Lesson 6 - Localisation of Function Flashcards
Localisation of Function
Refers to principle that functions have specific locations within the brain
Research has shown some functions are more localised than others
The motor and somatosensory functions are highly localised to particular areas of the cortex
Other functions are more widely distributed
The language system uses several parts of the brain, although some components, such as speech production, may be localised (Broca’s Area)
Visual Centres
Visual Cortex processes information such as colour and shape
In the occipital lobe of both hemispheres of the brain
Visual processing starts in the retina where light enters and strikes the photoreceptors
Nerve impulses from the retina are transmitted to the brain via the optic nerve
The majority terminate in the thalamus, which acts as a relay station, passing information onto the visual cortex
Auditory Centres
Auditory cortex processes information such as pitch and volume
Lies within the temporal lobe in both hemispheres
Auditory pathway begins in the cochlea in the inner ear, where sound waves are converted to nerve impulses, which travel via the auditory nerve to the auditory cortex
Basic decoding occurs in the brain stem
The thalamus carries out further processing before impulses reach the auditory cortex
Motor Cortex
Responsible for voluntary movements
Located in the frontal lobe of both hemispheres
Different parts of the motor cortex control different parts of the body
These areas are arranged logically next to one another
Damage to this area causes a loss of muscle function/paralysis in one or both sides of the body
Dependent on which hemisphere has been affected
Somatosensory Cortex
Responsible for processing sensations such as pain and pressure
Located in the parietal lobe of both hemispheres
Language Centres
Broca’s Area
Wenicke’s Area
Language Centres
Broca’s Area
Named after Paul Broca who treated patients with difficulty in speech production
Found they has lesions to the left hemisphere of the frontal love
Damage to the Broca’s Area causes expressive aphasia
This disorder affects language production but not understanding
Speech lacks fluency and patients have difficulty with certain words which help sentences function
Language Centres
Wernicke’s Area
In the left hemisphere of the temporal love
Carl Wernicke found patients with a lesion to this area could speak but were unable to understand language
Wernicke concluded that this area is responsible for the processing of spoken language
Connected to Broca’s Area by a neural loop
Damage to Wernicke’s Area causes receptive aphasia
This disorder leads to an impaired ability to understand language
Brain Diagram
Localisation of Function Evaluation Points
Localisation Distribution
Lashley (1930) - Equipoeniality Theory
Dronkers et al. (2007) - Broca’s Area
Dejerine (1892) - Brain Communication
Bavelier et al. (1997) - Brain areas
Localisation of Function Evaluation
Localisation Distribution
Negative
Some functions are more localised than others
Motor and somatosensory functions are highly localised to specific areas of the cortex
However, higher functions are much more widely distributed
Functions such as language are too complex to be assigned to just one area and instead involve networks of brain regions
Localisation of Function Evaluation
Lashley (1930) - Equipoteniality Theory
Negative
Holds that higher mental functions are not localised
Also claims that intact areas of the cortex take over responsibly for a specific cognitive function following injury to the area normally responsible
Localisation of Function Evaluation
Dronkers et al. (2007) - Broca’s Area
Negative
Re-examined the preserved brains of the two of Broca’s patients
MRI scans revealed that several areas of the brain had been damaged
Lesions to the Broca’s Area cause temporary speech destruction, they do not usually result in severe disruption of language
Language is a more widely distributed (and less localised) skill than originally thought
Localisation of Function Evaluation
Dejerine (1892) - Brain Communication
It may be that how brain areas communicate with each other is more important than specific brain regions
Dejerine (1892) reported a patient who could not read because of damage between the visual cortex and Wenicke’s area
Localisation of Function Evaluation
Bavelier et al. (1997) - Brain Areas
Negative
Found that there are individual differences in which brain areas are responsible for certain functions
Found that different brain areas are activated when a person is engaged in silent reading
They observed activity in the right temporal lobe, left frontal lobe and occipital lobe
This means that the function of silent reading does not have a specific location within the brain
