Explain one study related to localization of function in the brain.
- State what you are doing in the essay
- This essay will attempt to give a detailed account including reasons or causes of localisation of the brain
- Define Localisation of Function (LOF)
- LOF is the theory that certain areas of the brain correspond to certain functions; in that specific areas of the brain control different functions carried out by the brain.
- It refers to the idea that behaviour, emotions and thoughts originate in the brain in specific locations.
- Therefore, damage to relevant areas of the brain can cause drastic loss of that function and even more, depending on the individual.
- Therefore it is said that many functions of the brain are strictly “localised.?
- State/Introduce the parts of the brain The basic set-up of the brain includes:
- 2 main hemispheres:
- Left – logic, problem solving, maths, and language, controls RHS of body
- Right – creativity, emotion, beliefs controls RHS of body
- 4 main lobes:
- Occipital – vision
- Parietal – higher senses and language functions
- Frontal – reasoning, problem solving, judgement and creativity
- Temporal – perception, hearing (sound recognition), memory and meaning.
- Other important areas of the brain include:
- Broca’s Area – inability to produce language, but could understand/comprehend.
- Wernicke’s Area – inability to understand language, but could communicate/speak
- Introduce research into LOF
- Research from the 19th and 20th centuries has guided us towards a much better understanding of how we should carry out such research into the brain, but more specially, how functions of the brain are localized.
- Possible studies to use for this essay
- Some studies which appear to support and demonstrate localisation of function are:
- Broca – Tan (1861)
- Harlow – Phineas Gage (1849)
- Raine et al. (1997)
- *Roger Sperry (1968) – If this study is chosen, make sure you explicitly state how it is localisation of function.
- *Wernicke (1874)
- Milner – HM (1966)
* The studies with the stars are studies you can incorporate into your response, making sure you explicitly state how it relates to LOF as they are not clear or contain different intentions other than LOF.
- For example Wernicke – you can't really explain the study as he never really conducted an official study, but if you choose Broca then try and explain Wernicke’s study with it.
- Introduce research into LOF (be more specific)
- Scientific research into brain function was, until the 20th century, largely limited to case studies of individuals who were known to have suffered some kind of brain damage or head injury.
- This type of research, not being of an experimental nature, could never clearly establish a cause and effect relationship between the behaviour of the person before death and location of the brain damage.
Study 1: Phineas Gage (1848)
- To investigate the localisation of function in Phineas Gage’s case of how his brain damage resulted in a change of behaviour.
- Specifically, Harlow wanted to investigate how the particular brain damage altered his behaviour.
- Phineas Gage, a 25-year-old railroad worker in the 19th century who survived the passing of an iron rod through his head/skull.
- It entered below his left cheek and exited through the top of his skull on the frontal lobe.
- J.M Harlow nursed Gage to recovery observing his behaviour.
- Harlow observed and studied Gage, having undergone dramatic changes in personality after the injury, which he didn?t show beforehand.
- Harlow described him as having little restraint, using extremely rude language, and making grand plans for the future, which would be instantly replaced with others.
- From Harlow’s study of Phineas Gage, it can be concluded that Gage’s frontal lobes were indeed damaged in the left pre-frontal region, which accounted for his disinhibited behaviour.
- Harlow’s study exemplifies how different parts of the brain, in this case, the frontal lobe which controls personality, relating back to the theory of localization of function, which is that specific regions of the brain are responsible for different functions.
Study 2: Broca – “Tan” (1861)
- Introduce study and link to question:
- Another study from the 19th century which further revealed important and new information about the function of specific areas of the brain was by Paul Broca (1824-80)
- To investigate the localisation of function in a patient called “Tan.”
- Broca wanted to investigate Tan’s unusually language ability/capability by studying his brain.
- Broca studied a patient over a number of years (as it was a longitudinal study), known as “Tan,” because it was one of the few sounds he could make.
- After Tan died, Broca conducted a post-mortem autopsy on this patient (and several others) to figure out what part of the brain caused his or similar conditions.
- After performing the autopsy, he now had evidence that damage to a specific area of the brain was responsible for the loss of ability to produce coherent speech.
