Biomedical subjects

Keisetsu Shima

Publications and source records attributed to Keisetsu Shima.

11 recordsLinked to original sources

PubMed2006

Categorization of behavioural sequences in the prefrontal cortex.

Although it has long been thought that the prefrontal cortex of primates is involved in the integrative regulation of behaviours, the neural architecture underlying specific aspects of cognitive behavioural planning has yet to be clarified. If subjects are required to remember a large number of complex motor sequences and plan to execute each of them individually, categorization of the sequences according to the specific temporal structure inherent in each subset of sequences serves to facilitate higher-order planning based on memory. Here we show, using these requirements, that cells in the lateral prefrontal cortex selectively exhibit activity for a specific category of behavioural sequences, and that categories of behaviours, embodied by different types of movement sequences, are represented in prefrontal cells during the process of planning. This cellular activity implies the generation of neural representations capable of storing structured event complexes at an abstract level, exemplifying the development of macro-structured action knowledge in the lateral prefrontal cortex.

Action Potentials↗

PubMed2006

Binary-coded monitoring of a behavioral sequence by cells in the pre-supplementary motor area.

To regulate the temporal structure of a series of behavioral sequences involving multiple actions, it is essential to monitor the progress of the entire behavioral process. To identify the involvement of three cortical motor areas in monitoring behavioral sequences, we examined neuronal activity while monkeys sequentially performed a series of motor tasks in accordance with a predetermined behavioral schedule that included a numerical structure. We found that neurons in the pre-supplementary motor area exhibited activity that appeared to monitor the performance of the behavioral trials in a binary-coded manner. One-half of the activity represented odd-numbered trials within a behavioral sequence, whereas the other one-half represented even-numbered trials. Such neuronal activity, resembling the operation of binary counting elements widely used for constructing artificial computing devices, was rare in the supplementary motor area or in the primary motor cortex.

Action Potentials↗

PubMed2005

Prefrontal cortical cells projecting to the supplementary eye field and presupplementary motor area in the monkey.

We examined the location and spatial distribution of prefrontal cortical (PF) cells projecting to the supplementary eye field (SEF) and presupplementary motor area (pre-SMA) using a double retrograde-labeling technique in monkeys (Macaca fuscata). The SEF and pre-SMA were physiologically identified based on the findings of intracortical microstimulation and single cell recordings. Two fluorescent tracers, diamidino yellow and fast blue, were injected into the SEF and pre-SMA of each monkey. Retrogradely labeled cells in the PF were plotted with an automated plotting system. The cells projecting to the SEF and pre-SMA were mainly distributed in the upper and lower banks of the principal sulcus (area 46), with little overlap. Cells projecting to the SEF, but not to the pre-SMA, were observed in areas 8a, 8b, 9, 12, and 45. These findings suggest that the SEF and pre-SMA receive different sets of information from the PF cells.

Action Potentials↗

PubMed2004

Cingulate cortical cells projecting to monkey frontal eye field and primary motor cortex.

We compared the distribution of cingulate cortical cells projecting to the frontal eye field (FEF) and primary motor cortex (MI) using a multiple retrograde labeling technique. Two fluorescent tracers were injected into physiologically identified FEF and MI in each monkey. The location of cells projecting to the forelimb area of MI served to identify the rostral (CMAr) and caudal (CMAc) cingulate motor areas. We found two foci of cells projecting to the FEF: rostral (CEFr) and caudal (CEFc) cingulate eye field. The CEFr was located rostral to the CMAr, while the CEFc was located rostro-ventral to the CMAc. Cells projecting to the FEF and MI scarcely overlapped, indicating that each area receives different sets of information from the cingulate cortex.

Amidines↗

PubMed2003

Differences in spiking patterns among cortical neurons.

Spike sequences recorded from four cortical areas of an awake behaving monkey were examined to explore characteristics that vary among neurons. We found that a measure of the local variation of interspike intervals, L(V), is nearly the same for every spike sequence for any given neuron, while it varies significantly among neurons. The distributions of L(V) values for neuron ensembles in three of the four areas were found to be distinctly bimodal. Two groups of neurons classified according to the spiking irregularity exhibit different responses to the same stimulus. This suggests that neurons in each area can be classified into different groups possessing unique spiking statistics and corresponding functional properties.

Action Potentials↗

PubMed2002

Spatial distribution and density of prefrontal cortical cells projecting to three sectors of the premotor cortex.

