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Year 2 - neuroscience > Consciousness > Flashcards

Consciousness Flashcards

1
Q

What is consciousness?

A
  • The subjective experience of the mind and the world around us
  • To be in the state of the subjective or first-person point of view
  • The state of being aware of and responsive to one’s surroundings
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2
Q

What are the elements of consciousness?

A

The level of consciousness: are you drowsy? Are you wide-awake?

The content of consciousness: what are you conscious of?

Conscious self: consciousness is associated with some attachment to self

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3
Q

What is vigilance and awareness?

A

VIGILANCE: wakefulness – the level of consciousness in terms of how much your RAS is working. (Awake behaviour e.g looking)

AWARENESS: level and content of consciousness. When you are in a coma, you have a low level of consciousness. A patient in the vegetative state does still have a sleep-wake cycle – nevertheless, the level of awareness is similar to that seen in a coma.

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4
Q

What is the reticular activating system?

A

The RAS is an on/off switch to awakeness

- projects to the thalamus to the cortex from the brainstem

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5
Q

What is the ventral tegmental area and the locus coeruleus?

A
  • Ventral tegmental Area (dopaminergic neurones)
  • Locus coeruleus (noradrenergic neurones)

They are brainstem structures that project widely into the cortex. They regulate activity in the rest of the brain.

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6
Q

Which parts of the brain control consciousness?

A

It is unlikely that there is one brain region that controls consciousness. Consciousness is an emergent property, and arises from the distributed activity of the brain.

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7
Q

What can an fRMI show?

A
  • You can put people into an fMRI scan (you take pictures of blood flow, which is related to neural activity).
  • You can build maps using fMRI – brain regions don’t just act on their own
  • Activities are somewhat coordinated Certain networks become more active during certain tasks.
  • When you are at rest, the default-mode network is more active
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8
Q

What is pertubational complexity index?

A
  • Brain activity is measured in vivo

- Quantifying brain complexity using transcranial magnetic stimulation and EEG – pertubational complexity index (PCI)

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9
Q

How is pertubational complexity index done?

A
  • You get an anaesthetised patient
  • You use transcranial magnetic stimulation to pulse the brain -> this causes resonance of activity
  • This can be measured using EEG
  • In patients who have disorders of consciousness (or people who are asleep/anaesthetised), the response is not as diverse
  • This measure (PCI) tracks conscious level really well
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10
Q

What are neural correlates of consciousness?

A
  • The neural correlates of consciousness (NCC) constitute the minimal set of neuronal events and mechanisms sufficient for a specific conscious perception
  • The minimum neuronal mechanisms jointly sufficient for any one specific conscious experience
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11
Q

What are some disorders of consciousnes?

Describe the awareness and wakefulness of each

A

coma (absent wakefulness/awareness)

vegetative state (wakefulness with absent awareness)

minimally conscious state (wakefulness with minimal awareness)

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12
Q

What is a coma?

A
  • A state of unrousable unresponsiveness lasting more than 6 hrs
  • Person cannot be woken
  • Don’t respond to painful stimuli, light or sound
  • Lack normal sleep/wake cycle
  • Doesn’t initiate voluntary actions
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13
Q

What is a vegetative state?

A
  • Wakeful without being aware
  • Preserved capacity for spontaneous, stimulus induced arousal evidenced by sleep/wake cycle
  • Complete absence of behavioural evidence for self or environmental awareness
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14
Q

What is a minimally conscious state?

A

A state of severely altered consciousness in which minimal self/environmental awareness exists.
- inconsistent but reproducible responses above level of spontaneous/reflexive behavior

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15
Q

What is arousal and awareness?

A

Arousal: the dial on how awake you are

Awareness: about being conscious of something (the content of consciousness)

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16
Q

In normal consciousness, a coma, MCS, vegetative state and locked in syndrome describe the arousal and awareness levels

A

Normal: high arousal and awareness

Coma: low arousal and awareness

Vegetative: high arousal and low awareness

MCS: high arousal, low awareness

Locked in syndrome: high arousal and awareness

17
Q

What happens in brainstem death compared to in vegetative/MCS patients?

