Visual speech circuits in profound acquired deafness: a possible role for latent multimodal connectivity.
Level 4 - case-series / case-control
Case-control observational neuroimaging study with cross-sectional comparisons
PubMed 17906328 · doi:10.1093/brain/awm230
What was done
Using functional magnetic resonance imaging (fMRI), researchers investigated brain networks during a visual speechreading task in 9 profoundly deaf patients (7 women, mean age ± SE = 50.2 ± 4.8 years; deafness duration 4 to 48 months) and a group of hearing control subjects. The study evaluated cortical activity related to speechreading fluency (compensation) versus the duration of sensory deprivation (time-dependent plasticity).
What was found
Deaf patients and control subjects performed equally well on the visual speechreading task. Deaf patients activated the left posterior superior temporal cortex more than controls. This activation correlated with speechreading fluency but did not correlate positively with duration of deafness; instead, activation in this region decreased with deafness duration and was most pronounced right after deafness onset. Exact statistical values, effect sizes, and p-values were not reported in the abstract.
Why it matters
This study challenges the standard view that cross-modal cortical reorganization requires slow, progressive colonization, suggesting instead that early compensation in acquired deafness relies on pre-existing latent multimodal connections.
Limits
The deaf cohort was very small (n = 9), the abstract does not report the number of control subjects, and the analysis of plasticity over duration was cross-sectional across different individuals rather than a longitudinal follow-up.