Monday, 17 November 2008

Are you trying to impress me?

November 16, 2008, By Greg Miller

Even male zebrafinches need a bit of inspiration to do their best work. In her lecture here Saturday night, University of California, San Francisco neuroscientist Allison Doupe described how male finches tighten up their performance when a female is in view. With no one around, a male zebrafinch is liable to botch a few notes in his well-practiced song: sometimes he's a little flat, sometimes a little sharp. But with a fine-feathered female listening from a neighboring cage, he's more likely to hit all the right notes. Doupe's lab has been investigating the underlying neurophysiology, and she thinks this line of study may ultimately help clarify the function of the basal ganglia--a part of the brain that's crucial for learning skilled movements and one that's affected by several neuropsychiatric disorders.
In one experiment, Mimi Kao in Doupe's lab used microelectrodes to record the activity of neurons in a brain region called LMAN, a component of the avian basal ganglia. When a male finch sang to a female, LMAN neurons fired in a predictable pattern, with individual neurons firing when he sang a particular element of the song. But when the same male sang on his own, the pattern deteriorated and became less precise--much like his song.
When it comes to singing, Doupe suspects that the male zebrafinch brain has two modes: a performance mode, in which he tries to nail every note, and an "exploratory" or "singing in the shower" mode, in which he loosens up a bit and lets more variability creep in. Theoretical neuroscientists have proposed that variability--in the form of slightly sloppy execution of a movement or behavior--may actually help refine that behavior. Flipping back and forth between these two modes, Doupe said, would enable a bird to give it his best shot when it counts, while continuing to perfect his repertoire when he doesn't have an audience. (And the females do notice the difference: given a choice, they'll sidle up to a speaker playing a "performance" piece, Doupe's lab has found).
Doupe proposes that switching between performance and exploratory modes may be a crucial part of what the basal ganglia does, and she argues that figuring out how this switch works in songbirds could have implications for understanding human disorders associated with basal ganglia damage. Could a switch stuck in performance mode produce symptoms such as the rigidity of Parkinson's disease or the repetitiveness of obsessive compulsive disorder? Would a switch stuck in exploratory mode result in the erratic movements of Huntington's disease? Perhaps these questions are for the birds.

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