A
  • You lose the brainstem drive of respiratory drive, brainstem reflexes and so on
  • People in a vegetative state or patients who are minimally consciousness may need a tracheostomy, but they will still have respiratory drive
18
Q

Where is the brain damage in vegetative patients and those with locked in syndrome?

A

vegetative: destruction of cortex and hemispheres

locked in syndrome: damage to ventral pons

19
Q

How can awareness be tested for in patients with disorders of consciousness?

A
  • Patients in vegetative state put in into an fMRI scanner
  • Patients were asked to answer by nodding yes or shaking. If they did nothing they were classed as having a low level of consciousness
  • When patients underwent fMRI, questions were asked again
  • Instead of nodding yes, patients were told to imagine playing tennis. Instead of shaking no, patients were told to imagine they were walking around their house
  • Brain activity was similar in both patients and controls when you asked the patient to imagine playing tennis/imagine wondering around the house
  • This mechanism was used to allow patients to communicate
20
Q

What is homonymous hemianopia?

A

When you lose half of the visual field, common after stroke.

21
Q

What is neglect?

A

A higher order problem – you lose conscious awareness of one side.

  • If the neglect is on the left side, the patient won’t attend at all to anything on the right side
  • The patient has completely lost awareness of that side
  • Not just a visual issue
22
Q

What are EEGs?

A

EEG measures the electricity on the scalp, that in someway relates to brain activity

  • By counting the frequency of oscillations you can work out speed of activity
  • Oscillations are seen which reflect brain activity
23
Q

During sleep what waves are present and what frequency?

A

Delta

up to 4Hz

24
Q

During normal waking consciousness which waves are present and what frequency?

A

Baet

13-30 Hz

25
Q

Describe what alpha waves are and when are they more/less prominent?
What does an absence suggest?

A
  • Typically a rhythm that you see on the back of the brain, and is related to attention.
  • When you attend to something, the alpha waves go down – they get less prominent
  • When you relax, alpha rhythm is more prominent
  • Absence of alpha waves indicates problems.
26
Q

If a person has problems what will happen to the EEG?

A

it will be slower throughout

27
Q

What is an EEG useful for?

A

epilepsy

28
Q

What are gamma waves associated with and what frequency are they?

A

Associated with creation of conscious contents in the focus of the mind’s eye
- 40 Hz

29
Q

Which waved are present when you are awake and active?

A

beta and gamma

30
Q

How does the EEG compare in REM, nREM and when you are awake?

A
  • The EEG seen in REM sleep is very different to the EEG seen in NREM sleep
  • It doesn’t completely look like when you’re awake – but different to the rest of sleep
31
Q

What is the glasgow coma scale?

A
  • The GCS is a clinical means of assessing something about conscious level
  • It ranges between 3 and 15. 3 could even apply to a dead person in situations. The lower the score, the higher the severity
  • Eyes (4), Voice (5) and Motor (6)
32
Q

GCS - EYES

A

none -1
response to pain -2
response to speech -3
spontaneous -4

33
Q

GCS - VERBAL RESPONSE

A 
none -1
incomprehensible sounds -2
inappropriate words -3
disorientated -4
orientated -5
34
Q

GCS -MOTOR RESPONSE

A 
none -1
extensor response to pain -2
flexor response to pain -3
withdrawal to pain -4
localisation of pain -5
obeys commands -6
35
Q

What are some metabolic causes of coma?

A
  • Drug overdose
  • Hypoglycaemia
  • Diabetes
  • ‘The failures’ – renal, liver etc.
  • Hypercalcaemia
36
Q

What are some diffuse intracranial causes of coma?

A
  • Head injury (trauma)
  • Meningitis
  • SAH (subarachnoid h)
  • Encephalitis
  • Epilepsy
  • Hypoxic brain injury
37
Q

What are some brainstem causes of coma?

A
  • Brainstem infarct
  • Tumour
  • Abscess
  • Cerebellar haemorrhage
  • Cerebella infarct
38
Q

What are some hemispheric causes of coma?

A
  • Cerebral infarct
  • Cerebral haemorrhage (subdural/extradural)
  • Abscess
  • Tumour

Year 2 - neuroscience (13 decks)

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