Download Ch 16 - Motivation - Head

Bear: Neuroscience: Exploring the
Brain 3e
Chapter 16: Motivation
Slide 1
Neuroscience: Exploring the Brain, 3rd Ed, Bear, Connors, and Paradiso Copyright © 2007 Lippincott Williams & Wilkins
The Hypothalamus, Homeostasis, And
Motivated Behavior
Three components of neuronal response
(periventricular zone)
Humoral response --> pituitary
Visceromotor response --> ANS
Somatic motor response --> cortex
After Thanksgiving, why do I lose the weight
without dieting? Is this related to yo-yo
dieting?
Slide 2
Neuroscience: Exploring the Brain, 3rd Ed, Bear, Connors, and Paradiso Copyright © 2007 Lippincott Williams & Wilkins
Hormonal and Hypothalamic Regulation
of Body Fat and Feeding
Body Fat and Food Consumption
Lipostatic hypothesis
Parabiosis: E.g., Siamese twins
Leptin
Regulates body mass
Decreases appetite
Increases energy
expenditure
Leptin depletion
Incites adaptive responses
to fight starvation
Neuroscience: Exploring the Brain, 3rd Ed, Bear, Connors, and Paradiso Copyright © 2007 Lippincott Williams & Wilkins
Slide 3
Hormonal and Hypothalamic Regulation
of Body Fat and Feeding
The Hypothalamus and Feeding
Anorexia
Severely diminished appetite for food
Can be caused by lesions in lateral
hypothalamus
(So normally the lateral hypothalamus
correlates with hunger)
Slide 4
Neuroscience: Exploring the Brain, 3rd Ed, Bear, Connors, and Paradiso Copyright © 2007 Lippincott Williams & Wilkins
Hormonal and Hypothalamic Regulation
of Body Fat and Feeding
The Hypothalamus and Feeding
Obesity
Overeating.
Can be caused by bilateral lesions in
ventromedial hypothalamus
(So normally, the ventromedial hypothalamus
helps you feel satiated)
arcuate n. part of this
Slide 5
Neuroscience: Exploring the Brain, 3rd Ed, Bear, Connors, and Paradiso Copyright © 2007 Lippincott Williams & Wilkins
Hormonal and Hypothalamic Regulation
of Body Fat and Feeding
The Hypothalamus and Feeding (Cont’d)
Anorexia and Obesity
Slide 6
Neuroscience: Exploring the Brain, 3rd Ed, Bear, Connors, and Paradiso Copyright © 2007 Lippincott Williams & Wilkins
Hormonal and Hypothalamic Regulation
of Body Fat and Feeding
The Effects of Elevated Leptin Levels on the
Hypothalamus
Arcuate nucleus
Located at the base of the third
ventricle
Activation of arcuate neurons that release
αMSH and CART peptides
Anorectic peptides- diminish appetite
Slide 7
Neuroscience: Exploring the Brain, 3rd Ed, Bear, Connors, and Paradiso Copyright © 2007 Lippincott Williams & Wilkins
Hormonal and Hypothalamic Regulation
of Body Fat and Feeding
The Effects of Elevated Leptin Levels on the
Hypothalamus
Activation of arcuate neurons that release
αMSH and CART peptides (Cont’d)
Project to hypothalamic regions that
orchestrate coordinated response of:
1. Humoral response - paraventricular
n. contains parvocellular neurons
that project to ant. Pit. --> TSH,
ACTH
Slide 8
Neuroscience: Exploring the Brain, 3rd Ed, Bear, Connors, and Paradiso Copyright © 2007 Lippincott Williams & Wilkins
Hormonal and Hypothalamic Regulation
of Body Fat and Feeding
The Effects of Elevated Leptin Levels on the
Hypothalamus
Activation of arcuate neurons that release αMSH
and CART peptides (Cont’d)
Project to hypothalamic regions that
orchestrate coordinated response of:
1. Humoral response - paraventricular n.
contains parvocellular neurons that project
to ant. Pit. --> TSH, ACTH
2. Visceromotor response: ANS increases
symp. NS
Slide 9
Neuroscience: Exploring the Brain, 3rd Ed, Bear, Connors, and Paradiso Copyright © 2007 Lippincott Williams & Wilkins
Hormonal and Hypothalamic Regulation
of Body Fat and Feeding
The Effects of Elevated Leptin Levels on the
Hypothalamus
Activation of arcuate neurons that release αMSH
and CART peptides (Cont’d)
Project to hypothalamic regions that
orchestrate coordinated response of:
