Courtship: Birdsong

Birdsong Ultimate cause: helps attract mates of the same species (males and females benefit) Individual differences exist within a species. Why? Brain development Neuronal activity Adaptive value Reproductive fitness

Same species: Different dialects White crowned sparrows of Northern California are genetically identical

Different dialects: Peter Marler Within a species, birds living in distinct geographical “neighborhoods” sing unique songs Proximate hypothesis 1: genetic variation leads to different nervous system development Proximate hypothesis 2: environmental factors contribute to unique dialects-learn from fathers

Experiments Males raised in isolation-no tutor-never learn to sing a full song Males played tapes of song learn to sing whatever dialect they hear Deaf males sing, but poorly. Feedback is necessary. Birds are especially attuned to songs of their own species.

Time course of song development Song needs to be heard only during the critical period. Critical period is months before any singing is actually done by the young male. Hearing the song of a closely related species in parallel does not inhibit the ability to sing his own song later in life.

Genetics or environment?? Discussion Question Contrast the contributions of the environment and genetics of birdsong learning in general based on the experiments just discussed. What does it mean that white crowned sparrows can learn their conspecific song far more easily than songs of related sparrows? How about the fact that hearing the song during a 40 day period is sufficient to produce the song 5 months later? Genetics or environment??

Social influence on song learning Occasionally birds can be heard singing a song of a related species. Rare, but why does it ever happen? Social interaction: seeing the tutor makes the difference, even when a young male can hear the song of his own species (WC), he will mimic the song of the bird he can see and hear. (SF) Social effects can outlast the critical period, interacting with a non-conspecific tutor after 50 days leads to development of that song, not the species typical song

Neural correlates of birdsong Memories of songs heard during the critical period Song production Auditory feedback/song production matching song memory Particular property of male brain (females do not sing) Genetic? Female bird is ZW, male is ZZ Hormonal? Testosterone, estradiol both implicated Mapping the behavior to the neural mechanisms

Genetic-Environment Interactions Chromosomes determine gonads, gonads secrete hormones, hormones act on receptors in the brain, produce gene expression patterns distinct in male and female brain.

What cellular and molecular changes underlie these different phases What cellular and molecular changes underlie these different phases? The brain must be changing in concert.

Coordinated patterns of gene expression This is a remarkably consistent pattern seen in the male brain of the zebra finch.

What stimuli control the onset of gene expression changes? Auditory input Hearing his tutor’s song during the criticial period Hearing his own song during the sensorimotor phase (150-200 days old) Electrophysiological data suggest that certain neurons in the anterior forebrain become more and more selectively ‘tuned’ to the birds own song vs the tutor’s song i.e. the activity of these neurons is high only when the bird hears itself sing

Role of ZENK High levels of zenk in Area X, a key song control region in the male brain. Levels are high when the male hears the tutor song, and when he attempts to match it with his own song. As he perfects the song, zenk levels drop, suggesting this protein is important in the learning process, not the production. IF Zenk is mediates learning, it would be good to get rid of it once the song is learned so the male doesn’t learn the songs of other species. Zenk is a transcription factor.

Role of FoxP2 (the language gene) Inhibiting foxP2 impairs song production

DQ 2 Females will prefer to stand by a speaker playing a long song by a male of their species than a short song, indicating that females recognize different songs. What role might ZENK play in the female brain? Hypothesis? Experiment to test?