Motivation Week 3

Motivation PSYC 2230

Chapter 3: Physiological Mechanisms of Arousal

Arousal Theory

Arousal theory presents motivation through a continuum of behavioral activation, ranging between low and high arousal. The extreme ends of this continuum can be conceptualized as follows:

  • Low Arousal: Coma and Sleep

  • High Arousal: Waking, Alertness to Stress

Yerkes-Dodson Law

The Yerkes-Dodson Law describes an inverted U-shaped relationship between arousal and performance. According to this principle, there is an optimal level of arousal for performance, which does not apply uniformly to all behaviors, indicating that the relationship is more complicated than a simple peak performance at medium arousal.

Neural Structures & Arousal Theory

The studies by Bremer in 1937 explored the neural structures involved in arousal.

  • Encephale Isole: This procedure involved cutting through the brain stem between the medulla and spinal cord, which resulted in normal sleep-wake cycles.

  • Cerveau Isole: Another procedure involved cutting through the brain stem at the colliculi, leading to the subject remaining asleep without spontaneously waking.

  • It was concluded that brain structures situated between these two cuts are integral in regulating arousal levels for waking and sleeping.

  • Notably, the pons is responsible for controlling the sleep-wake cycle, breathing, and other unconscious processes.

The Reticular Activating System (RAS)

Research by Moruzzi and Magoun in 1949 identified the RAS, a collection of nerve cells located in the central brain stem stretching from the medulla through to the thalamus.

  • Electrical stimulation of the RAS leads to changes in EEG patterns, which mirror those observed when external stimuli are acknowledged, evidencing its role in attention.

What does EEG tell us?

  1. The RAS gathers input from external sensory environments.

  2. Severing the RAS eradicates the sleep-wake cycle.

  3. The RAS extends projections to the rest of the cortex, influencing overall arousal levels.

Hebb’s Theory & Lacey’s Model
Hebb’s Theory

Hebb posits that sensory information serves two primary functions:

  1. Cue Function: Provides necessary information concerning the environment.

  2. Arousal Function: Activates the individual in response to sensory input.

Lacey’s Model

Lacey expanded on this by defining arousal as a multidimensional construct encompassing:

  1. A behavioral response exhibited by an organism.

  2. Desynchronized brain activity.

  3. The presence of fast brain wave patterns.

  • It is emphasized that peripheral body sensory information significantly influences arousal levels.

Problems with Arousal Theory

Several limitations have been identified within arousal theory:

  1. There exists a lack of a consistent relationship between behavioral, cortical, and autonomic measures of arousal.

  2. Various patterns of bodily response to arousal have not been conclusively shown, although differences in autonomic responses have been documented for certain emotions.

  3. A correlation between EEG activity and motivational state lacks clarity.

  4. The physiological mechanisms alone do not encompass the full scope of motivation; environmental factors and an organism's history also play crucial roles.

Learning Check 1

  1. According to the inverted-U function, performance:

    • A. peaks at some mid-range level of arousal

    • B. peaks at low levels of arousal, only

    • C. peaks at high levels of arousal, only

    • D. is not related to arousal level

Sleep
Circadian Rhythms

Circadian rhythms are biological processes that follow a 24-hour cycle. Dement suggests these rhythms prompt sleep when individuals are least efficient, whereas Webb and Agnew argue that they induce sleep during unnecessary and potentially dangerous awake periods.

Two Processes Controlling Sleep

  1. Homeostatic Process: This process increases the duration of sleep based on the length of wakefulness.

  2. Circadian Process: This process regulates wake-up times.

Variation in Sleep Patterns

  • Sleep durations vary across species and among human age groups.

    • Prey species tend to have shorter sleep durations compared to predators.

    • Human sleep duration tends to decrease with age, leading to increased nighttime awakenings or insomnia.

    • There is a noted decline in sleep stages 3 and 4, especially in older males.

Sleep Stages

The sleep cycle consists of different stages, classified as follows:

  • Stage 1: Characterized by theta wave activity (3.5-7.5 Hz), constituting approximately 5% of total sleep time.

  • Stage 2: Contains sleep spindles and K-complexes, making up about 50% of sleep time.

  • Stage 3: Delta waves occur 20-50% of the time, constituting around 6% of sleep time.

  • Stage 4: Presenting high-frequency delta waves over 50% of the time, comprising about 14% of sleep time.

  • Stage 5 (REM sleep): Encompasses a mixture of theta, beta, and alpha waves; muscle tone is minimal, eyes exhibit rapid movement, and dreaming occurs. This stage makes up approximately 25% of sleep time, with episodes lasting between 10-45 minutes each time one falls asleep.

