L5 hemisphere lateralisation and split brain research

Question 1

Normal visual processing

Answer 1

Information presented in the left visual field of both eyes is processed in the visual cortex of the right hemisphere

Information in the right visual field of both eyes is processed in the visual cortex of the left hemisphere

Question 2

Normal visual information passing

Answer 2

Information passes from the retina of each eye, along the optic nerve to the visual cortex,

where it is immediately shared between hemispheres to provide an integrated visual field

Question 3

Normal visual information shared

Answer 3

Information is shared between hemispheres across the corpus callosum

• dense pathway of around 300 million neural fibres that connects the left and right hemisphere

Question 4

Split brain patients.

Answer 4

Have had a commissurotomy, surgical procedure in which the corpus callosum is severed as a treatment for epilepsy

Although patients overcome the epilepsy, information cannot pass between the left and right hemispheres, and they experience a divided visual field

Question 5

Divided visual field

Answer 5

As the severed corpus callosum divides both hemispheres, information presented in the left visual hemisphere (processed in right) is not shared with information presented in the right visual field (processed in left)

Question 6

Sperry’s procedure

Answer 6

Lab experiment, repeated measures, volunteer sampling

11 split brain participants as facing a central fixation point on a screen, and were briefly presented with words or images (for 1/10th of a second) in their left or right visual field only before being asked to report what they had seen in a variety of ways

Due to their divided visual field:

Information presented in the RVF was processed in the LH without being shared with the other hemisphere + opp

Question 7

Sperry findings

Answer 7

Participants could verbally report words presented to their RVF

Participants could nit report having seen a word presented to their LVF

Question 8

Sperry conc

Answer 8

Left hemisphere is responsible for comprehension and production of spoken language

Language is localised in the left hemisphere

Right hemisphere has no capacity for the production of spoken language

Question 9

Variation 1 procedure

Answer 9

Participants were presented with words in their left visual field and were asked to identify (by touch alone) the correct item from a collection of objects using their left hand

Question 10

V1 findings

Answer 10

Using their left hand, participants were able to identify by touch the correct item from a collection of objects in front of them

However they could not report having seen the word and were unable to explain why they had selected their chosen object

Question 11

V1 conc

Answer 11

Right hemisphere has some language comprehension ability: it can comprehend simple language (e..g nouns) but cannot verbally produce it

Question 12

V2 procedure

Answer 12

Participants were presented with words in their left visual field and were asked to write the word they had been shown using their left hand

Question 13

V2 findings

Answer 13

Using their left hand, participants were able to correctly write the word they had been shown, despite not being able to verbally report having seen a word

Question 14

V2 conc

Answer 14

Right hemisphere has some written ability

: it can comprehend simple language (e.g. nouns) and can write these words

Question 15

V3 procedure

Answer 15

Participants were presented with images of shapes in their left or right visual fields, before being asked to draw what they had seen

Question 16

V3 conc

Answer 16

Right hemisphere is dominant in visual and spatial tasks, such as drawing, which must be localised in the right hemisphere

Question 17

V4 procedure

Answer 17

Participants were presented with images of faces in their left or right visual fields, before being asked to identify the face (by sight) from a selection in front of them

Question 18

V4 findings

Answer 18

Participants were able to accurately identify the correct face when it had been presented in the left visual field but were unable to identify the face presented in their right visual field

Question 19

V4 conc

Answer 19

Right hemisphere is dominant in visual tasks, such as facial recognition, which must be localised in the right hemisphere