Welcome to the Healey webpage

 

Healey Lab Research - Behavioral Physiology

The forebrain of vocal learning species, such as humans and songbirds, has several features in common, including local production of steroid hormones (estrogens and androgens). Changes in local steroid levels within forebrain circuits can therefore influence communication behavior and vocal learning. We study these phenomena in songbirds using a variety of technical approaches including in vivo microdialysis, electrophysiology, immunocytochemistry, and neuropharmacology. Songbirds offer a unique model system in which brain steroid production is widespread and especially pronounced, and in which the development and expression of a suite of social behaviors is accessible in the laboratory and natural environments.

We use songbirds as a model of vocal learning and brain plasticity to examine questions such as:
Why does the brain produce its own supply of estrogens?
What neural and endocrine events occur when young birds learn to sing?
What brain regions are important for song processing and song memory?
What does the study of vocal learning in songbirds tell us about brain function in other vocal learning species, like human beings?


Why does the brain produce its own supply of estrogens?


Steroids, like estrogens and androgens, are produced within discrete neural circuits in the cortex of humans and songbirds. In songbirds, the estrogen-synthetic enzyme aromatase is expressed in both neuronal cell bodies and presynaptic boutons in forebrain circuits. Neuroestrogens can therefore influence behavior via local and acute actions within behavioral circuits. These actions are not well understood, in part because steroids have historically been associated with long-term events like puberty, seasonality, and sexual differentiation. Using a variety of methodological approaches we are testing the hypothesis that steroids act in a fast, localized manner very similar to neurotransmitters in the vertebrate nervous system.


What neural and endocrine events occur when young birds learn to sing?


An ensemble of neural, neurohormonal, and neurogenetic mechanisms are activated when adult songbirds hear auditory stimuli such as song. We are studying how these mechanisms contribute to the complex task of vocal learning in juvenile birds during development. Throughout the critical developmental stages of song learning we examine the electrical and neuromodulatory properties of neurons that contribute to song learning.


What brain regions are important for song processing and song memory?


The songbird forebrain contains a network of brain circuits that are involved in the highly complex process of singing. These structures are devoted to the processing of song, matching vocal output with neural templates, discriminating among individual song types, and storing long-term memories of individual songs. Our lab is investigating how the forebrain song circuit is modulated to enable these complex cognitive tasks.  


What does the study of vocal learning in songbirds tell us about brain function in other vocal learning species, like human beings?


Songbirds learn to vocalize according to a developmental timeline that parallels the process of human speech learning. Shared principals include a linear sequence of discrete stages, including a sensory phase (listening and classifying vocalizations and storing vocal memories), and a sensorimotor phase (‘babbling’ or practicing vocal elements and matching them against memorized sequences). Therefore, since zebra finches can be reared and studied in the laboratory they offer a rich and tractable model for studying the mechanisms of vocal learning. Our lab is particularly interested in how brain plasticity is guided and shaped by neurohormonal events. The ultimate goal of this work is to improve our understanding of how vocal circuits are modulated, in order to optimize the development of neuro-therapeutic agents for human communication disorders.