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Neuroscience > Final Material Prep > Flashcards

Final Material Prep Flashcards

1
Q

What is systems neuroscience?

A

The science of networks or circuits of neurons having specific functions

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2
Q

What does firing rate code for?

A

The firing rate codes for the strength of the sensory signal (rate code)

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3
Q

Synchrony code is responsible for coordinated activity

A
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4
Q

Electroencephalography (EEG) is a synchrony code **refer to lecture

A
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5
Q

What does the amplitude of depolarization code for?

A

The amplitude of depolarization codes for the strength of the sensory signal
- The more depolarization, the more transmitter is released

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6
Q

Central Pathway is responsible for:

A

Sensory signals transmitted from peripheral neurons to “central” neurons in the brain

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7
Q

Sensory Receptor Cells:

A
  • Modality specific
  • Transduce energy of different forms to electrical activity so that can be passed onto other neurons
  • Even within a single sensory system, different populations of neurons are specialized to detect different features of the same input
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8
Q

Receptive field is….

A

The location in the environment (or the surface of the body) from which the appropriate stimulus will change that cell’s activity

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9
Q

What is shown in a topographic map?

A
  • Neurons positioned side by side in one region project neurons so they are positioned in the next region
  • Orderly representation of the sensory space in the nervous system
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10
Q

Why does light energy undergo phototransduction?

A

Light energy undergoes phototransduction to trigger neural activities

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11
Q

Pupil

A

The opening that allows light to enter the eye
- Light goes into the retina

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12
Q

Iris

A

Surrounds the pupil
- Responsible for eye color
- Contains muscles that can change the size of the pupil (controls the amount of light reaching the eye)

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13
Q

Cornea

A

Covers the pupil and iris
- Responsible for light refraction

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14
Q

Sclera

A

Continuous with the cornea
- “White of the eye”; is a tough outer wall

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15
Q

Extraocular muscles

A

Move the eye

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16
Q

Where does phototransduction occur?

A

In the retina

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17
Q

What are the five major cell types in the retina?

A
  1. Retinal ganglion cells
  2. Amacrine cells
  3. Bipolar cells
  4. Horizontal cells
  5. Photoreceptor cells
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18
Q

Retinal information processing

A
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19
Q

What is the process of retinal information processing in the linear (direct) pathway?

A

Photoreceptor cells -> bipolar cells -> retinal ganglion cells -> brain

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20
Q

Why are photoreceptor cells unique?

A

Photoreceptor cells are the only cell type directly affected by light

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21
Q

Why are retinal ganglion cells unique?

A

Retinal ganglion cells are the retina’s only output cell type

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22
Q

What is the process of retinal information processing in the lateral (indirect) pathway?

A
  • Bipolar and photoreceptor cells target horizontal cells (and vice versa)
  • Retinal ganglion cells and bipolar cells target amacrine cells (and vice versa)
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23
Q

What are the two types of photoreceptor cells?

A
  1. Rods: ~120 million
    - high sensitivity to light
    - low acuity vision
    - achromatic
    - rare in fovea
  2. Cones: ~ 6 million
    - high acuity vision
    - low sensitivity to light
    - color sensitive (red, blue, green)
    - concentrated in fovea
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24
Q

Cones help detect light of specific wavelengths

A
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25
Q

Where is the fovea located?

A

The fovea is the center of the visual field

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26
Q

What is the process of light reaching photoreceptor cells?

A

Light directly reaches photoreceptor cells at the fovea

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27
Q

The fovea provides color & high resolution vision

A
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28
Q

Where are photoreceptor cells depolarized?

A

Photoreceptor cells are depolarized in the dark

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29
Q

What is the process of depolarizing a photoreceptor cell?

A
  1. Intracellular cyclic guanosine monophosphate (cGMP) binds to cGMP gated Na+ channel
  2. cGMP keeps the channel open and allows Na+ influx
  3. Photoreceptor cell membrane is kept depolarized (-30 mV; DARK CURRENT)
  4. Neuro transmitter glutamate is constantly released at the terminal
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30
Q

Where are photoreceptor cells hyperpolarized?

A

Photoreceptor cells are hyperpolarized in the light

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31
Q

How are photoreceptor cells hyperpolarized?

A
  1. Light stimulation reduces cGMP
  2. Na+ channel closes which allows membrane hyperpolarization (-65 mV)
  3. Glutame release stops at the terminal
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32
Q

What is used by light to decrease cGMP?

