Longitudinal microstructural changes in 18 amygdala nuclei resonate with cortical circuits and phenomics.

The amygdala nuclei modulate distributed neural circuits that most likely evolved to respond to environmental threats and opportunities. So far, the specific role of unique amygdala nuclei in the context processing of salient environmental cues lacks adequate characterization across neural systems and over time. Here, we present amygdala nuclei morphometry and behavioral findings from longitudinal population data (>1400 subjects, age range 40-69 years, sampled 2-3 years apart): the UK Biobank offers exceptionally rich phenotyping along with brain morphology scans. This allows us to quantify how 18 microanatomical amygdala subregions undergo plastic changes in tandem with coupled neural systems and delineating their associated phenome-wide profiles. In the context of population change, the basal, lateral, accessory basal, and paralaminar nuclei change in lockstep with the prefrontal cortex, a region that subserves planning and decision-making. The central, medial and cortical nuclei are structurally coupled with the insular and anterior-cingulate nodes of the salience network, in addition to the MT/V5, basal ganglia, and putamen, areas proposed to represent internal bodily states and mediate attention to environmental cues. The central nucleus and anterior amygdaloid area are longitudinally tied with the inferior parietal lobule, known for a role in bodily awareness and social attention. These population-level amygdala-brain plasticity regimes in turn are linked with unique collections of phenotypes, ranging from social status and employment to sleep habits and risk taking. The obtained structural plasticity findings motivate hypotheses about the specific functions of distinct amygdala nuclei in humans.

Connectivity-based parcellation of the amygdala and identification of its main white matter connections.

The amygdala plays a role in emotion, learning, and memory and has been implicated in behavioral disorders. Better understanding of the amygdala circuitry is crucial to develop new therapies for these disorders. We used data from 200 healthy-subjects from the human connectome project. Using probabilistic tractography, we created population statistical maps of amygdala connectivity to brain regions involved in limbic, associative, memory, and reward circuits. Based on the amygdala connectivity with these regions, we applied k-means clustering to parcellate the amygdala into three clusters. The resultant clusters were averaged across all subjects and the main white-matter pathways of the amygdala from each averaged cluster were generated. Amygdala parcellation into three clusters showed a medial-to-lateral pattern. The medial cluster corresponded with the centromedial and cortical nuclei, the basal cluster with the basal nuclei and the lateral cluster with the lateral nuclei. The connectivity analysis revealed different white-matter pathways consistent with the anatomy of the amygdala circuit. This in vivo connectivity-based parcellation of the amygdala delineates three clusters of the amygdala in a mediolateral pattern based on its connectivity with brain areas involved in cognition, memory, emotion, and reward. The human amygdala circuit presented in this work provides the first step for personalized amygdala circuit mapping for patients with behavioral disorders.

A Novel Sublabial Anterior Transmaxillary Approach for Medically Refractory Mesial Temporal Lobe Epilepsy: A Comparative Anatomic Study.

BACKGROUND: Current approaches for mesial temporal lobe epilepsy may result in suboptimal seizure control and cognitive decline. An incomplete treatment of the epileptogenic zone and unnecessary violation of functional cortical and subcortical areas may contribute to suboptimal results. OBJECTIVE: To describe and test the anatomic feasibility of a novel endoscopic anterior transmaxillary (ATM) approach to the temporal lobe and to compare the described technique to other transfacial approaches. METHODS: Twenty-four cadaveric brain hemispheres fixed in formalin were used to study anterior temporal surface anatomy. Two additional hemispheres were fixed in formalin and then frozen for white matter dissections. Subsequently, bilateral dissections on 4 injected cadaveric heads were used to describe the endoscopic ATM approach and to evaluate various anterior endoscopic corridors for the temporal pole and mesial temporal lobe structures. RESULTS: The ATM approach was considered superior because of direct visualization of the temporal pole and natural alignment with the mesial temporal structures. The mean exposure corridor covered 49.1° in the sagittal plane and 66.2° in the axial plane. The ATM allowed direct access lateral to the maxillary and mandibular nerves with an anterior-posterior trajectory aligned to the longitudinal axis of the hippocampus formation, allowing for a selective amygdalohippocampectomy with preservation of the trigeminal branches and the lateral temporal neocortex. CONCLUSION: The ATM approach is anatomically feasible, providing a direct and selective approach for the temporal pole and mesial temporal lobe structures, with a substantial angle of visualization because of its direct alignment with the mesial temporal lobe structures.

