Anesthesia suppresses nonsynchronous responses to repetitive broadband stimuli

University of Oklahoma, 865 Asp Avenue, Felgar Hall 210, Norman, OK 73019, USA.
Neuroscience (Impact Factor: 3.36). 04/2007; 145(1):357-69. DOI: 10.1016/j.neuroscience.2006.11.043
Source: PubMed


Although many aspects of sensory processing are qualitatively similar in awake and anesthetized subjects, important state-dependent differences are known to exist. To investigate the effects of anesthesia on temporal processing in rat auditory cortex, multi-unit neural responses to trains of broadband clicks were recorded prior to, 15 min following, and 5 h following the administration of a ketamine-based anesthetic. While responses to clicks in isolation were relatively stable between states, responses to subsequent clicks exhibited increases in latency, peak latency, response duration, and post-onset suppression under anesthesia. Ketamine anesthetic reduced the maximum rate at which multi-unit clusters entrained to repeated clicks. No multi-unit clusters entrained to stimulus presentation rates greater than 33 Hz under anesthesia, compared with 85% and 81% in the pre- and post-anesthetic condition, respectively. Anesthesia also induced oscillatory activity that was not present in awake subjects. Finally, ketamine anesthesia abolished all tonic excitatory and suppressive nonsynchronous responses to click trains. The results of this study suggest that ketamine-based anesthesia significantly alters neural coding of broadband click trains in auditory cortex.

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Available from: Sara E Anderson, Jan 13, 2014
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    • "Apart from its amplitude effects, ketamine robustly suppressed and delayed the latency of ERPs, especially at the first time point (~10 min post-injection), suggesting a relative slowing of signal processing and delay in peak synchrony of the neural oscillators generating the ERP response. Ketamine-induced slowing of ERPs has been reported both in clinical (30, 83) as well as in experimental subjects previously (56, 84, 85). Apart from its effects on N1 amplitude and latency, Ketamine impacted other ERP components as well. "
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    • "The auditory cortex is known to be highly sensitive to preceding activity, with periods of synchronized states exhibiting larger, lower frequency waves (Harris et al. 2011). Strong oscillatory responses have also been observed in ketamine-anesthetized preparations (Eggermont 1992; Kisley and Gerstein 1999; Rennaker et al. 2007) and are strongest in medium anesthesia depths (Kisley and Gerstein 1999). To reduce variability in the LFP area calculation, we removed trials that exhibited large sporadic activity preceding our stimulus-driven activity. "
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