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Lateralization of brain function

The lateralization of brain function (or hemispheric dominance[1][2]/ latralisation[3][4]) is the tendency for some neural functions or cognitive processes to be specialized to one side of the brain or the other. The median longitudinal fissure separates the human brain into two distinct cerebral hemispheres, connected by the corpus callosum. Although the macrostructure of the two hemispheres appears to be almost identical, different composition of neuronal networks allows for specialized function that is different in each hemisphere.

The human brain is divided into two 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.
  Right cerebral hemisphere
  Left cerebral hemisphere

Lateralization of brain structures is based on general trends expressed in healthy patients; however, there are numerous counterexamples to each generalization. Each human's brain develops differently, leading to unique lateralization in individuals. This is different from specialization, as lateralization refers only to the function of one structure divided between two hemispheres. Specialization is much easier to observe as a trend, since it has a stronger anthropological history.[5]

The best example of an established lateralization is that of Broca's and Wernicke's areas, where both are often found exclusively on the left hemisphere. Function lateralization, such as semantics, intonation, accentuation, and prosody, has since been called into question and largely been found to have a neuronal basis in both hemispheres.[6] Another example is that each hemisphere in the brain tends to represent one side of the body. In the cerebellum, this is the same body side, but in the forebrain this is predominantly the contralateral side.

Lateralized functions edit

Language edit

Language functions such as grammar, vocabulary and literal meaning are typically lateralized to the left hemisphere, especially in right-handed individuals.[7] While language production is left-lateralized in up to 90% of right-handers, it is more bilateral, or even right-lateralized, in approximately 50% of left-handers.[8]

 
This photo shows the left and right specialties of the brain.

Broca's area and Wernicke's area, associated with the production of speech and comprehension of speech, respectively, are located in the left cerebral hemisphere for about 95% of right-handers but about 70% of left-handers.[9]: 69  Social interactions, demonstrating fierce emotions, and mathematical information are all provided by the right hemisphere.[10]

Sensory processing edit

The processing of basic sensory information is lateralized by being divided into left and right sides of the body or the space around the body.

In vision, about half the neurons of the optic nerve from each eye cross to project to the opposite hemisphere, and about half do not cross to project to the hemisphere on the same side.[11] This means that the left side of the visual field is processed largely by the visual cortex of the right hemisphere and vice versa for the right side of the visual field.

In hearing, about 90% of the neurons of the auditory nerve from one ear cross to project to the auditory cortex of the opposite hemisphere.

In the sense of touch, most of the neurons from the skin cross to project to the somatosensory cortex of the opposite hemisphere.

Because of this functional division of the left and right sides of the body and of the space that surrounds it, the processing of information in the sensory cortices is essentially identical. That is, the processing of visual and auditory stimuli, spatial manipulation, facial perception, and artistic ability are represented bilaterally.[8] Numerical estimation, comparison and online calculation depend on bilateral parietal regions[12][13] while exact calculation and fact retrieval are associated with left parietal regions, perhaps due to their ties to linguistic processing.[12][13]

Value systems edit

Rather than just being a series of places where different brain modules occur, there are running similarities in the kind of function seen in each side, for instance how right-side impairment of drawing ability making patients draw the parts of the subject matter with wholly incoherent relationships, or where the kind of left-side damage seen in language impairment not damaging the patient's ability to catch the significance of intonation in speech.[14] This has led British psychiatrist Iain McGilchrist to view the two hemispheres as having different value systems, where the left hemisphere tends to reduce complex matters such as ethics to rules and measures, and the right hemisphere is disposed to the holistic and metaphorical.[15]

Clinical significance edit

Depression is linked with a hyperactive right hemisphere, with evidence of selective involvement in "processing negative emotions, pessimistic thoughts and unconstructive thinking styles", as well as vigilance, arousal and self-reflection, and a relatively hypoactive left hemisphere, "specifically involved in processing pleasurable experiences" and "relatively more involved in decision-making processes".[16] Additionally, "left hemisphere lesions result in an omissive response bias or error pattern whereas right hemisphere lesions result in a commissive response bias or error pattern."[17] The delusional misidentification syndromes, reduplicative paramnesia and Capgras delusion are also often the result of right hemisphere lesions.[18]

 
Lateral view of the Brain

Hemisphere damage edit

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[19] or intonation when speaking.[20] The left hemisphere is often involved with dealing of detail oriented and perception while the right hemisphere is involved with mostly overview and an overall concept of things.[1]

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. .[20] Although both sides of the hemisphere has different responsibilities and tasks, they both complete each other and create a bigger picture. [2] Lateral brain damage can also affect visual perceptual spatial resolution. People with left hemisphere damage may have impaired perception of high resolution, or detailed, aspects of an image. People with right hemisphere damage may have impaired perception of low resolution, or big picture, aspects of an image.