The brain of the tree pangolin (Manis tricuspis). VII. The amygdaloid body.

Here, we describe the cytoarchitecture and chemoarchitecture of the amygdaloid body of the tree pangolin. Our definition of the amygdaloid body includes the pallial portions of the amygdala, and the centromedial group that is a derivative of the subpallium and part of the extended amygdala. The remainder of the extended amygdala is not described herein. Within the amygdaloid body of the tree pangolin, we identified the basolateral group (composed of the lateral, basal, and accessory basal amygdaloid nuclei), the superficial, or cortical nuclei (the anterior and posterior cortical nuclei, the periamygdaloid cortex, and nuclei of the olfactory tract), the centromedial group (the central amygdaloid nucleus and the medial nuclear cluster), and other amygdaloid nuclei (the anterior amygdaloid area, the amygdalohippocampal area, the intramedullary group, and intercalated islands). The location within and relative to each other within the amygdaloid body and the internal subdivisions of these groups were very similar to that reported in other mammalian species, with no clearly derived features specific to the tree pangolin. The only variation was the lack of an insular appearance of the intercalated islands, which in the tree pangolin were observed as a continuous band of neurons located dorsomedial to the basolateral group similar in appearance to and almost continuous with the intramedullary group. In carnivores, the closest relatives of the pangolins, and laboratory rats, a similar appearance of portions of the intercalated islands has been noted.

Optic Tract as an Upper Limit in Amygdalectomy: Microsurgical Study.

BACKGROUND: In surgeries involving resection of the amygdala, despite clear relations established with the medial, lateral, anterior, posterior, and inferior segments, the upper limit remains controversial. The optic tract (OT) has been anatomically considered as a good landmark immediately inferior to the striatopallidal region. This anatomic structure has barely been explored by microsurgical study, generating uncertainty about the exact relationship with the surrounding structures. OBJECTIVE: To describe the OT in its entire length through microsurgical study, showing its superior, inferior, medial, and lateral relationships and highlighting its value as a landmark in superior amygdala resection. METHODS: Microsurgical anatomic dissection of the OT, from its origin in the chiasm to the lateral geniculate nucleus was performed in 8 alcohol-fixed human hemispheres, showing its different segments and relations. Photographs were taken from different angles to facilitate surgical orientation. RESULTS: We performed a dissection of the OT, showing its position relative to caudate and hippocampal formations. We exposed the structures related to the OT superiorly (striatopallidal region and superior caudate fasciculus), inferiorly (head of the hippocampus, amygdala, anterior choroidal artery, perforating artery branch of the anterior choroidal artery, terminal stria, and basal vein), medially (internal capsule and midbrain), and laterally (temporal stem [uncinate and inferior fronto-occipital fascicle], anterior perforated substance, and superior caudate fasciculus). CONCLUSION: To date, there is a paucity of articles describing the anatomy of the OT from a neurosurgery perspective. In this study, we describe the microsurgical anatomic path of the OT, as a reliable upper limit landmark for amygdala resection.

Suppression of non-selected solutions as a possible brain mechanism for ambiguity resolution in the word fragment task completion task.

Brain systems dealing with multiple meanings of ambiguous stimuli are relatively well studied, while the processing of non-selected meanings is less investigated in the neurophysiological literature and provokes controversy between existing theories. It is debated whether these meanings are actively suppressed and, if yes, whether suppression characterizes any task that involves alternative solutions or only those tasks that emphasize semantic processing or the existence of alternatives. The current functional MRI event-related study used a modified version of the word fragment completion task to reveal brain mechanisms involved in implicit processing of the non-selected solutions of ambiguous fragments. The stimuli were pairs of fragmented adjectives and nouns. Noun fragments could have one or two solutions (resulting in two words with unrelated meanings). Adjective fragments had one solution and created contexts strongly suggesting one solution for ambiguous noun fragments. All fragmented nouns were presented twice during the experiment (with two different adjectives). We revealed that ambiguity resolution was associated with a reduced BOLD signal within several regions related to language processing, including the anterior hippocampi and amygdala and posterior lateral temporal cortex. Obtained findings were interpreted as resulting from brain activity inhibition, which underlies a hypothesized mechanism of suppression of non-selected solutions.

The evolutionary trajectories of the individual amygdala nuclei in the common shrew, guinea pig, rabbit, fox and pig: A consequence of embryological fate and mosaic-like evolution.

