Serotonin Transporter Genetic Variation and the Response of the Human Amygdala
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Hidalgo R. B., Davidson J. R., J. Clin. Psychiatry 61, S7:5 (2000).
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Twenty-eight right-handed healthy subjects (20 females and 8 males) participated in the study according to the guidelines of the National Institute of Mental Health Institutional Review Board. All subjects were screened for and cleared of neurological psychiatric or substance-abuse problems and had no history of other medical problems or medical treatment relevant to cerebral metabolism and blood flow.
Materials and methods are available as supporting material on Science Online.
In both cohorts the two genotype groups were matched for gender (first and second cohort: 5 females and 2 males in each group) age [first cohort: mean ± SEM s group = 27.4 ± 5.6 years and l group = 32.1 ± 3.8 years; F (1 12) = 3.35 P = 0.09; second cohort: s group = 32.7 ± 4.9 years and l group = 32.7 ± 3.8 years; F (1 12) = 0.12 P = 0.73] and mean IQ [first cohort: mean ± SEM s group = 106.9 ± 9.8 and l group = 110.3 ± 6.2; F (1 12) = 0.61 P = 0.45; second cohort: s group = 106.1 ± 4.8 and l group = 96.9 ± 3.9; F (1 12) = 2.25 P = 0.16]. In the first cohort there were 12 Caucasians and 2 African Americans (both female l/l homozygotes) and in the second there were 13 Caucasians and 1 African American (female l/l homozygote).
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A. R. Hariri et al. Neuropsychopharmacology in press.
All subjects completed a version of the “ n -back” working memory task known to engage the dorsolateral prefrontal cortex and a network of related cortical regions (40). In this task subjects are required to remember the sequence of serially presented numbers in order to identify numbers that appeared “ n -back” (i.e. 1-back 2-back 3-back). There were no significant group differences in performance (accuracy or reaction time) on this task. Analysis of the imaging data (22) revealed no significant differences in any brain regions including the dorsolateral prefrontal cortex between the s and l groups.
Analysis of variance of performance measures on the emotion task revealed no significant group differences in either cohort for mean accuracy [first cohort: % correct ± SEM s group = 93.1 ± 7.0 and l group = 86.1 ± 4.5; F (1 12) = 0.69 P = 0.43; second cohort: s group = 96.4 ± 1.7 and l group = 98.8 ± 1.2; F (1 12) = 1.33 P = 0.27] or mean reaction time [first cohort: ms ± SEM s group = 2274.1 ± 120.8 and l group = 2367.8 ± 108.7; F (1 12) = 0.33 P = 0.58; second cohort: s group = 1761.5 ± 132.6 and l group = 1941.3 ± 159.6; F (1 12) = 0.75 P = 0.40].
Analysis of variance of total scores from the Harm Avoidance subset of the Tridimensional Personality Questionnaire (41) designed to represent behaviors such as fear and anxiety influenced by serotonergic neurotransmission revealed no significant group differences in either the first [mean ± SEM s group = 8.7 ± 2.0 and l group = 9.9 ± 1.1; F (1 12) = 0.24 P = 0.63] or second [mean ± SEM s group = 10.4 ± 1.6 and l group = 10.0 ± 2.3; F (1 12) = 0.02 P = 0.88] cohort. It should be noted however that the Tridimensional Personality Questionnaire has not been as robust as other measures (i.e. NEO personality inventory) in identifying genotype effects on fear and anxiety (3) and that the use of more robust measures in the current study may have revealed group differences in these behaviors.
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We thank S. Das S. Lee E. O'Hare W. G. Smith and R. Vakkalanka for technical assistance. Supporting Online Material www.sciencemag.org/cgi/content/full/297/5580/400/DC1 Materials and Methods