Dalia Khammash1, Molly Simmonite2, Thad A Polk3, Stephan F Taylor4, Sean K Meehan5. 1. School of Kinesiology, University of Michigan, 401 Washtenaw Ave, 41809, Ann Arbor, MI, USA; Department of Psychology, University of Michigan, 530 Church Street, 48109, Ann Arbor, MI, USA. Electronic address: daliak@umich.edu. 2. Department of Psychology, University of Michigan, 530 Church Street, 48109, Ann Arbor, MI, USA. Electronic address: molsim@umich.edu. 3. Department of Psychology, University of Michigan, 530 Church Street, 48109, Ann Arbor, MI, USA. Electronic address: tpolk@umich.edu. 4. Department of Psychiatry, University of Michigan, 4250 Plymouth Rd, 48109, Ann Arbor, MI, USA. Electronic address: sftaylor@med.umich.edu. 5. School of Kinesiology, University of Michigan, 401 Washtenaw Ave, 41809, Ann Arbor, MI, USA. Electronic address: skmeehan@uwaterloo.ca.
Abstract
BACKGROUND: Transcranial magnetic stimulation (TMS) is a non-invasive method to stimulate localized brain regions. Despite widespread use in motor cortex, TMS is seldom performed in sensory areas due to variable, qualitative metrics. OBJECTIVE: Assess the reliability and validity of tracing phosphenes, and to investigate the stimulation parameters necessary to elicit decreased visual cortex excitability with paired-pulse TMS at short inter-stimulus intervals. METHODS: Across two sessions, single and paired-pulse recruitment curves were derived by having participants outline elicited phosphenes and calculating resulting average phosphene sizes. RESULTS: Phosphene size scaled with stimulus intensity, similar to motor cortex. Paired-pulse recruitment curves demonstrated inhibition at lower conditioning stimulus intensities than observed in motor cortex. Reliability was high across sessions. CONCLUSIONS: TMS-induced phosphenes are a valid and reliable tool for measuring cortical excitability and inhibition in early visual areas. Our results also provide appropriate stimulation parameters for measuring short-latency intracortical inhibition in visual cortex.
BACKGROUND: Transcranial magnetic stimulation (TMS) is a non-invasive method to stimulate localized brain regions. Despite widespread use in motor cortex, TMS is seldom performed in sensory areas due to variable, qualitative metrics. OBJECTIVE: Assess the reliability and validity of tracing phosphenes, and to investigate the stimulation parameters necessary to elicit decreased visual cortex excitability with paired-pulse TMS at short inter-stimulus intervals. METHODS: Across two sessions, single and paired-pulse recruitment curves were derived by having participants outline elicited phosphenes and calculating resulting average phosphene sizes. RESULTS: Phosphene size scaled with stimulus intensity, similar to motor cortex. Paired-pulse recruitment curves demonstrated inhibition at lower conditioning stimulus intensities than observed in motor cortex. Reliability was high across sessions. CONCLUSIONS: TMS-induced phosphenes are a valid and reliable tool for measuring cortical excitability and inhibition in early visual areas. Our results also provide appropriate stimulation parameters for measuring short-latency intracortical inhibition in visual cortex.
Authors: M Oliveri; C Caltagirone; M M Filippi; R Traversa; P Cicinelli; P Pasqualetti; P M Rossini Journal: J Physiol Date: 2000-12-01 Impact factor: 5.182
Authors: T Kujirai; M D Caramia; J C Rothwell; B L Day; P D Thompson; A Ferbert; S Wroe; P Asselman; C D Marsden Journal: J Physiol Date: 1993-11 Impact factor: 5.182