title: Crossmodal enhancement of visual orientation discrimination by looming sounds requires functional activation of primary visual areas: a case study.
abstract: Approaching or looming sounds are salient, potentially threatening stimuli with particular impact on visual processing. The early crossmodal effects by looming sounds (Romei, Murray, Cappe, & Thut, 2009) and their selective impact on visual orientation discrimination (Leo, Romei, Freeman, Ladavas, & Driver, 2011) suggest that these multisensory interactions may take place already within low-level visual cortices. To investigate this hypothesis, we tested a patient (SDV) with bilateral occipital lesion and spared residual portions of V1/V2. Accordingly, SDV׳s visual perimetry revealed blindness of the central visual field with some residual peripheral vision. In two experiments we tested for the influence of looming vs. receding and stationary sounds on SDV׳s line orientation discrimination (orientation discrimination experiment) and visual detection abilities (detection experiment) in the preserved or blind portions of the visual field, corresponding to spared and lesioned areas of V1, respectively. In the visual orientation discrimination experiment we found that SDV visual orientation sensitivity significantly improved for visual targets paired with looming sounds but only for lines presented in the partially preserved visual field. In the visual detection experiment, where SDV was required to simply detect the same stimuli presented in the orientation discrimination experiment, a generalised sound-induced visual improvement both in the intact and in blind portion of the visual field was observed. These results provide direct evidence that early visual areas are critically involved in crossmodal modulation of visual orientation sensitivity by looming sounds. Thus, a lesion in V1 prevents the enhancement of visual orientation sensitivity. In contrast, the same lesion does not prevent the visual detection enhancement by a sound, probably due to alternative visual pathways (e.g. retino-colliculo-extrastriate) which are usually spared in these patients and able to mediate the crossmodal enhancement of basic visual abilities such as detection.
authors.affiliation: CsrNC, Centro studi e ricerche in Neuroscienze Cognitive, Alma Mater Studiorum - Università di Bologna, Polo Scientifico-Didattico di Cesena, 47521 Cesena, Italy; Dipartimento di Psicologia, Alma Mater Studiorum - Università di Bologna, 40127 Bologna, Italy; Centre for Cognitive Neuroimaging, Institute of Neuroscience and Psychology, University of Glasgow, Glasgow G12 8QB, United Kingdom.
authors.forename: Roberto
authors.initials: R
authors.lastname: Cecere
authors.affiliation: CBS, Centre for Brain Science, Department of Psychology, University of Essex, Colchester CO4 3SQ, United Kingdom.
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Romei
authors.affiliation: CsrNC, Centro studi e ricerche in Neuroscienze Cognitive, Alma Mater Studiorum - Università di Bologna, Polo Scientifico-Didattico di Cesena, 47521 Cesena, Italy; Dipartimento di Psicologia, Alma Mater Studiorum - Università di Bologna, 40127 Bologna, Italy.
authors.forename: Caterina
authors.initials: C
authors.lastname: Bertini
authors.affiliation: CsrNC, Centro studi e ricerche in Neuroscienze Cognitive, Alma Mater Studiorum - Università di Bologna, Polo Scientifico-Didattico di Cesena, 47521 Cesena, Italy; Dipartimento di Psicologia, Alma Mater Studiorum - Università di Bologna, 40127 Bologna, Italy. Electronic address: elisabetta.ladavas@unibo.it.
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Làdavas
mesh_terms: D000161:Acoustic Stimulation / Q000379:methods; D004192:Discrimination, Psychological / Q000502:physiology; D006323:Heart Arrest / Q000150:complications; D006801:Humans; D002534:Hypoxia, Brain / Q000209:etiology / Q000473:pathology*; D008297:Male; D009949:Orientation; D011930:Reaction Time; D013016:Sound; D014793:Visual Cortex / Q000473:pathology / Q000503:physiopathology*; D014796:Visual Perception / Q000502:physiology*
keywords: Cortical blindness; Looming sounds; Multisensory integration; Visual detection; Visual orientation discrimination