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Mutations in the doublecortin gene cause cortical malformations ('double cortex') in humans, but oddly, mice deficient for the gene appear normal. Joseph LoTurco and colleagues now use RNA interference to reduce doublecortin levels in rats and mice and report a disruption of radial migration, with cells stopping prematurely below or within incorrect layers of the developing neocortex. In addition to verifying the importance of DCX function during cortical development, the study also sends a cautionary message about conclusions drawn from gene knockout approaches. (pp 1245 and 1277)
White people who have difficulty implicitly pairing black names with positive words also tend to be impaired on tasks requiring cognitive control after interacting with a black experimenter. A new functional imaging study finds that such subjects also show more activity in brain regions associated with cognitive control when looking at black faces that are irrelevant to their task.
Presynaptic inhibition of cutaneous afferents influences sensory-motor responses in the spinal cord. In-vivo recordings in monkeys now show that this process suppresses the transmission of cutaneous signals generated during volitional movement.
Confusing results from gene deletion experiments have left the importance of doublecortin (DCX) during brain development unclear. A report in this issue establishes a definitive function for DCX and highlights limitations of gene knockout approaches.
A recent study in Nature shows that the columnar fate of motor neurons in the embryonic spinal cord is imposed by cross-repressive patterns of Hox-c expression. This Hox expression is in turn controlled by graded FGF signaling.