Consciousness: Biological and Cognitive Perspectives – Study Notes

Consciousness

Definition and Continuum

Consciousness refers to our awareness of ourselves and our environment. It exists on a continuum, ranging from full alertness to deep sleep, and includes various states with differing levels of sensory awareness and cognitive activity.

• Sleep: A state marked by low levels of physical activity and reduced sensory awareness.

• Wakefulness: Characterized by high levels of sensory awareness, thought, and behaviour.

• Other States: Includes daydreaming, intoxication, and unconsciousness due to anaesthesia.

Example: Lucid dreaming is a state where a person is aware they are dreaming and may exert control over the dream.

State	Awareness	Wakefulness
Conscious Wakefulness	High	High
Light Sleep	Moderate	Low
Deep Sleep	Low	Very Low
Coma	Minimal	Minimal
Vegetative State	Minimal	Minimal

Attention & Vigilance

Types of Attention

Attention is the process by which we focus on certain stimuli in our environment. Vigilance refers to the capacity to maintain attention and alertness over extended periods.

• Sustained Attention (Vigilance): Staying focused on one task for a long time.

• Divided Attention: Focusing on many things at once.

• Spatial Attention: Focusing on one part of our environment and then shifting our focus to other parts.

• Selective Attention: Choosing specific things in our environment to focus on, while ignoring others.

Example: Listening to a lecture while ignoring background noise demonstrates selective attention.

Factors Impacting Vigilance

• Unexpected Distractions: Sudden changes in the environment can disrupt attention.

• Vigilance Decrement: Over time, the ability to maintain vigilance tends to decrease.

• Psychophysiological Factors: Fatigue, boredom, stress, and individual differences affect vigilance.

• Environmental and Task Influences: Task complexity can impact the ability to sustain attention.

Biological Rhythms

Types of Biological Rhythms

Biological rhythms are internal cycles of activity that occur within the body and are crucial for regulating changes in consciousness.

• Menstrual Cycle: Ranges from 21 to 35 days in adults.

• Circadian Rhythm: A natural cycle that lasts about 24 hours, regulating sleep-wake cycles and other bodily functions.

Example: Body temperature fluctuates cyclically over a 24-hour period, peaking in the afternoon and dropping during sleep.

Rhythm	Duration	Example
Menstrual Cycle	21-35 days	Hormonal changes in females
Circadian Rhythm	~24 hours	Sleep-wake cycle, body temperature

Suprachiasmatic Nucleus (SCN) and Melatonin

The suprachiasmatic nucleus (SCN) is a specific area within the hypothalamus that acts as the brain's clock. It synchronizes the body's internal clock with the external environment through the release of melatonin, a hormone that induces sleepiness.

• Light Exposure: Regulates melatonin production and helps maintain circadian rhythms.

• Disruptions: Jet lag and shift work can cause the internal clock to fall out of sync with the outside world.

Example: Traveling across time zones can disrupt the circadian rhythm, leading to jet lag.

Sleep

Definition and Regulation

Sleep is distinguished by low levels of physical activity and reduced sensory awareness. Sleep-wake cycles are controlled by multiple brain areas, including the thalamus, hypothalamus, and pons.

• Hormones Involved: Melatonin, follicle stimulating hormone (FSH), luteinising hormone (LH), and growth hormone.

Example: Melatonin levels rise in the evening, promoting sleepiness.

Functions of Sleep

Sleep is essential for cognitive function and memory formation, including maintaining attention, making decisions, and recalling long-term memories. Impairments become more severe as the amount of sleep deprivation increases.

• Benefits: Enhances creative thinking, language learning, and inferential judgements.

• Consequences of Deprivation: Impaired immune system, increased risk of heart disease, diabetes, and decreased cognitive performance.

Function	Impact of Sleep Deprivation
Cognitive Function	Decreased attention, memory, decision-making
Physical Health	Increased risk of disease, impaired immunity

Stages of Sleep

Brain Waves and Sleep Stages

Different phases of sleep can be differentiated using electroencephalography (EEG), which measures brain wave activity.

• Alpha Waves (8–13 Hz): Present when a person is relaxed and awake, but not actively processing information.

• Theta Waves (4–7 Hz): Represent a state of light sleep or drowsiness, where a person can be easily awakened.

• Delta Waves (>3 Hz): Slowest and highest amplitude brain waves, characteristic of deep, restorative sleep.

Example: During deep sleep, delta waves dominate the EEG recording.

K-Complexes and Sleep Spindles

• K-complexes: Singular, high amplitude waves that represent a mechanism for maintaining sleep in the presence of external stimuli and aiding in sleep-based memory consolidation.

• Sleep Spindles: Bursts of rapid, rhythmic brain activity that play a role in integrating and processing memories and information learned throughout the day.

Example: Sleep spindles are prominent during Stage 2 sleep and are associated with learning and memory consolidation.

Summary Table: Sleep Stages and Brain Waves

Stage	Dominant Brain Waves	Characteristics
Awake	Beta, Alpha	Alert, relaxed
Stage 1 (NREM)	Theta	Light sleep, easy to awaken
Stage 2 (NREM)	Theta, Sleep Spindles, K-complexes	Deeper sleep, memory consolidation
Stage 3 (NREM)	Delta	Deep, restorative sleep
REM	Mixed, similar to awake	Dreaming, muscle paralysis

Key Equations

• $\text{Alpha Waves: } 8-13\ \text{Hz}$

• $\text{Theta Waves: } 4-7\ \text{Hz}$

• $\text{Delta Waves: } < 3\ \text{Hz}$

Additional info: These notes expand on the provided slides by including definitions, examples, and tables for clarity and exam preparation.