Plasticity edit

If a specific region of the brain, or even an entire hemisphere, is injured or destroyed, its functions can sometimes be assumed by a neighboring region in the same hemisphere or the corresponding region in the other hemisphere, depending upon the area damaged and the patient's age.[21] When injury interferes with pathways from one area to another, alternative (indirect) connections may develop to communicate information with detached areas, despite the inefficiencies.

Broca's aphasia edit

Broca's aphasia is a specific type of expressive aphasia and is so named due to the aphasia that results from damage or lesions to the Broca's area of the brain, that exists most commonly in the left inferior frontal hemisphere. Thus, the aphasia that develops from the lack of functioning of the Broca's area is an expressive and non-fluent aphasia. It is called 'non-fluent' due to the issues that arise because Broca's area is critical for language pronunciation and production. The area controls some motor aspects of speech production and articulation of thoughts to words and as such lesions to the area result in specific non-fluent aphasia.[22]

Wernicke's aphasia edit

Wernicke's aphasia is the result of damage to the area of the brain that is commonly in the left hemisphere above the Sylvian fissure. Damage to this area causes primarily a deficit in language comprehension. While the ability to speak fluently with normal melodic intonation is spared, the language produced by a person with Wernicke's aphasia is riddled with semantic errors and may sound nonsensical to the listener. Wernicke's aphasia is characterized by phonemic paraphasias, neologism or jargon. Another characteristic of a person with Wernicke's aphasia is that they are unconcerned by the mistakes that they are making.

Society and culture edit

Possible misapplication edit

 
Oversimplification of hemisphericity

The concept of "right-brained" or "left-brained" individuals is considered a widespread myth which oversimplifies the true nature of the brain's cerebral hemispheres (for a recent counter position, though, see below). Proof leading to the "mythbuster" of the left-/right-brained concept is increasing as more and more studies are brought to light. Harvard Health Publishing includes a study from the University of Utah in 2013, that exhibited brain scans revealing similarity on both sides of the brain, personality and environmental factors aside.[1] Although certain functions show a degree of lateralization in the brain—with language predominantly processed in the left hemisphere, and spatial and nonverbal reasoning in the right—these functions are not exclusively tied to one hemisphere.[23]

Terence Hines states that the research on brain lateralization is valid as a research program, though commercial promoters have applied it to promote subjects and products far outside the implications of the research.[24] For example, the implications of the research have no bearing on psychological interventions such as eye movement desensitization and reprocessing (EMDR) and neurolinguistic programming,[25][26] brain-training equipment, or management training.[27]

Counter position

The debate as to being “right-brained” or “left-brained” was reopened anew in 2023.[28] This re-opening is based on neuroscientific research which has refined the underlying primary functions of the two sides of the neocortex. In particular, Elkhonon Goldberg's “novelty-routinization” theory posits that the neocortex's right and left hemispheres primarily process cognitively novel and cognitively routine tasks, respectively.[29]

(Thus, this theory fits with [novel] aspects of visual-spatial processing predominantly occurring in the right hemisphere, as they tend to be relatively novel; similarly, [familiar] aspects of language tend to being predominantly processed in the left hemisphere, as they indeed tend to be cognitively routine to us. New/novel aspects of language, though, will fittingly be processed in the right-brain, just as familiar aspects of visual-spatial processing will be processed in the left-brain. [This explains why these functions are not exclusively tied to one hemisphere.])

As such, right-brained people favor the cognitively novel tasks/information whereas left-brained people favor the cognitively routine tasks/information. Or, in other words, right-brained people tend to prefer new and novel experiences whereas left-brained people favor familiar experiences. (Thus, this theory is the deeper understanding of many of pop psychology's “oversimplifications” of lateralization. For example, it explains why the right hemisphere has been considered creative, as creativity tends to involve new and novel information/tasks, whereas the left hemisphere has been considered analytical, as analysis tends to be the re-processing of already familiar information.)

This is not to say, though, that the tendencies of the left hemisphere cannot be performed well by a right-brained person and vice versa. For instance, right-brained people can exhibit strong analytical skills and attention to detail (generally cognitively routine, left-brained tasks), sometimes even surpassing their left-brained counterparts, but their overall tendency is more so to instead be synthesizing and to attend to the big picture (generally cognitively new, right-hemisphere-tending tasks). (Such nuances are one reason this thinking has been labeled a myth.)

Based on Goldberg's theory, the following table provides newly identified preferences of left- and right-brained people.[28]

Preference Category Left-brained People Right-brained People
Experience Type Familiar and Existing New and Novel
Learning/Action Pattern Learn, then Do Do, then Learn
Improve or Create? Improve Create
Review or Discover? Review Discover
Depth or Breadth? Depth Breadth
Analyze or Action? Analyze Action

It is vital, though, to remember that these are only tendencies. At times we may contradict our tendency to be left- or right-brained, but often we can come to identify the underlying reason.[28] Furthermore, although less likely, some of us may be more bilobal, but in general it seems most of demonstrate tendencies related to one side or the other—in other words, most of us prefer either new and novel experiences most of the time or we prefer familiar and known experiences most of the time.

