EEG Waves Flashcards
What creates the EEG?
Summated action potentials of millions of neurons in the brain
General Features of EEG:
- Low voltage (<200 mµV)
- Frequency: <1 Hz –> >50 Hz
- Differs over different parts of brain
- Usually no distinct pattern
The EEG Changes with:
- Degree of activity in the brain
- Arousal/awareness
- Sensory input (esp visual)
What are the 5 waves found in the EEG?
- Alpha
- Beta
- Gamma
- Theta
- Delta
Characteristics of Alpha Waves
- Frequency: 8-13 Hz (cycles/sec)
- Amplitude: 50 µVolts (size of wave)
- High frequency, low amplitude
When do Alpha Waves occur?
- During quiet wakefulness (thinking) with eyes closed
- Disappear during sleep
Area of the brain where
Alpha waves are most prevalent:
Occipital Cortex
Origin of Alpha Waves
- Requires connection between thalamus and cortex
- GABAergic neurons “force” coordination of neuronal activity
Alpha Wave Pathway
Thalamocortical Neurons –> Release EAA –> Activation of Intracortical (GABAergic) Neurons –> Release GABA –> inhibition
Characteristics of Beta Waves
- Frequency: 14 - 80 (cycles/sec)
- Amplitude: <50 µVolts
- High frequency, low amplitude
When do Beta Waves occur?
During alert wakefulness with EYES OPEN
Alerting Response
(1) Sensory input (opening eyes)
(2) Transition from alpha to beta waves
(3) Beta waves persist as long as alert
(4) Transition to alpha waves when eyes close again
Areas of the brain where Beta Waves are most prevalent:
Frontal Cortex; also parietal cortex
Origin of Beta Waves
- Requires connection between thalamus and cortex
- Sensory input from eyes “disrupts” the oscillation of waves
Characteristics of Gamma Waves
- Frequency: 30-80 Hz (frequently overlaps with range of Beta waves)
- May require Hippocampus
When do Gamma Waves occur?
- When individual is aroused or focused on something
- Especially prominent when planning a motor response
Characteristics of Theta Waves
- Frequency: 4-7 Hz
- Amplitude: 100 µVolts
- Slower frequency, higher amplitude
When do Theta Waves occur?
- Normal in children, particularly over parietal and frontal cortex
- May occur in adults when frustrated or disappointed; also occurs during sleep
What brain structure is required/involved in production of Theta Waves?
Hippocampus
Characteristics of Delta Waves
- Frequency: <3.5 Hz
- Amplitude: 100-200 µVolts
- Slowest and largest
When do Delta Waves occur?
- During deep sleep in adults
- Common in infants and can be seen while awake
- Appear during “wakefulness” sign of serious organic brain disease
Origin of Delta Waves
- Does not require connection between thalamus and cortex – cortex is running on its own
- Indicates that thalamus and cortex are no longer connected
Increased mental/neural activity is associated with ____ activity on the EEG
Increased
Mental activity leads to a ____ of activity, associated with ____ amplitudes and ____ frequency of the waves.
- Desynchronization
- Reduced
- Higher
In general, infants have ___ and ___ waves on EEG (___-like waves) especially over occipital regions, when they are awake.
- Slower and bigger
- Beta
When does the adult alpha-wave pattern appear?
Adolescence
Reduced metabolism leads to ____ neuronal activity.
Reduced
What decreases the frequency of the alpha rhythm?
- Hypoglycemia
- Low body temperature (hypothermia)
- Low adrenal glucocorticoids (low cortisol)
- High levels of CO2 in the blood (CO2 acts as a narcotic)
Non-REM Sleep
- Timing: majority of sleep
- Eye movements: slow, rolling motion
- EEG: gradually slows and increases in amplitude (moves to Delta waves)
- Dreams do occur during this time but they are generally rehashing events of the day
- Initial phases of memory consolidation occur during this time
REM Sleep
- Rapid Eye Movement
- Timing: approx every 90 mins, gets longer the later in the sleep period
- Eye movements: rapid, left to right
- EEG: low amplitude, high frequency (look most similar to the waves during wakefulness)
- Associated with vivid dreams that you remember; continued consolidation, linking knowledge to previous experience
