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Brain and Motivational States:Resting metabolic state, Individual differences

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Neurological Basis of Behavior (PSY - 610)
VU
Lesson40
Brain and Motivational States
Objectives:
To familiarize the students with the
·
Brain and motivational states
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Homeostasis, include temperature regulation, Cellular and brain controls of Thirst, Reward
systems and addictions, Fear, aggression, attachment
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Hunger, eating, satiation: brain+ NT control, Body weight set point (Theories), Eating Disorders
Obesity, Anorexia Nervosa.
If we look around us disorders of eating, whether it is obesity or anorexia nervosa, anorexia bulimia
seems to have overwhelmed especially our younger generation (mostly females). To understand why
feeding behaviors goes wrong, there must be some mechanism which ensures that weight remain stable
and when that mechanism breaks down the eating disorders are seen.
Obesity is a major problem of the fast food advanced world. In the US 34 million people are overweight
and 12.5 million people are severely overweight. It is now catching up and China where American fast
food was introduced to Chinese culture (where the body and system was not used to the cooking or the
food) led to an emerging obese younger population. Chinese children are actually being sent to camps to
reduce weight!
Obesity is also genetically linked but this does not explain why or how it has become a disorder of
epidemic nature, with more than double the number of obese people in the world in the 20th century. The
reason may be many a) during evolutionary development as hunters man needed to store fats, plus man
walked many miles, had a lot of physical work which did not fat accumulate. As life became more and
more sedentary this stored fats became unhealthy. Similarly changes in style of cooking, storing food
(now you get frozen foods) earlier women used to spend all day grinding corn or wheat for one meal.
Changes in life styles also made a huge difference--the older generation ate healthy foods and had a
healthy life style, the younger generation prefers to eat fried and fast food and very little exercise! These
are actual findings of a survey that a Behavioral Sciences class I taught carried out: to compare four
generations (their grandparents, parents, themselves and their younger brother and sisters).
Eating Disorders: could be acquired, learnt biological, metabolic, acculturated Acquired:
Children are taught to eat what was given to them and to finish their food. Further they learn to associate
eating with reward (parents promise candy for good behaviors!). Nutrition is not the focus at the
growing age. As people grow older they continue to eat the same kinds of food s that as children/
teenagers/ young adults, even though there is reduced nutritional requirement (and still eat as much!)
Then they tend to store fat. Why don't people stop (check out animals, they do stop!). Because in
humans the inhibitory signals are over ridden, and we continue to eat as the food looks good or tastes
good.
The Psychological variables which lead to overeating have been identified as: field dependence, reduced
impulse control, eats food too fast (too much), maladaptive controls, depression, tension etc.
Innate: obesity is a metabolic disorder. It has been reported by researchers that the reason why it is
difficult for fat people to loose weight is because of metabolic factors. There is basal metabolic rate
difference (some have a higher metabolism rate than others). This is supported by the findings that the
food intake of normals and obese people has not been shown to be significantly different (Rodin et al
1989,). However, there may difference in energy expenditure rates and metabolic states
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Neurological Basis of Behavior (PSY - 610)
VU
Resting metabolic state: diet resistant difficulty in losing weight, even after decreased caloric intake.
Those who diet and binge are setting their bodies at a different metabolic rate. The metabolic rate slows
down with each diet--- making it difficult to lose weight after every diet.
However, there are other factors such as underreporting, underrating eating: "I don't eat a thing, but I
keep gaining weight is something familiar we hear from people who have gained weight.
The simple formula is that if food and fat input= energy expenditure output: balance and weight is
maintained at a constant
Interestingly, 70-80% of a person's energy expenditure is through resting metabolism (Thermogenesis,
fidgeting and maintenance of posture/muscle tone: Non exercise thermo genesis)
Metabolism and energy needed to digest and assimilate food: exercise does not reduce weight but only
facilitates aerobics, and toning of body.
Fasting sends the body into the diet induced thermogenesis
Diet binge- Sporadic Dieting affects body's metabolism by setting it into a starvation mode. The
starvation mode means "we need to save what we have on the body" therefore signals and mechanisms
to store food, store fat come into operation. Once the alteration in metabolic efficiency of the body takes
place, it starts storing fats. Therefore diet binges do not work, if anything they slow down the
metabolism.
