Biology subjects

Kurcyus, K.

Publications and source records attributed to Kurcyus, K..

5 recordsLinked to original sources

bioRxiv2026

Directed cortical connectivity inferred from neural energy metabolism

Complex cognition depends on directed communication between brain regions. Yet, resting functional MRI resolves only undirected associations, and inferring the direction of signalling has proven difficult across the whole brain. Because synaptic transmission is metabolically asymmetric, with the postsynaptic neuron bearing most of the energetic cost, regional energy demand carries a physical signature of the direction of communication. Here, we show that this signature organizes the human cortex into a reproducible directed hierarchy, in which sensory and attentional systems preferentially drive higher-order networks, while the default mode and control networks act as principal receivers. Critically, the inferred directionality is independently predicted by two cellular markers of neuronal energy demand, regional mitochondrial density and laminar cytoarchitecture, linking macroscale information flow to its cellular substrate. The directed architecture recapitulates the known feedforward and feedback organization of visual pathways and, using an average CMRGlc template, extends to functional MRI acquired without PET. By grounding communication direction in energy metabolism, Metabolic Connectivity Mapping bridges correlative and effective connectivity and offers a scalable, biologically interpretable framework for mapping directed communication across the human brain.

neuroscience↗

bioRxiv2024

Simultaneous quantification of oxygen and glucose consumption during visual stimulation in the human cortex

The brain is fueled by oxidative glucose metabolism, yet activation may uncouple oxygen and glucose consumption. Because the two have never been measured simultaneously in humans across conditions, we combined multiparametric quantitative BOLD (mqBOLD) imaging with functional PET (fPET) during rest and visual stimulation. Participants (n = 12 with complete data) were scanned on an integrated PET/MR system during alternating six-minute blocks of checkerboard stimulation and fixation, with continuous arterial sampling. Cerebral metabolic rates of oxygen (CMRO2) and glucose (CMRglc), and cerebral blood flow (CBF) were quantified per condition and combined into the oxygen-to-glucose index (OGI = CMRO2/CMRglc), where six indicates fully oxidative glucose use. At rest, OGI was 4.6-5.0 in task-responsive visual regions and 4.9 elsewhere. Stimulation increased CMRglc (12-26%) and CBF (10-22%) more than CMRO2; (3-10%, not significant), lowering OGI by 12% in metabolically defined visual regions. Beyond the visual cortex, OGI fell 8%, significantly in 47% of cortical regions. The mechanisms differed, however: glycolytic upregulation in visual cortex (CBF, CMRglc up) versus oxidative downregulation elsewhere (CBF, CMRO2; down; CMRglc unchanged). Simultaneous imaging thus shows that focal activation shifts metabolism toward glycolysis across the cortex, with consequences for interpreting metabolic contrasts outside engaged regions.

neuroscience↗

bioRxiv2023

An energy costly architecture of neuromodulators for human brain evolution and cognition

Humans spend more energy on the brain than any other species. However, the high energy demand cannot be fully explained by brain size scaling alone. We hypothesized that energy-demanding signaling strategies may have contributed to human cognitive development. We measured the energy distribution along signaling pathways using multimodal brain imaging and found that evolutionarily novel connections have up to 67% higher energetic costs of signaling than sensory-motor pathways. Additionally, histology, transcriptomic data, and molecular imaging independently reveal an upregulation of signaling at G-protein coupled receptors in energy-demanding regions. We found that neuromodulators are predominantly involved in complex cognition such as reading or memory processing. Our study suggests that the upregulation of neuromodulator activity, alongside increased brain size, is a crucial aspect of human brain evolution.

neuroscience↗

bioRxiv2019

State and trait characteristics of anterior insula time-varying functional connectivity

The human anterior insula (aINS) is a topographically organized brain region, in which ventral portions contribute to socio-emotional function through limbic and autonomic connections, whereas the dorsal aINS contributes to cognitive processes through frontal and parietal connections. Open questions remain, however, regarding how aINS connectivity varies over time. We implemented a novel approach combining seed-to-whole-brain sliding-window functional connectivity MRI and k-means clustering to assess time-varying functional connectivity of aINS subregions. We studied three independent large samples of healthy participants and longitudinal datasets to assess inter- and intra-subject stability, and related aINS time-varying functional connectivity profiles to dispositional empathy. We identified four robust aINS time-varying functional connectivity modes that displayed both "state" and "trait" characteristics: while modes featuring connectivity to sensory regions were modulated by eye closure, modes featuring connectivity to higher cognitive and emotional processing regions were stable over time and related to empathy measures.

neuroscience↗

bioRxiv2019

The physiological effects of non-invasive brain stimulation fundamentally differ across the human cortex

Non-invasive brain stimulation reliably modulates brain activity and symptoms of neuropsychiatric disorders. However, stimulation effects substantially vary across individuals and brain regions. We combined transcranial magnetic stimulation (TMS) and functional magnetic resonance imaging (fMRI) to investigate the neuronal basis of inter-individual and inter-areal differences after TMS. We found that stimulating sensory and cognitive areas yielded fundamentally heterogeneous effects. Stimulation of occipital cortex enhanced brain-wide functional connectivity and biophysical modeling identified increased local inhibition and enhanced forward-signaling after TMS. Conversely, frontal stimulation decreased functional connectivity, associated with local disinhibition and disruptions of both feedforward and feedback connections. Finally, we identified brain-wide functional integration as a predictive marker for these heterogeneous stimulation effects in individual subjects. Together, our study suggests that modeling of local and global signaling parameters of a target area will improve the specificity of non-invasive brain stimulation for research and clinical applications.

neuroscience↗