Nonuniform high-gamma (60-500 Hz) power changes dissociate cognitive task and anatomy in human cortex
Charles M Gaona1, Mohit Sharma, Zachary V Freudenburg
1Departments of Biomedical Engineering, Neurological Surgery, and Computer Science, Washington University in St. Louis, St. Louis, Missouri 63130, USA.
Summary
High-gamma-band power changes in the brain are more complex than previously thought. Different frequency sub-bands within the high-gamma range show independent and varied responses, suggesting frequency is key to understanding brain activity.
Area of Science:
- Neuroscience
- Electrophysiology
- Cognitive Science
Background:
- High-gamma-band power changes (>60 Hz) in cortical electrophysiology typically indicate focal, event-related activity.
- A prevailing view suggests these changes stem from asynchronous neural firing, leading to uniform power increases.
- Previous studies showed low- and high-gamma band independence, but not within the high-gamma range itself.
Purpose of the Study:
- To investigate the heterogeneity of induced high-gamma-band (60-500 Hz) power changes in electrocorticographic (ECoG) signals.
- To determine if different high-gamma sub-bands exhibit independent functional responsiveness.
- To explore the role of frequency as a dimension in high-gamma neural dynamics.
Main Methods:
- Analysis of electrocorticographic (ECoG) signals during single-word repetition tasks in six human subjects.
- Time-frequency analyses to examine power changes across different high-gamma sub-bands (60-500 Hz).
- Comparison of power changes across different cognitive tasks (hearing, reading, speaking) and cortical locations (sensorimotor, Broca's area, superior temporal gyrus).
Main Results:
- Functional responsiveness varied across different ECoG high-gamma sub-bands, discriminating between cognitive tasks and cortical locations.
- Power changes within these sub-bands were consistent within single trials and showed distinct time courses.
- Behavior- and location-dependent power changes demonstrated nonuniform trends across subjects and task-relevant brain regions.
Conclusions:
- High-gamma-band power changes are more heterogeneous than previously assumed, with distinct sub-bands showing independent activity.
- Frequency, alongside time and location, is a critical dimension for understanding high-gamma neural dynamics.
- A revised approach is needed for evaluating high-gamma-band cortical activity, considering its frequency-specific characteristics.