This is not to say, though, that we do not use the whole brain. Life and personal growth require the use and development of both the right and left hemispheres, as it requires the processing of novel, unfamiliar situations as well as familiar, routine ones. Without this ability, we would struggle to survive and thrive. Interestingly, as we get older, we tend to become more set in our ways, which fits with many older adults and seniors having struggles to stay up on technology and other new and novel experiences.

Popular psychology edit

 
The 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.[30]: 107 [31] Interestingly, research has shown quite opposite function of brain lateralisation, i.e. left hemisphere creatively and chaotically links between concepts and right 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.[32][33][34]

Sex differences edit

In the 19th century and to a lesser extent the 20th, it was thought that each side of the brain was associated with a specific gender: the left corresponding with masculinity and the right with femininity and each half could function independently.[35] The right side of the brain was seen as the inferior and thought to be prominent in women, savages, children, criminals, and the insane. A prime example of this in fictional literature can be seen in Robert Louis Stevenson's Strange Case of Dr. Jekyll and Mr. Hyde.[36]

History edit

Broca edit

One of the first indications of brain function lateralization resulted from the research of French physician Pierre Paul Broca, in 1861. His research involved the male patient nicknamed "Tan", who had a speech deficit (aphasia); "tan" was one of the few words he could articulate, hence his nickname. In Tan's autopsy, Broca determined he had a syphilitic lesion in the left cerebral hemisphere. This left frontal lobe brain area (Broca's area) is an important speech production region. The motor aspects of speech production deficits caused by damage to Broca's area are known as expressive aphasia. In clinical assessment of this type of aphasia, patients have difficulty producing speech.[37]

Wernicke edit

German physician Karl Wernicke continued in the vein of Broca's research by studying language deficits unlike expressive aphasia. Wernicke noted that not every deficit was in speech production; some were linguistic. He found that damage to the left posterior, superior temporal gyrus (Wernicke's area) caused language comprehension deficits rather than speech production deficits, a syndrome known as receptive aphasia.

Imaging edit

These seminal works on hemispheric specialization were done on patients or postmortem brains, raising questions about the potential impact of pathology on the research findings. New methods permit the in vivo comparison of the hemispheres in healthy subjects. Particularly, magnetic resonance imaging (MRI) and positron emission tomography (PET) are important because of their high spatial resolution and ability to image subcortical brain structures.

Movement and sensation edit

In the 1940s, neurosurgeon Wilder Penfield and his neurologist colleague Herbert Jasper developed a technique of brain mapping to help reduce side effects caused by surgery to treat epilepsy. They stimulated motor and somatosensory cortices of the brain with small electrical currents to activate discrete brain regions. They found that stimulation of one hemisphere's motor cortex produces muscle contraction on the opposite side of the body. Furthermore, the functional map of the motor and sensory cortices is fairly consistent from person to person; Penfield and Jasper's famous pictures of the motor and sensory homunculi were the result.

Split-brain patients edit

Research by Michael Gazzaniga and Roger Wolcott Sperry in the 1960s on split-brain patients led to an even greater understanding of functional laterality. Split-brain patients are patients who have undergone corpus callosotomy (usually as a treatment for severe epilepsy), a severing of a large part of the corpus callosum. The corpus callosum connects the two hemispheres of the brain and allows them to communicate. When these connections are cut, the two halves of the brain have a reduced capacity to communicate with each other. This led to many interesting behavioral phenomena that allowed Gazzaniga and Sperry to study the contributions of each hemisphere to various cognitive and perceptual processes. One of their main findings was that the right hemisphere was capable of rudimentary language processing, but often has no lexical or grammatical abilities.[38] Eran Zaidel also studied such patients and found some evidence for the right hemisphere having at least some syntactic ability.[citation needed]

Language is primarily localized in the left hemisphere. While the left hemisphere has proven to be more optimized for language, the right hemisphere has the capacity with emotions, such as sarcasm, that can express prosody in sentences when speaking. According to Sheppard and Hillis, "The right hemisphere is critical for perceiving sarcasm (Davis et al., 2016), integrating context required for understanding metaphor, inference, and humour, as well as recognizing and expressing affective or emotional prosody—changes in pitch, rhythm, rate, and loudness that convey emotions".[39] One of the experiments carried out by Gazzaniga involved a split-brain male patient sitting in front of a computer screen while having words and images presented on either side of the screen, and the visual stimuli would go to either the right or left visual field, and thus the left or right brain, respectively. It was observed that if the patient was presented with an image to his left visual field (right brain), he would report not seeing anything. If he was able to feel around for certain objects, he could accurately pick out the correct object, despite not having the ability to verbalize what he saw.

