An oscillatory hierarchy controlling neuronal excitability and stimulus processing in the auditory cortex.
EEG oscillations are hypothesized to reflect cyclical variations in the neuronal excitability, with particular frequency bands reflecting differing spatial scales of brain operation. However, despite decades of clinical and scientific investigation, there is no unifying theory of EEG organization, and the role of ongoing activity in sensory processing remains controversial. This study analyzed laminar profiles of synaptic activity [current source density CSD] and multiunit activity (MUA), both spontaneous and stimulus-driven, in primary auditory cortex of awake macaque monkeys. Our results reveal that the EEG is hierarchically organized; delta (1-4 Hz) phase modulates theta (4-10 Hz) amplitude, and theta phase modulates gamma (30-50 Hz) amplitude. This oscillatory hierarchy controls baseline excitability and thus stimulus-related responses in a neuronal ensemble. We propose that the hierarchical organization of ambient oscillatory activity allows auditory cortex to structure its temporal activity pattern so as to optimize the processing of rhythmic inputs.
Lakatos
Peter
P
Cognitive Neuroscience and Schizophrenia Program, Nathan Kline Inst., Orangeburg, New York 10962, USA.
Shah
Ankoor S
AS
Knuth
Kevin H
KH
Ulbert
Istvan
I
Karmos
George
G
Schroeder
Charles E
CE
D000161:Acoustic Stimulation / Q000379:methods; D000818:Animals; D001303:Auditory Cortex / Q000166:cytology* / Q000502:physiology*; D001307:Auditory Perception / Q000502:physiology; D001931:Brain Mapping; D003344:Cortical Synchronization; D005072:Evoked Potentials, Auditory / Q000502:physiology*; D008253:Macaca mulatta; D008297:Male; D009474:Neurons / Q000502:physiology*; D013057:Spectrum Analysis; D013997:Time Factors