Cortical correlates of perceptual decision making during tactile spatial pattern discrimination

Abstract

Perceptual decision making involves a distributed cortical network including areas related to sensory feature extraction, decision formation, and finally signalling the decision through a motor response. Although these processing steps are supposed to occur in sequence, the seemingly instant mapping of a perceptual decision onto a motor response renders these processes almost indistinguishable. To dissociate cortical areas related to sensory decision making from areas that prepare the subsequent motor response, we performed functional magnetic resonance imaging during a tactile spatial pattern discrimination task with interleaved immediate and delayed response conditions. Decision difficulty was manipulated parametrically by adding spatial noise to the tactile patterns, resulting in a rise in decision time with increasing noise. We assumed that areas involved in making the decision should show a variation in their activation with decision time and irrespective of whether (immediate response condition) or not (delayed response condition) a motor response could be prepared in advance. To exhibit these putative decision areas, we used response time, as was obtained in the immediate response condition, as parametric predictor for the difficulty-dependent variations of blood oxygenation level-dependent (BOLD)-activity in both response conditions. BOLD activations in right (contralateral) postcentral sulcus, right intraparietal sulcus (IPS) and bilateral anterior insula (aINS) reflected this parametric modulation in both response conditions, suggesting a role of these areas in tactile decisions independent of decision-specific motor preparation. Furthermore, a multivariate pattern analysis performed on the BOLD responses in the delayed response condition for a single difficulty level independently validated IPS and aINS as decision-related areas. Hum Brain Mapp 36:3339-3350, 2015.V C 2015 Wiley Periodicals, Inc.

A somatosensory‐to‐motor cascade of cortical areas engaged in perceptual decision making during tactile pattern discrimination

“…The resulting time differences described a continuum that ranged from zero time difference, indicative for areas that process information related to the sensory input and, thus, are invariant to the response delay instruction, to time differences corresponding to the delayed response onset, thus indicating motor‐related processing. Taken together with our previous findings (Li Hegner et al []: Hum Brain Mapp 36:3339–3350), our results suggest that the anterior insula reflects the ultimate perceptual stage within the uncovered sensory‐to‐motor gradient, likely translating sensory information into a categorical abstract (non‐motor) decision. Hum Brain Mapp 38:1172–1181, 2017 .…”

“…Similar to the animal work reported above, previous human fMRI studies have also revealed a fronto‐parietal decision network, emphasizing the role of intraparietal sulcus (IPS) [Kayser et al, ], inferior frontal cortex [Filimon et al, ] and anterior insula [aINS, Binder et al, ; Ho et al, ; Li Hegner et al, ; Liu and Pleskac, ] in perceptual decision making. Converging evidence from these previous studies [Binder et al, ; Ho et al, ; Li Hegner et al, ; Liu and Pleskac, ] further highlights the aINS as a domain‐general perceptual decision area that reflects categorical perceptual decisions, irrespective of the modality of either motor response or sensory input. Yet, it still remains a challenge to detail these (and other) areas' “position” in a sensory‐to‐motor functional hierarchy within the set of areas contributing to perceptual decisions.…”

“…Yet, it still remains a challenge to detail these (and other) areas' “position” in a sensory‐to‐motor functional hierarchy within the set of areas contributing to perceptual decisions. This shall be exemplified by a human fMRI study of our group, in which we uncovered a distributed set of cortical areas contributing to perceptual decision making during tactile spatial pattern discrimination [Li Hegner et al, ]. In brief, in this study we exhibited multiple task‐related areas in which fMRI activity was positively correlated with decision difficulty and subjects' reaction times.…”

“…The presence of decision‐related activity in the latter two areas was further confirmed by our ability to successfully decode subjects' perceptual decision within trials of identical difficulty using multivariate pattern analysis. On the one hand, our approach allowed us to highlight the aINS and the IPS as decision areas, while their activity could not be explained by differences in sensory input or motor output [Li Hegner et al, ]. On the other hand, our previous analysis could not detail whether processing in these and other decision‐related brain areas relates to the sensory input they require or to the motor response, which they ultimately cause.…”

Decoding vibrotactile choice independent of stimulus order and saccade selection during sequential comparisons

“…A significant portion of decision-related signals in the FEF or LIP disappeared when saccade directions were decorrelated from perceptual choices (Bennur & Gold, 2011;Gold & Shadlen, 2003; reviewed in Huk et al, 2017). Similarly, recent human fMRI studies also failed to capture decision-related signals in the FEF or IPS when there was no fixed mapping between choice and saccade direction (Filimon et al, 2013;Hebart et al, 2012;Li Hegner, Lindner, & Braun, 2015). From these results one might conclude that oculomotor regions may merely represent the motor decisions.…”