Conditioning-induced changes in sensory cortical maps detected in mice by intrinsic signal optical imaging

Abstract

Intrinsic signal optical imaging (ISOI) has been used previously for the detection of changes in sensory processing in the somatosensory cortex in response to environment alteration or after deprivation of sensory information. To date, there have been no reports of ISOI being used in learning-induced changes in the somatosensory cortex. In the present study, ISOI was performed twice in the same mouse: before and after conditional fear learning. The conditioning paradigm consisted of pairing sensory stimulation of vibrissae with electric tail shock. In order to map the cortical representation of the vibrissa B1 with ISOI, we deflected the vibrissa with an intensive stimulation (frequency of 10 Hz for 6 s). After conditioning, we found that the cortical representation of vibrissa B1 had expanded by an average of 44%, compared with pre-learning, by using images obtained with ISOI. Previously, we demonstrated an enlargement of the cortical representation of the vibrissae stimulated by the same behavioral training paradigm but using [14C]2-deoxyglucose. This current investigation provides the first ISOI-based evidence of learning-induced changes in plasticity in the barrel cortex. The results indicate that irrespective of physiological mechanisms used for visualization of the vibrissae representation or subject�s testing state (aware or anesthetized animal), the conditioning induced changes in each case in the cortical processing of intensive stimuli. This suggests specific functional reorganization of the neuronal circuits. Moreover, ISOI as a noninvasive method of mapping cortical activation in the same animal before and after behavioral training could serve as a very useful tool for precise manipulation within the cortex and for assessing the resulting effects on experience-dependent cortical plasticity.