PS1003 Andrew: Sensation and Sensory Processing I

Question 1

What is the organisation of the sensory systems?

Answer 1

Peripheral sensory receptors.

Spinal cord and cranium.

Question 2

Organisation of sensory systems: what is the sensory thalamus?

Answer 2

Acts as a filter for all the senses besides one. It does not quite process information but acts as a gate which can enhance or stop information reaching the cortex.

Question 3

Organisation of sensory systems: what is the path of the primary sensory cortex?

Answer 3

goes into and comes from the brain. It is the location of the primary somatosensory cortex, the main sensory receptive area for the sense of touch

Question 4

Organisation of sensory systems: what is the unimodal association cortex?

Answer 4

The initial processing is unimodal so it will be particular an association and process that in isolation from the other modalities. area that primarily deals with information from one sense modality. For example, the visual association cortex is a unimodal association area that is devoted to the integration of different types of visual information.

Question 5

Organisation of sensory systems: what is the multimodal association cortex?

Answer 5

an association area that manages information from multiple sense modalities; a multimodal association area also may integrate information from motor areas.

Question 6

How are the pathways of sensory pathways organised?

Answer 6

in a very similar way

Question 7

How is somatosensory information organised?

Answer 7

● Somatosensory information crosses over- right side of the bran to the left and left side of the brain to the right

Question 8

Organ, Nerve and Cortex for Touch:

Answer 8

skin, spinal cord, somato-sensory

Question 9

Organ, Nerve and Cortex for Sight:

Answer 9

eye, optic II, visual

Question 10

Organ, Nerve and Cortex for Hearing:

Answer 10

ear, vestibulo-cochlear VIII, auditory

Question 11

Organ, Nerve and Cortex for Taste:

Answer 11

tongue, facial VII & glossoph IX & Vagus X, somato-sensory

Question 12

Organ, Nerve and Cortex for Smell:

Answer 12

nose, olfactory I and olfactory

Question 13

What happens to information for the face?

Answer 13

It goes through the cranium nerve and straight to the brain.

Question 14

What are the numbers at the end of the nerves mean?

Answer 14

These are cranial nerves

Question 15

What are cranial nerves?

Answer 15

a bundle of nerves that transmit information straight to the brain

Question 16

What are the five things we can taste?

Answer 16

○ Salty, sour, sweet, bitter, umani

Question 17

Do we have a taste map?

Answer 17

no this is a myth, as do not have different areas of the tongue sensitive to different tastes but rather all the different tastes can be tasted at the whole of the tongue

Question 18

Is there a link between taste and smell?

Answer 18

Smelling food also helps us to taste our food. It is why when we have a cold we are unable to taste things, so it does indeed affect the perception of our food. People with damage to olfactory nerves cannot smell but also cannot properly taste the food.

Question 19

Gustatory pathway: from the taste buds to the taste receptor cells what pathway does it take?

Answer 19

It then goes through the different cranial nerves (facial (VIII), Glosso-pharangeal (IX) & Vagus (X), through the brainstem, then the thalamus to then taste centres of the somatosensory cortex (argued that there is a subsection which is specialised in taste)

Question 20

Gustatory pathway: from the taste buds what pathway do the touch/pain receptors take?

Answer 20

It then goes through the different cranial nerves (facial (VIII), Glosso-pharangeal (IX) & Vagus (X), through the brainstem, then the thalamus to then the somatosensory cortex- this is the pathway where there is a link between taste and pain e.g. burning your tongue

Question 21

How are the cranial nerves involved with taste spatially located?

Answer 21

The facial (VIII) nerve is connected to the first two thirds of the tongue, the Glosso-pharangeal (IX) is connected to the back third of the tongue and the Vagus (X) is located at the roof of the mouth.

Question 22

Olfactory perception: where are olfactory receptors located?

Answer 22

in olfactory epithelium of nose

Question 23

What is the olfactory epithelium?

Answer 23

The olfactory epithelium is a specialized epithelial tissue inside the nasal cavity that is involved in smel

Question 24

Olfactory perception: what is the olfactory nerve?

Answer 24

It is the only instance when the information is not processed through the thalamus but instead the olfactory bulb. each of the first pair of cranial nerves, supplying the smell receptors in the mucous membrane of the nose.

Question 25

Olfactory perception: what is the olfactory bulb?

Answer 25

a neural structure of the vertebrate forebrain involved in olfaction, the sense of smell.

Question 26

Olfactory perception: what is the olfactory cortex?

