Imaging Risk-taking in Attention-deficit Hyperactivity Disorder

Abstract:
To compare the pattern of brain activation during the performance of a Risk-Taking task (Bechara et al., 1994) in individuals with Attention-Deficit Hyperactivity (ADHD; n=5, 32.6 ± 6.8 y) and healthy controls (n=18, 30.2 ± 6.6 y), we measured regional cerebral blood flow (rCBF) using positron emission tomography with H215O. The Risk-Taking task is a test of decision-making based on the weighing of reward and penalty. Deficits in behavioral inhibition, characteristic of ADHD, have been associated with dysfunction of the orbitofrontal cortex, whose functional integrity is required for normal performance on the task. Mean performance on the task did not differ between ADHD (net-score -2.8 ± 25.3) and control (net-score 9.3 ± 27.6) subjects. Both control and ADHD groups showed activations (peak P<0.001) in the orbitofrontal cortex bilaterally, dorsolateral prefrontal cortex primarily right, and cerebellum. Whereas controls showed activations in insula bilaterally, right thalamus, and right superior parietal cortex, ADHD subjects showed activations in left hippocampus and right uncus. Decision-making recruited similar key structures (prefrontal cortex) in both control and ADHD subjects. However, the task activated areas that code predominantly somatosensory attributes of stimuli in the control group, and areas that subserve mood and memory in the ADHD group. Despite the small size of the ADHD group, these findings may reflect important abnormalities in the network that mediates decision-making responsible for part of the maladaptive behavior typical of ADHD.