T he importance of the anterior cingulate gyrus for autism is suggested by three lines of evidence. 1) The anterior cingulate gyrus has been implicated in higher cognitive functions and in the expression and recognition of affect-functions that are compromised in autism. 2) Increased cell densities in many areas of the limbic system, including the anterior cingulate gyrus, have been found in postmortem studies of autistic patients (1). 3) Previous positron emission tomography (PET) studies (2, 3) suggested the anterior cingulate gyrus as an area of possible abnormality. None of the earlier studies used high-resolution coregistered magnetic resonance imaging (MRI) as a guide to more precise placement of anatomical regions of interest.
METHODWe studied seven patients with autism (five men and two women), all verbally fluent, whose mean age was 24.3 years (SD=10.7, range= 17-47) and whose IQs ranged from 60 to 125. The comparison group consisted of seven sex-and age-matched normal volunteers (mean age=26.4 years, SD=9.2, range=20-47; IQ range=88-136) without a history of substantial medical, psychiatric, or neurological disorders or a family history of psychiatric disorders. Patients with other medical, neurological, or neuropsychiatric disorders were excluded. A verbal fluency test was used to assess verbal functioning; scores for naming animals did not differ significantly between the patients and the comparison subjects (mean= 14.3, SD=10.5, versus mean=17.7, SD=8.8), whereas scores for words beginning with the letter T were lower among the patients than among the comparison subjects (mean=7.2, SD=2.2, versus mean=17.1, SD=3.4; t=4.30, df=11, p<0.05). One patient was being treated with nortriptyline at the time of the scanning, but the others had not taken psychoactive medications for at least several months. The patients were given general medical, neurological, and psychiatric examinations and the SMA-20 test. The patients' diagnoses of autism were confirmed by the Autism Diagnostic Interview (4) with the parents in six cases and by clinical interview in the seventh. Written informed consent was obtained from all subjects.MRI axial acquisitions were done with a 1.5-T GE Signa 5x system (three-dimensional volume spoiled gradient recall acquisition in the steady state, TR=24 msec, TE=5 msec, flip angle=40°, contiguous 1.2-mm slices). Two researchers (M.M.H., A.S.), without knowledge of diagnosis, outlined the anterior cingulate gyrus on axial MRI slices (intertracer intraclass correlation coefficient= 0.87), beginning with the plane showing the appearance of the cingulate sulcus and ending dorsally (25-30 planes higher) with the plane showing the disappearance of the corpus callosum. The anterior cingulate gyrus was outlined starting from the deepest recess of the cingulate sulcus, moving medially and then in an inferior direction until the callosal recess was reached. The two recesses Presented at the 149th annual meeting
