Background: The orienting reflex (OR) is a fundamental biological mechanism thought to reflect automatic adaptive processing of environmental stimuli necessary for successful interaction with the environment. It has been hypothesized that the OR is generated in response to novelty such as in the case where a mismatch results between an internal neuronal template stored in working memory and incoming stimuli. Recent blood oxygenated level dependant (BOLD) activation studies that have investigated networks involved in the processing of novelty have suggested the recruitment of a distributed limbic-neocortical network. In the present study, event-related functional resonance imaging with simultaneous autonomic electrodermal activity was used to detect single trials of an auditory oddball task associated with the OR.
Results: The pattern of activations indicated two distinct, but partially overlapping, networks. Predominantly, frontal activations were seen for the target stimuli that did elicit an OR, including the orbitofrontal gyrus and anterior cingulate gyrus, as well as activations in the anterior thalamus and cerebellum. On contrary, parietal activations including the supramarginal gyrus and precuneus were seen for the target stimuli that that did not elicit an OR.