WEEK 1: CONSCIOUS AND BRAIN ACTIVITY Flashcards
What is consciousness?
A subjective state of wakefulness and being aware of your environment and self-such as private inner world of your mind (thoughts, perceptions, dreams etc)
awareness of yourself and the world,
It is described as sentience, awareness, subjectivity, the ability to experience and feel, wakefulness, having a sense of selfhood and executive control of the mind.
Define the following levels of consciousness
1. Alert
2.Clouding consciousness/ drowsy/lethargic
3.confusion
4.Delirium
5.Stupor
6..Coma
- awake and responsive to external stimuli
2.reduced wakefulness, feel sleepy or fatigued and sluggish.
3.Patient is bewildered or unclear and misinterprets his or her environment.
4.State of confusion, sometimes visual hallucinations
*A temporary mental state characterized by confusion, anxiety, incoherent speech, and hallucinations.
- Sleepy state and aroused by vigorous repetitive stimuli
6.Non arousal and unresponsive (Glasglow coma scale is used in clinical practice)
What is the highest form of consciousness?
Higher states of consciousness are often associated with spiritual or mystical experiences. It involves an elevated state of awareness where people are able to gain a greater sense of themselves, their role, and the world.
List examples of highest form of consciousness
*Meditation
*Mindfulness
*Lucid dreaming
*Flow states
* Transcendence
Outline factors that alter the consciousness mechanisms
- diffuse brain dysfunction
- Generalised metabolic disorders such as alcohol intake, uraemia and septicaemia inhibit brain function
3.Direct effects within the brain - Lesions in thee brainstem affecting the reticular activating system
5.Pressure effects on the brainstem - Lesion in the brain compressing the brain affecting ascending reticular activating system
NOTE: Consciousness is mostly altered by effects on the brainstem, reticular activating system and the cerebral cortex
What is electroencephalography?
The study of electrical activities of the brain
What is electroencephalogram?
The recording of electrical signals of the brain ( Berger waves)
It helps us see a glimpse of the generalized activity of cerebral cortex.
Berger waves of an awake and sleeping individual are different
Outline clinical uses of EEG
*Diagnosis of neurological disorders (epilepsy, stroke)
*Diagnosis of sleep disorders ( disorders of the midbrain affecting ascending reticular activating system
*Subdural hematoma
Briefly describe an EEG work
- Electrodes are placed on the head
- Small voltage fluctuations of microvolts in amplitude are measured between selected pairs of electrodes
- It takes many thousand underlying neurons together to generate an EEG signal big enough to see at all
4.The EEG rhythms vary dramatically and often correlate with particular states of behavior such as level of attentiveness, sleeping or waking and pathology seizures and coma
What is the amplitude of an EEG signal strongly dependent on?
It is dependent on how synchronous the activity of underlying neurons is
Describe the alpha rythms of the brain
- Seen in non-attentive, relaxed or meditating , closed eyes
- It is the hallmark frequency of the normal awake adult brain,
*Marked on the parietal-occipital area - Has a frequency of 8- 12 waves/ second
4.Has a low amplitude of 30-50mv
5.It is abolished by visual stimuli
6.
Describe the beta rhythms of the brain
*Associated with mental activity ( arousal and wakefulness)
*Not affected by eye opening
*Predominant in frontal lobe and precentral gyrus
*Desynchronized
*High frequency 13-60 waves/sec
*Low amplitude 5-10mv
Describe the Theta rythms
*Mostly found in children below 5 years
*Predominant from temporal and occipital lobe
*Indicates emotional stress in adults
*Low frequency 4-8 waves/sec
*Amplitude 10mv
Describe the delta rhythms
*Common in adults during deep sleep
*Common in wakeful children
*Not affected by opening eyes
*Indicated brain damage , increased ICP, epilepsy, depression and mental deficiency when seen in adults outside deep sleep
*Low frequency 1-5 waves/sec
*Low amplitude 20 -200 mv
List Other factors that can influence your EEG reading include:
low blood sugar
bright or flashing lights
some medications, such as sedatives
consuming caffeine
oily hair or hair spray
List factors that could interfere with an EEG reading
Several types of movementsTrusted Source can potentially cause “artifacts” on an EEG recording that mimic brain waves. The person responsible for interpreting your EEG will take these movements into account. They include:
your pulse and heartbeat
breathing
sweating
mouth movements
muscle movements
What is frequency in EEG?
Frequency describes how many waves there are per second, and is measured in hertz (Hz).
There are four main frequencies of the human brain seen on scalp EEG, in increasing order: delta, theta, alpha and beta.
What is the amplitude of a EEG ?
Amplitude is the height of a waveform, essentially a proxy for the voltage, and on the scalp is measured in microvolt
What is the morphology of a waveform?
The morphology of a waveform describes its overall shape, and is important for both interpreting a tracing and communicating your findings.
For an individual waveform, each part of a wave is considered a phase.
Its easiest to think of phases by imaging an imaginary baseline; a monophasic wave begins on one side of the baseline and has only two parts, an up slope and a down slope, and crosses the baseline only once.
