RT Journal Article SR Electronic T1 As soon as you taste it – evidence for sequential and parallel processing of gustatory information JF eneuro JO eNeuro FD Society for Neuroscience SP ENEURO.0269-18.2018 DO 10.1523/ENEURO.0269-18.2018 A1 Raphael Wallroth A1 Kathrin Ohla YR 2018 UL http://www.eneuro.org/content/early/2018/10/15/ENEURO.0269-18.2018.abstract AB The quick and reliable detection and identification of a tastant in the mouth regulate nutrient uptake and toxin expulsion. Consistent with the pivotal role of the gustatory system, taste category information (e.g. sweet, salty) is represented during the earliest phase of the taste-evoked cortical response (Crouzet et al., 2015) and different tastes are perceived and responded to within only a few hundred milliseconds, in rodents (Perez et al., 2013) and humans (Bujas, 1935). Currently, it is unknown whether taste detection and discrimination are sequential or parallel processes, i.e. whether you know what it is as soon as you taste it. To investigate the sequence of processing steps involved in taste perceptual decisions, participants tasted sour, salty, bitter, and sweet solutions and performed a taste-detection and a taste-discrimination task. We measured response times and 64-channel scalp electrophysiological recordings, and tested the link between the timing of behavioral decisions and the timing of neural taste representations determined with multivariate pattern analyses. Irrespective of taste and task, neural decoding onset and behavioral response times were strongly related, demonstrating that differences between taste judgments are reflected early during chemosensory encoding. Neural and behavioral detection times were faster for the iso-hedonic salty and sour tastes than their discrimination time. No such latency difference was observed for sweet and bitter, which differ hedonically. Together, these results indicate that the human gustatory system detects a taste faster than it discriminates between tastes, yet hedonic computations may run in parallel (Perez et al., 2013) and facilitate taste identification.Significance Statement Human response behavior reflects the culmination of multiple processing stages, so that the emergence of the commonly observed response delay between simple and more complex gustatory perceptual decisions remained unaddressed. For the first time, we show a strong correspondence between neural and behavioral task-dependent latency differences, providing evidence that this lag is represented during early chemosensory encoding, rather than resulting from higher-level cognitive processing. Moreover, we find that the processing sequence itself varies with taste contrast, likely dependent on hedonics. We suggest that taste hedonic features are processed in parallel to purely sensory computations with the potential to facilitate stimulus identification in the human gustatory sense, supporting the concept of a flexible sequence of gustatory coding states.