INVESTIGATION ON EVIDENCE FOR REPRESENTATIONAL VIEW OF THE BRAIN’S ORGANIZATION: SHARED NEURAL RESOURCES FOR LONG-TERM MEMORY AND PERCEPTION IN VISION

More than 5 million individuals in the United States have Alzheimer’s disease and by the year 2060 this number will almost triple. Patient care is currently estimated to cost around $290 billion per year. Alzheimer’s disease is known to cause deficits in memory and in perception, but the underlying mechanism by which these cognitive deficits arise is not well understood. Furthermore, treatments for patients with Alzheimer\u27s or related dementias are limited. One limitation is that we still have not attained a thorough understanding of how brain systems are functionally organized to produce cognition and behavior in the healthy brain. The objective of the presented research was to investigate how memory and perception are computed and organized in the brain. Based on case studies like patient H.M., traditional accounts of cognition explain memory function in terms of processes computed by separable brain regions. In contrast, the Representational-Hierarchical (R-H) Theory posits that brain regions are engaged in any cognitive task according to whether these areas contain the optimal representations. The R-H Theory postulates that the organization of cognition (i.e. memory and perception) in the brain is better understood in terms of a hierarchical continuum of representations, as opposed to anatomical modules for distinct cognitive processes. Here, I investigated whether recognition memory can be supported by structures outside of canonical memory regions (i.e., medial temporal lobe), in sensory areas known to mediate perception (e.g., visual cortex). In addition, I tested the hypothesis that cortical regions supporting recognition memory are the regions containing optimal representations of the to-be-remembered information and whether the regions that contain the optimal neural code for visual items are the same regions that signaled memory for the visual items. The outcomes of this dissertation have translational and theoretical significance. First, it will determine whether the R-H Theory provides a better explanation of how our brains give rise to human behavior. Second, it sheds light on whether the information content of a cortical region\u27s neural code determines what cognitive tasks it supports. Both of these advances may lay the groundwork for better understanding and treatment of memory-related dementias like Alzheimer’s disease