Biospychology- Hemispheric lateralisation

Question 1

What is hemispheric lateralisation?

Answer 1

Idea that the two halves of the brain are functionally different and that certain mental processes and behaviours are mainly controlled by one hemisphere rather than the other for example language.

Question 2

What is the definition of split brain research?

Answer 2

A series of studies which began in the 1960s involving epileptic patients who had experienced a surgical separation of the hemispheres of the brain. This allowed researchers to investigate the extent to which brain function is lateralised.

Question 3

Which side of the body does the right side of the brain process information from?

Answer 3

The left side.

Question 4

What side of the body does the left side of the brain process?

Answer 4

Information from the right half of the body.

Question 5

Where does the left visual field project information to?

Answer 5

Left eye: nasal retina
Right eye: temporal retina

Question 6

What pathways do the information from the visual field take?

Answer 6

Information from the left nasal retina crosses to contralateral hemisphere of the optic chasm.
Information from the right temporal retina does not cross so remains in the ipsilateral hemisphere.

Question 7

Where does information from the right visual field project TO?

Answer 7

Right eye: nasal retina.
Left eye: temporal retina.

Question 8

What pathways does information from the right visual field take in the brain?

Answer 8

Information from the right nasal retina crosses to contralateral hemisphere at the optic chasm.
Information from the left temporal retina does not cross so remains in the ipsilateral hemisphere.

Question 9

What is the corpus callosum?

Answer 9

How the two hemispheres communicate.

Question 10

What will happen if the corpus callosum is severed?

Answer 10

Information arriving at the cortex cannot be exchanged between hemispheres.

Question 11

What is a commissurotomy?

Answer 11

An operation to cure epilepsy by severing the corpus callosum the electrical discharge of epilepsy cannot move across to the whole brain when this is cut.

Question 12

What was the aim of Sperry’s study on split brains?

Answer 12

Aim: to examine the extent to which the two hemispheres are specialised for certain functions.

Question 13

What was the procedure of Sperry’s research on split brains?

Answer 13

Procedure – he devised a method called the divided field. This is because the participants would look ahead at a dot in the centre of the screen and see one item to the left and one item to the right for 0.1 seconds (this was to prevent the subject from moving their eyes).

Question 14

What were the four tasks the participants had to complete in Sperry’s (1968) study into split brains?

Answer 14

– Describing what you see
– Recognition by touch
– composite words
– Matching faces

Question 15

What do we already know about hemispheric lateralisation?

Answer 15

We know that language is usually processed by the left hemisphere.
And the right hemisphere seems to have more involvement in the processing of faces and emotions .

Question 16

What were the key findings of Sperry’ study into split brains?

Answer 16

– When presented a picture to the right visual field the patient could describe what they saw demonstrating the superiority of the left hemisphere when it comes to language production.
– When a picture was presented to the left visual field the patient could not describe what was shown and often reported that there was nothing present.
- When objects were placed in the right hand, the patient could describe verbally what they felt.
– When objects were placed in the left hand the patient could not describe what they felt however the left hand could identify a similar object by feeling it.
Also when a picture was presented in the left visual field the person could not verbalise what they saw, however they could draw it demonstrating the superiority of the right hemisphere when it comes to visual motor tasks.


Question 17

What was the conclusions of Sperry’s experiment?

Answer 17

The research highlights a number of differences between the two hemispheres.

Firstly, the left hemisphere is dominant in speech and language.

Secondly, the right hemisphere is dominant in terms of visual#motor tasks.

Question 18

What is the one strength of the idea of lateralisation?

Answer 18

Superior processing skills.

Question 19

What are two limitations of the theory of hemispheric lateralisation?

Answer 19

Methodological issues
Adaption of function.

Question 20

Explain superior processing skills as a strength of hemispheric lateralisation.(PEEL)

Answer 20

P: a strength of the lateralised function suggested by split brain research is support from more recent studies which extend the understanding of hemispheric specialisation.
E: luck et al (1989) show the split brain participants are faster than normal controls at identifying the odd one out in an array of similar object highlighting the specialised processing abilities of the hemispheres.
En: these findings aligned with Sperry earlier conclusions reinforcing the idea that the left and right tennis spheres have distinct functions and ability.
L: this supports earlier findings demonstrating the robustness of the concept that the left brain and the right brain are distinct in terms of function and ability.

Question 21

What are the methodical issues as a limitation of hemispheric lateralisation?(PEEL).

Answer 21

P: a limitation of Sperry research on split brain patient is that methodological challenges that may impact the generalisability and internal ability of the findings.
E: the study was a quasi Experiment so participants are not randomly assigned to groups introducing potential bias only individuals with epilepsy severe enough to warrant surgery were included in the experimental group while the control group consisted of individuals without epilepsy making epilepsy potential confounding variable. This sample was only 11 suggesting population validity.
E: these factors make it difficult to generalise the findings as the unique characteristics of these patients could limit the applicability of the results to a broader population.
L: therefore, the study design and the specific characteristics of the participants made reduce the generalised ability of Sperry conclusions to the general population.

Question 22

What is adaption of function as a limitation of hemispheric lateralisation?(PEEL).

Answer 22

P: limitation of the split brain research is that findings from Gazzaniga (1998) the earlier conclusions of split brain research, particularly regarding the lateralisation of language in the brain.
E: initially split brain research suggested that the right hemisphere was in capable of handling even basic language functions however more recent case studies such as that of patient J.W.demonstrate otherwise J.W.develop the ability to speak using the right hemisphere enabling him to verbally express information information presented to either the left or the right hemisphere.
E: this illustrates the brains remarkable ability to adapt following damage suggesting that language may not be exclusively localised to the left hemisphere as previously thought.
L: therefore, Gazzanigas findings cool into question the validity of the earlier research on hemispheric naturalisation suggesting that the brains language capabilities may be more flexible and less localised than initially believed.