Temporal-Nasal Asymmetry in Facial Emotion Processing

Hydra, Farah (2011) Temporal-Nasal Asymmetry in Facial Emotion Processing. London City University.

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Abstract

Whilst many have argued for a right hemisphere advantage for the processing of emotional stimuli, reflected in a left hemifield bias for attending, researchers have also highlighted the attentional biases of the superior colliculus, which shows an enhanced response to stimuli in the temporal hemifields. This structure has been found to be part of a subcortical network involving the pulvinar and amygdala, activated in response to emotional signals in our environment. The present study was therefore designed to investigate hemispheric lateralisation effects in facial emotion processing, as well as to determine if a temporal-nasal asymmetry in processing could be found for emotional faces, via activation of the colliculo-pulvinar-amygdala pathway. This was attempted using a behavioural choice-reaction time study, whereby participant responses to the location of monocularly presented emotional faces of varying intensities were measured. Based on suggestions of the combined influence of cortical and subcortical systems on spatial attention (Zackon et al, 1997), it was hypothesised that a left hemifield cortical advantage for attending to emotional stimuli would interact with a temporal hemifield subcortical advantage for attending, giving a left temporal hemifield advantage for attending. Data analyses showed that whilst reaction time and accuracy responses significantly improved with greater intensity of facial expression, the hemispheric lateralisation and temporal-nasal asymmetry hypotheses could not be supported. However, patterns in the data which demonstrated these effects, though non-significant, suggested flaws in the current experimental design. It is therefore argued that there is a need for more ecologically valid procedures for these effects to be surfaced. Suggestions are made for future research.