Biomedical subjects

Helen L Jamison

Publications and source records attributed to Helen L Jamison.

3 recordsLinked to original sources

PubMed2006

The role of the posterior fusiform gyrus in reading.

Studies of skilled reading [Price, C. J., & Mechelli, A. Reading and reading disturbance. Current Opinion in Neurobiology, 15, 231-238, 2005], its acquisition in children [Shaywitz, B. A., Shaywitz, S. E., Pugh, K. R., Mencl, W. E., Fulbright, R. K., Skudlarski, P., et al. Disruption of posterior brain systems for reading in children with developmental dyslexia. Biological Psychiatry, 52, 101-110, 2002; Turkeltaub, P. E., Gareau, L., Flowers, D. L., Zeffiro, T. A., & Eden, G. F. Development of neural mechanisms for reading. Nature Neuroscience, 6, 767-773, 2003], and its impairment in patients with pure alexia [Leff, A. P., Crewes, H., Plant, G. T., Scott, S. K., Kennard, C., & Wise, R. J. The functional anatomy of single word reading in patients with hemianopic and pure alexia. Brain, 124, 510-521, 2001] all highlight the importance of the left posterior fusiform cortex in visual word recognition. We used visual masked priming and functional magnetic resonance imaging to elucidate the specific functional contribution of this region to reading and found that (1) unlike words, repetition of pseudowords ("solst-solst") did not produce a neural priming effect in this region, (2) orthographically related words such as "corner-corn" did produce a neural priming effect, but (3) this orthographic priming effect was reduced when prime-target pairs were semantically related ("teacher-teach"). These findings conflict with the notion of stored visual word forms and instead suggest that this region acts as an interface between visual form information and higher order stimulus properties such as its associated sound and meaning. More importantly, this function is not specific to reading but is also engaged when processing any meaningful visual stimulus.

Adolescent↗

PubMed2005

Hemispheric specialization for processing auditory nonspeech stimuli.

The left hemisphere specialization for speech perception might arise from asymmetries at more basic levels of auditory processing. In particular, it has been suggested that differences in "temporal" and "spectral" processing exist between the hemispheres. Here we used functional magnetic resonance imaging to test this hypothesis further. Fourteen healthy volunteers listened to sequences of alternating pure tones that varied in the temporal and spectral domains. Increased temporal variation was associated with activation in Heschl's gyrus (HG) bilaterally, whereas increased spectral variation activated the superior temporal gyrus (STG) bilaterally and right posterior superior temporal sulcus (STS). Responses to increased temporal variation were lateralized to the left hemisphere; this left lateralization was greater in posteromedial HG, which is presumed to correspond to the primary auditory cortex. Responses to increased spectral variation were lateralized to the right hemisphere specifically in the anterior STG and posterior STS. These findings are consistent with the notion that the hemispheres are differentially specialized for processing auditory stimuli even in the absence of linguistic information.

Acoustic Stimulation↗

PubMed2004

Morphology and the internal structure of words.

Morphology is the aspect of language concerned with the internal structure of words, and languages vary in the extent to which they rely on morphological structure. Consequently, it is not clear whether morphology is a basic element of a linguistic structure or whether it emerges from systematic regularities between the form and meaning of words. Here, we looked for evidence of morphological structure at a neural systems level by using a visual masked priming paradigm and functional MRI. Form and meaning relations were manipulated in a 2 x 2 design to identify reductions in blood oxygenation level-dependent signal related to shared form (e.g., corner-corn), shared meaning (e.g., idea-notion), and shared morphemes (e.g., boldly-bold, which overlapped in both form and meaning). Relative to unrelated pairs (e.g., ozone-hero), morphologically related items reduced blood oxygenation level-dependent signal in the posterior angular gyrus bilaterally, left occipitotemporal cortex, and left middle temporal gyrus. In the posterior angular gyrus, a neural priming effect was observed for all three priming conditions, possibly reflecting reduced attentional demands rather than overlapping linguistic representations per se. In contrast, the reductions seen in the left occipitotemporal cortex and left middle temporal gyrus corresponded, respectively, to main effects of orthographic and semantic overlap. As neural regions sensitive to morphological structure overlapped almost entirely with regions sensitive to orthographic and semantic relatedness, our results suggest that morphology emerges from the convergence of form and meaning.

Adolescent↗