Neural activity in SII modifies sensory evoked potentials in SI in awake rats

THE function of the projection from the secondary somatosensory cortex (SII ) to the primary somatosensory cortex (SI) in rats was investigated by reco rding sensory evoked potentials (SEP) in SI during glutamate activation and lidocaine blockade of SII. In anesthetized animals, glutamate stimulation of SII decreased SEP latency and increased SEP amplitude, whereas no change s were evident during lidocaine blockade of SII. In awake animals, a second , later component of the SEP appeared. This second component was almost com pletely eliminated during lidocaine blockade of SII. We conclude that the p rojection from SII to SI in rats slightly facilitates the SEP response in a nesthetized animals and is responsible for a major portion of the late comp onent of the SEP in awake animals. (C) 1998 Lippincott Williams & Wilkins.