Memory, Delayed

The purpose of this study is to understand the neural mechanisms that support real world spatial navigation in humans using deep brain recordings and stimulation during virtual reality (VR), augmented reality, and real world memory tasks. We will determine the cognitive (i.e., memory) and behavioral (i.e., body, head, eye position and movement) factors that modulate deep brain activity and the consequent effects of memory-enhancing deep brain stimulation.

The proposed project seeks to elucidate memory processes and consolidation during sleep by leveraging the unique capability of direct recordings from the human brain at multiple levels of resolution-single neurons, localized neuronal assemblies, intracranial local field potentials-during rich behavioral tasks with real-life narratives and extracting neural features that relate to different aspects of episodic experience. The investigators will further probe causal mechanisms of consolidation by application of auditory and electrical stimulations during sleep and its effect on modulating memory processes.

Sensorineural hearing loss (SNHL) is among the most prevalent chronic conditions in aging and has a profoundly negative effect on speech comprehension, leading to increased social isolation, reduced quality of life, and increased risk for the development of dementia in older adulthood. Typical audiological tests and interventions, which focus on measuring and restoring audibility, do not explain the full range of cognitive difficulties that adults with hearing loss experience in speech comprehension. For example, adults with SNHL have to work disproportionally harder to decode acoustically degraded speech. That additional effort is thought to diminish shared executive and attentional resources for higher-level language processes, impacting subsequent comprehension and memory, even when speech is completely intelligible. This phenomenon has been referred to as listening effort (LE). There is a growing understanding that these cognitive factors are a critical and often "hidden effect" of hearing loss. At the same time, the effects of LE on the neural mechanisms of language processing and memory in SNHL are currently not well understood. In order to develop evidence-based assessments and interventions to improve comprehension and memory in SNHL, it is critical that the cognitive and neural mechanisms of LE and its consequences for speech comprehension are elucidated. In this project, the investigators adopt a multi-method approach, combining methods from clinical audiology, psycholinguistics, and cognitive neuroscience to address this gap of knowledge. Specifically, the investigators adopt a novel and innovative method of co-registering pupillometry (a reliable physiological measure of LE) and language-related event-related brain potential (ERP) measures during real-time speech processing to characterize the effects of clear speech (i.e., a listener-oriented speaking style that is spontaneously adopted to improve intelligibility when speakers are aware of a perception difficulty on behalf of the listener) on high-level language processes (e.g., semantic retrieval, syntactic integration) and subsequent speech memory in older adults with SNHL. This innovative work addresses a time-sensitive gap in the literature regarding the identification of objective and reliable markers of specific neurocognitive processes impacted by speech clarity and LE in age-related SNHL.