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Background: Numerous findings indicate alterations in brain serotonin systems in seasonal affective disorder (SAD). [ 123 I]-2-β-carbomethoxy-3-β-(4-iodophenyl)-tropane ([ 123 I]-β-CIT) labels serotonin transporters (5-HTTs) in the midbrain. We performed a [ 123 I]-β-CIT single photon emission computer tomography (SPECT) study under the hypothesis of lower [ 123 I]-β-CIT binding reflecting reduced central 5-HTT availability in depressed SAD patients. Methods: Depressed SAD patients and healthy control subjects were investigated using [ 123 I]-β-CIT SPECT 4 hours and again 24 hours after tracer injection. Subjects had either never used psychotropic medication or had been drug-free for at least 6 months prior to the investigation. Specific-to-nondisplaceable partition coefficient (V 3 ′′) was calculated for the thalamus-hypothalamus and the midbrain-pons; the cerebellum served as a reference region. Results: Patients showed a reduction in V 3 ′′ in thalamus-hypothalamus (2.41 ± 0.3 vs. 2.84 ± 0.4; p = .026) 24 hours post tracer injection (p.i.). No difference between patients and control subjects was found in midbrain-pons (1.31 ± 0.2 vs. 1.42 ± 0.2; p = .39). No differences were detected in the SPECT acquisitions 4 hours p.i. Conclusions: Depressed SAD patients showed lower specific-to-nondisplaceable [ 123 I]-β-CIT binding in the region of interest (ROI) thalamus-hypothalamus. The small size of the midbrain-pons ROI may have contributed to the failure to show a difference in this ROI as well. Similar to reduced midbrain 5-HTT availability in nonseasonal depression, depression in SAD seems to be associated with reduced 5-HTT availability to the thalamus-hypothalamus.

routine. Total brain volume was significantly reduced in the TBI group (t 5 2.28, df 5 18, p , .04). There was a significant group effect on hippocampal volume (F 5 9.87, df 5 (1,14), p , .007) with bilateral volume reductions in the TBI subjects. Including gender as a second independent variable and covarying for the effect of total brain volume and age did not change the significance of these findings. Additionally, TBI severity (mild vs. moderatesevere) did not predict hippocampal volume. The volumetric MRI findings are consistent with the hypothesis that auditory gating and P50 abnormalities following TBI may be predicated on damage to hippocampal cholinergic systems.