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Neural Circuits > Optigentics And Oscillstions > Flashcards

Optigentics And Oscillstions Flashcards

1
Q

What is optigentics

A

Using opsins to positively or negatively modulate neuronal activity with high temporal resolution

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2
Q

How does optigentics work …

A

Forgin dna from algae expressed which codes for Opsin protein of interest in specific cell types
Promoter codes for expression of gene

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3
Q

What are the methods of gene delivery

A

Transfection
Electroporation
Viral infection

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4
Q

Types of virus used

A

Adeno-associated virus - doesn’t cause disease and onset of gene expression is fast

Adenovirus- can cause disease. Areas of virus genome deleted to prevent disease

Lentivirus - serviced from HIV but genomic deletions ensure inactivity. Enter nucleus of host cell and interstate into genome (stable and lasts months to years)

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5
Q

What are opsins

A

Light activated proteins

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6
Q

Name an opsin to activate neurons and what light activates it

A

Chr2
Blue

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7
Q

Name inhibitory opsin and colour

A

N PHR
Yellow

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8
Q

Why can’t you use gfp with chr2

A

The blue light used to stimulate gfp will activate and open the chr2 channel causing cations to enter and depolarise cell
Don’t want cell to be active during observations as it can cause extra cellular excitotoxicitu or plasticity

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9
Q

What is floxed

A

DNA sequences is flanked by two lox p sites. This means it’s needs cre-recombinase to delete or invert sequence

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10
Q

How to selectively express a gene in particular cell type

A

Breed mice that contain floxed gene in all cell types with transgenic mouse line that express cre-recombinase in one cell type.
Or inject virus into transgenic mouse line that express cre recombinase

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11
Q

What are some gluatamergic neurons

A

Pyramidal- found in all cortical layers
Spiny stellate- later 4

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12
Q

Purpose of feedforward inhibition

A

Acts as a break to liMit speed of excitation

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13
Q

Purpose of lateral inhibition

A

Prevent spread of excitation

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14
Q

Purpose of feedback inhibition

A

Prevent runaway excitation

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15
Q

Purpose of recurrent excitation

A

Amplify a signal

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16
Q

What is a neuronal oscillation

A

waves of electrical activity caused by synchronised brain activity
When neurons connect as groups they are simultaneously active and inactive together

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17
Q

What is a local field potential

A

Measure activity of lots of neurons within sampling radius of electrode

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18
Q

What is a wave phase

A

Angle representing a proportion of oscillation period

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19
Q

What are cortical slow waves

A

<1hz non rem sleep
Upstates - neuronal depolarisation (active)
Downstairs- hyperpolaristaion
Coordinate neuronal population activity in the absence of extrinsic input from environment

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20
Q

Properties of cortical slow waves

A

Input from thalamus
Propogate from rostral to caudal
Important in memory consolidation

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21
Q

Functions of theta oscillations

A

Spatial navigation and performance of cog task

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22
Q

Gamma functions

A

Higher cog processing e.g memory and attention

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23
Q

Properties of sharp wave ripple

A

120-250
Sleep and rest
Originate in hippocampus
Memory consolidation- reactivation of neurons that were previously active during wakefulness
Ca1

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24
Q

Functional connectivity

A

Relationship between anatomically distinct brain areas

Spatial memory- coordinated theta oscillations between pfc and hippocampus

Cog performance- tuning of pfc spiking to specific phases of hippocampus theta rhythm

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25
Q

Where does most spiking of hippocampus theta wave happen

A

Descending phase

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26
Q

Gamma waves and basket neurons

A

Inhibitory fast spiking basket neurons fire almost every gamma cycle in ca3
Basket cells respond maximally to gamma synapses so likely to fire ap when stimulated at that frequency

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27
Q

Basket cells and pyramidal cells

A

Fast spiking basket cells can control timings of pyramidal cell firing
Firing in basket cell drives IPSP of pyramidal
Only able to fire once IPSP had decayed and retuned to rest

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28
Q

How are gamma waves made

A

Through excitation-inhibition feedback and inhibition-inhibition feedback

Mechanism depends on functional properties of neuronal circuit which oscillation occurs

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29
Q

Gamma definition

A

Umbrella term that describes a variety of different oscillation subtypes in 30-120hz

