On nature and limits of cortical developmental plasticity after an early lesion, in a child

MS is a little girl who suffered severe, bilateral destruction of her primary visual areas at six weeks, after premature birth at 30 weeks. Between the ages of 4.5 and 5.5 years she partially recovered different aspects of visual function, and, in particular, the ability to segregate figures from background, based on texture cues. The recovery might have been due to the compensatory role of the remaining visual areas that could have acquired response properties similar to those of the primary visual areas. This is not supported by the available FMRI (functional magnetic resonance imaging) responses to visual stimuli. Instead, abnormalities in the pattern of stimulus-induced changes of interhemi-spheric EEG-coherence in this patient suggest that her visual callosal connections, and possibly other cortico-cortical connections have re-organized abnormally. Since cortico-cortical connections, including the callosal ones appear to be involved in perceptual binding and figure-background segregation, their reorganization could be an important element in the functional recovery after early lesion, and/or in the residual perceptual impairment.