Editing Bird vocalization (section)

==== Mirror neurons and vocal learning ====
A [[mirror neuron]] is a [[neuron]] that discharges both when an individual performs an action and when he/she perceives that same action being performed by another.<ref name="Rizzolatti, G. 2004">{{cite journal|last1=Rizzolatti |first1=Giacomo|last2=Craighero |first2=Laila |s2cid=1729870|year=2004|title=The mirror-neuron system|journal=Annu. Rev. Neurosci.|volume=27|pages=169–192|doi=10.1146/annurev.neuro.27.070203.144230|pmid=15217330}}</ref> These neurons were first discovered in [[macaque]] monkeys, but recent research suggests that mirror neuron systems may be present in other animals including humans.<ref>{{cite journal|author1=Oberman, L. M.|author2=Pineda, J. A.|author3=Ramachandran, V. S.|year=2007|title=The human mirror neuron system: A link between action observation and social skills|journal=Social Cognitive and Affective Neuroscience|volume=2|issue=1|pages=62–66|doi=10.1093/scan/nsl022|pmc=2555434|pmid=18985120}}</ref>[[File:Song selective HVCx neurons.svg|thumb|300px|'''Song selectivity in HVCx neurons:''' neuron activity in response to calls heard (green) and calls produced (red). '''a.''' Neurons fire when the primary song type is either heard or sung. '''b, c.''' Neurons do not fire in response to the other song type, regardless of whether it is heard or sung.<ref name="Prather2008">{{cite journal|author1=Prather J. F.|author2=Peters S.|author3=Nowicki S.|author4=Mooney R.|year=2008|title=Precise auditory-vocal mirroring in neurons for learned vocal communication|journal=Nature|volume=451|issue=7176|pages=305–310|doi=10.1038/nature06492|pmid=18202651|bibcode=2008Natur.451..305P|s2cid=4344150}}</ref>]]

Mirror neurons have the following characteristics:<ref name="Rizzolatti, G. 2004"/>
* They are located in the [[premotor cortex]].
* They exhibit both sensory and motor properties.
* They are action-specific – mirror neurons are only active when an individual is performing or observing a certain type of action (e.g., grasping an object).

Because mirror neurons exhibit both [[sensory neuron|sensory]] and [[motor neuron|motor]] activity, some researchers have suggested that mirror neurons may serve to map sensory experience onto motor structures.<ref name="Dinstein, I. 2008">{{cite journal|author1=Dinstein, I.|author2=Thomas, C.|author3=Behrmann, M.|author4=Heeger, D.J.|year=2008|title=A mirror up to nature|journal=Current Biology|volume=18|issue=1|pages=R13–18|doi=10.1016/j.cub.2007.11.004|pmc=2517574|pmid=18177704|bibcode=2008CBio...18..R13D }}</ref> This has implications for birdsong learning– many birds rely on auditory feedback to acquire and maintain their songs. Mirror neurons may be mediating this comparison of what the bird hears, how it compares to a memorized song template, and what he produces.

In search of these auditory-motor neurons, Jonathan Prather and other researchers at Duke University recorded the activity of single neurons in the [[High vocal center|HVCs]] of [[swamp sparrow]]s.<ref name="Prather2008"/> They discovered that the neurons that project from the HVC to Area X (HVC<sub>X</sub> neurons) are highly responsive when the bird is hearing a playback of his own song. These neurons also fire in similar patterns when the bird is singing that same song. Swamp sparrows employ 3–5 different song types, and the neural activity differs depending on which song is heard or sung. The HVC<sub>X</sub> neurons only fire in response to the presentation (or singing) of one of the songs, the primary song type. They are also temporally selective, firing at a precise phase in the song syllable.

Prather, et al. found that during the short period of time before and after the bird sings, his HVC<sub>X</sub> neurons become insensitive to [[Sound|auditory]] input. In other words, the bird becomes "deaf" to his own song. This suggests that these neurons are producing a [[corollary discharge]], which would allow for direct comparison of motor output and auditory input.<ref>{{cite journal|author1=Tchernichovski, O.|author2=Wallman, J.|year=2008|title=Behavioral neuroscience: Neurons of imitation|journal=Nature|volume=451|issue=7176|pages=249–250|doi=10.1038/451249a|pmid=18202627|bibcode=2008Natur.451..249T|s2cid=205035217|doi-access=free}}</ref> This may be the mechanism underlying learning via auditory feedback. These findings are also in line with Leonardo's (2004) efference copy model of error correction in birdsong learning and production.

Overall, the HVC<sub>X</sub> auditory motor neurons in swamp sparrows are very similar to the visual motor mirror neurons discovered in [[primates]]. Like mirror neurons, the HVC<sub>X</sub> neurons:

* Are located in a [[premotor]] brain area
* Exhibit both sensory and motor properties
* Are action-specific – a response is only triggered by the "primary song type"

The function of the mirror neuron system is still unclear. Some scientists speculate that mirror neurons may play a role in understanding the actions of others, [[imitation]], [[theory of mind]] and [[language acquisition]], though there is currently insufficient [[neurophysiology|neurophysiological]] evidence in support of these theories.<ref name="Dinstein, I. 2008"/> Specifically regarding birds, it is possible that the mirror neuron system serves as a general mechanism underlying [[vocal learning]], but further research is needed. In addition to the implications for song learning, the mirror neuron system could also play a role in [[territorial behavior]]s such as song-type matching and countersinging.<ref>{{cite journal |author=Miller, G. |year=2008 |title=Mirror neurons may help songbirds stay in tune |journal=Science |volume=319 |issue=5861 |page=269 |doi=10.1126/science.319.5861.269a |pmid=18202262 |s2cid=34367648 }}</ref><ref>{{cite journal|url= |title=Auditory–vocal mirroring in songbirds|first=Richard |last=Mooney|journal=Philosophical Transactions of the Royal Society B: Biological Sciences|date=5 June 2014|volume=369|issue=1644|publisher=Philosophical Transactions of the Royal Society B: Biological Sciences Online|doi=10.1098/rstb.2013.0179|pmid=24778375|pmc=4006181}}</ref>