Additional images edit

See also edit

[40]

References edit

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External links edit

  • Left Brain, Right Brain? Wrong

Bibliography edit

Further resources edit

lateralization, brain, function, this, article, about, specialization, function, between, left, right, hemispheres, brain, specialization, brain, function, generally, functional, specialization, brain, lateralization, brain, function, hemispheric, dominance, l. This article is about specialization of function between the left and right hemispheres of the brain For specialization of brain function generally see Functional specialization brain The lateralization of brain function or hemispheric dominance 1 2 latralisation 3 4 is the tendency for some neural functions or cognitive processes to be specialized to one side of the brain or the other The median longitudinal fissure separates the human brain into two distinct cerebral hemispheres connected by the corpus callosum Although the macrostructure of the two hemispheres appears to be almost identical different composition of neuronal networks allows for specialized function that is different in each hemisphere The human brain is divided into two 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 Right cerebral hemisphere Left cerebral hemisphere Lateralization of brain structures is based on general trends expressed in healthy patients however there are numerous counterexamples to each generalization Each human s brain develops differently leading to unique lateralization in individuals This is different from specialization as lateralization refers only to the function of one structure divided between two hemispheres Specialization is much easier to observe as a trend since it has a stronger anthropological history 5 The best example of an established lateralization is that of Broca s and Wernicke s areas where both are often found exclusively on the left hemisphere Function lateralization such as semantics intonation accentuation and prosody has since been called into question and largely been found to have a neuronal basis in both hemispheres 6 Another example is that each hemisphere in the brain tends to represent one side of the body In the cerebellum this is the same body side but in the forebrain this is predominantly the contralateral side Contents 1 Lateralized functions 1 1 Language 1 2 Sensory processing 1 3 Value systems 2 Clinical significance 2 1 Hemisphere damage 2 2 Plasticity 2 3 Broca s aphasia 2 4 Wernicke s aphasia 3 Society and culture 3 1 Possible misapplication 3 2 Popular psychology 3 3 Sex differences 4 History 4 1 Broca 4 2 Wernicke 4 3 Imaging 4 4 Movement and sensation 4 5 Split brain patients 5 Additional images 6 See also 7 References 8 External links 9 Bibliography 10 Further resourcesLateralized functions editLanguage edit Language functions such as grammar vocabulary and literal meaning are typically lateralized to the left hemisphere especially in right handed individuals 7 While language production is left lateralized in up to 90 of right handers it is more bilateral or even right lateralized in approximately 50 of left handers 8 nbsp This photo shows the left and right specialties of the brain Broca s area and Wernicke s area associated with the production of speech and comprehension of speech respectively are located in the left cerebral hemisphere for about 95 of right handers but about 70 of left handers 9 69 Social interactions demonstrating fierce emotions and mathematical information are all provided by the right hemisphere 10 Sensory processing edit The processing of basic sensory information is lateralized by being divided into left and right sides of the body or the space around the body In vision about half the neurons of the optic nerve from each eye cross to project to the opposite hemisphere and about half do not cross to project to the hemisphere on the same side 11 This means that the left side of the visual field is processed largely by the visual cortex of the right hemisphere and vice versa for the right side of the visual field In hearing about 90 of the neurons of the auditory nerve from one ear cross to project to the auditory cortex of the opposite hemisphere In the sense of touch most of the neurons from the skin cross to project to the somatosensory cortex of the opposite hemisphere Because of this functional division of the left and right sides of the body and of the space that surrounds it the processing of information in the sensory cortices is essentially identical That is the processing of visual and auditory stimuli spatial manipulation facial perception and artistic ability are represented bilaterally 8 Numerical estimation comparison and online calculation depend on bilateral parietal regions 12 13 while exact calculation and fact retrieval are associated with left parietal regions perhaps due to their ties to linguistic processing 12 13 Value systems edit Rather than just being a series of places where different brain modules occur there are running similarities in the kind of function seen in each side for instance how right side impairment of drawing ability making patients draw the parts of the subject matter with wholly incoherent relationships or where the kind of left side damage seen in language impairment not damaging the patient s ability to catch the significance of intonation in speech 14 This has led British psychiatrist Iain McGilchrist to view the two hemispheres as having different value systems where the left hemisphere tends to reduce complex matters such as ethics to rules and measures and the right hemisphere is disposed to the holistic and metaphorical 15 Clinical significance editDepression is linked with a hyperactive right hemisphere with evidence of selective involvement