Occipital Lobe

Question 1

What is occipital lobe responsible for?

Answer 1

vision

Question 2

Calcarine sulcus

Answer 2

divides the top and bottom visual field; contains most of the primary visual cortex

Question 3

Medial view of occipital lobe

Answer 3

• calcarine sulcus

Question 4

Ventral view of occipital lobe

Answer 4

• lingual gyrus (V2 and VP) and fusiform gyrus (V4)

Question 5

Lateral view of occipital lobe

Answer 5

• no clear division

Question 6

Fusiform gyrus

Answer 6

• contains area V4; extends to temporal lobe

Question 7

Extrastriate cortex

Answer 7

• higher order processing
• includes recognition of shape, motion, and colour
• visual input is sent from V1 to this area

Question 8

Stirate cortex

Answer 8

• another name for V1 due to its striped appearance
• has a distinct laminar organization (light, dark, light, dark)
• has a heterogenous function (has more than one function)

Question 9

What technique can be used to assign names for parts of the occipital lobe and determine their function? How was it used in determining determining anatomy and function for areas V1 and V2?

Answer 9

Staining technique can be used to determine anatomy and then function. Staining was used for V1 and V2. There were different forms of stains such as blobs, stripes, and interblobs indicating that there are different functions in these areas. Blobs determine sensation of color. Thin stripes are perception of color. Thick stripes are form and motion perception. Interblobs are sensitive to orientation.

Question 10

What is the difference between perception and sensation?

Answer 10

Perception is the processing of incoming information, meanwhile sensation is the incoming information.

Question 11

From where does V1 receive information from and where does V1 send information to?

Answer 11

V1 receives visual input from the LGN, and then sends it off to the extrastriate cortex for higher order of processing.

Question 12

How many layers are in the human cortex?

Answer 12

Traditionally it is believed to have 6 layers. However, recently it has been reported that the V1 contains more than 6 layers. In terms of function this would probably make sense.

Question 13

What is area V4 responsible for? Where is it located?

Answer 13

The primary job of area V4 is colour vision. It is also plays a role in detection of movement, depth, and position. V4 is located in the extrastriate cortex.

Question 14

What are the three pathways that V2 is connected to?

Answer 14

V2 is known as the helper of V1. It has three pathways in which information is passed onto in the extrastriate cortex. One pathway is out to the parietal lobe - the dorsal stream. Another pathway is out to the inferior temporal lobe - the ventral stream. Last pathway is output to the superior temporal sulcus - STS stream.

Question 15

Briefly mention what kind of visual information is passed on to each of the output streams from the V2 area.

Answer 15

The dorsal stream takes in information regarding visual guidance of movements (i.e. where pathway). For example, it helps determine whether you should move your arm upwards or downwards to pick up a water bottle. The ventral stream takes in information regarding object perception (i.e. what am i looking at). The STS stream is involved in visual spatial function.

Question 16

How is social perception and cognition organized within the STS?

Answer 16

Social perception and cognition is organized into language, voices, faces, biological motion, and theory of mind.

Question 17

Why is it difficult for people with autism to interact with others?

Answer 17

It is difficult because their theory of mind is disrupted which prevents them from being able to guess what is going on in other people’s minds. Theory of mind allows individuals to be aware of what someone else might be thinking or doing. But for people with autism, they find it difficult to understand and be aware of what others are thinking of, and hence find it difficult to interact with them.

Question 18

In macaque monkeys, where is area V4 located? What is this area referred to in humans?

Answer 18

In macaque monkeys, the area V4 is located in the lingual gyrus. This area is referred to as hV4 in humans.

Question 19

What area of the brain are the blobs in V1 connected to?

Answer 19

Blobs in V1 determine sensation of colour, and hence are connected at area V4 in the extrastriate cortex, which is responsible for colour vision.

Question 20

What area of the brain are the interblobs in V1 connected to?

Answer 20

Interblobs in V1 are sensitive to orientation. They are connected to area MT/V5, which is also the motion sensory of the brain.

Question 21

Area V1 and V2 have a connection to area V3 of the brain. Is this statement true or false?

