Biology subjects

Chen, S. C.-Y.

Publications and source records attributed to Chen, S. C.-Y..

4 recordsLinked to original sources

bioRxiv2025

Post-Ictal Gamma Oscillations Predict Hippocampal Structural Integrity in Mesial Temporal Lobe Epilepsy

The underlying histopathology and epileptic network of patients with mesial temporal lobe epilepsy (mTLE) are difficult to ascertain. Here, we report a novel electrical activity following seizure termination, termed post-ictal gamma oscillations (PIGOs), recorded in mice with intrahippocampal kainic acid injection and a patient with mTLE. PIGOs are characterized by a spectral shift of increased power in gamma frequencies relative to decreased power in other frequencies, generating a gamma peak. PIGOs are accompanied by increased intracellular calcium levels among parvalbumin-positive interneurons and a direct current shift. Only a subgroup of animals in the study had PIGOs. These animals had less pronounced hippocampal sclerosis (HS) than those without PIGOs. To illustrate the translational potential of these findings, we analyzed data from two patients with unilateral mTLE, one with PIGOs and the other without. The patient with PIGOs had symmetrical hippocampi on neuroimaging, whereas the other exhibited overly decreased interictal glucose uptake in left hippocampus, suggesting left-sided HS. After receiving laser ablation of mesial temporal regions, the patient with PIGOs became seizure-free, whereas the other did not. Our results suggest that PIGOs may serve as a biomarker for a milder form of HS in patients with mTLE and for predicting treatment outcomes.

neuroscience↗

bioRxiv2023

Neural Correlates of Perceptual Similarity Masking in Primate V1

Visual detection is a fundamental natural task. Detection becomes more challenging as the similarity between the target and the background in which it is embedded increases, a phenomenon termed "similarity masking". To test the hypothesis that V1 contributes to similarity masking, we used voltage sensitive dye imaging (VSDI) to measure V1 population responses while macaque monkeys performed a detection task under varying levels of target-background similarity. Paradoxically, we find that during an initial transient phase, V1 responses to the target are enhanced, rather than suppressed, by target-background similarity. This effect reverses in the second phase of the response, so that in this phase V1 signals are positively correlated with the behavioral effect of similarity. Finally, we show that a simple model with delayed divisive normalization can qualitatively account for our findings. Overall, our results support the hypothesis that a nonlinear gain control mechanism in V1 contributes to perceptual similarity masking.

neuroscience↗

bioRxiv2021

Similar neural and perceptual masking effects of low-power optogenetic stimulation in primate V1

Can direct stimulation of primate V1 substitute for a visual stimulus and mimic its perceptual effect? To address this question, we developed an optical-genetic toolkit to "read" neural population responses using widefield calcium imaging, while simultaneously using optogenetics to "write" neural responses into V1 of behaving macaques. We focused on the phenomenon of visual masking, where detection of a dim target is significantly reduced by a co-localized medium-brightness pedestal. Using our toolkit, we tested whether V1 optogenetic stimulation can recapitulate the perceptual masking effect of a visual pedestal. We find that, similar to a visual pedestal, low-power optostimulation can significantly reduce visual detection sensitivity, that a sublinear interaction between visual and optogenetic evoked V1 responses could account for this perceptual effect, and that these neural and behavioral effects are spatially selective. Our toolkit and results open the door for further exploration of perceptual substitutions by direct stimulation of sensory cortex.

neuroscience↗

bioRxiv2020

Steady state evoked potential (SSEP) responses in the primary and secondary somatosensory cortices of anesthetized cats: nonlinearity characterized by harmonic and intermodulation frequencies

When presented with an oscillatory sensory input at a particular frequency, F [Hz], neural systems respond with the corresponding frequency, f [Hz], and its multiples. When the input includes two frequencies (F1 and F2) and they are nonlinearly integrated in the system, responses at intermodulation frequencies (i.e., n1*f1+n2*f2 [Hz], where n1 and n2 are non-zero integers) emerge. Utilizing these properties, the steady state evoked potential (SSEP) paradigm allows us to characterize linear and nonlinear neural computation performed in cortical neurocircuitry. Here, we analyzed the steady state evoked local field potentials (LFPs) recorded from the primary (S1) and secondary (S2) somatosensory cortex of anesthetized (ketamine-xylazine) cats while we presented slow (F1=23Hz) and fast (F2=200Hz) somatosensory vibration to the contralateral paw pads and digits. Over 9 experimental sessions, we recorded LFPs from N=1620 and N=1008 bipolar-referenced sites in S1 and S2 using electrode arrays. Power spectral analyses revealed strong responses at 1) the fundamental (f1, f2), 2) its harmonic, 3) the intermodulation frequencies, and 4) broadband frequencies (50-150Hz). To compare the computational architecture in S1 and S2, we employed simple computational modeling. Our modeling results necessitate nonlinear computation to explain SSEP in S2 more than S1. Combined with our current analysis of LFPs, our paradigm offers a rare opportunity to constrain the computational architecture of hierarchical organization of S1 and S2 and to reveal how a large-scale SSEP can emerge from local neural population activities.

neuroscience↗