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Genes for speech may not be limited to humans

Vocal communication in mice is affected by the same gene needed for human speech.

Our current understanding is that mice have either no — or extremely limited — neural circuitry, or genes, similar to those that regulate human speech. According to a recent study published in Frontiers in Behavioral Neuroscience — this may be wrong.

Dr. Jonathan Chabout is the lead author of the paper, whose principal investigator is Dr. Erich Jarvis. Dr. Jarvis and colleagues report their results on the effect of a genetic mutation in the Forkhead box protein #2 (FOXP2) on vocal patterns of adult male mice.

FOXP2 regulates speech production in humans.

Humans with deficiencies in FOXP2 protein have difficulty forming complex syllables and sentences.

Although mice are unable to communicate using speech in the same way as humans, they do vocalize to communicate with each other. Therefore, this study wanted to determine whether FOXP2 deficiencies have similar consequences in communication by mice as they do in humans.

They do.

Males Sing Syllables at Louder, Longer, Higher Pitch
in Response to Fresh Female Urine, but Sharper to Awaken Females

Dr. Jarvis suggests his study supports the "continuum hypothesis" which is that FOXP2 affects the vocal production of all mammals not just humans.

Dr. Jarvis' team investigated twenty-six (26) male mice bred to have the same FOXP2 mutation as found in humans with speech deficits, and twenty-four (24) "wildtype" male mice (i.e., mice with a normal level of FOXP2 protein).

Both types of male mice (1. heterozygous mice containing the FOXP2 mutation and 2. wildtype mice) were placed in several unique situations — housed with a wildtype female mouse, or only the urine of wildtype females, or housed with a sleeping female, or sleeping male mouse. These choices were based on prior research published by Chabout and colleagues in 2015.

The past study found that in various social situations, healthy males produce differences in the sequence and duration of ultrasonic vocalizations (USVs) — high pitched sounds inaudible to us — that mice sing.

In their new study, investigators wanted to determine if a FOXP2 deficiency affects communication patterns in mice. Results showed that FOXP2 heterozygotes (mice with two different mutations of FOXP2) have difficulty producing complex vocal patterns. Wildtype mice can create these vocal patterns with ease. All vocalizations were measured for syllable length and number of unique syllables over time.

These differences are particularly strong when FOXP2 heterozygotes and wildtype males were in the presence of female mice. Wildtype males were 3 times as likely to produce more complex syllable types and sequences — as heterozygotes. Dr. Jarvis' team conducted intricate statistical analyses to validate this finding, and the conclusion held.

Dr. Jarvis' team used transsynaptic tracing of mouse vocal larynx muscles to compare vocal brain regions of wildtype and heterozygote FOXP2 mice, at the end of all recordings. This revealed heterozygote's vocal motor neurons were more widely distributed across their cortex than in wildtype mice. This suggests a FOXP2 mutation affects both placement as well as function of neurons affecting communication, in both mice and humans.

Prior research had shown a more limited role for FOXP2 than what is becoming apparent.

Dr. Jarvis: "We believe that FOXP2 already had a pre-existing role in regulating vocal communication long before human language evolved."

In 2005, Holy and Guo advanced the idea that male mice produce ultrasonic vocalizations (USV) with some features similar to courtship songs of songbirds. Since then, studies showed that male mice emit USV songs in different contexts (sexual and other) and possess a multisyllabic repertoire. Debate still exists for and against plasticity in their vocalizations. But the use of a multisyllabic repertoire can increase potential flexibility and information, in how elements are organized and recombined, namely syntax. In many bird species, modulating song syntax has ethological relevance for sexual behavior and mate preferences. In this study we exposed adult male mice to different social contexts and developed a new approach of analyzing their USVs based on songbird syntax analysis. We found that male mice modify their syntax, including specific sequences, length of sequence, repertoire composition, and spectral features, according to stimulus and social context. Males emit longer and simpler syllables and sequences when singing to females, but more complex syllables and sequences in response to fresh female urine. Playback experiments show that the females prefer the complex songs over the simpler ones. We propose the complex songs are to lure females in, whereas the directed simpler sequences are used for direct courtship. These results suggest that although mice have a much more limited ability of song modification, they could still be used as animal models for understanding some vocal communication features that songbirds are used for.

Citation: Chabout J, Sarkar A, Patel SR, Radden T, Dunson DB, Fisher SE and Jarvis ED (2016) A Foxp2 Mutation Implicated in Human Speech Deficits Alters Sequencing of Ultrasonic Vocalizations in Adult Male Mice. Front. Behav. Neurosci. 10:197. doi: 10.3389/fnbeh.2016.00197

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Nov 18, 2016   Fetal Timeline   Maternal Timeline   News   News Archive   

Duke University neurobiologists Gustavo Arriaga (left) and Erich Jarvis
watch as a mouse sings its ultrasonic tune in the lab.
Image Credit:
Jared Lazarus/Duke University


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