1. Humoral response - paraventricular n.
contains parvocellular neurons that project
to ant. Pit. --> TSH, ACTH
2. Viscero-motor response: ANS increases
symp. NS
3. Somatic Motor Response: Inhibits lateral
hypothalamus (hunger center)- projects to
cortex
Slide 10
Neuroscience: Exploring the Brain, 3rd Ed, Bear, Connors, and Paradiso Copyright © 2007 Lippincott Williams & Wilkins
Elevated
Leptin
levels:
3. somatic motor
1. humoral
2. visceromotor
Slide 11
Neuroscience: Exploring the Brain, 3rd Ed, Bear, Connors, and Paradiso Copyright © 2007 Lippincott Williams & Wilkins
Hormonal and Hypothalamic Regulation
of Body Fat and Feeding
The Effects of Decreased Leptin Levels on the
Hypothalamus
Activation of arcuate neurons that release NPY
and AgRP
Effects on energy balance: Opposite to the effects
of αMSH and CART
Orexigenic peptides– increase appetite
1. NPY and AgRP inhibit secretion of TSH and
ACTH (humoral)
2. Activate parasympathetic division of ANS
(visceromotor)
3. Stimulate feeding behavior (somatic motor)
Slide 12
Neuroscience: Exploring the Brain, 3rd Ed, Bear, Connors, and Paradiso Copyright © 2007 Lippincott Williams & Wilkins
The Effects of Decreased Leptin Levels on the
Hypothalamus (Cont’d)
Slide 13
Neuroscience: Exploring the Brain, 3rd Ed, Bear, Connors, and Paradiso Copyright © 2007 Lippincott Williams & Wilkins
Hormonal and Hypothalamic Regulation
of Body Fat and Feeding
The Control of Feeding by Lateral Hypothalamic
Peptides - (3. Somatic motor response)
Lateral hypothalamus: Motivation to eat (hunger
center)
Electrical stimulation: Triggers feeding behavior
in satiated animals
Caveat
MCH: Peptide nt
Informs cortex about low leptin levels
Motivates the search for food
Orexin: peptide nt, also.
Slide 14
Neuroscience: Exploring the Brain, 3rd Ed, Bear, Connors, and Paradiso Copyright © 2007 Lippincott Williams & Wilkins
Hormonal and Hypothalamic Regulation
of Body Fat and Feeding
Summary: The Effects of Elevated/Decreased
Leptin Levels on the Hypothalamus
A rise in leptin levels
Increases αMSH and CART in arcuate
neurons  inhibit feeding behavior and
increase metabolism
A fall in leptin levels
Increases NPY and AgRP in arcuate and
MCH neurons in lateral hypothalamus 
stimulates feeding behavior and
decreases metabolism (MCH, orexin)
Slide 15
Neuroscience: Exploring the Brain, 3rd Ed, Bear, Connors, and Paradiso Copyright © 2007 Lippincott Williams & Wilkins
Summary Activity
Take a few moments to look over your
worksheet
Identify questions you have
Summarize in a table, in words, or out loud to
your partner the long term regulation of
feeding behavior without looking at your
notes.
Slide 16
Neuroscience: Exploring the Brain, 3rd Ed, Bear, Connors, and Paradiso Copyright © 2007 Lippincott Williams & Wilkins
The Short-Term Regulation of Feeding
Behavior
Motivation to eat—depends on
Time and quantity of last meal
Appetite, Eating, Digestion, and Satiety
3 phases: Cephalic; Gastric; Substrate
Slide 17
Neuroscience: Exploring the Brain, 3rd Ed, Bear, Connors, and Paradiso Copyright © 2007 Lippincott Williams & Wilkins
The Short-Term Regulation of Feeding
Behavior
Appetite, Eating,
Digestion, and Satiety
Gastric Distension
Cholecystokinin
Insulin
Slide 18
Neuroscience: Exploring the Brain, 3rd Ed, Bear, Connors, and Paradiso Copyright © 2007 Lippincott Williams & Wilkins
Why Do We Eat?
Reinforcement and Reward
Liking: Hedonic
Wanting: Drive reduction
Electrical self-stimulation: Experiments to
identify sites of reinforcement
Effective sites for self-stimulation:
Trajectory of dopaminergic axons in the
ventral tegmental area projecting to the
forebrain
Drugs that block dopamine receptors:
Reduce self-stimulation
Slide 19
Neuroscience: Exploring the Brain, 3rd Ed, Bear, Connors, and Paradiso Copyright © 2007 Lippincott Williams & Wilkins
Why Do We Eat?
