How does Behavior Change the Brain? Multiple Methods to Answer Old Questions.

SYNOPSIS. Clearly the brain controls behavior but can behavior also ''control'' the brain? On an evolu- tionary time scale, selective ecological pressures shape the sensory and motor capacities as well as the body and behavior. Correspondingly, in development, behavior acts in concert with the environment to cause structural changes in the brain lasting a lifetime. Surprisingly, in ''real time'' social behavior can also cause changes, typically reversible, in the brain in adult animals. Changes caused by behavioral interactions can be dramatic, and in many instances, these interactions are directly related to reproductive behavior. Un- derstanding how behavior sculpts the brain in the course of behavioral interactions is a major challenge. Analyzing such changes requires a model system allowing control of the biological and behavioral environ- ment of many animals simultaneously yet allowing access to physiological, cellular and molecular processes being regulated. The mouthbrooding cichlid Haplochromis (Astatotilapia) burtoni (Gunther) from Lake Tan- ganyika lends itself to the study of social influences on the brain. It has complex, though easily observable individual and social behaviors regulated by two distinct classes of males, those with territories and those without. Many features of the animals are shaped by social encounters including the maturation of juveniles, the hypothalamic-pituitary-gonadal axis, the growth rate, the basal stress level among others. How does social information effect change in the brain and body? Animals must attend to the social scene to identify their chances. Learning how social information is transduced into cellular changes in this species should help understand how this happens in other social animals. Von Uexkull (1921) realized that every species ex- periences life differently because it lives in its own particular ''umwelt,'' or unique perceptual world. For example a bat uses sonic echoes to probe the darkness, forming images from sound reflected off the surround- ings but can also see with its eyes in the ultraviolet, possibly for nectar foraging (Winter et al., 2003) giv- ing it two unique windows on the world. Such sensory capacities define what can be sensed, enabling some and constraining other behavioral responses of an an- imal. Writing at the beginning of the twentieth century, Von Uexkull could not possibly have anticipated the discovery of magnetic, electric or pressure senses, nor could he have imagined a ''visual'' sense extending from the infrared into the ultraviolet. Lorenz (1932) expanded the idea of ''umwelt'' to include not just detection of stimuli from physical surroundings but also from other animals. His influential article, ''Com- panions as factors in the bird's environment,'' showed that behavioral scientists needed to enlarge their views of an animal's perceptual world to include other indi- viduals and their aggregate social context. Behavior is the ultimate arbiter of animal survival and how ani- mals respond during their interactions with others and with the environment shape its phenotype. Yet behav- ior, in turn, depends on intricate physiological, cellular