Content deleted Content added
→Language and speech: Clearer phrasing and edited mistake in lexical lateralization |
Marked citation from psychology stack exchange as unreliable |
||
| (6 intermediate revisions by 4 users not shown) | |||
Line 4:
[[File:Cerebral hemisphere - animation.gif|thumb|alt=Diagram of the human brain.|upright=1.2|The human brain is divided into two [[Cerebral hemisphere|hemispheres]]–left and right. Scientists continue to explore how some cognitive functions tend to be dominated by one side or the other; that is, how they are ''lateralized''.{{Legend|#F270F4|Right cerebral hemisphere}}{{Legend|#7086F4|Left cerebral hemisphere}}]]
The '''lateralization of brain function''' (or '''hemispheric dominance'''<ref>{{Cite web |date=2018-12-24 |title=Left brain vs. right brain: How does one dominate? |url=https://www.medicalnewstoday.com/articles/323892 |access-date=2023-01-10 |website=www.medicalnewstoday.com |language=en}}</ref><ref>{{Cite web |title=Hemispheric differences and hemispheric dominance (video) |url=https://www.khanacademy.org/test-prep/mcat/behavior/biological-basis-of-behavior-ner/v/hemispheric-differences-and-hemispheric-dominance |access-date=2023-01-10 |website=Khan Academy |language=en}}</ref>/ lateralization<ref>{{Cite web |title=Localisation of Function in the brain and Hemispheric Lateralisation: motor, somatosensory, visual, auditory and language centres; Broca's and Wernicke's areas, split brain research. Plasticity and Functional Recovery of the brain after trauma |url=https://www.psychologyhub.co.uk/student-resources/paper-2-biopsychology/brain-localisation-and-hemispheric-lateralisation/ |access-date=2023-01-10 |website=Psychology Hub |language=en-gb}}</ref><ref>{{Cite web |title=Lateralization of Brain Function - Simply Psychology |url=https://www.simplypsychology.org/brain-lateralization.html |access-date=2023-01-10 |website=www.simplypsychology.org}}</ref>) is the tendency for some neural functions or [[cognitive process]]es to be specialized to one side of the brain or the other. The [[median longitudinal fissure]] separates the [[human brain]] into two distinct [[cerebral hemisphere]]s
Lateralization of brain structures
The best example of an established lateralization is that of [[Broca's area|Broca's]] and [[Wernicke's area]]s, where both are often found exclusively on the left hemisphere. Function lateralization, such as [[semantics]], [[intonation (linguistics)|intonation]], [[accentuation]], and [[prosody (linguistics)|prosody]], has since been called into question and largely been found to have a neuronal basis in both hemispheres.<ref>{{cite journal | vauthors = Riès SK, Dronkers NF, Knight RT | title = Choosing words: left hemisphere, right hemisphere, or both? Perspective on the lateralization of word retrieval | journal = Annals of the New York Academy of Sciences | volume = 1369 | issue = 1 | pages = 111–131 | date = April 2016 | pmid = 26766393 | pmc = 4874870 | doi = 10.1111/nyas.12993 | bibcode = 2016NYASA1369..111R }}</ref> Another example is that each hemisphere in the brain tends to represent one side of the body. In the [[cerebellum]], this is the [[Ipsilateral|ipsilateral side]], but in the [[forebrain]] this is predominantly the [[Contralateral brain|contralateral side]].
Line 12:
== Lateralized functions==
===Language and speech===
[[Language]] functions are lateralized to the left hemisphere in 96% of right-handers and 60% of left-handers.<ref name="Taylor">{{cite book | vauthors = Taylor I, Taylor MM | year = 1990 | title = Psycholinguistics: Learning and using Language | publisher = Pearson | isbn = 978-0-13-733817-7}} p. 367</ref><ref name=":2">{{Cite book |
Meaning of words, called [[lexicon]], is processed bilaterally which has been tested through the [[word superiority effect]]. This finding is consistent with the distributed memory and knowledge systems required for lexical entries; however, each hemisphere's lexicon is considered unique since it may be organized and accessed differently.<ref name=":2" /> For example, the right hemisphere lacks letter recognition, and cannot judge lexical relationships such as superordinate words or [[antonyms]].<ref name=":2" />
Line 18:
The permitted organization of words, called [[grammar]], is lateralized in only one hemisphere, typically the left one. These functions include "understanding verbs, pluralizations, the possessive, and active-passive differences" and understanding changes in meaning due to word order.<ref name=":2" /> However, the right hemisphere is able to judge when a sentence is grammatically correct, which may indicate that patterns of speech are learned by rote rather than applied through understanding rules.<ref name=":2" />
[[Speech]] production and language comprehension are specialized in [[Broca's area|Broca's]] and [[Wernicke's area|Wernicke's]] areas respectively, which are located in the left hemisphere for 96% of right-handers and 70% of left-handers.<ref name=":2" /><ref name="Griggs2012">{{cite book |title=Psychology : a concise introduction |vauthors=Griggs RA |date=2012 |publisher=Worth Publishers |isbn=978-1429261555 |edition=3rd |___location=New York, NY}}</ref> However, there
In [[writing]], studies attempting to isolate the linguistic component of written language in terms of brain lateralization could not provide enough evidence of a difference in the relative activation of the brain hemispheres between left-handed and right-handed adults.<ref>{{cite journal | vauthors = Papadopoulou AK, Samsouris C, Vlachos F, Badcock N, Phylactou P, Papadatou-Pastou | title = Exploring cerebral laterality of writing and the relationship to handedness: a functional transcranial Doppler ultrasound investigation | journal = Laterality | volume = 29 | issue = 1 | pages = 117–150 | date = November 2023 | doi = 10.1080/1357650X.2023.2284407| pmid = 38112692 }}</ref>
Line 29:
==== Vision ====
[[File:Optic processing human brain.jpg|thumb|340x340px|Lateralization of the left and right visual hemifields due to decussation.]]
