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Neuroscience Y3S1 > Introduction to Sensory Processing > Flashcards

Introduction to Sensory Processing Flashcards

1
Q

Name the ‘type’ of sensory processing/coding that takes place in the olfactory system. (1)

A

Population coding

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2
Q

True or false? Explain your answer if necessary. (1)

In the olfactory system, and other brain systems, single neurones encode individual stimuli.

A

False - population coding occurs, where combinations of neurones encode a stimulus

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3
Q

What are the collections of neurones called in the olfactory bulb where primary olfactory neurones which detect similar stimuli synapse? (1)

A

Glomeruli

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4
Q

What is the missing word? (1)

………………… are the functional units of the olfactory bulb that process odours.

A

Glomeruli

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5
Q

Why are several glomeruli in the olfactory bulb activated when detecting a smell? (2)

A

Because smells are made up of different odour stimuli (chemicals)

which all activate different glomeruli.

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6
Q

What is meant by a ‘neuronal ensemble’? (2)

*Two slightly different definitions

A

The neuronal population that is activated by a specific stimulus.

A co-activated group of neurones which carry information on to the next synapse.

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7
Q

Fill the gaps regarding population coding in the olfactory system. (4)

Information is processed within groups of …………………..
For example, a stimulus will activate a range of different ……………….. which will synapse on …………………………
The neuronal population that is activated by a specific stimulus is called a ………………………..

A

neurones

neurones

a range of second order neurones

neuronal ensemble

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8
Q

Fill the gaps relating to population coding in the olfactory system. (9)

Olfactory sensory neurones lie within the ………………….
They express different ………………….., however each neurone expresses predominantly one type of ……………………. and responds to one particular type of …………………..
All neurones expressing the same receptor types will synapse on the same …………………………. in the ………………………..
However, smells are typically made up of different combinations of molecules and olfactory stimuli. Therefore, smells that humans see as distinct may show some ……………….. with the neurones that are activated.
It is the ……………….. of neurones, also known as the ………………………., which is activated which allows us to distinguish smells.

A

olfactory epithelium

olfactory receptors

receptor

stimulus

glomerulus

olfactory bulb

overlap

combination

neuronal population

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9
Q

True or false? Explain your answer if necessary. (1)

The number of smells that a human can distinguish well exceeds the number of individual sensory neurones.

A

True - this is because it is the combination of neurones activated which encode the stimulus

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10
Q

Fill the gaps relating to population coding in the olfactory system. (2)

Different smells activate different neurones at different …………………….. A certain population of neurones being activated at certain strengths give rise to a …………………..

A

strengths

smell

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11
Q

Name three types of interneurones found in the olfactory bulb. (3)

A

Periglomerular

Lateral projecting

Granule cells

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12
Q

Where in the olfactory bulb are periglomerular interneurones found? (1)

What neurotransmitter do they contain? (1)

A

Around the outside of the glomeruli

GABA

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13
Q

Where in the olfactory bulb are lateral projecting interneurones found? (1)

What neurotransmitter do they contain? (1)

A

connecting different glomeruli

GABA

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14
Q

The glomeruli in the olfactory bulb connect to second order neurones.

Name two types of second order neurone in the olfactory bulb. (2)

A

Tufted cells

Mitral cells

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15
Q

Second order neurones in the olfactory bulb project to which cortical area? (1)

Be specific. (1)

A

Olfactory cortex (piriform cortex)

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16
Q

Fill the gaps relating to population coding in the olfactory system. (3)

Granule cells are ……………….neurones in the ……………………, which modulate activity of ……………………….

A

inter

olfactory bulb

second order neurones

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17
Q

Describe why we get used to smells after a while. I.e. why do we get ‘nose blind’? (4)

A

The brain tries to predict the information going up to it

It sends top-down projections

in an attempt to silence the information coming in

because it doesn’t want too much information coming into the brain at a time

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18
Q

True or false? Explain your answer if necessary. (1)

Some neurones in the olfactory epithelium can respond to more than one smell.

