We found altered amygdala function in females with CAH. However, no difference in amygdala function was observed in males with CAH compared to control males. Amygdala activation in females with CAH was bilaterally higher than amygdala activation in control females, and was similar to amygdala activation in control males, suggesting a virilizing effect. The left amygdala seemed to be more substantially affected, but this laterality effect was not statistically significant.
These findings are partially consistent with previous work in our laboratory that showed reduced amygdala volume in 27 children with CAH (11 females; age 4–16 years) compared to 47 sex- and age-matched healthy controls (Merke et al., 2003
). Although our previous structural study showed a volumetric reduction in the size of the amygdala in patients with CAH independent of sex, it is of interest to note that the effect size (ES) (Cohen 1998
) in girls (ES d′ = 1.56) was almost twice as large as the effect size in boys (ES d′ = 0.91). Our current functional study shows altered amygdala activation in females only.
In the present work, the amygdala function was probed through the now standard way of examining fMRI BOLD signal changes in the amygdala, i.e., during exposure to displays of faces expressing anger or fear vs. neutral expressions (see review, Adolphs 2002
). Behaviorally, the CAH group rated the aversiveness of negative vs. neutral emotions less differently than did the control group, and this effect was mostly related to lower ratings of negative emotions by the CAH group compared to the control group. Moreover, reaction time to negative vs. neutral emotions tended to be shorter in the CAH group compared to the control group, echoing aversiveness ratings. These group differences in performance did not influence the fMRI findings. However, they suggested that patients with CAH may not differentiate aversive from neutral emotions as well as controls. In addition, the diagnosis effect on performance scores was not modulated by sex, suggesting that these performance differences might reflect an alternative (non-androgen) disease-specific effect on neural processes. CAH-related alterations in the HPA axis may play a role, but further studies are needed to explore this possibility.
Previous psychological and behavioral studies of patients with CAH have focused on possible androgen effects on the brain. Compared with their unaffected sisters or control girls, female with CAH have more male-typical childhood play and behavior (Berenbaum1999
; Berenbaum & Snyder 1995
; Dittmann, Kappes, Kappes, Borger, Meyer-Bahlburg, Stegner, Willig, & Wallis 1990
; Hines 2003
; Meyer-Bahlburg, Dolezal, Baker, Carlson, Obeid, & New 2004
; Servin, Nordenstrom, Larsson, & Bohlin 2003
), are more likely to report physical aggression (Berenbaum et al., 1997
) and have better spatial abilities (Hampson, Rovet, & Altmann 1998
; Hines, Fane, Pasterski, Mathews, Conway, & Brook 2003
). The children in our study were not evaluated for male-typical behavior. However, the females with CAH had amygdala activation similar to control males, possibly reflecting an early organizational effect of excess androgen on these brain structures or associated circuits.
The organizational effects of androgen on the development of the brain provide a likely explanation to our findings. The amygdala contains many androgen receptors (DonCarlos, Garcia-Ovejero, Sarkey, Garcia-Segura, & Azcoitia 2003
; Wood 1997
), which have been shown to modulate amygdala size in animals and humans (Goldstein, Seidman, Horton, Makris, Kennedy, Caviness, Jr., Faraone, & Tsuang 2001
). Androgens have also been proposed to influence emotional learning (Vazquez-Pereyra et al., 1995
) through their action on the limbic system (Vazquez-Pereyra et al., 1995
; Naghdi and Asadollahi, 2004
) (Naghdi et al., 2004
; Vazquez-Pereyra et al., 1995
Whereas our main interpretation relies on the neurodevelopmental consequences of elevated androgens, the distinct or interactive contribution of glucocorticoid imbalance cannot be ruled out, particularly based on the role of glucocorticoids on amygdala function. The corticotrophin releasing hormone (CRH), whose expression in the amygdala is stimulated by circulating glucocorticoid (Makino, Gold, & Schulkin 1994
), has been found to play a critical role in the processing of negative emotions, such as aggression, and behavioral responses to stress, particularly fear-related behaviors (LeDoux 2000
). The mechanism underlying glucocorticoid potential influence in our findings is complex. Both early lack of circulating glucocorticoid and later excess of iatrogenic glucocorticoid (Merke, Bornstein, Avila, & Chrousos 2002
) could alter amygdala function. However, glucocorticoid imbalance would not explain the female selectivity of the perturbation observed in the present study because alterations in the HPA axis due to CAH are comparable in both sexes (Merke et al., 2005
). Further functional neuroimaging studies that target processes known to be highly influenced by corticosteroid function, such as memory (Wolf, Kuhlmann, Buss, Hellhammer, & Kirschbaum 2004
) or stress response (de Kloet et al., 2005
), could help to disambiguate the respective role of sex steroids and corticosteroids on amygdala function and associated behavior.
