Electrical neuroimaging reveals intensity-dependent activation of human cortical gustatory and somatosensory areas by electric taste

To analyze the neural basis of electric taste we performed electrical neuroimaging analyses of event-related potentials (ERPs) recorded while participants received electrical pulses to the tongue. Pulses were presented at individual taste threshold to excite gustatory fibers selectively without concomitant excitation of trigeminal fibers and at high intensity evoking a prickling and, thus, activating trigeminal fibers. Sour, salty and metallic tastes were reported at both intensities while clear prickling was reported at high intensity only. ERPs exhibited augmented amplitudes and shorter latencies for high intensity. First activations of gustatory areas (bilateral anterior insula, medial orbitofrontal cortex) were observed at 70–80 ms. Common somatosensory regions were more strongly, but not exclusively, activated at high intensity. Our data provide a comprehensive view on the dynamics of cortical processing of the gustatory and trigeminal portions of electric taste and suggest that gustatory and trigeminal afferents project to overlapping cortical areas.

Research highlights▶ Electric taste activates the insula as early as 100 ms after stimulus onset. ▶ Overlapping cortical activations represent gustatory and somatosensory sensations. ▶ Both sensations are processed within key areas for gustatory perception. ▶ Activation patterns are vastly dynamic, i.e. changing on a sub-second time-scale. ▶ Gustatory and trigeminal afferents project to overlapping cortical areas.