The spatial distribution of prefrontal cortical cells projecting to three different sectors in the premotor cortex was examined. The cells projecting to the three sectors were distributed in separate regions in the dorsolateral prefrontal cortex with a small overlap. Cells projecting to the ventral sector were distributed in the lower bank of the principal sulcus (PS). Those projecting to the restro-dorsal sector were located near the superior limb of the arcuate sulcus, and in the dorsal convexity and upper bank of the PS. Cells projecting to the caudo-dorsal sector were observed in the upper bank of the PS and in the area 8a. These findings suggest that each of the three sectors of the premotor cortex receive different sets of information from the prefrontal cortex.

Amidines↗

PubMed2002

Numerical representation for action in the parietal cortex of the monkey.

The anterior part of the parietal association area in the cerebral cortex of primates has been implicated in the integration of somatosensory signals, which generate neural images of body parts and apposed objects and provide signals for sensorial guidance of movements. Here we show that this area is active in primates performing numerically based behavioural tasks. We required monkeys to select and perform movement A five times, switch to movement B for five repetitions, and return to movement A, in a cyclical fashion. Cellular activity in the superior parietal lobule reflected the number of self-movement executions. For the most part, the number-selective activity was also specific for the type of movement. This type of numerical representation of self-action was seen less often in the inferior parietal lobule, and rarely in the primary somatosensory cortex. Such activity in the superior parietal lobule is useful for processing numerical information, which is necessary to provide a foundation for the forthcoming motor selection.

Animals↗

PubMed2002

New classification scheme of cortical sites with the neuronal spiking characteristics.

Multiple cortical areas are mutually compared on the bases of neuronal spiking characteristics measured through three dimensionless interspike interval statistical coefficients. The spike sequences were recorded from the prefrontal cortical area (PF), the pre-supplementary motor area (Pre-SMA), the supplementary motor area (SMA) and the rostral cingulate motor area (CMAr) of a behaving monkey performing a waiting period task. The distribution of three statistical coefficients is found to be largely dependent on the recording site. By measuring the Hellinger distances among those distributions, Pre-SMA, SMA and CMAr are found to be mutually similar in comparison with PF.

Action Potentials↗

PubMed1987

Effects of morphine on two types of nucleus raphe dorsalis neurons in awake cats.

Forty-nine neurons recorded within the nucleus raphe dorsalis (NRD) in awake cats were classified into 2 groups: 29 regularly firing (clock-like) and 20 irregularly firing (non-clock-like) neurons. Hardly any of the clock-like neurons were influenced either by noxious stimulation (0.1 ml of 5% formalin, s.c.) or by a single dose (1 mg/kg, i.p.) or cumulative doses (0.25, 0.5, 1 mg/kg) of morphine. In contrast, about half the non-clock-like neurons were activated both by noxious stimulation and by administration of morphine. Morphine-induced activation of non-clock-like neurons was dose-related and reversed by naloxone (0.2 mg/kg, i.p.). These findings suggest that clock-like neurons in the NRD are not involved in morphine analgesia. Non-clock-like neurons, however, may play a role in the mediation of such analgesia.

Action Potentials↗

PubMed1984

Arthritis induced in cat by sodium urate: a possible animal model for tonic pain.

An attempt has been made to determine whether cats rendered arthritic by the injection of monosodium urate (MSU) crystals (rod-shaped 40-130 micrometers length) into one knee joint capsule can be used as animal model of tonic (chronic) pain. A limp and a decrease in body weight supported by the injected hind leg's paw occurred approximately 1 h after the MSU (20 mg) injection, reached a maximum at 2-3 h, and lasted for more than 6 h before a gradual return to pre-injection levels. They were diminished by systemic administration and local (the dorsal part of the nucleus raphe dorsalis) application of morphine, this effect being blocked by naloxone. This suggests that the limping and the paw pressure decrease are the reflexion of pain. It is suggested that the animal model of the MSU-induced arthritis is useful for the study of tonic pain.

Animals↗

PubMed1981

Antinociceptive action of morphine and pentazocine on unit activity in the nucleus centralis lateralis, nucleus ventralis lateralis and nearby structures of the cat.

Single neuronal activity has been recorded extracellularly from the nucleus centralis lateralis (CL), ventralis lateralis (VL) and medialis dorsalis (MD) of the cat thalamus. The majority of the CL, VL and MD neurons were excited by nociceptive stimulation such as pinching the skin with serrated forceps and/or intra-arterial injection of bradykinin. The nociceptive neurons were also driven by non-nociceptive stimulation such as tap of deep tissues, bending hairs and an air-puff and/or joint rotation, and their receptive fields were large. After intravenous administration of either morphine or pentazocine, most nociceptive neurons became unresponsive to nociceptive stimuli, although they were driven by non-nociceptive stimuli. This suggests that morphine and pentazocine have a specific antinociceptive action on these nociceptive neurons. Intravenous naloxone reversed the antinociceptive action of morphine, but failed to reduce the action of pentazocine. This differentiation has an important functional significance.

Animals↗