Looking for the neural basis of memory

Eye movements reflect specific memory-processing events and occur at the speed of cognition and neurophysiological activity. Eye movements therefore are better suited for identifying brain–behavior–cognition linkages in episodic memory than are coarse-grained behaviors. Invasive neurophysiological recordings in conjunction with eye-movement tasks have clarified the role of sharp-wave ripples and theta oscillations in episodic memory. Memory neuroscientists often measure neural activity during task trials designed to recruit specific memory processes. Behavior is championed as crucial for deciphering brain–memory linkages but is impoverished in typical experiments that rely on summary judgments. We criticize this approach as being blind to the multiple cognitive, neural, and behavioral processes that occur rapidly within a trial to support memory. Instead, time-resolved behaviors such as eye movements occur at the speed of cognition and neural activity. We highlight successes using eye-movement tracking with in vivo electrophysiology to link rapid hippocampal oscillations to encoding and retrieval processes that interact over hundreds of milliseconds. This approach will improve research on the neural basis of memory because it pinpoints discrete moments of brain–behavior–cognition correspondence. Memory neuroscientists often measure neural activity during task trials designed to recruit specific memory processes. Behavior is championed as crucial for deciphering brain–memory linkages but is impoverished in typical experiments that rely on summary judgments. We criticize this approach as being blind to the multiple cognitive, neural, and behavioral processes that occur rapidly within a trial to support memory. Instead, time-resolved behaviors such as eye movements occur at the speed of cognition and neural activity. We highlight successes using eye-movement tracking with in vivo electrophysiology to link rapid hippocampal oscillations to encoding and retrieval processes that interact over hundreds of milliseconds. This approach will improve research on the neural basis of memory because it pinpoints discrete moments of brain–behavior–cognition correspondence. the process by which encoded information is stabilized into a durable memory trace. In most experiments that focus on encoding or retrieval, short delays minimize consolidation. the process by which sensory inputs and internal states are rapidly stored in memory. the ability to recall past experiences, which can be used to inform memory-based decision making, planning, or future simulation. It relies on multiple processes including encoding, storage or consolidation, and retrieval. high-frequency (~30–120 Hz) synchronous neuronal activity observed in the local field potential. the process by which patterns of neural activity present during initial learning are activated again at a later point in time. the process by which previously encoded information is reactivated, thus allowing memory to influence behaviors such as eye movements, recognition judgments, and recall responses. highly synchronous neural complexes observed in the hippocampus that consist of a strong deflection in the local field potential (sharp wave) and concurrent high-frequency oscillations (ripples, 80–140 Hz in humans). low-frequency synchronous neuronal activity that is implicated in memory processing and long-range communication between brain regions. Distinct forms of theta occur along the hippocampal long axis in humans, with relatively slow theta (~3 Hz) in anterior hippocampus and fast theta (~8 Hz) in posterior hippocampus. memory tasks often use distinct study, delay, and test phases. Tests differ in the cues that guide retrieval. Recognition tasks use studied stimuli as memory probes, and subjects discriminate studied from novel. Cued recall tasks use partial retrieval cues (e.g., one of two simultaneously presented stimuli). Subjects try to generate missing associates. Free-recall tasks do not provide external retrieval cues. After encoding lists, subjects must use internally generated cues for retrieval.