in processing negative emotions pessimistic thoughts and unconstructive thinking styles as well as vigilance arousal and self reflection and a relatively hypoactive left hemisphere specifically involved in processing pleasurable experiences and relatively more involved in decision making processes 16 Additionally left hemisphere lesions result in an omissive response bias or error pattern whereas right hemisphere lesions result in a commissive response bias or error pattern 17 The delusional misidentification syndromes reduplicative paramnesia and Capgras delusion are also often the result of right hemisphere lesions 18 nbsp Lateral view of the Brain Hemisphere damage edit 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 19 or intonation when speaking 20 The left hemisphere is often involved with dealing of detail oriented and perception while the right hemisphere is involved with mostly overview and an overall concept of things 1 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 20 Although both sides of the hemisphere has different responsibilities and tasks they both complete each other and create a bigger picture 2 Lateral brain damage can also affect visual perceptual spatial resolution People with left hemisphere damage may have impaired perception of high resolution or detailed aspects of an image People with right hemisphere damage may have impaired perception of low resolution or big picture aspects of an image Plasticity edit If a specific region of the brain or even an entire hemisphere is injured or destroyed its functions can sometimes be assumed by a neighboring region in the same hemisphere or the corresponding region in the other hemisphere depending upon the area damaged and the patient s age 21 When injury interferes with pathways from one area to another alternative indirect connections may develop to communicate information with detached areas despite the inefficiencies Broca s aphasia edit Broca s aphasia is a specific type of expressive aphasia and is so named due to the aphasia that results from damage or lesions to the Broca s area of the brain that exists most commonly in the left inferior frontal hemisphere Thus the aphasia that develops from the lack of functioning of the Broca s area is an expressive and non fluent aphasia It is called non fluent due to the issues that arise because Broca s area is critical for language pronunciation and production The area controls some motor aspects of speech production and articulation of thoughts to words and as such lesions to the area result in specific non fluent aphasia 22 Wernicke s aphasia edit Wernicke s aphasia is the result of damage to the area of the brain that is commonly in the left hemisphere above the Sylvian fissure Damage to this area causes primarily a deficit in language comprehension While the ability to speak fluently with normal melodic intonation is spared the language produced by a person with Wernicke s aphasia is riddled with semantic errors and may sound nonsensical to the listener Wernicke s aphasia is characterized by phonemic paraphasias neologism or jargon Another characteristic of a person with Wernicke s aphasia is that they are unconcerned by the mistakes that they are making Society and culture editPossible misapplication edit nbsp Oversimplification of hemisphericity The concept of right brained or left brained individuals is considered a widespread myth which oversimplifies the true nature of the brain s cerebral hemispheres for a recent counter position though see below Proof leading to the mythbuster of the left right brained concept is increasing as more and more studies are brought to light Harvard Health Publishing includes a study from the University of Utah in 2013 that exhibited brain scans revealing similarity on both sides of the brain personality and environmental factors aside 1 Although certain functions show a degree of lateralization in the brain with language predominantly processed in the left hemisphere and spatial and nonverbal reasoning in the right these functions are not exclusively tied to one hemisphere 23 Terence Hines states that the research on brain lateralization is valid as a research program though commercial promoters have applied it to promote subjects and products far outside the implications of the research 24 For example the implications of the research have no bearing on psychological interventions such as eye movement desensitization and reprocessing EMDR and neurolinguistic programming 25 26 brain training equipment or management training 27 Counter position This section relies largely or entirely on a single source Relevant discussion may be found on the talk page Please help improve this article by introducing citations to additional sources Find sources Lateralization of brain function news newspapers books scholar JSTOR April 2024 The debate as to being right brained or left brained was reopened anew in 2023 28 This re opening is based on neuroscientific research which has refined the underlying primary functions of the two sides of the neocortex In particular Elkhonon Goldberg s novelty routinization theory posits that the neocortex s right and left hemispheres primarily process cognitively novel and cognitively routine tasks respectively 29 Thus this theory fits with novel aspects of visual spatial processing predominantly occurring in the right hemisphere as they tend to be relatively novel similarly familiar aspects of language tend to being predominantly processed in the left hemisphere as they indeed tend to be cognitively routine to us New novel aspects of language though will fittingly be processed in the right brain just as familiar aspects of visual spatial processing will be processed in the left brain This explains why these functions are not exclusively