SOMATOSENSORY SYSTEMS, PAINShort-latency afferent inhibition varies with cortical state in rat somatosensory cortexFunke, Klaus; Benali, AliaAuthor Information Department of Neurophysiology, Medical Faculty, Ruhr-University Bochum, Universitaetsstrasse, Bochum, Germany Correspondence to Dr Klaus Funke, Department of Neurophysiology, Ruhr-Universitaet Bochum, Universitaetsstrasse 150, Bochum D-44780, Germany Tel: +49 234 3223944; fax: +49 234 3214192; e-mail: firstname.lastname@example.org Received 13 May 2009 accepted 24 May 2009 NeuroReport: October 7th, 2009 - Volume 20 - Issue 15 - p 1313-1318 doi: 10.1097/WNR.0b013e32832e9b3b Buy Metrics Abstract Short-latency afferent inhibition (SAI) can be used to demonstrate experimentally induced or pathological changes in cortical excitability. By recording somatosensory-evoked potentials from rat somatosensory cortex (S1), we can show that SAI further varies with the state of the cortex as deduced from the spectral composition of the electroencephalogram. SAI is strongly increased during episodes of enhanced δ-activity. The amplitude ratio of second /first somatosensory-evoked potential is significantly correlated to the ratio of θ/δ band power, but also depends on the power of higher-frequency bands. We conclude that evoked cortical inhibition is not a constant entity, but varies with the physiological state of the cortical network controlled by the brainstem arousal system. © 2009 Lippincott Williams & Wilkins, Inc.