Browsing by Author "Harvey, Denise Y."

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    Distinct loci of lexical and semantic access deficits in aphasia: Evidence from voxel-based lesion-symptom mapping and diffusion tensor imaging
    (Elsevier, 2015) Harvey, Denise Y.; Schnur, Tatiana T.
    Naming pictures and matching words to pictures belonging to the same semantic category negatively affects language production and comprehension. By most accounts, semantic interference arises when accessing lexical representations in naming (e.g., Damian, Vigliocco, & Levelt, 2001) and semantic representations in comprehension (e.g., Forde & Humphreys, 1997). Further, damage to the left inferior frontal gyrus (LIFG), a region implicated in cognitive control, results in increasing semantic interference when items repeat across cycles in both language production and comprehension (Jefferies, Baker, Doran, & Lambon Ralph, 2007). This generates the prediction that the LIFG via white matter connections supports resolution of semantic interference arising from different loci (lexical vsﾠsemantic) in the temporal lobe. However, it remains unclear whether the cognitive and neural mechanisms that resolve semantic interference are the same across tasks. Thus, we examined which gray matter structures [using whole brain and region of interest (ROI) approaches] and white matter connections (using deterministic tractography) when damaged impact semantic interference and its increase across cycles when repeatedly producing and understanding words in 15 speakers with varying lexical-semantic deficits from left hemisphere stroke. We found that damage to distinct brain regions, the posterior versusﾠanterior temporal lobe, was associated with semantic interference (collapsed across cycles) in naming and comprehension, respectively. Further, those with LIFG damage compared to those without exhibited marginally larger increases in semantic interference across cycles in naming but not comprehension. Lastly, the inferior fronto-occipital fasciculus, connecting the LIFG with posterior temporal lobe, related to semantic interference in naming, whereas the inferior longitudinal fasciculus (ILF), connecting posterior with anterior temporal regions related to semantic interference in comprehension. These neuroanatomical-behavioral findings have implications for models of the lexical-semantic language network by demonstrating that semantic interference in language production and comprehension involves different representations which differentially recruit a cognitive control mechanism for interference resolution.
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    Object priming in the fusiform cortex: Exploring effects of task and visual similarity
    (2010) Harvey, Denise Y.; Dannemiller, James L.
    Neural priming for same and different exemplars and viewpoints of objects was examined in two experiments using functional magnetic resonance imaging. In line with previous studies, viewpoint- and exemplar-specific priming was observed in the right fusiform gyrus (RFG). In contrast to some studies, viewpoint- but not exemplar-abstract priming was observed in the left fusiform gyrus (LFG). In the first experiment, neither task-demands nor visual similarity affected priming in the LFG. However, the RFG, including an area specialized for processing faces (the fusiform face area) was sensitive to the visual similarity of exemplar pairs. The second experiment explored this unpredicted result, but did not replicate the visual similarity effects. Results suggest that RFG and LFG are differentially sensitive to changes in viewpoint and are unaffected by task demands or visual similarity.
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    Semantic interference in language production and comprehension: Same or separable loci?
    (2014-04-22) Harvey, Denise Y.; Schnur, Tatiana T.; Martin, Randi C.; Fischer-Baum, Simon; O'Callaghan, Casey
    The ability to speak and understand language is consciously a fast and easy process. However, the language system can err, either in normal processes or as a result of neural damage following stroke. Often, in both production and comprehension, errors are semantically related to the intended word, such as saying or understanding “cat” when the intended meaning is “dog”. This semantic interference (SI) effect suggests that the processing stages involved in language production and comprehension overlap to some extent. However, because language production and comprehension are usually investigated separately, this has led to different conclusions about how SI arises in each language modality. By most accounts, SI in production occurs at the lexical-semantic level, whereas SI in comprehension arises within the semantic system itself. In this dissertation, I distinguish between SI in production and comprehension by examining how (cognitive mechanisms) and where (neural loci) SI arises during picture naming and word-picture matching tasks that elicit SI by manipulating the semantic context with which target items appear. Aim I of my dissertation directly compared the behavioral characteristics of SI in healthy participants’ production and comprehension performance in order to elucidate the level and cognitive mechanism by which SI arises in each language modality. Aim II explored patients’ susceptibility to SI as it related to cortical gray matter and subcortical white matter damage. The results provided converging evidence that not only do the SI characteristics differ in production and comprehension, but also the neural locus of SI differs across language modality. However, the time course of SI is similar in both language modalities. Accordingly, I conclude SI arises when mapping meanings with words in production vs. mapping words with meanings in comprehension, but that the same cognitive mechanism operates over lexical-semantic processes across modalities. In the end, I argue that because of inherent differences between the order with which lexical and semantic representations are accessed in production vs. comprehension, the mechanism produces different behavioral manifestations of SI in each language modality and places differential demands on cognitive control mechanisms required to resolve interference.