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Training-induced cortical representation of a hemianopic hemifield
  1. L Henriksson1,
  2. A Raninen2,
  3. R Näsänen3,
  4. L Hyvärinen4,
  5. S Vanni1
  1. 1Advanced Magnetic Imaging Centre and Brain Research Unit of Low Temperature Laboratory, Helsinki University of Technology, Espoo, Finland
  2. 2Department of Biological and Environmental Sciences, University of Helsinki, Helsinki, Finland
  3. 3Brainwork Laboratory, Finnish Institute of Occupational Health, Helsinki, Finland
  4. 4Faculty of Behavioural Sciences, University of Helsinki, Helsinki, Finland
  1. Correspondence to:
 L Henriksson
 Low Temperature Laboratory, Brain Research Unit, Helsinki University of Technology, PO Box 3000, Espoo 02015 HUT, Finland; henriksson{at}neuro.hut.fi

Abstract

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.

  • fMRI, functional magnetic resonance imaging
  • MCE, minimum current estimate
  • MEG, magnetoencephalography

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Footnotes

  • Published Online First 15 September 2006

  • Funding: This work was supported by the Academy of Finland, Instrumentarium Science Foundation, the Finnish Graduate School of Neuroscience, the Finnish Cultural Foundation, the De blindas vänner rf—Sokeain Ystävät ry and the Finnish Medical Foundation.

  • Competing interests: None.

  • Ethical approval: This study was approved by the ethics committees of the Hospital District of Helsinki and Uusimaa. The participant gave written informed consent before the measurements. Tenets of the Declaration of Helsinki were followed.

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