tied to one hemisphere As such right brained people favor the cognitively novel tasks information whereas left brained people favor the cognitively routine tasks information Or in other words right brained people tend to prefer new and novel experiences whereas left brained people favor familiar experiences Thus this theory is the deeper understanding of many of pop psychology s oversimplifications of lateralization For example it explains why the right hemisphere has been considered creative as creativity tends to involve new and novel information tasks whereas the left hemisphere has been considered analytical as analysis tends to be the re processing of already familiar information This is not to say though that the tendencies of the left hemisphere cannot be performed well by a right brained person and vice versa For instance right brained people can exhibit strong analytical skills and attention to detail generally cognitively routine left brained tasks sometimes even surpassing their left brained counterparts but their overall tendency is more so to instead be synthesizing and to attend to the big picture generally cognitively new right hemisphere tending tasks Such nuances are one reason this thinking has been labeled a myth Based on Goldberg s theory the following table provides newly identified preferences of left and right brained people 28 Preference Category Left brained People Right brained People Experience Type Familiar and Existing New and Novel Learning Action Pattern Learn then Do Do then Learn Improve or Create Improve Create Review or Discover Review Discover Depth or Breadth Depth Breadth Analyze or Action Analyze Action It is vital though to remember that these are only tendencies At times we may contradict our tendency to be left or right brained but often we can come to identify the underlying reason 28 Furthermore although less likely some of us may be more bilobal but in general it seems most of demonstrate tendencies related to one side or the other in other words most of us prefer either new and novel experiences most of the time or we prefer familiar and known experiences most of the time This is not to say though that we do not use the whole brain Life and personal growth require the use and development of both the right and left hemispheres as it requires the processing of novel unfamiliar situations as well as familiar routine ones Without this ability we would struggle to survive and thrive Interestingly as we get older we tend to become more set in our ways which fits with many older adults and seniors having struggles to stay up on technology and other new and novel experiences Popular psychology edit Further information Popular psychology nbsp The 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 30 107 31 Interestingly research has shown quite opposite function of brain lateralisation i e left hemisphere creatively and chaotically links between concepts and right 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 32 33 34 Sex differences edit See also Neuroscience of sex differences In the 19th century and to a lesser extent the 20th it was thought that each side of the brain was associated with a specific gender the left corresponding with masculinity and the right with femininity and each half could function independently 35 The right side of the brain was seen as the inferior and thought to be prominent in women savages children criminals and the insane A prime example of this in fictional literature can be seen in Robert Louis Stevenson s Strange Case of Dr Jekyll and Mr Hyde 36 History editThis section does not cite any sources Please help improve this section by adding citations to reliable sources Unsourced material may be challenged and removed October 2017 Learn how and when to remove this message Broca edit One of the first indications of brain function lateralization resulted from the research of French physician Pierre Paul Broca in 1861 His research involved the male patient nicknamed Tan who had a speech deficit aphasia tan was one of the few words he could articulate hence his nickname In Tan s autopsy Broca determined he had a syphilitic lesion in the left cerebral hemisphere This left frontal lobe brain area Broca s area is an important speech production region The motor aspects of speech production deficits caused by damage to Broca s area are known as expressive aphasia In clinical assessment of this type of aphasia patients have difficulty producing speech 37 Wernicke edit German physician Karl Wernicke continued in the vein of Broca s research by studying language deficits unlike expressive aphasia Wernicke noted that not every deficit was in speech production some were linguistic He found that damage to the left posterior superior temporal gyrus Wernicke s area caused language comprehension deficits rather than speech production deficits a syndrome known as receptive aphasia Imaging edit These seminal works on hemispheric specialization were done on patients or postmortem brains raising questions about the potential impact of pathology on the research findings New methods permit the in vivo comparison of the hemispheres in healthy subjects Particularly magnetic resonance imaging MRI and positron emission tomography PET are important because of their high spatial resolution and ability to image subcortical brain structures Movement and sensation edit In the 1940s neurosurgeon Wilder Penfield and his neurologist colleague Herbert Jasper developed a technique of brain mapping to help reduce side effects caused by surgery to treat epilepsy They stimulated motor and somatosensory cortices of the brain with small electrical currents to activate discrete brain regions They found that stimulation of one hemisphere s motor cortex produces muscle contraction on