Stereological Analysis of Amygdala Neuron Number in Autism

“There are reports of altered packing density of cells, minor and highly variable disruption of dendritic orientation, reduced size and spacing of radial minicolumns of neurons in different cortical areas including the frontal lobe [28 ,29], and selective reduction in cell number in some forebrain structures [30].”

“processes are associated with a variety of neuropsy chiatric disorders, ranging from autism spectrum [58, 59] to anxiety disorders [57, 60].”

“Schumann and Amaral (2006) have identified the lateral nucleus as having accentuated pathological features.”

“The largest postmortem study of autism to use stereological methods for quantifying neuron numbers in 10-to 44-year-old cases found fewer neurons in the amygdala, a structure important in emotion, learning, and memory (Schumann and Amaral, 2006).”

“Structural and functional changes in the amygdala are associated with a variety of neuropsychiatric disorders ranging from autism spectrum (Schumann & Amaral, 2006; Mosconi et al. 2009) to anxiety disorders (Ledoux, 2007; Janak & Tye, 2015).”

“A recent stereological study of the amygdala in nine ASD brains showed consistently fewer neurons in the ASD amygdala, which is involved in the regulation of emotion (50).”

“…(Otsuka et al., 1999; Page et al., 2006), functional (Baron-Cohen et al., 1999; Critchley et al., 2000; Wang et al., 2004; Dalton et al., 2005; Ashwin et al., 2006; Williams et al., 2006), and post-mortem studies (Schumann and Amaral, 2006) indicate that amygdalar abnormalities are present in ASD.”

“2005) and with anxiety disorders (Pine 2007), and has particular relevance to ASD given evidence of amygdala abnormalities (Schumann and Amaral 2006).”

“Statistics reported in the text and figures represent the mean7SEM.”

“Results from the analysis of the features of axons in these and the three female cases did not differ from other cases within each group in this and other studies that used tissue from the same cases (Buxhoeveden et al., 2006; Schumann and Amaral, 2006; Yip et al., 2007).”

“…contiguous, and given the prior empirical evidence for abnormality of both structures in autism spectrum disorders (Schumann et al., 2004; Schumann and Amaral, 2006), these were broken into two regions of interest to evaluate their separate contributions by first making an independent…”

“…structures and their circuits may be affected in autism (e.g., Bauman and Kemper, 1985; Tsatsanis et al., 2003; Schumann et al., 2004; Haznedar et al., 2006; Schumann and Amaral, 2006; Shukla et al., 2010; Tamura et al., 2010; Cheon et al., 2011; Di Martino et al., 2011; Langen et al., 2012).”

“Postmortem investigations have demonstrated abnormal brain growth, including neuronal overgrowth in some regions (Courchesne, Mouton et al. 2011), and undergrowth in others (Schumann and Amaral 2006).”

“Significant structural abnormalities in the amygdala have also been associated with autism.(57,65)”

“There is also evidence of abnormalities in amygdala volume in autism (Abell et al., 1999; Schumann & Amaral, 2006; Sparks et al., 2002); this has resulted in theories emphasizing abnormalities in amygdala as central to autism spectrum disorder, especially to social symptoms (Nacewicz et al., 2006).”

“…development of social mechanisms, including attention, communication, and reward processing, may persist without intervention and could have consequential effects on the subsequent development of social-communicative abilities (Chevallier et al. 2012; Eyler et al. 2012; Schumann and Amaral 2006).”

“For instance, Schumann & Amaral (2006) carried out stereological analyses of nine adult male postmortem brains of patients with ASD and found no difference in the total volume of the amygdala or cell size, but they did report reductions in the number of neurons in the amygdalae of autistic…”

“For example, while amygdala volume and neuron number is normal or reduced at older ages, amygdala volume is increased at younger ages (19;22–26), suggesting neurobiological processes in the initial phase of autism may be unique.”

“Notably, in individuals with ASD, the amygdala displays hyperplasia at early developmental timepoints, but ultimately becomes hypoplastic by late childhood and early adolescence, when brain growth in normal subjects has caught up (Schumann and Amaral, 2006; Schumann et al., 2004).”

“Postmortem studies of individuals with autism have noted immature-appearing and densely packed cells(5,6) and fewer neurons within the amygdala.(7) Abnormal amygdala volumes have been observed across multiple structural MR imaging studies of adolescents and adults with autism.”

“…in neural growth during adolescence is arguably not an extension of, but instead categorically different from, the early phase of brain overgrowth (Courchesne, Campbell, & Solso, 2011; Schumann & Amaral, 2006; van Kooten et al., 2008; Vargas, Nascimbene, Krishnan, Zimmerman, & Pardo, 2005).”

