You read this paragraph by mostly using resources of your left hemisphere. But is the asymmetry of your brain realized at the neuronal level and how does it emerge during your lifetime? The pigeon’s visual system is an excellent model to find answers for these questions. Now, Biopsychologists from Bochum have published a review on 20 years of asymmetry research in this model. They describe how lateralized visual stimulation induces structural asymmetries within the brain of the embryo during a critical time window, and how these early asymmetrical signals shape the nervous system into a lateralized structure. Interhemispheric control mechanisms seem to stabilize these induced asymmetries. The functional left-right differences are then established due to the interplay between bottom-up and top-down mechanisms that generate a lateralized, hemispheric-specific visual analysis.

Manns, M. and Güntürkün, O., Dual coding of visual asymmetries in the pigeon brain – the interaction of bottom-up and top-down systems, Exp. Brain Res., 2009, 199: 323-332.