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Biomedical subjects

H Mushiake

Publications and source records attributed to H Mushiake.

30 records · Page 2Linked to original sources
PubMed1993

Preferential activity of dentate neurons during limb movements guided by vision.

1. We recorded the activity of dentate neurons while monkeys (n = 2) performed sequential pointing movements under two task conditions: visually guided and remembered. For both conditions, a monkey faced a panel with five touch pads. The animal began a trial by placing his right hand on a hold key in front of him. In the Remembered Sequence Task, light-emitting diodes (LEDs) over three touch pads were illuminated in a sequence as an instruction to the monkey. At the end of a variable instruction period, an auditory "Go" signal told the monkey to release the hold key and press the touch pads according to the instructed sequence. In the Tracking Task, the monkey was required to press three touch pads immediately after the LED over each of them was illuminated. 2. We recorded from 172 neurons in the dentate that showed task-related changes in activity during the reaction time (RT) period (i.e., the interval between the onset of the Go signal and the release of the hold key). Approximately 40% of these neurons were considered task-dependent because they displayed exclusive or enhanced (> +/- 50%) changes in peak activity during the RT period for one of the two task conditions. Almost 80% of the task-dependent neurons displayed exclusive or enhanced activity changes during the Tracking Task. Many of these neurons were located ventral and lateral to dentate neurons, which were not task-dependent. 3. These results suggest that a portion of the dentate nucleus is preferentially involved in the generation and/or guidance of movement based on visual cues.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Reorganization of activity in the supplementary motor area associated with motor learning and functional recovery.

The supplementary motor area (SMA) of primates has been implicated in the initiation and execution of limb movements. However, when a motor task was extensively overlearned, few SMA neurons, if any, were active before the movement onset. Subsequent lesions of the primary motor cortex gave rise to the appearance of premovement activity changes, indicating usedependent reorganization of the neuronal activity in SMA.

Animals↗
PubMed1991

Two movement-related foci in the primate cingulate cortex observed in signal-triggered and self-paced forelimb movements.

1. Single-unit activity in the cingulate cortex of the monkey was recorded during the performance of sensorially (visual, auditory, or tactile) triggered or self-paced forelimb key press movements. 2. Microelectrodes were inserted into the broad rostrocaudal expanse of the cingulate cortex, including the upper and lower banks of the cingulate sulcus and the hemispheric medial wall of the cingulate gyrus. 3. A total of 1,042 task-related neurons were examined, the majority of which were related to the execution of the key press movements. In greater than 60% of them, the movement-related activity preceded the activity in the distal flexor muscles. 4. The movement-related neurons were distributed, in two foci, in the posterior and anterior parts of the cingulate cortex, both including the upper and lower banks of the cingulate sulcus. The posterior focus was found to largely overlap the area projecting to the forelimb area of the primary motor cortex by the use of the horseradish peroxidase (HRP) method. 5. About 40% of the cingulate cortical neurons showed equimagnitude responses during the signal-triggered and self-paced movements. The neurons exhibiting a selective or differential response to the self-paced motor task were more frequently observed in the anterior than in the posterior cingulate cortex. 6. The long-lead type of changes in activity, ranging from 500 ms to 2 s, were observed mainly before the self-paced and, much less frequently, before the triggered movements. They were particularly abundant in the anterior cingulate cortex. 7. Only a few of the neurons showed activity time-locked to the onset of the sensory signals. 8. These observations indicate that the anterior and posterior parts of the cingulate cortex are distinct entities participating in the performance of limb movements, even if the movements are simple, such as those in this study.

Animals↗
PubMed1991

Neuronal activity in the primate premotor, supplementary, and precentral motor cortex during visually guided and internally determined sequential movements.

