J. Andrew Hartshorn and Dr. Brock Kirwan, Department of Psychology
I began work in the BYU Memory and Cognition Lab in the fall of 2009. Under the direction of Dr. Kirwan I was fortunate enough to be involved in a variety of projects using different testing methodologies. My first project examined the ability of people to distinguish between similar memories (pattern separation). A subsequent study utilized EEG tests to determine subjects’ abilities to rate the confidence of their memories of presented words.
The final study I worked on was the one for which I was awarded an ORCA grant. This study sought to test a hypothesis presented by Toner and colleagues (2008), in which they demonstrated deficiencies in older adults on a memory task involving the disambiguation of old and similar visual stimuli. It was predicted that this deficiency was a result of cell loss in the dentate gyrus. To determine if this was actually the case we utilized fMRI scanning and AFNI (a neuroimaging tool) to calculate individual volumes of the dentate gyrus and other pertinent memory areas (including the hippocampus, parahippocampal gyrus, and subiculum).
All scanning took place at the University of Utah. As of the end of April 2011 we had run nine subjects. In order to be a study participant, subjects had to be at least sixty-five years of old with no history of dementia. Furthermore, subjects had to go through an in-depth screening before being able to receive an MRI. One of the most challenging aspects of the study was recruiting subjects that fit in this category. We put up fliers in the Salt Lake City area and throughout Provo, and even though we offered payment for participation, only a handful of people responded to our fliers. In each scanning session, participants received a resting state fMRI and after leaving the scanner we administered a behavioral memory task using a laptop.
In this task, participants viewed a series of everyday objects and decided if the object was new to the experiment (novel), had been presented before (repeat), or was new but similar to a previously seen stimulus. The task consisted of studying pictures of various objects, and then seeing a new set of objects and reporting whether each object was new, old, or similar (same object, but a different color, for example).
The first step in analyzing the data was loading the brain scans into AFNI (Analysis of Functional Neuroimages). Dr. Kirwan trained me in using AFNI to locate and trace the hippocampus, subiculum, parrahipocampal gyrus, and most importantly, the dentate gyrus. This is a difficult, time-intensive process requiring patience and attention to details. After working for several months we were able to calculate the volume of subjects’ dentate gyri and correlate this with their performance on the aforementioned behavioral task. Upon initial analysis we did affirm our hypothesis–smaller dentate gyrus volumes correlated with decreased performance on a memory task.
To conclude, our initial hypothesis was proven to be true. To strengthen this finding it will be necessary to recruit more study participants. We anticipate the study to be completed by the end of the year. Understanding the aging brain and its relationship to memory is important as it may lead to greater understanding and treatment of neurodegenerative diseases, such as Alzheimer’s.