Only rats that received rapid cocaine delivery (the same dose given over five rather than 100 seconds) displayed psychomotor sensitization on the second day of drug delivery. In orbitofrontal and medial prefrontal cortex, nucleus accumbens and caudate-putamen, c-fos and arc mRNAs were increased to a greater extent by fast drug delivery. Finally, rapid delivery resulted in a faster onset and larger block of dopamine reuptake. Such kinetic data may also be important in designing anti-addictive treatments strategies.
2. Sizing up autism in the amygdala and hippocampus: The amygdala is enlarged in children, but not adolescents, with autism; the hippocampus is enlarged at all ages Schumann et al.
This week, Schumann et al. reexamine a controversial aspect of the underlying neuropathology, the differences in the size of brain structures in male children and adolescents with autism and the related Asperger's syndrome. While the cortical size was unaffected, the hippocampus was slightly larger in autistic subjects than controls. Interestingly, the amygdala of children, but not adolescents, was larger with autism, regardless of retardation. The comparison confirmed a 40% increase in the amygdala of normal children between age 7.5 and 18.5 that seems to occur prematurely in autism. Although our understanding of these changes is rudimentary, the role of the amygdala in social interactions provides an intriguing possible connection to autism.