Towards a somatosensory theory of handwriting

The NeuroSchool PhD Program of Aix-Marseille University (France) has launched its annual calls for PhD contracts for students with a master's degree in a non-French university. 

This project is one of the proposed projects. Not all proposed projects will be funded, check our website for details.

State of the art: The use of sensory signals in motor control has long been debated. In most theoretical models, sensory feedback is typically represented by a single arrow/loop (Miall & Wolpert 1996), despite different neurophysiological pathways. However, the specific roles of somatosensory and visual feedback in motor control remain unclear. In the specific case of handwriting, which is a highly complex cognitive and motor skill, the dominant view is that vision is the main sense involved. Given that handwriting requires the precise coordination of several arm joints, and that proprioception is critical for interjoint coordination arm reaching (Ghez et al. 1995), an alternative, somatosensory-based hypothesis may be considered. The main goal of this PhD project is to advance our theoretical understanding of handwriting control by specifying the roles of somatosensory signals for planning, execution and learning processes. To this end, the approach is to compare healthy individuals to patients with massive yet specific somatosensory deficits due to a rare sensory neuropathy (due to congenital, PIEZO2 or ASIC3 genetic mutations, or acquired, autoimmune diseases). We expect impaired executive control in patients, but relatively spared motor planning and learning due to compensation by the visual and prefrontal systems. In addition to the expected theoretical shift toward a somatosensory modelling of handwriting, the assessment of patients’ performance and adaptive strategies will be instrumental to inform clinicians (neurologists, occupational and physio-therapists) and optimize learning as well as readaptation procedures.  

Methods: First, we will conduct detailed behavioral assessments of handwriting (based on Alhaddad et al. 2024) in patients and matched controls to determine the processes which depend on somatosensory feedback. At this point, 11 patients have agreed to participate: although this number is limited, it is at least 5 times greater than in most studies with such rare patients. A motion-capture device will be used to acquire kinematic data during handwriting. Specific statistical tests will be used to infer about differences between patients and controls. Clinical and detailed sensory examination will be performed by collaborators to strengthen the project. The second phase will tackle neurophysiological underpinnings of handwriting by using EEG as already done in our group (Zuo et al., in revision). We will quantify the oscillatory dynamics of neural signals associated to tracing movements of varying difficulty.  

Expected results: At the behavioral level, we predict differences between patients and controls on variables reflecting executive control. At the neural level, we predict that patients will recruit more midfrontal theta processes than matched controls to monitor handwriting, and that beta oscillations over the posterior electrodes will be more strongly coupled with movement kinematics, reflecting higher reliance on visual feedback in patients.  

Feasibility:  Seed funding has been obtained to buy equipment and hire a Master student to adjust the behavioral protocol and acquire preliminary data (ICR NeuroMarseille, 2026). A CPP proposal has been submitted in February by the CRPN (2026-A00277-44). Other opportunities are being explored for a larger project between the LAMA team (CRPN), which has internationally-recognized expertise on the behavioral and neural bases of handwriting, and the DynamiCC team (ISM) which has a long tradition of studying the role of somatosensory signals in motor control by comparing healthy humans and rare patients, thanks to an ongoing collaboration with local clinicians at APHM and abroad. 

Within Aix Marseille Université, NeuroMarseille brings together 8 research laboratories and NeuroSchool, a graduate school in neuroscience, to increase the attractiveness of the university, international collaborations, interdisciplinarity, links with the clinical and industrial worlds and the integration of students into professional life. 

Launched in July 2018, NeuroSchool unifies and harmonizes the training of the third year of the Bachelor of Life Sciences (Neuroscience track), the Master's and the PhD in Neuroscience. 

• Expected candidate profile : Students from Neuroscience, Psychology, Movement Science, or Bio-Engineering are welcome. Proficiency in human research, English written and oral communication, and programming (e.g. Python, R or Matlab) are required.