Visual and motor cortex excitability:: a transcranial magnetic stimulation study

Objectives: Phosphene thresholds (PTs) to transcranial magnetic stimulation over the occipital cortex and motor thresholds (MTs) have been used increasingly as measures of the excitability of the visual and motor cortex. MT has been utilized as a guide to the excitability of other, non-motor cortical areas such as dorsolateyal prefrontal cortex. The aims of this study were to compare the PTs to MTs; to assess their stability across sessions; and to investigate their relation to MTs. Methods: PTs and MTs were determined using focal transcranial magnetic stimulation over the visual and motor cortex. Results: PTs were shown to be significantly higher than MTs. Both PTs and MTs were stable across sessions. No correlation between PTs and MTs could be established. Conclusions: Phosphene threshold is a stable parameter of the visual cortex excitability. MTs were not related to the excitability of nonmotor cortical areas. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.