Biomedical subjects

William Davis Gaillard

Publications and source records attributed to William Davis Gaillard.

3 recordsLinked to original sources

PubMed2005

Functional imaging of developmental and adaptive changes in neurocognition.

Characterization of brain-behavior relationships through functional magnetic imaging (fMRI) within typically or atypically developing populations poses methodological and interpretational challenges. We consider theoretical, methodological, and artifactual factors that influence characterization of developmental and adaptive changes in childhood. Findings from anatomical and physiological brain development studies are highlighted as they may influence functional imaging results. Then, we consider several patterns of functional activation within the context of developmental processes as well as neurologic disease. Hypotheses regarding the development of cognitive networks are proposed to account for the individual differences seen in normal and atypical development. We also identify potential sources of unwanted variability related to experimental design and task performance and suggest possible solutions to help minimize these effects. Lastly, a challenge for current studies is a lack of group and individual analysis methods that can be reliably applied to capture and quantify factors that contribute to variability introduced by developmental and disease processes. We review current methods and propose potential solutions.

Adaptation, Physiological↗

PubMed2004

Functional MR imaging of language, memory, and sensorimotor cortex.

fMR imaging is a versatile technology that allows for the noninvasive identification of sensory, motor,and cognitive functions that may be impaired by surgical resection. fMR imaging provides the capacity to probe several brain functions, and when results are uncertain, to repeat or modify them. There are some limitations, MR contraindications to scanning, motion, and cooperation among them. Yet for most patients fMR imaging provides a reliable way to lateralize language dominance and to guide localization of language functions. Memory paradigms lag behind language in practical application, but the impediments to its utility will likely be resolved in the near future.

Brain Mapping↗

PubMed2002

Neuroimaging reveals automatic speech coding during perception of written word meaning.

The extent to which visual word perception engages speech codes (i.e., phonological recoding) remains a crucial question in understanding mechanisms of reading. In this study, we used functional magnetic resonance imaging techniques combined with behavioral response measures to examine neural responses to focused versus incidental phonological and semantic processing of written words. Three groups of subjects made simple button-pressing responses in either phonologically (rhyming-judgment) or semantically (category-judgment) focused tasks or both tasks with identical sets of visual stimuli. In the phonological tasks, subjects were given both words and pseudowords separated in different scan runs. The baseline task required feature search of scrambled letter strings created from the stimuli for the experimental conditions. The results showed that cortical regions associated with both semantic and phonological processes were strongly activated when the task required active processing of word meaning. However, when subjects were actively processing the speech sounds of the same set of written words, brain areas typically engaged in semantic processing became silent. In addition, subjects who performed both the rhyming and the semantic tasks showed diverse and significant bilateral activation in the prefrontal, temporal, and other brain regions. Taken together, the pattern of brain activity provides evidence of a neural basis supporting the theory that in normal word reading, phonological recoding is automatic and facilitates semantic processing of written words, while rapid comprehension of word meaning requires devoted attention. These results also raise questions about including multiple cognitive tasks in the same neuroimaging sessions.

Adult↗