Dopamine and cognitive functioning: Brain imaging findings in Huntington'sdisease and normal aging

Recent brain imaging studies in Huntington's disease CHD) and normal aging suggest a relationship between central dopaminergic neurotransmission and c ognitive performance. Results demonstrate substantial losses in dopamine (D A) function in both. HD and aging. Moreover, HD patients and older adults s how deficits across multiple cognitive domains, including episodic memory, speed of processing, and executive functioning. Although few studies are av ailable at present, there is converging evidence that multiple measures of pre- and postsynaptic DA biochemistry are (a) highly interrelated, and (b) strongly associated with the cognitive deficits that accompany HD and aging . There is also emerging evidence that DA neurotransmission influences cogn itive performance independent of HD or age. In general, the research review ed in this article indicates that the nigrostriatal DA system is an importa nt component of a frontostriatal circuitry that is critically involved in c ognitive functioning.