The Role of Dopamine in Motivation
Old belief: Dopamine projection served
hedonic reward
New understanding
Dopamine-depleted animals “like” food
but “do not want” food
Lack motivation to seek food, but enjoy
it when available
Stimulation of the dopamine axons
Craving for food without increasing the
hedonic impact
Slide 20
Neuroscience: Exploring the Brain, 3rd Ed, Bear, Connors, and Paradiso Copyright © 2007 Lippincott Williams & Wilkins
Why Do We Eat?
The Role of Dopamine in Motivation
Serotonin, Food, and Mood
Serotonin as a neurotransmitter
Serotonin levels
Low: Postabsorptive period
Rise: In anticipation of food
Spike: During meals
Mood elevation
Rise in blood tryptophan and brain
serotonin
Slide 21
Neuroscience: Exploring the Brain, 3rd Ed, Bear, Connors, and Paradiso Copyright © 2007 Lippincott Williams & Wilkins
Why Do We Eat?
The Role of Dopamine in Motivation
Serotonin, Food, and Mood (Cont’d)
Drugs that elevate serotonin levels
Example: Dexfenfluramine (Redux)
Disorders: Anorexia nervosa; Bulimia
nervosa both often accompanied by
depression
Treatment
Antidepressant drugs—elevate brain
serotonin levels
Example: Fluoxetine (“Prozac”)
Slide 22
Neuroscience: Exploring the Brain, 3rd Ed, Bear, Connors, and Paradiso Copyright © 2007 Lippincott Williams & Wilkins
Other Motivated Behaviors
Drinking
Hypovolemia
Decrease in blood volume
Hypertonicity
Increase in the concentration of
dissolved substances in the blood
Vasopressin: Antidiuretic hormone or ADH
Acts on kidneys to increase water
retention
Inhibit urine production
Slide 23
Neuroscience: Exploring the Brain, 3rd Ed, Bear, Connors, and Paradiso Copyright © 2007 Lippincott Williams & Wilkins
Other Motivated Behaviors
Drinking (Cont’d)
Volumetric thirst
Thirst triggered by
hypovolemia
Slide 24
Neuroscience: Exploring the Brain, 3rd Ed, Bear, Connors, and Paradiso Copyright © 2007 Lippincott Williams & Wilkins
Other Motivated Behaviors
Drinking (Cont’d)
OVLT—vascular organ of
the lamina terminalis
Role of OVLT neurons
Excite magnocellular
neurosecretory cells
Stimulate
osmometric thirst
Diabetes insipidus
Treatment—replace
missing vasopressin
Slide 25
Neuroscience: Exploring the Brain, 3rd Ed, Bear, Connors, and Paradiso Copyright © 2007 Lippincott Williams & Wilkins
Other Motivated Behaviors
Temperature Regulation
Cells fine-tuned for constant temperature—
37°C (98.6ºF)
Neurons for temperature homeostasis
Clustered in anterior hypothalamus
Humoral and visceromotor responses
Neurons in the medial preoptic area
of the hypothalamus
Somatic motor (behavioral) responses
Neurons of lateral hypothalamic area
Slide 26
Neuroscience: Exploring the Brain, 3rd Ed, Bear, Connors, and Paradiso Copyright © 2007 Lippincott Williams & Wilkins
Other Motivated Behaviors
Temperature Regulation (Cont’d)
Process during a fall in temperature:
TSH released by
anterior pituitary
TSH stimulates
release of thyroxin
from thyroid gland
Increase in cellular
metabolism
Visceromotor response: Goosebumps
Involuntary somatic motor response
Shivering, seeking warmth
Rise in temperature: Metabolism slowed by
reducing TSH release
Slide 27
Neuroscience: Exploring the Brain, 3rd Ed, Bear, Connors, and Paradiso Copyright © 2007 Lippincott Williams & Wilkins
Other Motivated Behaviors
Temperature Regulation (Cont’d)
Hypothalmic responses to stimuli that
motivate behavior
Slide 28
Neuroscience: Exploring the Brain, 3rd Ed, Bear, Connors, and Paradiso Copyright © 2007 Lippincott Williams & Wilkins
Concluding Remarks
Overview of motor systems
Addressed “how” questions of behavior
E.g., How is movement initiated?
Overview of motivation systems
Addresses “why” questions of behavior
E.g., Why do we drink when dehydrated?
The important discovery of a neural basis for
feeding behavior
Allows us to frame new questions that will
impact how we view our own behaviors
Slide 29
Neuroscience: Exploring the Brain, 3rd Ed, Bear, Connors, and Paradiso Copyright © 2007 Lippincott Williams & Wilkins
End of Presentation
Slide 30
Neuroscience: Exploring the Brain, 3rd Ed, Bear, Connors, and Paradiso Copyright © 2007 Lippincott Williams & Wilkins