TrkB-BDNF Signaling in Experience-Dependent Molecular Plasticity in Zebra Finches

Development of an organism's phenotype is not solely the result of genetics, but also integration of external environmental inputs, i.e. experience-dependent processes. Zebra finch sensory song learning, behaviorally and neurologically analogous to human speech acquisition, offers a powerful model for examining the intersection of age and experience especially during sensitive windows of development and their underlying molecular mechanisms. Within both male and female zebra finches, the auditory lobule (AL), has been signified to play a crucial role in sensory song learning. In the AL, manipulations of signaling cascades, ERK and mTOR, result in behavioral deficits in song recognition and song learning, implicating ERK and mTOR as necessary to sensory song learning. However, an upstream point of regulation of these cascades has not been established. This pilot project investigates trkB-BDNF signaling, a pathway heavily implicated in experience-dependent plasticity, learning and memory, neuronal survival and circuit development, and central nervous system (CNS) maintenance. TrkB-BDNF may also act as an upstream trigger for developmentally and sensory learning relevant cascades, ERK and mTOR. To test trkB-BDNF's role in zebra finch song learning, BDNF signaling was manipulated throughout their developmentally sensitive windows during controlled tutor sessions, with behavioral outcomes measured by quantitative comparison to the tutor's song. Pilot results suggest that trkB-BDNF may be necessary for sensory song learning. However, due to additional confounds and a restricted sample size, further trials continuing this project are warranted. Establishing this role will clarify trkB-BDNF's contribution to sensory memory formation, molecular plasticity, and provide further understanding of molecular mechanisms underlying experience-dependent processes.