Meta-analytic clustering dissociates brain activity and behavior profiles across reward processing paradigms

Description: We employed a data-driven, meta-analytic clustering approach to an extensive body of reward processing neuroimaging results archived in the BrainMap database (www.brainmap.org) to characterize meta-analytic groupings (MAGs) of reward processing experiments based on the spatial similarity of brain activation patterns. Using a data-driven, meta-analytic, k-means clustering approach, we dissociated five meta-analytic groupings (MAGs) of neuroimaging results (i.e., brain activation maps) from 749 experimental contrasts across 177 reward processing studies involving 13,345 healthy participants. We objectively identified a five-MAG solution which represented dissociated patterns of activation consistently occurring across reward processing tasks (MAG-1: ventral-striatal; MAG-2: dorsal-striatal; MAG-3: limbic-parietal; MAG-4: frontal-parietal; MAG-5: medial frontal-posterior cingulate). The optimal clustering-solution was selected based on majority rule of four information-theoretic metrics and, subsequently, convergent brain activity across each grouping of neuroimaging experiments was quantified via separate meta-analyses. To compile a large corpus of neuroimaging results across reward processing paradigms, we extracted activation coordinates reported in published studies that were archived in the BrainMap Database as of April 22, 2016, under the meta-data labels Reward, Delay Discounting, and Gambling (www.brainmap.org) (Fox et al., 2005; Fox & Lancaster, 2002; Laird et al., 2011). The vast majority (94.9%) of identified studies were archived under the Reward label with most Delay Discounting and Gambling studies being additionally archived under Reward. The Reward label denotes that the reported activation coordinates were identified in a task where a stimulus served to reinforce a desired response (e.g., monetary reward after a correct response) (www.brainmap.org/taxonomy/paradigms). Almost all studies included in the corpus were also archived under a variety of other meta-data labels (e.g. Task Switching (6.4%), Go/No-Go (2.9%), Visuospatial Attention (2.9%), Reasoning/Problem Solving (1.3%), Wisconsin Card Sorting Test (2.6%)) which is unsurprising as reward processing is a multifaceted construct, connecting elements of sensation, perception, cognitive control, and other mental operations. We considered only activation coordinates from published neuroimaging studies, among healthy participants, that were reported in standard Talairach (Talairach & Tournoux, 1988) or Montreal Neurological Institute (MNI) (Collins, 1994) space and derived from whole-brain statistical comparisons. Brain coordinates derived through behavioral correlations or a priori region of interest (ROI) analyses were excluded. As this meta-analysis aimed to investigate brain activation linked with typical reward processing, coordinates from groups of individuals with psychological or neuropsychiatric disorders (e.g., addictive disorders) were excluded from the corpus. Each included study provided at least one experimental contrast that statistically identified brain activity associated with a certain task-event defined by the original authors (e.g., a brain activity map). These experimental contrasts were summarized and curated in the BrainMap database as a set of brain activity foci linked either with phases of the original task (i.e., task response, anticipation of outcome, outcome delivery) or stimuli presented in the task (i.e., positive outcome, negative outcome, high reward, low reward). Foci from experimental contrasts can also reflect locations of brain activity linked with more abstract and computationally derived constructs of interest in the original study (e.g., learning rate, subjective value).