Biology subjects

Sampaio-Baptista, C.

Publications and source records attributed to Sampaio-Baptista, C..

6 recordsLinked to original sources

bioRxiv2026

When More Is Not Better: Increased Motor Cortex Recruitment In Older Adults Is Associated With Performance Decline During High-Demand Cognitive-Motor Tasks

Age-related changes in brain structure and function lead to reorganisation in neural activity during cognitive-motor tasks. A central question is whether increased brain activity in older adults reflects compensatory mechanisms that help maintain performance, or inefficient recruitment due to neural dedifferentiation. In this context, the Compensation-Related Utilization of Neural Circuits Hypothesis (CRUNCH) proposes that older adults recruit more brain resources as task demands rise, but reach a limit beyond which this no longer supports performance. This study examined brain activity changes in older adults in response to increased cognitive-motor task demands. Twenty-one right-handed older adults performed an Action Selection (AS) task with three difficulty levels during functional MRI. Behavioural performance declined with increasing task difficulty. Whole-brain analyses revealed that higher task complexity was associated with increased activation in sensorimotor and prefrontal regions, particularly the left dorsolateral prefrontal cortex (DLPFC) and left premotor cortex (PMd). Importantly, higher activity in subcortical regions (caudate nucleus) was associated with better performance at lower difficulties, while greater activation in cortical motor areas (primary motor cortex (M1), and the supplementary motor area (SMA)) was linked to worse performance at high difficulty. Additionally, greater increases in sensorimotor activity (M1, PMd, DLPFC) across difficulties correlated with greater declines in performance, supporting the notion of inefficient resource recruitment. Together, the findings support a novel hypothesis, compatible with CRUNCH, of a subcortical to cortical shift (SCOS) with increasing cognitive-motor demand, where the transition from efficient subcortical processing to over-reliance on cortical motor areas may contribute to performance decline in ageing.

neuroscience↗

bioRxiv2023

Ablation of oligodendrogenesis in adult mice alters brain microstructure and activity independently of behavioural deficits

Oligodendrocytes continue to differentiate from their precursor cells even in adulthood, a process that can be modulated by neuronal activity and experience. Yet, our understanding of the functional role of adult oligodendrogenesis remains limited. Previous work has indicated that conditional ablation of oligodendrogenesis in adult mice can lead to learning and memory deficits in a range of behavioural tasks. Our results, reported here, have replicated a key finding that learning to run on a complex wheel with unevenly spaced rungs is disrupted by ablation of oligodendrogenesis. However, using ex vivo MRI (MTR and DTI), we also found that ablating oligodendrogenesis by itself alters brain microstructure, independent of behavioural experience. Furthermore, in vivo EEG recording in behaviourally naive mice with ablated oligodendrogenesis revealed altered brain activity in the form of increased EEG power density across a broad frequency range. Together, our data indicate that disrupting the formation of new oligodendrocytes directly alters brain microstructure and activity. This suggests a role for adult oligodendrogenesis in the maintenance of brain function and indicates that task-independent changes to brain structure and function might contribute to the learning and memory deficits associated with oligodendrogenesis ablation.

neuroscience↗

bioRxiv2020

Heterogeneous relationships between white matter and behaviour

Several studies have established specific relationships between White Matter (WM) and behaviour. However, these studies have typically focussed on fractional anisotropy (FA), a neuroimaging metric that is sensitive to multiple tissue properties, making it difficult to identify what biological aspects of WM may drive such relationships. Here, we carry out a pre-registered assessment of WM-behaviour relationships in 50 healthy individuals across multiple behavioural and anatomical domains, and complementing FA with myelin-sensitive quantitative MR modalities (MT, R1, R2*). Surprisingly, we only find support for predicted relationships between FA and behaviour in one of three pre-registered tests. For one behavioural domain, where we failed to detect an FA-behaviour correlation, we instead find evidence for a correlation between behaviour and R1. This hints that multimodal approaches are able to identify a wider range of WM-behaviour relationships than focusing on FA alone. To test whether a common biological substrate such as myelin underlies WM-behaviour relationships, we then ran joint multimodal analyses, combining across all MRI parameters considered. No significant multimodal signatures were found and power analyses suggested that sample sizes of 40 to 200 may be required to detect such joint multimodal effects, depending on the task being considered. These results demonstrate that FA-behaviour relationships from the literature can be replicated, but may not be easily generalisable across domains. Instead, multimodal microstructural imaging may be best placed to detect a wider range of WM-behaviour relationships, as different MRI modalities provide distinct biological sensitivities. Our findings highlight a broad heterogeneity in WMs relationship with behaviour, suggesting that variable biological effects may be shaping their interaction. HighlightsO_LIPre-registered testing of microstructural imaging across modalities (FA, MT, R1, R2*) to test WM-behaviour relationships. C_LIO_LIPartial support for FA-behaviour relationships hypothesised based on previous literature. C_LIO_LIMultimodal approaches can help detect WM-behaviour relationships that are not detected with FA alone. C_LIO_LISample sizes of 40 to 200 may be needed to detect myelin-behaviour relationships in joint multimodal analyses. C_LIO_LIVariable biological effects may be shaping WM-behaviour relationships. C_LI

