Intracranial EEG analysis during spatial memory tasks: the role of high frequency oscillations

Treball de fi de grau en Biomèdica Tutor: Adrià Tauste Historically, declarative memory has been indirectly studied using spatial navigation experiments in rodents. Theories of hippocampal function expanded with the discovery of neural ensembles (place cells, grid cells) able to depict current spatial representations of the physical world. Place cell coupling to theta rhythm, or theta phase precession, first related neural firing to brain oscillations. Replay of past place cell sequences during short brain oscillations (sharp waves) established a basis for memory encoding after learning, but the involvement of grid cells in replay is unknown. We hereby present evidence that replay of rodent grid cells during the sharp-wave ripple complex in awake spatial navigation tasks is fairly low, contrarily to replay in place cells. Overcoming the technical limitations faced in this study will help to unveil part of the hippocampal contribution to memory processes. We also present a pilot study with an epilepsy patient, one of the first attempting detection of high frequency oscillations during cognitive processes. Future more task-design controlled research might help to identify behavioral correlates of high frequency oscillations and might possibly unveil their role in cognitive function and memory processes.