Of mice, birds, and humans: The mouse ultrasonic song system has features similar to humans and song-learning birds Erich D. Jarvis Duke University Medical Center Howard Hughes Medical Institute Department of Neurobiology October 9th, 2012

Researchers – mouse song project Erich Jarvis, PhD Project leader Professor Duke Univ Senior-author Gustavo Arriaga, PhD (Graduate student) Graduated May 2011 1-st author Eric Zhou, BA Graduated May 2010 Now in Medical School 2nd-author

Convergent behavior: vocal learning – substrate for speech AVIAN FAMILY TREE only humans * * Hackett et al 2008 tree * * Depends on auditory feedback, vocal critical periods, cultural transmission, syntax,… Deaf-induced vocal disorders, aphasias, speech sound disorder, autism,… Vocal learners

Are mice vocal learners or not? Never tested! Goal was to test hypothesis using vocal non-learning species: chicken for birds and mice for mammals Holy and Guo showed mice have songs with acoustic features like song learning birds? Mouse song in real time Hypothesis about evolution of vocal learning trait: birds and mammals Project to identify axon guidance molecule mutations unique to vocal learners, and then manipulate them. Needed to use mice as controls. But mouse songs like songbird songs – Guo and Holly 2005 sonograms and recordings Could not find any study that tested vocal learning and the mouse song system So we set out discover the system and test whether or not these vocalizations have traits of vocal learners. Mouse song slowed Individual differences Are mice vocal learners or not? Never tested! Holy and Guo 2005 PLoS Biol

1. Mouse singing-driven gene expression A1 brainatlas.mbi.ufl.edu Activated brain regions: ambiguus, central grey, motor cortex, striatum, auditory cortex Comparison with learners and non-learners In-situs of ambiguus, laryngeal motor cortex, underlying dorsal striatum, and auditory cortex (olfactory bulb, ventralateral thalamus) Quantifications arc, egr1 Arriaga, Zhou, Jarvis 2012 From Figure 2

Exclusively in Layer V neurons of singing-induced M1 cortex region II III IV V VI Cg Is the connection direct or indirect. Inject BDA tracer into motor cortex region and simultaneously inject Cholera Toxin B into laryngeal muscles to backfill ambiguus motor neurons. 8 animals on target, bilaterally. Found projection to lateral dorsal striatum, same location as singing regulated gene expression: brightfield to darkfield Arriaga, Zhou, Jarvis 2012 From Figure 3

Singing activated M1 projects directly to vocal motor neurons (Amb) But projection is sparse: 1-2 axons per motor neuron Arriaga, Zhou, Jarvis 2012 From Figure 3

2. Mouse song system connectivity more similar to songbird and human Arriaga, Zhou, Jarvis 2012 From Figure 1

3. Posterior vocal motor pathway produces learned vocalizations X X X X EXPERIMENT 3: Motor cortex lesion (n=5) Visual cortex lesion (n=5) Sham surgery (n=6) Eliminate song production Innate calls intact Eliminate song/speech production Crying/laughing intact Lesions: in vocal learners Nottebohm et al 1976 J Comp Neurol

Experiment 3. M1 laryngeal cortex lesions Record song, ibotenic acid lesion, record song again, backfill with PRV and verify lesion. down jumps up jumps Lead to greater singing variation: aphasia of song? Arriaga, Zhou, Jarvis 2012 From Figure 4

Deafened mice show some song deterioration Caspase-3 a cystein proteases that play essential roles in programmed cell death. CASP3 KO causes loss of ear hair cells by 1 month (Takahasi et al 2001 Brain Res) Arriaga, Zhou, Jarvis 2012 From Figure 5

5. Song pitch convergence caused by competitive social experience Co-house adult C57 males + BxD males that sing at different pitches in the presence of either a C57 female or BxD female Arriaga, Zhou, Jarvis 2012 From Figure 6

Traits unique to vocal learners Vocal non-learners** Mice BRAIN Cortical & striatal brain regions active in vocal production YES NO Direct forebrain projection to brainstem vocal motor neurons YES, sparse Require vocal motor cortex to produce learned vocalizations YES, partial BEHAVIOR Require auditory feedback to develop and maintain vocalizations: deafened-induced vocal deterioration Vocal imitation YES, pitch What is vocal learning? Traits unique to vocal learners: In brain: Use of the cortical/pallial regions active in producing vocalizations Direct projection from motor cortex to vocal motor neurons. Requirement of the cortex to produce and learn vocalizations Behavior: Requirement of auditory feedback to maintain vocalization Imitation of sounds of heard *Vocal learners: e.g. humans, songbirds, parrots, hummingbirds. **Vocal non-learners: e.g. non-human primates, cat, chicken, pigeon Reviewed in: Doupe & Kuhl 1999 Ann Rev Neurosci; Hauser et al 2002 Science; Jarvis 2004 Ann NY Acad Sci; Jurgens & Ehrenreich 2007 Brain Res; Fischer & Hammerschmidt 2010 Genes, Brain & Behav.

Summary We propose that vocal learning is not dichotomous, but a continuous trait. Mice are limited vocal learners, in the middle. Mice might serve as genetic models for some properties thought unique to humans for speech-language disorders. Given the convergent behavior, neural networks, and genetics for vocal learning, it is theoretically possible to genetically enhance the circuit. chicken macaque mice songbird human Vocal learning and brain pathway continuum (not solely based on species related)

NIH Director’s Pioneer Award Howard Hughes Medical Institute Funding for projects presented NIH Director’s Pioneer Award Howard Hughes Medical Institute NIDCD R01-DC007218

Big questions EITHER Mice are more similar to humans and song learning birds for vocal communication traits than are non-human primates are to humans OR Much of the last 50 years of research on differences between vocal learners and non-learners needs to be re-evaluated