Dreams
Domhoff’s Neurocognitive Theory of Dreams

According to Domhoff, dreaming constitutes a developmental cognitive achievement characterized by:

  1. Continuity Principle: The idea that daily concerns manifest in dreams.

  2. Repetition Principle: Similar themes and elements can recur in dreams over decades.

Revonsuo’s Threat Simulation Theory

This theory posits that dreaming serves to simulate threatening events, with evidence suggesting that dreams often portray negative scenarios, with aggression being the most common behavior exhibited.

Franklin & Zyphur’s Expansion of Renonsuo’s Theory

They propose that dreams serve additional cognitive roles, acting as a virtual rehearsal mechanism essential for developing human cognitive capabilities beyond just processing threatening situations.

Sleep Deprivation

William Dement researched dream deprivation by waking individuals during REM sleep, leading to:

  1. REM Pressure: The accumulated need for REM sleep that is only alleviated through additional REM sleep.

  2. REM Rebound: An increase in REM sleep following periods of dream deprivation.

  • Effects of REM deprivation include:

    • Changes in animal feeding patterns based on light-dark cycles, without altering the overall quantity eaten.

    • An uptick in aggressive and sexual behaviors in animals.

  • Drugs associated with causing REM deprivation include barbiturates, amphetamines, and alcohol.

Physiology of Sleep

Two primary pathways through which the RAS promotes arousal include:

  • Reticular Activating System

  • Thalamus

  • Cerebral Cortex

  • Hypothalamus

  • Basal Ganglia

  • Basal Forebrain

  • Hippocampus

Neurotransmitters of Sleep

The following neurotransmitters are implicated in sleep regulation:

Neurotransmitters That Promote Arousal

  1. Acetylcholine

  2. Norepinephrine

  3. Serotonin

  4. Histamine

  5. Orexin

Neurotransmitter That Promotes Sleep

  • GABA (Gamma-Aminobutyric Acid) is chiefly responsible for promoting sleep states.

Possible Functions of Sleep

According to Hartmann (1973):

  1. Restorative Function: Stages 3 and 4 are the most restorative, while REM sleep helps restore attention and emotional balance.

  2. Organization of the Brain: Dement (1972) posited that increased REM sleep during developmental stages facilitates brain organization.

  3. Programming Device: Sleep serves to consolidate new information and integrate complex associative memories.

Learning Check 2

  1. Which stage or stages of sleep are identified as NREM?

    • A. Stages 1-4

    • B. Stage 1

    • C. Stages 2 & 3

    • D. Stage 4

Learning Check 3

  1. Most REM sleep occurs:

    • A. when we first fall asleep

    • B. early in the night

    • C. in the middle of the night

    • D. later in the night

Stress
Selye (1973)

Selye indicated that stressors bring individuals away from their optimal states, necessitating a stress response to restore balance.

Kemeny (2003)

The nature of the stress response is dictated by various factors related to the stressor, such as:

  • Controllability

  • Ambiguity

  • Novelty

  • Duration

  • Demands placed on the person

Triggers of Stress

Both physical and psychological triggers can provoke stress, often signified by emotional upheaval or disruptions in behavior.

Hypothalamic-Pituitary-Adrenal Axis

In response to stressors, the following sequence is activated:

  1. Detection of the stressor by the hypothalamus

  2. Activation of the Sympathetic Nervous System

  3. Release of Cortisol, Epinephrine, and Norepinephrine from the Pituitary Gland

  4. Activation of Corticotropin-Releasing Hormone (CRH)

  5. Activation of Adrenocorticotropic Hormone (ACTH)

  6. Response from the Adrenal Medulla and Adrenal Cortex

General Adaptation Syndrome

Developed by Hans Selye, General Adaptation Syndrome consists of three stages:

  1. Stage 1: Alarm Response

    • Release of corticoids prepares the organism for confrontation.

    • Epinephrine circulates, enhancing fight or flight ability.

  2. Stage 2: Stage of Resistance

    • Functions that were heightened during the alarm response are normalized but focus on areas of the body experiencing stress.

  3. Stage 3: Stage of Exhaustion

    • General physiological responses are reactivated, risking mortality if the stressor persists.

    • Alcohol use may increase, but it does not provide relief from the stressors.

Buffers Against Stress

Several factors can serve as buffers against the impacts of stress:

  • Hardiness: Characterized by commitment, perception of control, and acceptance of challenges; having a sense of curiosity and internal locus of control can be beneficial.

  • Exercise: Shown to mitigate both psychological and physiological stress effects.

  • Social Support Theory: The presence of social support offers protection against stress, showing a more significant effect on men than women.

  • Explanatory Style & Expressive Style: A pessimistic explanatory style can be damaging, paralleling attributes observed in hardiness.

Other Minor Buffers

  1. Knowledge about stressors

  2. Emotional insulation

  3. Perspective beyond immediate challenges

  4. Meditation practices

Learning Check 4

  1. The master gland within the endocrine system is:

    • A. Pituitary Gland

    • B. Adrenal Gland

    • C. Thyroid Gland

    • D. Hypothalamus