U1 L5 Higher Mental Functions & Brain Waves

Normal brain function involves continuous electrical activity.
An electroencephalogram (EEG) records this activity.
Patterns of neuronal electrical activity recorded are called brain waves.
Each person’s brain waves are unique, characterized by a continuous train of peaks and troughs.
Wave frequency is expressed in Hertz (Hz).

Alpha waves: Regular and rhythmic, low-amplitude, slow, synchronous waves indicating an "idling" brain.
Beta waves: Rhythmic, more irregular waves occurring during the awake and mentally alert state.
Theta waves: More irregular than alpha waves; common in children but abnormal in adults.
Delta waves: High-amplitude waves seen in deep sleep and when the reticular activating system is damped.

Encompasses perception of sensation, voluntary initiation and control of movement, and capabilities associated with higher mental processing.
Involves simultaneous activity of large areas of the cerebral cortex.
Is superimposed on other types of neural activity.
Is holistic and totally interconnected.
Clinical consciousness is defined on a continuum that grades levels of behavior: alertness, drowsiness, stupor, coma.

There are two major types of sleep:
- Non-rapid eye movement (NREM)
- Rapid eye movement (REM)
One passes through four stages of NREM during the first 30-45 minutes of sleep.
REM sleep occurs after the fourth NREM stage has been achieved.

NREM stages include:
- Stage 1: Eyes are closed and relaxation begins; the EEG shows alpha waves; one can be easily aroused.
- Stage 2: EEG pattern is irregular with sleep spindles (high-voltage wave bursts); arousal is more difficult.
- Stage 3: Sleep deepens; theta and delta waves appear; vital signs decline; dreaming is common.
- Stage 4: EEG pattern is dominated by delta waves; skeletal muscles are relaxed; arousal is difficult.

Characteristics of REM sleep:
- EEG pattern reverts through the NREM stages to the stage 1 pattern.
- Vital signs increase.
- Skeletal muscles (except ocular muscles) are inhibited.
- Most dreaming takes place.

Alternating cycles of sleep and wakefulness reflect a natural circadian rhythm.
Although RAS activity declines in sleep, sleep is more than turning off RAS.
The brain is actively guided into sleep.
The suprachiasmatic and preoptic nuclei of the hypothalamus regulate the sleep cycle.
A typical sleep pattern alternates between REM and NREM sleep.

Slow-wave sleep is presumed to be the restorative stage.
Those deprived of REM sleep become moody and depressed.
REM sleep may be a reverse learning process where superfluous information is purged from the brain.
Daily sleep requirements decline with age.

Narcolepsy: Lapsing abruptly into sleep from the awake state.
Insomnia: Chronic inability to obtain the amount or quality of sleep needed.
Sleep apnea: Temporary cessation of breathing during sleep.

Is active when we are awake. They produce Nor that causes “fight –or-flight” response.
Is inactive when we are sleeping. No motor activity results from cortical stimuli because they are prevented from reaching the spinal cord.

Memory is the storage and retrieval of information.
The three principles of memory are:
- Storage – occurs in stages and is continually changing
- Processing – accomplished by the hippocampus and surrounding structures
- Memory traces – chemical or structural changes that encode memory

The two stages of memory are short-term memory and long-term memory.
Short-term memory (STM, or working memory): A fleeting memory of the events that continually happen.
- STM lasts seconds to hours and is limited to 7 or 8 pieces of information.
Long-term memory (LTM) has limitless capacity.

Factors that affect transfer of memory from STM to LTM include:
- Emotional state: We learn best when we are alert, motivated, and aroused.
- Rehearsal: Repeating or rehearsing material enhances memory.
- Association: Associating new information with old memories in LTM enhances memory.
- Automatic memory: Subconscious information stored in LTM.