A historical overview of the study of aperiodic neural activity

The study of aperiodic neural activity – reflecting patterns of non-frequency specific activity that are observed in electrical neural recordings such as M/EEG and intracranial LFP recordings – has recently rapidly expanded as a topic of study. While the extent of this work reflects a newfound interest in the study of aperiodic activity, the study of aperiodic activity itself is not new. There is a rich, though arguably fractured and underappreciated, history of work developing and demonstrating key findings and ideas regarding aperiodic neural activity, dating back many decades. In addition, studies of behavior, physiology, and physics have contributed many ideas, methods, and theoretical frameworks that have informed the study of neural activity. This perspective explores the history of the study of aperiodic neural activity and related topics, covering early discussions of separating oscillatory and aperiodic activity that started in the late 1940s, the emergence of frequency-domain measures of non-frequency specific activity by the mid 1970s, and findings from across the subsequent half-century of work investigating how aperiodic neural activity relates to development, cognition, disease, and more. Collectively, this history set the foundation for key ideas regarding aperiodic activity prior to the recent (re-)emergence of these topics in contemporary work. In summarizing this historical study of aperiodic neural activity, this perspective seeks both to establish the historical context of such work as well as to emphasize the wealth of knowledge available in the historical record to contextualize and contribute to current and future work.