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Functional magnetic resonance imaging of the cortical response to photic stimulation in humans following optic neuritis recovery |
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| Authors: | Toosy A T Werring D J Bullmore E T Plant G T Barker G J Miller D H Thompson A J |
| Affiliation: | a NMR Research Unit, Institute of Neurology, Queen Square, London WC1N 3BG, UK b Department of Psychiatry, University of Cambridge, Addenbrooke's Hospital, Cambridge CB2 2QQ, UK c The National Hospital for Neurology and Neurosurgery, Queen Square, London WC1N 3BG, UK |
| Abstract: | Recovery from optic neuritis has been shown to be associated with an abnormal functional MRI (fMRI) response following exposure of the eye to an epoch based (ON-OFF design) flickering photic stimulus. Visual cortex activation is reduced during photic stimulation, whilst extra-occipital areas are extensively activated with a peak blood oxygen level dependent response during the OFF phase of the stimulus paradigm. We performed a further fMRI experiment to determine whether the abnormal extra-occipital response is a phase-specific phenomenon or whether it results from a delayed haemodynamic response. A cohort of patients that recovered from optic neuritis was studied, this time using a longer photic stimulation epoch (40 s). The extra-occipital response again peaked during the baseline condition, indicating that the phenomenon is phase dependent. Our results also reinforce the important findings of extra-occipital activation following optic neuritis which may represent an adaptive reorganization of the cerebral response. |
| Keywords: | Functional MRI Optic neuritis Photic stimulation Cortical reorganization |
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