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ABSTRACT: The neuronal activity in the primary somatosensory cortex was collected when monkeys performed a haptic-haptic DMS task. We found that, in trials with correct task performance, a substantial number of cells showed significant differential neural activity only when the monkeys had to make a choice between two different haptic objects. Such a difference in neural activity was significantly reduced in incorrect response trials. However, very few cells showed the choice-only differential neural activity in monkeys who performed a control task that was identical to the haptic-haptic task but did not require the animal to either actively memorize the sample or make a choice between two objects at the end of a trial. From these results, we infer that the differential activity recorded from cells in the primary somatosensory cortex in correct performance reflects the neural process of behavioral choice, and therefore, it is a neural correlate of decision-making when the animal has to make a haptic choice.
Journal of Cognitive Neuroscience 03/2012; 24(7):1634-44. · 5.18 Impact Factor
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ABSTRACT: Abacus experts are able to mentally calculate multi-digit numbers rapidly. Some behavioral and neuroimaging studies have suggested a visuospatial and visuomotor strategy during abacus mental calculation. However, no study up to now has attempted to dissociate temporally the visuospatial neural process from the visuomotor neural process during abacus mental calculation. In the present study, an abacus expert performed the mental addition tasks (8-digit and 4-digit addends presented in visual or auditory modes) swiftly and accurately. The 100% correct rates in this expert's task performance were significantly higher than those of ordinary subjects performing 1-digit and 2-digit addition tasks. ERPs, EEG source localizations, and fMRI results taken together suggested visuospatial and visuomotor processes were sequentially arranged during the abacus mental addition with visual addends and could be dissociated from each other temporally. The visuospatial transformation of the numbers, in which the superior parietal lobule was most likely involved, might occur first (around 380 ms) after the onset of the stimuli. The visuomotor processing, in which the superior/middle frontal gyri were most likely involved, might occur later (around 440 ms). Meanwhile, fMRI results suggested that neural networks involved in the abacus mental addition with auditory stimuli were similar to those in the visual abacus mental addition. The most prominently activated brain areas in both conditions included the bilateral superior parietal lobules (BA 7) and bilateral middle frontal gyri (BA 6). These results suggest a supra-modal brain network in abacus mental addition, which may develop from normal mental calculation networks.
PLoS ONE 01/2012; 7(5):e36410. · 4.09 Impact Factor
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ABSTRACT: Previous studies suggested that primary somatosensory (SI) neurons in well-trained monkeys participated in the haptic-haptic unimodal delayed matching-to-sample (DMS) task. In this study, 585 SI neurons were recorded in monkeys performing a task that was identical to that in the previous studies but without requiring discrimination and active memorization of specific features of a tactile or visual memorandum. A substantial number of those cells significantly changed their firing rate in the delay compared with the baseline, and some of them showed differential delay activity. These firing changes are similar to those recorded from monkeys engaged in active (working) memory. We conclude that the delay activity is not necessarily only observed as was generally thought in the situation of active memorization of different features between memoranda after those features have been actively discriminated. The delay activity observed in this study appears to be an intrinsic property of SI neurons and suggests that there exists a neural network in SI (the primary sensory cortex) for haptic working memory no matter whether the difference in features of memoranda needs to be memorized in the task or not. Over 400 SI neurons were also recorded in monkeys well-trained to discriminate two memoranda in the haptic-haptic DMS task for comparison of delay firing of SI neurons between the two different working memory tasks used in this study. The similarity observed in those two situations suggests that working memory uses already-existing memory apparatus by activating it temporarily. Our data also suggest that, through training (repetitive exposure to the stimulus), SI neurons may increase their involvement in the working memory of the memorandum.
Journal of Cognitive Neuroscience 11/2011; 24(3):664-76. · 5.18 Impact Factor
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ABSTRACT: Prefrontal cortex (PFC) has been implicated in modulation of sensory information processing in somatosensory cortex. However, it remains unclear whether or not PFC regulates sensory information in thalamus. In the present study, the effect of PFC stimulation on tactile responses of neurons in the ventrobasal thalamus (VB) of the rat was investigated by single-unit recording. PFC stimulation significantly enhanced the signal-noise ratio (tactile responses/background activities) in 16 out of 66 VB neurons (24.2%) that had receptive fields in fore or hind limbs. Such changes can be classified into three different categories: (1) PFC stimulation not only increased the tactile responses, but also suppressed the background activities of neurons (six neurons, 9.1%); (2) PFC stimulation only increased the tactile responses of neurons (five neurons, 7.6%); (3) PFC stimulation only suppressed the background activities of neurons (five neurons, 7.6%). Our results suggest that PFC also modulates somatosensory information at the thalamic level.
Neuroscience Letters 05/2008; 435(2):152-7. · 2.11 Impact Factor
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ABSTRACT: This study explores the cortical cell dynamics of unimodal and cross-modal working memory (WM). Neuronal activity was recorded from parietal areas of monkeys performing delayed match-to-sample tasks with tactile or visual samples. Tactile memoranda (haptic samples) consisted of rods with differing surface features (texture or orientation of ridges) perceived by active touch. Visual memoranda (icons) consisted of striped patterns of differing orientation. In a haptic-haptic task, the animal had to retain through a period of delay the surface feature of the sample rod to select a rod that matched it. In a visual-haptic task, the animal had to retain the icon for the haptic choice of a rod with ridges of the same orientation as the icon's stripes. Units in all areas responded with firing change to one or more task events. Also in all areas, cells responded differently to different sample memoranda. Differential sample coherent firing was present in most areas during the memory period (delay). It is concluded that neurons in somatosensory and association areas of parietal cortex participate in broad networks that represent various task events and stimuli (auditory, motor, proprioceptive, tactile, and visual). Neurons in the same networks take part in retaining in WM the memorandum for each trial, whether it is encoded haptically or visually. The VH association by parietal cells in WM is analogous to the auditory-visual association previously observed in prefrontal cortex. Both illustrate the capacity of cortical neurons to associate sensory information across time and across modalities in accord with the rules of a behavioral task.
