Meeting Abstract
How and why did complex brain and behavior evolve? Clues to the evolution of complexity emerge from comparative analyses of animals with complex brains and those with simple morphology, nervous system and behavioral economics. The brains of vertebrates, arthropods and some annelids have highly derived executive structures and function that control downstream central pattern generators (CPGs) for locomotion, behavioral choice and reproduction. For the vertebrates, these structures – basal ganglia, cortex and hypothalamus – integrate somatotopically mapped sensory inputs with motivation and memory to transmit complex motor commands to relay stations controlling CPG outputs. Similar computations occur in the central complex and mushroom bodies of the arthropods, and in mammals these interactions structure subjective thought and socially based valuations. The simplest model systems available for comparison are opisthobranch molluscs, which have avoided selective pressure for complex bodies, brain and behavior through potent chemical defenses. In particular, in the sea-slug Pleurobranchaea californica the functions of hypothalamus, basal ganglia, cortex and hindbrain are all combined in the feeding motor network and its direct interactions with CPGs for agonist and antagonist behaviors. I will evaluate the unavoidably combined contributions of sexuality, reproductive strategy, nutritional storage, and skeletons to brain evolution.
