Bottom-up and top-down factors in visual and auditory asymmetries

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The main theoretical foundation for my proposal stems from the model proposed by Hugdahl (2000) according to which the observed perceptual asymmetry in any relevant task reflects a combination of a bottom-up component and a top-down component. Perceptual asymmetries are observed whenever presentation of specific stimuli produces a performance advantage for one side of the body over the other. Specifically, the proposed work will focus on visual and auditory stimuli producing, respectively, an advantage for stimuli presented in the left or right visual field, and an advantage for sounds presented to the left or right ear. In this context, the bottom-up aspect reflects stimulus content (typically verbal or non-verbal) and cerebral organization, whereas the top-down aspect refers to attentional effects (i.e. the ability to direct visual or auditory attention to a specific location). However, I propose that other factors should be included in the top-down component, whereas specific factors involved in the bottom-up component remain underspecified in the model. From this perspective, I propose to pursue three lines of inquiries meeting the short-term objective of characterizing top-down and bottom-up processes in perceptual asymmetries. In one line of research, visual and auditory tasks measuring perceptual asymmetries will be examined from the perspective that they have a significant memory component. A second line of research, will build on the hypothesis that sarcastic speech tends to be slower, of lower pitch, and louder than sincere speech. The third line of research will investigate factors responsible for stimulus dominance in dichotic listening and examine ways to minimize the influence of these factors in the assessment of auditory asymmetries. The long-term goal of this research is to identify task components and cerebral mechanisms underlying perceptual asymmetries with the ultimate goal to provide valid and reliable measurement of perceptual asymmetries for use in the pre-surgery screening of patients with neurological impairments such as epilepsy and brain tumors. Thus, this research has important applications relevant to the measurement of functional cerebral specialization.