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Advanced molecules, membranes and cells > Superior Colliculus > Flashcards

Superior Colliculus Flashcards

1
Q

Where are colliculi found?

A

dorsal surface of midbrain - 4 in total

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2
Q

Where is main direct anantomical projection from? colliculi

A

retina

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3
Q

Colliculi project to

A

LGN of thalamus then to visual cortex of occipital lobe

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4
Q

2 layers of superior collciulus and functions

A

superficial - visual

deep - auditory + somatosensory

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5
Q

SC superficial layers input

A

only visual

contralateral retina, LGN, visual cortex

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6
Q

SC deep layers input

A

visual
somatosensory
auditory - inf colliculi
motor

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7
Q

SC superficial layers output

A

visual centres - LGN

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8
Q

SC deep layers output

A

ascending and descending fibres

commissural corssing over fibres

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9
Q

3 functions of SC

A

trigger behavioural responses to novel stimuli
integrate sensory information
influence general behaviour state

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10
Q

5 outcomes of SC following novel stimuli

A 
pursue - crossed descending
defend - uncrossed descending
orient 
ANS changes 
EEG arousal
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11
Q

Visual stimulus - SC

A

sensory stimulus activates contralateral SC

orient eyes, ears and head to stimulus

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12
Q

SC ablation

A

unilateral SC ablation

contralateral sensory deficits - auditory, visual and somatosensory

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13
Q

2 visual pathways in CNS

A

analysis of stimuli - geniculocortical system

visual attention/orientation = superior colliculus

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14
Q

What is the sprague effect?

A

Lesion R visual cortex = contralateral neglect

Lesion left colliculus = orientation restored

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15
Q

Explain sprague effect and its implications

A

Left and right SC inhibit eachother
substantia nigra feeds into left SC and right cortex into right SC
lesion right cortex, inhibtion from left SC predominates
get rid of this and restore balance
lesion studies misleading

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16
Q

saccades

A

sudden movements of eyes when scan an image

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17
Q

Brain areas involved in saccades

A

inhibit saccade = dorsolateral PFC

trigger saccade = frontal eye field

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18
Q

explain experiment with SC and visual spatial attention with target and distractor

A

1 part of SC inactivated = hemi-neglect
cool down part dealing with distractor = improve target tracking efficiency
SC inactivated part dealing with target system = decrease efficiency

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19
Q

Subconscious vision/blindsight

A

stroke patients damage to visual cortex - still some visual orientation

20
Q

SC role in consciusness

A

without knowing where you are/posture and sensory information would not be able to have conscious awareness

21
Q

Midbrain auditory maps - relevance

A

barn owl hunts at night

auditory map in deep SC crucial

22
Q

owl - 2 differences of auditory perception

A

interaural timing differences

interaural level differences

23
Q

Inter aural timing differences

A

noise closest to one ear arrives there first

time difference between arriving at 2nd ear

24
Q

Interaural level differences

A

1 ear slightly higher up

25
Q

SC in lower vertebrates

A

tectum

26
Q

Auditory orientation in barn owl

A

ITD, ILD and sound processed and project to inferior colliculi
forebrain and inferior colliculi

27
Q

tonotopic maps

A

centre nucleus of Inferior colliculus

frequency specific channels

28
Q

topographic maps

A

space map - specific locations in colliculus respond to specific locations in periphery
external nucleus IC and tectum

29
Q

how to do electrophysiological mapping in vivo

A

General anaesthetic, expose right SC - remove cortex
anechoic chamber with 12 speakers and lights
neuronal discharge
analyse visual and spatial map

30
Q

anechoic chamber

A

12 speakers and 12 lights in front of animal

31
Q

analysing visual map - electrophysiology

A

topography
on-off responses
directional selectivity
diameter of receptive fields

32
Q

analysing auditory map - electrophysiology

A

topography and on-off responses

33
Q

normalised polar plot

A 
0 degrees in front of animal
180 degrees is back 
probes fire - maximum cell response plot, speakers - how big is response from other location
exclusively from side 
Q50 and Q75
RA = response area
34
Q

Tuned auditory responses

A

tuned topographic map
tuned responses have clear preference to particular stimulus position
RA, Q50 and Q75 small

35
Q

topographic organisation

A

plot position of SC used against position in space = linear relationship
eg front of colliculus response to stimuli at front etc

36
Q

Formation of auditory map in deep SC

A

developmentally organised
different age groups after birth - newborn not tuned
day 32 = tuned responses

37
Q

white noise and SC

A

easier orientation to stimulus
SC not frequency tuned
mixed frequency activates SC better

38
Q

Sc and spatial attention

A

SC both implements motor consequences of attention
crucial role in process of target selection that precedes movement
shifts of covert attention - normal control of spatial attention

39
Q

Multisensory input Sc

A

deep layers
visual/auditory/somatosensory
do get individual senses too but most mixed

40
Q

Most frequent multisensory deep SC input in rodents and rattlesnakes

A 
rodents = visual/somato
snake = visual-infrared - locate prey!
41
Q

Integration in the SC - in vivo electrophysiology

response enhancement

A

bigger neuronal response when multimodal stimuli

amplify one another - even if no response alone can add together to make big response

42
Q

Integration in the SC - in vivo electrophysiology

response depression

A

less firing when combined

stimuli neither spatially or temporally related

43
Q

multisensory integration example

A

cat -bird in tree
auditory alone = nothing
visual alone = nothing
both = auditory and visual input = orientation

44
Q

Multisensory integration - behavioural example - response enhancement

A

weak visual/auditory stimuli - correct approach rewarded
combine both coincidentally
effective enhancement of correct responses

45
Q

multisensroy - response depression example

A

strong visual stimuli
combine visual and auditory 60 degrees apart
depressed in comparison to just auditory

Advanced molecules, membranes and cells (20 decks)

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