The amygdala primarily evolved as a danger detector that regulates emotional behaviours and learning. However, it is also engaged in stress responses as well as olfactory/pheromonal and reproductive functions. All of these functions are processed by a set of nuclei which are derived from different telencephalic sources (pallial and subpallial) and have a unique cellular structure and specific connections. It is unclear how these individual anatomical and functional units evolved to fit the amygdala to the specific needs of various mammals. Thus, this study provides quantitative data regarding volumes, neuron density and neuron numbers in the main amygdala nuclei of the common shrew, guinea pig, rabbit, fox and pig - species from across the mammalian phylogeny which differ in brain complexity and ecology. The results show that the volume of the amygdala and its individual nuclei scale with negative allometry relative to brain mass (an allometric coefficient below one). However, in relation to the whole amygdala volume, volumes and volumetric percentages of the lateral (LA) and basomedial (BM) nuclei scale with positive allometry, for the medial (ME) and lateral olfactory tract (NLOT) nuclei these parameters scale with negative allometry while the values of these parameters for the basolateral (BL), central (CE) and cortical (CO) nuclei scale with isometry. Moreover, density of neurons scales with strong negative allometry relative to both brain mass and amygdala volume with values of allometric coefficient below zero across studied species. This value for BL is significantly lower than that for the whole amygdala, for ME it is significantly higher while values for NLOT, CE, CO, LA and BM are quite similar to the value for whole amygdala. Finally, neuron numbers in the whole amygdala and its individual nuclei scale with negative allometry in relation to brain mass. However, in relation to the number of neurons in the whole amygdala, neuron numbers and percentages of neurons for LA and BM scale with positive allometry, for BL and NLOT they scale with negative allometry while the values of these parameters for CE, CO and ME scale with isometry. In conclusion, all of these results indicate that each of the nuclei studied displays a different and unique pattern of evolution in relation to brain mass or the whole amygdala volume. These patterns do not match with the various classical concepts of amygdala parcellation; however, in some way, they reflect diversity revealed by the expression of homeobox genes in various embryological studies.

Harsh Parenting and Child Brain Morphology: A Population-Based Study.

Evidence suggests that maltreatment shapes the child's brain. Little is known, however, about how normal variation in parenting influences the child neurodevelopment. We examined whether harsh parenting is associated with the brain morphology in 2,410 children from a population-based cohort. Mothers and fathers independently reported harsh parenting at child age 3 years. Structural and diffusion-weighted brain morphological measures were acquired with MRI scans at age 10 years. We explored whether associations between parenting and brain morphology were explained by co-occurring adversities, and whether there was a joint effect of both parents' harsh parenting. Maternal harsh parenting was associated with smaller total gray (ß = -0.05 (95%CI = -0.08; -0.01)), cerebral white matter and amygdala volumes (ß = -0.04 (95%CI = -0.07; 0)). These associations were also observed with the combined harsh parenting measure and were robust to the adjustment for multiple confounding factors. Similar associations, although non-significant, were found between paternal parenting and these brain outcomes. Maternal and paternal harsh parenting were not associated with the hippocampus or the white matter microstructural metrics. We found a long-term association between harsh parenting and the global brain and amygdala volumes in preadolescents, suggesting that adverse rearing environments common in the general population are related to child brain morphology.

Subcortical volumes across the lifespan: Data from 18,605 healthy individuals aged 3-90 years.

Age has a major effect on brain volume. However, the normative studies available are constrained by small sample sizes, restricted age coverage and significant methodological variability. These limitations introduce inconsistencies and may obscure or distort the lifespan trajectories of brain morphometry. In response, we capitalized on the resources of the Enhancing Neuroimaging Genetics through Meta-Analysis (ENIGMA) Consortium to examine age-related trajectories inferred from cross-sectional measures of the ventricles, the basal ganglia (caudate, putamen, pallidum, and nucleus accumbens), the thalamus, hippocampus and amygdala using magnetic resonance imaging data obtained from 18,605 individuals aged 3-90 years. All subcortical structure volumes were at their maximum value early in life. The volume of the basal ganglia showed a monotonic negative association with age thereafter; there was no significant association between age and the volumes of the thalamus, amygdala and the hippocampus (with some degree of decline in thalamus) until the sixth decade of life after which they also showed a steep negative association with age. The lateral ventricles showed continuous enlargement throughout the lifespan. Age was positively associated with inter-individual variability in the hippocampus and amygdala and the lateral ventricles. These results were robust to potential confounders and could be used to examine the functional significance of deviations from typical age-related morphometric patterns.

