Monday, January 02, 2006

More info on the kids study

Here is more information on the preliminary study, and its caveats: see also here.


... These previous [brain] studies, however, have been limited to examining only adults who stutter, and no studies have thus far examined neural correlates of spontaneous recovery from stuttering. Hence it remains a clinically and theoretically imperative goal to determine the neural correlates of childhood stuttering persistence and recovery, closer to disorder onset.
Here we present preliminary results from a voxel-based morphometry study
(VBM) looking at children with persistent stuttering (CWPS), children who have spontaneously recovered from stuttering (CWRS), and children who have never stuttered (CWNS). Results indicate that, compared to CWNS, children who persist or have recovered from stuttering have significantly less gray matter density in the left hemisphere inferior frontal regions coinciding with the Broca¹s area, as well as the anterior cingulate. Interestingly, CWRS showed an intermediate level of gray matter density compared to CWNS and CWPS in these areas. Results are discussed in context of possible developmental pattern differences that lead to, or are a result of, eventual persistence or recovery from stuttering.


The present results point to anomalous gray matter density (GMD) in several regions of the brain as possible neural correlates of developmental stuttering. Regardless of eventual persistence or recovery, children who have once stuttered appear to exhibit significantly reduced GMD compared to their normally fluent peers in areas such as the left IFG, an area known to be critical in speech motor planning. Although CWRS generally showed a similar pattern of GMD findings to CWPS, they also exhibited important differences from the latter, which may reflect brain plasticity associated with natural recovery from stuttering. For instance, CWRS tended to exhibit an intermediate level of GMD in the left IFG and ACC, namely, levels of density approximating that of controls. On the other hand, CWRS tended to have decreased GMD in parietal regions such as the SMA (BA 6) and the SMG (BA 40) compared to the other two groups, possibly reflecting the effects of increased pruning in these regions correlating with a compensating mechanism they may have adopted to aid in recovery.

This study has several limitations. First, due to the small sample size in the three groups (n=7 in each group), the results are preliminary and need to be replicated with a larger sample. Second, although VBM provides an even-handed approach to looking at regional differences among groups on a whole brain basis, the process of averaging and smoothing involved in the analysis pipeline may obscure individual differences in structure, and group differences in smaller areas of interest may be more difficult to identify. Third, structural anomalies may merely represent risk factors for anomolous function. As such, future studies may consider pairing structural techniques such as VBM and DTI with functional techniques (i.e., fMRI and MEG) in order to elucidate correlations between anomalous structure and functional deficits involved in development, maintenance, or recovery from stuttering.

No comments: