Abstract
Anesthesia affects cortical response properties and induces changes in functional network connectivity. Many studies in sensory neurophysiology do not explicitly differentiate between anesthetic states and possibly underestimate the effect of anesthetic level on cortical response properties. To investigate this question, we performed simultaneous multisite recordings in V1 of C57bl/6 mice under continuously changing inspiratory isoflurane concentration from low to high dosage. During the continuous change of anesthesia level we presented visual and auditory stimuli. At all levels of anesthesia, visual stimulation evoked responses in V1. However, during light anesthesia auditory stimulation slightly suppressed ongoing LFP activity in V1. With increasing anesthesia levels this suppression vanished, and at a specific point a discrete change in sensory responsiveness of V1 to auditory stimulation appeared. At this discrete point auditory suppression was reversed into auditory induced activation of V1. This transition in properties was coincident with the appearance of burst-suppression. The responses during burst suppression state had long latency and resembled spontaneous bursts. This presumably unspecific auditory effect in V1 disappeared as soon as isoflurane concentration level dropped below a certain level. The results demonstrate that in the extreme case heteromodal effects can be induced by varying anesthesia level.