- This area became known as Broca’s area.
- The effects of damage to this part of the brain can most easily be observed in the speech of stroke victims, many of whom are temporarily or permanently unable to produce language, a condition known as Broca’s aphasia.
- Broca concluded that the area named after him (Broca’s area) is responsible for an impairment of language in a person.
- Through this study, new understanding and research had arised of “localised functions? of different parts of the brain, as a result of this finding from early research into the brain by scientists such as Broca.
Study 3: Wernicke (1874)
- Introduce study and link to question:
- A further study from the 19th century, very similar to Broca’s which also revealed important and new information about the function of another specific area of the brain was by Carl Wernicke (1874)
- *May want to link with Broca’s area.
- To investigate the localisation of function in patients with brain damage.
- Like Broca, Wernicke wanted to investigate another speech/language and comprehension disorder, in which he believed, resulted from a different area than Broca’s area responsible for the comprehension of speech.
- Wernicke worked in a similar fashion to Broca, by noting behaviour and conducting post-mortem autopsies to locate brain damage after patients had died, particularly in stroke victims.
- After performing the autopsies, Wernicke concluded that there was a section of the brain which was responsible for the comprehension of speech.
- The area later became known as Wernicke’s area.
- Individuals with this type of aphasia might have problems understanding the speech of others or might substitute wrong words into planned phrases.
- He now had evidence that damage to Wernicke’s area was responsible for the loss of ability to comprehend and understand speech, but still being able to speak.
- Through this study, Wernicke concluded that the area named after him (Wernicke’s area) is responsible for an impairment of comprehending/understanding language.
- Through studies like Wernicke and Broca’s, it became clear that specific parts of the brain were responsible for specific human activities and behaviour.
- However, it was still very difficult to find ways to investigate this further, as cases like these were usually rare.
- Furthermore, people could not be operated on as it is deemed to be unethical.
Study 4: Raine et al. (1997)
Aims: The aim of the experiment was to discover (using PET scans) if murderers who pleaded not guilty by reason of insanity (NGRI) to show evidence of brain abnormalities (by observing the cortical and subcortical parts of the brain)
- Was to compare the functioning of various brain structures between NGRI'S and normal subjects using PET scanning technologies
The independent variable in this study was whether the participant was a NGRI or not. The dependent variable was the PET scan results between the controls and the NGRIs.
1 for each subject
- matched for age / sex
- schizophrenics with non-murderer schizophrenics
- all controls screened for mental/physical health)
- 41 participants (39 male, 2 female) who pleaded not guilty for reasons of insanity (average age of 34.3
- Matched with 41 participants (controls) was selected based on sex, age and matched to a NGRI participant
- Each participant was injected with a glucose tracer (bonds to substances like glucose) (for PET scans)
- As the brain uses substances like glucose (as energy) the areas of the brain that are most active absorb it
- The glucose is broken down but the radioactive materials remain and it emits positively charged particles called positrons, which are picked up by the scan
- This information can be read by the computer, producing coloured images on the level of activity throughout the brains
- They had to perform tasks requiring them to detect target signals for 32 minutes
- Compared level of activity (glucose metabolism) in the right and left hemispheres of the brains and the control participants
- Less activity in the parietal and pre-frontal cortex of the brain of those participants charged with murder
- More activity in the occipital areas and no difference in their temporal areas
- Group 1 (those charged with murder):
- Inability to grasp long-term implications of a situation
- Inappropriate emotional expression
- Lack of activity in the amygdala - indicating that violence was due to unusual emotional responses (e.g. lack of fear)
- A large sample was used with many controls to rule out alternative effects on brain activity.
- Previous findings on brain structures involved in violence are supported and new findings revealed.
- The PET scan method can lack precision, as the findings apply only to a subgroup of violent offenders (not to other types of violence or crime) and caution in the interpretation of the findings is needed, which need to be replicated.
- The findings do not mean violence is caused by biology alone (other social, psychological and situational factors are involved).
- It does not demonstrate that the murderers are not responsible for their actions.
- It does not mean PET scans can diagnose murderers and do not say whether the brain abnormalities are a cause or effect of behaviour.