Answer 26

The primary olfactory cortex is a portion of the cerebral cortex involved in olfaction.

Question 27

Olfactory perception: what is the hypothalamus responsible for?

Answer 27

It is via the hypothalamus not via the thalamus. there is a big connection to this area when responding to olfactory cues as it has connections with the olfactory bulb and the cortex.

Question 28

Hierarchical processing: how is sensory processing organised in a hierarchical manner?

Answer 28

It arrives in the primary sensory cortex and then processed in the unimodal association cortex.

Question 29

What is the pathway for olfactory perception?

Answer 29

Olfactory receptors in olfactory epithelium of nose, then the Olfactor nerve (II) which projects onto the Olfactory bulb which then projects to the olfactory cortex- the last two are linked to the the hypothalamus NOT the thalamus

Question 30

Hierarchical processing: how are things processed in the brain?

Answer 30

different areas of the brain have specific functions- so they process certain aspects of the information coming it. This is similar in all sensory modalities.

Question 31

Hierarchical processing: example of visual system- what are the basics?

Answer 31

Information from eye through optic nerves into the brain

Question 32

Hierarchical processing: example of visual system- what is the ventral stream?

Answer 32

The pathway that has information come through the dorsal lateral geniculate nucleus (LGN) which is in the thalamus. This moves into the primary visual cortex- area V1 (striate cortex) and then it projects to the unimodal association cortices (V2- V5) (extrastriate cortex) and then to the higher processing areas that are still unimodal in the temporal cortex (inferior temporal cortex) – STS, TEO, TE areas of higher processing within the temporal lobe.

Question 33

Hierarchical processing: example of visual system- what is the striate cortex?

Answer 33

Striate cortex (also known as V1) is the main receiving area for visual signals from the LGN. Striate cortex is divided into six layers numbered from 1 (nearest the surface) to 6 (deepest)

Question 34

Hierarchical processing: example of visual system- what is the extrastriate cortex?

Answer 34

The extrastriate cortex is the region of the occipital cortex of the mammalian brain located next to the primary visual cortex, which is also named striate cortex because of its striped appearance in the microscope.

Question 35

Hierarchical processing: example of visual system- where is area V1 located?

Answer 35

right at the back of the occipital lobe (back of the head) which is why when there is a bang at the back of the head it is the V1 that is taking the hit and therefore your primary sensory information will be affected and this is why you see stars.

Question 36

Where is area V1 and what does it do?

Answer 36

Primary visual cortex (striate cortex) and is the first level of input to the visual cortex

Question 37

What does area V1 respond to?

Answer 37

Cells in V1 respond to different aspects of the visual signal (e.g. orientation, size, colour)

Question 38

What responsibilities does area V1 have?

Answer 38

It is involved in characterisation not analysis, so the information that is streamed to V1 is then sent to other areas to be processed. It sends independent outputs to several other areas.

Question 39

What does damage to are V1 lead to?

Answer 39

Damage to V1 leads to total or partial blindness depending on the extent of the damage. So if there is complete destruction, then one is completely blind. But there can just be damages to the area and this could be from sources such as brain damage or tumours

Question 40

How is the visual structure mapped?

Answer 40

Topographical (relating to or representing the physical distribution of parts or features on the surface of or within an organ or organism.- in other words it is physically represented)

Question 41

Hierarchical processing: example of visual system- what is the dorsal stream?

Answer 41

This is when information from the eye goes to the superior colliculus, bypasses area VI and projects to the extrastriate cortex (V2-V5) which projects to the posterior parietal cortex

Question 42

Hierarchical processing: example of visual system- what is the posterior parietal cortex?

Answer 42

(the portion of parietal neocortex posterior to the primary somatosensory cortex) plays an important role in planned movements, spatial reasoning, and attention.

Question 43

What is blindsight?

Answer 43

○ Subjects are blind due to damage to area V1 (large area of blindness in visual field so not completely blind) but they can “guess” direction of travel of a moving object or colour- can get it right 90% of the times which is far more than chance

Question 44

What is not analysed in V1?

Answer 44

movement and colour as those who are blind-sighted are still able to see these- so this information is processed outside of this area

Question 45

How does the superior colliculus involved with visual processing?

Answer 45

When looking at evolutionary levels, we see that the suprior colliculus is an older pathway, and that it processes visual information in a rapid and crude way rather than teh refined way of area V1

Question 46

What happens due to the superior colliculus working quicker?