Cerebral Cortex 10/2007; 17 Suppl 1:i77-87. · 6.54 Impact Factor
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ABSTRACT: Our previous studies on scalp-recorded event-related potentials (ERPs) showed that somatosensory N140 evoked by a tactile vibration in working memory tasks was enhanced when human subjects expected a coming visual stimulus that had been paired with the tactile stimulus. The results suggested that such enhancement represented the cortical activities involved in tactile-visual crossmodal association. In the present study, we further hypothesized that the enhancement represented the neural activities in somatosensory and frontal cortices in the crossmodal association. By applying independent component analysis (ICA) to the ERP data, we found independent components (ICs) located in the medial prefrontal cortex (around the anterior cingulate cortex, ACC) and the primary somatosensory cortex (SI). The activity represented by the IC in SI cortex showed enhancement in expectation of the visual stimulus. Such differential activity thus suggested the participation of SI cortex in the task-related crossmodal association. Further, the coherence analysis and the Granger causality spectral analysis of the ICs showed that SI cortex appeared to cooperate with ACC in attention and perception of the tactile stimulus in crossmodal association. The results of our study support with new evidence an important idea in cortical neurophysiology: higher cognitive operations develop from the modality-specific sensory cortices (in the present study, SI cortex) that are involved in sensation and perception of various stimuli.
PLoS ONE 02/2007; 2(8):e771. · 4.09 Impact Factor
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ABSTRACT: We describe the use of near-infrared spectroscopy (NIRS) as a suitable means of assessing hemodynamic changes in the cerebral cortex of awake and behaving monkeys. NIRS can be applied to animals performing cognitive tasks in conjunction with electrophysiological methods, thus offering the possibility of investigating cortical neurovascular coupling in cognition. Because it imposes fewer constraints on behavior than fMRI, NIRS appears more practical than fMRI for certain studies of cognitive neuroscience on the primate cortex. In the present study, NIRS and field potential signals were simultaneously recorded from the association cortex (posterior parietal and prefrontal) of monkeys performing two delay tasks, one spatial and the other non-spatial. Working memory was accompanied by an increase in oxygenated hemoglobin mirrored by a decrease in deoxygenated hemoglobin. Both the trends and the amplitudes of these changes differed by task and by area. Field potential records revealed slow negative potentials that preceded the task trials and persisted during their memory period. The negativity during that period was greater in prefrontal than in parietal cortex. Between tasks, the potential differences were less pronounced than the hemodynamic differences. The present feasibility study lays the groundwork for future correlative studies of cognitive function and neurovascular coupling in the primate.
NeuroImage 06/2005; 26(1):215-20. · 5.89 Impact Factor
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ABSTRACT: Neurons in the monkey's anterior parietal cortex (Brodmann's areas 3a, 3b, 1, and 2) have been reported to retain information from a visual cue that has been associated with a tactile stimulus in a haptic memory task. This cross-modal transfer indicates that neurons in somatosensory cortex can respond to non-tactile stimuli if they are associated with tactile information needed for performance of the task. We hypothesized that neurons in somatosensory cortex would be activated by other non-tactile stimuli signaling the haptic movements--of arm and hand--that the task required. We found such cells in anterior parietal areas. They reacted with short-latency activity changes to an auditory signal (a click) that prompted those movements. Further, some of those cells changed their discharge in temporal correlation with the movements themselves, with the touch of the test objects, and with the short-term memory of those objects for subsequent tactile discrimination. These findings suggest that cells in the somatosensory cortex participate in the behavioral integration of auditory stimuli with other sensory stimuli and with motor acts that are associated with those stimuli.
Behavioural Brain Research 09/2004; 153(2):573-8. · 3.42 Impact Factor
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ABSTRACT: Studies have shown that in the monkey′s associative cerebral cortex, cells undergo sustained activation of discharge while
the animal retains information for a subsequent action. Recent work has revealed the presence of such ″memory cells″ in the
anterior parietal cortex (Brodmann′s areas 3a, 3b, 1, and 2) – the early stage of the cortical somatosensory system. Here
we inferred that, in a cross-modal visuo-haptic short-term memory task, somatosensory cells would react to visual stimuli
associated with tactile features. Single-unit discharge was recorded from the anterior parietal cortex – including areas of
hand representation – of monkeys performing a visuo-haptic delayed matching-to-sample task. Units changed firing frequency
during the presentation of a visual cue that the animal had to remember for making a correct tactile choice between two objects
at the end of a delay (retention period). Some units showed sustained activation during the delay. In some of them that activation
differed depending on the cue. These findings suggest that units in somatosensory cortex react to visual stimuli behaviorally
associated with tactile information. Further, the results suggest that some of these neurons are involved in short-term active
memory and may, therefore, be part of cross-modal memory networks.
Experimental Brain Research 09/1997; 116(3):551-555. · 2.39 Impact Factor