White Fiber Correlates of Amygdalohippocampectomy Through the Middle Temporal Gyrus Approach.

OBJECTIVE: The white fiber and gross anatomy relevant for performing amygdalohippocampectomy through the middle temporal gyrus approach for mesial temporal sclerosis has been depicted by white fiber dissection. METHODS: Three previously frozen and formalin fixed cerebral hemispheres were studied. The Klingler method of fiber dissection was used to study the anatomy. The primary tools used were hand-made wooden spatulas, forceps, and microscissors. The anatomy of the amygdala and hippocampus and the landmarks for performing the disconnection during epilepsy surgery are presented. The white fibers at risk during the middle temporal gyrus approach were studied. RESULTS: The white fiber tracts at risk during the middle temporal gyrus approach for epilepsy surgery are the fibers of the inferior frontooccipital fasciculus, temporal extension of the anterior commissure, Meyer loop of the optic radiation, and uncinate fasciculus. On the basis of our anatomic dissections, we present a novel entry point into the temporal horn, potentially minimizing injury to the fibers of the sagittal stratum. We also propose novel landmarks to perform the amygdala disconnection in mesial temporal sclerosis. CONCLUSIONS: The middle temporal gyrus is a commonly used approach to perform temporal lobectomy and amygdalohippocampectomy for patients with mesial temporal sclerosis. The anatomy relevant to the approach as presented will aid while performing epilepsy surgery.

High-resolution mapping and digital atlas of subcortical regions in the macaque monkey based on matched MAP-MRI and histology.

Subcortical nuclei and other deep brain structures are known to play an important role in the regulation of the central and peripheral nervous systems. It can be difficult to identify and delineate many of these nuclei and their finer subdivisions in conventional MRI due to their small size, buried location, and often subtle contrast compared to neighboring tissue. To address this problem, we applied a multi-modal approach in ex vivo non-human primate (NHP) brain that includes high-resolution mean apparent propagator (MAP)-MRI and five different histological stains imaged with high-resolution microscopy in the brain of the same subject. By registering these high-dimensional MRI data to high-resolution histology data, we can map the location, boundaries, subdivisions, and micro-architectural features of subcortical gray matter regions in the macaque monkey brain. At high spatial resolution, diffusion MRI in general, and MAP-MRI in particular, can distinguish a large number of deep brain structures, including the larger and smaller white matter fiber tracts as well as architectonic features within various nuclei. Correlation with histology from the same brain enables a thorough validation of the structures identified with MAP-MRI. Moreover, anatomical details that are evident in images of MAP-MRI parameters are not visible in conventional T1-weighted images. We also derived subcortical template "SC21" from segmented MRI slices in three-dimensions and registered this volume to a previously published anatomical template with cortical parcellation (Reveley et al., 2017; Saleem and Logothetis, 2012), thereby integrating the 3D segmentation of both cortical and subcortical regions into the same volume. This newly updated three-dimensional D99 digital brain atlas (V2.0) is intended for use as a reference standard for macaque neuroanatomical, functional, and connectional imaging studies, involving both cortical and subcortical targets. The SC21 and D99 digital templates are available as volumes and surfaces in standard NIFTI and GIFTI formats.

Dissecting the midlife crisis: disentangling social, personality and demographic determinants in social brain anatomy.

In any stage of life, humans crave connection with other people. In midlife, transitions in social networks can relate to new leadership roles at work or becoming a caregiver for aging parents. Previous neuroimaging studies have pinpointed the medial prefrontal cortex (mPFC) to undergo structural remodelling during midlife. Social behavior, personality predisposition, and demographic profile all have intimate links to the mPFC according in largely disconnected literatures. Here, we explicitly estimated their unique associations with brain structure using a fully Bayesian framework. We weighed against each other a rich collection of 40 UK Biobank traits with their interindividual variation in social brain morphology in ~10,000 middle-aged participants. Household size and daily routines showed several of the largest effects in explaining variation in social brain regions. We also revealed male-biased effects in the dorsal mPFC and amygdala for job income, and a female-biased effect in the ventral mPFC for health satisfaction.

Impact of Mesial Temporal Lobe Resection on Brain Structure in Medically Refractory Epilepsy.

