Objective

Using a block design BOLD-fMRI , we want to investigate the connectivity in brain regions when two motor responses are performed in the same time. The designs will be replicated using EEG and MEG to understand the time course of the activated brain network better. It will allow us to map the brain processes involved in sensorimotor integration and attentional sharing.

Study population

60 right-hand dominant, adult healthy volunteers

Design

Two experiments will be performed using MEG, EEG and fMRI techniques. Both experiments will use visuo-motor control tasks. Two motor responses (given by two fingers of the dominant hand) will be simultaneously performed. Experiment 1 will use single motor tasks; Experiment 2 will use dual motor tasks. In both experiments, the attention demands will vary with the execution mode of the motor outputs (competitive or cooperative). In competitive tasks, the visual stimuli will be used to perform two independent motor outputs. In cooperative tasks, the visual stimuli will be used to perform two coupled motor outputs. The effect of the execution mode on brain connectivity will be isolated comparing competitive and cooperative tasks. The sensory information must be associated to the motor command to perform a given motor task: this process is called sensorimotor integration. With both experiments, we will be able to dissociate the network connectivity linked to:

• sensorimotor integration demands for focused attention in a single task,
• sensorimotor integration demands for divided attention in a dual motor task.

After subjects have been properly trained to perform the tasks, they will undergo fMRI scanning MEG and EEG recording. Subjects will perform the tasks presented pseudo-randomly during six sets of 5-minute sessions. We will record their muscular activity via EMG surface electrodes.

Outcome measures

The primary outcomes are the task-dependent functional connectivity (for fMRI) between areas and coherence (for MEG and EEG) of cerebral sources relative to performance of the tasks. The force control of two fingers in the same time would elicit blood oxygen level dependent (BOLD) signal and electrical brain activity variations in the network involved in manual dexterity. We are interested in studying the connectivity between the homologous motor areas of the two hemispheres, and between prefrontal cortex and parietal cortex, to understand sensorimotor integration processes during competitive and cooperative dual tasks. As a second measure, we are interested in analyzing coherence between MEG-EMG and EEG-EMG signals.

• INCLUSION CRITERIA:

Subjects age from 18 to older.

Subjects must be right-hand dominant (Edinburgh Handedness Quotient greater than 60)

Subjects willing to abstain from caffeine or alcohol for 48 hours prior to the fMRI scanning and MEG/EEG recording

EXCLUSION CRITERIA:

Subjects with any abnormal findings on neurological exam

Subjects who are pregnant (as determined by positive urine pregnancy test)

Subjects with any findings on the MRI safety questionnaire which prevents them from safely undergoing an MRI scan

Subjects with metallic dental fillings which are likely to cause MRI artifacts

Subjects with any history of brain tumor, stroke, head trauma or a vascular malformation as obtained by history or from imaging studies

Subjects with any history of a severe medical condition, such as cardiovascular disease, which would prevent them from lying flat for up to 120 minutes

Subjects without the capacity to give informed consent

Subjects with claustrophobia or other restrictions which prevent them from undergoing a scan in a confined space for up to 90 minutes

Subjects who are left-handed