For full expression, language depends on an interplay between cognitive and motor skills. For example, people with a rare genetic form of developmental verbal dyspraxia have difficulty learning and producing the intricate, coordinated series of muscle movements necessary for speech, a result of a mutation in a brain transcription factor called FOXP2. In songbirds, this same protein is found in a brain region--area X--that is essential for the acquisition of the birds' characteristic song, which they learn under the close tutelage of an adult bird.
Haesler et al. tested whether a deficit in FoxP2 would also produce communication deficits in zebra finches. They injected into area X a lentivirus vector carrying RNA interference sequences from FoxP2, which reduced FoxP2 mRNA by 70%. After the 2-month tutoring period, the treated birds' songs--normally a stereotyped series of syllables that remains stable throughout adulthood--were missing syllables and contained inappropriately repeated segments (errors similar to those of humans with dyspraxia). Some of the sounds were also poor copies of their tutor's original. Thus, without sufficient FoxP2, normal developmental motor learning could not take place. The authors speculate that FoxP2 is necessary for structural and functional changes in area X neurons as birds learn their songs. -- KK
PLoS Biol. 5, e321 (2007).
