Diffusion Tensor Imaging is a MRI modality that allows for characterization of brain tissue and visualization of nerve tracks based on measurements of the diffusion of water molecules.
Analysis by DTI of the starling brain during the spring reproductive season (April; a,c) and in the summer non-breeding season (July; b,d) demonstrates extensive plasticity in connectivity. This MRI approach first confirms the important variation of the connection of HVC to RA between April and July. This projection is denser during the spring (increased axonal density and myelination; see arrows in parts a and b).
In conclusion, repeated in vivo DTI thus identified an unexpected degree of plasticity, resulting in optimized connections in April (larger numbers of axons and/or increased myelination) that might prepare birds for the demanding behavioral tasks conditioning successful reproduction.