The neural representation of sensorimotor transformations in a human perceptual decision making network

Abstract

Humans can quickly engage a neural network to transform complex visual stimuli into a motor response. Activity from a key region within this network, the intraparietal sulcus (IPS), has been associated with evidence accumulation and motor planning, thus implicating it in sensorimotor transformations. If such transformations occur within a brain region, a key and untested prediction is that neural activity reflecting both the parametric amount of evidence available and the timing of motor planning can be independently manipulated. To investigate these ideas, we constructed a dot motion discrimination task in which information about response modality (what to use) and response mapping (how to use it) was provided independently either before or after presentation of a dot motion coherence stimulus whose strength varied across trials. Consistent with our hypothesis, activity within IPS covaried with dot motion coherence during the stimulus phase, and as information necessary for the response was delayed, the peak of IPS activity shifted to the response phase. In contrast, areas such as the motion-sensitive region MT+ and the supplementary motor area demonstrated activity limited to the stimulus and response phases of the task, respectively. These results show that activity in IPS correlates with temporally dissociable representations consistent with both evidence accumulation and motor planning, and suggest that IPS is a core component for sensorimotor transformations within the perceptual decision-making network.© 2013 Elsevier Inc. All rights reserved. IntroductionThe ability to link sensation with action is integral to even the most fundamental of decisions. In humans, a number of studies have identified a frontoparietal network involved in processes during perceptual decisions, including sensory processing, attentional control, evidence accumulation, and motor planning (Heekeren et al., 2008; Kayser et al., 2010a,b;Liu and Pleskac, 2011;Ploran et al., 2007Ploran et al., , 2011Rowe et al., 2010;Ho et al., 2009;Tosoni et al., 2008). Previously we demonstrated that for subjects performing a dot motion discrimination task, this network displays a blood oxygen level-dependent (BOLD) response that varies inversely with motion coherence (Kayser et al., 2010a). Consistent with previous and subsequent findings (e.g., Hebart et al., 2012;Ho et al., 2009;Kayser et al., 2010b), this negative parametric effect matched predictions of a proportional-rate diffusion model for evidence accumulation to a threshold (Palmer et al., 2005;Ratcliff and McKoon, 2008), and linked human brain activity with a computational model of the transformation from stimulus to response.Although this parametric effect is necessary, it is not sufficient to define regions that support such sensorimotor transformations. Human studies, for example, show that areas such as the motion-sensitive region MT+, supplementary motor area (SMA), and intraparietal sulcus (IPS) all display this parametric effect. Importantly, results from macaque studies show that ...

Decision and action planning signals in human posterior parietal cortex during delayed perceptual choices

“…In human observers, mechanisms of perceptual decision‐making have been investigated in several studies using functional magnetic resonance imaging (fMRI) and electroencephalography/magnetoencephalography methods (Heekeren et al ., ; Philiastides & Sajda, ; Ploran et al ., ; Tosoni et al ., ; Donner et al ., ; Ho et al ., ; Kayser et al ., ; Liu & Pleskac, ; Gould et al ., ; Hebart et al ., ; O'Connell et al ., ; Wyart et al ., ; Erickson & Kayser, ; Filimon et al ., ). Several studies have focused on the issue of whether perceptual decisions rely on response‐related mechanisms or are mediated by high‐level mechanisms independent of the motor response (Heekeren et al ., ; Ho et al ., ; Liu & Pleskac, ; Hebart et al ., ; O'Connell et al ., ; Filimon et al ., ).…”

“…Several studies have focused on the issue of whether perceptual decisions rely on response‐related mechanisms or are mediated by high‐level mechanisms independent of the motor response (Heekeren et al ., ; Ho et al ., ; Liu & Pleskac, ; Hebart et al ., ; O'Connell et al ., ; Filimon et al ., ). Some evidence (Tosoni et al ., ; Donner et al ., ; Gould et al ., ; Erickson & Kayser, ) indicates that perceptual decision‐related signals occur in regions involved in planning and executing actions consistently with the intentional framework, but the slow temporal resolution of the blood‐oxygenation‐level‐dependent (BOLD) signal has prevented a clear separation of decision from motor planning signals.…”

Imaging decision-related neural cascades in the human brain

“…On any given trial, the level of noise, or stimulus evidence, was varied randomly. The task itself, as well as similar visual decision-making tasks 28 , is believed to engage an extensive set of cortical areas in a coordinated fashion, including regions that are responsible for sensory encoding, evidence accumulation, decision formation, and response and decision monitoring. However, the dynamic interplay of these regions has never been observed in humans.…”

Computational modelling: moonlighting on the neuroscience and medicine

“…Using a mathematical framework, it has been demonstrated that the anterior areas of prefrontal cortex are involved in making more complex decisions (24). An attempt for modeling the human cognitive procedures has been recently made through the simulated processes like acquired rule-based systems or manipulation of visual representations in decision-making (25). Computational modeling of cognitive functions has revealed that information from multiple sensory modalities are integrated in the frontal and parietal lobes of the brain (26,27).…”