Action blindsight and antipointing in a hemianopic patient

• Published in: Neuropsychologia Vol. 128; pp. 270 - 275
• Main Authors: Smits, A.R., Seijdel, N., Scholte, H.S., Heywood, C.A., Kentridge, R.W., de Haan, E.H.F.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.05.2019
• Subjects: Action blindsight; Attention; Blindness - diagnostic imaging; Blindness - etiology; Blindness - psychology; Hemianopia; Hemianopsia - complications; Hemianopsia - diagnostic imaging; Hemianopsia - psychology; Humans; Magnetic Resonance Imaging; Male; Photic Stimulation; Pointing; Psychomotor Performance; Residual vision; Spatial localisation; Vision, Ocular; Visual Cortex - diagnostic imaging; Visual Cortex - physiopathology; Visual Fields; Visual Perception; Young Adult; Pointing; Hemianopia; Action blindsight; Residual vision; Spatial localisation
• ISSN: 0028-3932; 1873-3514
• DOI: 10.1016/j.neuropsychologia.2018.03.029

Blindsight refers to the observation of residual visual abilities in the hemianopic field of patients without a functional V1. Given the within- and between-subject variability in the preserved abilities and the phenomenal experience of blindsight patients, the fine-grained description of the phenomenon is still debated. Here we tested a patient with established “perceptual” and “attentional” blindsight (c.f. Danckert and Rossetti, 2005). Using a pointing paradigm patient MS, who suffers from a complete left homonymous hemianopia, showed clear above chance manual localisation of ‘unseen’ targets. In addition, target presentations in his blind field led MS, on occasion, to spontaneous responses towards his sighted field. Structural and functional magnetic resonance imaging was conducted to evaluate the magnitude of V1 damage. Results revealed the presence of a calcarine sulcus in both hemispheres, yet his right V1 is reduced, structurally disconnected and shows no fMRI response to visual stimuli. Thus, visual stimulation of his blind field can lead to “action blindsight” and spontaneous antipointing, in absence of a functional right V1. With respect to the antipointing, we suggest that MS may have registered the stimulation and subsequently presumes it must have been in his intact half field. •Tested for "action" blindsight a hemianopic patient with established "perceptual" blindsight.•Ability to localise targets in his blind field by pointing, without acknowledge awareness suggesting additional "action blindsight".•Occasionally, patient exhibited spontaneous antipointing behaviour.•(f)MRI revealed a structurally disconnected residual right calcarine sulcus, not activated by visual stimuli.