A

Light decreases cGMP through transducin (g-protein)

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33
Q

Light intensity gradually changes membrane potential and glutamate release **

A

Glutamate release increases the darker it is

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34
Q

How is a visual image mapped onto the retina?

A

Cells in different locations in the retina have receptive fields in different locations in the visual field

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35
Q

The photoreceptor receptive field:
1. Is circular
2. The receptive field of a given photoreceptor is determined by its location in the retina
3. Photoreceptors respond to changes of light intensity in its receptive field

A
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36
Q

What is a receptive field?

A

In the visual system, a neuron’s receptive field is the location in the visual field (sensory space) from which light changes the cell’s activity
- All cells in the visual system have receptive fields

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37
Q

What types of cells are activated by signals from photoreceptor cells?

A
  • Retinal ganglion cells (RGCs)
  • Amacrine cells
  • Bipolar cells
  • Horizontal cells
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38
Q

Receptive field size differences in distinct RGC types:

A
  • RGCs in peripheral: convergence of synaptic input = large receptive field= M (magno) type
  • RGCs in central: no or less convergence of synaptic input = small receptive field= P (parvo) type
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39
Q

Divergence of single photoreceptor cells onto multiple RGCs leads to…?

A

Overlapping receptive fields

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40
Q

Neighboring RG cells have overlapping receptive fields

A
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41
Q

What are the 2 different glutamate receptors in bipolar cells?

A
  • Inhibitory
  • Excitatory
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42
Q

What is the process of using an inhibitory glutamate receptor process?

A
  1. Glutamate release from pre-synapse in PR cell
  2. Received by inhibitory receptor at post-synapse in BP cell
  3. Decrease membrane potential in BP cell
  4. No neurotransmitter release
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43
Q

In what order do the cells show up in retinal structures?

A

Retinal ganglion cells, bipolar cells, photoreceptor cells

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44
Q

In the visual system, what is the difference between a neuron’s receptive and visual fields?

A

A neuron’s receptive field is the location inside of the visual field (sensory space in which light changes the cell’s activity

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45
Q

Light on in an ON center RG cell… Light on in an OFF center RG cell…

A

Increases APs; decreases APs

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46
Q

The receptive field is comprised of the center + surround

A
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47
Q

What is the mechanism of BP cell response to the receptive field surround?

A

HC depolarization -> PR cell inhibition + BP cell excitation

48
Q

Center PR cell

A

Potential = depolarized + inhibition by HC

49
Q

ON-center BP

A

Potential = hyperpolarized + excitation by HC

50
Q

Light on surround = large decrease of AP

A
51
Q

Light on center = large increase of AP

A
52
Q

Visual perception is not dependent on illumination level

A
53
Q

Why do we see advertisements for bright and dark environments?

A

Contrasts in light intensity are more informative than the overall illumination
- So our perceptions of what we see are not dramatically affected by the level of ambient illumination

54
Q

The retina consists of 3 structures:

A
  • Lateral geniculate nucleus (LGN)
  • Superior colliculus (SC)
  • Suprachiasmatic nucleus (SCN)
55
Q

Suprachiasmatic Nucleus (SCN)

A
  • Receives inputs from intrinsically photosensitive RGC (ipRGC)
56
Q

What is circadian rhythm?

A

24 hour fluctuations of biological processes in the suprachiasmatic nucleus

57
Q

Axons from RGCs in both eyes that are activated by the same object in the visual field converge onto the same neurons in the SC

A
58
Q

Sensory neurons directly synapse onto motor neurons to control movements, such as gaze and saccades

A
59
Q

The SC has a layered structure

A
60
Q

What is the pathway for the LGN?

A

LGN is required to consciously perceive objects

61
Q

In blindsight…

A
  • LGN not functioning
  • SC can track/avoid objects subconsciously
  • SCN responsible for circadian rhythm intact
62
Q

Magno type cells are…

A

Achromatic; 5%

63
Q

Parvo type cells are…

A

Color sensitive, carry detailed information; 90%

64
Q

LGN duties/responsibilities:

A
  • Receive synaptic inputs from RGCs
  • LGN neurons project to the primary visual cortex
65
Q

There are 6 distinct layers in the LGN:

A
  • Lyers 1 & 2 contain larger cells
    ->Magnocellular LGN layer
  • Layers 3-6 contain smaller cells
    -> Parvocellular LGN layer
66
Q

What are the extra layers of LGNs?

