal cortex in monkeys, and that the cortical part is involved in motivational functions as well as in cognitive functions.

Animals↗
PubMed1997

Cortical field potentials preceding vocalization in monkeys.

Field potentials before vocalization were studied with electrodes chronically implanted on the surface and at a 2.0-3.0 mm depth in various cortical areas in three monkeys. Surface-negative, depth-positive (s-N, d-P) slow potentials prior to vocalization were recorded in the premotor (including the Broca's homolog), motor and somatosensory cortices, and the supplementary motor area (SMA). Such premovement potentials were recorded also in the cingulate and prefrontal cortices when a monkey uttered a sound with intense motivation for reward. Cerebellar hemispherectomy on the right side eliminated the s-N, d-P premovement potentials in the motor cortex and in the posterior bank of inferior limb of the arcuate sulcus (homolog of Broca's area) in the left hemisphere. After the operation, the tone came to have less components of different frequencies, and its duration varied much more than before. These facts suggest that the neocortical area homologous to the human speech area takes part in the generation and control of monkey vocalization together with the cerebellum possibly through cerebro-cerebellar interactions. This is against ideas so far proposed on nonhuman primate vocalization, i.e., it is generally considered that animal vocalization differs fundamentally from human speech.

Animals↗
PubMed1996

Influences of emotion upon parotid secretion in human.

Fluid of the parotid gland was collected from seven human subjects during sleep and four subjects during wakefulness. It was continuously weighed during collection on an electronic balance. The weight value was processed on line by a personal computer, and circadian rhythm in connection with the flow rate of saliva was studied. One subject showed no secretion of saliva throughout sleep, but in the other subjects, saliva was secreted, although it was slight. There was no difference between the flow rate in rapid eye movement (REM) sleep and non-REM sleep. Every subject during wakefulness showed a flow rate in a range from a very high value to one almost equal to the value during sleep. The flow rate during wakefulness varied greatly, and there seemed to be no rhythmic pattern to it. With the aid of auditory or visual stimuli etc., the influence of emotional state upon parotid secretion was investigated in 12 subjects. It was found that the flow rate decreased significantly from an intense, passionate state to a relaxed, pleasant state, to a tense or uneasy state and was lowest in a passive, indifferent state, being almost the same as that during sleep. These findings suggest that secretion of parotid saliva depends more on emotional state than circadian rhythm.

Adult↗
PubMed1996

Studies on integrative functions of the human frontal association cortex with MEG.

Our MEG studies on the human frontal association cortex are briefly reviewed. (1) The no-go potential was first found at go/no-go reaction-time hand movement task with discrimination between different colour light stimuli in the prefrontal cortex of monkeys. The potential was recorded in human subjects with EEG over the scalp, but its current dipoles could be localized only by use of MEG, in the dorsolateral part of the frontal association cortex in both cerebral hemispheres. The function for no-go decision and subsequent suppressor action was thus substantiated in the human frontal cortex. (2) Utterance of a short noun in Japanese was found to be initially preceded by an activity in the lower lateral part of the frontal lobe and then by that around the central sulcus. The area of the former, often in both hemispheres, appears to correspond to Broca's motor speech centre and that of the latter, always in both hemispheres, to correspond to the motor-somatosensory cortices. (3) Intensive and continuous concentration on mental calculation and some 'abstract' thinking for a few minutes were often associated with magnetic theta (5-7 Hz) wave bursts in the frontal part of the scalp. Dipole fitting suggested that the electrical current dipoles occur successively and scattered in wide areas of the frontal lobe on both sides. They are to be called "frontal mental theta wave", revealing dynamic and active participation of the frontal lobe in mental functions.

Adult↗
PubMed1995

Cortical field potentials preceding vocalization and influences of cerebellar hemispherectomy upon them in monkeys.

Field potentials preceding vocalization were recorded with electrodes chronically implanted on the surface and at 2.0-3.0 mm depth in various cortical areas in three monkeys. Surface-negative, depth-positive (s-N, d-P) slow potentials prior to vocalization were recorded in the premotor (including the Broca's homology), motor and somatosensory cortices in both hemispheres, and the supplementary motor area in the cerebral hemisphere. Such premovement potentials were recorded also in the cingulate and prefrontal cortices when a monkey uttered with intense motivation for reward. Cerebellar hemispherectomy on the right side eliminated the s-N, d-P premovement potentials in the motor cortex and in the posterior bank of inferior limb of the arcuate sulcus (homolog of Broca's area) in the left hemisphere. Vocal tone contained less components in different frequencies, and its duration became more variable than before the operation. These facts suggest that the neocortical area homologous to the human speech area takes part in generation and control of monkey vocalization together with the cerebellum, possibly through cerebro-cerebellar interactions, against ideas so far offered on nonhuman primate vocalization.

Action Potentials↗
PubMed1995

Enkephalin-immunoreactive fastigial neurons in the rat cerebellum project to upper cervical cord segments.

By using enkephalin immunohistochemistry combined with retrograde fluorescent labelling, a great majority of neurons in the rat cerebellum sending their axons to the spinal cord were shown to contain enkephalin immunoreactivity. These neurons were numerous and clustered in the fastigial nucleus but far less abundant in other cerebellar nuclei. Enkephalin-immunoreactive fibers present in the ventral horn and the central cervical nucleus of upper cervical cord segments almost completely disappeared contralaterally following kainic acid-induced cell loss in the fastigial nucleus. The results indicate that fastigial and some other cerebellar nucleus neurons provide enkephalin-containing projections toward these spinal sites.

Animals↗
PubMed1995

Field potential change in the prefrontal cortex of the left hemisphere during learning processes of reaction time hand movement with complex tone in the monkey.

