Understanding vertebrate brain evolution

Four major questions can be asked about vertebrate brain evolution:1) What major changes have occurred in neural organization andfunction? 2) When did these changes occur? 3) By what mechanismsdid these changes occur? 4) Why did these changes occur? Comparativeneurobiologists have been very successful in recognizing majorchanges in brain structure. They have also made progress inunderstanding the functional significance of these changes,although this understanding is primarily limited to sensorycenters, rather than integrative or motor centers, because ofthe relative ease of manipulating the relevant stimuli. Althoughneuropaleontology continues to provide important insights intowhen changes occurred, this approach is generally limited torecognizing variation in overall brain size, and sometimes brainregions, as interpreted from the surface of an endocranial cast.In recent years, most new information regarding when neuralchanges occurred has been based on cladistical analysis of neuralfeatures in extant taxa. Historically, neurobiologists havemade little progress in understanding how and why brains evolve.The emerging field of evolutionary developmental biology appearsto be the most promising approach for revealing how changesin development and its processes produce neural changes, includingthe emergence of novel features. Why neural changes have occurredis the most difficult question and one that has been the mostignored, in large part because its investigation requires abroad interdisciplinary approach involving both behavior andecology.