- No control over the level of violence used in the murder.
- Brain scans can be difficult to interpret.
- Ethical implications of socially sensitive research.
- Raine et al's study on NGRI's illustrated localisation of function
- Differences were found in the amygdala and corpus callosum of the NGRI's, amongst various structures, suggesting differences in their experience of emotion of fear and their inability to contemplate consequences of their actions
- The use of this new technology enables psychologists to see the functioning structures of the brain whilst performing specific tasks
- This hence allowed Raine to compare the functions of various brain regions, effectively showing changes in these areas in NGRI subjects and how they subsequently affect subjects' functioning
Study 5: Sperry (1968)
- Introduce study and link to question:
- An influential study, which helped neuroscientists to understand the way brain functions appear to be not only localized in specific regions, but also lateralized – that is, the left and right hemispheres seem to be more or less responsible for certain activities was from the work of Roger Sperry (1968).
- *Be careful with this study, and be explicit about the localization of function that Sperry demonstrated.
- Note that laterization of function is not the same as localization of function, so answers using Sperry need to focus on the function of the corpus callosum, not on differences between left and right hemispheres of the brain.
- To investigate both the localisation and laterization of brain functions.
- To test the effects of a severed corpus callosum, and therefore prove that the two hemispheres have separate functions.
- He selected 11 patients who had severed corpus callosums, where the corpus callosums were severed in epilepsy sufferers to prevent seizures crossing from one side of the brain to another.
- The patients were asked to perform hemisphere-related tasks.
- The tasks included being shown an image on the left or right hand side of their body, where they were asked to identify it or asked to drawn pictures with their left or right hands based off an example.
- Sperry found that the patients could redraw pictures with their left hands, but not with their right.
- This could be due to the fact that the left hand side of the body is controlled by the right hemisphere, which is also the creative hemisphere.
- Sperry also found that when a picture was shown on the left they could not identify it, but could recognise it out of a variety of objects (right hemisphere knows object function but not name).
- Inversely, when the object was shown on the right the patients were able to identify what it was.
- Although, Sperry only had 11 participants, he found significant information into the insight of localization of brain function as well as laterization, which is the theory that the two hemispheres have separate functions.
- His study was seen to have low ecological validity, as it only had 11 participants/patients.
- Furthermore, more research needs to be undertaken regarding people who do not have a severed corpus callosum, so that it can be distinguished as to whether Sperry’s results can be applied to the general population.
- Through this study, Sperry found significant information into the insight of localization of brain function as well as laterization, which is the theory that the two hemispheres have separate functions.
- Laterization of function include the assertion that the right half of the brain is dominant for visuo-spatial ability (demonstrated in tasks like reading maps or recognizing faces), as well as musical abilities and understanding intonation in speech.
- The left half of the brain seems to be more positive than the right and is dominant for language and logical or mathematical abilities.
- His research allowed other research to form and take place to gain more insight into how the different parts of the brain functions.
- What has been discovered through this essay? Make a link to the learning outcome
- The theory of localization of function within the brain is clearly established, and has relevant studies to support it as seen by Harlow’s work on Phineas Gage and other studies.
- It is generally accepted that there are two hemispheres within the brain which each control separate functions.
- Similarly, the four lobes of the brain and other areas of the brain are understood to have separate functions, primarily to do with the senses.
- What did Harlow’s study (or other study) signify?
- Harlow’s study (1848)
helped to demonstrate localization of brain function, in how different parts of the brain are responsible for specific human activities and behaviour.
- State explicitly what area of the brain affected what behaviour in Phineas Gage’s condition.
- In Gage’s case, Harlow discovered that the frontal lobes were responsible a change in personality and emotional vibe, which Gage showed a significant change in behaviour of.
- However, more research needs to be undertaken in this area to ensure better understanding of the human brain.
Hints & Tips
- Short-answer questions may require you to write an explanation of a study connected with localization of function.
- In order to write a good response, you need to describe the study and clearly indicate how it shows that brain functions are localized.
- Specifically: detailing what part of the brain was affected, how the researcher found out, and what the effect on behaviour, cognition or emotion was.