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. 2006 Jul 19;26(29):7674-9.
doi: 10.1523/JNEUROSCI.1285-06.2006.

Stereological analysis of amygdala neuron number in autism

Cynthia Mills Schumann  1 , David G Amaral
Affiliations

Stereological analysis of amygdala neuron number in autism

Cynthia Mills Schumann et al. J Neurosci. .

Abstract

The amygdala is one of several brain regions suspected to be pathological in autism. Previously, we found that young children with autism have a larger amygdala than typically developing children. Past qualitative observations of the autistic brain suggest increased cell density in some nuclei of the postmortem autistic amygdala. In this first, quantitative stereological study of the autistic brain, we counted and measured neurons in several amygdala subdivisions of 9 autism male brains and 10 age-matched male control brains. Cases with comorbid seizure disorder were excluded from the study. The amygdaloid complex was outlined on coronal sections then partitioned into five reliably defined subdivisions: (1) lateral nucleus, (2) basal nucleus, (3) accessory basal nucleus, (4) central nucleus, and (5) remaining nuclei. There is no difference in overall volume of the amygdala or in individual subdivisions. There are also no changes in cell size. However, there are significantly fewer neurons in the autistic amygdala overall and in its lateral nucleus. In conjunction with the findings from previous magnetic resonance imaging studies, the autistic amygdala appears to undergo an abnormal pattern of postnatal development that includes early enlargement and ultimately a reduced number of neurons. It will be important to determine in future studies whether neuron loss in the amygdala is a consistent characteristic of autism and whether cell loss occurs in other brain regions as well.

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Figures

Figure 1.
Figure 1.
Brightfield photomicrograph of Nissl-stained coronal sections through rostral (a), midrostrocaudal (b), and caudal (c) levels of the amygdala. AAA, Anterior amygdaloid area; AB, accessory basal nucleus; AHA, amygdalohippocampal area; B, basal nucleus; C, central nucleus; COa, anterior cortical nucleus; COp, posterior cortical nucleus; EC, entorhinal cortex; H, hippocampus; I, intercalated nuclei; L, lateral nucleus; M, medial nucleus; NLOT, nucleus of the lateral olfactory tract; OT, optic tract; PAC, periamygdaloid cortex; PL, paralaminar nucleus; PU, putamen; SAS, semiannular sulcus; VC, ventral claustrum. Scale bar, 2 mm.
Figure 2.
Figure 2.
Photomicrograph of a Nissl-stained section illustrating the lateral nucleus at 100× (the magnification used for the optical fractionator) from a 15-year-old with autism. Scale bar, 10 μm.
Figure 3.
Figure 3.
Number of neurons in five subdivisions of the amygdala of autism (red) and control (blue) brains. The asterisk indicates significant difference (p = 0.03) in neuron number between autism and control lateral nuclei.
Figure 4.
Figure 4.
Bivariate scattergram of the number of neurons in the total amygdala of autism (red) and control (blue) brains by age.
See this image and copyright information in PMC

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