the opposite side of the body Furthermore the functional map of the motor and sensory cortices is fairly consistent from person to person Penfield and Jasper s famous pictures of the motor and sensory homunculi were the result Split brain patients edit Main article Split brain Research by Michael Gazzaniga and Roger Wolcott Sperry in the 1960s on split brain patients led to an even greater understanding of functional laterality Split brain patients are patients who have undergone corpus callosotomy usually as a treatment for severe epilepsy a severing of a large part of the corpus callosum The corpus callosum connects the two hemispheres of the brain and allows them to communicate When these connections are cut the two halves of the brain have a reduced capacity to communicate with each other This led to many interesting behavioral phenomena that allowed Gazzaniga and Sperry to study the contributions of each hemisphere to various cognitive and perceptual processes One of their main findings was that the right hemisphere was capable of rudimentary language processing but often has no lexical or grammatical abilities 38 Eran Zaidel also studied such patients and found some evidence for the right hemisphere having at least some syntactic ability citation needed Language is primarily localized in the left hemisphere While the left hemisphere has proven to be more optimized for language the right hemisphere has the capacity with emotions such as sarcasm that can express prosody in sentences when speaking According to Sheppard and Hillis The right hemisphere is critical for perceiving sarcasm Davis et al 2016 integrating context required for understanding metaphor inference and humour as well as recognizing and expressing affective or emotional prosody changes in pitch rhythm rate and loudness that convey emotions 39 One of the experiments carried out by Gazzaniga involved a split brain male patient sitting in front of a computer screen while having words and images presented on either side of the screen and the visual stimuli would go to either the right or left visual field and thus the left or right brain respectively It was observed that if the patient was presented with an image to his left visual field right brain he would report not seeing anything If he was able to feel around for certain objects he could accurately pick out the correct object despite not having the ability to verbalize what he saw Additional images edit nbsp Ventricles of brain and basal ganglia Superior view Horizontal section Deep dissection nbsp Ventricles of brain and basal ganglia Superior view Horizontal section Deep dissectionSee also editAlien hand syndrome Ambidexterity Bicameral mentality Brain asymmetry Chirality Contralateral brain Cross dominance Divided consciousness Dual consciousness Emotional lateralization Handedness Hemispherectomy Laterality Left brain interpreter The Master and His Emissary Parallel computing Psychoneuroimmunology Right hemisphere brain damage Of Two Minds book Wada test Yakovlevian torque 40 References edit Left brain vs right brain How does one dominate www medicalnewstoday com 24 December 2018 Retrieved 10 January 2023 Hemispheric differences and hemispheric dominance video Khan Academy Retrieved 10 January 2023 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 Psychology Hub Retrieved 10 January 2023 Lateralization of Brain Function Simply Psychology www simplypsychology org Retrieved 10 January 2023 Halpern ME Gunturkun O Hopkins WD Rogers LJ November 2005 Lateralization of the vertebrate brain taking the side of model systems The Journal of Neuroscience 25 45 10351 10357 doi 10 1523 JNEUROSCI 3439 05 2005 PMC 2654579 PMID 16280571 Ries SK Dronkers NF Knight RT April 2016 Choosing words left hemisphere right hemisphere or both Perspective on the lateralization of word retrieval Annals of the New York Academy of Sciences 1369 1 111 131 Bibcode 2016NYASA1369 111R doi 10 1111 nyas 12993 PMC 4874870 PMID 26766393 Taylor I Taylor MM 1990 Psycholinguistics Learning and using Language Pearson ISBN 978 0 13 733817 7 p 367 a b Beaumont JG 2008 Chapter 7 Introduction to Neuropsychology Second ed The Guilford Press ISBN 978 1 59385 068 5 Griggs RA 2012 Psychology a concise introduction 3rd ed New York NY Worth Publishers ISBN 978 1429261555 Rogers Lesley J July 2021 Brain Lateralization and Cognitive Capacity Animals 11 7 1996 doi 10 3390 ani11071996 ISSN 2076 2615 PMC 8300231 PMID 34359124 The Optic Nerve Human Anatomy Photius Coutsoukis a b Dehaene S Spelke E Pinel P Stanescu R Tsivkin S May 1999 Sources of mathematical thinking behavioral and brain imaging evidence PDF Science 284 5416 970 974 Bibcode 1999Sci 284 970D doi 10 1126 science 284 5416 970 PMID 10320379 Archived PDF from the original on 19 July 2011 a b Dehaene S Piazza M Pinel P Cohen L May 2003 Three parietal circuits for number processing PDF Cognitive Neuropsychology 20 3 487 506 CiteSeerX 10 1 1 4 8178 doi 10 1080 02643290244000239 PMID 20957581 S2CID 13458123 Archived PDF from the original on 19 July 2011 McGilchrist 2009 provides an extensive survey of the relevant literature in chapter two McGilchrist I Vedantam S 4 February 2019 One Head Two Brains How The Brain s Hemispheres Shape The World We See Audio podcast with transcript NPR Hidden Brain Hecht D October 2010 Depression and the hyperactive right hemisphere Neuroscience Research 68 2 77 87 doi 10 1016 j neures 2010 06 013 PMID 20603163 S2CID 39453265 Braun CM Delisle J Guimond A Daigneault R March 2009 Post unilateral lesion response biases modulate memory crossed double dissociation of hemispheric specialisations Laterality 14 2 122 164 doi 10 1080 13576500802328613 PMID 18991140 S2CID 28225385 Devinsky O January 2009 Delusional misidentifications and duplications right brain lesions