Biology subjects

Atapour, N.

Publications and source records attributed to Atapour, N..

5 recordsLinked to original sources

bioRxiv2025

Highly Consistent Anatomical Asymmetry in a Small Primate Brain: Left is Always Larger in the Marmoset Monkey

Although lateralisation of brain function is relatively common in animals, this is rarely accompanied by overt anatomical asymmetries. In primates, morphological differences between the cerebral hemispheres are well established in Hominidae but have been regarded as subtler or inconsistent in other species. Here we demonstrate that the left hemisphere is reproducibly larger than the right hemisphere in one of the smallest primates, the marmoset. This asymmetry develops postnatally, persists throughout adult life, and is found in individuals from genetically isolated colonies. Voxel-based morphometry reveals that the larger left hemisphere is primarily due to differences in the volume of cortical areas linked to social cognition. This result challenges the notion that the development and evolution of marked morphological asymmetry between the hemispheres is linked to the evolution of large brains.

neuroscience↗

bioRxiv2024

Giant pyramidal neurons of the primary motor cortex express vasoactive intestinal polypeptide (VIP), a known marker of cortical interneurons

Vasoactive intestinal polypeptide (VIP) is known to be present in a subclass of cortical interneurons that are involved in the disinhibition of excitatory pyramidal neurons. Here, using three different antibodies, we demonstrate that VIP is also present in the giant layer 5 pyramidal (Betz) neurons which are characteristic of the limb and axial representations of the marmoset primary motor cortex (cytoarchitectural area 4ab). No VIP staining was observed in smaller layer 5 pyramidal cells present in the primary motor facial representation (cytoarchitectural area 4c), or in premotor cortex (e.g. the caudal subdivision of the dorsal premotor cortex, A6DC), indicating the selective expression of VIP in Betz cells. The most intense VIP staining occurred in the largest Betz cells, located in the medial part of A4ab. VIP in Betz cells was colocalized with neuronal specific marker (NeuN) and a calcium-binding protein parvalbumin (PV). PV also intensely labelled axon terminals surrounding Betz cell somata. Whereas Betz cells bodies were located in layer 5, VIP-positive (VIP+) interneurons were more abundant in the superficial cortical layers. They constituted about 5-7% of total cortical neuronal population, with the highest density observed in area 4c. Our results demonstrate the expression of VIP in the largest excitatory neurons of the primate cortex, which may offer new functional insights into the role of VIP in the brain, and also provide opportunities for genetic manipulation of Betz cells.

neuroscience↗

bioRxiv2024

Distribution of calbindin-positive neurons across areas and layers of the marmoset cerebral cortex

The calcium-binding protein calbindin is selectively expressed in specific neuronal populations of the cerebral cortex, including major classes of inhibitory interneurons. We have charted the distribution of calbindin-positive (CB+) neurons across areas and layers of the entire marmoset cortex using a combination of immunohistochemistry, AI-based image segmentation, 3-dimensional reconstruction, and cytoarchitecture-aware registration. CB+ neurons formed 10-20% of the cortical neuronal population, occurring in higher proportions in areas corresponding to low hierarchical levels of processing, such as sensory cortices. Although CB+ neurons concentrated in the supragranular layers, there were clear trends in laminar distribution: the relative density in infragranular layers increased with hierarchical level, and the density in layer 4 was lowest in areas involved in sensorimotor integration and action planning. These results reveal new aspects of the cytoarchitectural organization of the primate cortex and demonstrate an efficient approach to mapping the full distribution of neurochemically distinct cell types throughout the brain, readily applicable to most mammalian species and parts of the nervous system.

neuroscience↗

bioRxiv2023

Rapid degeneration and neurochemical plasticity of the lateral geniculate nucleus following lesions of the primary visual cortex in marmoset monkeys

Lesions of the primary visual cortex (V1) cause retrograde neuronal degeneration, volume loss and neurochemical changes in the lateral geniculate nucleus (LGN). Here we characterise the timing of these processes, by comparing the LGN of adult marmoset monkeys following various recovery times after unilateral V1 lesions. Observations in NeuN-stained sections obtained from animals with very short (3 days) recoveries showed that the volume and neuronal density in the LGN ipsilateral to the lesions were similar to those in the contralateral hemispheres. However, neuronal density in the LGN lesion projection zones (LPZ) dropped rapidly thereafter, with a loss of [~]50% of the population occurring within a month of the lesions. This level of neuronal loss was then sustained for the remainder of the range of recovery times, up to >3 years post-lesion. In comparison, shrinkage of the LGN progressed more gradually, not reaching a stable value until 6 months post lesion. We also determined the time course of the expression of the calcium-binding protein calbindin (CB) in magnocellular (M) and parvocellular (P) layer neurons, a recently described form of neurochemical plasticity triggered by V1 lesions. We found that CB expression could be detected in surviving M and P neurons as early as 1 month after a lesion, with the percentage of neurons showing this neurochemical phenotype showing subtle changes over 6 months. Our study shows that there is a limited time window for any possible interventions aimed at reducing secondary neuronal loss in the visual afferent pathways following damage to V1.

neuroscience↗

bioRxiv2018

Neuronal distribution across the cerebral cortex of the marmoset monkey (Callithrix jacchus)

Using stereological analysis of NeuN-stained sections, we investigated neuronal density and number of neurons per column throughout the marmoset cortex. Estimates of mean neuronal density encompassed a greater than threefold range, from >150,000 neurons/ mm3 in the primary visual cortex to ~50,000 neurons/ mm3 in the piriform complex. There was a trend for density to decrease from posterior to anterior cortex, but also local gradients, which resulted in a complex pattern; for example, in frontal, auditory and somatosensory cortex neuronal density tended to increase towards anterior areas. Anterior cingulate, motor, premotor, insular and ventral temporal areas were characterized by relatively low neuronal densities. Analysis across the depth of the cortex revealed greater laminar variation of neuronal density in occipital, parietal and inferior temporal areas, in comparison with other regions. Moreover, differences between areas were more pronounced in the supragranular layers than in infragranular layers. Calculations of the number of neurons per unit column revealed a pattern that was distinct from that of neuronal density, including local peaks in the posterior parietal, superior temporal, precuneate, frontopolar and temporopolar regions. These results suggest that neuronal distribution in adult cortex result from a complex interaction of developmental/ evolutionary determinants and functional requirements.

neuroscience↗