Item-specific clustering of high gamma-band activity on theta phase during speech categorization

Pre-stimulus theta phase predicted both neural and perceptual responses in epilepsy patients, with /da/ and /ga/ showing gamma activity clustering at distinct theta phases.

• Why it matters: Theta phase can bias perception, but it was unclear whether these biases align with item-specific theta-gamma phase-amplitude coupling.
• What they did: Ambiguous /da/–/ga/ speech sounds were presented while intracranial electrocorticography recorded activity in epilepsy patients, testing whether perceptual bias matched item-specific theta-gamma PAC.
• The result: /da/ and /ga/ tuned channels exhibited gamma clustering at different theta phases, implying phase-specific pre-activation of item-specific representations that shapes behavior.

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