neuroscience↗

bioRxiv2020

Neurofeedback fMRI in the motor system elicits bi-directional changes in activity and white-matter structure in the healthy adult human brain

Neurofeedback can be used to alter brain activity and is therefore an attractive tool for neuromodulation in clinical contexts. Different contexts might call for different patterns of activity modulation. For example, following stroke, alternative therapeutic strategies could involve up or down-regulation of activity in the ipsilateral motor cortex. However, effects of such strategies on activity and brain structure are unknown. In a proof of concept study in healthy individuals, we showed that fMRI neurofeedback can be used to drive activity up or down in ipsilateral motor cortex during hand movement. Given evidence for activity-dependent white matter plasticity, we also tested effects of activity modulation on white matter microstructure using diffusion tensor imaging (DTI). We show rapid opposing changes in corpus callosum microstructure that depend on the direction of activity modulation. Bidirectional modulation of ipsilateral motor cortex activity is therefore possible, and results not only in online changes in activity patterns, but also in changes in microstructure detectable 24 hours later.

neuroscience↗

bioRxiv2019

Skill acquisition increases myelination and strengthens functional connectivity in the sensorimotor circuit of the adult rat

The effects of skill acquisition on whole-brain structure and functional networks have been extensively investigated in humans but have yet to be explored in rodents. Forelimb reaching training in rodents results in well-established focal functional and structural reorganization within the motor cortex (M1) and cerebellum, indicating distributed alterations in both structure and function. However, it is unclear how local alterations in structure and function relate to distributed learning-related changes across motor networks. Here we trained adult rats in skilled reaching and used multimodal whole-brain in vivo MRI to assess both structural and functional plasticity over time.\n\nWe detected increases in a myelin-related MRI metric in white matter, cortical areas, and to a lesser extent in the cerebellum, paralleled by strengthened functional connectivity between M1 and cerebellum, possibly reflecting a decrease in cerebellum inhibition over M1. Skill learning therefore leads to myelin increases in pathways that connect sensorimotor regions, and in functional connectivity increases between areas involved in motor learning, all of which correlate with performance. These findings closely mirror previous reports of network-level changes following motor learning in humans and underlines the correspondence between human and rodent brain circuits for motor learning, despite important differences in the anatomy of physiology of movement circuits between species.

neuroscience↗

bioRxiv2019

Experience-related alterations in white matter structure and gene expression in adult rats

White matter (WM) plasticity during adulthood is a recently described phenomenon by which experience can shape brain structure. It has been observed in humans using diffusion tensor imaging (DTI). However, it remains unclear which mechanisms drive or underlie WM plasticity in adulthood. Here, we combined DTI and mRNA expression analysis and examined the effects of somatosensory experience in adult rats. Somatosensory experience resulted in differences in WM and grey matter structure. C-FOS mRNA expression, a marker of cortical activity, in the barrel cortex correlated with the structural WM measures, suggesting that WM plasticity is activity-dependent. Analysis of myelin-related genes revealed higher myelin basic protein expression in WM, while genome-wide RNA sequencing analysis identified 134 differentially-expressed genes regulating proteins involved in functions related to cell proliferation and differentiation, neuronal activity modulation and regulation of myelination. In conclusion, the macroscale measures of WM differences identified in response to somatosensory experience are supported by molecular evidence, which strongly suggest myelination as, at least, one of the underlying mechanisms.

neuroscience↗