“There is converging evidence implicating the amygdala in the neuropathology of autism from several areas of neuroscience including postmortem (Bauman and Kemper, 1985; Kemper and Bauman, 1998; Schumann and Amaral, 2006), structural magnetic resonance imaging (MRI), and functional MRI (fMRI) studies.”

“The amygdala and hippocampus are subcortical brain regions associated with ASD (Aylward et al., 1999; Schumann et al., 2004; Schumann and Amaral, 2006).”

“Subsequent work using modern stereological methods in a larger, seizure-free cohort found different, albeit related, abnormalities with fewer neurons in the amygdala of cases compared with controls.(44) The fact that the effects were most prominent in the lateral nucleus of the amygdala is intriguing given that a redu…”

“…an average shrinkage factor of 0.53 reported in this study, cincluding the NA; 3¼ Lauer et al. (2001), dconsidering an average shrinkage factor of 0.47 reported in this study; 4¼ Pakkenberg et al. (1990); 5¼ Schumann and Amaral (2006); 6¼Beckmann and Lauer (1997), eincluding the NA, fP50.”

“…1988, 1994; Allen and Courchesne, 2003), and especially the “social brain”, i.e. the amygdala (e.g. Baron-Cohen et al., 2000; Amaral et al., 2003; Schumann & Amaral, 2006), the fusiform gyrus (e.g. Schultz et al., 2003; van Kooten et al., 2008), the mirror neuron system (e.g. Oberman et al.,…”

“[59] found it in the lateral nucleus of the amygdala.”

“It is interesting, though, that the reduction in neuron number in the lateral nucleus of the amygdala in schizophrenia is similar to the reduced neuron numbers in the lateral nucleus reported in cases of autism (Schumann & Amaral, 2006).”

“…to social stress have been at least theoretically implicated in this anomalous pattern of amygdala development (Nacewicz et al., 2006; Schumann & Amaral, 2006), further research is necessary to explore how structural and functional abnormalities of the amygdala may be related to…”

“Amygdalar abnormalities have been widely documented and include reduced numbers of neurons (Schumann and Amaral, 2006), volumetric deviations from age-matched controls (Aylward et al., 1999; Munson et al., 2006; Nacewicz et al., 2006; Pierce et al., 2001; Schumann et al., 2004; Sparks et al.,…”

“Age-related and progressive neuronal pathology and neuronal loss in cerebellar Purkinje [115] or amygdala [116] cells in individuals with autism [117] are all representative of a neurodegenerative process [118–121].”

“Partial data and diagnostic information from a subset of cohort 1 (n = 19) have previously been published by Schumann and Amaral (31).”

“In other larger structures, significantly lower asf’s are generally used (Schumann and Amaral, 2006) With design-based stereology, the parameters for setting up each experiment are defined empirically and can be arrived at by a variety of means and logic.”

“Some differences of the estimated total number of neurons in the lateral nucleus in the amygdala in the control group in Schumann and Amaral [4] study (4.0 million), Kreczmanski et al. [66] (4.43 million) and 5.54 million in our study reflect mainly technical differences and in part interindividual differences.”

“For this analysis, about which we had specific predictions, we selected regions of interest (ROIs): the MTG, FG, AMY, MPFC, and IFG.”

“In contrast, the measurements of neuronal soma size in humans (Schumann and Amaral, 2006) might have underestimated true neuronal size, as compared to the perfusion-fixation condition that was used for rats and monkeys.”

“It has been suggested that overgrowth of this structure may be unique to the early development of the disorder (Schumann & Amaral, 2006), contributing to the atypical scaffolding of fundamental social and emotional skills (Sparks et al., 2002).”

“For example, it has been observed that adults with ASD have reduced amygdala [33] and hippocampus volume compared to typical individuals [34–36] while other studies have reported increased hippocampal volume [37] or no differences [38].”

“It is of interest that some of the brain regions where agerelated changes in the ASD group were found to show histological abnormalities in post-mortem ASD brains (Bauman and Kemper 1985; Casanova et al. 2006; Schumann and Amaral 2006).”

“Axonal loss in amygdala was reported histologically (Schumann & Amaral, 2006).”

“Schultz (11) suggested that abnormalities of the amygdala are likely to be responsible for developmental abnormalities of the subcortical face-processing pathway system, since there are known structural abnormalities of the amygdala in ASD (17,18).”

“It has also been shown that the lateral amygdala has an abnormal growth pattern and significantly fewer neurons in autistic patients (33).”

“Toddlers have exhibited bilateral amygdala overgrowth which correlates with severity of social impairment (Cynthia Mills Schumann et al. 2009).”

“The amygdala’s possible contribution to ASD is supported by a large literature showing structural and histological abnormalities (Amaral et al., 2008; Bauman and Kemper, 1985; Ecker et al., 2012; Schumann and Amaral, 2006; Schumann et al., 2004) as well as atypical activation across BOLD-fMRI studies (Gotts et al.”

