View source for Yakovlevian torque

{{Short description|Asymmetry of the brain hemispheres}}
[[File:YakovlevianTorque.png|thumb|The Yakovlevian torque in the cerebrum (exaggerated). Redrawn from Toga & Thompson (2003).<ref name="Toga"/>]]
'''Yakovlevian torque''' (also known as '''occipital bending''' ('''OB''')<ref name="Maller">{{Cite journal|date=2015-01-30|title=Occipital bending (Yakovlevian torque) in bipolar depression|journal=Psychiatry Research: Neuroimaging|language=en|volume=231|issue=1|pages=8–14|doi=10.1016/j.pscychresns.2014.11.008|pmid=25480522|issn=0925-4927|last1=Maller|first1=Jerome J.|last2=Anderson|first2=Rodney|last3=Thomson|first3=Richard H.|last4=Rosenfeld |first4=Jeffrey V. |author-link4=Jeffrey Rosenfeld |last5=Daskalakis|first5=Zafiris J.|last6=Fitzgerald|first6=Paul B.|s2cid=37224862}}</ref> or '''counterclockwise brain torque'''<ref name="Mock">{{cite journal |last1=Mock |first1=Jeffrey |last2=Zadina |first2=Janet |last3=Corey |first3=David |last4=Cohen |first4=Jeremy |last5=Lemen |first5=Lisa |last6=Foundas |first6=Anne |title=Atypical Brain Torque in Boys With Developmental Stuttering |journal=Developmental Neuropsychology |date=2012 |volume=37 |issue=5 |pages=434–452 |doi=10.1080/87565641.2012.661816 |pmid=22799762 |pmc=5537737 }}</ref>) is the tendency of the right side of the [[human brain]] to be warped slightly forward relative to the left and the left side of the human brain to be warped slightly backward relative to the right. This is responsible for certain [[asymmetry|asymmetries]], such as how the [[lateral sulcus]] of the human [[brain]] is often longer and less curved on the left side of the brain relative to the right. Stated in another way, Yakovlevian torque can be defined by the existence of [[Frontal lobe|right-frontal]] and [[Occipital lobe|left-occipital]] [[Paleoneurobiology#Asymmetry|petalias]], which are protrusions of the surface of one hemisphere relative to the other. It is named for [[Paul Ivan Yakovlev]] (1894&ndash;1983), a Russian-American [[neuroanatomy|neuroanatomist]] from [[Harvard Medical School]].<ref name="Toga">{{cite journal|first1=A. W.|last1=Toga|last2=Thompson|first2=P. M.|year=2003|title=Mapping brain asymmetry|journal=Nature Reviews Neuroscience|volume=4|issue=1|pages=37–48|doi=10.1038/nrn1009|pmid=12511860|
s2cid=15867592}}</ref><ref>{{cite book|last=Carter|first=Rita|title=The Human Brain Book|page=57|isbn=978-0-7566-5441-2|publisher=Dorling Kindersley |year=2009}}</ref>
==Effects==
===Handedness===
A 2012 literature review showed that [[Morphometrics|morphometry]] studies had consistently found that [[handedness|handedness-related]] effects corresponded to the extent of the Yakovlevian torque;<ref name="Renteria">{{cite journal |last1=Renteria |first1=Miguel E. |title=Cerebral Asymmetry: A Quantitative, Multifactorial, and Plastic Brain Phenotype |journal=Twin Research and Human Genetics |date=March 26, 2012 |volume=15 |issue=3 |pages=401–413 |doi=10.1017/thg.2012.13 |pmid=22856374 |s2cid=6685337 |url=https://www.cambridge.org/core/services/aop-cambridge-core/content/view/6B69E8EF4FC75A0B851C9A606A5BE1E0/S1832427412000138a.pdf/cerebral_asymmetry_a_quantitative_multifactorial_and_plastic_brain_phenotype.pdf |access-date=November 8, 2019}}</ref> increased torque, as measured by increased size of the right-frontal petalia and the left-occipital petalia, tends to be more common in right-handed individuals.<ref name="Phillips">{{cite journal |last1=Phillips |first1=Kimberly A. |last2=Sherwood |first2=Chet C. |title=Cerebral Petalias and Their Relationship to Handedness in Capuchin Monkeys (Cebus apella) |journal=Neuropsychologia |date=June 11, 2007 |volume=45 |issue=10 |pages=2398–2401 |pmc=1959338 |pmid=17418285 |doi=10.1016/j.neuropsychologia.2007.02.021 }}</ref> Individuals with mixed-handedness or left-handedness show reduced levels of Yakovlevian torque.<ref>{{cite journal |last1=Guadalupe |first1=Tulio |last2=Willems |first2=Roel |last3=Zwiers |first3=Marcel |last4=Vasquez |first4=Alejandro |last5=Hoogman |first5=Martine |last6=Hagoort |first6=Peter |last7=Fernandez |first7=Guillen |last8=Jan |first8=Buitelaar |last9=Franke |first9=Barbara |last10=Fisher |first10=Simon |last11=Francks |first11=Clyde |title=Differences in cerebral cortical anatomy of left- and right-handers |journal=Frontiers in Psychology |date=March 28, 2014 |volume=5 |issue=26 |pages=261 |pmc=3975119 |pmid=24734025 |doi=10.3389/fpsyg.2014.00261 |doi-access=free }}</ref>
===Developmental stuttering===
Reduced right-frontal and left-occipital petalias and reversed petalia asymmetries (that is, left-frontal and right occipital petalias) have been associated with developmental [[stuttering]] in both adults and pre-adolescent boys.<ref name="Mock"/> This may be tied to the [[lateral sulcus]] housing [[Broca's area]],<ref name="Renteria" /> which plays a significant role in [[Speech|production of language]].
