Biology subjects

Tucciarelli, R.

Publications and source records attributed to Tucciarelli, R..

4 recordsLinked to original sources

bioRxiv2024

Shaping the developing homunculus: the roles of deprivation and compensatory behaviour in sensory remapping

Some of the most dramatic examples of neuroplasticity in the human brain follow congenital sensory deprivation, though we have limited understanding of the plasticity mechanisms driving such large-scale remapping. Hand loss due to congenital limb differences (CLD) offers a unique temporal dissociation of developmental neuroplasticity mechanisms: While sensory deprivation is congenital, compensatory motor behaviours develop progressively across childhood. Using paediatric neuroimaging and semi-ecological behavioural analysis in children (5-7 years old) and adults (>25 years old) with unilateral upper-limb CLD, we studied deprivation- and use-dependent plasticity in the deprived primary somatosensory cortex and beyond. We reveal that global remapping, encompassing the entire sensory homunculus, is established early and maintained in adulthood. We demonstrate that deprivation-driven homeostatic plasticity can drive this global remapping, with Hebbian-based compensatory learning further contributing to inter-individual differences both in childhood and adulthood. Our findings emphasise the early establishment and stability of cortical maps, despite extensive daily-life behavioural adaptation.

neuroscience↗

bioRxiv2023

Does ipsilateral remapping following hand loss impact motor control of the intact hand?

What happens once a cortical territory becomes functionally redundant? We addressed brain and behavioural adaptations for the intact hand in individuals with a missing hand. Previous studies reported increased ipsilateral activity in the somatosensory territory of the missing hand (i.e., remapping) in acquired amputees, but not in individuals with a congenitally missing hand (one-handers). It is unclear whether remapping in amputees involves recruiting more neural resources to support the intact hand, and whether such activity is increased in tasks that demand greater motor control. We investigated sensorimotor learning and neural representation of the intact hand in one-handers and amputees using a multi-finger configuration task, as well as univariate and multivariate fMRI. We found that ipsilateral activity increased with motor demand - but only in the amputees group. However, these changes did not reflect behavioural differences. The representation of the finger configurations, as revealed by multivariate analysis, was stronger in amputees and closer to the typical representation found in controls contralateral hand territory, compared to one-handers. This collaborative contra-ipsilateral activity may reflect the intact hands efference copy. One-handers struggled to learn difficult finger configurations, but this did not translate to differences in univariate or multivariate activity relative to controls. Together with a supplementary structural white matter analysis, our results suggest that enhanced activity in the missing hand territory may not reflect intact hand function. Instead, we suggest that plasticity is more restricted than generally assumed and may depend on the availability of homologous pathways acquired early in life. Significant StatementWe studied whether brain resources in the missing-hand territory support demanding intact hand motor control in people who were born with one hand or lost a hand later in life. We found that amputees had increased activity in the brain area used for the missing hand, but no improvement in the performance of their intact hand. This collaborative contra-ipsilateral activity may reflect the intact hands efference copy. One-handers showed slight deficits while learning to perform complex motor movements, but no brain activity differences in the missing hand territory, compared to controls. Our results suggest that brain plasticity is limited and may depend on early life experiences.

neuroscience↗

bioRxiv2019

Reconstructing neural representations of tactile space

Psychophysical experiments have demonstrated large and highly systematic perceptual distortions of tactile space. We investigated the neural basis of tactile space by analyzing activity patterns induced by tactile stimulation of nine points on a 3 x 3 square grid on the hand dorsum using functional magnetic resonance (fMRI). We used a searchlight approach within pre-defined regions of interests (ROIs) to compute the pairwise Euclidean distances between the activity patterns elicited by tactile stimulation. Then, we used multidimensional scaling (MDS) to reconstruct tactile space at the neural level and compare it with skin space at the perceptual level. Our reconstructions of the shape of skin space in contralateral primary somatosensory (SI) and motor (M1) cortices reveal that it is distorted in a way that matches the perceptual shape of skin space. This suggests that early sensorimotor areas are critical to processing tactile space perception.\n\nSignificant StatementHere, we show that the primary somatosensory (SI) and motor (M1) cortices, rather than higher-level brain areas, are critical to estimating distances between tactile stimuli on the hand dorsum. By combining functional magnetic resonance (fMRI), Procrustes alignment, and multidimensional scaling, we reconstructed the shape of skin space in the brain. Strikingly, the shape of the skin that we reconstructed from neural data matches the distortions we found at the behavioral level, providing strong evidence that early sensorimotor areas are critical for the construction of tactile space. Our work therefore supports the view that tactile distance perception is computed at lower level in the somatosensory system than is usually supposed.

neuroscience↗

bioRxiv2019

The representational space of observed actions

Categorizing and understanding other peoples actions is a key human capability. Whereas there exists a growing literature regarding the organization of objects, the representational space underlying the organization of observed actions remain largely unexplored. Here we examined the organizing principles of a large set of actions and the corresponding neural representations. Using multiple-regression representational similarity analysis of fMRI data, in which we accounted for variability due to major action-related features (body parts, scenes, movements, objects), we found that the semantic dissimilarity structure was best captured by patterns of activation in the lateral occipitotemporal cortex (LOTC) and the left posterior inferior parietal lobe (IPL). Together, our results demonstrate that the organization of observed actions in the LOTC and the IPL resembles the organizing principles used by participants to classify actions behaviorally, in line with the view that these regions are crucial for accessing the meaning of actions.

neuroscience↗