Activation in ventro-lateral prefrontal cortex during the act of tasting: an fNIRS study

The act of tasting is the product of inseparable integrative behavior consisting of multi-sensory processing and orolingual motor coordination. Often tasting-induced brain activity is looked at in a reductionist manner as a set of isolated components. However, brain activity as a whole during tasting may not simply be the sum of isolated brain responses; therefore, attempting to look at the cortical activation in a more holistic manner is important. Using functional near-infrared spectroscopy (fNIRS), we assessed cortical responses during tasting, contrasting observed neuronal activation of the lateral prefrontal cortex (LPFC), of 19 healthy participants before and during tasting of 8ml of sweet-based solutions. To examine the activated brain structure, we estimated the anatomical regions of the measured location in standard brain space. We also included simple tongue tapping movement (TT) and word fluency (WF) tasks as comparative functional markers. Significant activity was found in channels (CHs) estimated to be in the bilateral oral motor areas during the TT task, and those in the LPFC, primarily in the left hemisphere, during the WF task. During the tasting task, significant activation was observed in CHs estimated to lie in the ventral part of pre- and post-central gyri as well as in the ventro-LPFC (VLPFC). The activated regions partly overlapped with those detected during TT or WF tasks, but extended more anteriorly and ventrally. Our study suggests that, in addition to tongue motor areas, the VLPFC is involved in the act of tasting.