A Cortical Network Sensitive to Stimulus Salience in a Neutral Behavioral Context Across Multiple Sensory Modalities

1 Institute of Medical Science, 2 Department of Medical Imaging, and 3 Department of Surgery, University of Toronto; and 4 Toronto Western Research Institute, Toronto Western Hospital, Toronto, Ontario M5T 2S8, Canada Downar, Jonathan, Adrian P. Crawley, David J. Mikulis, and Karen D. Davis. A Cortical Network Sensitive to Stimulus Salience in a Neutral Behavioral Context Across Multiple Sensory Modalities. J. Neurophysiol. 87: 615-620, 2002. Stimulus salience depends both on behavioral context and on other factors such as novelty and frequency of occurrence. The temporo-parietal junction (TPJ) responds preferentially to behaviorally relevant stimuli and is thought to play a general role in detecting salient stimuli. If so, it should respond preferentially to novel or infrequent events, even in a neutral behavioral context. To test this hypothesis, we used event-related functional magnetic resonance imaging (fMRI) to identify brain regions sensitive to the novelty of visual, auditory, and tactile stimuli during passive observation. Cortical regions with a greater response to novel than familiar stimuli across all modalities were identified at two sites in the TPJ region: the supramarginal gyrus (SMG) and superior temporal gyrus. The right inferior frontal gyrus (IFG), right anterior insula, left anterior cingulate cortex (ACC), and left inferior temporal gyrus also showed sensitivity to novelty. The novelty-sensitive TPJ activation in SMG overlaps a region previously identified as sensitive behavioral context. This region may play a general role in identifying salient stimuli, whether the salience is due to the current behavioral context or not. The IFG activation overlaps regions previously identified as responsive to nonnovel sensory events regardless of behavioral context. The IFG may therefore play a general role in stimulus evaluation rather than a specific role in identifying novel stimuli. The ACC activation lies in a region active during complex response-selection tasks, suggesting a general role in detecting and/or planning responses to salient events. A frontal-parietal-cingulate network may serve to identify and evaluate salient sensory stimuli in general.