ABSTRACT
The question of laterality, symmetry and other features related to laterality have now been reinstated as of fundamental importance to modern neuroscience. It may be said that the brain structure of fishes is as far removed from man as is possible within the vertebrates and if asymmetry was a unique feature of the brain of man then it should distinguish the brain of fish least of all. The habenular nuclei are a focus for asymmetry in the amphibian brain as well as the fish brain. In one study of fifty frog brains all without exception showed a striking asymmetry of this structure. The range of cerebral asymmetry is wide, including gross anatomical asymmetry as well as subtle functional differences. Some of the asymmetries could be mere accidents of nature, perpetuated only because they remained neutral with respect to the question of survival.
