Description

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 and group assignment will be determined. There will be 3 groups:

1. Visuo-proprioceptive realignment (perceptual learning)
2. Visuomotor adaptation (motor learning)
3. Control (no learning)

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 (perceptual learning, motor learning, or no learning, depending on group assignment), 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.