Understanding the neural mechanisms underlying the benefits of unitization on associative memory in young and older adults

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Abstract. By 2050, roughly 83.7 million individuals in the U.S. alone will be over the age of 65. Within this population, memory declines are at the forefront of age-related cognitive complaints. Associative memory, or the ability to link together multiple pieces of information, is especially vulnerable to aging. Associative memory is central to everyday memory function, supporting everything from our ability to remember face-name associations to links between medicines and their daily dosages. As such, there is an urgent need to identify methods that can improve associative memory in older adults. Our long-term goal is to identify effective, theory-driven, evidence-based approaches for enhancing associative memory in older adults. The objective of this application is to elucidate the mechanism underlying the cognitive and neural benefits of unitization on associative memory. The overarching hypothesis is that unitization operates by creating representations of object pairs that mirror how single items are encoded in memory, and does not require conscious, strategic implementation [nor is it dependent on semantic relatedness]. Instead we posit that unitization can be effectively induced through the way in which information is presented to a person. We expect that unitization will result in shifts from hippocampal-based associative processing to cortical-based item processing, with similar shifts observed throughout the memory network, whereby patterns of unitization-related activity are more similar to item-level processing than to associative processing. Additionally, if unitization operates by forming an integrated representation of item pairs, then the unitized ensemble should be both encoded and subsequently retrieved as a single ensemble, with retrieval processes mirroring that of item retrieval. This hypothesis is based on a) findings that unitized information is processed by item-processing regions in young adults and b) the ability of Gestalt principles to transform the representations of individual items into a holistic representation. Finally, we posit that unitization is not limited to binding amongst co-occurring statically presented items, but can occur across temporally presented visual and auditory information as well. The approach is innovative because it directly applies a well-established theory of perception to ameliorate the burden of binding in associative memory processing, with the goal of enhancing associative memory in aging. The approach employs cutting-edge multivariate and network connectivity analyses to test the neurocognitive mechanism underlying the application of unitization to associative memory at all stages of memory. The proposed research is significant because it tests a method for enhancing memory in aging that can be employed across a range of applications absent of subject-generated strategy deployment. In doing so, the work is a critical step in elucidating the flexibility of neural processing across the lifespan to the betterment of memory function. By identifying ways to improve memory function in young and older adults, this work has the potential to 1) enhance other cognitive processes, 2) improve the quality of life in aging, and 3) help dissociate normal aging from early signs of dementia.