Field potentials were recorded with electrodes implanted in various cortical areas while a naive monkey was learning reaction time hand movements with complex tone. When cortical surface-negative, depth-positive potential (at a latency of about 80 ms after a stimulus onset) appeared in the rostral bank of the inferior limb of the arcuate sulcus of the left cerebral hemisphere, and became gradually larger, the monkey began to respond to the stimulus with the movement. As the potential in the prefrontal (prearcuate) cortex and the cerebellar-mediated potential in the motor cortex gradually increased with further training, the movement became quicker and more skillful. Three naive monkeys achieved the movement with complex tone in shorter training days than the movement with pure tone; the movement with pure tone was not accompanied by any significant potential in the prefrontal cortex. It is deduced from the present study, and previous studies on visuo-initiated movements, that the prefrontal area, especially in the left hemisphere, plays a significant role for a monkey to associate a stimulus with appropriate motor execution.

Acoustic Stimulation↗
PubMed1995

Motor speech centres in the frontal cortex.

Activities of the frontal cortices in both cerebral hemispheres preceding utterance of a short word were recorded and analyzed with multichannel SQUID gradiometers. Light stimuli of two different colours of 500 ms duration were delivered in front of a subject at random time intervals and in irregular order of the different colours. The subject should respond to either of the stimuli by uttering a short word, e.g., 'en' [en] ('round' in Japanese) or another by a short simple voice without meaning as a word, e.g., 'e' [e]. The initial sounds of both voices are to be the same, i.e., 'e' [e] in these examples. The 37 gradiometers covering either the left or the right frontal-parietal part of the hemisphere recorded different magnetic fields between the word and the simple voice. Magnetic fields averaged 100 times at the onset of the stimuli revealed that the utterance of a word is preceded by significant magnetic field changes at a peak latency of 120-165 ms from the onset of light stimuli, whereas the utterance of a simple voice is not preceded by such changes. At a peak latency of 160-190 ms, about 20-40 ms before the start of perioral EMGs, both the utterances are commonly preceded by magnetic field changes. Dipole fittings based on these magnetic fields suggest that the earlier magnetic fields reflect electrical activities in the ventral lateral part of the frontal association area, usually in both left and right hemispheres, and that the later fields represent those in the sensorimotor area in both the hemispheres. That part of the frontal association area appears to be the centre for organizing words to speak and to correspond possibly to the Broca's speech area.

Adult↗
PubMed1993

Effect of cooling the dentate nucleus of the cerebellum on hand movement of the monkey.

The functional role of the cerebellum in voluntary movement was investigated by local cooling of the cerebellar nuclei in three Japanese monkeys which performed hand movement tasks in response to visual stimuli. We implanted electrodes in various areas of the cerebral hemispheres to record field potentials in the cortex, and examined effects of the cooling upon the movement and field potentials. Cooling of the dentate nucleus ipsilateral to the moving hand reversibly increased the reaction time and reduced the size of surface-negative, depth-positive (s-N, d-P) field potential in the motor cortex contralateral to the hand. The potential preceded the movement by an almost constant time of about 100 ms in the normal condition. The cooling remarkably prolonged and deviated the time. By shifting the cooling probe to different distances from the nucleus, we noted various decreases of the cooling effect. We also found a close correlation between the size of the s-N, d-P potential and the reaction time, i.e., when the potential was small, the reaction time was long. These findings support the following ideas; the motor command for this task comes to the motor cortex through the cerebello-thalamo-cortical pathway which includes the dentate nucleus, and produces the s-N, d-P potential as EPSP currents in pyramidal neurons in the motor cortex. We also studied self-paced movement task. In some cases, the cooling reduced the size of readiness potential in the motor cortex.

Animals↗
PubMed1993

Changes in cortical field potentials during learning processes of go/no-go reaction time hand movement with tone discrimination in the monkey.

Field potentials were recorded with electrodes implanted in various cortical areas while a monkey acquired a task of go/no-go reaction time hand movement with discrimination between tone stimuli of different frequencies. After a few weeks of training, a surface-negative, depth-positive (s-N, d-P) potential (no-go potential) emerged in the dorsal bank of the principal sulcus. As the potential increased in size in 1-3 months, the monkey gradually discriminated between go and no-go stimuli. The no-go potential is considered to be related to judgement not to move and suppression of motor execution. In the superior temporal gyrus, a s-N, d-P potential at a shorter latency than the no-go potential augmented in size on both go and no-go trials, as the monkey learned the discrimination task. The s-N, d-P potential in this gyrus may reflect an information processing prior to the discrimination in the prefrontal cortex.

Acoustic Stimulation↗
PubMed1993

No-go activity in the frontal association cortex of human subjects.

'No-go potential', specific to the no-go reaction in go/no-go reaction-time hand movement with discrimination between different colour light stimuli, was recorded with electrodes chronically implanted in the prefrontal cortex of monkeys. Similar potentials were widely distributed over frontal-parietal parts of the human scalp on the same no-go reaction. In this report, MEG measurement was made over the scalp of five healthy subjects in order to localize current sources responsible for the scalp potential. We found in- and outflow of magnetic fields over the dorsolateral frontal parts of the head, contra- and ipsilateral to the operant hand. These magnetic fields were most reasonably interpreted to be due to current dipoles localized in the dorsolateral parts of frontal lobes in both contra- and ipsilateral hemispheres, presumably in the prefrontal-premotor areas. No-go decision and subsequent suppression of voluntary movements are suggested to be one of the functional features of the human frontal association cortex, as in the case of monkeys.

Adult↗