A
  • K1-K6 (before layer 1) ventral to each principal layer
  • NonM-nonP type
    -> Koniocellular
67
Q

CICIIC

A

C: Contralateral
I: Ipsilateral

68
Q

Each layer in the right LGN contains a complete disproportionate representation of the left visual field

A
69
Q

Primary Vision Cortex (V1)

A

Topographic map in V1 is inherited from retina
- 1/2 of the neurons in V1 code for the fovea region

70
Q

What are pyramidal cells?

A
  • Single thick apical dendrite that branches towards the end
  • Multiple basal dendrites
  • Axon descending from the soma
  • Long- rage axonal projections
71
Q

What are spiny stellate cells?

A
  • Small neurons
  • Multiple dendrites that radiate from the soma
  • Most of the axons make local connections
72
Q

What are the different types of inhibitory neurons?

A

PYR: pyramidal neuron
PV+: parvalbumin interneuron
SST+: somatostatin interneuron
VIP+: vasointestinal peptide-expressing interneuron

73
Q

What are the stripe like structures in V1?

A
  • Ocular dominance columns
  • indicate recent metabolically active areas
74
Q

What are blobs?

A

Spots in V1 as a result of K layer inputs from LGN
- Blob neurons only respond to color

75
Q

What does the cortical module: hypercolumn entail?

A
  • same receptive field
  • complete coverage of all orientations (multiple orientation columns)
  • input from both eyes
  • multiple blobs
  • repeating modules throughout V1
76
Q

Orientation columns responsibility:

A
  • 36 orientation columns in each cortical module
  • Observed in all layers except layer IVC
  • Neurons in orientation columns analyze the shape, form, or motion of an object
77
Q

Ocular dominance columns responsibility:

A
  • All the neurons in a column preferentially have input from a single eye
  • 0.5 mm wide stripes
  • Each cortical module has 4 ocular dominance columns
  • Neurons in layer IV have exclusive input from one eye
  • Neurons in layer II, III, V, VI have dominant input from one eye, but also have input from both eyes
78
Q

Blobs responsibility:

A
  • Cytochrome oxidase rich neurons
  • Observed in layer II,II, V, VI
  • Arranged in rows (each blob is centered on an ocular dominance stripe in layer IV)
  • Each cortical module has 16 blobs
  • Neurons in blobs are color sensitive, but insensitive to shape
79
Q

What are the 3 parallel pathways of visual information?

A
  • V5: dorsal stream for motion and direction
  • V4: ventral stream for color
  • V4/IT: ventral stream for shape
80
Q

What is the inferotemporal (IT) cortex?

A
  • IT cortex has subsets of neurons that respond selectively to highly complex visual stimuli (hands, face, food)
    -> involved in object recognition
  • A wide variety of colors and abstract shapes are good stimuli for neurons in the IT cortex
81
Q

Order for the receptive field in the central visual pathway:

A

Photoreceptor -> RGC -> LGN -> V1 -> Higher order areas (IT)

82
Q

What are the 3 modalities of somatosensation?

A
  1. Exteroception
  2. Proprioception
  3. Interoception
83
Q

Exteroception:

A
  • Mechanoreception: discriminative touch, social/affective touch
  • Thermoreception: warm/cool
  • Nociception: pain (mechanical, thermal, chemical), itch
84
Q

Proprioception:

A
  • Joint position
  • Muscle length, force
  • Skin stretch
85
Q

Different afferent fibers have different ending structures

A

With end organs = hairy skin
Without end organs = bare skin

86
Q

What is the function of the 4 classes of afferent fibers?

A

Convey signals from body/organ surface to CNS

87
Q

The sense of touch

A
  • Mechanoreception
  • Myelinated fibers: Aalpha, Abeta, Adelta
  • All have end organs, triggered by physical deformation
  • Cell bodies in dorsal root ganglion and trigeminal ganglion
  • Topographic mapping
88
Q

The microneurographic technqiue

A

Thin electrode contacts an afferent nerve fiber and impulses from the cutaneous sense organ respond to touch

89
Q

Depth of end organ determines size of receptive field which determines amount of response properties

A
90
Q

Receptor density -> sensitivity

A
91
Q

2 Point Discrimination

A

The ability to discriminate that two close-by points touching the body surface are truly separated

92
Q

Thermoreceptors

A
  1. Cold receptors:
    - Adelta bare nerve endings
    - 100 x more sensitive to sudden cooling than to gradual skin cooling
  2. Warm receptors:
    - C bare nerve endings
    - Equally sensitive to rapid and slow warming
    - Stop firing at 45 C
93
Q

What does the primary somatosensory cortex (S1) entail?

