Abstracts

Rationale: The Morris water maze has been used to study memory in animals, but similar tools for human research are limited. Computer-based simulations of three-dimensional space offer experimental environments where spatial cognition can be assessed. Functional MRI (fMRI) has been used extensively to investigate brain function in a variety of tasks neurophysiology. The goal of this project is to use fMRI to characterize the neural correlates of spatial memory function in humans performing in a computer-based replica of the Morris water maze.Methods: The virtual Morris water maze is a computer-based navigable environment based on the traditional water maze. It consists of a circular pool of opaque liquid containing a hidden platform. Participants first undergo learning trials to memorize the location of the hidden platform with reference to unique visual cues located at cardinal points. Next, probe trials are conducted within an fMRI scanner. Participants search for the hidden platform unaware that it is no longer present. Blood oxygen level dependent functional MRI data is acquired during the probe trials and contrasted with data acquired during a visible target navigation task.Results: The neural network mediating spatial memory appears to be centered at the retrosplenial cortex with interconnections between the right parietal cortex and hippocampus. The initial analysis was therefore limited to the retrosplenial cortex. Comparing the BOLD signal during the probe trials and visible target tasks yielded a small statistically significant cluster. (Figure 1) This data was extracted and used as a regressor in second level analyses, which showed covariance in the right parietal region and the right hippocampus. (Figure 2)Conclusions: This study demonstrates the feasibility of using computer-based virtual environments to study spatial navigation in humans. Our findings further describe functional interconnectedness between the retrosplenial cortex and both the right parietal region and right hippocampus during a spatial navigation task. This method therefore appears to be a potential model to explore the neural mechanisms associated with spatial memory processing in adults.