Motor Cortex:

• Controls voluntary movement

Broca’s area:

• Responsible for the production of speech

Auditory cortex:

• Processes information from our ears

Wernicke’s area:

• Responsible for the understanding of language

Visual cortex:

• Processes information from our eyes

Somatosensory cortex:

• Processes information about touch, pain, temperature and proprioception (the position of your brain)

The brain is divided into two hemispheres:

1. The brain is split into two hemispheres (halves)- the right hemisphere and the left hemisphere

2. The corpus callosum connects the two hemispheres

3. Different functions are dominant in each hemisphere

4. In most people, Broca’s and Wernicke’s areas are only found in the left hemisphere- so it handles most language functions. The left hemisphere is also generally responsible for logic, analysis and problem-solving

5. The right hemisphere is more concerned with things like spatial comprehension, emotions and face recognition

6. This is known as hemispheric lateralisation of function

The two hemispheres can communicate via the corpus callosum:

Each hemisphere generally deals with information from the opposite side of the body.

1. Information from the right visual field (that’s the right half of what you see) goes to the visual cortex in the left hemisphere

2. Information from the left visual field goes to the visual cortex in the right hemisphere

3. Information passes through the corpus callosum to whichever side of the brain needs to deal with it

Split brain surgery gives a research opportunity:

1. In very severe cases of epilepsy, the only treatment available is to sever the corpus callosum. This stops seizures from spreading across the brain

2. But a side effect of splitting the hemispheres is that information can no longer move between them

3. Scientists have used split-brain surgery patients to study the different roles of the two hemispheres

Sperry (1968)- Effects of split-brain surgery:

Method:

• The study involved a combination of case studies and experiments

• The 11 participants had undergone split-brain surgery as a result of epilepsy that couldn’t be controlled by medication

• A control group had no hemisphere disconnection

• In one of the experiments, participants covered one eye and looked at a fixed point on a projection screen

• Pictures were projected onto the left or right of the screen at high speeds so that there was no time for eye movement

Results:

• If the picture was shown in the right visual field, all of the participants could say or write what it was without a problem

• But if the image flashed onto the left the split-brain participants couldn’t say or write down what they’d seen

• They could however select a corresponding object with their left hand, which represented what had been shown to their left eye (right hemisphere), even though they didn’t know why they had selected this object

Conclusion:

• This shows that different areas of the brain specialise in different functions

• The left hemisphere (which receives visual information from the right visual field) can convert sight into spoken and written language

• Usually, information entering the right hemisphere can cross over to be processed in the left.

• As the results show, this can’t happen in split brains, so the information going to the right hemisphere can’t be converted into language at all

• However, the right hemisphere can still produce a non-verbal response

Evaluation:

• Using case studies as well as experiments meant that Sperry obtained both qualitative and quantitative data

• Using both research methods meant that the reliability and the validity of the study were increased

• The study only used 11 participants, which is a very small sample size for being able to generalise the results to others

• It would have been difficult to find a large number of split-brain patients to study

• Epilepsy is usually caused by brain damage and the patients had also been on medication which may have affected their brains

• It is hard to conclude that the ways they processed information would be the same as for people without epilepsy or split-brain treatment

• The study has also been criticised in terms of ecological validity- the experimental situation was artificial, so it’s difficult to generalise the results to real-life situations