Biology subjects

Kim-McManus, O.

Publications and source records attributed to Kim-McManus, O..

3 recordsLinked to original sources

bioRxiv2025

Distributed theta networks support the control of working memory: Evidence from scalp and intracranial EEG

We combined scalp EEG and intracranial EEG (iEEG) to identify spectral and network-level signatures of executive control during a delayed match-to-sample task working memory task. To isolate executive processes, we contrasted test and sample phases, matched in perceptual input but differing in cognitive demand. Scalp EEG revealed increased frontal midline theta event-related spectral perturbations (ERSPs), dynamic increases and decreases in posterior theta-alpha ERSPs, and decreased central alpha-beta ERSPs during the test phase. These local spectral changes were accompanied by enhanced frontoposterior theta phase synchrony and network hub strength, predicting higher behavioral accuracy. Using a novel cross-modal scalp EEG-iEEG ERSP similarity approach, we localized the sources of scalp-derived frontal midline, posterior, and central control effects to medial frontal, parietal, temporal, and occipital regions. Our results integrate power and connectivity measures across scalp and iEEG, linking local spectral fluctuations to broader network organization. Together, they support a model in which executive control emerges from flexible, temporally precise coordination between medial frontal control hubs and posterior representational systems.

neuroscience↗

bioRxiv2025

Declarative Memory Through the Lens of Single-Trial Peaks in High-Frequency Power

Declarative memory depends on the coordination of local processing, indexed by high-frequency broadband (HFB) activity, with global network organization, indexed by theta oscillations. However, theta and HFB exhibit asynchronous timing, raising the question of how results of local processing are communicated throughout the network. Using intracranial EEG in patients performing a recognition memory task, we examined this coordination across the medial temporal lobe (MTL) and prefrontal cortex (PFC). HFB peak activity was earlier in the MTL than PFC. Anchoring analyses of theta phase clustering and connectivity to HFB peaks revealed strong phase clustering locked to HFB peaks in the PFC, as well as connectivity between the PFC and MTL that predicted individual memory performance. Graph analysis revealed specific connections amidst sparse network connectivity during memory success. This study demonstrates that transient brain states linked to internal physiological events support memory and refines our understanding of local and network-level process interactions. HighlightsO_LIMemory-linked theta activity is time-locked to internal brain events C_LIO_LINetwork connectivity changes dynamically during memory processing C_LIO_LISparse network connectivity supports successful memory C_LIO_LISpecific sequences of transient states may be critical for declarative memory C_LI

neuroscience↗

bioRxiv2025

Circuit dynamics of approach-avoidance conflict in humans

Debilitating anxiety is pervasive in the modern world. Choices to approach or avoid are common in everyday life and excessive avoidance is a cardinal feature of anxiety disorders. Here, we used intracranial EEG to define a distributed prefrontal-limbic circuit supporting approach and avoidance. Presurgical epilepsy patients (n=20) performed a continuous-choice, approach-avoidance conflict decision-making task inspired by the arcade game Pac-Man, where patients trade-off harvesting rewards against potential losses from attack by the ghost. As patients approached increasing rewards and threats, we found evidence of a limbic circuit mediated by increased theta power in the hippocampus, amygdala, orbitofrontal cortex (OFC) and anterior cingulate cortex (ACC), that drops rapidly during avoidance. Theta band connectivity within this circuit and with the lateral prefrontal cortex increases during approach and falls during avoidance, and amygdala and lateral frontal activity granger-caused the theta oscillations in both the OFC and ACC. Importantly, the degree of network connectivity predicted how long patients approach, with enhanced network synchronicity extending approach times. Finally, when threat is imminent, the system dynamically switches to a sustained increase in high-frequency activity (70-150Hz) in the middle frontal gyrus (MFG), tracking the degree of threat. The results provide evidence for a distributed prefrontal-limbic circuit, mediated by theta oscillations and high frequency activity, underlying approach-avoidance conflict in humans.

neuroscience↗