Split Brain Experiment & Visual Field.

Front 1

You severe the corpus callosum and Anterior comissure of a cat and train it to respond to a given visual stimuli with only one eye. When you give him the task with the other eye, you see that he is still aware of the task, which is not what you expected in a split brain cat. What went wrong?

Back 1

If the optic chiasm is not severed, both hemispheres will receive visual input and hence you do not have complete segregation.

Front 2

What is the purpose of the Tachistoscope and how does it work?

Back 2

The tachistoscope has been designed to account for the optic chiasm that is not severed in human patients since it can relay information to both hemisphere. It is a box that forces the patient to fixate a given point and a stimuli is then presented very briefly to one of the eyes such that the information is only seen in one hemisphere.

Front 3

Describe where does the visual information gets conveyed from the left eye to area 17.

Back 3

Light goes in the left eye hits the retina which then conveys information in the left optic nerve and when the information is at the optic chiasm, information form the nasal retina will cross to the contralateral optic tract while information from the temporal retina will be conveyed in the ipsilateral optic tract which then arrives at the lateral greniculate nucleus. information is then projected to the striate cortex ( area 17) through the optic radiation.

Front 4

The right visual field will projects to which part of the retina in each eye?

Back 4

the temporal retina of the left eye and the nasal part of the right eye.

Front 5

What happens if you have a lesion to the right optic nerve?

Back 5

No vision from the right eye.

Front 6

What happens if you have a lesion to the left optic tract?

Back 6

you do not have vision of the right visual field. This is called right homonymous hemianopsia.

Front 7

What happens when you have a lesion to the optic chiasm? what is this condition called?

Back 7

you will have both temporal visual fields blind. It is called Bitemporal heteronymous hemianopsia.

Front 8

In which sulcus does area 17 lie in?

Back 8

It lies in the calcarine sulcus

Front 9

Which part of the corpus callosum allows for communication between the two striate corteces?

Back 9

The Splenium.

Front 10

In a cerebral commissurotomy which areas of the brain are severed? why would you do this precedure?

Back 10

The anterior commissure and the corpus callosum. This procedure was ment to minimize seizures that were uncontrolled and wouldn't improve through medication.

Front 11

What did Roger Sperry's experiment showed?

Back 11

That the corpus callosum and anterior commissure are necessary to allow communication between both hemispheres other wise you have to "consciousness"

Front 12

What tactile discrimination test did Roger Sperry do on cats?

Back 12

An object discrimination task where the cat can only the forpaw. He could effectively teach the task to pick up two different objects with its two paws and could hence teach a different task for each hemisphere.

Front 13

Why is it imperative that a visual stimulus is presented very briefly in a tachistoscope?

Back 13

It is to prevent the saccade of the eyes towards the object which would mean that both hemispheres would see the object.

Front 14

You examine a split brain patient using a tachistoscope. You briefly present a "red square" on the center of the left visual field very briefly and ask the patient what did he see. To your surprise he tells you "a red square". This astonishes you because the patient's dominant hemisphere is the left not the right. Why was the patient able to say what he saw?

Back 14

The red square was put in the middle of the visual field which means that there is a high chance that both the temporal and nasal retina of the left eye have received the input. The left nasal retina will project to the right hemisphere but the left temporal retina will project to the left hemisphere which would enable a patient to verbalize what he sees.

Front 15

Does the right hemisphere have any language capacity?

Back 15

It can understand simple words but cannot procuce speech or have complicated syntax

Front 16

If you present a red square in the left visual field of a split brain patient, how will he able to respond?

Back 16

He won't be able to verbalize what he saw but he will rightly identify it when selecting an object or pointing at one. He won't be ble to explain why however.

Front 17

When you test a split brain patient by making them name the colour they see in the left visual field, if you only have a choice of two colours what can happen to the patient?

Back 17

Since only the right hemisphere will see the colour the left hemisphere have no clue what it is and will do a guess. If it is incorrect the right hemisphere will create movements of the heads to "indicate" to the left hemisphere that it is wrong and the patient will hence correct his answer.

Front 18

In term of search strategies, which hemisphere is better?

Back 18

The left hemisphere is more efficient than the right.

Front 19

What can be dangerous when asking a patient to draw an object on a paper when seeing two different but related words in each side of the visual field?

Back 19

both can contribute to the drawing to show as if both hemisphere communicated (when they actually did not)

Front 20

What linguistic task showed that the right hemisphere in some individuals have some language capacity?

Back 20

When spelling a simple word using letter blocks and putting them together.

Front 21

In terms of reporting facts, what is the respective tendencies of each hemisphere?

Back 21

The right is more accurate while the left has a tendency to distort the truth.

Front 22

Which hemisphere can pin point the source of a memory using context?

Back 22

the left hemisphere .

Front 23

Which of the two hemisphere is chracterized by " search of meaning" and which one simply stick to facts?

Back 23

Left: interpretation of meaning

right: Stick to facts.

Front 24

According to the theory of evolution, what gave rise to the lateralization of the brain?

Back 24

The fact that the brain increased its specialization for given tasks required more "cortical space" and hence resulted in an asymmetrical specialization of each hemisphere to optimize efficiency.

Front 25

Is the lateralization ( especially language) very salient in a 1 to 3 years old child?

Back 25

No, both hemispheres have equal capacity to develop language.

Front 26

Which hemisphere has its capacity to perceive illusory contours impaired when the shapes doing the illusory contours have a lining?

Back 26

the left hemisphere

Front 27

Do both hemisphere exclusively control the contraleral hand?

Back 27

No, there is some control over the ipsilateral hand but it is much smaller