Consciousness and Sleep

Electroencephalogram (EEG)

• Measures electrical activity of neurons closest to scalp: gray matter of cortex
• Reflects mental states: relaxed, alert, seizure...
• Frequency of wave = level of responsiveness
• Fast frequency = more alert
• Amplitude of wave = synchronous activity

Stages of Sleep

• Stages 1 - 4: called Non-REM (NREM) sleep
• REM sleep is also called paradoxical sleep, because it is characterized by the brain activity observed during waking (theta and beta activity).
• REM sleep is also characterized by rapid eye movement (REM), increased heart rate and respiration, reduced muscle tone, and dreaming.
• Types of waves: beta, alpha, theta and delta
• Beta --> awake and alert (low amplitude, fast frequency)
• Alpha --> awake but relaxed (slow frequency)

• Non-REM and REM sleep periods alternate, and the percentage of time spent in REM sleep progressively increases over the nocturnal sleep period.

States of Consciousness

• Structures involved: hypothalamus and reticular activating system
• Parts of reticular activating system:
• Increase norepinephrine and serotonin when awake (aminergic neurons)
• Decrease acetylcholine when awake (cholinergic neurons)

• Hypothalamus (plus other centers):
• Decreases GABA when awake
• Increases histamine when awake
• Leads to increased activity of the thalamus and cortex

(Mesolimbic) Dopamine Pathway

• Main reward pathway
• Starts in reticular activating system --> Midbrain --> Prefrontal cortex
• Amphetamines cause release of dopamine
• Most psychoactive drugs act here

Limbic System

• Deals with instinct and mood
• Basic emotions: fear, pleasure, anger
• Drives: hunger, sex, dominance, care of offspring

Memory and Learning

• Hippocampus is a major structure in memory acquisition
• Declarative memory: facts and events that can be recalled
• Procedural memory: how to do things, motor skills
• Consolidation: stabilizing the memory after initial acquisition (from short to long term)

Language Areas

• Broca's Area: language articulation
• Think that you were reading an article about someone's brain being broken!
• Wernicke's Area: language comprehension