Abstract
A fundamental problem in understanding the human brain in general, or specifically the visual system, is determining to what extent the brains of different individuals behave alike. Here we compare two different aspects of brain function: task activation strength and the relation between task activation and behavior. Human subjects (N=50) perform an average of 750 trials each on a perceptual task with confidence inside an MRI scanner. For each subject, voxel activation strength is estimated from blocks of 8 trials. To determine how similar changes in brain activity are among individuals in response to task demands, we correlated the activity maps among individuals. We find that a task generates similar activation patterns among people (r = 0.38 0.17). We determined if the same relation among individuals exists when comparing task activation and behavior. First, we correlated the average reaction time from the block of 8 trials with activation producing a subject specific activity-reaction time map. The activity-reaction time map indexes how activation strength relates to behavioral performance within an individual. To determine how similar the activity-reaction time maps are among individuals, we correlated the activity-reaction time maps were correlated among individuals. Immense differences among individuals emerge in how task activation relates to behavioral outcome (r = 0.01 0.02). Additionally, we found similar results we compared the similarity between activation-confidence maps (r = 0.005 0.1) and activation-accuracy maps between individuals (r = 0.002 0.01). Furthermore, the results for activation strength and activation-behavior can be explained by a single computational model that jointly generates brain activity and behavior. These findings demonstrate that unlike global brain structure and function that are shared among people, the relation between brain activity and behavioral outcomes is largely idiosyncratic during a perceptual task.