Chunk #123 — 5. Implications for understanding gene-brain-behavior relationships in health and disease — 5.2. An example: P3 as intermediate phenotype for externalizing disorders
However, exact neurocognitive mechanisms by which the reduction of P3 amplitude contributes to the risk for externalizing spectrum behaviors remains unclear. One possible interpretation based on the evidence that electrocortical positivity is associated with inhibitory regulation of cortical excitability (Birbaumer et al., 1990), is that reduced P3 reflects a tonic elevation of cortical excitability, with the latter being a risk factor for poor inhibitory control of behavior (Anokhin et al., 1999b; Begleiter and Porjesz, 1999). However, this cortical disinhibition hypothesis does not seem to be in good agreement with the widely accepted notion that dysregulated behaviors result from poor cortical control over subcortically generated drives and impulses. According to this model, a deficit, rather than excess, of cortical activation would be a risk factor for externalizing behaviors. Apart from oddball tasks, P3 potentials are elicited across a variety of other cognitive tasks by goal-relevant stimuli that require some sort of decision making and response. On the other hand, meta-analysis of functional neuroimaging studies indicated that diverse executive functions tend to engage a very similar set of brain regions, suggesting the
