September 28th CTE Seminar

Guest Speaker

Title: Dynamics of Human Brain Oscillations During Off-line States

Presenter: Dr. Sujith Vijayan,

Research group: Neural Dynamics and Neural Engineering Lab

Off-line states, such as sleep, are periods during which the internal dynamics of the brain
are relatively independent of external stimuli. The oscillatory dynamics that occur during
these states are thought to be critical for learning and memory and are often disrupted by
disease. Therefore an understanding of these oscillatory dynamics offers the possibility of
both enhancing the cognitive capacities of healthy individuals and providing
pharmacological and stimulation interventions for diseases.

In the first half of my talk I will present a mechanistic model of alpha (8-13 Hz)
oscillations during general anesthesia. In the induction of general anesthesia, behaviorally
defined loss of consciousness coincides with anteriorization—the spatial shift of alpha
power from posterior to anterior regions. We show that anteriorization can be explained
by the differential effect of anesthetic drugs on thalamic nuclei with disparate spatial
projections. In particular, we show that anesthetic drugs can disrupt the alpha activity
generated at depolarized membrane potentials in posteriorly projecting thalamic nuclei
while engaging a new, hyperpolarized alpha in frontally projecting thalamic nuclei.

In the second half of my talk I will present work examining oscillations recorded
intracranially in humans during REM sleep. Although REM sleep is traditionally thought
to consist of irregular activity, we discovered prominent theta (4-8 Hz) and beta (15-35
Hz) oscillations in the frontal cortices, in particular in the anterior cingulate cortex (ACC)
and the dorsolateral prefrontal cortex (DLPFC). These beta and theta rhythms were
coherent between the ACC and the DLPFC, spatially disparate regions that are both
important for memory. The coordination of these rhythms during REM sleep may play an
important role in emotional regulation and in procedural motor and emotional memory
consolidation and has important implications for diseases that are marked by
abnormalities in REM sleep, such as Parkinson’s disease and post-traumatic stress
disorder (PTSD).