Volumetry of the human amygdala — An anatomical study

doi:10.1016/j.pscychresns.2009.11.005

Psychiatry Research: Neuroimaging

Volume 182, Issue 1, 30 April 2010, Pages 67-72

https://doi.org/10.1016/j.pscychresns.2009.11.005 Get rights and content

Abstract

A striking feature of the studies that have addressed the measurement of the amygdala is the wide range of volumes encountered, with reports of volumes ranging from 1 to almost 4 cm³. Another striking feature is the number of discrepancies in the landmarks adopted for manual tracing in magnetic resonance imaging (MRI). The goal of our study was to assess the anatomical volume of the amygdala on the basis of its cytoarchitecture while comparing the differences in age and sex. This study was performed on 21 normal male brains (mean age of 56.8 years) and 9 normal female brains (mean age of 61.2 years). The volume of the amygdala was measured by planimetry of Nissl-stained serial sections using ImageJ software. To address the complexity of the amygdala, we elected to use two types of amygdalar measurement that differ mainly in the definition of anterior pole boundaries. The average size of the classic amygdala was 1.24 cm³ (S.D. = 0.14), while the average size of the amygdala with wider borders was 1.63 cm³ (S.D. = 0.2). No interhemispheric or intersexual differences were observed for either type of amygdalar measurement. Neither sex revealed any statistically important relationship between volume of the amygdala and age. Our study was concerned exclusively with the anatomical volume of the amygdala rather than the MRI volume. Nevertheless, our results may have important implications for MRI studies because as of yet there is no gold standard for manual volumetry of the amygdala.

Introduction

Magnetic resonance imaging (MRI) volumetry of the amygdala has attracted the attention of many investigators in the last 15 years. The complex architecture of the amygdala and the small amount of signal contrast in MR images complicate the precise assessment of its borders. Due to this complexity the volume of the amygdala is most commonly assessed using a variety of external anatomical landmarks. These methods were adopted to ensure the reliability of such measurement. With the wide variety of anatomical landmarks used, volumes ranging from 1 to almost 4 cm³ have been found (Brierley et al., 2002). In several post-mortem studies the average volume of the amygdala ranged from 0.6 to 1.6 cm³ (Bogerts et al., 1985, Heckers et al., 1990, Scott et al., 1991, Vereecken, 1993Chance et al., 2002, Amunts et al., 2005). Therefore, it is believed that many MRI volumetric studies of the amygdala have overestimated its volume (Convit et al., 1999). Concerning post-mortem studies, Brierley et al. (2002) attributed these differences in volume to normal anatomical variation. We, however, attribute these differences to the definition of the amygdala in measurement protocols. Furthermore, nearly all of the above-mentioned post-mortem studies were performed for the purpose of comparison, not for the assessment of normal amygdalar volume. Such studies are rare and the number of observations rarely exceeds three brains (Stephan et al., 1987, Barger et al., 2007). The goal of our study was thus to assess the anatomical volume of the amygdala on a larger number of specimens than in most of the previous morphologic studies while examining potential differences in age and sex.

Section snippets

Material

Post-mortem volumetry of the amygdala was based on the examination of 36 brains from the neurolaboratory collection of the Anatomical Institute, First Faculty of Medicine, Charles University in Prague. Our collection consisted of 21 male brains (mean age of 56.8 years) and 9 female brains (mean age of 61.2 years). Clinical characteristics of the 30 cases are summarized in Table 1. The autopsy was carried out 24–48 h post-mortem. None of the subjects had any history of neurological or psychiatric

Results

The average size of the classic amygdala (V_Class) was 1.24 cm³ (S.D. = 0.14) (for detailed descriptive statistics see Table 2). For both sexes the volume of the right amygdala was greater by 2.44%, but the difference was not statistically significant (t = 1.16, 29 df, P = 0.25) (Fig. 2). No significant intersexual volume differences were found (t = − 1.19, 28 df, P = 0.24; r_PB = 0.17, P = 0.09). Neither sex revealed any statistically important relationship between V_Class and age (Fig. 3).

In the second

Discussion

The amygdala is a complex and heterogeneous structure involved in many autonomic regulations. The amygdala also plays an important role in motivation, memory, visual recognition and the integration of complex sensory information, especially related to emotionally relevant events (Dolan, 2000, LeDoux, 2000, Larson et al., 2006). The amygdala, due to its close association with the hippocampus, is one of the structures affected early in Alzheimer's disease (AD). With Alzheimer's disease becoming a

Acknowledgements

This work was supported by the Ministry of Health of the Czech Republic, Internal Grant Agency grant IGA MZ 2006, NR8931-4. We thank Kveta Patkova and Bohuslava Fulinova for the excellent technical assistance, and Associate Professor David Sedmera, M.D., PhD., Institute of Anatomy, for the helpful advice and comments. We are deeply indebted to the donors and their families who have made this study possible.

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Volumetry of the human amygdala — An anatomical study

Abstract

Introduction

Section snippets

Material

Results

Discussion

Acknowledgements

Neurobiology of Aging

Biological Psychiatry

Brain Research. Brain Research Reviews

Psychiatry Research: Neuroimaging

Psychiatry Research: Neuroimaging

Neuroscience

Neuropsychologia

Brain Research. Brain Research Reviews

Neuroscience

Neurobiology of Aging

Epilepsy Research

Journal of Neurological Sciences

Biological Psychiatry

Journal of Neuroscience Methods

Neuroscience

Neurobiology of Aging

Cytoarchitectonic mapping of the human amygdala, hippocampal region and entorhinal cortex: intersubject variability and probability maps

Anatomy and Embryology (Berlin)

A comparative volumetric analysis of the amygdaloid complex and basolateral division in the human and ape brain

American Journal of Physical Anthropology

The importance of accurate anatomic assessment for the volumetric analysis of the amygdala

Brazilian Journal of Medical and Biological Research

Basal ganglia and limbic system pathology in schizophrenia. A morphometric study of brain volume and shrinkage

Archives of General Psychiatry

Zur Normalen und patologischen Anatomie des Mandelkerngebiets

Journal für Psychologie und Neurologie

Studies of the vertebrate telencephalon. II. The nuclear pattern of the anterior olfactory nucleus, tuberculum olfactorium and the amygdaloid complex in adult man

Journal of Comparative Neurology

Functional neuroimaging of the human amygdala during emotional processing and learning

Correlation between rates of brain atrophy and cognitive decline in AD

Neurology

Asymmetries in the hippocampus and amygdala of chimpanzees (Pan troglodytes)

Behavioral Neuroscience

Temporolimbic volume reductions in schizophrenia

Archives of General Psychiatry