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Motor and phosphene thresholds: a TMS correlation study

Stewart, L; Walsh, V; hwell, J; (2001) Motor and phosphene thresholds: a TMS correlation study. Neuropsychologia , 39 (4) pp.415 - 419.

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Objective: To investigate the stability of visual phosphene thresholds and to assess whether they correlate with motor thresholds. Background: Currently, motor threshold is used as an index of cortical sensitivity so that in transcranial magnetic stimulation (TMS) experiments, intensity can be set at a given percentage of this value. It is not known whether this is a reasonable index of cortical sensitivity in non-motor and hence whether it should be used in experiments where other cortical areas are targeted. Previous studies have indicated that phosphene threshold might be a suitable alternative in TMS studies of the visual system. Method: Using single pulse TMS visual phosphene and motor thresholds were measured in 15 subjects. Both thresholds were retested in seven of these subjects a week later. Result: Visual phosphene thresholds, though stable within subjects across the two sessions, showed greater variability than motor thresholds. There was no correlation between the two measures. Conclusion: TMS motor thresholds cannot be assumed to be a guide to visual cortex excitability and by extension are probably an inappropriate guide to the cortical excitability of other non-motor areas of the brain. Phosphene thresholds are proposed as a potential standard for inter-individual comparison in visual TMS experiments.

Type: Article
Title: Motor and phosphene thresholds: a TMS correlation study
Additional information: Imported via OAI, 7:29:01 11th Aug 2007
UCL classification: UCL > School of Life and Medical Sciences > Faculty of Brain Sciences > Psychology and Language Sciences (Division of) > Institute of Cognitive Neuroscience
UCL > School of Life and Medical Sciences > Faculty of Life Sciences
URI: http://discovery.ucl.ac.uk/id/eprint/175268
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