Introduction: Neural oscillations are essential for encoding cognitive and emotional processes. However, the role of non-oscillatory or aperiodic neural activity is less understood. Using intracranial recordings, we examined the role of aperiodic activity during the recall and cognitive regulation of emotional autobiographical memories (AMs) in the amygdala.
Methods: Six patients (mean age 35.9 years, 3 female) implanted with stereotactic EEG electrodes for the localization of seizures participated in an emotional autobiographical memory task. All subjects had a diagnosis of depression and half had PTSD. Participants recalled “calm”, “sad”, and “traumatic” memories for 20 seconds and were instructed to either maintain or reappraise their emotions. Spectral parameterization using Specparam was conducted to isolate the aperiodic 1/f slope of the power spectrum to assess the aperiodic exponent (reflecting excitatory/inhibitory balance of neural activity) within the amygdala, a region implicated in affective disorders.
Results: The mean Beck Depression Inventory, Beck Anxiety Inventory, and PTSD checklist scores were 31.7, 30.7, and 42.2, respectively. Subjects favored reappraisal over suppression strategies based on the Emotional Regulation Questionnaire. Response to Script Driven Imagery scores were highest for traumatic memories. Differences in the aperiodic exponent between the left and right amygdala were identified during emotional AM recall. In PTSD patients, the left amygdala showed decreases in the aperiodic exponent for traumatic memories compared to sad and calm memories. In one patient with severe PTSD (PCL 57), increases in the exponent were observed for traumatic memories in the right amygdala. Cognitive reappraisal of sad and traumatic AMs was found to modulate the exponent component of the aperiodic curve.
Conclusion : Aperiodic neural activity in the amygdala can characterize certain features of emotional memory processing and regulation. Further research is warranted to evaluate the role of aperiodic neural activity as a potential biomarker for affective disorders and a target for therapeutic interventions.
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