Emerging principles in functional representations of touch

Tamè, Luigi; Longo, Matthew R.

doi:10.1038/s44159-023-00197-6

Cited by 5 publications

(1 citation statement)

References 172 publications

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“…According to Serino & Haggard's (2010) multilevel model of somatosensory perception and body representation, MBRs housed in posterior parietal areas are continuously updated by the activity of the primary somatosensory cortex (SI). Importantly, this model accounts for the well-established finding that MBRs do not reflect the morphology of body parts accurately, but -to some extent -their distorted SI representations (Tamè et al, 2021, Tamè & Longo, 2023. Longo & Haggard's MBR model (Longo et al 2010, 2015 also considers the involvement of specific MBRs in somatosensory processing, namely the body model, the superficial schema and the body image, and similarly proposes that they serve distinct purposes.…”

Section: Introductionmentioning

confidence: 99%

Repetitive Somatosensory Stimulation Shrinks The Body Image

Azaroual-Sentucq,

Macchione,

Miller

et al. 2024

Preprint

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Current models of mental body representations (MBRs) indicate that tactile inputs feed several of them for different functions, implying that altering tactile inputs may affect MBRs differently. Here we tested this hypothesis by leveraging Repetitive Somatosensory Stimulation (RSS), known to improve tactile perception by modulating primary somatosensory cortex (SI) activity, and measured its effects over thebody image, thebody modeland thesuperficial schemain a randomized sham-controlled, double-blind cross-over study. Results show that RSS affected thebody image, participants perceiving their finger size as being smaller after RSS. While previous work showed increase of finger size perception after tactile anesthesia (Gandevia & Phegan 1999), these findings reveal that tactile inputs can diametrically modulate the body image. In contrast, RSS did not alter thebody modelorsuperficial schema. In addition, we report a novel mislocalization pattern, with a bias towards the middle finger in the distal phalanges that reverses towards the thumb in the proximal phalanx, enriching the known distortions of thesuperficial schema. Overall, these findings provide novel insights into the functional organization of MBRs and their relationships with somatosensory information. Reducing the perceived body size through RSS could be useful in helping treat body image disturbance.

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Section: Introductionmentioning

confidence: 99%

Repetitive Somatosensory Stimulation Shrinks The Body Image

Azaroual-Sentucq,

Macchione,

Miller

et al. 2024

Preprint

Self Cite

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On the Geometry of Somatosensory Representations in the Cortex

Saadon-Grosman,

Asher,

Loewenstein

2024

Preprint

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It is well-known that cortical areas specializing in the processing of somatosensory information from different parts of the body are arranged in an orderly manner along the cortex. It is also generally accepted that in the cortex, somatosensory information is initially processed in the primary somatosensory cortex and from there, it is hierarchically processed in other cortical regions. Previous studies have focused on the organization of representation at a level of a single or few cortical regions, identifying multiple body maps. However, the question of the large-scale organization of these different maps, and their relation to the hierarchical organization has received little attention. This is primarily because the highly convoluted shape of the cortical surface makes it difficult to characterize the relationship between cortical areas that are centimeters apart. Here, we used functional MRI to characterize cortical responses to full-body light touch stimulation. Our results indicate that the organization of both body representation and hierarchy is radial, with a small number of extrema that reign over a large number of cortical regions. Quantitatively computing the local relationship between the gradients of body and hierarchy maps, we show that the interaction between these two radial geometries, body representation and hierarchy in S1 are approximately orthogonal. However, this orthogonality is restricted to S1. Similar organizational patterns in the visual and auditory systems suggest that radial topography may be a common feature across sensory systems.Significance statementThe sensation of touch on our skin is represented in the brain as a map, where body parts are organized sequentially from head to toe. In the cerebral cortex, multiple body maps are distributed across numerous regions, processing signals at different hierarchical levels. Is there a large-scale organization of these body maps in the cerebral cortex? We show that all previously known body maps and their hierarchies are organized with a radial geometry. Similar radial geometry may also characterize the visual and auditory systems, indicating that radial geometry is a common organizational principle of sensory processing in the cortex.

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Transfer of Tactile Learning to Untrained Body Parts: Emerging Cortical Mechanisms

Frank

2024

Neuroscientist

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Pioneering investigations in the mid-19th century revealed that the perception of tactile cues presented to the surface of the skin improves with training, which is referred to as tactile learning. Surprisingly, tactile learning also occurs for body parts and skin locations that are not physically involved in the training. For example, after training of a finger, tactile learning transfers to adjacent untrained fingers. This suggests that the transfer of tactile learning follows a somatotopic pattern and involves brain regions such as the primary somatosensory cortex (S1), in which the trained and untrained body parts and skin locations are represented close to each other. However, other results showed that transfer occurs between body parts that are not represented close to each other in S1—for example, between the hand and the foot. These and similar findings have led to the suggestion of additional cortical mechanisms to explain the transfer of tactile learning. Here, different mechanisms are reviewed, and the extent to which they can explain the transfer of tactile learning is discussed. What all of these mechanisms have in common is that they assume a representational or functional relationship between the trained and untrained body parts and skin locations. However, none of these mechanisms alone can explain the complex pattern of transfer results, and it is likely that different mechanisms interact to enable transfer, perhaps in concert with higher somatosensory and decision-making areas.

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Emerging principles in functional representations of touch

Cited by 5 publications

References 172 publications

Repetitive Somatosensory Stimulation Shrinks The Body Image

Repetitive Somatosensory Stimulation Shrinks The Body Image

On the Geometry of Somatosensory Representations in the Cortex

Transfer of Tactile Learning to Untrained Body Parts: Emerging Cortical Mechanisms

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