brain localisation

• Localisation of function is the idea that different parts of the brain perform different functions.
• The brain is divided into two halves, called hemispheres, which are divided by a small gap.
• Different functions are localised to different parts of the brain
• Hemispheric lateralisation is the idea that the two hemispheres perform different functions.
• Language skills are hemispherically lateralised to the left hemisphere.
• Spatial skills are hemispherically lateralised to the right hemisphere.
• Both hemispheres are involved in controlling our movement and all five senses.
• The right hemisphere controls movement of the left side of the body and the left hemisphere controls movement of the right side of the body.
• The left hemisphere processes touch information from the right side of the body, and the right hemisphere processes touch information from the left side of the body.
• Movement, vision and touch are organised contralaterally.
• If functions are organised contralaterally, the right hemisphere controls the left side of the body, and the left hemisphere controls the right side of body.
• The left and right hemisphere communicate by sending nerve impulses to each other via synapses
• The two hemispheres are connected by the corpus callosum.
• The corpus callosum is a bundle of nerve axons that enables communication between the two hemispheres.
• If the corpus callosum is cut, the two hemispheres will no longer be able to communicate with each other.
• Split-brain patients are patients whose corpus callosum has been cut.
• Research that investigates split-brain patients is called split-brain research, and it has enabled researchers to study hemispheric lateralisation.
• In split brain research, the researcher presents a stimulus to either the patient’s left or right hemisphere. Patients are asked to respond by pointing at the stimulus that matches the one they were just shown or asked to describe a stimulus that has been presented to them.
• In split brain research, the stimulus should be presented to just one of the patient's hemispheres at a time
• If a function is not hemispherically lateralised, the patient should be able to perform the function, regardless of whether the stimulus is presented to the right or left hemisphere.
• Sperry and Gazzaniga 1967 presented images to either the patient’s right or left hemisphere.
• Sperry’s first study found that if patients were asked to point to one of four pictures to identify which matched the image, they could perform the task whether or not the image was presented to their right or left hemisphere.
• Sperry’s second study found that if patients were asked to verbally describe the image, they could only perform this task if the image was presented to their left hemisphere.
• Sperry concluded that language is hemispherically lateralised to the left hemisphere.
• Split brain surgery is a rare procedure. Split brain surgery is only done when no other treatment is possible. This is problematic as research is based on small samples with brain abnormalities meaning findings may lack generalisability.
• Not all findings on hemispheric lateralisation have been replicated. For example, more recent studies have shown that not all aspects of language are controlled by the left hemisphere. This is problematic as it contradicts previous research
• Exceptions to theory of hemispheric lateralisation. Danelli conducted a case study using verbal testing and MRI to study EB, who had his left hemisphere removed, and compared to a control group of participants with normal brains. Danelli concluded hemispherically lateralised functions can be taken over by the other hemisphere in some conditions. This is problematic as it contradicts the theory of hemispheric lateralisation.
• Some functions, like vision, hearing, touch, smell, taste, and movement, are controlled by both hemispheres
• The cortex is the outer surface of the brain
• The motor cortex controls our body movement by sending nerve impulses to motor neurons, which control the muscles in our body.
• There’s a motor cortex in the left hemisphere, which controls the right side of the body and there's a motor cortex in the right hemisphere which controls the left side of the body
• Damage to the right motor cortex affects the ability to move the left side of body. Damage to the left motor cortex affects the ability to move the right side of the body.
• The somatosensory cortex processes touch by receiving nerve impulses from sensory neurons, which are next to the sensory receptors on the skin.
• The somatosensory cortex is contralaterally controlled. The somatosensory cortex in the left hemisphere controls touch in the right side of the body. The somatosensory cortex in the right hemisphere controls touch in the left side of the body.
• The auditory cortex processes sound by receiving nerve impulses from sensory neurons that talk to sensory receptors in the ears
• There is an auditory cortex in both hemispheres as both hemispheres are responsible for processing sound
• The visual cortex works by receiving nerve impulses from sensory neurons that talk to sensory receptors in your eyes.
• Vision is organised contralaterally. The left visual cortex processes visual information from the right side. The right visual cortex processes visual information from the left side.
• If you damage the right visual cortex, you lose the ability to process vision and see things on your left side. If you damage the left visual cortex, you lose the ability to process vision and see things on your right side.
• Broca’s area is hemispherically lateralised to the left hemisphere as it is involved in producing language