OBJECTIVE: Surgical resection can decrease seizure frequency in medically intractable temporal lobe epilepsy. However, the functional and structural consequences of this intervention on brain circuitry are poorly understood. We investigated structural changes that occur in brain circuits after mesial temporal lobe resection for refractory epilepsy. Specifically, we used neuroimaging techniques to evaluate changes in 1) contralesional hippocampal and bilateral mammillary body volume and 2) brain-wide cortical thickness. METHODS: Serial T1-weighted brain magnetic resonance images were acquired before and after surgery (1.6 ± 0.5 year interval) in 21 patients with temporal lobe epilepsy (9 women, 12 men; mean age, 39.4 ± 11.5 years) who had undergone unilateral temporal lobe resection (14 anterior temporal lobectomy; 7 selective amygdalohippocampectomy). Blinded manual segmentation of the unresected hippocampal formation and bilateral mammillary bodies was performed using the Pruessner and Copenhaver protocols, respectively. Brain-wide cortical thickness estimates were computed using the CIVET pipeline. RESULTS: Surgical resection was associated with a 5% reduction in contralesional hippocampal volume (P < 0.01) and a 9.5% reduction in mammillary body volume (P = 0.03). In addition, significant changes in cortical thickness were observed in contralesional anterior and middle cingulate gyrus and insula (Pfalse discovery rate < 0.01) as well as in other temporal, frontal, and occipital regions (Pfalse discovery rate < 0.05). Postoperative verbal memory function was significantly associated with cortical thickness change in contralesional inferior temporal gyrus (R2 = 0.39; P = 0.03). CONCLUSIONS: These results indicate that mesial temporal lobe resection is associated with both volume loss in spared Papez circuitry and changes in cortical thickness across the brain.

Neonatal amygdala volumes and the development of self-regulation from early infancy to toddlerhood.

Objective: At the broadest level, self-regulation (SR) refers to a range of separate, but interrelated, processes (e.g., working memory, inhibition, and emotion regulation) central for the regulation of cognition, emotion, and behavior that contribute to a plethora of health and mental health outcomes. SR skills develop rapidly in early childhood, but their neurobiological underpinnings are not yet well understood. The amygdala is one key structure in negative emotion generation that may disrupt SR. In the current study, we investigated the associations between neonatal amygdala volumes and mother-reported and observed child SR during the first 3 years of life. We expected that larger neonatal amygdala volumes would be related to poorer SR in children. Method: We measured amygdala volumes from magnetic resonance imaging (MRI) performed at age M = 3.7 ± 1.0. We examined the associations between the amygdala volumes corrected for intracranial volume (ICV) and (a) parent-reported indicators of SR at 6, 12, and 24 months (N = 102) and (b) observed task-based indicators of SR (working memory and inhibitory control) at 30 months of age in a smaller subset of participants (N = 80). Results: Bilateral neonatal amygdala volumes predicted poorer working memory at 30 months in girls, whereas no association was detected between amygdalae and inhibitory control or parent-reported SR. The left amygdala by sex interaction survived correction for multiple comparisons. Conclusions: Neonatal amygdala volume is associated with working memory, particularly among girls, and the association is observed earlier than in prior studies. Moreover, our findings suggest that the neural correlates for parent-reported, compared to observed early life SR, may differ. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

El término cuerpo amigdaloide en la terminología médica / The term amygdaloid body in medical terminology

RESUMEN: En terminología médica el término amígdala cerebral es utilizado para denominar a la estructura que según la Terminologia Neuroanatomica y Terminologia Anatomica se conoce como cuerpo amigadaloide, la cual está constituida por diversos núcleos y es responsable de las emociones, el comportamiento, regulación de la ansiedad, la agresión, el miedo, la memoria emocional, la cognición social y las respuestas al estrés. Siendo la amígdala cerebral una estructura tan importante el objetivo de este estudio fue: analizar el significado del término amígdala cerebral en la Terminologia Neuronatomica y en la Terminologia Anatomica y contrastar si el origen de sus raíces greco latinas concuerdan con la función de esta estructura acorde con los requerimientos de la FIPAT. Para ello se consultó los diccionarios de la Lengua Española, Diccionario DGE Griego Español, Diccionario VOX Griego Español, Diccionario Médico, Biológico, Histológico y Etimológico de la Universidad de Salamanca y Diccionario de Términos Médicos de la Real Academia Nacional de Medicina, así como algunos artículos y libros clásicos de anatomía. Los resultados indicaron que el término amígdala tiene el mismo significado en griego como en latín, en donde ἀμυγδαλέα, ἀμυγδαλέας (pr. amygdaléa, amygdaléas) es el árbol del almedro y ἀμυγδάλη, ἀμυγδάλης (pr. amygdále, amygdáles) significa almendra. Conociendo tanto la anatomía como la fisiología de esta estructura su forma no se asemeja a la de una almendra y su denominación actual no está acorde con los requerimientos de la FIPAT por lo cual consideramos que esta debe ser revisada.

