Encoding of visual-spatial information in working memory is more challenging than retrieval: Evidence from EEG and Virtual Reality study
Open Access
- Author:
- Jaiswal, Niharika
- Graduate Program:
- Kinesiology
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- November 18, 2009
- Committee Members:
- Semyon Slobounov, Thesis Advisor/Co-Advisor
Semyon Slobounov, Thesis Advisor/Co-Advisor
Karl Maxim Newell, Thesis Advisor/Co-Advisor
William Ray, Thesis Advisor/Co-Advisor - Keywords:
- EEG
working memory
visual-spatial sketch pad
sLORETA - Abstract:
- ABSTRACT A sphere of study that has garnered much attention amongst neuroscientists is working memory. It is being used to predict cognitive abilities like intelligence, attention and even emotional regulation. Due to its enormous significance, we designed our study, aiming to understand the neural and functional bases of visual-spatial working memory. Visual-spatial working memory tasks are decomposed into encoding, maintenance and retrieval phases. We hypothesize that encoding of visual-spatial information is cognitively more challenging than retrieval of the information. This was tested by combining Electroencephalography (EEG) with a Virtual Reality (VR) paradigm to observe the modulation in EEG activity, alongwith brain areas activated using sLORETA, during encoding and retrieval. EEG power analysis results demonstrated an increase in theta activity during encoding in comparison to retrieval. The increase was predominant in right fronto-central regions of the brain. In contrast alpha activity was significantly higher for retrieval in right parietal, left central and occipital areas in comparison to encoding. This revealed that encoding required more cerebral efforts than retrieval, as past studies have clearly indicated that with increase in task demand theta synchronizes and alpha desynchronizes. Next, source localization results obtained from sLORETA indicated activity in Inferior frontal gyrus which is a part of dorsolateral prefrontal cortex (DLPFC) during encoding, whereas activation of Inferior Parietal lobule and Precuneus during retrieval. Studies have shown that activation in DLPFC occurs in response to increased cerebral challenge while posterior parietal areas represent a default network of the brain which is activated during tasks similar to conscious resting states. Based on these evidences we conclude that encoding of visual-spatial information is more challenging than retrieval. Also, we witnessed an encoding/retrieval flip i.e. disruption of default network of brain during encoding. Our results exhibited that encoding and retrieval utilized different neural substrates. Lastly, the pattern of brain areas activated during both, encoding and retrieval supported the concept of hemispheric laterality i.e., visual-spatial working memory tasks are localized in the right brain hemisphere. We hope that the results from our study would be extended to the clinical population and improve the understanding of visual-spatial deficits that are a normal occurrence post Head Injury, Stroke and even normal aging.