Human and animal neurophysiological studies have shown that the auditory and tactile systems interact both early in time, and early in the cortical processing hierarchy. The question remains as to the functional significance of these multisensory interactions that are observed prior to 100 ms post-stimulus onset in both auditory and tactile cortices. We sought to test the hypothesis that this cross-talk occurs during preattentive sensory processing. The mismatch negativity (MMN), an electrophysiological response associated with the pre-attentive detection of a change within the context of a regular pattern of stimulation, served as the dependent measure. High-density electrophysiological recordings were made in healthy adults who viewed a silent movie while they were presented a stream of blocked tactile, auditory or audio-tactile stimuli consisting of frequent and infrequent stimuli. The mismatch waveforms were calculated by subtracting the frequent from the infrequent evoked potential. In Experiment 1 and 2, we investigated the cross sensory interactions to duration and frequency change, respectively. For both experiments we measure tactile, auditory and audio-tactile MMN. The scalp data showed fronto-central negative topographies for both the frequency and duration multisensory MMNs, which is typical of auditory alone mismatches. Cross-sensory interactions between the sensory channels were assessed by testing for non-linearity of the multisensory MMNs when compared to the sum of the unisensory MMNs. In the duration change paradigm the multisensory mismatch showed no cross sensory interaction between audition and touch, suggesting that duration is processed in sensory specific cortices. In contrast, in the frequency change paradigm the multisensory mismatch exhibited non-linear interactions beginning at ~180ms, and was consistent with preattentive cross-talk among the tactile and auditory temporal frequency processing streams. Our results suggest that different networks might underlie the processing of duration whereas there is cross-sensory interaction at the sensory perceptual level of audition and tactile for frequency processing.

Auditory-Somatosensory; EEG