Striatal dopamine transporters and cognitive functioning in healthy men and women.
OBJECTIVE: There is growing interest in distinguishing the biological bases of sex differences in behavior from environmental influences. Sex hormone levels seem to be related to some cognitive abilities, particularly memory, and the dopaminergic system participates in the mediation of memory. The dopamine transporter is the primary indicator of dopaminergic tone. This study investigated the relationship between cognition and dopamine transporter availability in healthy men and women. METHOD: Dopamine transporter levels were measured with a technetium-99m radiolabeled analog of cocaine, TRODAT-1, in 66 healthy volunteers (30 men and 36 women). A neuropsychological battery designed to target functions associated with dopaminergic activity was administered during the uptake interval between the radiopharmaceutical injection and image acquisition. RESULTS: Women and younger participants had higher dopamine availability in the caudate nucleus, and these groups also performed better on verbal learning tasks. Furthermore, dopamine transporter availability was correlated with learning performance within groups. Relationships between dopamine availability in the caudate and putamen and executive and motor functioning were observed in women, but not in men. CONCLUSIONS: The results provide further evidence for age effects and sex differences in the neuromodulatory influences of dopamine on behavior in humans.