Time-resolved aperiodic and oscillatory dynamics during human visual memory encoding

Biological neural networks translate sensory information into neural code that is held in memory over long timescales. Theories for how this occurs often posit a functional role of neural oscillations. However, recent advances show that neural oscillations are often confounded with non-oscillatory, aperiodic neural activity. Here we analyze a dataset of intracranial human EEG recordings (N=13; 10 female) to test the hypothesis that aperiodic activity plays a role in visual memory, independent and distinct from oscillations. By leveraging a new approach to time-resolved parameterization of neural spectral activity, we find event-related changes in both oscillations and aperiodic activity during memory encoding. During memory encoding, aperiodic-adjusted alpha oscillatory power significantly decreases while, simultaneously, aperiodic neural activity “flattens out”. These results provide novel evidence for task-related dynamics of both aperiodic and oscillatory activity in human memory, paving the way for future investigations into the unique functional roles of these two neural processes in human cognition. Significance Statement Neural oscillations have been extensively implicated in memory encoding. However, recent advances show that oscillations are often confounded with aperiodic activity, motivating further investigation of aperiodic dynamics in memory. Here we analyze a dataset of intracranial human EEG recordings to test the hypothesis that aperiodic activity plays a role in memory, distinct from oscillations. By leveraging a new approach to time-resolved spectral parameterization, we find event-related changes in both oscillations and aperiodic activity. Based on our observations, we posit a speculative role for aperiodic activity in cognition, complementary to that of neural oscillations, in a form of neural communication through aperiodic dynamics.