An example of a monophonic wave is a simple spike. A biphasic wave starts on one side of the baseline with an up slope and downslope going through the baseline, but then has a second part that crosses the baseline again; the classic epileptiform spike and slow wave discharge is an example of a biphasic wave. Polyphasic waves cross the baseline multiple times.
Describe an EEG for an awake person
;Low voltage, fast EEG, continuous voluntary movement, rapid eye movement
Outline the features of a NREM sleep
No eye movement, slow wave sleep, high (delta waves, no dreams, dull or absent sensation, occasional involuntary movements. occupies 70-80% of sleep, has 4 stages
Describe stage 1 of NREM sleep
*easily aroused , lightest sleep
1.Once eyes closed, relaxation
2.Rapid beta waves
3.Theta waves start to appear
4.There is loss of muscle control( tossing and turning occurs
Stage 1, also called N1, is essentially when a person first falls asleep. This stage normally lasts just one to seven minutes.
During N1 sleep, the body has not fully relaxed, though the body and brain activities start to slow with periods of brief movements. There are light changes in brain activity associated with falling asleep in this stage.
It is easy to wake someone up during this sleep stage, but if a person is not disturbed, they can move quickly into stage 2. As the night unfolds, an uninterrupted sleeper may not spend much more time in stage 1 as they move through further sleep cycles.
Describe stage 2 of NREM sleep
*Light sleep, arousal become difficult
EEG pattern irregular
Theta waves interrupted by Sleep Spindles (high voltage waves generated by interaction between from thalamic & cortical neurons)
High amplitude waves (K-complex) are common
Adult spend 50% of sleeping time.During stage 2, or N2, the body enters a more subdued state including a drop in temperature, relaxed muscles, and slowed breathing and heart rate. At the same time, brain waves show a new pattern and eye movement stops. On the whole, brain activity slows, but there are short bursts of activity
that actually help resist being woken up by external stimuli.
Stage 2 sleep can last for 10 to 25 minutes during the first sleep cycle, and each N2 stage can become longer during the night.
Collectively, a person typically spends about half their sleep time in N2 sleep.
Describe stage 3 of NREM sleep
Stage 3: Moderate Sleep, Slow Wave Sleep (SWS)
*Sleep deepens, lasts 10 minutes of sleep cycle
*Delta and Theta waves common
*Sleep spindles and K complex are less common
*Vital signs decline
Describe stage 4 of NREM sleep
Stage 4: (SWS) Deepest NREM sleep, difficult arousal
*EEG dominated by Delta waves
*Skeletal muscles relaxed, neural activity at its lowest
*Breathing, HR, blood pressure, temperature reduced
*Children may have somnambulism and night terrors
Stage 3 sleep is also known as N3 or deep sleep, and it is harder to wake someone up if they are in this phase. Muscle tone, pulse, and breathing rate decrease in N3 sleep as the body relaxes even further.
The brain activity during this period has an identifiable pattern of what are known as delta waves. For this reason, stage 3 may also be called delta sleep or slow-wave sleep (SWS).
Experts believe that this stage is critical to restorative sleep, allowing for bodily recovery and growth. It may also bolster the immune system and other key bodily processes. Even though brain activity is reduced, there is evidence that deep sleep contributes to insightful thinking, creativity and memory.
You spend the most time in deep sleep during the first half of the night. During the early sleep cycles, N3 stages commonly last for 20 to 40 minutes. As you continue sleeping, these stages get shorter, and more time gets spent in REM sleep instead.
Describe EEG pattern for REM sleep
*Characterized by rapid eye movements
*Begins with a series of PGO waves
*Flat and Desynchronized EEG pattern
*High frequency, low amplitude-BETA WAVES ARE PREDOMINANT
*Accounts for a minority of our sleep time, 20 – 30% of sleeping period
*Resembles an active, waking brain, with fast low voltage fluctuations
*Sleep paralysis
*Dreaming is common
*Arousal is easy
*Heart rate quickens
*Breathing more irregular and rapid
*Brain wave activity resemble wakefulness
*Associated with genital arousal
*The oxygen consumption of the brain is higher in REM sleep than when the brain is awake
Which sleeping stage gets longer as the night progresses?
As the night goes on, REM stages get longer, especially in the second half of the night. While the first REM stage may last only a few minutes, later stages can last for around an hour. In total, REM stages make up around 25% of sleep in adults.
Distinguish between FEM and NREM sleep
REM sleep
* Takes 20-30% of sleep cycle
*Respiratory rate, temperature and heart rate are fluctuating
*There is eye movements
*Dreams
*Muscle twitching
*Irregular, low amplitude high frequency BETA WAVES
NREM sleep
*takes 70-80%
*RR, Temp and HR STABLE
*Dreams, eye movements and muscle twitching ABSENT
*Varying types of waves depending on stage of NREM
Describe an EEG for an awake person.
Low voltage, fast EEG, continuous voluntary movement, rapid eye movement
