Motivation and Reward

Motivation

• Internal factors
• External factors
• Behaviour

Drives

• Goals

Incentives

• Reinforcer

Complementary and influential

Central pattern generators

• Mechanisms for drive control?

Physiology and Drives

"Tissue needs"

Homeostasis

• Balance

Regulatory drive

• Maintains homeostasis

Non-regulatory drive

• Some other purpose

Drives as Brain States

Central-state theory of drives

• Neural activity in different sets of neurons
• Central drive system
  • Neural circuits involved in drive

Input

• Signals to raise and lower drive

Output

• Perception, cognition, motor

Hypothalamus as Hub of Central Drive System

Near brainstem

Tracts to many brain areas

Linked to autonomic system

Hormones


• Sensitive to
• Controls release of

Hypothalamic Control of Hunger

Lateral area

• Food seeking when neurons active
  • Bilateral lesions...starvation
  • Electrical stimulation...eat

Ventromedial area

• Satiety center when neurons active
  • Bilateral lesions...obesity
  • Electrical stimulation...don't eat

Inhibitory connections

• From ventromedial to lateral area

More generally...

Lateral hypothalamus

• Goal directed behaviour
  • Hunger, thirst, sex...
• Lesioning studies
  • Tracts of axons through this area
    • Brainstem, basal ganglia
    • Motor-activation system: "Do something!"
  • Neurons in the area
    • Hunger

Ventromedial hypothalamus

• Autonomic nervous system
• Parasympathetic control of digestion
• Lesioning studies
  • No inhibition of parasympathetic...overactive
  • Hyper metabolization
    • Nutrients converted to fat...inaccessible
  • Always feel hungry

Diet pills

• $200 million per year market in U.S.A.
• CNS stimulant
  • Phenylpropanolamine (PPA)
  • Amphetamines
• So what?
  • Parasympathetic system
    • Anxious, angry, excited
    • Not hungry
  • Addictive!
    • e.g., Judy Garland

Sleeping and Dreaming

Sleep as a drive

Altered state of consciousness

Electroencephalograms (EEGs)

• Recording of electrical activity of the brain

Alpha waves

• Relaxed, awake
• Slow
• Spontaneous, synchronized neural firing

Beta waves

• Alert, awake
• Fast
• Directed, irregular neural firing

Sleep cycles

Stage 1

• Brief, transition state

Stages 2 and 3

• Deeper sleep

Stage 4

• Muscle tension, heart rate, breathing decline
• Deepest sleep: delta waves

Cycle through:

• Stages 1, 2, 3, 4, 3, 2, REM, 2, 3, 4,...

REM

• Rapid eye movement
• EEG is unsynchronized
  • Looks like beta waves
• Dreams

How's and Why's of Sleep?

Biological rhythm

• Circadian rhythm
  • 24 hours
  • Temperature, hormones, behaviour, activity
• Light cues
• Hypothalamus
  • Suprachiasmatic nucleus
    • Rhythm generating neurons
    • Pattern generator

Slow-wave sleep

• Medulla and pons
  • Soma here...send axons to cortex
  • Serotonin
    • Inhibitory
  • Innervated from hypothalamus
• Restoration theory
  • Healing time
  • Body processes slow down
• Protection theory
  • Evolutionary
  • Energy saving
  • Protection

REM sleep

• Pons
  • Excitatory on brain activity
  • Inhibitory on motor neurons
  • Cataplexy

Dreams

Freudian dream theory

• Wish fulfillment
• Unconscious messages
• Interpretation of symbols

Activation-synthesis hypothesis

• Awake
  • Actively interpret incoming stimuli
• Asleep
  • Sources of incoming stimuli inhibited
  • Brain keeps trying to organize cortical activity
• Pontine reticular neurons
  • Send motor stimuli
  • But muscles inhibited
  • Cortex "invents" context
    • Dreams are very movement oriented

Synaptic exercise

• Synapses change with learning
  • Lost or gained
• Asleep roughly 30% of your life
• Perceptual and motor cortex
  • Dreams: hallucinations
• Fetal dreaming

Neurological and psychoanalytical

Driven to Ask:

"Diet pills control my life!" What do the diet pills actually control?

During mid-term week is more sleep really the answer to your problems?

Do dreams cause REM patterns, or is it the other way around?

Fish do not dream. Reptiles do, but only show "proto-dreams" (barely enter REM-like states). Birds dream for several seconds at a time. Mammals dream for longer periods the more related they are to humans. Humans dream more than any other animal. Is there an evolutionary reason for this pattern? How about an environmental reason?