Individual differences: Why do some people put on weight more easily than others/ Research ahs
shown that there are special brown adipose tissues which may carry the clue. These convert calories
directly into heat. These are important in animals which hibernate. These animals need this to wake up
in spring. This is known as the Non shivering thermogenesis. These cells rich in mitochondria (explains
why they are high metabolic rate cells!) The mitochondria give these cells the brown color which is why
they are known as brown adipose cells. The B adrenergic receptors control the metabolism of these
cells. Increased Norepinephrine levels lead to increased non shivering thermogenesis leading to heat
production. This mechanism is controlled by the medial hypothalamus. Defect in brown adipose tissue
metabolism leads to defects in the breakdown of fat. It has been reported that in normal rats the
increases in metabolism of brown adipose tissue rises by 200% occurs after a meal, whereas in obese
rats this does not happen. This indicates that deficient meal induced thermogenesis may be involved in
eating disorders.
If each meal increases metabolism, then increase in number of meals would burn more through this
process. This has been suggested and been used as a mechanism for weight reduction.
In extreme cases the relevant therapy for treatment of obesity has been a) jaw wiring: to stop the patient
from eating, or intestinal surgery, which reduces the length of the intestines, or reducing the stomach
size by stapling the stomach (gastroplasty)
Reducing the length of INTESTINES lead to reduced gastric activity, but this can cause a great deal of
discomfort!
We have been talking so far of people who overeat, but there are some people who under eat to the point
of starvation. This is especially true of young women who see models and film artists who have become
thin to be fashionable. This disorder is called Anorexia nervosa. In another form of this disorder young
women eat very little and then binge and throw up forcibly. This disorder is known as Anorexia/
bulimia. Their focus is on food- but in a different way. They like to cook, they like to feed people, they
like to talk food, collect recipes--but they do not eat.
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Neurological Basis of Behavior (PSY - 610)
VU
Anorexia: Is it hereditary or enlarged sulci in the brain (return to normal after recovery), enlarged
ventricles (permanent damage), defect in Dopaminergic, noradrenergic, and brain opioids levels- these
may the biochemical/structural defects which lead to Anorexia? Psychotherapy is not effective but the
anorexic drug Fenfluramine is successful in treating anorexics
Self starvation- This has become part of the modern cultural norms? There have been many famous
cases. One such case is that of a famous American popular singer of the 70's, Karen Carpenter who died
of Anorexia. A bright talented young woman who kept starving herself because she thought she was fat.
More recently cat walk models have been required to go through a weighing process in various shows
around the world to ensure that they are not below required levels of Body weight and Mass.
Thus we have seen that feeding though important for survival can be strongly controlled by social and
other factors in humans.
Thirst: fluid intake
Have you ever thought why do you drink fluids/water, you might answer you do so because you get
thirsty, but then ask yourself where do you feel thirst? In our mouth you would reply, because you feel
dryness in your mouth. Then the question is what would cause this dryness? Dry Salivary glands, you
would answer obviously. The salivary glands dry out because of lowered water level in blood leading to
dryness leading to thirst which would lead to drinking.
Thirst is motivated behavior--it is purposive- animals would continue to seek water when thirsty and
only stop when they have taken water. It is periodic as it appears several times (when the animal eats).
This is almost constant seeking of water as water cannot be stored like fats on our body- there is greater
depletion of fluids
Lets think like a researcher,
1) What if water is injected directly into mouth? It leads to reduced drinking.
2) What if we remove the salivary glands? This leads to dryness of mouth, but no increase in drinking.
So what is drinking or fluid intake controlled by.
For survival, every living organism needs water because each cell in the body and all processes need
fluids for maintaining and cleaning the system one of the most important motivated behaviors is thirst.
For average human adult daily water intake and output equals about 2500 milliliters. Water is lost
through the lungs (vapor), through skin (perspiration) through kidneys (urination) and we input it
through drinking, eating foods with high water content (think of melons, or oranges, even meat is 70%
water). The human body is 50-60% water Sources/mechanism to measure fluid level
It is interesting to note that there are two different mechanisms by which fluid is regulated: the
intracellular and the extracellular.
