ABSTRACT
Cortical malformations are commonly associated with developmental delays, dyslexia, and certain forms of mental retardation. It is generally assumed that the functional disorders observed in individuals with brain malformations are the result of disturbances in the cells and/or circuits associated with the malformations. However, in most cases, the relation between a structural malformation and its associated functional deficit is not well characterized. This chapter examines structural abnormalities and behavioral deficits that occur in a seizure-prone animal (the tish rat). This animal exhibits large groups of misplaced neurons in the neocortex, termed subcortical band heterotopia. Seizure activity in the tish brain does not appear to emanate from the cortical heterotopia, but rather from the normal-appearing areas of 244cortex neighboring the heterotopia. In addition, the behavioral deficits observed in this animal occur, at least in part, in a manner that is independent of the primary cortical malformation. These latter findings suggest that other, more subtle disturbances in neural cells and/or their circuitries can play a key role in functional disturbances associated with cortical malformations.
