Motivation Ch' 3

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Motivation Ch. 3

• The Brains Role

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Study 1 The All-You-Can-Eat Buffet

• One catch You have to get a shot 30 min. before
  the meal
• Group 1 Placebo
• Group 2 Ghrelin
• Research question Who eats more?
• Answer Those that received the ghrelin hormone

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Study 2 The 3-Month Diet

• Step 1 Monitor ghrelin levels for several days
• Step 2 Begin 3-month diet for some participants
• Step 3 Monitor ghrelin during diet
• Results
• Diet worked 20 body weight loss, maintained
  for 3 months post-diet
• Ghrelin continued to rise even after the diet was
  over

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Study 2 Results
Ghrelin was chronically high for dieters Ghrelin
rises and falls through the day Eating leads to
rapid ghrelin declines Hunger increased for
dieters
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Principle 1 Brain Structures

• Three types of structures are important
• Actual structural areas
• Hypothalamus
• Neural circuits
• Limbic system
• Neurotransmitter pathways
• Serotonin pathway, dopamine pathway

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Principle 2 Biochemistry

• Neurotransmitters
• Nervous system resident
• Mostly generated in the brain
• Hormones
• Endocrine system/bloodstream resident
• Generated in glands
• Both controlled by internal and external states

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Principle 3 Situational Triggers

• Experienced events
• Bodily states
• Behavioral decisions
• Obstacles to goals

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Measuring the Brain

• Direct stimulation
• Rats and electrodes, oh my!
• Open-brain surgery
• fMRI
• Functional magnetic resonance imaging
• Records changes in blood oxygenation
• Oxygenation increased activity

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Important Parts of the Brain
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Approaching

• Hypothalamus eating, drinking, mating
• Medial forebrain bundle (MFB) pleasure, reward
• Septal area sociability, sexuality
• Frontal lobes planning, goal setting, reasoning
• Left prefrontal cortex Positive emotional
  experience

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Avoiding

• Right prefrontal cortex negative emotional
  experience
• Amygdala fear, anxiety, aggression
• Hippocampus behavioral inhibition system

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Reticular Formation

• Located within the brain stem
• Ascending RAS arouses the cortex
• Descending RAS regulates muscle tone

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The Hypothalamus

• Regulates important functions including
• Eating
• Drinking
• Mating
• Controls endocrine system
• Controls ANS activation (sympathetic and
  parasympathetic response modes)

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Medial Forebrain Bundle (MFB)

• Connects the hypothalamus to other limbic
  structures
• Active when pleasurable feelings are
  experienced
• Mild, generally positive feelings

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Amygdala

• Detects and responds to threat
• Impairment can produce
• Tameness/neutral affect
• Preference for isolation
• Loss of fear response
• Inability to remember/learn threats

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Septo-Hippocampal Circuit

• Includes the septal area, hippocampus, cingulate
  gyrus, fornix, thalamus, hypothalamus, mamillary
  bodies
• Primary function is to predict pleasure and
  anxiety before an event occurs
• Uses the memory functions of the hippocampus to
  do this
• Center of approach/avoidance decisions

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Drugs and the Circuit

• Opiates blunt the anxiety effects of the circuit
• Stimulants can augment these effects
• Hippocampus is concerned with mismatches
  (not-okay)
• Septal area is concerned with matches (okay)

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Prefrontal Cortex

• Right prefrontal cortex negative feelings
• Left prefrontal cortex positive feelings
• BAS and BIS
• Individual sensitivity to avoidance and approach
  situations
• Connected to asymmetry in prefrontal cortex
  activation

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Neurotransmitter Pathways

• A cluster of neurons that communicate with others
  using one particular neurochemical
• There are four primary pathways
• Dopamine (reward ? good feelings)
• Serotonin (mood and emotion)
• Norepinephrine (arousal and alertness)
• Endorphin (inhibits pain, anxiety and fear)

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The Dopamine Pathway

• Events that signal reward or pleasure trigger the
  pathway
• Dopamine output provided by the ventral tegmental
  area (VTA)
• Dopamine enhances creativity and problem solving
• Release in proportion to a specific comparison
• Experienced reward ??actual reward

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The Role of Anticipation

• Dopamine is released upon the expectation of
  experiencing reward
• Provides motivational force to some stimulus to
  realize the anticipation (i.e., sexual
  encounters)
• Often, the event itself does not match
  anticipation, and so dopamine release adjusts
• Without dopamine, we not approach ANYTHING

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Dopamine and Memory

• Dopamine teaches us what is inviting or
  pleasurable
• Surprises of pleasure register that event in
  our memories as something worth approaching

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Dopamine and Goal-Directed Behavior

• Dopamine activates a part of the brain that
  releases voluntary skeletal movement
• Thus, we anticipate the event but we are also
  motivated to seek out the realization of the
  event
• We therefore act because of
• The expectation of pleasure
• The desire to achieve the pleasurable state

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The Third Principle The Social Context

• Food deprivation hormone levels, hypothalamus
• Humorous movie dopamine release
• Alarm clock reticular formation
• Your mean boss amygdala
• Disappointment and failure hippocampus
• Coping with stress hippocampus, dopamine
• Opiates medial forebrain bundle, endorphin sites

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Our Brains and Our Awareness

• Lingual and non-lingual structures
• Conscious goals vs. urges and appetites
• Other examples
• We are likely to help if we are in a positive
  mood
• We socialize more on sunny days
• We are more violent when it is hotter