A large body of research has shown that spatial information is processed more accurately in the left than in the right visual field. In healthy subjects, this spatial processing asymmetry has been named ¿pseudoneglect,¿ and it entails a slight but systematic leftward bias across various experimental tasks. A number of studies have revealed that this basic spatial phenomenon is modulated by emotional processing. However, these studies have produced overall mixed results, and the presence and direction of the effect are still unclear.
Here, we will examine the interaction between emotion processing and pseudoneglect using a perceptual line bisection task. Forty participants will be recruited for this project. First, participants will be asked to perform a perceptual bisection line in order to assess each individual¿s attention bias baseline. Second, participants will perform a perceptual bisection line task. Happy, sad, angry, or scrambles faces will be presented either at the ends of the line or before the line appears.
The implication of this project will be discussed in the context of some theoretical frameworks, such as the right-hemisphere hypothesis and the valence-specific hypothesis. The results of this work will potentially contribute to understanding the interplay between emotional states and attention.
The proposed research aims at investigating the following assumptions: the right posterior temporal-parietal is dominant for allocating attention to contralateral left hemifield; neural mechanisms underlying emotion and attention processing are strongly interconnected; emotional stimuli induce asymmetrical alterations in brain activation; this asymmetrical alteration causes a preferential orienting toward the contralateral hemifield, and the activated network of regions underlying emotion processing produces a modulation in the attention network that is reflected in a shift in spatial biases.
These assumptions allow making some precise predictions on the possible experimental outcomes in relation to the different hypotheses. For instance, the right hypothesis implies that attention and emotion processing share the same neural substrates in the right hemisphere; thus, for instance, a face would shift the attention bias leftward regardless of the emotional connotation. Conversely, according to the valence hypothesis, a face with a happy and angry expression would shift the attention bias to the right, and a face with a sad expression would shift the bias to the left.
This proposed research is innovative in relation to previous studies for multiple reasons. First, we will present faces with both approaches (happiness and anger) and withdrawal (sadness) emotions and these stimuli will allow making precise predictions about the right and the valence hypotheses. Second, the stimuli will have foveal and peripheral presentations that will account for possible differences in the visual field. Third, excluding subjects with an r-squared lesser than 0.8 will increase the likelihood of obtaining a reliable measure of spatial bias for each participant and decrease the heterogeneity of the sample due to individual differences in attention spatial biases. Lastly, the presentation of scrambled faces will exclude that the subjects¿ performance will depend on low-level visual properties.
In general, studying the potential role of the individual¿s emotional state in modulating attention function has important implications not only for understanding normal functioning but also for clinical application in neuropsychological patients. Indeed, several studies have shown a positive effect on visual attention, awareness, and reducing bisection error associated with visual neglect syndrome (e.g., Tamietto et al., 2005; Soto et al., 2009; Chen et al., 2013; Kang and Thaut, 2019; Smith and Niedeggen, 2020). Over the last two decades, much research has been focused on the influence of emotional processing on spatial biases in both patients and neurologically intact individuals, based on the strong influence that emotion has on attention in everyday life and on the tight interconnection between the neural mechanisms that mediate these two phenomena. However, this interaction is still not well understood. Understanding how spatial attentional biases are affected by emotional processing can assist clinicians and researchers to understand how this interaction can modulate the strength of contralesional deficits in patients with visual neglect and extinction and ultimately how to employ attentional resources to overcome the deficit.