1. Single-cell activity was recorded from three different motor areas in the cerebral cortex: the primary motor cortex (MI), supplementary motor area (SMA), and premotor cortex (PM). 2. Three monkeys (Macaca fuscata) were trained to perform a sequential motor task in two different conditions. In one condition (visually triggered task, VT), they reached to and touched three pads placed in a front panel by following lights illuminated individually from behind the pads. In the other condition (internally guided task, IT), they had to remember a predetermined sequence and press the three pads without visual guidance. In a transitional phase between the two conditions, the animals learned to memorize the correct sequence. Auditory instruction signals (tones of different frequencies) told the animal which mode it was in. After the instruction signals, the animals waited for a visual signal that triggered the first movement. 3. Neuronal activity was analyzed during three defined periods: delay period, premovement period, and movement period. Statistical comparisons were made to detect differences between the two behavioral modes with respect to the activity in each period. 4. Most, if not all, of MI neurons exhibited similar activity during the delay, premovement, and movement periods, regardless of whether the sequential motor task was visually guided or internally determined. 5. More than one-half of the SMA neurons were preferentially or exclusively active in relation to IT during both the premovement (55%) and movement (65%) periods. In contrast, PM neurons were more active (55% and 64% during the premovement and movement periods) in VT. 6. During the instructed-delay period, a majority of SMA neurons exhibited preferential or exclusive relation to IT whereas the activity in PM neurons was observed equally in different modes. 7. Two types of neurons exhibiting properties of special interest were observed. Sequence-specific neurons (active in a particular sequence only) were more common in SMA, whereas transition-specific neurons (active only at the transitional phase) were more common in PM. 8. Although a strict functional dichotomy is not acceptable, these observations support a hypothesis that the SMA is more related to IT, whereas PM is more involved in VT. 9. Some indications pointing to a functional subdivision of PM are obtained.

Animals↗
PubMed1990

Selective coding of motor sequence in the supplementary motor area of the monkey cerebral cortex.

We describe a property of neurons in the supplementary motor area (SMA) of the cerebral cortex of monkey that is different from those in the primary motor area (M1) in relation to execution of a sequential motor task. A group of SMA neurons was active when the animal remembered and pressed three touch-pads in a predetermined sequence but inactive when the same movement was guided by sequentially presented visual signals. This finding indicates that the SMA is involved in the performance of sequential movements on the basis of the information stored inside the brain.

Animals↗
PubMed1990

An output zone of the monkey primary motor cortex specialized for bilateral hand movement.

We have identified a subregion in the monkey primary precentral motor cortex (MI) that is characterized by its relationship to bilateral or ipsilateral hand movements. The subregion is located between the digit and face representation areas. The majority of single cells in this portion of MI exhibit distinct activity before and during visually triggered key-press movements performed by means of ipsilateral or contralateral digit flexion. Intracortical microstimulation evoked responses of ipsilateral, in addition to contralateral, digit muscles.

Animals↗
PubMed1989

Slow fluctuations of single unit activities of hippocampal and thalamic neurons in cats. I. Relation to natural sleep and alert states.

Spontaneous unit discharges during the natural sleep-wakefulness cycle in two different neuronal groups, the hippocampal pyramidal cells and thalamic ventrobasal neurons, have been analyzed. The results show that both neurons fire with white-noise-like fluctuations during the slow-wave sleep, and with slow fluctuations with power spectral densities inversely proportional to the frequency in the frequency range of 0.02-1.0 Hz, during the paradoxical sleep. This confirms that the characteristics of fluctuations in neuronal activities of the mesencephalic reticular formation observed in our previous study are more general phenomena in the cat's brain. Partly similar behavior of spectral densities is also observed during the alert state. These observations are quantitatively confirmed by the statistical time series analysis of the spike density processes of spontaneous activities.

Action Potentials↗
PubMed1989

Slow fluctuations of single unit activities of hippocampal and thalamic neurons in cats. II. Role of serotonin on the stability of neuronal activities.

A series of experiments was carried out both in the hippocampal pyramidal and thalamic ventrobasal neurons to investigate the effect of serotonin level in the brain on slow fluctuations of neuronal discharges. Single neuronal activities were recorded in the following two pharmacologically treated states: (1) a 5-hydroxytryptamine depleted state by p-chlorophenylalanine administration (PCPA phase) and (2) a 5-methoxy-N,N-dimethyltryptamine administered state under the PCPA pretreatment (5-MeODMT phase). The slow fluctuations of neuronal activities in the frequency range of 0.02-1.0 Hz in both nuclei were prominent during the PCPA phase and were similar to those during the paradoxical sleep. In contrast, slow fluctuations were suppressed during the 5-MeODMT phase and neuronal activities during this phase were similar to those during slow wave sleep (SWS). The results show that serotonin in the brain definitely plays a role in stabilizing single neuronal activities.

