Browsing by Author "Basak, Chandramallika"

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    Binaral Rivalry in the Presence of Visual Lexical and Perceptual Influences
    (2011) Chen, Jennifer; Basak, Chandramallika
    When two different odorants are presented at the same time to the two nostrils, we experience alternations in olfactory percepts, a phenomenon called binaral rivalry. Little, however, is known about the nature of such alternations. Here we investigate this issue by subjecting unstable and stable olfactory percepts to the influences of visual lexical or perceptual cues as participants engage in either mononaral sampling of a single odorant or binaral sampling oftwo different odorants. We show that alternations of olfactory percepts in the binaral setting persist even when visual modulation is present. We further show that while the two types of cues exert comparable effects in the mononaral setting, they produce greater and unequivocal differences in the binaral setting, with perceptual cues outweighing lexical cues. Our findings provide the evidence that an inherent, stimulus-driven process underlies binaral rivalry despite its general susceptibility to topdown influences.
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    Inhibitory control mechanisms and their role in task switching: A multi-methodological approach
    (2013-05-13) Allen, Corinne; Martin, Randi C.; Schnur, Tatiana T.; Oswald, Frederick L.; Kemmer, Suzanne E.; Basak, Chandramallika
    Executive control allows us to ignore distraction and switch between tasks in a flexible, yet organized fashion. While a hallmark of controlled behavior, distinctions among executive control processes are not thoroughly agreed upon. The present work explored the organization of two of these executive control processes, inhibition and shifting, and their relationship to each other. There were two primary goals. The first goal was to investigate the distinction among inhibitory control processes, as “inhibition” has oftentimes been considered a unitary construct. For example, there is evidence that response-distractor inhibition, which involves resolving interference from dominant responses or distractors in the external environment, is different from resistance to proactive interference (PI), which involves overcoming interference from previously relevant representations in memory. Using aging, neuropsychology, and individual differences methodologies, I investigated the unity and diversity of inhibitory control mechanisms. The healthy aging and neuropsychological evidence supported a distinction between response-distractor inhibition and resistance to proactive interference. However, when controlling for processing speed, the individual differences work suggested a need for further specification, as only a subset of these tasks emerged in the single factor model that provided the best fit to the data. The second goal was to explore how inhibitory control processes interact with task switching, as some theoretical accounts of task switching have suggested that switch costs result from the need to overcome interference from the previously relevant task. Inconsistent with these theories, I found little relation between inhibitory control and measures of global and local task switching, and instead, working memory served as the best predictor of these shifting measures. In contrast, inhibitory control was related to the backward inhibition abilities of older adults. These findings are discussed within a theory of working memory that accounts for the patterns of results found across the different methodologies.
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    The Mechanisms of Proactive Interference and Their Relationship with Working Memory
    (2012-09-05) Glaser, Yi; Martin, Randi C.; Byrne, Michael D.; Wilson, Rick K.; Basak, Chandramallika; Beauchamp, Michael S.
    Working memory (WM) capacity – the capacity to maintain and manipulate information in mind – plays an essential role in high-level cognitive functions. An important determinant of WM capacity is the ability to resolve interference of previously encoded but no longer relevant information (proactive interference: PI). Four different mechanisms of PI resolution involving binding and inhibition have been proposed in the literature, although debate continues regarding their role. Braver et al. (2007) introduced an important distinction in the PI resolution literature, proposing two general types of PI control mechanisms that occur at different time points: proactive control (involves preparation in advance of the interference) and reactive control (occurs after interference occurs). This thesis proposed that among these four functions involving binding and inhibition, item inhibition and binding could be involved in proactive control, while familiarity inhibition and episodic inhibition could be involved in reactive control. The question is which mechanism in each pair is indeed involved in proactive control and reactive control respectively, and how these proactive control and reactive control mechanisms work together to resolve PI. In addition, do these mechanisms play a role in the relationship between PI resolution and WM? In an individual differences study, individuals’ ability to resolve PI was assessed in memory tasks, with two versions of each that encouraged the use of either proactive or reactive control. In addition, measures were obtained of individuals’ ability of binding and inhibition in tasks that had minimal memory demands. Regression analyses showed contributions of binding and inhibition to PI resolution and WM. Moreover, these functions are responsible for the correlation between PI resolution and WM. In a neuroimaging study, the neural basis of proactive control was examined by comparing two memory tasks that differed in their demand on binding and inhibition. In addition, the brain regions engaged in reactive control was examined by contrasting trials involving interference or not. The thesis showed that item inhibition carried out by the left inferior frontal cortex (IFC) is involved in proactive control while episodic inhibition carried out by the left IFC and the posterior parietal cortex is involved in reactive control.