The neurodevelopmental frontostriatal disorders: Evolutionary adaptivenessand anomalous lateralization

The: frontostriatal system (dorsolateral prefrontal cortex, lateral orbitof rontal cortex, anterior cingulate,supplementary motor area, and associated basal-ganglia structures) is subject to a range of neurodevelopmental disor ders: Tourette's syndrome (TS), obsessive compulsive disorder (OCD), attent ion deficit hyperactivity disorder (ADHD), schizophrenia (SCZ), autism, and probably depression. The system is responsible for our adaptive responses (initiation, execution, or withholding) to environmental situations, and th e above disorders, involving effectively excessive release ol withholding o f various types of response, are all a consequence of changes in specific f rontostriatal regions. The disorders all have a genetic component, and thei r persistence in the genome indicates that their clinical manifestations ma y also he associated, perhaps in low levels in close relatives, with certai n adaptive advantages in given situations. Thus autism is associated with c omputational careers, depression with literary creativity, SCZ with lateral thinking and the Odyssean personality, ADHD with an lee-Age readiness to r espond, OCD with a focused range of interests, and TS with competitive spor ts and jazz improvisation. The disorders are all highly cumorbid, and which one predominantly manifests may depend on how the frontostriatal system ha ppens to he compromised as a result of inherited genetic predispositions an d environmental contingency. We review the adaptive nature of the various s ubclinical manifestations and the evidence for concomitant phenomena (possi bly epiphenomena): alterations in structural, functional, and behavioral la teralization in each syndrome. Indeed it is not clear that altered laterali zation in frontostriatal disorders of a neurodevelopmental origin generally has any adaptive significance; it may often simply serve as a marker for a ltered regulatory function of the frontostriatal system, alterations which in low genetic dosage or penetrance continue to play an adoptive role in cl inically unaffected close relatives of probands, hut which, in high dosage or penetrance in the probands themselves, are generally deleterious. (C) 20 00 Academic Press.