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Although food and affective pictures share similar emotional and motivational characteristics, the relationship between the neuronal responses to these stimuli is unclear. Particularly, it is not known whether perceiving and imagining food and affective stimuli elicit similar event-related potential (ERP) patterns. In this study, two ERP correlates, the early posterior negativity (EPN) and the late positive potential (LPP) for perceived and imagined emotional and food photographs were investigated. Thirteen healthy volunteers were exposed to a set of food photos, as well as unpleasant, pleasant, and neutral photos from the International Affective Picture System. In each trial, participants were first asked to view a photo (perception condition), and then to create a visual mental image of it and to rate its vividness (imagery condition). The results showed that during perception, brain regions corresponding to sensorimotor and parietal motivational (defensive and appetitive) systems were activated to different extents, producing a graded pattern of EPN and LPP responses specific to the photo content - more prominent for unpleasant than pleasant and food content. Also, an EPN signature occurred in both conditions for unpleasant content, suggesting that, compared to food or pleasant content, unpleasant content may be attended to more intensely during perception and may be represented more distinctly during imagery. Finally, compared to LLP activation during perception, as well as imagery and perception of all other content, LPP activation was significantly reduced during imagery of unpleasant photos, suggesting inhibition of unwanted memories. Results are framed within a neurocognitive working model of embodied emotions.

Biological motion stimuli, depicted as orthographically projected point-light or stick-figure walkers, do not contain any information about their orientation in depth. The projections of such stimuli, therefore, provide the same visual information when oriented towards the viewer as when oriented away. Even though this is the case, naïve observers display a bias to perceive the facing-towards percept more often. Some researchers have speculated that this facing-the-viewer bias may exist for sociobiological reasons. That is, mistaking another human as retreating when they are actually approaching could potentially have more severe consequences than the opposite error. This theory implies that the facing-towards percept of a biological motion stimulus is potentially more threatening. Measures of anxiety and the facing-the-viewer bias should therefore be related, as researchers have consistently found that anxious individuals display an attentional bias towards more threatening stimuli. In our first experiment, we demonstrated that individuals with greater anxiety do indeed have greater facing-the-viewer biases, and that this relationship is mediated by inhibitory ability (Chapter 2). As our first experiment was correlational in nature, we next used a between-subjects design. We showed that physical exercise, which is known to reduce anxiety, also reduces the facing-the-viewer bias for full stick figure walkers, but not for bottom- or top-half-only stimuli (Chapter 3). In our final experiment, we manipulated anxiety more directly using progressive muscle relaxation and an anxiety induction task (Chapter 4). In the latter experiment, we found that relaxation had the same effect on facing-the-viewer biases that physical exercise had, while our anxiety induction task did not affect biases significantly. In Chapter 6, we discuss the importance of these findings in the context of understanding how anxiety affects our perception of our external environment., Thesis (Ph.D, Psychology) -- Queen's University, 2014-07-25 13:45:16.077