Academic journal article Canadian Journal of Experimental Psychology

Failure to Remap Visuotactile Space across the Midline in the Split-Brain

Academic journal article Canadian Journal of Experimental Psychology

Failure to Remap Visuotactile Space across the Midline in the Split-Brain

Article excerpt

Abstract We examined the effect of posture change on the representation of visuotactile space in a split-brain patient using a cross-modal congruency task. Splitbrain patient J.W. made speeded elevation discrimination responses (up versus down) to a series of tactile targets presented to the index finger or thumb of his right hand. We report congruency effects elicited by irrelevant visual distractors placed either close to, or far from, the stimulated hand. These cross-modal congruency effects followed the right hand as it moved within the right hemispace, but failed to do so when the hand crossed the midline into left hemispace. These results support recent claims that interhemispheric connections are required to maintain an accurate representation of visuotactile space.

Resume A l'aide d'une tache de congruence intermodale, nous avons etudie l'effet du changement de posture sur la representation de l'espace visuo-tactile chez un patient a cerveau divise. J.W., un patient callos-tomise, devait executer, le plus rapidement possible, des reponses discriminatives d'elevation (haut/bas) a une serie de cibles tactiles presentees A Findex ou au pouce de sa main droite. Nous avons note des effets de congruence suscites par des distracteurs visuels non pertinents, qu'ils aient ete A proximite ou non de la main stimulee. Ces effets de congruence intermodale se sont manifestees tant que la main droite se deplacait dans l'hemichamp droit, mais ont disparu lorsqu'elle franchissait la methane et penetrait dans l'hemichamp gauche. Ces resultats corroborent des conclusions recentes selon lesquelles les connexions interhemispheriques sont essentielles au maintien d'une representation exacte de l'espace visuo-tactile.

In recent years, researchers have begun to investigate how the brain integrates information from different sensory modalities. Evidence from an ever-growing variety of research methodologies has started to converge on a number of common conclusions regarding the rules underlying multisensory integration and attention in humans and other species (e.g., Calvert, Brammer, & Iversen, 1998; Driver & Spence, 1998, 2000; Stein, London, Wilkinson, & Price, 1996; Welch & Warren, 1986, for reviews).

One major source of evidence comes from neuropsychological studies demonstrating that brain damage can profoundly alter the normal processes of multisensory integration and attention (e.g., di Pellegrino, Ladavas, & Farne, 1997; Farne, Pavani, Meneghello, & Ladavas, 2000; Halligan, Hunt, Marshall, & Wade, 1996; Maravita, Spence, Clarke, Husain, & Driver, 2000; Mattingley, Driver, Beschin, & Robertson, 1997; Rorden, Heutink, Greenfield, & Robertson, 1999). For example, di Pellegrino et al. reported data from a patient with left-sided extinction (caused by a righthemisphere lesion) who could detect tactile stimulation on the impaired (contralesional) left hand when presented in isolation, but was typically unaware of the same left-hand stimulation (which was thus "extinguished" from awareness) if a visual stimulus was presented simultaneously from close to the right hand. Importantly, this crossmodal extinction effect was shown to depend on the current proximity of visual information and tactile events in external space (di Pellegrino et al., 1997; Ladavas, di Pellegrino, Farne, & Zeloni, 1998). When taken together with recent results from behavioural (e.g., Pavani, Spence, & Driver, 2000; Soto-Faraco, Spence, Fairbanks, Kingstone, Hillstrom, & Shapiro, 2001; Spence, Pavani, & Driver, 1998), neuroimaging (e.g., Macaluso, Frith, & Driver, 2000a, 2000b), and electrophysiological studies (e.g,, Graziano, Cooke, & Taylor, 2000; Graziano & Gross, 1993), it becomes clear that we may soon begin to bridge the gap between single-cell data and human perceptual experience. In the present manuscript, we focus on neuropsychological research investigating the integration of visual, tactile, and proprioceptive information in the representation of visuotactile space in a split-brain patient. …

Search by... Author
Show... All Results Primary Sources Peer-reviewed

Oops!

An unknown error has occurred. Please click the button below to reload the page. If the problem persists, please try again in a little while.