Answer 21

True. Area V1 and V2 are connected to area V3 which is responsible for shape of objects in motion.

Question 22

A physician holds a ball in front of the patient, which the patient claims they cannot see. However, when the physician throws the ball at them, the patient catches it. Why does this occur?

Answer 22

This occurs due to a lesion in some area of the primary visual cortex. Primary visual cortex is associated with your conscious ability to describe where objects are. Hence, why the individual cannot see the object. However, they are still able to catch the ball because they reacted unconsciously, and only their conscious ability to describe what they see, is limited.

Question 23

Is vision limited to areas in the occipital lobe?

Answer 23

No, the brain has about 55% vision-related areas of the total cortex.

Question 24

List the five categories of vision.

Answer 24

Vision for action, action for vision, recognition, space, and how to not get overwhelmed

Question 25

What is the difference between vision for action and action for vision?

Answer 25

Vision for action is involved with using vision to carry out everyday tasks. For example, ducking, catching, etc. It is more spontaneous. Action for vision follows the idea that we guide our attention by using vision, but it is attention that guides our movement connected to vision.

Question 26

What is the difference between top-down processing and bottom-up processing?

Answer 26

Bottom-up processing refers to processing sensory information as it is coming in. It is more of a spontaneous process. Top-down processing refers to the perception of vision involving cognitive function. Your brain applies what it knows, and what it expects to perceive, and then fills in the blanks. Action for vision is performed by top-down processing.

Question 27

How can you assess if someone has agnosia?

Answer 27

Agnosia is loss of visual knowledge. It can be tested by asking individuals to draw what they see and then assessing eye movement using an eye tracking device. Eye movements of an agnostic subject would be random when asked to draw an object such as a sphere.

Question 28

Which category of vision involves the temporal lobe?

Answer 28

Visual recognition involves the temporal lobe and is involved in recognizing objects.

Question 29

Which category of vision is responsible for spatial functions?

Answer 29

The visual space category is responsible for spatial functions. This category involves the parietal lobe which is the primary for where things are located.

Question 30

What are the two types of spatial functions?

Answer 30

There is egocentric spatial function which involves location of an object relative to a person, and allocentric spatial function which involves location of an object relative to another object.

Question 31

Why does our brain not capture everything around us?

Answer 31

Our brain does not capture everything around us because it does not want to get overwhelmed. This idea has to do with the last category of vision - visual attention (i.e. how not to get overwhelmed). When we look at the environment or at an image, we only focus on one aspect of the image, and not everything.

Question 32

What is the overall purpose of the Milner-Goodale Model? What does it say?

Answer 32

Milner-Goodale Model tries to differentiate the different hierarchical visual pathways in a way so that it connects to either recognition or action. Recognition is found in the temporal visual areas describing the ventral stream (what pathway). It involves V3 responsible for dynamic form, and V4 responsible for colour form. Action is found in the parietal visual areas describing the dorsal stream (where pathway). It involves V5 responsible for motion and V3A responsible for form.

Question 33

What type of blindness occurs when the optic nerve or retina is damaged?

Answer 33

Monocular blindness occurs when the optic nerve or retina is damaged. This results in loss of sight in one eye.

Question 34

What is hemianopia? Describe the different types of hemianopia blindness’.

Answer 34

Hemianopia is when one part of the entire eye’s visual field is blind. This results in complete lesion of area V1. There are various types including, bitemporal hemianopia, right nasal hemianopia, and homonymous hemianopia. Bitemporal hemianopia is due to the formation of a tumor on the pituitary gland, which places pressure on the optic chiasm. This results in loss of vision in the temporal fields of both eyes (because it says bitemporal). Right nasal hemianopia is due to lesion in the lateral chiasm which leads to loss of vision in one nasal field. Homonymous hemianopia results in loss of sight in one visual field due to damage in the optic tract, LGN, or V1.

Question 35

Define quadrantanopia.

Answer 35

Quadrantanopia is when there is a loss of vision in one-quarter of the visual field. This is usually due to a visual cortex lesion.

Question 36

What type of blindness results in the central part of the eye being preserved?

