Biology subjects

Nasseef, M. T.

Publications and source records attributed to Nasseef, M. T..

2 recordsLinked to original sources

bioRxiv2026

Acute lysergic acid diethylamide induces a time-dependent shift toward hippocampal control of default mode network reorganization

Background Classical psychedelics induce profound changes in brain function, yet the temporal organization of these effects remains incompletely understood. Methods We investigated the effects of acute lysergic acid diethylamide (LSD) on large-scale brain connectivity in nine male Long-Evans rats using resting-state functional magnetic resonance imaging. Following a 15-min baseline acquisition, rats received LSD (500 g/kg, i.p.), and imaging continued during two consecutive 15-min post-injection periods. Network reorganization was assessed using independent component analysis (ICA), seed-to-voxel mapping, stationary seed-to-seed connectivity, dynamic graph-based metrics, and dynamic causal modeling. Results LSD produced widespread but regionally heterogeneous changes across default mode network related, cortical, striatal, thalamic, sensory, and limbic systems. During the early post-injection window, ICA revealed a predominance of increased functional coupling, while dynamic analyses showed prominent fluctuations in hippocampal coupling strength and medial frontal network centrality. Dynamic causal modeling identified a false discovery rate-corrected reduction in retrosplenial-to-infralimbic influence, accompanied by a broader descriptive pattern of reduced posterior- and hippocampal-to-frontal coupling. During the later window, ICA showed a relative shift toward connectivity decreases, while complementary analyses revealed more selective hippocampal and parahippocampal involvement. Conclusions Across complementary analyses, acute LSD induced a temporally structured reorganization of brain hierarchy, characterized by an early weakening of directed cortical interactions followed by a later shift toward hippocampal-centered network control. These findings identify a dynamic shift in effective network organization and provide a mechanistic framework for psychedelic-induced default mode network reconfiguration.

neuroscience↗

bioRxiv2019

Mapping the living mouse brain neural architecture: strain specific patterns of brain structural and functional connectivity

Mapping the structural and functional brain connectivity fingerprints became an essential approach in neurology and experimental neuroscience because network properties can underlie behavioral phenotypes. In mouse models, revealing strain related patterns of brain wiring have a tremendous importance, since these animals are used to answer questions related to neurological or neuropsychiatric disorders. C57BL/6 and BALB/cJ inbred strains are primary \"genetic backgrounds\" for brain disease modelling and for testing therapeutic approaches. Nevertheless, extensive literature describes basal differences in the behavioral, neuroanatomical and neurochemical profiles of the two strains, which raises the question whether the observed effects are pathology specific or depend on the genetic background. Here we performed a systematic comparative exploration of brain structure and function of C57BL/6 and BALB/cJ mice via Magnetic Resonance Imaging (MRI). We combined voxel-based morphometry (VBM), diffusion MRI and high resolution fiber mapping (hrFM) and resting state functional MRI (rs-fMRI) and depicted brain-wide dissimilarities in the morphology and \"connectome\" features in the two strains. Particularly C57BL/6 animals show bigger and denser frontal cortical areas, cortico-striatal tracts and thalamic and midbrain pathways, and higher density of fibers in the genu and splenium of the corpus callosum. These features are fairly reflected in the functional connectograms that emphasize differences in \"hubness\", frontal cortical and basal forbrain connectivity. We demonstrate strongly divergent reward-aversion circuitry patterns and some variations of the default mode network features. Inter-hemispherical functional connectivity showed flexibility and adjustment regarding the structural patterns in a strain specific manner. We further provide high-resolution tractograms illustrating also inter-individual variability across inter-hemispherical callosal pathways in the BALB/cJ strain.

neuroscience↗