Biomedical subjects

Jun Tanji

Publications and source records attributed to Jun Tanji.

28 records · Page 2Linked to original sources

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

Reward-based planning of motor selection in the rostral cingulate motor area.

The cingulate motor areas, located in the banks of the cingulate sulcus, constitute a portion of the cingulate cortex of primates. We here present experimental evidence showing that the rostral cingulate motor area (CMAr), but not the caudal one (CMAc) is crucial for the selection of future movements based on reward information. After muscimol injection into the CMAr, monkeys were impaired in selecting movements appropriately on the basis of the amount of reward obtained by performing correct movements. Furthermore, four types of cells in the CMAr were found to reflect a process intervening between detection of reward alteration and selection of a future movement. Each type of cell seems to be involved in responding to the quality of the reward, and to relay that information to change planned movements, and prepare a new movement.

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↗

PubMed2002

The relationship between MI and SMA afferents and cerebellar and pallidal efferents in the macaque monkey.

The purpose of the present study was to determine the interrelationship between the thalamic afferents arising from the cerebellum (Cb) and the internal segment of the globus pallidus (GPi) with the neurons projecting to the primary motor cortex (MI) and to the supplementary motor area (SMA). We combined fluorescent retrograde tracers with a double anterograde labeling technique. Multiple injections of a combination of Diamidino Yellow and Fast Blue were made into either the MI or SMA hand/arm representation as determined by intracortical microstimulation. In the same animal, biotinylated dextran amine was injected into the GPi and horseradish peroxidase conjugated to wheat germ agglutinin was injected into the contralateral cerebellar nuclei. The results revealed that the cerebellar and pallidal thalamic territories are largely separate. The ventral anterior nucleus (VA) and the ventral lateral nucleus pars oralis (VLo) contained a greater density of pallidal labeling while a greater density of cerebellar label was observed more caudally in the ventral posterior lateral nucleus pars oralis (VPLo) as well as in nucleus X (X). Moreover, we observed that the greatest coincidence of retrograde cell labeling was within the pallidal thalamic territory following the SMA injections and within the cerebellar thalamic territory following the MI injections. However, interdigitating foci of pallidal and cerebellar label were also observed particularly in the ventral lateral nucleus pars oralis (VLo) and the ventral lateral nucleus pars caudalis (VLc). In both VLo and VLc, we additionally observed coincidence between the cerebellar labeling and SMA projection neurons as well as between pallidal labeling and MI projection neurons. These data suggest that while MI primarily receives inputs originating from Cb and SMA primarily receives inputs originating from GPi, it also appears that MI and SMA receive secondary afferents arising from GPi and Cb, respectively.

Animals↗

PubMed2002

Cellular activity in the supplementary eye field during sequential performance of multiple saccades.

To investigate how single neurons in the supplementary eye field (SEF) participate in sequential performance of multiple saccades, we analyzed presaccadic activity while monkeys were performing three saccades in six different orders from memory. The saccades in each sequence were separated by a fixation period and initiated from the same fixation point with intervening return saccades. We found that the majority of the presaccadic activity of the SEF neurons differed significantly depending on the numerical position of saccades in each sequence (rank order). This rank-order selectivity was found in parallel with the selectivity for the sequence of three saccades. Our data suggest a role for SEF neurons in the coding of temporally ordered saccadic eye movements.

Animals↗

PubMed2002

Contrasting neuronal activity in the dorsal and ventral premotor areas during preparation to reach.

We compared neuronal activity in the dorsal and ventral premotor areas (PMd and PMv, respectively) when monkeys were preparing to perform arm-reaching movements in a motor-set period before their actual execution. They were required to select one of four possible movements (reaching to a target on the left or right, using either the left or right arm) in accordance with two sets of instruction cues, followed by a delay period, and a subsequent motor-set period. During the motor-set period, the monkeys were required to get ready for a movement-trigger signal to start the arm-reach promptly. We analyzed the activity of 211 PMd and 109 PMv neurons that showed selectivity for the combination of the two instruction cues during the motor-set period. A majority (53%) of PMd neurons exhibited activity significantly tuned to both target location and arm use, and an approximately equal number of PMd neurons showed selectivity to either forthcoming arm use or target location. In contrast, 60% of PMv neurons showed selectivity for target location only and not for arm use. These findings point to preference in the use of neuronal activity in the two areas: preparation for action in the PMd and preparation for target acquisition in the PMv.

Animals↗

PubMed2002

Distribution of eye- and arm-movement-related neuronal activity in the SEF and in the SMA and Pre-SMA of monkeys.

We analyzed neuronal activity in the supplementary eye field (SEF), supplementary motor area (SMA), and presupplementary motor area (pre-SMA) during the performance of three motor tasks: capturing a visual target with a saccade, reaching one arm to a target while gazing at a visual fixation point, or capturing a target with a saccade and arm-reach together. Our data demonstrated that each area was involved in controlling the arm and eye movements in a different manner. Saccade-related neurons were found mainly in the SEF. In contrast, arm-movement-related neurons were found primarily in the SMA and pre-SMA. In addition, we found that the activity of both arm-movement- and saccade-related neurons differed depending on the presence or absence of an accompanying saccade or arm movement. Such context dependency was found in all three areas. We also discovered that activity preceding eye or arm movement alone, and eye and arm movement combined, appeared more often in the pre-SMA and SEF, suggesting their involvement in effector-independent aspects of motor behavior. Subsequent analysis revealed that the laterality of arm representation differed in the three areas: it was predominantly contralateral in the SMA but largely bilateral in the pre-SMA and SEF.

Animals↗

PubMed2002

Effects of image motion in the dorsal premotor cortex during planning of an arm movement.

This study examined whether neuronal activity in the dorsal premotor cortex (PMd) covaries with image motion or actual movement of the arm while planning a target-capturing task when the motor task is guided by an image of the moving arm. For this purpose, we trained a monkey to capture a target on a video screen with the part of the arm displayed on the screen. The target-capturing body part was either the right or left side of the hand image. Because the actual arm movement was invisible, the motor task was guided by the arm image, which was at times right-left inverted on the screen. We found that neuronal activity in the PMd predominantly reflected arm-image movement rather than the actual arm movement, and for half of PMd neurons, the activity differed depending on the target-capturing body-part defined in the right or left side of the arm image.

Animals↗