Hemispheric Contributions to Visuospatial Attention and Emotional Processing

Author: Ella Moeck

Moeck, Ella, 2019 Hemispheric Contributions to Visuospatial Attention and Emotional Processing, Flinders University, College of Education, Psychology and Social Work

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The human brain comprises the right and left hemisphere, which increase its capacity by allowing simultaneous processing of information. The right and left hemispheres have functional asymmetries, defined as differences in behaviour or neural activation resulting from specialisations located in each hemisphere. This thesis focuses on asymmetries for visuospatial attention and emotional processing. Few studies have investigated the combined influence of visuospatial attention and emotional processing asymmetries on behavioural responses (e.g., attention, memory) to naturalistic scenes, despite knowing they are largely automatic and do not function in isolation. I seek to address this gap by investigating the influence of visuospatial attention and emotional processing asymmetries on three behavioural outcomes; attention, recognition memory, involuntary memory. More specifically, the broad objective of this thesis is to understand how functional asymmetries influence attention to and memory for emotional stimuli, primarily images. I achieved this objective by establishing whether these asymmetries influence (1) attending to and disengaging from emotional stimuli, (2) recognition memory for emotional (negative and positive) compared to neutral images, and (3) involuntary memory for negative images. I also investigated (4) increasing hemispheric activation to perform unilateral contractions (i.e., squeezing a ball with one hand), by measuring whether these contractions alter biases in visuospatial attention.

My findings suggest that hemispheric asymmetries for visuospatial attention and emotional processing influence some behavioural outcomes, primarily recognition memory for emotional images. I found a left hemisphere memory deficit for emotional (positive and negative) compared to neutral images. Thus, it is not right hemisphere superiority for processing emotion, but left hemisphere inferiority, that appears to influence memory. However, task demands (e.g., making recognition memory judgments after viewing image pairs for 500 ms vs. viewing a single image for 3000 ms) and the type of memory measured (voluntary vs. involuntary) influenced whether or not this left hemisphere memory deficit occurred. I also examined whether hemispheric asymmetries influence attention; specifically, the emotion induced blindness effect (Most, Chun, Widders, & Zald, 2005)—where an emotional distractor impairs people’s ability to notice a neutral target presented shortly afterwards. I found limited evidence that hemispheric asymmetries influence people’s ability to disengage from emotional (vs. neutral) stimuli, in this case to detect a neutral target. Although right hemisphere processing improved target detection overall, right and left hemisphere processing led to a similar impairment in target detection following emotional distractors. Finally, I found that unilateral contractions did not influence visuospatial attention, suggesting they may be an ineffective method of increasing hemispheric activation and visuospatial attention asymmetries.

These findings add to the view that we can no longer see responsibilities of the right and left hemisphere as single dichotomous units; the processes within and the interaction between the right and left hemispheres leads to our experience of emotion. This thesis has practical implications for understanding how hemispheric asymmetries contribute to emotional processing in general and speculating how hemispheric asymmetries may lead to problematic emotional processing. Future research should directly test the influence of hemispheric asymmetries in the development and maintenance of psychological disorders.

Keywords: visuospatial attention, emotion, laterality, hemispheric asymmetries

Subject: Psychology thesis

Thesis type: Doctor of Philosophy
Completed: 2019
School: College of Education, Psychology and Social Work
Supervisor: Melanie Takarangi