Introduction to Consciousness Flashcards
What is consciousness?
Processes that enable us to experience the world around us
Distinct from automatic behaviours that occur in a rather unconscious manner
What structure within the brain is heavily involved in regulating alertness?
Reticular Activating System
What is the reticular formation?
A core of grey matter passing through the midbrain, pons + upper medulla– it is a polysynaptic network that regulates activity of the cerebral cortex
What are the sensory inputs to the reticular formation?
Sensory + pain from ascending pathways
Vestibular information from medial vestibular nucleus
Visual from superior colliculus
Auditory from inferior colliculus
Olfactory via the median forebrain bundle
The RF modulates cerebral activity via various projections. What are these projections?
Noradrenergic projections from the Locus coeruleus (Pons) to the cerebral cortex
Dopaminergic projections from the ventral tegmental area (midbrain) to the cerebral cortex
What are the different waveforms seen on an EEG and what levels of arousal do they represent?
Delta (< 4 Hz): Sleep
Theta (4-8 Hz): Drowsiness
Alpha (8-13 Hz): Subject relaxed with eyes closed
Beta (13-30 Hz): Mental activity + attention
Gamma range (~40 Hz): creation of conscious contents in the focus of the mind’s eye, via the recurrent thalamo-cortical feedback
What is a coma?
Absent wakefulness + absent awareness
Unrousable unresponsiveness
Cant be awakened, no normal sleep-wake cycle
No initiation of voluntary actions
State 4 causes of coma.
Metabolic alteration e.g. hypoglycaemia
Diffuse intracranial e.g. epilepsy
Hemisphere lesion e.g. cerebral haemorrhage, tumour
Brainstem e.g. brainstem infarct, tumour, abscess
Describe how the Glasgow Coma Scale is structured.
Eye opening = 4
Verbal responses = 5
Motor responses = 6
What would the consequences of a right parietal lesion be?
Hemispatial neglect: patient will not pay attention to left visual field
Info. from left visual field is reaching primary visual cortex but because of the parietal damage, patient is not conscious of this visual field
E.g. Eat a meal, only eat half of what is on plate
What imaging technique can be used to study consciousness in health and disease?
Functional MRI
Describe the dynamics of neuronal activity
Integration: brain activity over time is collectively correlated
Differentiation: different parts of brain must be doing different things to account for the range of occurrences in our experiences
Is there a single brain region for consciousness?
No, there are brain networks (groups of regions that function together)
Which brain network is considered important for consciousness?
Default mode network
What does the perturbational complexity index illustrate?
Complexity of brain activity
Complex: high level of consciousness
Low complexity: low level of consciousness