SUMMARY: In medical terminology the term brain amygdala is used to refer to the structure that according to the Terminologia Neuroanatomica and Terminologia Anatomica is known as the amydaloid body, which is made up of various nuclei and is responsible for emotions, behavior, regulation of the anxiety, aggression, fear, emotional memory, social cognition, and responses to stress. Being the cerebral amygdala such an important structure, the objective of this study was: to analyze the meaning of the term cerebral amygdala in Terminologia Neuroanatomica and in Terminologia Anatomica and to contrast if the origin of its Greek Latin roots agrees with the function of this structure according to the requirements of the FIPAT. For this, the dictionaries of the Royal Spanish Academy, the DGE Greek Spanish Dictionary, the VOX Greek Spanish Dictionary, the Medical, Biological, Histological and Etymological Dictionary of the University of Salamanca, the Dictionary of the Royal National Academy of Medicine, as well as some articles and classic books of anatomy. The results indicated that the term amygdala has the same meaning in Greek as in Latin, where? ἀμυγδαλέα, ἀμυγδαλέας (pr. Amygdaléa, amygdaléas) is the almond tree andἀμυγδάλη, ἀμυγδάλης (pr. amygdále, amygdáles) means almond. Knowing both the anatomy and the physiology of this structure, its shape does not resemble that of an almond and its current name is not in accordance with the requirements of the FIPAT, for which we consider that it should be revised.

Microsurgical anatomy of the amygdaloid body and its connections.

The amygdaloid body is a limbic nuclear complex characterized by connections with the thalamus, the brainstem and the neocortex. The recent advances in functional neurosurgery regarding the treatment of refractory epilepsy and several neuropsychiatric disorders renewed the interest in the study of its functional Neuroanatomy. In this scenario, we felt that a morphological study focused on the amygdaloid body and its connections could improve the understanding of the possible  implications in functional neurosurgery. With this purpose we performed a morfological study using nine formalin-fixed human hemispheres dissected under microscopic magnification by using the fiber dissection technique originally described by Klingler. In our results the  amygdaloid body presents two divergent projection systems named dorsal and ventral amygdalofugal pathways connecting the nuclear complex with the septum and the hypothalamus. Furthermore, the amygdaloid body is connected with the hippocampus through the amygdalo-hippocampal bundle, with the anterolateral temporal cortex through the amygdalo-temporalis fascicle, the anterior commissure and the temporo-pulvinar bundle of Arnold, with the insular cortex through the lateral olfactory stria, with the ambiens gyrus, the para-hippocampal gyrus and the basal forebrain through the cingulum, and with the frontal cortex through the uncinate fascicle. Finally, the amygdaloid body is connected with the brainstem through the medial forebrain bundle. Our description of the topographic anatomy of the amygdaloid body and its connections, hopefully represents a useful tool for clinicians and scientists, both in the scope of application and speculation.

Genetic scores for adult subcortical volumes associate with subcortical volumes during infancy and childhood.

Individual differences in subcortical brain volumes are highly heritable. Previous studies have identified genetic variants that underlie variation in subcortical volumes in adults. We tested whether those previously identified variants also affect subcortical regions during infancy and early childhood. The study was performed within the Generation R study, a prospective birth cohort. We calculated polygenic scores based on reported GWAS for volumes of the accumbens, amygdala, brainstem, caudate nucleus, globus pallidus, putamen, and thalamus. Participants underwent cranial ultrasound around 7 weeks of age (range: 3-20), and we obtained metrics for the gangliothalamic ovoid, a predecessor of the basal ganglia. Furthermore, the children participated in a magnetic resonance imaging (MRI) study around the age of 10 years (range: 9-12). A total of 340 children had complete data at both examinations. Polygenic scores primarily associated with their corresponding volumes at 10 years of age. The scores also moderately related to the diameter of the gangliothalamic ovoid on cranial ultrasound. Mediation analysis showed that the genetic influence on subcortical volumes at 10 years was only mediated for 16.5-17.6% of the total effect through the gangliothalamic ovoid diameter at 7 weeks of age. Combined, these findings suggest that previously identified genetic variants in adults are relevant for subcortical volumes during early life, and that they affect both prenatal and postnatal development of the subcortical regions.

