The present study aims to characterize and modulate motor imagery abilities in individuals with aphantasia. The investigators will characterize the neurophysiological and physiological underpinnings of mental imagery abilities in participants with aphantasia by investigating several indices of motor imagery abilities and comparing them to participants with typical mental imagery abilities. The investigators will investigate whether non-invasive brain stimulation applied to the primary motor cortex improves mental imagery abilities in participants with aphantasia.
The investigators will recruit 20 participants with aphantasia and 20 participants with typical mental imagery capacities (no-aphantasia groups). Participants in both groups will complete a 3-hour visit for inclusion and baseline measurements (Visit 1) which will include neurophysiological, autonomic nervous system, cognitive and behavioral measures. Participants in the aphantasia group will complete 2 additional visits to receive active and sham tDCS sessions (Visit 2 and 3), according to a randomized, double-blind, sham-controlled, crossover design. Mental training will be done concurrently with tDCS using a sequential finger tapping-task (Truong et al., 2022). Participants will receive the instructions of trying to imagine themselves performing the motor task, by feeling their fingers moving as if they were actually moving it (kinesthetic modality of motor imagery). Visits will be separated by at least 7 days.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
BASIC_SCIENCE
Masking
TRIPLE
Enrollment
40
Participants will receive a session of active HD-tDCS at a current intensity of 4 mA for a duration of 15min. The placement of electrodes will be determined to specifically target the primary motor cortex (4 x 1 montage with the anode over C4). During the stimulation, participants will be engaged in a mental training task (sequential finger tapping-task).
Participants will receive a session of sham HD-tDCS, which will be delivered following the same procedures as active HD-tDCS but the intensity of the current will be set at 4mA during the 30 first seconds at the beginning of the 15-min period of the stimulation, and equal to 0 mA for the reminding period of stimulation to simulate the tingling sensation often experienced by individuals during active stimulation. The placement of electrodes will be determined to specifically target the primary motor cortex (4 x 1 montage with the anode over C4). During the stimulation, participants will be engaged in a mental training task (sequential finger tapping-task).
Centre Hospitalier le Vinatier
Bron, France
RECRUITINGGains in motor performance following mental training
Gains in motor performance following mental training combined with tDCS will be measured using a sequential finger tapping-task. Gains following training will be expressed as a percentage of the baseline performance.
Time frame: 2 times: immediately before tDCS (baseline) and immediately after tDCS
Motor corticospinal excitability at rest and during kinesthetic motor imagery
Motor corticospinal excitability will be assessed with single-pulse transcranial magnetic stimulation (TMS) applied over the primary motor cortex representation of the non-dominant hand. Using electromyography, we will measure the peak-to-peak mean amplitude of motor evoked potentials (MEPs, measured in mV) in the contralateral first dorsal interosseous muscle both at rest and during kinesthetic motor imagery.
Time frame: 1 time at baseline (Visit 1), in both groups
Heart rate variability
Heart rate variability, including respiratory sinus arrhythmia measures, expressed in milliseconds (ms), will be assessed at rest and during kinesthetic motor imagery by recording the heart rate using three electrodes placed in the left chest area. These electrodes will be connected to the Biopac MP150 system and monitored with the Acqknowledge software
Time frame: through study completion, an average of 1 month
Skin conductance
Amplitude of electrodermal response will be measured at rest, during actual movements and during kinesthetic motor imagery using the Biopac MP150 system with the Acqknowledge software. The ratio between amplitudes during imagined/actual movements will be computed (expressed in percent).
Time frame: through study completion, an average of 1 month
Mental imagery abilities
Mental imagery abilities in different sensory modalities will be measured as scores at the following questionnaires: Vividness of Visual Imagery Questionnaire (VVIQ; range 16-80)
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Time frame: 1 time at baseline, in both groups
Mental imagery abilities
Mental imagery abilities in different sensory modalities will be measured as scores at the following questionnaires: the Kinesthetic and Visual Imagery Questionnaire (KVIQ; range 20-100).
Time frame: 1 time at baseline, in both groups
Mental imagery abilities
Mental imagery abilities in different sensory modalities will be measured as scores at the following questionnaires: the Movement Imagery Questionnaire-Revised (MIQ-R; range 14-98)
Time frame: 1 time at baseline, in both groups
Mental imagery abilities
Mental imagery abilities in different sensory modalities will be measured as scores at the following questionnaires: the Test of Ability in Movement Imagery (TAMI; range 0-24)
Time frame: 1 time at baseline, in both groups
Mental imagery abilities
Mental imagery abilities in different sensory modalities will be measured as scores at the following questionnaires: Plymouth Sensory Imagery Questionnaire (Psi-Q; range 0-70)
Time frame: 1 time at baseline, in both groups
Source monitoring performance
Source monitoring performance will be evaluated using a specific source monitoring task . Source-monitoring accuracy scores (range 0-100) will be calculated as proportions of accurate source attributions for each source
Time frame: 1 time at baseline, in both groups
Implicit motor imagery capacities
Implicit motor imagery capacities will be measured using a hand laterality judgment task . The percentage of correct response at the task will be calculated (range 0-100%).
Time frame: 1 time at baseline, in both groups
Performance of time-to-contact estimation
Performance will be measured using a specific time-to-contact (TTC) task. A TTC task involves temporal prediction in that the task requires a participant to predict the moment at which an event will occur given past sensory information (e.g., an auditory stimuli). The estimation of TTC requires determining the moment of contact (TTCa). The analysis of performance is based on BIAS quantification, which measures the average difference between individual estimation and TTCa
Time frame: 1 time at baseline, in both groups