Recent evidence suggests that the expression of GABA(A) receptor subunits is determined by an early innate program which can be further modified by thalamic input and local factors. We analyzed the GABA(A) subunit distribution in experimentally induced subcortical heterotopia which are a subgroup of neuronal migration disorders. Heterotopias consist of clusters of neurons which have stopped migration early, before they have reached their final commitment and well before thalamic afferents have reached their targets. Immuno- histochemical analyses of five important GABA(A) receptor subunits revealed an expression pattern typical for upper cortical layers reflecting the original commitment of the heterotopic neurons. These results point towards detailed innate determinants of cell fate which even contain information on receptor subunit distribution and are not affected by ectopic positioning.