Abstracts

Rationale: Children with epilepsy suffer disproportionately higher rates of attention-deficit. The neural mechanisms that underlie selective attention are complex, not well understood, and the precise mechanism underlying epilepsy-related disruption of attentional processes is unknown. Here, we leverage clinically indicated stereotactically implanted electrodes within the anterior cingulate cortex (ACC) to demonstrate phase resetting during attention-demanding tasks and disruption of this process by subclinical epileptic activity.

Methods: Sixteen in-patients in the epilepsy monitoring unit at the Hospital for Sick Children with stereotactically implanted depth electrodes in the ACC were recruited to perform a computer-based attention-demanding task. Instantaneous phase in the theta, alpha, and beta frequency bands were obtained through the Hilbert transform on band-limited recordings time-locked to stimulus presentation.

Results: We observed that attentional shifts are dependent upon theta-band phase resetting immediately following stimulus onset and that the preferred theta phase angle is predictive of reaction time. We also found a selective enhancement of oscillatory coupling between the ACC and the dorsal attention network and decoupling with the default mode network during task performance. When transient focal epileptic activity occurs around the time of stimulus onset, phase resetting is impaired, connectivity changes with attentional and default mode networks are abolished, and reaction times are prolonged.

Conclusions: The results of the present work highlight the fundamental mechanistic role of oscillatory phase in the ACC in supporting attentional circuitry and present novel targets for remediating attention deficits in children.

Funding: Please list any funding that was received in support of this abstract.: Banting & Best Doctoral Research Award - Canadian Institutes of Health Research; Project Grant - Canadian Institutes of Health Research.