Supported by the “extreme male brain theory” (Baron-Cohen 1999), and influenced by prior investigations on the prevalence of autism spectrum disorder (ASD) proposing a male:female ratio of 6-8:1 (Fombonne 2005), ASD is still commonly seen as a male disorder. However, recent studies as well as clinical experience (Attwood 2008) suggest a clearly decreased male:female-ratio of 4:1 (Bartley 2006) also in high functioning patients with ASD.
Also, behavioral studies described different behavioral patterns of males and females with ASD, and particularly assigned a better social conduct to female patients. Nonetheless, to the authors’ knowledge the number of behavioral studies on “female autism” is still small, and so far, there are no studies using functional magnetic resonance imaging (fMRI) which try to address this topic.
Objectives:
As a better social adaptiveness in females with ASD compared to autistic males was previously suggested, in our study we tried to clarify whether patients with high-functioning ASD reveal gender-specific characteristics on a behavioral and/or neural level during participating in an empathy task. Elucidating gender-specific characteristics of ASD might have important implications for education and treatment of autistic individuals.
Methods:
28 patients with high-functioning ASD and 28 healthy subjects, matched for gender, age, and education, took part in an event-related fMRI study.
Participants were confronted with either emotional (E) or neutral (N) video stimuli. Each video was followed by two seven-point rating scales, one asking for the intensity of participants’ own emotions during the video (“SELF”-rating), and the second addressing the intensity of the emotion of the actor in the video (“OTHER”-rating).
Results:
Behaviorally, we neither found gender differences for the group of autistic patients nor for the healthy subjects. However, comparing the overall groups on the “SELF”- and the “OTHER”-rating revealed significantly less target-matching answers in the patient group. Moreover, patients rated the neutral videos (N) significantly more emotional.
Analysis of brain activation for the E>N contrast yielded activation of a network of superior frontal, superior temporal, and inferior frontal regions, accompanied by activation of the thalamus in case of healthy control subjects. In contrast to that, ASD patients revealed activation solely of superior frontal and superior temporal regions.
While there were no significant gender effects on brain activation for the healthy control group, we found increased activation in males with ASD compared to autistic females in the medial frontal cortex bilaterally, and in the precuneus.
Comparing both groups separated for gender yielded reduced activation in autistic females compared to their healthy control group in the amygdala, and in midbrain regions, in the periaqueductal gray in particular, while male patients compared to their healthy control group exhibited reduced activation of the bilateral middle frontal gyrus.
Conclusions:
Our data propose different ways of processing social information in males and females with ASD suggesting specific alterations on the level of “social motivation” in female patients, while male patients seem to exhibit stronger deficits in integrating multisensory information.
These findings might indicate gender-specific “endophenotypes” in ASD with potential implications for treatment.
See more of: Brain Imaging: fMRI-Social Cognition and Emotion Perception
See more of: Brain Structure & Function