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Coding of high frequency vibrations in the awake animal

Whisker vibration at a wide range of frequencies is encoded in the awake barrel cortex (tested between 10 and 700Hz). Preliminary data indicate that 1 to 1 responses are present continuously for at least 1 s (stimulus duration) for the entire range of frequencies. The same vibratory frequencies also elicited responses under anaesthesia (isoflurane), however 1 to 1 responses were present only up to 320Hz.

Phase-locking of high frequency responses appears to be more precise in the awake cortex. The initial 50-100ms of a response may be altered under anaesthesia. The On-response is enhanced, followed by an inhibitory pause of about 40 ms and a rebound activity. Thus, entrainment to the vibratory stimulus begins not before 80 -100ms after response onset. In the awake animal, high frequency components of whisker movements are precisely encoded in the barrel cortex within the first 10ms (as well as for seconds) of cortical activity and thus are features available for texture discrimination.

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