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Optigentics And Oscillstions Flashcards

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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
Where does most spiking of hippocampus theta wave happen
Descending phase
26
Gamma waves and basket neurons
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
27
Basket cells and pyramidal cells
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
28
How are gamma waves made
Through excitation-inhibition feedback and inhibition-inhibition feedback Mechanism depends on functional properties of neuronal circuit which oscillation occurs
29
Gamma definition
Umbrella term that describes a variety of different oscillation subtypes in 30-120hz
30
What is the peripheral control of locomotion hypothesis
Sensory feedback from moving limbs drives rhythmic pattern of activity
31
What is central control hypothesis
Neural circuits drive rhythmic pattern
32
What are central pattern generators
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
33
Characteristics of cpg
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
34
Why are CPGs in invertebrates good and bad to study
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
Intrinsic membrane properties of invertebrates
Endogenous bursting- pacemaker activity Plateau potential- bistability Post inhibitory rebound- induce firing by inhibition then release Spike freq adaptation - freq decreases with time
36
How are tadpoles cpg networks studied
Immobilise tadpole by blocking NMJ and create fictive swimming. Electrical activity is recorded from roots or individual neurons
37
What creates very slow negative feedback
Isk (ca) Slow oscillation bursts
38
What makes fast positive feedback
Ica, INa Fast oscillations
39
How are oscillations produced by pacemakers
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
What is in and out phase for synapses
Coupling of oscillators to synchronise them In phase is excitatory Out of phase is inhibitory
41
How do tadpoles swim
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
How can different cpg pattens be made
Coupling and different oscillation freq produce variation of patterns Switching between different types of coordination can be achieved by excitation or through neuromodulators
43
How does modulation of freq of cpg unit work when running
High freq - lowered time of foot on floor Low freq- longer time with legs swinging
44
Where do spinal nerves convey sensory info from and to
From peripheral receptors (soma found in dorsal root ganglion) to synapse with neurons in the dorsal horn of spinal cord
45
What is a dermatome
Area of skin innervated by dorsal root on the left and right side of each spinal segment
46
What are the 4 spinal segments
Cervical- head and shoulders Thoracic- torso Lumbar- front legs Sacral- back legs
47
What is somatotopic organisation
Orderly representation and transmission of sensory information from the periphery of body to brain along topographically organised nerve tracts
48
What is the dorsal columns tract
Axonal projections of dorsal horn to skin are organised into the tract Located between dorsal horns of spinal cord
49
Dorsal columns tract neurons
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
Where do dorsal columns decussate
Dorsal columns nuclei to contra lateral Side
51
Trigeminal tract
Sensory information from face tongue mouth and dura matter follow this tract 1- Trigeminal nuclei decussate 2- thalamus 3- primary somatosensory cortex
52
Function and location of thalamus
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
Function and location of p.somatosensory cortex
Post central Gyrus in parietal lobe Receives projections from vp nucleus Processing of body positions and texture and shape
54
What is the sensory homunculus
Areas represented according to density of innervation
55
What are the types of cortical connectivity
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
What areas are involved in planning of movement
Pfc- integrate of sensory info and evaluate need for motor action Posterior parietal cortex - spatial relationship of body and environment Motor cortex
57
Lateral pathways
Control voluntary movements Corticospinal tract Rubriospinal tract
58
Corticospinal tract
Upper neurons -cortex to ventral horn Lower neurons - ventral hormbgi muscle fibre Decussate at mudullary pyramids
59
Rubrospinal tract
Upper - originates in red nucleus in midbrain Lower- neurons in ventral horn
60
What is a myotome
Group of muscles innervated by all lower motor neurons in a single spinal nerve
61
Phototransduction
Light sensitive photo pigment on outer retina triggers membrane potential change in receptors in response to light
62
Decussation in vision
Light decussates at level of optic chiasm Only temporal visual field
63
Cells of retina
Photoreceptors -convert light into info Bipolar Ganglion Horizontal Amacrine
64
What is receptive field
Area of retina where light stimulation induced a change in mp of a cell Created by direct and indirect input
65
Bipolar cells
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
What is visual field
Region of space seen by both eyes
67
What is visual hemifield
Region of space seen by individual eyes
68
Binocular
Overlapped space seen by both eyes
69
What are the ganglion cell types
M-type P-type Non m and non p
70
Function of fova
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
Pathway of info from retina
Retina Optic nerve LGN Primary visual cortex
72
Where are cell types segregated
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
Properties of V1
6 layers Visual info is segregated by eye and cell type forming ocular dominant columns in layer 4
74
What makes 3D vision
Binocularity occurs in layers of cortex
75
What do simple cells do
Found in layer IV and converge inputs from IV cells which create elongated receptive field. They have centre surrounded organisation
76
Function of complex cells
Receive inputs from simple cells No centre surrounded antagonism Has elongated receptive field
77
Purpose of elongated receptive field in V1
Underlies ability of cells to selectivity respond to stimuli which different orientations and directions of movement
78
What are blobs
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
What are the what and where pathways
Where - dorsal What- ventral
80
What are the connections of cortical areas
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
How is shape perception possible
Upper level of V1 neurons respond to like segments (edges) of objects that’s are aligned with the orientation of their receptive fields
82
How is depth perception possible
Originates from binocular disparity V1 neurons respond to images on and behind plane of fixation
83
How do we perceive motion perception
Visual system integrates local motion signals to determine direction of movement Analysed by MT neurons
84
How is colour perceived v
V4 neurons add main determinates of colour perception

Neural Circuits (5 decks)

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