Redundancy circuits of the commissural pathways in human and rhesus macaque brains.

It has been hypothesized that the human brain has less redundancy than animals, but the structural evidence has not been identified to confirm this claim. Here, we report three redundancy circuits of the commissural pathways in primate brains, namely the orbitofrontal, temporal, and occipital redundancy circuits of the anterior commissure and corpus callosum. Each redundancy circuit has two distinctly separated routes connecting a common pair of cortical regions. We mapped their trajectories in human and rhesus macaque brains using individual and population-averaged tractography. The dissection results confirmed the existence of these redundancy circuits connecting the orbitofrontal lobe, amygdala, and visual cortex. The volume analysis showed a significant reduction in the orbitofrontal and occipital redundancy circuits of the human brain, whereas the temporal redundancy circuit had a substantial organizational difference between the human and rhesus macaque. Our results support the hypothesis that the human brain has less redundancy in the commissural pathways than that of the rhesus macaque brain. Further studies are needed to explore its neuropathological implications.

High resolution automated labeling of the hippocampus and amygdala using a 3D convolutional neural network trained on whole brain 700 µm isotropic 7T MP2RAGE MRI.

Image labeling using convolutional neural networks (CNNs) are a template-free alternative to traditional morphometric techniques. We trained a 3D deep CNN to label the hippocampus and amygdala on whole brain 700 µm isotropic 3D MP2RAGE MRI acquired at 7T. Manual labels of the hippocampus and amygdala were used to (i) train the predictive model and (ii) evaluate performance of the model when applied to new scans. Healthy controls and individuals with epilepsy were included in our analyses. Twenty-one healthy controls and sixteen individuals with epilepsy were included in the study. We utilized the recently developed DeepMedic software to train a CNN to label the hippocampus and amygdala based on manual labels. Performance was evaluated by measuring the dice similarity coefficient (DSC) between CNN-based and manual labels. A leave-one-out cross validation scheme was used. CNN-based and manual volume estimates were compared for the left and right hippocampus and amygdala in healthy controls and epilepsy cases. The CNN-based technique successfully labeled the hippocampus and amygdala in all cases. Mean DSC = 0.88 ± 0.03 for the hippocampus and 0.8 ± 0.06 for the amygdala. CNN-based labeling was independent of epilepsy diagnosis in our sample (p = .91). CNN-based volume estimates were highly correlated with manual volume estimates in epilepsy cases and controls. CNNs can label the hippocampus and amygdala on native sub-mm resolution MP2RAGE 7T MRI. Our findings suggest deep learning techniques can advance development of morphometric analysis techniques for high field strength, high spatial resolution brain MRI.

Comparative neuroanatomical study of the amygdala and fear conditioning in Nigerian breeds of Artiodactyla: Sheep (Uda) and goats (Red Sokoto).

The aim of this study was to evaluate fear condition responses in sheep and goat and to relate this to the neuroarchitecture of their amygdala. Forty adult sheep (Uda breed) and 40 adult goats (Red Sokoto breed) were fear-conditioned by associating the sound of a car horn (neutral stimuli) with water spray (aversive stimuli) and the fear response was determined by direct observation of the behavior of the sheep and goats and measuring their flight distances and escape time. Eight groups were studied, each comprising of 10 animals (five sheep and five goats). Goats and sheep were tested alternately in the morning of every day of the week for three consecutive weeks, in which 4 days was used for habituation and 3 days for testing. Histologically, neurons in the central and basolateral complex of the amygdala were studied and analyzed using Nissl and golgi staines. Behaviorally, goats elicited an active avoidance response expressed as flight with concomitant intense flight distances (p < .001) compared to sheep. Although, sheep had larger brain parameters, it showed attenuated basolateral amygdala cytoarchitecture consistent with reduced fear perception and response. Goats had significantly more densely distributed pyramidal and spiny stellate neurons in the basolateral amygdala while sheep showed more non-pyramidal and aspiny neurons. These results provide interesting practical perspectives on how adaptions in the amygdala coincides with alterations in fear conditioning in domestic animals and may be the basis for the higher incidence of the sheep in automobile accidents than goats in developing countries especially Africa.