Biology subjects

Tamietto, M.

Publications and source records attributed to Tamietto, M..

4 recordsLinked to original sources

bioRxiv2026

Preserved brain hierarchy supports residual vision without awareness after visual cortex damage

Damage to the primary visual cortex causes loss of conscious vision, yet some patients retain the ability to respond to stimuli despite reporting no visual experience. Why similar lesions produce such different behavioral phenotypes remains unclear. While research to date has focused primarily on spared pathways that bypass V1, here we asked whether these divergent outcomes are also linked to the brain's intrinsic functional architecture. In the largest resting-state fMRI cohort of patients with unilateral V1 damage reported to date, we quantified information sharing between regions across cortical and subcortical parcels in blindsight-positive and blindsight-negative patients, as well as in age-matched healthy controls. Despite comparable lesions, the two patient groups displayed distinct hierarchical patterns on the cortex: B+ patients preserved a sensory-to-association organization as in healthy controls, whereas B- patients exhibited a marked flattening of this hierarchy. The effect was driven by abnormally low shared-information coupling within unimodal cortices and scaled continuously with single-subject behavioral blind-field detection performance. A thalamic region consistent with the pulvinar, linking the contralesional visual cortex and the frontal eye field, discriminated B+ from B- patients. These findings highlight the system-level consequences of V1 damage supporting blindsight, suggesting that the unimodal-transmodal axis might track not only global states of consciousness, but also whether sensory information can guide behavior without awareness.

neuroscience↗

bioRxiv2026

Generalisation of training-induced recovery in occipital stroke: neurochemical and fMRI correlates

BACKGROUNDDamage to the early visual cortex after an occipital stroke typically results in the loss of conscious vision in the contralateral hemifield. Nonetheless, extensive perceptual training can restore visual motion discrimination in the blind-field. Here, we assessed, in a cohort study, whether improvements transferred to an untrained Gabor detection task and whether awareness within the blind field increased. We then explored the neural underpinnings of these changes. METHODSEighteen participants (6 female; aged 24-74 years; >6 months post-stroke) completed at least six months of visual rehabilitation in their blind field. Rehabilitation consisted of participants practicing a two-alternative, forced-choice, motion discrimination task using random dot stimuli, five days/week, at home, at one or two non-overlapping, locations in their blind-field. Each participant also completed two in-lab visits: one pre- and one post-training. A subset returned to the lab for a follow-up visit three months later to assess persistence of recovery. In addition to the trained task, an untrained, drifting-Gabor detection task was used to measure transfer of learning and changes in visual awareness at the trained locations. To investigate neural mechanisms underlying generalisation of improvements, participants completed MRI scanning at each lab visit. Magnetic resonance spectroscopy (MRS) was used to quantify GABA and glutamate concentrations in the ipsilesional motion sensitive area, hMT+, and a control voxel in the sensorimotor cortex. Functional MRI was conducted to assess BOLD signal changes in hMT+ and across the rest of the brain during passive viewing of high contrast Gabor stimuli in the blind field. RESULTSParticipants showed significant improvements in motion direction discrimination (trained task) between pre- and post-training in-lab visits, which generalised to improvements in Gabor detection and awareness (untrained task). Reduced GABA and glutamate in ipsilesional hMT+ was linked to improved Gabor detection, but not awareness. Increased BOLD signals in hMT+ and dorsolateral prefrontal cortex also correlated with improved Gabor detection, while awareness changes were linked to higher-level areas associated with visual attention in the contralesional prefrontal cortex (area 46) and inferior parietal lobule. CONCLUSIONSLong-term visual rehabilitation using a global motion discrimination task generalised to enhance both detection and awareness of moving Gabors within the blind field of occipital stroke survivors. Improvements were supported by selective changes in brain regions known to be involved in motion perception and attention respectively, suggesting that a broad network supports recovery, which could be targeted to enhance outcomes.

neuroscience↗

bioRxiv2025

Beyond Reorganization: Intrinsic cortical hierarchies constrain experience-dependent plasticity in sensory-deprived humans

Innate cortical organisation and postnatal sensory experience interact dynamically to shape the functional architecture of the human brain. Using naturalistic stimulation, functional gradient analyses, and comparative approaches in congenitally blind, congenitally deaf, and typically developed individuals, we investigated how intrinsic hierarchical structures and sensory experiences influence cortical organisation. Our findings demonstrate that the principal functional gradients spanning from unimodal sensory to transmodal association cortices are consistently preserved across all groups, suggesting a robust genetically determined cortical scaffold. Nonetheless, congenital sensory deprivation selectively reshapes the geometry of modality-specific gradients, characterised by reduced functional differentiation within sensory-deprived cortical regions. These geometric contractions promote experience-driven plastic reorganization, enabling deprived sensory areas to establish enhanced functional connectivity with transmodal and non-deprived sensory cortices. Critically, this reorganisation aligns systematically with pre-existing cortical gradients, highlighting intrinsic hierarchical constraints that guide experience-dependent plasticity. Moreover, sensory-deprived regions exhibiting heightened connectivity actively engage in processing structured perceptual information from intact modalities, reflecting specific feature-driven cross-modal adaptations. Collectively, these results underscore a fundamental duality in cortical organisation: innate hierarchical principles impose constraints on cortical architecture, while sensory experience drives adaptive refinement, demonstrating the brains intrinsic capacity for flexible functional reconfiguration in response to sensory deprivation.

neuroscience↗

bioRxiv2017

Gender-specific brain activation during visual art perception

The human body is the most common object of pictorial representation in western art. The goal of this study was to probe its evolutionary basis of visual art perception by investigating neural markers of gender-specific brain activity triggered by paintings of male and female images. Our results show significant activity in brain areas other than those recently associated with visual arts perception. Novel findings concern participant-general as well as gender specific brain activity. Although our participants were fully aware that they were viewing artworks, the inferior parietal lobule - known for its role in the perception of emotional body images - and the somatosensory cortex - which is related to touch - were selectively active for female body paintings in all participants. The most interesting finding as regards gender was that the sight of female bodies activates the subgenual anterior cingulate cortex in males, an area known to subserve autonomic arousal. In contrast, in females the sight of the male body activated reward and control related parts of the dorsal anterior cingulate cortex. This supports the notion that basic evolutionary processes operate when we view body images, also when they are paintings far removed from daily experience.

neuroscience↗