VTHAND-CENTRED SPACE

Visuo-tactile cortical mechanims for a hand-centred spatial representation in humans

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 Obiettivo del progetto (Objective)

'When interacting with objects the brain needs to locate the limbs and the relevant visual information surrounding them. Studies on monkeys showed that information from different sensory modalities converges at the individual neurone level within a multisensory fronto-parietal network. This multisensory integration occurs within the space surrounding the body (peripersonal space) and has been linked to the sensory guidance of reaching and defensive movements, and localisation the limbs in space. In humans, only indirect behavioural evidence exists of a similar representation, and virtually nothing is known about the neuronal mechanisms of multisensory integration in peripersonal space. This project will provide the first direct evidence for the existence of an integrative visuo-tactile (VT) mechanism in the human brain by identifying the areas which implement it in hand-centred coordinates. We will use an innovative multimodal strategy involving complementary behavioural, functional magnetic resonance imaging (fMRI) and transcranial stimulation (TMS) approaches. We mean to employ cross-modal fMRI-adaptation to identify neuronal responses reflecting the multisensory integrative mechanisms of the VT peri-hand space representation. This method allows us to circumvent the limits of traditional fMRI analysis and go beyond the voxel-level resolution. We will investigate the plasticity of the VT peri-hand space during tool use and when prosthetic limbs are experienced as one’s own body part. Finally, TMS will reveal the link between the plasticity of the multisensory space representation and the motor system. This project has important clinical and industrial applications. Understanding the rapid plasticity of the multisensory peripersonal space will help to develop new rehabilitative strategies for amputees using advanced prosthetic limb devices. Our work will be important for optimising the control of virtual and robotic tools during fine manipulation (i.e. tele-surgery).'

Introduzione (Teaser)

How the human brain processes information remains a mystery even today. EU-funded researchers have managed to figure out how our brain processes visual and sensory information for spatial orientation and interaction with objects.

Descrizione progetto (Article)

Studies on monkeys revealed that sensory guidance of movement is enabled through hand-centred spatial representation in the brain. This enables them to perceive objects within the space around their body and interact accordingly though limb localisation.

Under the aegis of the project 'Visuo-tactile cortical mechanims for a hand-centred spatial representation in humans' (VTHAND-CENTRED SPACE), researchers successfully provided evidence of multi-sensory guidance for hand-centred spatial representation in humans.

A major issue with functional magnetic resonance imaging (fMRI) is identifying neuronal sub-populations involved in visual-selective response to near-hand spatial stimuli. This is because such neuronal sub-populations are intermingled with other multi-sensory neurons in the brain. To circumvent this, an experimental protocol called blood oxygen level-dependent (BOLD) adaptation was optimised.

Researchers combined BOLD with fMRI, and identified that the parietal and premotor areas in the brain process visual stimuli close to the hand for space representation.

Another major achievement is the demonstration of plasticity for peri-hand space representation even with prosthetic limbs. For this purpose, transcranial stimulation along with visual stimuli was used. Experiments revealed that like our human hand, the brain perceives the prosthetic limb as a body part. The location of the prosthetic limb is used as reference for representation of space surrounding the limb and helps in interaction with objects. A key finding is the discovery that hand-centred spatial representation involves the multi-sensory neurons in the ventral premotor and the posterior parietal cortex.

Project findings could also be extrapolated to represent motor interaction with other people using hand-centred representation of space. Future studies could now investigate this link further and identify areas of brain associated with specific functions. Applications include assessing extent of traumatic brain injury or developing more effective rehabilitation approaches.