L6 Locaisation Of Function Flashcards
Define localisation of function
Localisation of function refers to the principle that functions (e.g. vision,
hearing, memory, etc.) have specific locations within the brain.
What has research shows about localisation of function
Some functions are more localised than other . 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).
What is the visual centre and how does it work ?
The visual cortex processes information such as colour and
shape. It is 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 the information onto the visual cortex.
What is the auditory centre
The auditory cortex processes information such as pitch
and volume. It lies within the temporal lobe in BOTH hemispheres of the brain.
The 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.
What is the motor cortex, how does it work
The motor cortex is responsible for voluntary movements.
It is located in the frontal lobe of BOTH brain 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 can cause a loss of
muscle function/paralysis in one or both sides of the body (depending on which
hemisphere/hemispheres have been affected).
What is the somatosensory cortex
The somatosensory cortex is responsible for
processing sensations such as pain and pressure .It is located in the parietal
lobe of BOTH hemispheres.
What two area are the language centres
Broca’s areas , and Wernickes area
What is the Broca’s area
This area is named after Paul Broca who treated patients who
had difficulty producing speech. He found that they had lesions to the LEFT
hemisphere of the frontal lobe. Damage to the Broa’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 (e.g. ‘it’ and ‘the’).
What is the Wernickes area
This area is in the LEFT hemisphere of the temporal lobe.
Carl Wernicke found that 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. The Wernicke Area is
connected to the Broca’s Area by a neural loop. Damage to the Wernicke’s Area
causes Receptive Aphasia. This disorder leads to an impaired ability to
understand language.
What lobes are in what areas of the brain ?
Evaluation of localisation of function (some more localised than others)
Some functions are more localised than others. Motor and somatosensory
functions are highly localised to specific areas of the cortex. However, higher
functions (e.g. personality and consciousness) 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.
Evaluation of localisation of function (equipotentiality theory)
Equipoteniality theory (Lashley, 1930) holds that higher mental functions are
not localised. The theory also claims that intact areas of the cortex take over responsibility for a specific cognitive function following injury to the area
normally responsible.
Evaluation of localisation of function (MRI scans)
Dronkers et al. (2007) re-examined the preserved brains of 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 disruption they do not
usually result in severe disruption of language. Language is a more widely
distributed (and less localised) skill than originally thought.
Evaluation of localisation of function (brain communication is more important)
t 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 Wernicke’s
area.
Evaluation of localisation of function (individual differences)
Bavelier et al. (1997) found that there are individual differences in which
brain areas are responsible for certain functions. They 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.