===Bipolar disorder===
Increased size of the left-occipital petalia, resulting from an abnormally high degree of Yakovlevian torque has been associated with [[bipolar disorder]].<ref name="Maller" /> Maller et al. 2015 found that increased asymmetry of the occipital lobe, or occipital bending, was four times more prevalent in subjects with bipolar disorder than in healthy controls.<ref name="Maller" /> This applied both to patients with [[Bipolar I disorder|bipolar disorder type I]] and [[Bipolar II disorder|type II]].
==Development and evolution==
There is some evidence suggesting that the Yakovlevian torque is related to the [[facial asymmetry#Aurofacial asymmetry|aurofacial asymmetry]] and the [[contralateral brain|contralateral organization of the brain]] and is due to a not quite complete [[Axial Twist theory|twist of the anterior part of the head]].<ref name="lussanet2019">{{cite journal | last=de Lussanet | first=M.H.E. | doi=10.7717/peerj.7096 | journal=PeerJ | pages=e7096 | title=Opposite asymmetries of face and trunk and of kissing and hugging, as predicted by the axial twist hypothesis | volume=7 | year=2019|pmid=31211022|pmc=6557252 | doi-access=free}}</ref> According to the [[Axial Twist theory]], each side of the brain represents the opposite body side due to a developmental twist along the body axis.<ref name="Lussanet2012">{{cite journal | first1=M. H. E. | last1=de Lussanet | first2=J. W. M. | last2=Osse | year=2012 | title=An ancestral axial twist explains the contralateral forebain and the optic chiasm in vertebrates | journal=Animal Biology | volume=62 | issue=2 | pages=193–216 | doi=10.1163/157075611X617102 | arxiv=1003.1872 | s2cid=7399128}}</ref>
==Presence in primates==
Yakovlevian torque is found in modern humans and [[Hominidae#Fossil|fossil hominids]], appearing reliably as early as ''[[Homo erectus]]''.<ref name="Phillips" /> The patterning of petalias in extinct human ancestors is examined via [[endocast]]s, wherein a cast is made of the [[cranial vault]]: the asymmetries of human ancestors can be measured from these casts because petalias leave impressions inside the cranial vault.<ref name="Phillips" />
Some authors have reported that similar petalia patterns are found in a number of [[primates]] including [[Old World monkey]]s, [[New World monkey]]s and [[Hominidae|Great apes]],<ref>{{cite journal | pmid = 10683399 | doi=10.1016/s0028-3932(99)00090-1 | volume=38 | title=Asymmetries in cerebral width in nonhuman primate brains as revealed by magnetic resonance imaging (MRI) | year=2000 | journal=Neuropsychologia | pages=493–9  | last1 = Hopkins | first1 = WD | last2 = Marino | first2 = L| issue=4 | s2cid=40689952 }}</ref> but others report different protrusions;<ref>{{cite journal | last1 = Holloway | first1 = RL | last2 = De | year = 1982 | title = Some preliminary findings of the paleontology of cerebral dominance | journal = American Journal of Physical Anthropology | volume = 58 | issue = 1 | pages = 110 | doi = 10.1002/ajpa.1330580111 | pmid = 6812430 }}</ref><ref>{{cite journal |last1=LeMay |first1=M |title=Morphological cerebral asymmetries of modern man, fossil man, and nonhuman primate |journal=Annals of the New York Academy of Sciences |date=1976 |volume=280 |issue=1 |pages=349–366 |doi=10.1111/j.1749-6632.1976.tb25499.x |pmid=827951 |bibcode=1976NYASA.280..349L |s2cid=46070451 }}</ref> these differences seem to be tied to which techniques are used to measure the petalia, so it is not well-understood if all primates demonstrate Yakovlevian torque.<ref name="Phillips" />
==References==
<references/>
[[Category:Neuroanatomy|Yakovlevian torque]]
[[Category:Biophysics]]
[[Category:Brain]]
[[Category:Brain asymmetry]]