In [[visual perception|vision]], [[retinal ganglion cell]]s undergo partial decussation at the [[optic chiasm]], where [[axon]]s from the nasal retinas cross to the opposite hemisphere, while axons from the temporal retinas remain on the [[Ipsilateral|ipsilateral side]].<ref>{{Cite web|url=https://theodora.com/anatomy/the_optic_nerve.html|title = The Optic Nerve - Human Anatomy | work = Photius Coutsoukis }}</ref><ref name=":0">{{Cite book |
==== Hearing ====
Line 56:
=== Hemisphere damage ===
Damage to either the right or left hemisphere, and its resulting deficits provide insight into the function of the damaged area. There is truth to the idea that some brain functions reside more on one side of the brain than the other. We know this in part from what is lost when a stroke affects a particular part of the brain. Left hemisphere damage has many effects on language production and perception. Damage or lesions to the right hemisphere can result in a lack of [[emotional prosody]]<ref>{{Cite journal |last1=Patel |first1=Sona |last2=Oishi |first2=Kenichi |last3=Wright |first3=Amy |last4=Sutherland-Foggio |first4=Harry |last5=Saxena |first5=Sadhvi |last6=Sheppard |first6=Shannon M. |last7=Hillis |first7=Argye E. |date=2018 |title=Right Hemisphere Regions Critical for Expression of Emotion Through Prosody |journal=Frontiers in Neurology |volume=9 |page=224 |doi=10.3389/fneur.2018.00224 |pmc=5897518 |pmid=29681885 |doi-access=free }}</ref> or intonation when speaking.<ref name="Zickert 107884">{{cite journal |last1=Zickert |first1=Nele |last2=Geuze |first2=Reint H. |last3=Beking |first3=Tess |last4=Groothuis |first4=Ton G.G. |title=Testing the Darwinian function of lateralization. Does separation of workload between brain hemispheres increase cognitive performance? |journal=Neuropsychologia |date=August 2021 |volume=159 |
Right hemisphere damage also has grave effects on understanding discourse. People with damage to the right hemisphere have a reduced ability to generate inferences, comprehend and produce main concepts, and a reduced ability to manage alternative meanings. Furthermore, people with right hemisphere damage often exhibit discourse that is abrupt and perfunctory or verbose and excessive. They can also have pragmatic deficits in situations of turn taking, topic maintenance and shared knowledge. .<ref name="Zickert 107884"/> Although both sides of the hemisphere has different responsibilities and tasks, they both complete each other and create a bigger picture'''.'''<ref name="Zickert 107884"/>
Line 81:
=== Popular psychology ===
{{Further|Popular psychology}}[[File:Brain Lateralization.svg|thumb|right|Oversimplification of lateralization in pop psychology. This belief was widely held even in the scientific community for some years.]]
Some popularizations oversimplify the science about lateralization, by presenting the functional differences between hemispheres as being more absolute than is actually the case.<ref name="Westen 2006">{{cite book| vauthors = Westen D, Burton L, Kowalski K |title=Psychology : Australian and New Zealand edition|date=2006|publisher=John Wiley & Sons|___location=Milton, Qld.|isbn=9780470805527}}</ref>{{rp|107}}<ref>{{cite journal | vauthors = Toga AW, Thompson PM | title = Mapping brain asymmetry | journal = Nature Reviews Neuroscience | volume = 4 | issue = 1 | pages = 37–48 | date = January 2003 | pmid = 12511860 | doi = 10.1038/nrn1009 }}</ref> Interestingly, research has shown quite opposite function of brain lateralisation, i.e. right hemisphere creatively and chaotically links between concepts and left hemisphere tends to adhere to specific date and time, although generally adhering to the pattern of left-brain as linguistic interpretation and right brain as spatio-temporal.<ref>{{Cite web|url=https://psychology.stackexchange.com/questions/16096/brain-right-hemisphere-is-random-and-left-hemisphere-is-linear-really|title = Cognitive psychology - Brain Right hemisphere is random and left hemisphere is linear? Really? | publisher = Stack Exchange, Inc }}</ref>{{Unreliable source?|date=August 2025|certain=y|reason=Psychology stack exchange is a forum, not a trustworthy source of information.}}<ref name="pmid10869045">{{cite journal |last1=Gazzaniga |first1=M. S. |title=Cerebral specialization and interhemispheric communication: Does the corpus callosum enable the human condition? |journal=Brain |date=July 2000 |volume=123 |issue=7 |pages=1293–1326 |doi=10.1093/brain/123.7.1293 |pmid=10869045 |doi-access=free }}</ref>
===Sex differences===
| |||