“…the one quantitative stereological study conducted to date reported a ∼15% decrease in the number of neurons in adolescents and adults with autism (Schumann and Amaral, 2006), This finding suggests that either neuron number does not account for the increase in amygdala size in young children…”

“…participants (Bauman and Kemper, 1985; Abell et al., 1999; Aylward et al., 1999; Howard et al., 2000; Pierce et al., 2001; Nacewicz et al., 2006; Schumann and Amaral, 2006) and some have suggested that amygdala dysfunction may play a causal role in autistic social impairment (Baron-Cohen et…”

“Neuron number data originally published in [17,35].”

“Histologic studies of postmortem brain tissue from patients with ASD have shown neuronal abnormalities in the amygdala.(9,10) Volumetric studies in preschool-age children with ASD have consistently shown that the amygdala is enlarged,(11-14) but little is known about amygdala function in very young children with ASD.”

“…et al., 2015) and neurological deficiencies in learning, memory, recognition, and emotional behaviors (Foster, Rinaman, & Cryan, 2017; Gareau et al., 2011; Smith, 2015), along with less social behaviors (Mayer, Tillisch, & Gupta, 2015; Schumann & Amaral, 2006; Vuong, Yano, Fung, & Hsiao, 2017).”

“…the limbic system, including involvement of the amygdala, hippocampus, and anterior cingulate cortex [Lawrence, Kemper, Bauman, & Blatt, 2010; Schumann & Amaral, 2006; Simms, Kemper, Timbie, Bauman, & Blatt, 2009] as well as scattered cytoarchitectonic abnormalities in other cortical areas…”

“However, in two disorders characterized by aberrant social behavior, autism spectrum disorder (Schumann and Amaral, 2006) and William’s Syndrome (Galaburda and Bellugi, 2006), the lateral nucleus appears to be the most affected amygdaloid nucleus and is suggested to contribute significantly to…”

“Neuronal numbers were found to be fewer in the amygdala of individuals diagnosed with an ASD than controls [27].”

“Based on a postmortem study, the dysfunction of amygdala, which may lead to changes in the aggressive and emotional behavior, might be explained by the significant reduced number of neurons in this area of the autistic brain when compared with age-matched typically developing children [Schulkin, 2007; Schumann and Ama…”

“Given findings of anatomical abnormality [23–25] and functional abnormality [26] of the amygdala in individuals with ASD, it is possible that dysregulation of the relationship between personal space and interpersonal distance relates directly to amygdala dysfunction.”

“…Gaffney et al., 1988; Arin et al., 1991; Piven et al., 1992; Hashimoto et al., 1993; Raymond et al., 1996; Fatemi et al., 2002; Palmen et al., 2004; Schumann and Amaral, 2006; Kulesza and Mangunay, 2008; Whitney et al., 2008; Wegiel et al., 2010; Kulesza et al., 2011; Stoner et al., 2014; Wegiel…”

“In a previous study in our laboratory, we found evidence of accelerated cell loss in adult cases of ASD relative to TD cases, especially in the lateral nucleus (Schumann & Amaral, 2006; Morgan, Barger, Amaral, & Schumann, 2014).”

“Previous findings in the fusiform gyrus and amygdala, both of which send and receive connections with areas 44 and 45, showed reduced neuron number and, in the fusiform gyrus, reduced somatic volume [66, 73].”

“This is noteworthy because previous studies have suggested that atypical amygdala functions may contribute to the ASD social phenotype (Schumann and Amaral 2006; Mosconi et al. 2009; Schumann et al. 2009).”

“Amaral DG, Bauman MD, Schumann CM (2003) The amygdala and autism: implications from non-human primate studies.”

“However, in older adolescents and in adults with ASD, the amygdala is similar (Haznedar et al., 2000) or reduced in volume (Pierce et al., 2001; Nacewicz et al., 2006; Schumann and Amaral, 2006) and neuronal numbers (Avino et al., 2018).”

“…et al., 2010), schizophrenia (Lawrie et al., 2003; Kreczmanski et al., 2007), and autism (Baron-Cohen et al., 2000; Schumann et al., 2004, 2009; Schumann and Amaral, 2006; Mosconi et al., 2009), as well as in neurological disorders such as epilepsy (Aliashkevich et al., 2003;…”

“Yet, as Schumann reviewed at the symposium, when postmortem studies of brains from older individuals with autism are carried out, there are actually significantly fewer neurons (Schumann and Amaral, 2006).”

“Reported genetic polymorphisms are marked with blue circles, as indicated in the inset (Color figure online) and Pauls 2003; Schumann and Amaral 2006).”