Papers by Bidhan Lamichhane
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Brain Connectivity, 2013
Our perception of the temporal order of everyday external events depends on the integrated sensor... more Our perception of the temporal order of everyday external events depends on the integrated sensory information in the brain. Our understanding of the brain mechanism for temporal-order judgment (TOJ) of unisensory events, particularly in the visual domain, is advanced. In case of multisensory events, however, there are unanswered questions. Here, by using physically synchronous and asynchronous auditory-visual events in functional magnetic resonance imaging (fMRI) experiments, we identified the brain network that is associated with the perception of the temporal order of multisensory events. The activation in the right temporo-parietal junction was modulated by the perception of asynchronous audiovisual events. During this perception of temporal order, the right dorsolateral prefrontal cortex coordinated activity with the right temporo-parietal and the left inferior parietal cortices. These results suggest that the TOJ in the multisensory domain underlies a network activity between parietal and prefrontal cortices unlike the regional activity in the right temporo-parietal junction in the unisensory visual domain.
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Diverse cortical structures are known to coordinate activity as a network in relaying and process... more Diverse cortical structures are known to coordinate activity as a network in relaying and processing of visual information to discriminate visual objects. However, how this discrimination is achieved is still largely unknown. To contribute to answering this question, we used face-house categorization tasks with three levels of noise in face and house images in functional magnetic resonance imaging (fMRI) experiments involving thirty-three participants. The behavioral performance error and response time (RT) were correlated with noise in face-house images. We then built dynamical causal models (DCM) of fMRI blood-oxygenation level dependent (BOLD) signals from the face and house category-specific regions in ventral temporal (VT) cortex, the fusiform face area (FFA) and parahippocampal place area (PPA), and the dorsolateral prefrontal cortex (dlPFC). We found a strong feed-forward intrinsic connectivity pattern from FFA and PPA to dlPFC. Importantly, the feed-forward connectivity to dlPFC was significantly modulated by the perception of both faces and houses. The dlPFC-BOLD activity, the connectivity from FFA and PPA to the dlPFC all increased with noise level. These results suggest that the FFA-PPA-dlPFC network plays an important role for relaying and integrating competing sensory information to arrive at perceptual decisions.
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Nepal Journal of Obstetrics and Gynaecology, 2014
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NeuroImage, 2014
Oscillatory interactions within functionally specialized but distributed brain regions are believ... more Oscillatory interactions within functionally specialized but distributed brain regions are believed to be central to perceptual and cognitive functions. Here, using human scalp electroencephalography (EEG) recordings combined with source reconstruction techniques, we study how oscillatory activity functionally organizes different neocortical regions during a tactile discrimination task near the limit of spatial acuity. While undergoing EEG recordings, blindfolded participants felt a linear three-dot array presented electromechanically, under computer control, and reported whether the central dot was offset to the left or right. The average brain response differed significantly for trials with correct and incorrect perceptual responses in the timeframe approximately between 130 and 175ms. During trials with correct responses, source-level peak activity appeared in the left primary somatosensory cortex (SI) at around 45ms, in the right lateral occipital complex (LOC) at 130ms, in the ...
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Brain Connectivity, 2013
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Brain connectivity, Jan 12, 2015
The anterior insulae (INSs) are involved in accumulating sensory evidence in perceptual decision-... more The anterior insulae (INSs) are involved in accumulating sensory evidence in perceptual decision-making independent of the motor response, whereas the dorsal anterior cingulate cortex (dACC) is known to play role in choosing appropriate behavioral responses. Recent evidence suggests that INSs and dACC are part of the salience network (SN), a key network known to be involved in decision-making and thought to be important for the coordination of behavioral responses. However, how these nodes in SN contribute to the decision-making process from segregation of stimuli to the generation of an appropriate behavioral response remains unknown. In this study, we scanned thirty-three participants in fMRI and asked them to decide whether the presented pairs of audio (a beep of sound) and visual (a flash of light) stimuli were synchronous or asynchronous. Participants reported their perception with a button press. Stimuli were presented in block of eight pairs with a temporal lag (ΔΤ) between t...
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Papers by Bidhan Lamichhane