Journal
HUMAN BRAIN MAPPING
Volume 35, Issue 7, Pages 2935-2949Publisher
WILEY
DOI: 10.1002/hbm.22375
Keywords
semantic processing; propofol; inferior frontal gyrus; sedation; functional MRI
Funding
- Wellcome Trust [083660/Z/07/Z]
- Raymond and Beverly Sackler Studentship
- Stephen Erskine Fellowship, Queens' College Cambridge
- UK Medical Research Council [MC_US_A060_0038]
- British Oxygen Professorship of the Royal College of Anaesthetists
- MRC [MC_U105580446] Funding Source: UKRI
- Medical Research Council [G0001354, G1000183B, MC_U105580446, G0001354B] Funding Source: researchfish
- National Institute for Health Research [NF-SI-0512-10090] Funding Source: researchfish
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Sedation has a graded effect on brain responses to auditory stimuli: perceptual processing persists at sedation levels that attenuate more complex processing. We used fMRI in healthy volunteers sedated with propofol to assess changes in neural responses to spoken stimuli. Volunteers were scanned awake, sedated, and during recovery, while making perceptual or semantic decisions about nonspeech sounds or spoken words respectively. Sedation caused increased error rates and response times, and differentially affected responses to words in the left inferior frontal gyrus (LIFG) and the left inferior temporal gyrus (LITG). Activity in LIFG regions putatively associated with semantic processing, was significantly reduced by sedation despite sedated volunteers continuing to make accurate semantic decisions. Instead, LITG activity was preserved for words greater than nonspeech sounds and may therefore be associated with persistent semantic processing during the deepest levels of sedation. These results suggest functionally distinct contributions of frontal and temporal regions to semantic decision making. These results have implications for functional imaging studies of language, for understanding mechanisms of impaired speech comprehension in postoperative patients with residual levels of anesthetic, and may contribute to the development of frameworks against which EEG based monitors could be calibrated to detect awareness under anesthesia. Hum Brain Mapp 35:2935-2949, 2014. (c) 2013 Wiley Periodicals, Inc.
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