Biology subjects

Han, H.-B.

Publications and source records attributed to Han, H.-B..

5 recordsLinked to original sources

bioRxiv2025

Working memory readout varies with frontal theta rhythms

Increasing evidence suggests that attention varies rhythmically, phase-locked to ongoing cortical oscillations. Here, we report that the phase of theta oscillations (3-6 Hz) in the frontal eye field (FEF) is associated with temporal and spatial variation of the read-out of information from working memory (WM). Non-human primates were briefly shown a sample array of colored squares. A short time later, they viewed a test array and were rewarded for identifying which square changed color (the target). Better performance (accuracy and reaction time) varied systematically with the phase of local field potential (LFP) theta at the time of test array onset as well as the targets location. This is consistent with theta "scanning" across the FEF and thus visual space from top to bottom. Theta was coupled, on opposing phases, to both spiking and beta (12-20 Hz). These results could be explained by a wave of activity that moves across the FEF, modulating the readout of information from WM.

neuroscience↗

bioRxiv2022

Dynamic switching between distinct oscillatory rhythms in prefrontal-amygdala circuits for dimorphic defensive behaviors under natural threats

The medial prefrontal cortex (mPFC) and basolateral amygdala (BLA) are involved in the regulation of defensive behavior under threat, but their engagement in flexible behavior shifts remains unclear. Here, we report the oscillatory activities of mPFC-BLA circuit in reaction to a naturalistic threat, created by a predatory robot in mice. Specifically, we found dynamic frequency tuning among two different theta rhythms ([~]5 or [~]10 Hz) was accompanied by agile changes of two different defensive behaviors (freeze or flight). By analyzing flight trajectories, we also found that high beta ([~]30 Hz) is engaged in the top-down process for goal-directed flights and accompanied by a reduction in fast gamma (60-120 Hz, peak near 70 Hz). The elevated beta nested the fast gamma activity by its phase more strongly. Our results suggest that the mPFC-BLA circuit has a potential role in oscillatory gear shifting allowing flexible information routing for behavior switches. HighlightsO_LIWhen threatened, mice take quick defensive behaviors such as freeze or flight. C_LIO_LImPFC-BLA theta tunes its frequency at 5 or 10 Hz for freeze or flight, respectively. C_LIO_LILow and high theta rhythms in mPFC-BLA emerge in a mutually exclusive way. C_LIO_LImPFC-driven beta emerges during goal-directed flights, coordinating fast gamma in BLA. C_LI eTOC BlurbHan et al. presents neural dynamics of mPFC-BLA network for freeze-or-flight defensive behaviors under naturalistic threats. Tuning the theta frequency in the mPFC-BLA network is for fast and agile actions under a naturalistic threat, and mPFC-driven beta oscillatory burst is for strategic action.

neuroscience↗

bioRxiv2020

Rotational snapping: Illusory rhythmicity induced by global and local motion binding

The complexity of human perceptual system has often been investigated through its atypical function; the illusion. Here, I introduce a new visual illusion induced by rotational motion binding, which leads to a gestalt perception of illusory object rhythmically popping out and fading away. In this illusion, observers reported non-existing rhythm out of rotating Gabor patches (e.g., local rotation) that also have orbital trajectory with opposite direction (e.g., global rotation), only under the particular combinations of parameters. This illusory rhythmicity was four times faster than the average of global/local rotational speed. Image reconstruction using the response-triggered average revealed the rhythmicity is explained by the circular alignment of array, demonstrating the effect of repeated contour integration and its perceptual consequences.

neuroscience↗

bioRxiv2019

Functional dissociation of theta oscillations in the frontal and visual cortices and their long-range network during sustained attention

Theta-band (4-12 Hz) activities in the frontal cortex have been thought to be a key mechanism of sustained attention and goal-related behaviors, forming a phase-coherent network with task-related sensory cortices for integrated neuronal ensembles. However, recent visual task studies found that selective attention attenuates stimulus-related theta power in the visual cortex, suggesting a functional dissociation of cortical theta oscillations. To investigate this contradictory behavior of cortical theta, a visual Go/No-Go task was performed with electroencephalogram recording in mice. During the No-Go period, transient theta oscillations were observed in both the frontal and visual cortices, but theta oscillations of the two areas were prominent in different trial epochs. By separating trial epochs based on subjects short-term performance, we found that frontal theta was prominent in good-performance epochs, while visual theta was prominent in bad-performance epochs, exhibiting a functional dissociation of cortical theta rhythms. Furthermore, the two theta rhythms also showed a heterogeneous pattern of phase-amplitude coupling with fast oscillations, reflecting their distinct architecture in underlying neuronal circuitry. Interestingly, in good-performance epochs, where visual theta was relatively weak, stronger fronto-visual long-range synchrony and shorter posterior-to-anterior temporal delay were found. These findings highlight a previously overlooked aspect of long-range synchrony between distinct oscillatory entities in the cerebral cortex and provide empirical evidence of a functional dissociation of cortical theta rhythms.\n\nIN BRIEFPrevious literature emphasized the pro-cognitive role of coherent oscillatory networks between distal brain regions, such as the fronto-visual theta synchrony. However, such a conceptual framework has been challenged as recent findings revealed distinct behavioral correlates of theta oscillations found in different cortical regions, especially in the frontal and visual cortices. Here, we show that frontal and visual theta represent distinct cortical processes and that the functional connectivity between them increases during sustained attention, especially when one of the two theta rhythms is relatively suppressed. The data presented here highlight a novel aspect of neural long-range synchrony between distinct cortical oscillators with distinct functional significance in task performance.

neuroscience↗

bioRxiv2016

Distinctive BOLD Connectivity Patterns in the Schizophrenia Brain: Machine-learning based comparison between various connectivity measures

Recent functional magnetic resonance imaging (fMRI) studies have found distinctive functional connectivity in the schizophrenic brain. However, most of the studies focused on the correlation analysis to define the functional connectivity for BOLD fluctuations between brain regions, which resulted in the limited understanding to the network properties of altered wirings in the schizophrenic brain. Here I characterized the distinctiveness of BOLD connectivity pattern in the schizophrenic brain relative to healthy brain with various similarity measures in the time-frequency domain, while participants are performing the working memory task in the MRI scanner. To assess the distinctiveness of the connectivity pattern, discrimination performances of the pattern classifier machines trained by each similarity measurement were compared. As a result, the classifier machine trained by cross-spectral coherence pattern in low frequency fluctuation (LFF, 0.01-0.08 Hz band) made better performance than the machine trained by correlation-based connectivity pattern. Interestingly, the classifier machine trained by time-lagging patterns in cross-correlation function of LFF produced higher classifying sensitivity than the machines trained by other measures. These results indicate that there are unobserved but considerable features in the functional connectivity pattern of schizophrenic brain which traditional emphasis on correlation analysis does not capture.

neuroscience↗