Intracellular monitors the vascular (blood) and nonvascular (Tissue) fluid components. There are saline
levels of the body fluids in addition to the level of water which is needed to be maintained therefore
constant monitoring of
1) Fluid level
2) 9 % level saline in blood and CSF.
If you recall the sodium levels of ions is high on the extracellular membrane and low in the intracellular
membrane. If sodium ions increase in the intracellular membrane, fluid passes through the cell walls to
dilute salt­ inside the same would happen if the sodium concentration increases in reverse. Immediately
fluid forms one compartment move to equalize the fluid and osmotic balance on both sides of the
membrane. If fluid is lost form the intracellular membrane it is known as cellular dehydration, and if it
lost from extracellular compartment it is known as hypovolemia. Both lead to thirst and drinking
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Neurological Basis of Behavior (PSY - 610)
VU
Hypothalamic mechanism of fluid works regulation and drinking. Wayner and Carey (1973) have
shown that two separate regions of the hypothalamic receptors are involved in detection or monitoring
of fluid levels.
Cellular dehydration and Osmoreceptors:
For detection of changes in intracellular fluid level, the lateral hypothalamus is involved, and for
detection of changes in the extracellular fluid level the anterior hypothalamus is more sensitive. Fluid
levels in extracellular more important. The fluid level is constantly monitored
When the cellular dehydration takes place the pituitary releases Antidieuretic Hormone and the animal
starts drinking. The Kidney and hormones produced by kidney become important Renin acts on
Angiotensinogen- which produces Angiotensin II- which acts directly on thirst receptors in
Hypothalamus. The Anti diuretic hormone (ADH) released by Anterior Hypothalamus via posterior
pituitary. Increased release of ADH acts on kidneys to retain fluid/decrease urine volume (excretion of
water) and the decreased ADH is a signal to retain fluid output from the body (save body's water). The
water intake help reduce the osmotic pressure and the water is then absorbed by the intracellular
compartment
The Osmoreceptors are located around the Lateral Pre Optic area of the hypothalamus, which can then
send out signals through cellular mechanism and the neural systems.
There are mechanoreceptors which monitor the hypovolemia (extracellular dehydration) and these
monitor the vascular walls for tonic rate of discharge. Some of these are located near the heart and can
monitor the changes in blood pressure (sound familiar?) which results from hypovolemia
There are two mechanisms of thirst and both these are important for maintaining the fluid levels of the
body and ensuring survival and working of the cells.
Loss of fluid from either compartment lead to primary drinking or this is to restore loss of fluid. But
there is drinking in the absence of water loss which is called secondary drinking. This is not in response
to cellular dehydration but dryness of mouth or psychogenic or other pathological reasons
Drinking is therefore one of most important needs of the body's system and research is ongoing for the
NeuroChemicals and hormones that are involved in this behavior.
References:
1. Carlson N.R. (2005) Foundations of Physiological Psychology Allyn and Bacon, Boston
2. Pinel, John P.J. (2003) Biopsychology (5th edition) Allyn and Bacon Singapore
3. Bloom F, Nelson and Lazerson (2001), Behavioral Neuroscience: Brain, Mind and Behaviors (3rd
edition) Worth Publishers New York
4. Bridgeman, B (1988) The Biology of Behaviour and Mind. John Wiley and Sons New York
5. Brown,T.S. and Wallace.(1980) P.M Physiological Psychology
Academic Press New York
6. Mogensen, G.J. (1977) The Neurobiology of Behavior. LawrenceErlbaum Associates
Note: References 5, 6 more closely followed in addition to the references cited in text.