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30
Q

What is the peripheral control of locomotion hypothesis

A

Sensory feedback from moving limbs drives rhythmic pattern of activity

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31
Q

What is central control hypothesis

A

Neural circuits drive rhythmic pattern

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32
Q

What are central pattern generators

A

Neural circuits that generate rhythmic patterns of motor behaviour even in the a sense of sensory feedback inputs. But feedback and sensory stimuli impact are useful to change patterns e.g if stood on a rock

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33
Q

Characteristics of cpg

A

Involved in motor behaviours e.g walking swimming breathing
Automatically generate motor rhythms
Activity modulated by sensory and proprioceptive movements
Brain also involved in coordination of voluntary activity

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34
Q

Why are CPGs in invertebrates good and bad to study

A

Good- small neuronal networks so are easy to study and manipulate

Bad- mostly inhibitory so not good for representing vertebrates which are mostly excitatory

35
Q

Intrinsic membrane properties of invertebrates

A

Endogenous bursting- pacemaker activity
Plateau potential- bistability
Post inhibitory rebound- induce firing by inhibition then release
Spike freq adaptation - freq decreases with time

36
Q

How are tadpoles cpg networks studied

A

Immobilise tadpole by blocking NMJ and create fictive swimming.
Electrical activity is recorded from roots or individual neurons

37
Q

What creates very slow negative feedback

A

Isk (ca)
Slow oscillation bursts

38
Q

What makes fast positive feedback

A

Ica, INa
Fast oscillations

39
Q

How are oscillations produced by pacemakers

A
  1. Inward current quickly depolarise cell into active phase (positive feedback by L type ca channels) and open na and k channel
  2. During active phase there is a slow build up of ca in the cell
  3. When ca is high enough outward k (ca) current brings cell back to silent phase (negative feedback) channels close
  4. During silent phase the cell slowly removes ca and mp returns to baseline
40
Q

What is in and out phase for synapses

A

Coupling of oscillators to synchronise them
In phase is excitatory
Out of phase is inhibitory

41
Q

How do tadpoles swim

A

Post inhibitory rebound
Recurrent excitation and contra lateral inhibition
dIN stimulation results in spiking
(Group of connected din which are exciting each other are stimulated which causes spiking but doesn’t go back to rest)
Because NMDAR have slow decay so cells stay depolarised but don’t spike because Na channels are still inactive and k active
Then din are inhibited because NMDA current string enough to excite neurons which results in swimming

42
Q

How can different cpg pattens be made

A

Coupling and different oscillation freq produce variation of patterns
Switching between different types of coordination can be achieved by excitation or through neuromodulators

43
Q

How does modulation of freq of cpg unit work when running

A

High freq - lowered time of foot on floor
Low freq- longer time with legs swinging

44
Q

Where do spinal nerves convey sensory info from and to

A

From peripheral receptors (soma found in dorsal root ganglion) to synapse with neurons in the dorsal horn of spinal cord

45
Q

What is a dermatome

A

Area of skin innervated by dorsal root on the left and right side of each spinal segment

46
Q

What are the 4 spinal segments

A

Cervical- head and shoulders
Thoracic- torso
Lumbar- front legs
Sacral- back legs

47
Q

What is somatotopic organisation

A

Orderly representation and transmission of sensory information from the periphery of body to brain along topographically organised nerve tracts

48
Q

What is the dorsal columns tract

A

Axonal projections of dorsal horn to skin are organised into the tract
Located between dorsal horns of spinal cord

49
Q

Dorsal columns tract neurons

A

1 order neuron- dorsal horn to dorsal Columns
2 order- columns to thalamus (here projections becoming the medial leminuscus synapse with 3 order)
3- thanks with primary somatosensory cortex

50
Q

Where do dorsal columns decussate

A

Dorsal columns nuclei to contra lateral Side

51
Q

Trigeminal tract

A

Sensory information from face tongue mouth and dura matter follow this tract
1- Trigeminal nuclei decussate
2- thalamus
3- primary somatosensory cortex

52
Q

Function and location of thalamus

A

Found in diencephalon
Relay station for sensory info (except olfactory)
First step in processing sensory info and functions in screening irrelevant info according to behavioural demands

