Whiskers: Difference between revisions

Amongst those species with motile macrovibrissae, some (rats, mice, flying squirrels, gerbils, chinchillas, hamsters, shrews, porcupines, opossums) move them back and forth periodically in a movement known as ''whisking'',<ref>{{cite web|url=https://www.youtube.com/watch?v=aMHuMhEzGWI |url-status=dead |archive-url= https://web.archive.org/web/20130703223500/http://www.youtube.com/watch?v=aMHuMhEzGWI |archive-date= Jul 3, 2013 |title=CIA-Rat |author1=RoyalSociety |date=Oct 2, 2011 |publisher=Youtube |access-date=2013-06-24}}</ref> while other species (cats, dogs, raccoons, pandas) do not appear to.<ref name=scholarpedia /> The distribution of mechanoreceptor types in the whisker follicle differs between rats and cats, which may correspond to this difference in the way they are used.<ref name=ebara /> Whisking movements are amongst the fastest produced by mammals.<ref name=jin>{{cite journal | title=Fiber Types of the Intrinsic Whisker Muscle and Whisking Behavior | journal=The Journal of Neuroscience|date= March 31, 2004|volume= 24|issue=13|pages=3386–3393 | doi=10.1523/JNEUROSCI.5151-03.2004 | last1=Jin | first1=T.-E. | pmid=15056718 | pmc=6730039| last2=Witzemann | first2=V. | last3=Brecht | first3=M. }}</ref> In all whisking animals in which it has so far been measured, these whisking movements are rapidly controlled in response to behavioural and environmental conditions.<ref name=scholarpedia>{{cite journal |title=Vibrissal behaviour and function|journal=Scholarpedia | volume= 6|page=6642 | doi=10.4249/scholarpedia.6642 | year=2011 | last1=Grant | first1=Robyn | last2=Mitchinson | first2=Ben | last3=Prescott | first3=Tony | issue=10 |doi-broken-date=2024-06-12 |bibcode=2011SchpJ...6.6642P| doi-access=free }}</ref> The whisking movements occur in bouts of variable duration, and at rates between 3 and 25 whisks/second. Movements of the whiskers are closely coordinated with those of the head and body.<ref name="scholarpedia"/>

Sensory function aside, movements of the vibrissae may also indicate something of the state of mind of the animal,<ref name="vets" /> and the whiskers play a role in social behaviour of rats.<ref name="Wolfe Mende Brecht 2011 pp. 900–9102">{{cite journal |last1=Wolfe |first1=Jason |last2=Mende |first2=Carolin |last3=Brecht |first3=Michael |date=2011 |title=Social facial touch in rats. |journal=Behavioral Neuroscience |volume=125 |issue=6 |pages=900–910 |doi=10.1037/a0026165 |pmid=22122151 |issn=1939-0084}}</ref>

The sensory function of vibrissae is an active research area—experiments to establish the capabilities of whiskers use a variety of techniques, including temporary deprivation either of the whisker sense or of other senses. Animals can be deprived of their whisker sense for a period of weeks by whisker trimming (they soon grow back), or for the duration of an experimental trial by restraining the whiskers with a flexible cover like a mask (the latter technique is used, in particular, in studies of marine mammals<ref name=dehnhardt />). Such experiments have shown that whiskers are required for, or contribute to: object localization,<ref name=Ahissar>{{cite journal | title=Vibrissal location decoding | first1=E. | last1=Ahissar | first2=P. M. | last2= Knutsen | journal=Scholarpedia| volume=6|issue=10|pages=6639|doi=10.4249/scholarpedia.6639 | year=2011 | doi-broken-date=2024-06-12 | bibcode=2011SchpJ...6.6639A | doi-access=free }}</ref><ref name=Diamond>{{cite journal | title='Where' and 'what' in the whisker sensorimotor system| first1=M. | last1=Diamond | first2=P | last2=von Heimendahl |first3=P. |last3=Knutsen |first4=D. |last4=Kleinfeld |first5=A. |last5=Ahissar |journal=Nature Reviews Neuroscience |volume=9 |issue=8 |pages=601–612 |doi=10.1038/nrn2411 |pmid=18641667 |year=2008 |s2cid=6450408 }}</ref> orienting of the snout, detection of movement, texture discrimination, shape discrimination, exploration, [[thigmotaxis]], locomotion, maintenance of equilibrium, maze learning, swimming, locating food pellets, locating food animals, and fighting, as well as nipple attachment and huddling in rat pups.<ref name=scholarpedia/>

A large part of the [[brain]] of whisker-specialist mammals is involved in the processing of nerve impulses from vibrissae, a fact that presumably corresponds to the important position the sense occupies for the animal. Information from the vibrissae arrives in the brain via the [[trigeminal nerve]] and is delivered first into the trigeminal sensory complex of [[brainstem]]. From there, the most studied pathways are those leading up through parts of [[thalamus]] and into [[barrel cortex]],<ref>{{cite journal | title=Vibrissal afferents from trigeminus to cortices | journal=Scholarpedia | volume= 4|pages=7454 | doi=10.4249/scholarpedia.7454 | year=2009 | last1=Deschenes | first1=Martin |last2=Urbain |first2=Nadia | issue=5 | doi-broken-date=2024-06-12 | bibcode=2009SchpJ...4.7454D | doi-access=free }}</ref> though other major pathways through the [[superior colliculus]] in [[midbrain]] (a major visual structure in visual animals) and the [[cerebellum]], to name but a couple, are increasingly coming under scrutiny.<ref name=loops>{{cite journal | title=Anatomical loops and their electrical dynamics in relation to whisking by rat | journal=Somatosensory & Motor Research | volume= 16| issue = 2 |pages=69–88 | doi=10.1080/08990229970528 | pmid=10449057 | year=1999 | last1=Kleinfeld | first1=Rune w. Berg | citeseerx=10.1.1.469.3914 }}</ref> Neuroscientists, and other researchers, studying sensory systems favour the whisker system for a number of reasons (see [[Barrel cortex]]), not least the simple fact that laboratory rats and mice are whisker, rather than visual, specialists.