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Table of Contents:
  1. INTRODUCTION:Descriptive, Experimental and/ or Natural Studies
  2. BRIEF HISTORICAL REVIEW:Roots of Behavioural Neurosciences
  3. SUB-SPECIALIZATIONS WITHIN THE BEHAVIORAL NEUROSCIENCES
  4. RESEARCH IN BEHAVIOURAL NEUROSCIENCES:Animal Subjects, Experimental Method
  5. EVOLUTIONARY AND GENETIC BASIS OF BEHAVIOUR:Species specific
  6. EVOLUTIONARY AND GENETIC BASIS OF BEHAVIOUR:Decent With Modification
  7. EVOLUTIONARY AND GENETIC BASIS OF BEHAVIOUR:Stereoscopic vision
  8. GENES AND EXPERIENCE:Fixed Pattern, Proteins, Genotype, Phenotypic
  9. GENES AND EXPERIENCE:Mendelian Genetics, DNA, Sex Influenced Traits
  10. GENES AND EXPERIENCE:Genetic Basis of behavior, In breeding
  11. GENES AND EXPERIENCE:Hybrid vigor, Chromosomal Abnormalities
  12. GENES AND EXPERIENCE:Behavioral Characteristics, Alcoholism
  13. RESEARCH METHODS AND TECHNIQUES OF ASSESSMENT OF BRAIN FUNCTION
  14. RESEARCH METHODS AND TECHNIQUES OF ASSESSMENT OF BRAIN FUNCTION:Activating brain
  15. RESEARCH METHODS AND TECHNIQUES OF ASSESSMENT OF BRAIN FUNCTION:Macro electrodes
  16. RESEARCH METHODS AND TECHNIQUES OF ASSESSMENT OF BRAIN FUNCTION:Water Mazes.
  17. DEVELOPMENT OF THE NERVOUS SYSTEM:Operation Head Start
  18. DEVELOPMENT OF THE NERVOUS SYSTEM:Teratology studies, Aristotle
  19. DEVELOPMENT OF THE NERVOUS SYSTEM:Stages of development, Neurulation
  20. DEVELOPMENT OF THE NERVOUS SYSTEM:Cell competition, Synaptic Rearrangement
  21. DEVELOPMENT OF THE NERVOUS SYSTEM:The issues still remain
  22. DEVELOPMENT OF THE NERVOUS SYSTEM:Post natal
  23. DEVELOPMENT OF THE NERVOUS SYSTEM:Oxygen level
  24. Basic Neuroanatomy:Brain and spinal cord, Glial cells, Oligodendrocytes
  25. Basic Neuroanatomy:Neuron Structure, Cell Soma, Cytoplasm, Nucleolus
  26. Basic Neuroanatomy:Control of molecules, Electrical charges, Proximal-distal
  27. Basic Neuroanatomy:Telencephalon, Mesencephalon. Myelencephalon
  28. Basic Neuroanatomy:Tegmentum, Substantia Nigra, MID BRAIN areas
  29. Basic Neuroanatomy:Diencephalon, Hypothalmus, Telencephalon, Frontal Lobe
  30. Basic Neurochemistry:Neurochemicals, Neuromodulator, Synaptic cleft
  31. Basic Neurochemistry:Changes in ionic gates, The direct method, Methods of Locating NT
  32. Basic Neurochemistry:Major Neurotransmitters, Mesolimbic, Metabolic degradation
  33. Basic Neurochemistry:Norepinephrine/ Noradrenaline, NA synthesis, Noadrenergic Pathways
  34. Basic Neurochemistry:NA and Feeding, NE and self stimulation: ICS
  35. Basic Neurochemistry:5HT and Behaviors, Serotonin and sleep, Other behaviours
  36. Basic Neurochemistry:ACH and Behaviors, Arousal, Drinking, Sham rage and attack
  37. Brain and Motivational States:Homeostasis, Temperature Regulation, Ectotherms
  38. Brain and Motivational States:Biological Rhythms, Circadian rhythms, Hunger/Feeding
  39. Brain and Motivational States:Gastric factors, Lipostatic theory, Neural Control of feeding
  40. Brain and Motivational States:Resting metabolic state, Individual differences
  41. Brain and Motivational States:Sleep and Dreams, Characteristics of sleep
  42. Higher Order Brain functions:Brain correlates, Language, Speech Comprehension
  43. Higher Order Brain functions:Aphasia and Dyslexia, Aphasias related to speech
  44. Higher Order Brain Functions:Principle of Mass Action, Long-term memory
  45. Higher Order Brain Functions:Brain correlates, Handedness, Frontal lobe