Rapid and reversible recruitment of early visual cortex for touch.
Level 3 - non-randomized controlled study
Controlled experimental study comparing blindfolded participants to non-blindfolded controls without stated randomization in the abstract
PubMed 18728773 · doi:10.1371/journal.pone.0003046
What was done
Normally sighted adult individuals underwent five days of complete visual deprivation via blindfolding combined with an intensive tactile training program, alongside non-blindfolded controls. Tactile performance was evaluated with a Braille character discrimination task. Serial fMRI measured blood-oxygen-level-dependent (BOLD) signal changes in the occipital cortex during tactile stimulation. On the fifth day and 24 hours post-blindfold removal, repetitive transcranial magnetic stimulation (rTMS) was applied to the occipital cortex to determine whether disrupting visual cortex activity causally impaired tactile discrimination.
What was found
The abstract reports no exact numerical values or sample sizes. Blindfolded participants demonstrated improved Braille character discrimination after five days. In the blindfolded group, fMRI revealed increased occipital cortex BOLD response during tactile stimulation after five days of visual deprivation, which returned to baseline within 24 hours of removing the blindfold. Occipital rTMS on day five impaired Braille recognition in the blindfolded group but not in controls, and this impairment disappeared 24 hours after blindfold removal.
Why it matters
This study shows that the adult human visual cortex can be rapidly and reversibly recruited for tactile processing within days. This rapid timeframe indicates that crossmodal plasticity in early sensory deprivation operates via unmasking and modulating pre-existing neural connections rather than exclusively forming new anatomical pathways.
Limits
The abstract does not disclose participant sample size, demographics, or precise quantitative effect sizes and statistical metrics. Group allocation is not described as randomized, and the study did not measure intermediate time points during the five-day period or long-term outcomes beyond 24 hours post-intervention.