Date of Award
Doctor of Philosophy (PhD)
The right prefrontal cortex and left parietal cortex have been implicated in the cognitive control of episodic memory retrieval. In addition, the relationship between executive function tasks and episodic retrieval indicate that they both depend on similar cognitive control processes. We recently proposed that theta oscillations represent interactions between brain systems for the control of episodic retrieval (reviewed in Nyhus & Curran, 2010). Top-down control of episodic retrieval is generally greater during source retrieval (e.g. retrieving contextual information such as the gender of the voice a word was studied in) than during item retrieval (e.g. retrieving whether a word was studied or not). In order to explore the role of theta oscillations in top-down control of episodic retrieval, three experiments were performed. Experiment 1 examined theta power and long-range synchronization between frontal and parietal regions for source retrieval. Experiment 2 examined theta power and long-range synchronization between frontal and parietal regions for item retrieval. And Experiment 3 provided a within-experiment comparison between item and source retrieval as well as exploring the relationship between individual differences in executive function updating and theta oscillations during episodic retrieval. In Experiment 1 and Experiment 3, which included source retrieval, frontal theta power was greater for old than new words from 500-800 ms. In all experiments, theta coherence was greater for old than new words and in Experiment 1 and Experiment 3, theta coherence was greater for incorrect than correct source judgments. In addition, executive function updating positively correlated with discrimination for item and source retrieval and there was a marginal negative correlation between executive function updating tasks and theta coherence. These results indicate that right frontal areas are engaged for source retrieval and that transient theta interactions in a fronto-parietal-hippocampal network are involved in the monitoring of episodic memory. In addition, the correlation with executive function updating indicates that monitoring the contents of working memory and monitoring the contents of long-term episodic memory retrieval engage similar executive control processes and that subjects who have better executive control are more efficient at monitoring the contents of episodic retrieval.
Nyhus, Erika Marie, "Theta Oscillations in Top-down Control of Episodic Memory Retrieval" (2010). Psychology and Neuroscience Graduate Theses & Dissertations. 7.