Training-induced cortical representation of a hemianopic hemifield.
BACKGROUND
Patients with homonymous hemianopia often have some residual sensitivity for visual stimuli in their blind hemifield. Previous imaging studies suggest an important role for extrastriate cortical areas in such residual vision, but results of training to improve vision in patients with hemianopia are conflicting.


OBJECTIVE
To show that intensive training with flicker stimulation in the chronic stage of stroke can reorganise visual cortices of an adult patient.


METHODS
A 61-year-old patient with homonymous hemianopia was trained with flicker stimulation, starting 22 months after stroke. Changes in functioning during training were documented with magnetoencephalography, and the cortical organisation after training was examined with functional magnetic resonance imaging (fMRI).


RESULTS
Both imaging methods showed that, after training, visual information from both hemifields was processed mainly in the intact hemisphere. The fMRI mapping results showed the representations of both the blind and the normal hemifield in the same set of cortical areas in the intact hemisphere, more specifically in the visual motion-sensitive area V5, in a region around the superior temporal sulcus and in retinotopic visual areas V1 (primary visual cortex), V2, V3 and V3a.


CONCLUSIONS
Intensive training of a blind hemifield can induce cortical reorganisation in an adult patient, and this case shows an ipsilateral representation of the trained visual hemifield in several cortical areas, including the primary visual cortex.
Henriksson
L
L
Advanced Magnetic Imaging Centre and Brain Research Unit of Low Temperature Laboratory, Helsinki University of Technology, Espoo, Finland. henriksson@neuro.hut.fi
Raninen
A
A
Näsänen
R
R
Hyvärinen
L
L
Vanni
S
S
D005425:Flicker Fusion; D006423:Hemianopsia / Q000209:etiology / Q000534:rehabilitation*; D006801:Humans; D008279:Magnetic Resonance Imaging; D015225:Magnetoencephalography; D008297:Male; D008875:Middle Aged; D020521:Stroke / Q000150:complications; D014793:Visual Cortex / Q000502:physiology*; D014796:Visual Perception