Localisation of Brain Functions Flashcards
Who founded Localisation Theory
Broca and Wernicke
What is Localisation Theory
Different parts of the brain are responsible for different functions
if an area is damaged, function will be impaired
The cortex of both hemispheres is divided into four lobes
each lobe has a different function
How did Localisation Theory challenge Holistic Theory
Because holistic theory stated that all parts of the brain were involved in the processing of thoughts and actions
Phineas Gage (evidence of localisation)
While working on the railways, a metal rod was blasted through Gage’s left cheek behind his eye and through his brain and skull
Gage survived, but became rude, aggressive and irritable due to the damage done to his frontal lobe
What are the 4 lobes
Frontal Lobe
Paretial Lobe
Occipital Lobe
Temporal Lobe
Where is the motor area
Frontal lobe
Where is Wernicke’s area
Temporal lobe
Where is Broca’s area
Frontal lobe
What does the Motor Area do
Controls voluntary movement in the opposite side of the body
Damage may result in loss of control over fine movements
What does the Somatosensory Area do
Where sensory information from the skin is represented
The more sensitive the area, the more space is devoted
What does the Visual Area do
Each eye sends information from the right visual field to the left visual cortex, and from the left visual field to the right visual cortex
Damage to the left hemisphere can produce blindness in part of the right visual field of both eyes
What does the Auditory Area do
Analyses speech based information
Damage could cause partial hearing loss
Damage to specific areas may affect the ability to understand language
Where is the Motor Area
Back of Frontal Lobe
Where is the Somatosensory Area
Front of Paretial Lobe
Where is the Visual Area
Occipital Lobe
Where is the Auditory Area
Temporal Lobe
Broca’s Area
Found in the left hemisphere
Frontal lobe
Responsible for speech
Damage will cause Broca’s Aphasia
Broca’s Aphasia
Non-fluent Aphasia
Causes, slow, laborious speech that lacks fluency
Wernicke’s Area
Found in the left hemisphere
Temporal lobe
Responsible for language comprehension
Damage causes Wernicke’s Aphasia
Wernicke’s Aphasia
Fluent Aphasia
Production of nonsense words that don’t make sense
Having Broca’s and Wernicke’s Aphasia
Global Aphasia
Evaluation (STRENGTH) - Brain Scan Evidence of Localisation
Peterson et al (1988) - used brain scans to show that Wernicke’s Area was active during listening tasks and Broca’s Area was active during reading tasks
Tulving et al (1994) - Semantic and episodic memories are stored in different parts of the prefrontal cortex
Demonstrates localisation theory is reliable
Evaluation (STRENGTH) - Neurosurgical Evidence in Support
Lobotomy-Surgically removing areas of the brain to control behaviours (developed by Walter Freeman in 1940s)
Early attempts were brutal and imprecise, and typically involved severing connections in the frontal lobe to try and control aggression
Neurosurgery is used today in extreme cases of OCD and depression
Dougherty et al (2002) -
44 OCD patients had a cingulotomy follow up after 32 weeks
1/3 had a successful response
14% had a partial successful response
Symptoms related to mental disorders are localised to one area of the brain
Evaluation (STRENGTH) - Case Study Evidence
Phineas Gage
However, this is a single case study, is not generalisable and lacks population validity
Evaluation (WEAKNESS) - Lashley’s Research
Challenges localisation theory
Removed between 10-15% of the cortex in rats who were learning to navigate a maze
No area was found to be more important than any other in their ability to learn the maze
In conclusion, learning appeared to require every part of the cortex and is not confined to a particular area so learning is not localised
However, this study does have the issue of extrapolation
Evaluation (WEAKNESS) - Plasticity
Plasticity - when the brain has been damaged, and a function is lost, the rest of the brain seems to reorganise itself in an attempt to recover the lost function
Lashley described this as the Law of Equipotentiality - whereby surviving brain circuits chip in so the same neurological action can be achieved
although this does not happen every time there are several documented cases of stroke victims being able to recover those abilities that were lost as a result of the illness
This challenges localisation as it suggests all parts of the brain can perform all functions, making it not localised