Action Potentials↗
PubMed1989

Activity of digital area neurons of the primary somatosensory cortex in relation to sensorially triggered and self-initiated digital movements of monkeys.

Single-cell activity was examined in digital areas of the primary somatosensory cortex (SI) of monkeys performing sensorially triggered and self-initiated digital movements with the aim of rigorously determining the relative timing of onset of the neuronal activity with respect to movement onset. The activity of prime mover muscles for execution of a key-press movement was recorded simultaneously with the neuronal activity; movement onset was defined as the onset of muscle activity. Neuronal receptive fields were also identified. The following findings emerged from this study: (1) Few neurons, if any, in the SI(areas 3b, 1, 2), including pyramidal tract neurons, were active prior to movement onset. (2) The movement-related activity of SI neurons was basically similar in cases of signal-triggered and self-initiated movement. (3) No neuron in the SI showed activity associated with ipsilateral digital movement. (4) A majority of movement-related neurons in the precentral motor cortex, in contrast, started their activity before movement onset. These findings suggest that SI neuronal activity participates little in providing information necessary for developing motor responses in the initial phase of simple digital movements.

Afferent Pathways↗
PubMed1988

Fluctuations in spontaneous discharge of hippocampal theta cells during sleep-waking states and PCPA-induced insomnia.

1. The spontaneous activity of hippocampal theta cells in head-restrained cats was recorded during slow-wave sleep (SWS), paradoxical sleep (PS), and the attentive state of bird watching (BW). We also recorded theta cell activity during a state of insomnia with pontogeniculoocipital (PGO) waves, which was induced by the administration of p-chlorophenylalanine (PCPA), a selective inhibitor of serotonin synthesis. 2. The time-dependent structure of fluctuations in theta cell activity was evaluated by power spectral analysis and Markovian analysis. The coefficient of variation for these time series was used as a measure of the variability of theta cell activity, which indicates the relative amplitude of fluctuations. 3. During SWS, theta cell activity showed a larger variability and a flat spectrum, i.e., low Markovian properties. During PS, this activity exhibited smaller variability and high spectral density in a low-frequency band (0.01-1.0 Hz), i.e., high Markovian properties. During BW, variability, spectral and Markovian properties were intermediate. 4. The firing pattern of theta cells during PCPA-induced insomnia was similar to that during PS. However, after the administration of either a serotonin agonist, 5-Methoxy-N,N-dimethyltryptamine, or a choline antagonist, atropine sulfate, theta cell activity no longer exhibited PS-like fluctuations, revealing instead a firing pattern similar to that during SWS. 5. During PS and PCPA-induced insomnia, not only the unit activity of theta cells, but PGO activity and theta wave frequency exhibited slow fluctuations, i.e., the high spectral density in the low-frequency band (0.01-1.0 Hz). 6. Cross-correlation analyses were performed between the fluctuations in theta cell activity, theta wave frequency, and PGO activity. These fluctuations correlated with each other during both PS and PCPA-induced insomnia. Bursts of PGO waves especially contributed to these cross-correlations. 7. These results suggest, first, that the slow fluctuations of the theta cell activity during PS and PCPA-induced insomnia is the physiological expression of the removal of aminergic influences and, secondly, that they are dependent on cholinergic mechanisms, including PGO generators.

Action Potentials↗
PubMed1986

Markov-dependency and spectral analyses on spike-counts in mesencephalic reticular neurons during sleep and attentive states.

Spontaneous activities of the mesencephalic reticular formation (MRF) neurons of head-restrained cats were recorded to investigate their dynamic properties during sleep and waking. The Markov-dependency and spectral analyses were performed on the time series of counts converted from the MRF spike-train. During slow-wave sleep (SWS), MRF neurons fired with low Markovian properties and had a similar spectral-density curve as white noise; during paradoxical sleep (PS), their firing pattern showed high Markovian properties owing to low-frequency fluctuations, with spectral densities inversely proportional to frequency (the l/f spectrum). During the attentive state of bird watching (BW), intermediate Markovian properties were observed. These results confirmed both the rest theory of SWS and the activation of the brain during PS from the viewpoint of dynamic information-processing. Furthermore, the activation of the brain during PS may be greater than in BW.

Animals↗