Abstract
IntroductionOrganization of tactile input into somatotopic maps enables us to localize stimuli on the skin. Temporal relationships between stimuli are important in maintaining the maps and influence perceived locations of discrete stimuli. This points to the spatiotemporal stimulation sequences experienced as motion as a potential powerful organizing principle for spatial maps. We ask whether continuity of the motion determines perceived location of areas in the motion path using a novel tactile stimulus designed to ‘convince’ the brain that a patch of skin does not exist by rapidly skipping over it.MethodTwo brushes, fixed 9 cm apart, moved back and forth along the forearm (at 14.5 cm s−1), crossing a 10-cm long ‘occluder’, which prevented skin stimulation in the middle of the motion path. Crucially, only one brush contacted the skin at any one time, and the occluder was traversed almost instantaneously. Participants pointed with the other arm towards the felt location of the brush when it was briefly halted during repetitive motion, and also reported where they felt they had been brushed.ResultsParticipants did not report the 10-cm gap in stimulation – the motion path was perceptually completed. Pointing results showed that brush path was ‘abridged’: locations immediately on either side of the occluder, as well as location at the ends of the brush path, were perceived to be >3 cm closer to each other than in the control condition (F(1,9) = 7.19; p = .025 and F(1,9) = 6.02, p = .037 respectively). This bias increased with prolonged stimulation.ConclusionsAn illusion of completion induced by our Abridging stimulus is accompanied by gross mislocalization, suggesting that motion determines perceived locations. The effect reveals the operation of Gestalt principles in touch and suggests the existence of dynamic maps that quickly adjust to the current input pattern.
Highlights
Organization of tactile input into somatotopic maps enables us to localize stimuli on the skin
An illusion of completion induced by our Abridging stimulus is accompanied by gross mislocalization, suggesting that motion determines perceived locations
Spatial organization of sensory input is common in the cortex, including the organization of tactile input into somatotopic maps
Summary
Organization of tactile input into somatotopic maps enables us to localize stimuli on the skin. Spatial organization of sensory input is common in the cortex, including the organization of tactile input into somatotopic maps This organization enables us to localize stimuli on the skin and perform other spatial tasks [1], [2]. The relocation created new spatial relationships between previously remote skin patches This naturally brought about a change in the temporal pattern of their inputs, such that the new neighboring locations were co-stimulated with high probability. The receptive fields of cortical neurons changed, reflecting the new neighborhood relations, and have been described as ‘time-based constructs’ [7] Findings like these motivated an extension of formal self-organizing models to include temporal stimulus structure [8]
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