The Zebrafish Habenulae: Abundant Asymmetry in the Dorsal Diencephalon
Caleb A. Doll* and Joshua T. Gamse§
*Neuroscience Graduate Program, Vanderbilt University Medical School, U1205 Medical Center North, Nashville, TN 37232, USA.
§Department of Biological Sciences, Vanderbilt University, Nashville, TN 37235, USA
Correspondence to C.D. e-mail: firstname.lastname@example.org
ABSTRACT | The animal kingdom abounds with examples of asymmetric body plans. In mammals, a gross examination of the visceral organs reveals many of these asymmetries, including the biased placement of the heart, liver, and pancreas along the Left/Right (L/R) axis. A discussion of asymmetry is easily extended to the beautifully complex organization of the brain. For instance, the human cerebral cortex has evolved specialized regions that are specific to one hemisphere; Broca’s area, the locus for speech, is found specifically in the left hemisphere in the vast majority of individuals. In fact, brain asymmetry is quite common throughout the vertebrate lineage, suggesting that lateralized organization is of evolutionary merit and thus contributes adaptive advantages. Although it is difficult to correlate molecular deviations in symmetry with functional consequences in a behaving animal, careful characterization of asymmetrical brain development may eventually unveil the essential components of the nascent lateralized brain.