Finally, we present findings of a complementary whole brain analysis. Two findings merit some comments. First, the interaction of Diagnosis-by-Sex contrast showed that the most robust effect laid in the inferior parietal lobule (LPI). The LPI is highly sexually dimorphic (Frederikse, Lu, Aylward, Barta, & Pearlson 1999
), and has been associated with sex differences in visual-spatial abilities (Gron, Wunderlich, Spitzer, Tomczak, & Riepe 2000
). Furthermore, the examination of this interaction using post-hoc analyses indicated that the pattern of activation in girls with CAH was more similar to that of control boys than of control girls, supporting the hypothesis of an early organizational effect of testosterone on brain function in girls with CAH. The second notable finding is the main effect of Diagnosis that is predominant on the fusiform gyrus. This structure processes complex visual stimuli, particularly of social nature (e.g., faces, body movements) (Kanwisher, McDermott, & Chun 1997
), and is tightly connected with the amygdala (Morris, Friston, Buchel, Frith, Young, Calder, & Dolan 1998
; Pessoa, McKenna, Gutierrez, & Ungerleider 2002
; Sabatinelli, Bradley, Fitzsimmons, & Lang 2005
; Taylor, Liberzon, & Koeppe 2000
). This finding is consistent with the presence of disease specific abnormalities across sex, which might affect the coding of social stimuli, as suggested by performance perturbation in the CAH group relative to the control group found in the present work. These deficits might reflect impaired corticosteroid function rather than sex steroid since they affect equally boys and girls.
A number of caveats should be mentioned. First, our sample size was relatively small, and may have limited the exploration of correlations of brain activation with behavioral performance and treatment. However, the detection of a significant interaction between sex and diagnosis suggested that this effect was strong. Second, it was impossible to separate out the complicated effects of cortisol replacement medication and multiple hormones at the time of testing. However, our CAH patients were on approximately physiological dose replacement, overall disease control was good, and our hormonal measurements did not appear to influence the results. Third, the task was relatively complex, which may have led to some dispersion of effects because of increased noise. However, this task has been used in our laboratory for several years (McClure et al., 2004
; Monk et al., 2003
; Nelson et al., 2003
; Pine, Cohen, Gurley, Brook, & Ma 1998
), with a large number of healthy adolescents, and pediatric patients with anxiety and mood disorders. It has been shown to reliably activate the amygdala, to be sensitive to development (McClure et al., 2004
) function (Monk et al., 2003
) and to psychopathology (Pine et al., 1998
; McClure et al., in preparation). Fourth, there are virtually no data available on sex differences in amygdala response to evocative faces in healthy adolescents. Therefore, the sex differences found in the present study are important to validate in future work. Finally, our control sample consisted of healthy adolescents matched on all demographic characteristics, but without the stress of having a chronic disease. However, the use of a comparison group with a chronic disease also presents drawbacks, since the nature of the chronic disease can itself affect brain function in unique ways.
Despite these limitations, this first study of cerebral function in adolescents with CAH suggests altered amygdala function in this population, possibly reflecting an organizational effect of sex steroids. Future cognitive and neuroimaging studies in patients with CAH and other endocrine imbalances will provide further insight into the influence of hormones on the developing brain.