Answer 46

so an example of this is when getting startled and then realising that it is nothing. This may be happening as a result of the initial information reaching the eye (e.g. light) is getting to the brain in a quick by unprocessed form. This demonstrates how information can get to the primary visual cortex without going through area V1.

Question 47

Despite differences how does the superior colliculus and dorsal LGN work together?

Answer 47

The superior colliculus gets the information to the brain quickly, so we have a rapid response- able to have flight or fight response ready. the dorsal LGN which is a few milliseconds slower then allow you to process the information properly and allows you to make a decision.

Question 48

What does area V3 do?

Answer 48

It is the first stage of building object form. It codes component aspects of the objects e.g. edges, orientation and spatial frequency (which is size. So if something is a long way away it will have a smaller spatial frequency on the retina map than if it was large. It also feeds information to V4, V5, the Superior temporal sulcus (STS), Inferior temporal cortex (TEO and TE)- those last three are higher processors and the parietal cortex

Question 49

What is the function of the parietal cortex?

Answer 49

The parietal lobe is at the back of the brain and is divided into two hemispheres. It functions in processing sensory information regarding the location of parts of the body as well as interpreting visual information and processing language and mathematics.

Question 50

What is area V4 responsible for?

Answer 50

Colour recognition and perception. Has been shown that individual neurons respond to a variety of wavelengths. PET and fMRI studies show that there is activation in V4 to coloured patterns (e.g. alternating between stimuli such as red chequered and black chequered will show V4 becoming more active)

Question 51

What is Achrimatopsia?

Answer 51

It is when there is damage to V4 and causes an inability to perceive colour, so that patients “see in black and white”. There is also an inability to imagine or remember colour, therefore V4 has an important role in analysing colour and colour meaning.

Question 52

What role does the temporal lobe (TEO, TE, STS) play in visual processing?

Answer 52

Highest level of processing of visual information and feeds into the temporal lobe.

Question 53

How does recognition of objects work in the temporal lobe?

Answer 53

Recognition of objects is dependent on their form, but independent of scale (distance), orientation and illumination

Question 54

Where is our visual memory?

Answer 54

It is located in the temporal lobe, so when we see an object and compare it to our data bank we can see how we recognise it compared to previous information.

Question 55

What is the importance of the STS?

Answer 55

It is involved with facial recognition: features of a face (subject specific) e.g. can recognise the person no matter what. Expressions on a face (independent of subject) and gaze direction- whereupon we can analyse where someone is looking

Question 56

Where are the facial recognition aspects located?

Answer 56

They are located in the STS which is a band of tissue down the sulcus. However, all the different aspects of facial recognition are in independent areas, therefore lesions can cause very specific damage such as being able to recognise a person but not the facial expression they make.

Question 57

What is associative visual agnosia?

Answer 57

normal visual acuity but cannot name what they see- able to describe it but cannot name it- there is a disconnection between the temporal and the visual memory system, where there is processing and recall

Question 58

What is apperceptive visual agnosia?

Answer 58

normal visual acuity, but cannot recognise objects visually by shape- can describe what it does
E.g. able to describe what a pen is but cannot recognise the object visually e.g. it is cylindric and that we can write with it

Question 59

What is area V5 responsible for?

Answer 59

Movement perception. Research such as alternating location of black and white chequered shows an acitvation in both V4 (colour) and V5 (motion). Pet and fMRI show that this activation in the V5 is only with moving patterns not stationary.

Question 60

What happens if V5 is damaged?

Answer 60

A woman who suffered a stroke causing bilateral damage became unable to perceive continuous motion and saw only separate successive postions e.g. would not be able to see the visual movment of tea being poured however all other aspects of visual function was fine. She was also unable to see the movement of lips while people spoke but could judge movement of tactile and auditory stimuli.

Question 61

What is the role of the posterior parietal cortex?

Answer 61

Analysis of spatial location of visual cues. Helps to build a image of multiple objects in space and coordinates visually directed movement (e.g. reaching) so it links to motor output pathways. Receives information from all areas of the visual cortex

Question 62

What happens if the posterior parietal cortex is damaged?

Answer 62

Balint’s syndome- where motion and visual are together but there are no difficulties in perception or object recognition.

Question 63

What is optic ataxia?

Answer 63

A form of Balint’s syndrome where subject have a deficit in reaching for objects (misdirected movement)

Question 64

What is ocular apraxia?

Answer 64

A form of Balint’s syndrome where there is a deficit in visual scanning, so cannot coordinate eye movement. there is a difficulty in fixating on an object and they are unable to perceive the location of an object in space.