The Brain Flashcards
(14 cards)
Localisation of Function
Localisation of function is the idea that certain functions (e.g., language and memory) have certain locations within the brain.
Evidence for Localisation of Function
- One such case study is that of Phineas Gage.
- In 1848, while working on a rail line, he experienced a drastic accident in which an iron rod went through his skull.
- Although Gage survived this ordeal, he did experience a change in personality, such as loss of inhibition and anger.
- This change provided evidence to support the theory of localisation of brain function, as it was believed that the area the iron stake damaged was responsible for personality.
- The four areas you need to be aware of are:
1. Motor area
2. Somatosensory area
3. Visual area
4. Auditory area
Motor Area
Theory:
- Responsible for voluntary movements by sending signals to the muscles in the body.
- Located in the frontal lobe.
Study:
- Hitzig and Fritsch first discovered that different muscles are coordinated by different areas of the motor cortex by electrically stimulating the motor area of dogs.
- This resulted in muscular contractions in different areas of the body depending on where the probe was inserted.
- The regions of the motor area are arranged in a logical order, for example, the region that controls finger movement is located next to the region that controls the hand and arm and so on.
Somatosensory Area
Theory:
- Receives incoming sensory information from the skin to produce sensations related to pressure, pain, temperature, etc.
- Different parts of the somatosensory area receive messages from different parts of the body.
- Located in the parietal lobe.
Study:
- Robertson found that this area of the brain is highly adaptable, with Braille readers having larger areas in the somatosensory area for their fingertips compared to normal sighted participants.
Visual Area
Theory:
- Receives and processes visual information.
- Information from the right visual field is processed in the left hemisphere, and information from the left visual field is processed in the right hemisphere - contralateral
- The visual area contains different parts that process different types of information, including colour, shape or movement.
- Located in the occipital lobe.
Auditory Area
Theory:
- Analyses and processes acoustic information.
- Information from the left ear is processed in the right hemisphere and information from the right ear is processed in the left hemisphere.
- The auditory area contains different parts, and the primary auditory area is involved in processing simple features of sound, including volume, tempo and pitch.
- Located in the temporal lobe.
Language Centres: Broca’s Area
- Broca’s area named after Paul Broca, discovered this region while treating a patient named Leborgne, who was more commonly referred to as ‘Tan’.
- Tan could understand spoken language but was unable to produce any coherent words, and could only say ‘Tan’.
- After Tan’s death, Broca conducted a post-mortem examination on Tan’s brain and discovered that he had a lesion in the left frontal lobe.
- This led Broca to conclude that this area was responsible for speech production.
- People with damage to this area experience Broca’s aphasia, which results in slow and inarticulate speech.
Language Centres: Wernicke’s Area
- Carl Wernicke discovered another area of the brain that was involved in
language comprehension. - Wernicke found that patients with damage to Wernicke’s area were still able to speak, but unable to comprehend language.
- Wernicke’s area is found in the left temporal lobe, and is thought to be involved in language processing/comprehension.
- People with damage to this area struggle to comprehend language, often producing sentences that are fluent but meaningless - Wernicke’s aphasia.
- Wernicke concluded that language involves a separate motor and sensory region. The motor region is located in Broca’s area and the sensory region is located in Wernicke’s area.
Hemispheric Lateralisation
Lateralisation is the idea that the two halves of the brain are functionally different and that each hemisphere has functional specialisations, e.g., the left is dominant for language, and the right excels at visual motor tasks. The two hemispheres are connected through nerve fibres called the corpus callosum, which facilitate interhemispheric communication: allowing the left and right hemisphere to communicate with each other.
Split-Brain Research
Sperry and Gazzaniga were the first to investigate hemispheric lateralisation with the use of split-brain patients.
Aim
The aim of their research was to examine the extent to which the two hemispheres are specialised for certain functions.
Method
- Natural experiment.
- An image/word is projected to the patient’s left visual field (which is processed by the right hemisphere) or the right visual field (which is processed by the left hemisphere).
- When information is presented to one hemisphere in a split-brain patient, the information is not transferred to the other hemisphere (as the corpus callosum is cut).
- They conducted describe what you seek tasks, tactile tests and drawing tasks:
- In the describe what you see task, a picture was presented to either the left or right visual field and the ppt had to simply describe what they saw.
- In the tactile test, an object was placed in the patient’s left or right hand and they had to either describe what they felt, or select a similar object from a series of alternate objects.
- In the drawing task ,ppts were presented with a picture in either their left or right visual field, and they had to simply draw what they saw.
Findings
DWYS
1. Picture presented to RVF (processed by LH) - the patient could describe what they saw, demonstrating the superiority of the left hemisphere when it comes to language production.
2. Picture presented to LVF (processed by RH) - the patient could not describe what was shown and often reported that there was nothing present.
TT
1. Object placed in right hand (processed by LH) - the patient could describe verbally what they felt or they could identify the test object presented in the right hand by selecting a similar appropriate object, from series of alternate objects.
2. Object placed in left hand (processed by RH) - the patient could not describe what they felt and could only make wild guesses. However, the left hand could identify a test object by selecting a similar appropriate object, from a series of alternate objects.
DT
1. Picture presented to RVF (processed by LH) - While the right-hand would attempt to draw a picture, the picture was never as clear as the left hand, again demonstrating the superiority of the right hemisphere for visual motor tasks.
2. Picture presented to LVF (processed by RH) - the left hand would consistently draw clearer and better pictures than the right-hand (even though all the ppts were right-handed). This demonstrates the superiority of the right hemisphere when it comes to visual motor tasks.
Conclusion
The findings of Sperry and Gazzaniga’s research highlights a number of key differences between the two hemispheres. Firstly, the left hemisphere is dominant in terms of speech and language. Secondly, the right hemisphere is dominant in terms of visual-motor tasks.
