Functional contributions of medial temporal lobe substructures to declarative memory
Memory permits us to bridge the past with the present, providing information about prior encounters with a stimulus or context that can serve to build predictive models for the present. At the neurobiological level, it is well established that the hippocampus and surrounding medial temporal lobe (MTL) cortices play an essential role in declarative memory––long-term memory for general facts and specific events. The MTL comprises several structures, including the hippocampal formation (dentate gyrus, CA fields, and subiculum), and surrounding entorhinal, perirhinal and parahippocampal cortices. These structures are likely to contribute differently to declarative memory, but the unique contribution of each structure remains debated. Using a combination of high-resolution fMRI and cortical flattening techniques that allow for differentiation of MTL substructures, our research explores functional specialization within the MTL based on anatomically guided hypotheses that rely on knowledge of the anatomical connectivity of the region with structures in neocortex, as well as information about the intrinsic connectivity within MTL. Isolating the function of each of these structures, as well as specifying how they interact, is central to understanding declarative memory processing and how damage or disease disrupts such processing.

Interactions between memory and attention in the medial temporal lobe
Attention can interact and guide memory by selecting the most relevant information for processing. Functional neuroimaging studies have revealed attention-dependent modulations in lateral cortical regions involved in the perceptual processing of visual information, but it is unclear how attention may modulate activity in MTL regions important for declarative memory processing. Encoding processes in the MTL may rely on top-down influence from goal-directed attentional mechanisms mediated by regions in frontal and parietal cortex. Modulation of MTL regions by goal-directed attention may help to enhance declarative memory encoding. Similarly, goal-directed attention might also enhance the successful expression of memory by influencing retrieval processes mediated by the MTL. Using high-resolution fMRI techniques, our research investigates how modulations in goal-directed attention affect activation in MTL subregions during both declarative memory encoding and retrieval specifically examining whether attention differentially affects memory processing subserved by specific MTL subregions.

Medial temporal lobe function in schizophrenia
Schizophrenia is typically associated with psychosis (hallucinations, delusions, thought disorder). However, cognitive deficits in memory, attention, and executive function, along with affective changes are also characteristics of the disease. Cognitive dysfunction in schizophrenia is associated with poor psychosocial function, and impairments in memory and attention are particularly unresponsive to treatment contributing to poor prognosis and disability. The impairments in declarative memory that are observed in schizophrenia are accompanied by correlated hippocampal abnormalities as revealed by functional neuroimaging studies. Further evidence from structural neuroimaging indicates that the CA3 region of the hippocampus may be particularly affected in the disease suggesting a specific role for this region in the pathology of schizophrenia. Employing high-resolution functional MRI techniques that allow differentiation between hippocampal subfields, our research seeks to directly investigate disruptions in MTL function (specifically CA3 function) that may be associated with structural abnormalities observed in schizophrenia. The ability to observe and characterize MTL function in schizophrenia is likely to facilitate understanding of how declarative memory is affected in the disease and may provide insight into new avenues for treatment and intervention.