The corpus callosum is the largest fibre tract in the brain of placental mammals and connects the two cerebral hemispheres. Corpus callosum dysgenesis is a developmental brain disorder that is commonly genetic and occurs in approximately 1:4000 live births. It is easily diagnosed by MRI or prenatal ultrasound and is found in isolation or together with other brain anomalies, or with other organ system defects in a large number of different congenital syndromes. Callosal dysgenesis is a structural brain wiring disorder that can impact brain function and cognition in heterogeneous ways. We aim to understand how early developmental mechanisms lead to circuit alterations that ultimately impact behaviour and cognition. Translated to Spanish by MD and Medical interpreter Trinidad Ott. El cuerpo calloso es el tracto de fibras más grande del cerebro de los mamíferos placentarios y conecta los dos hemisferios cerebrales. La disgenesia del cuerpo calloso es un trastorno del desarrollo del cerebro que comunmente es genético y ocurre en aproximadamente 1: 4000 nacidos vivos. Se diagnostica fácilmente mediante resonancia magnética o ecografía prenatal y se encuentra aislado o junto con otras anomalías cerebrales, o con otros defectos del sistema de órganos en un gran número de síndromes congénitos diferentes. La disgenesia callosa es un trastorno estructural del cableado cerebral que puede afectar la función cerebral y la cognición de formas heterogéneas. Nuestro objetivo es comprender cómo los primeros mecanismos del desarrollo conducen a alteraciones en los circuitos que, en última instancia, afectan el comportamiento y la cognición. Traducción al español por la Doctora e Intérprete Médica Trinidad Ott.

Cases with visuospatial abnormalities provide opportunities for understanding the underlying cognitive mechanisms. Three cases of visual mirror-reversal have been reported: AH (McCloskey, 2009), TM (McCloskey, Valtonen, & Sherman, 2006) and PR (Pflugshaupt et al., 2007). This research reports a fourth case, BS -- with focal occipital cortical dysgenesis -- who displays highly unusual visuospatial abnormalities. They initially produced mirror reversal errors similar to those of AH, who -- like the patient in question -- showed a selective developmental deficit. Extensive examination of BS revealed phenomena such as: mirror reversal errors (sometimes affecting only parts of the visual fields) in both horizontal and vertical planes; subjective representation of visual objects and words in distinct left and right visual fields; subjective duplication of objects of visual attention (not due to diplopia); uncertainty regarding the canonical upright orientation of everyday objects; mirror reversals during saccadic eye movements on oculomotor tasks; and failure to integrate visual with other sensory inputs (e.g., they feel themself moving backwards when visual information shows they are moving forward). Fewer errors are produced under conditions of certain visual variables. These and other findings have led the researchers to conclude that BS draws upon a subjective representation of visual space that is structured phenomenally much as it is anatomically in early visual cortex (i.e., rotated through 180 degrees, split into left and right fields, etc.). Despite this, BS functions remarkably well in their everyday life, apparently due to extensive compensatory mechanisms deployed at higher (executive) processing levels beyond the visual modality.