Biomedical subjects

Karen M Jones

Publications and source records attributed to Karen M Jones.

4 recordsLinked to original sources

PubMed2005

Phonological decoding involves left posterior fusiform gyrus.

Aloud reading of novel words is achieved by phonological decoding, a process in which grapheme-to-phoneme conversion rules are applied to "sound out" a word's spoken representation. Numerous brain imaging studies have examined the neural bases of phonological decoding by contrasting pseudoword (pronounceable nonwords) to real word reading. However, only a few investigations have examined pseudoword reading under both aloud and silent conditions, task parameters that are likely to significantly alter the functional anatomy of phonological decoding. Subjects participated in an fMRI study of aloud pseudoword, aloud real word, silent pseudoword, and silent real word reading. Using this two-by-two design, we examined effects of word-type (real words vs. pseudowords) and response-modality (silent vs. aloud) and their interactions. We found 1) four regions to be invariantly active across the four reading conditions: the anterior aspect of the left precentral gyrus (Brodmann's Area (BA) 6), and three areas within the left ventral occipitotemporal cortex; 2) a main effect of word-type (pseudowords > words) in left inferior frontal gyrus and left intraparietal sulcus; 3) a main effect of response-modality (aloud > silent) that included bilateral motor, auditory, and extrastriate cortex; and 4) a single left hemisphere extrastriate region showing a word-type by response-modality interaction effect. This region, within the posterior fusiform cortex at BA 19, was uniquely modulated by varying phonological processing demands. This result suggests that when reading, word forms are subject to phonological analysis at the point they are first recognized as alphabetic stimuli and BA 19 is involved in processing the phonological properties of words.

Adult↗

PubMed2004

Neural changes following remediation in adult developmental dyslexia.

Brain imaging studies have explored the neural mechanisms of recovery in adults following acquired disorders and, more recently, childhood developmental disorders. However, the neural systems underlying adult rehabilitation of neurobiologically based learning disabilities remain unexplored, despite their high incidence. Here we characterize the differences in brain activity during a phonological manipulation task before and after a behavioral intervention in adults with developmental dyslexia. Phonologically targeted training resulted in performance improvements in tutored compared to nontutored dyslexics, and these gains were associated with signal increases in bilateral parietal and right perisylvian cortices. Our findings demonstrate that behavioral changes in tutored dyslexic adults are associated with (1) increased activity in those left-hemisphere regions engaged by normal readers and (2) compensatory activity in the right perisylvian cortex. Hence, behavioral plasticity in adult developmental dyslexia involves two distinct neural mechanisms, each of which has previously been observed either for remediation of developmental or acquired reading disorders.

Adult↗

PubMed2002

Hypothesis testing for selective, differential, and conjoined brain activation.

Hypothesis testing in functional neuroimaging studies relies heavily on the computation of categorical contrasts in which brain activation associated with one experimental condition is assessed relative to brain activation associated with a different experimental condition. Often, multiple pair-wise contrasts are computed and reported independently. Here we describe an approach to hypothesis testing that logically combines multiple pair-wise contrasts to distinguish among selective, differential and conjoined brain activation patterns. Using a sample dataset in which participants viewed objects, visual noise patterns or a fixation cross, we demonstrate that selective and differential brain activation patterns are often confounded with current approaches to hypothesis testing but that the logical combination approach can distinguish between these two types of data patterns. Specifically, we show that brain regions that respond selectively to an object recognition task relative to viewing visual noise or a fixation cross (selective activation) are mutually exclusive from brain regions that show a graded response to object viewing, noise viewing and visual fixation (differential activation). We thus show that the logical combination approach sufficiently constrains the results of categorical contrasts to reflect only the data pattern that would be predicted from the cognitive processing account under investigation.

Adolescent↗

PubMed2002

Meta-analysis of the functional neuroanatomy of single-word reading: method and validation.

Intersubject variability and subtle differences in experimental design can lead to variable results in studies of cognitive processes such as reading. To accurately identify the neural processes associated with cognition and sensorimotor processing, meta-analytic methods capable of identifying areas of consistent activation among studies are useful. This paper describes a novel approach for combining published neuroimaging results from multiple studies, designed to maximize the quantification of interstudy concordance while minimizing the subjective aspects of meta-analysis. In this method, a localization probability distribution was modeled for each activation focus obtained from 11 PET studies of reading single words aloud, and the union of these distributions was taken to yield an activation likelihood estimate map for the brain. Significance was assessed via permutation analysis of randomly generated sets of foci. Regions of significant concordance were identified in bilateral motor and superior temporal cortices, pre-SMA, left fusiform gyrus, and the cerebellum. These meta-analytic results were validated by comparison with new fMRI data on aloud word reading in normal adult subjects. Excellent correspondence between the two statistical maps was observed, with fMRI maxima lying close to all meta-analysis peaks and statistical values at the peaks identified by the two techniques correlating strongly. This close correspondence between PET meta-analysis and fMRI results also demonstrates the validity of using fMRI for the study of language tasks involving overt speech responses. Advantages of this automated meta-analysis technique include quantification of the level of concordance at all brain locations and the provision for use of a threshold for statistical significance of concordance.

Brain↗