Características eletrofisiológicas e estimulação binaural no desempenho e persistência da memória

Abstract

Little has been investigated about electrophysiological characteristics associated with memory persistence over time, as well as there are few studies investigating causal relationship between theta oscillations and memory, especially by auditory sensory pathway, a potential low-cost brain stimulation alternative. In order to contribute to the minimization of such gaps in knowledge, 4 experiments were carried out. The first one had a single group and repeated measures design, investigating electrophysiological characteristics related to memory success and failure, as well as to incidental encoding and recognition retrieval processes after a 10-minute interval. The electroencephalographic activity was recorded throughout the experiment. The second experiment, with a protocol similar to the first one, but without electroencephalographic recording, and with stimuli composed of item together with context (background color), aimed to investigate the forgetting rates over time, and to verify the feasibility of investigating electrophysiological characteristics related to memory persistence. This experiment had 2 independent groups that performed the recognition tasks at intervals of 10 minutes and 24 hours, or 24 and 72 hours, respectively. In the third and fourth experiments a binaural stimulation (EB) protocol at theta frequency (5 Hz) was partially replicated, in an online and another presential version, respectively. Both had 3 independent groups, referring to the types of stimulation received (binaural, monaural, pure tone). All groups performed an incidental encoding task of words associated with context (color or scene), and subsequent recognition task that evaluated memory for item, and item associated with context. The fourth experiment had an additional recognition session that occurred 7 days after the first one. The experiment 1 evidenced association between power in theta and alpha with encoding success, but did not present consistent evidence of this relation in retrieval process. In addition, the power in theta was lower in errors during encoding compared to errors during recall. The experiment 2 identified low forgetting rates between the intervals tested, demonstrating the need for future investigations with larger intervals. The experiments 3 and 4 did not show significant difference in performance between the types of stimulation in the experiments, except for the lower performance of monaural stimulation in relation to pure tone stimulation, in the presencial experiment.