Meta analysis of neuroimaging studies demonstrate increased thalamic activity, and bilaterally reduced inferior frontal gyrus activation. Activity in the amygdala and other subcortical structures such as the ventral striatum tend to be increased, although results are inconsistent and likely dependent upon task characteristics such as valence. Reduced functional connectivity between the ventral prefrontal cortex and amygdala along with variable findings supports a hypothesis of general dysregulation of subcortical structures by the prefrontal cortex. A bias towards positively valenced stimuli, and increased responsiveness in reward circuitry may predispose towards mania. Mania tends to be associated with right hemisphere lesions, while depression tends to be associated with left hemisphere lesions.