Christopher R. Olson, Ph.D.

Assistant Professor

Research in the Auditory and Vocal Learning Laboratory at Midwestern University

My laboratory uses the zebra finch model to better understand issues of human health that are challenging to study on their own. These include the alcohol effects on vocal learning and brain function, and the role of vitamin A deficiency in cognition and vocal learning. Both of these are well known to affect human health, but their effects are extremly challenging to study in the human brain. Songbirds are a powerful model to investigate properties of the nervous system as it relates to complex behaviors and learning, and the zebra finch is well suited to address these hard to study problems that are significant to humans. Spring-boarding off previous work that identified the roles of Vit.A/retinoid signaling pathways in vocal maturation, I have investigated the relevance of vitamin A deficiency, a major global human health issue, to vocal learning and neuronal function. An important follow-up to the vitamin A study was the finding that ethanol, which shares its metabolic pathways with retinoid synthesis, has major effects on acoustic properties of the learned vocalizations of the finch. 

Project 1: Alcohol effects on vocal development and underlying vocal brain circuits
Aim 1A. How does alcohol exposure affect the ability to learn tutor song? Using specially designed cages we are testing the effect that alcohol has on vocal learning in tutor-pupil learning paradigms.
Aim 1B. How does the timing of alcohol ingestion affect brain gene expression? Alcohol acutely alters vocal learning, vocal variability and brain gene expression. However, the prolonged effects are not understood. I will test how binge-like alcohol exposure affects vocal behavior and brain function at several points during and after its exposure.
Aim 1C. Are alcohol effects mediated through dopamine signaling pathways? Zebra finch vocal learning and production is mediated through dopamine signaling, a neurotransmitter system that is known to be altered by alcohol in the brain. We are developing methods to use pharmacological blockade of dopamine receptors (DR1s and DR2s) in an attempt to reverse deleterious effects of alcohol on vocal variability.

Project 2: Ontogeny of retinoic acid signaling in the zebra finch vocal circuit
Aim 2.  Describe the ontogeny of Vitamin A signaling in the song circuit through expression of ALDH1A2. Vitamin A signaling is essential for the development of vocal learning in the finch. However, the dynamics and transport of the bioactive form of Vit. A (all-trans retinoic acid) in functioning brains is not well described. I will use in situ hybridization and Immunohistochemistry techniques to describe Vit. A signaling through the brain distribution of the terminal enzyme for retinoic acid synthesis, ALDH1A2, and other enzymes in this synthesis pathway, its receptors (RAR/RXR) and retinoid binding proteins.

Project 3: Comparative vocal neuroanatomy in vocal learning and non-learning hummingbirds
Aim3: I am investigating the vocal neuroanatomy of  several hummingbird species that vary in their ability to produce learned vocalizations.  Some hummingbird species and lineages of Passeriform songbirds (e.g. the suboscine flycatchers), many found in Arizona in robust wild populations, do not produce organized song. This is despite extensive efforts by naturalists to describe the vocalizations of these species, thus the consensus view is that these species have not evolved vocal learning. Alternatively, recent phylogenetic analyses reveal that vocal learning was most likly present in ancestral species, meaning that vocal learning was lost in the lineages that do not exhibit it. To understand the neurobiology of a trait that is fundamental to human language acquisition, we aim to examine brains for vocal circuits of these species using established methods with molecular markers of Anna's hummingbird and zebra finch vocal circuitry. To do this I am performing detailed histological and molecular reconstructions of vocal neuroanatomy utilizing thin section tissue microscopy. Furthermore, there is a nearly complete lack of knowledge of the hummingbird vocal organs (syrinx and trachea) as well as key sensory organs (e.g. the cochlea) that are fundamental to vocal production and auditory perception. Thus efforts in my lab are underway to preserve tissues from vocal learners and putative non-learners, for a through histological description.

Past Projects
My research has its roots in studying the ecology, physiology and life-history evolution of free-living birds. More broadly work in my lab focuses on the environmental factors that drive an animal's physiological and neurobiological development. I initially participated in field studies with white-crowned sparrows where we sought to understand constraints in breeding energetics during different stages of reproduction and different modes of migration and elevational dispersion.

I also participated in a study that examined life-history strategies between phylogenetically-paired species that live in north-temperate (Arizona) and sub-tropical (Argentina) communities, a 3-year study that culminated in a significant revision in how we understand the effects of resources (Lackian) and predation (Skutchian) on reproductive effort. I have significant natural-history expertise, and my broad experience in avian biology recently took me to the Atlantic Forest of Brazil to study some unique ultrasonic vocalizations of a hummingbird and the possible high frequency perception of these vocalizations. 

My doctoral research at Iowa State University used songbirds as models of temperature-sensitive embryonic development, where I identified physiological and morphological consequences to frequent periodic cooling, and established that condition is an important factor that parent birds must consider when they leave the nest to forage. This parent-offspring conflict that occurs during avian development has been central to understanding broader issues of life-history evolution, clutch size and latitudinal clines (tropical-temperate) in reproductive strategies.

Later as a postdoc at Oregon Health & Science University I continued this research theme with the songbird model to understand the molecular changes that occur in the neural vocal circuitry as the juvenile bird goes through different critical periods of vocal learning, with the premise that these molecular events are critical to allowing the bird to detect and respond to tutor cues necessary to learn a complex song. Specifically, I have focused on the developmental changes in the retinoic acid signaling pathway, as that pathway is critical for vocal maturation, but have also identified a number of different genes that change expression in the vocal circuitry at various times during the vocal learning period.