title: Are recognition deficits following occipital lobe TMS explained by raised detection thresholds?
abstract: It is known that transcranial magnetic stimulation (TMS) administered over the occipital pole suppresses recognition of visual objects. Our aim was to ascertain whether this suppression can be interpreted as a change in visual contrast threshold. Four subjects detected the orientation of an U-shaped hook flashed for 21 ms. Under control conditions, mean contrast threshold was found at 0.88 log units Weber contrast. Thresholds were raised if TMS was applied 40-200 ms after the visual stimulus. Maximum elevation was 1.67 log units under TMS at 120 ms stimulus onset asynchrony. This phenomenon can be interpreted as a reduction in signal-to-noise ratio of the visual stimuli by TMS, which can be compensated for by increasing the contrast of the stimuli.
authors.affiliation: Max-Planck-Institut für biologische Kybernetik, Tübingen, Germany. thomas.kammer@tuebingen.mpg.de
authors.forename: T
authors.initials: T
authors.lastname: Kammer
authors.forename: H G
authors.initials: HG
authors.lastname: Nusseck
mesh_terms: D015350:Contrast Sensitivity / Q000528:radiation effects*; D004056:Differential Threshold / Q000528:radiation effects; D004574:Electromagnetic Fields; D005108:Extinction, Psychological / Q000528:radiation effects; D006801:Humans; D007266:Inhibition, Psychological; D009778:Occipital Lobe / Q000528:radiation effects*; D010719:Phosphenes; D010812:Physical Stimulation; D012016:Reference Values; D017603:Signal Detection, Psychological / Q000528:radiation effects*; D014792:Visual Acuity