A

True - they tend to express one receptor, but each smell is made up of different molecules so the neurones activated will overlap

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19
Q

What is the missing word? (1)

We only become aware of smells once neurones in the ……………………….. become activated.

A

olfactory cortex

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20
Q

True or false? Explain your answer if necessary. (1)

Some neurones overlap with how they are activated, however it is the population, not individual neurones, that help us to distinguish smells.

A

True

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21
Q

Describe how the olfactory system can differentiate between the concentrations of odours in the environment. (6)

A

An odour activates multiple neurones

they travel to the piriform cortex and activate different cortical neurones

they can also converge to weakly activate the same neurone

if the concentration of an odour is low the primary neurones may be activated at slightly different times so APs won’t converge/summate and activate the piriform cortex neurone

if the concentration of an odour is high the primary neurones will be activated very strongly and quickly so the EPSPs are summated on the cortical neurone and activate it

activity on the shared cortical neurone may help to encode odour strength

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22
Q

Describe how the brain is able to differentiate between different types of touch stimuli. (5)

A
  • Different touch stimuli will preferentially activate different types of peripheral primary afferent fibre in different ways (strongly or weakly)
  • So different populations of neurones in the spinal dorsal horn will be activated (both projection and interneurones)
  • The brain (thalamus) then receives different patterns of activity from this neuronal population
  • A population of neurones in the thalamus is activated
  • And this population will project to the somatosensory cortex
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23
Q

Fill the gaps related to population coding in the dorsal horn. (4)

Sensory stimuli activate multiple ……………………. that will give rise to a sensory signal. This sensory signal activates numerous ………………. and ……………………. in the spinal cord.

The signals generated arrive at the spinal cord with a ………………….. pattern, which is an important component to the overall neural code.

A

fibre types

second order neurones

interneurones

temporal

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24
Q

Give three factors or qualities of the neural code that hold the key to population coding and deciphering a particular stimulus. (3)

A

Intensity of activation

Spatial pattern of activation

Timing of activation

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25
Q

Fill the gaps relating to information processing in the spinal cord. (7)

Each low threshold mechanoreceptor subtype displays unique …………………….. patterns and ………………… distributions.

Within sensory columns mapping to particular regions of skin, LTMR inputs converge onto ………………………

These units, also known as ………………….. represent the first sites of sensory information processing.

The ………………….. is the key initial locus of LTMR and nociceptor stimulus representation, integration, and processing of ensemble activity patterns.

The …………………… is then passed up the hierarchy to the next sensory processing centre (usually the …………………..).

A

central branching

collateral

iterative units

neural ensembles

dorsal horn

neural code

thalamus

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26
Q

Fill the gaps relating to information processing in the spinal cord. (8)

All distinct LTMR fibre types have unique ………………….. properties, …………………… thresholds, ……………………. velocities, …………………… patterns, and ……………………. kinetics. They all converge onto the ……………………..

This convergence of LTMR inputs occurs in a ……………topic, ……………….. manner, and these columns are likely to be key loci of LTMR integration and processing.

A

tuning

excitation

conduction

spike

adaptation

dorsal horn

somato

columnar

27
Q

Low threshold mechanoreceptors principally use which fast neurotransmitter? (1)

A

Glutamate

28
Q

Synaptic arrangements between LTMR subtypes, their postsynaptic targets, and interneurones, often form which complex structures in the spinal cord? (1)

A

Synaptic glomeruli

29
Q

Give three types of fibre endings that are contained in synaptic glomeruli in the spinal cord. (3)

A

Primary afferent axonal boutons

Postsynaptic dendrites

Neighbouring interneurones

30
Q

Fill the missing words relating to information processing in the spinal cord. (2)

Synaptic glomeruli feature lots of ………………, all coming in and synapsing onto …………………..

