Two-Dimensional Population Receptive Field Mapping of Human Primary Somatosensory Cortex

Asghar, Michael; Sanchez-Panchuelo, Rosa; Schluppeck, Denis; Francis, Susan

doi:10.1007/s10548-023-01000-8

Cited by 2 publications

References 47 publications

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Cortical activations associated with spatial remapping of finger touch using EEG

Alouit,

Gavaret,

Ramdani

et al. 2024

Cerebral Cortex

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The spatial coding of tactile information is functionally essential for touch-based shape perception and motor control. However, the spatiotemporal dynamics of how tactile information is remapped from the somatotopic reference frame in the primary somatosensory cortex to the spatiotopic reference frame remains unclear. This study investigated how hand position in space or posture influences cortical somatosensory processing. Twenty-two healthy subjects received electrical stimulation to the right thumb (D1) or little finger (D5) in three position conditions: palm down on right side of the body (baseline), hand crossing the body midline (effect of position), and palm up (effect of posture). Somatosensory-evoked potentials (SEPs) were recorded using electroencephalography. One early-, two mid-, and two late-latency neurophysiological components were identified for both fingers: P50, P1, N125, P200, and N250. D1 and D5 showed different cortical activation patterns: compared with baseline, the crossing condition showed significant clustering at P1 for D1, and at P50 and N125 for D5; the change in posture showed a significant cluster at N125 for D5. Clusters predominated at centro-parietal electrodes. These results suggest that tactile remapping of fingers after electrical stimulation occurs around 100–125 ms in the parietal cortex.

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Cortical activations associated with spatial remapping of finger touch using EEG

Alouit,

Gavaret,

Ramdani

et al. 2024

Cerebral Cortex

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Cutting a nerve of the hand alters the organisation of digit maps in primary somatosensory cortex

Weber,

Marshall,

Timircan

et al. 2024

Preprint

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Hand nerve transection injuries precipitate a variety of reorganisational changes in both the peripheral and central nervous systems. Surgical repair restores the continuity of severed nerves, yet regenerating fibres establish new connections without topographical guidance, rearranging the branching architecture of peripheral nerves in the hand. In non-human primates, forelimb nerve transection and repair dramatically alters the otherwise orderly and highly conserved organisation of the digit maps in primary somatosensory areas 3b and 1. Digit-map organisation becomes patchwork and highly variable. Although without compelling evidence, these same reorganisational changes are presumed to occur in humans and to have significant functional implications for patient recovery. In the current study, we evaluate these assumptions. Functional MRI is used to characterise the fine-grained organisation of digit responses in the primary somatosensory cortex in twenty-one patients with nerve transection injuries and thirty healthy controls. Both univariate dice overlap coefficients and state-of-the-art multivariate representational distances are used to quantify the extent and pattern of interdigit response separability in primary somatosensory cortex. Our results reveal significant differences between patients and controls. The fine-grained organisation of the primary somatosensory cortex is altered in nerve repair. Average dice coefficients reveal significantly increased interdigit response overlap. These effects are specific to the hemisphere contralateral to the nerve-repaired hand, reflecting inputs from reinnervated digits, and are more robust within the cortical zones of the repaired nerves. Nerve repair also alters the relative functional structure of the primary somatosensory cortex, changing the otherwise stereotypical pattern of interdigit response separability seen in healthy controls. Unexpectedly, these later alterations manifest bilaterally, as maps for the healthy hand of patients also show an atypical pattern of interdigit response separability. Our findings provide the first compelling evidence for altered digit maps following nerve repair in humans, bridging results from animal models. Nonetheless, the clinical significance of the changes we observe remains unclear. No reliable relationships between fMRI measures of cortical reorganisation and behavioural measures of functional impairments are observed. Altered digit maps are not found to correlate with impairments in touch localisation or with broader measures of functional impairment as captured by sensory Rosen scores.

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Two-Dimensional Population Receptive Field Mapping of Human Primary Somatosensory Cortex

Cited by 2 publications

References 47 publications

Cortical activations associated with spatial remapping of finger touch using EEG

Cortical activations associated with spatial remapping of finger touch using EEG

Cutting a nerve of the hand alters the organisation of digit maps in primary somatosensory cortex

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