Biology subjects

Alexandros Goulas

Publications and source records attributed to Alexandros Goulas.

3 recordsLinked to original sources

bioRxiv2016

Cytoarchitectonic similarity is a wiring principle of the human connectome

Understanding the wiring diagram of the human cerebral cortex is a fundamental challenge in neuroscience. Elemental aspects of its organization remain elusive. Here we examine which structural traits of cortical regions, particularly their cytoarchitecture and thickness, relate to the existence and strength of inter-regional connections. We use the architecture data from the classic work of von Economo and Koskinas and state-of-the-art diffusion-based connectivity data from the Human Connectome Project. Our results reveal a prominent role of the cytoarchitectonic similarity of supragranular layers for predicting the existence and strength of connections. In contrast, cortical thickness similarity was not related to the existence or strength of connections. These results are in line with findings for non-human mammalian cerebral cortices, suggesting overarching wiring principles of the mammalian cerebral cortex. The results invite hypotheses about evolutionary conserved neurobiological mechanisms that give rise to the relation of cytoarchitecture and connectivity in the human cerebral cortex.

Neuroscience↗

bioRxiv2016

Intrinsic functional architecture of the macaque dorsal and ventral lateral frontal cortex

Investigations of the cellular and connectional organization of the lateral frontal cortex (LFC) of the macaque monkey provide indispensable knowledge for generating hypotheses about the human LFC. However, despite numerous investigations, there are still debates on the organization of this brain region. In vivo neuroimaging techniques such as resting-state fMRI can be used to define the functional circuitry of brain areas producing results largely consistent with gold-standard invasive tract-tracing techniques and offering the opportunity for cross-species comparison within the same modality. Our results using resting-state fMRI from macaque monkeys to uncover the intrinsic functional architecture of the LFC corroborate previous findings and inform current debates. Specifically, we show that i) the region in the midline and anterior to the superior arcuate sulcus is divided in two areas separated by the posterior supraprincipal dimple; ii) the cytoarchitectonically defined area 6DC/F2 contains two connectional divisions; and, iii) a distinct area occupies the cortex around the spur of the arcuate, updating what was previously proposed to be the border between dorsal and ventral motor/premotor areas. Within the ventral LFC specifically, the derived parcellation clearly suggests the presence of distinct areas i) with a somatomotor/orofacial connectional signature (putative area 44), ii) with an occulomotor connectional signature (putative frontal eye fields), and iii) premotor areas possibly hosting laryngeal and arm representations. Our results illustrate in detail the intrinsic functional architecture of the macaque LFC, thus providing valuable evidence for debates on its organization.

Neuroscience↗

bioRxiv2015

Principles of ipsilateral and contralateral cortico-cortical connectivity in the mouse

Structural connectivity among cortical areas provides the substrate for information exchange in the brain and is characterized by the presence or absence of connections between specific areas. What principles govern this cortical wiring diagram? Here, we investigate the relation of physical distance and cytoarchitecture with the connectional architecture of the mouse cortex. Moreover, we examine the relation between patterns of ipsilateral and contralateral connections. Our analysis reveals a mirrored and attenuated organization of contralateral connections when compared to ipsilateral connections. Both spatial proximity and cytoarchitectonic similarity of cortical areas are related to the presence or absence of connections. Notably, our analysis demonstrated that these factors conjointly relate better to cortico-cortical connectivity than each factor in isolation, and that the two factors contribute differently to ipsilateral and contralateral connectivity. Distance is more tightly related to the presence or absence of ipsilateral connections, but its contribution greatly diminishes for contralateral connections, while the contribution of cytoarchitectonic similarity remains stable. Our results, conjointly with similar findings in the cat and macaque cortex, suggest that a common set of principles underlies the macroscale wiring of mammalian brains.

Neuroscience↗