A

inputs

each other

31
Q

Fill the gaps relating to information processing in the spinal cord. (2)

The presence of synaptic glomeruli allows for input …………………. at the very first synapse within the dorsal horn, and is thus thought to be the anatomical substrate for ……………………………

A

modulation

primary afferent presynaptic modulation

32
Q

Are interneurones in the dorsal horn excitatory or inhibitory? (1)

A

Can be either

33
Q

True or false? Explain your answer if necessary. (1)

Interneurones in the dorsal horn do not receive inputs from primary afferent fibres, and they are not known to modulate the neural code.

A

False - PAFs synapse on different interneurones and these interneurones WILL modulate the neural code

34
Q

Give three possible ways that dorsal horn interneurones can be classified neurochemically. (3)

A
  • By neurotransmitter
  • By neuropeptide
  • By calcium-binding protein expression
35
Q

In which lamina/e of the dorsal horn are PKCy+ interneurones concentrated? (1)

A

Lamina II and III

36
Q

Give four different firing patterns which can occur in dorsal horn interneurones. (4)

A
  • Tonic
  • Phasic
  • Delayed-onset
  • Single-spike
37
Q

Spiking pattern variability in dorsal horn interneurones is significant in what way? What do spiking patterns represent? (1)

A

Reflect differences in the processing of tactile sensory information by these interneurones.

38
Q

Which interneurones in the dorsal horn represent the spatial code of incoming information? (2)

A

Tonic

Delayed-onset

39
Q

What are the proposed roles of tonic and delayed-onset interneurones in the dorsal horn? (2)

A

Integrators of sensory information

that detect which primary afferent fibres are actively releasing neurotransmitters.

40
Q

Which interneurones in the dorsal horn represent the temporal code of incoming information? (2)

A

Phasic

Single-spike

41
Q

What are the proposed roles of phasic and single-spike interneurones in the dorsal horn? (2)

A

Act as coincidence detectors

which recognise the co-occurrence of temporally close but spatially distributed input signals (interpret the timing of inputs)

42
Q

Name two types of glial cells which may play a role in information processing in the spinal cord. (2)

A

Astrocytes

Microglia

43
Q

Fill the gaps relating to information processing in the spinal cord. (3)

Surrounding every synapse are ……………………, which are able to regulate the ……………….. of neurones. ……………….. cells also play a role in this.

A

astrocytic end feet

excitability

microglial

44
Q

Name two roles of glia that allow them to regulate the excitability of neurones. (2)

A

Glutamate buffering

Synaptic scaling

45
Q

Describe how glia are involved in glutamate buffering when modulating the excitability of neurones. (4)

A
  • Astrocytic end feet surround synapses
  • Synaptic glutamate taken up by astrocytes
  • Converted to glutamine
  • Glutamine transferred to neurones to be recycled to glutamate again
46
Q

Describe the process of how glial cells are involved in synaptic scaling. (4)

A
  • Microglia and astrocytes release substances such as TNFa
  • TNFa can activate intracellular signalling cascades
  • Which can increase AMPA receptors
  • And strengthen synapses
47
Q

Describe what is meant by ‘synaptic scaling’. (2)

A

A homeostatic mechanism

for example synaptic strengthening if activity is too low.

48
Q

Which two neurotransmitters are largely released by descending pathways into the spinal cord? (2)

A

Noradrenaline

Serotonin

49
Q

Describe the actions of NA and 5HT, released by descending pathways, in the spinal cord. (3)

A

Act on GABAergic and enkephalin-containing interneurones

to indirectly modulate primary afferent and secondary projection neuronal excitability

and thus alter the neural code projected up to higher centres of the pain processing pathway.

50
Q

Descending modulatory systems release neurotransmitters onto interneurones in the spinal cord.