Answer 36

Macular sparing results in the central part of the eye - macular, being preserved. Lesions of the occipital lobe often spare the macular region of the visual field. It helps differentiate lesions in the optic tract and the thalamus.

Question 37

What type of blindness results from small visual cortex lesions near the calcarine sulcus?

Answer 37

This type of lesions produce blind spots, or scotomas.

Question 38

What causes blindsight? Use Patient B.K.’s diagnosis and symptoms to help explain this concept.

Answer 38

Ans: Patient B.K. was diagnosed with quadrantanopia, which is when there is a loss of vision in one-quarter of the visual field due to visual cortical lesions, and right infarct tissue in the occipital lobe, which is basically dead tissue. Patient B.K. experienced what is called blindsight. Blindsight is having no conscious recollection of seeing something. When there is damage in area V1 we know that it is going to affect the conscious ability of visual processing. When asked if patient can see the pen that is being held in the visual field that they are experiencing blindness, they say they cannot identify the object - they see nothing. When the pen is moved in various directions, the patient is unconsciously able to determine which direction the pen is moving in - they themselves are unaware of how they are able to do this because they still see NOTHING. Blindsight reveals the idea of nonconscious processing.

Question 39

Patient D.B. had symptoms of cortical blindness (i.e. blindsight) and hemianopia. What caused this?

Answer 39

An MRI revealed that patient D.B. had an angioma in the right calcarine sulcus. An angioma is presence of abnormal blood vessels.

Question 40

The doctor tells Patient L.M. that she/he has vascular abnormality due to damage in area V5/MT of the brain. What does this mean for patient L.M? How do you think the doctor came up with this diagnosis?

Answer 40

Vascular abnormality means that there are some blood flow issues. Damage to area V5 or known as area MT means there is going to be an impairment in movement guided by vision, since this area is known for motion pathway. The doctor probably came up with this diagnosis by looking at the individual’s symptoms. Patient L.M. was unable to intercept moving objects using her hand.

Question 41

Describe the Case Study on Patient V.K.

Answer 41

Patient V.K. had bilateral hemorrhages in occipitoparietal regions of the brain. The symptom was optic ataxia. Optic ataxia is impairment in using visual information to guide motor movements.

Question 42

Patient D experiences prosopagnosia. What does that mean? Where must have the damage occurred?

Answer 42

Prosopagnosia is a deficit in facial recognition. This is a result of lesion in the right occipitotemporal region of the brain. This may be due to the fact that temporal regions are responsible for labelling.

Question 43

What happens when there is a left occipitotemporal lesion?

Answer 43

This can be seen in Patient T who had a left occipitotemporal lesion. It resulted in alexia which is inability to read.

Question 44

What are the diagnoses that can be made when an individual has a gross bilateral damage to the occipital cortex?

Answer 44

Individuals can be diagnosed with apperceptive object agnosia, which is when individuals are unable to recognize, copy or match shapes. Another form of apperceptive object agnosia is simultagnosia, which is also caused by gross bilateral damage to the occipital cortex. Simultagnosia is when an individual is unable to perceive more than one object at a time.

Question 45

What are the two different types of object agnosias’?

Answer 45

There are two types of object agnosia - apperceptive object agnosia and associative object agnosia.

Question 46

What is associative object agnosia?

Answer 46

Associative object agnosia is when an individual is able to perceive the object but cannot identify it. This is usually caused by lesions to the anterior temporal lobe.

Question 47

What is another name for facial agnosia? What causes this?

Answer 47

Prosopagnosia is when individuals are unable to recognize previously known faces. This can occur due to bilateral damage in the temporal cortex.

Question 48

What form of agnosia results in the patient being unable to read?

Answer 48

Alexia results in individuals not being able to read. This occurs due to damage in the left fusiform and lingual areas.

Question 49

Define visuospatial agnosia.

Answer 49

Visuospatial agnosia results in topographic disorientation which means the individual is unable to find their way. This form of agnosia is also associated with other symptoms like difficulty recognizing faces. This is caused by damage to the occipitotemporal regions including medial fusiform and lingual areas.