Abstract:
In our day-to-day interactions, we use our own motor representations to understand the
actions of those around us. How we relate to others is an important part of life.
Understanding motor representations can help us to better learn and grow, conduct
relationships, assess intent, and increase the quality of our daily lives. Further,
understanding how we acquire motor representations can help us better understand this
mechanism as we use it. The acquisition of these motor representations can be described
by functional changes in the brain as well as structural changes in the brain. The
relationship between these expressions of plasticity is not well understood. In this study,
I sought to establish if a mediation equation would explain the results of an action
recognition study. Participants were taught a novel one ball juggling cascade task either
by physically performing it (nonvisual motor group) or by means of observation
(nonmotor visual group). The group who physically performed the task learned
completely without visual input ensured by blindfolds. The observation group was taught
a visual task with physical practice. Magnetic resonance imaging (MRI) scans were
taken before, during, and after training. The functional magnetic resonance imaging
(fMRI) results represented functional changes between time points. These results showed
the changes in action recognition as a result of training. A voxel-based morphometry
(VBM) analysis, performed on the structural MRI images, represented the structural
changes. These results were overlaid to determine regions which spatially overlap for
both functional and structural changes, with the head of the hippocampus as the only
brain region which demonstrated both. A region of interest (ROI) analysis was
conducted on the individual images for the head of the hippocampus to obtain mean
intensities. These means were entered into Baron and Kenny’s (1986) mediation
equations to determine if structural changes act as a mediator on the relationship between
time and functional changes. While the equations for the relationship between time on
functional changes and time on structural changes were significant, the relationship
between structural changes on functional changes was not significant. Therefore the
requirements of Baron and Kenny (1986) were not upheld, leading to the conclusion that
structural changes do not act as a mediator in the relationship between time and
functional changes.