What two neurotransmitters are these interneurones likely to contain? (2)

A

GABA

Enkephalin

51
Q

Name three elements of the CNS that can alter the neural code produced in dorsal horn projection neurones (not peripheral input). (3)

A

Interneurones

Glial cells

Descending pathways

52
Q

Give two examples of drug types which can target descending pathways projecting to the dorsal horn. (2)

Describe the effects of these drugs. (4)

A

Serotonin reuptake inhibitors

Noradrenaline reuptake inhibitors

  • Potentiate effects of 5HT and NA in spinal cord
  • Therefore, more activation of GABA and enkephalin-containing interneurones
  • So less activation of second order projection neurones
  • And alteration of neural code projecting to brain
53
Q

Describe how population coding can result in allodynia during inflammation. (4)

A
  • Inflammation changes properties of primary afferent fibres (peripheral sensitisation)
  • So a touch stimulus results in a different activation pattern in primary afferent fibres
  • The PAFs then activate a slightly different population of cells in the dorsal horn
  • So there is a different neural code in spinal cord (which may signal pain)
54
Q

Fill in the gaps relating to neural coding of sensory stimuli. (4)

The first neural code produced in PAFs is transformed in the ………………………. via ……………….. synapses.
The code is then further transformed in the …………………… At each step, neuronal activity has to be changed into a ………………., then back into neuronal activity.

A

spinal cord dorsal horn

chemical

thalamus

chemical signal

55
Q

Describe how neural coding of noxious and innocuous stimuli differs. (3)

A
  • Different pattern of primary afferent fibres activated
  • Different neural codes produced in spinal cord
  • Different neural codes transferred to brain
56
Q

Describe how maladaptive plasticity, or central sensitisation in the spinal cord may result in an innocuous stimulus being misinterpreted as pain (allodynia). (5)

A

Misrepresentation of neural code as it is being transformed

due to altered connections and synaptic strengths in the spinal cord

eg. neurones may become more excitable

which disrupts and changes the normal neural code for that stimulus

and the new neural code may resemble a ‘painful’ stimulus, so is misinterpreted as noxious

57
Q

Name three theories of neural coding. (3)

A
  • Intensity theory
  • Specificity theory
  • Combinatorial theory
58
Q

What is the intensity theory of neural coding? (2)

A

Pain is caused by sufficiently strong activation of unspecialised neurones.

This could be any primary afferent fibre as this theory states that they do not have specific roles.

59
Q

What is the specificity theory of neural coding? (2)

What is another name for this theory? (1)

A
  • Specialised high threshold neurones respond to noxious stimuli
  • It is these neurones’ activation that causes pain

Also called the labelled line principle.

60
Q

Give one drawback of the specificity (labelled lines) theory of neural coding. (1)

A

It is too simple to fully explain what is occurring at the level of the spinal cord.

61
Q

Describe the combinatorial theory of neural coding. (4)

A
  • Noxious stimuli activate high threshold nociceptors, and their activation is involved in evoking pain
  • however the stimulus can also activate other primary afferent fibres such as low threshold neurones
  • because the central pathways carrying these signals interact
  • pain will depend jointly on high threshold neurone and low threshold neurone activation levels
62
Q

Give an example of a type of combinatorial neural coding. (1)

How does this type of processing work? (3)

A

Opponent processing

The HThN synapses onto a second order neurone

The LThN synapses onto its own second order neurone and also a GABAergic interneurone

This interneurone stimulates GABA release onto the HThN’s second order interneurone to inhibit it

63
Q

Describe the thermal grill illusion. (5)

A

Alternating warm and cool stimuli very close to one another

So cool and warm neurones are activated very close together on the skin

And they project to the same neuronal ensemble in the spinal cord and partake in opponency processing (cancel each other out)

However cold neurones are also weakly activated in other areas

and these are not cancelled out so cause a burning pain sensation

64
Q

True or false? Explain your answer if necessary. (1)

In the context of the thermal grill illusion, a warm stimulus will only activate hot nerve fibres, however cold and cool stimuli separately will activate both cold and cool nerve fibres.

A

True

Neuroscience Y3S1 (7 decks)

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