A
  • Modality segregation
  • Somatotopy
  • Column Structure
94
Q

What is somatotopy?

A

Orderly representation of the body surface area in the somatosensory cortex

95
Q

Columnar structure in S1:

A
  • Column: neurons spanning vertically across multiple layers sharing similar response properties
  • Same receptive field
  • Respond to a certain type of tactile feature
96
Q

Recording in humans (microneurographic technique) is limited in revealing central mechanisms…

A

Animal models of whiskers are used instead

97
Q

Rodent whisker system advantages

A
  • The neural circuits from periphery to CNS is relatively simple (only 3 synapses from whisker to cortex)
  • Exquisite somatotopy (each whisker represented in S1 by distinct group of neurons)
  • Genetic accessibility (mouse)
  • Powerful recording techniques during behavior
98
Q

Bottom-up sensory pathway (whiskers)

A

Whiskers - brainstem - VPM thalamus - S1 cortex

99
Q

Calcium pacing allows for monitoring the activity of hundreds of neurons simultaneously

A
100
Q

Optogenetics

A

Genetically encoded light activated ion channels
- Allows changing neuronal activity at fine timescales

101
Q

Tactile detection of head fixed mice

A

Head-fixed mice are trained to report the perception of a single whisker deflection by licking toward a water port. They are also trained to withhold licking in the absence of whisker deflection. Neuronal recording and perturbations can be performed simultaneously during task performance.

102
Q

Different types of motor control

A
  • Reflexive: triggered by external events
  • Rhythmic: walking, chewing, whisking
  • Voluntary: self initiated, goal directed
103
Q

Spinal cord: reflex, rhythmic

A

Innervate muscle

104
Q

Brainstem: reflex, rhythmic

A

Innervate spinal cord and muscle

105
Q

Forebrain: voluntary

A

Does not directly innervate muscle

106
Q

What is the importance of the brain stem?

A
  • Signals from the periphery go through brainstem to the rest of the brain
  • Controls vitals such as blood pressure and respiration
107
Q

What is the importance of the basal ganglia and cerebellum?

A
  • Interconnected with cortex
  • Controls smooth movement and posture
  • Don’t directly project to spinal cord or motor neurons
108
Q

Each fiber in the muscle is innervated by a single axon branch from the CNS

A
109
Q

1 motor neuron = multiple fibers; 1 muscle fiber = 1 neuron

A
110
Q

Alpha motor neuron

A
  • Directly triggers the generation of muscle force
  • A single alpha motor neuron innervates multiple muscle fibers
111
Q

Flexor vs. Extensor

A
  • Extension: contraction of the extensor pulls the left end of the bone upward causing the right end to pivot downward
  • Flexion: contractions of the flexors pull the right end of the bone upward
112
Q

Locomotion cat experiment

A
  • Cat is paralyzed and can’t consciously move its lower body. It’s supported on a sling and its legs are placed on a treadmill. The cat can’t initiation locomotion by itself, but it can be made to walk with perfect coordination on 4 limbs if we stimulate the brainstem or turn on the treadmill
113
Q

Neuronal mechanisms for locomotion

A
  • central pattern generators
  • command neurons
  • sensory inputs
  • coordinating fibers
114
Q

Central Pattern Generator (CPG)

A
  • A network of neurons that produces rhythmic output based on intrinsic properties of individual neurons
  • can generate complex patterned output even if the CPG is isolated from the brain and sensory inputs
115
Q

Command neurons for locomotion are located in the mesencephalic locomotor region (MLR)

A
116
Q

Stretching of the muscle spindle induces depolarization of the sensory axon

A

Sensory feedback activates CPG

117
Q

Complex movement occurs in 3 stages (picking up a cup)

A
  1. Spatial assessment: analyze where you are with respect to the cup
    - Posterior parietal cortex
  2. Planning strategy: plan for picking up cup
    - Premotor cortex
  3. Detailed execution: control which muscles contracted in what order and strength
    - Primary motor cortex

Neuroscience (8 decks)

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