Introduction to Consciousness Flashcards

1
Q

What is consciousness?

A

Processes that enable us to experience the world around us

This is distinct from automatic behaviours that occur in a rather unconscious manner

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2
Q

What structure within the brain is heavily involved in regulatingalertness?

A

Reticular Activating System

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3
Q

What is the reticular formation?

A

A core of grey matter passing through the midbrain, pons and uppermedulla – it is a polysynaptic network that regulates the activity of the cerebral cortex

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4
Q

What are the sensory inputs to the reticular formation?

A

Sensory and pain from ascending pathways
Vestibular information from medial vestibular nucleus
Visual from superior colliculus
Auditory from inferior colliculus
Olfactory via the median forebrain bundle

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5
Q

The RF modulates cerebral activity via various projections. Whatare these projections?

A

Noadrenergic projections from the nucleus coeruleus to the cerebral cortex
Dopaminergic projections from the ventral tegmental area to the cerebral cortex
Cholinergic projections to the thalamus
Raphe nuclei in the midline – main source of serotoninergic projections to the brain and spinal cord

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6
Q

Which of these projections is most important in regulating the level of arousal?

A

Cholinergic projections

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7
Q

What are the three mechanisms by which these projections regulate the level of arousal?

A

Excitation of individual thalamic relay nuclei –> activation of cortex
Projections to intralaminar nuclei –> project to all areas of cortex
Projections to reticular nucleus– regulates flow of information through other thalamic nuclei to the cortex

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8
Q

What are the different waveforms seen on an EEG and what levels of arousal do they represent?

A

Delta (< 4 Hz) – seen in sleep
Theta (4-8 Hz) – drowsiness
Alpha (8-13 Hz) – subject relaxed with eyes closed
Beta (13-30 Hz) – mental activity and attention
Gamma range (~40 Hz) – creation of conscious contents in the focus of the mind’s eye, via the recurrent thalamo-cortical feedback

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9
Q

What is a cerebral contusion?

A

Localised bleeding in the brain (bruise in the brain)

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10
Q

What is a concussion?

A

Diffuse, widespread, homogenous impairment of brain tissue due tobrain trauma

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11
Q

What is acute confusion/delirium and stupor?

A

Acute confusion and delirium– sustained disturbance of consciousness where mental processes are slowed. Subject may be inattentive, disorientated and having difficulty carrying out simple commands or speaking
Stupor– lack of critical cognitive function and consciousness – only responsive to pain

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12
Q

Damage to the reticular formation can lead to coma. What is a coma?

A

State of unconsciousness in which the subject cannot be roused even by strong sensory stimuli
Different from sleep – metabolic activity of the brain is depressed and there is total amnesia for this period

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13
Q

State some causes of coma.

A

Metabolic alteration e.g. hypoglycaemia, hypoxia, intoxication
Bilateral lesions in the cerebral hemispheres
Lesions in the thalamus or brainstem

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14
Q

Describe how the Glasgow Coma Scale is structured.

A

Eye opening = 4
Verbal responses = 5
Motor responses = 6

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15
Q

What causes a persistent vegetative state?

A

Disconnection of the brainstem from the cortex or widespread cortical damage
Brainstem is still functioning so reflexes, postural movements and sleep-wake cycle may still be present

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16
Q

What is brain death?

A

Irreversible coma due to brainstem death, but body kept alive artificially
NOTE: spinal reflexes and some postural movements may be present

17
Q

What would the consequences of a right parietal lesion be?

A

Hemispatial neglect – the patient will not pay attention to the left visual field
Information from the left visual field is reaching the primary visual cortex but because of the parietal damage, the patient is not conscious of this visual field

18
Q

What imaging technique can be used to study consciousness in health and disease?

A

Functional MRI

19
Q

What is blindsight?

A

Brain-damaged (occipito-visual cortex) patients who are perceptually blind of their visual field can demonstrate some responses to visual stimuli e.g. manually interacting with ‘unseen’ objects and avoiding ‘unseen’ objects