left brain delusions Neurology 72 1 80 87 doi 10 1212 01 wnl 0000338625 47892 74 PMID 19122035 S2CID 207103708 Patel Sona Oishi Kenichi Wright Amy Sutherland Foggio Harry Saxena Sadhvi Sheppard Shannon M Hillis Argye E 2018 Right Hemisphere Regions Critical for Expression of Emotion Through Prosody Frontiers in Neurology 9 224 doi 10 3389 fneur 2018 00224 ISSN 1664 2295 PMC 5897518 PMID 29681885 a b Zickert Nele Geuze Reint H Beking Tess Groothuis Ton G G 20 August 2021 Testing the Darwinian function of lateralization Does separation of workload between brain hemispheres increase cognitive performance Neuropsychologia 159 107884 doi 10 1016 j neuropsychologia 2021 107884 ISSN 0028 3932 PMID 34090868 Pulsifer MB Brandt J Salorio CF Vining EP Carson BS Freeman JM March 2004 The cognitive outcome of hemispherectomy in 71 children Epilepsia 45 3 243 254 doi 10 1111 j 0013 9580 2004 15303 x PMID 15009226 S2CID 15894321 Pinel PJ 2011 Biopsychology 8th ed Allyn amp Bacon ISBN 978 0 205 83256 9 nbsp This article incorporates text available under the CC BY 4 0 license Betts J Gordon Desaix Peter Johnson Eddie Johnson Jody E Korol Oksana Kruse Dean Poe Brandon Wise James Womble Mark D Young Kelly A 8 June 2023 Anatomy amp Physiology Houston OpenStax CNX 13 2 The Central Nervous System ISBN 978 1 947172 04 3 Hines T 1987 Left Brain Right Brain Mythology and Implications for Management and Training The Academy of Management Review 12 4 600 606 doi 10 2307 258066 JSTOR 258066 Drenth JD 2003 Growing anti intellectualism in Europe a menace to science Studia Psychologica 45 1 5 13 available in ALLEA Annual Report 2003 Archived 16 June 2011 at the Wayback Machine pp 61 72 Nielsen JA Zielinski BA Ferguson MA Lainhart JE Anderson JS 14 August 2013 An evaluation of the left brain vs right brain hypothesis with resting state functional connectivity magnetic resonance imaging PLOS ONE 8 8 e71275 Bibcode 2013PLoSO 871275N doi 10 1371 journal pone 0071275 PMC 3743825 PMID 23967180 Della Sala S 1999 Mind Myths Exploring Popular Assumptions about the Mind and Brain New York Wiley ISBN 978 0 471 98303 3 Archived from the original on 9 May 2018 a b c Schroeder Thomas 15 July 2023 Left Brain Right Brain Reconceptualized A New Neuroscientific Understanding of an Old Divide Medium Goldberg Elkhonon 2018 A New Look at the Old Riddle Novelty Routines and the Evolution of the Bicameral Brain Japanese Journal of Cognitive Neuroscience 20 3 4 129 138 Westen D Burton L Kowalski K 2006 Psychology Australian and New Zealand edition Milton Qld John Wiley amp Sons ISBN 9780470805527 Toga AW Thompson PM January 2003 Mapping brain asymmetry Nature Reviews Neuroscience 4 1 37 48 doi 10 1038 nrn1009 PMID 12511860 S2CID 15867592 Cognitive psychology Brain Right hemisphere is random and left hemisphere is linear Really Stack Exchange Inc Gazzaniga MS July 2000 Cerebral specialization and interhemispheric communication does the corpus callosum enable the human condition Brain A Journal of Neurology 123 Pt 7 7 1293 326 doi 10 1093 brain 123 7 1293 PMID 10869045 Schematic drawing showing how the left hemisphere differs from the right in mnemonic functions The left is specialized for semantic processing while the right appears to be specialized for episodic memory Harrington A 1 January 1989 Medicine Mind and the Double Brain A Study in Nineteenth Century Thought Princeton University Press pp 87 90 ISBN 978 0691024226 Stiles A 2006 Robert Louis Stevenson s Jekyll and Hyde and the Double Brain SEL Studies in English Literature 1500 1900 46 4 879 900 doi 10 1353 sel 2006 0043 JSTOR 4127513 S2CID 161889732 Broca P 1865 Sur le siege de la faculte du langage articule Bulletins et Memoires de la Societe d Anthropologie de Paris 6 1 377 393 doi 10 3406 bmsap 1865 9495 hdl 11858 00 001M 0000 002A E780 7 Kandel E Schwartz J Jessel T Principles of Neural Science 4th ed p1182 New York McGraw Hill 2000 ISBN 0 8385 7701 6 Sheppard SM Hillis AE December 2018 That s right Language comprehension beyond the left hemisphere Brain A Journal of Neurology 141 12 3280 3289 doi 10 1093 brain awy291 PMC 6262217 PMID 30496360 Shmerling Robert 25 August 2017 Right brain left brain right Harvard Health Publishing Harvard Medical School Retrieved 24 March 2022 External links editLeft Brain Right Brain WrongBibliography editMcGilchrist I 9 October 2009 The Master and His Emissary The Divided Brain and the Making of the Western World Hardcover ed US Yale University Press ISBN 978 0 300 14878 7 Ocklenburg S amp Gunturkun O 2024 The Lateralized Brain The Neuroscience and Evolution of Hemispheric Asymmetries Second Edition Academic Press ISBN 978 0 323 99737 9 https www sciencedirect com book 9780323997379 the lateralized brain Gunturkun Onur Ocklenburg Sebastian 16 October 2017 The Lateralized Brain The Neuroscience and Evolution of Hemispheric Asymmetries Hardcover ed Academic Press ISBN 9780128034538 Further resources editJosse G Tzourio Mazoyer N January 2004 Hemispheric specialization for language Brain Research Brain Research Reviews 44 1 1 12 doi 10 1016 j brainresrev 2003 10 001 PMID 14739000 S2CID 8181841 Cutting J 2012 A Critique of Psychopathology Parodos Verlag ISBN 978 3 938880 51 7 Ornstein R 1998 The Right Mind Making Sense of the Hemispheres Harcourt Brace International ISBN 978 0 15 600627 9 Jill Bolte Taylor 2008 My Stroke of Insight Viking USA 0670020745 Ocklenburg S amp Gunturkun O 2024 The Lateralized Brain The Neuroscience and Evolution of Hemispheric Asymmetries Second Edition Academic Press ISBN 978 0 323 99737 9 https www sciencedirect com book 9780323997379 the lateralized brain Retrieved from https en wikipedia org w index php title Lateralization of brain function amp oldid 1217913288, wikipedia, wiki, book, books, library,

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