**L6 - Localisation of Function Flashcards
what is LOCALISATION of FUNCTION?
LOCALISATION OF FUNCTION refers to the PRINCIPLE that FUNCTIONS (such as hearing, vision, memory etc) have SPECIFIC LOCATIONS WITHIN THE BRAIN
Research has shown that 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)
how are the VISUAL CENTRES localised?
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
how are the AUDITORY CENTRES LOCALISED?
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 responsible for and how is it LOCALISED?
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 was affected)
what is the SOMATOSENSORY CORTEX responsible for and how is it localised?
The SOMATOSENSORY CORTEX is RESPONSIBLE for PROCESSING SENSATIONS such as PAIN AND PLEASURE
It is located in the PARIETAL LOBE of BOTH BRAIN HEMISPHERES
what are the TWO LANGUAGE CENTRES in the BRAIN called?
1) BROCA’s AREA
2) WERNICKE’s AREA
what is BROCA’S AREA?
BROCA’S 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 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
what is WERNICKE’S 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’S 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
draw and label the BRAIN AREAS? (4 of them)
On notability
- HIGHER FUNCTIONS (EVALUATION OF LOCALISATION OF FUNCTION)
- 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
- EQUIPOTENIALITY THEORY (EVALUATION OF LOCALISATION OF FUNCTION)
- Another weakness of the LOCALISATION OF FUNCTION THEORY is that EQUIPOTENIALITY THEORY holds that HIGHER MENTAL FUNCTIONS ARE NOT LOCALISED
The theory also claims that INACT AREAS of the CORTEX TAKE OVER RESPONSIBILITY for a SPECIFIC COGNITIVE FUNCTION FOLLOWING INJURY to the area NORMALLY RESPONSIBLE
- DRONKERS ET AL (EVALUATION OF LOCALISATION OF FUNCTION)
- DRONKERS ET AL 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 but they DO NOT USUALLY RESULT IN SEVERE DISRUPTION OF LANGUAGE.
Language is a MORE WIDELY DISTRIBUTED (and less localised) SKILL THAN ORIGINALLY THOUGHT
- DEJERINE (EVALUATION OF LOCALISATION OF FUNCTION)
- It may be that HOW BRAIN AREAS COMMUNICATE WITH ONE ANOTHER IS MORE IMPORTANT than SPECIFIC BRAIN REGIONS.
DEJERINE reported a PATIENT WHO COULD NOT READ BECAUSE OF DAMAGE BETWEEN the VISUAL CORTEX and WERNICKE’S AREA
- BAVELIER ET AL (EVALUATION OF LOCALISATION OF FUNCTION)
- BAVELIER ET AL 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