53
Q

Function and location of p.somatosensory cortex

A

Post central Gyrus in parietal lobe
Receives projections from vp nucleus
Processing of body positions and texture and shape

54
Q

What is the sensory homunculus

A

Areas represented according to density of innervation

55
Q

What are the types of cortical connectivity

A

Association fibres (short and long range)- connect nearby regions of cortex
Commisural fibres - connect corresponding regions of hemispheres to coordinate activity of both sides of body

56
Q

What areas are involved in planning of movement

A

Pfc- integrate of sensory info and evaluate need for motor action

Posterior parietal cortex - spatial relationship of body and environment

Motor cortex

57
Q

Lateral pathways

A

Control voluntary movements

Corticospinal tract
Rubriospinal tract

58
Q

Corticospinal tract

A

Upper neurons -cortex to ventral horn
Lower neurons - ventral hormbgi muscle fibre

Decussate at mudullary pyramids

59
Q

Rubrospinal tract

A

Upper - originates in red nucleus in midbrain
Lower- neurons in ventral horn

60
Q

What is a myotome

A

Group of muscles innervated by all lower motor neurons in a single spinal nerve

61
Q

Phototransduction

A

Light sensitive photo pigment on outer retina triggers membrane potential change in receptors in response to light

62
Q

Decussation in vision

A

Light decussates at level of optic chiasm
Only temporal visual field

63
Q

Cells of retina

A

Photoreceptors -convert light into info
Bipolar
Ganglion
Horizontal
Amacrine

64
Q

What is receptive field

A

Area of retina where light stimulation induced a change in mp of a cell
Created by direct and indirect input

65
Q

Bipolar cells

A

Each bipolar cell receives direct synaptic input from a variable number of photoreceptors and indirect input from horizontal cells
They can be on or off
On- depolarised
Off- hyperpolarised

66
Q

What is visual field

A

Region of space seen by both eyes

67
Q

What is visual hemifield

A

Region of space seen by individual eyes

68
Q

Binocular

A

Overlapped space seen by both eyes

69
Q

What are the ganglion cell types

A

M-type
P-type
Non m and non p

70
Q

Function of fova

A

Used to position visual objects that need to be anyalsed in greater detail
Central retina is more represented in V1 than peripheral due to fova

71
Q

Pathway of info from retina

A

Retina
Optic nerve
LGN
Primary visual cortex

72
Q

Where are cell types segregated

A

LGN
Magnocellular - m type 2,7 (upper layer IV)
Pavocellular - m tyoe 6,5,4,3 (lower layer IV)
Koniocellular - Non m and non p

73
Q

Properties of V1

A

6 layers
Visual info is segregated by eye and cell type forming ocular dominant columns in layer 4

74
Q

What makes 3D vision

A

Binocularity occurs in layers of cortex

75
Q

What do simple cells do

A

Found in layer IV and converge inputs from IV cells which create elongated receptive field. They have centre surrounded organisation

76
Q

Function of complex cells

A

Receive inputs from simple cells
No centre surrounded antagonism
Has elongated receptive field

77
Q

Purpose of elongated receptive field in V1

A

Underlies ability of cells to selectivity respond to stimuli which different orientations and directions of movement

78
Q

What are blobs

A

Groups of cells outside layer 4
Important in object colour
Have opponent centre surrounded receptive fields
Respond to different wavelengths of light and some depolarise and some hyperpolersise
Act antagonisticly
Monocular

79
Q

What are the what and where pathways

A

Where - dorsal
What- ventral

80
Q

What are the connections of cortical areas

A

Feed forward- lower to higher areas- transmission of info
Feedback- higher to lower- modulation
Horizontal- across same area- output command generation bro higher order areas

81
Q

How is shape perception possible

A

Upper level of V1 neurons respond to like segments (edges) of objects that’s are aligned with the orientation of their receptive fields

82
Q

How is depth perception possible

A

Originates from binocular disparity
V1 neurons respond to images on and behind plane of fixation

83
Q

How do we perceive motion perception

A

Visual system integrates local motion signals to determine direction of movement
Analysed by MT neurons

84
Q

How is colour perceived v

A

V4 neurons add main determinates of colour perception

Neural Circuits (5 decks)

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