Neural Basis of Sensory and Motor Learning: Functional Connections

Human perception of hand position is multisensory. The brain can estimate it visually, from an image on the retina, and proprioceptively, from receptors in the joints and muscles. The sensory inputs determining these percepts are subject to changes in environmental factors (e.g., lighting) and internal factors (e.g., movement history). Multisensory integration of visual and proprioceptive estimates gives us flexibility to cope with such changes. For example, washing dishes with the hands immersed in water creates a spatial misalignment between vision and proprioception, as water refracts light. The brain resolves this conflict by realigning visual and/or proprioceptive estimates of hand position, and also by adjusting motor commands (visuomotor adaptation). The neural basis of these adaptive processes is poorly understood. The purpose of this study is to find out if multisensory and visuomotor learning are accompanied by changes in resting state connectivity between sensory regions of the brain and other areas.

The first session is a familiarization session for functional magnetic resonance imaging (fMRI) and the behavioral task, and is expected to last 30-40 minutes. Subjects will first fill out screening forms to confirm the answers given during the initial screening, and the Edinburgh handedness inventory to quantify their handedness. If subjects are still eligible, subjects will lie in a mock scanner and perform the functional task: Subjects will have their left index finger taped to a wooden stick, and an experimenter from the team will manipulate the finger with the stick outside of the scanner. Subjects will respond to the different movements by pressing buttons with their right hand. Subjects will also be introduced to the behavioral task, which is performed at an apparatus in the room next to the scanner: Subjects sit in front of a touchscreen and point to targets seen in a mirror.

If subjects are interested in moving on to the main session at this point, the main session will be scheduled.

The main session will take about 2 hours. Subjects will first fill out the MR safety screening form. Subjects will then perform some practice trials of the behavioral task to remind the subject of the task. This will be followed by the first resting state scan (12 min), a 20-30 minute baseline block of the behavioral task (no learning), a second resting state scan (12 min), the 20-30 minute learning block of the behavioral task, and a third resting state scan (12 min). Finally, the subject will do the functional task in the scanner (same as familiarization session, 12 min. total) and an anatomical scan (~6 minutes). The session will conclude with some questions about the subject's subjective experience of the procedures.

Inclusion criteria

• Ages of 18-45 years old
• Right-handed.
• Free of Covid symptoms in week preceding testing.

Exclusion criteria

• metallic, mechanical, or magnetic implants;
• are claustrophobic, or are unable to remain still for long periods of time;
• use an intra-uterine device (IUD) whos MR compatibility has not been established.
• Women who are pregnant or think they might be pregnant will also be excluded, as effects of fMRI on the unborn are not known.
• People who have a BMI over 30 will be excluded as it may be uncomfortable or impossible to lay in the MRI scanner and reach the button box.
• Potential subjects will be excluded if they have any neurological disorders, or orthopedic or pain conditions in the upper limbs.
• Investigators will also exclude subjects who do not have normal vision, or corrected-to-normal vision with contacts, or the imaging center does not have a pair of MRI compatible glasses that fits their prescription.
• investigators will invite subjects to reschedule if they have any of the common Covid symptoms within the last week and if they haven't been fully vaccinated or obtained a negative Covid test within the past 4 days. If they don't believe they can meet these criteria on another date, they will be excluded.
• After giving their consent, participants may be excluded during the study if they are unable to perform the tasks or follow instructions.