Audiovisual Events in Sensory Memory

The functional properties of the auditory sensory memory have been extensively studied using the mismatch negativity (MMN) component of the auditory event-related potential (ERP) and its magnetic counterpart recorded using magneto-encephalography (MEG). It has been found that distinct auditory features (such as frequency or intensity) are encoded separately in sensory memory. Nevertheless, the conjunction of these features (auditory “gestalts”) can also be encoded in auditory sensory memory. Here we investigated how auditory and visual features of bimodal events are represented in sensory memory by recording audiovisual MMNs in two different audiovisual oddball paradigms. The results of a first ERP experiment showed that the sensory memory representations of auditory and visual features of audiovisual events lie within the temporal and occipital cortex, respectively, yet with possible interactions between the processing of the unimodal features. In a subsequent MEG experiment, we found some evidence that audiovisual feature conjunctions could also be represented in sensory memory. These results, thus, extend to the audiovisual domain a number of properties of sensory memory already established within the auditory system.