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Brain and Motivational States:Biological Rhythms, Circadian rhythms, Hunger/Feeding

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Neurological Basis of Behavior (PSY - 610)
VU
Lesson38
Brain and Motivational States
Objectives:
To familiarize the students with the
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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, Body weight set point (Theories), Obesity, Anorexia Nervosa, thirst, bio-rhythms,
Sleep and awakening.
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Pathology related to sleep cycles
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Sleep disorders and treatment
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Neurophysiology and biorhythms, Sleep and awakening cycles, Dreams, Sleep disorders
Biological Rhythms:
All biological systems are running on some cycle or the other, at any given point in time. When changes
occur in the body or behaviorual functioning on a regular basis i.e. rhythmic, these are called biological
cycles and these follow a particular rhythm. These cycles could be short within a day (hunger), or
diurnal i.e. of day/night or could be monthly (menstrual cycle), or yearly (reproductive cycle in
animals). These biological rhythms/cycles have important influence on behaviors of animals
The characteristics of biological rhythms:
1. Period: This is defined as the time required for a rhythm to be complete. This mean when a cycle is
called a period (from the beginning to the end)
2. Frequency: The reciprocal of a period e.g. body temperature reaches a peak once a day. The body
temperature period would be 24 hours and frequency would be once in 24 hours. There are cycles such a
reproductive behaviors in animals of 12 month period with a frequency of one (once a year mating
season) per reproductive cycle.
3. Amplitude: is the amount of change from the original starting point i.e. 98.40+1 F or 98.40+1.50 F.
How large is the change from the set point or the original point in the cycle. There are individual
differences in amplitude. One person may have a rise of .5F the other a rise of 1F degrees
4. Phase: The peak of the rise in temperature may also be different. One person may have a peak at
2.p.m. another at 3 p.m. and still another at 4p.m. Similarly the drop in temperature may also differ from
person to person (gender and metabolism). The phase is complete with the peak (highest) and trough
(lowest). The phase is always with reference to the time of the day, time of the month, time of the year,
or some other external marker. The three people with different peaks would be out of phase with each
other. Similarly there are those who stay up all night and sleep during the day and those who sleep at 10
every night and wake up at 5.00 every morning. These two are totally opposite to each other and out of
phase with each other.
Biological Rhythms
The biological rhythms /clocks control the functioning of most behaviors that are biological including
the thermostat, female estrus cycles, the hunger and thirst, and sleep cycles and these are entrained with
the light /dark cycles.
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Neurological Basis of Behavior (PSY - 610)
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Circadian rhythms
These are biological rhythm cycles which follow a day cycle: circadian: Circa: circle, and dian from
diem= of a day. The daily cycles are many such as temperature and most important (and obvious) of
sleep/ awakening, feeding.
There are other rhythms and cycles, such as the estrous cycle, (in some animals it appears once a year or
so)
Studies have shown that there are rhythms for every biological response in the body measured: the
epidermal (skin temperature) response, urine, blood, whole body temperature, physical rigor (energy to
do work), weight, heart rate, blood pressure, respiratory peak flow, Growth Hormone levels, and even
Plasma ACTH (stress hormone levels). Studies have also shown that body's response to drugs (such as
pain killers) also differs with the time of the day, implying the smaller or larger dose may be necessary
for the therapeutic effect.
The Circadian Rhythms are controlled through the Suprachiasmatic Nucleus (SCN) located in the
medial hypothalamus. Lesions in the SCN breaks down the behavioral circadian rhythms in rats
drinking and adrenal cortisone responses were affected in SCN lesioned rats (Zucker 1972). In hamster,
the estrus cycles (female's ovulatory cycles) are also disrupted.
How can our circadian rhythms be changed or influenced: by phase shifts (day and night shift workers
have not just sleep to take care of but their body adjusts by making changes in the other cycles as well.
Studies on changes in 12 hour shifts have shown that adaptation of shifts to heart rate, Norepinephrine,
epinephrine levels, body temperature, stomach enzyme production, and performance peaks also were
affected (Higgins 1975),
Menstrual cycles of women were also found to be disrupted if they were traveling across continents and
their sleep/awake cycles were disrupted (jet lags?)
Day/Night and dark light cycles also affect mental health. In countries where there are long dark
winters, there is behavioral syndrome known as the winter blues.
Circadian and other biological rhythms are important modulators of behaviors in man and animals.
Body Temperature and biological cycle: circadian (of a day)
The body temperature is not constant throughout the day. Depending on the type of species, whether
these are nocturnal (night foragers: night hunter) or day forager, their body temperature would rise and
fall accordingly. The temperature peaks whenever the animal is most active, therefore for the humans,
horse and other day animals it would peak during the mid afternoon. The rodent rat is nocturnal
therefore its temperature peaks at night. Similarly the lowest temperature would be at night for the day
foragers and during day for the nocturnal animals. The set point for the body temperature is set by the
light /dark cycles which set the biological clock which in turn sets the biological metabolism (faster
during awake and slower during sleep- to save on energy) Temperature lowest during sleep, because
metabolism is lowered. Sleep reduces demand on metabolic heat production
Therefore, the L/D cycles-set the biological clock which in turn sets the temperature-set point? In some
species the thermoregulatory behavior is modulated for longer cycles such as Hibernation. Hibernation
is when the animals moves into a state where the body temperature is reduced and metabolism slowed to
particular level. There is limited requirement of fats etc, and the body can go a long way on the stores of
fat. There are bears and other animals which hibernate in winter and others such as birds which fly away
for winters (the Siberian birds migrate towards the Arabian Sea coastal areas for the winters)
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Among the other important biological systems which have an autonomic modulating mechanism, one of
the most important ones is hunger through which energy and nutrition is provided to ensure the survival
of the organism's systems
Hunger/Feeding
Feeding is an essential behavior as provision of nutrients, energy for survival for heat production for
metabolism all depend on what is eaten by the animal. Animals must eat enough to maintain their
requirement and to maintain body weight. If they exceed the input and not sue it ­ it would lead to
obesity, and if they do not take what is required in sufficient amounts it would lead to starvation. The
seeking of food is hunger- and a very strong motivating behavior. Humans and animals spent most of
their awake hours in foraging for food. Food Seeking is part of the homeostatic systems to regulate the
organism internal needs.
Hunger/feeding as a motivated behavior
Food intake/feeding/hunger is motivated behavior, because feeding behavior
a) Periodic: it is tied with the body's energy consumption, metabolism, its needs, the external
environment (temperature etc).the signals for onset of feeding and of stopping eating increase and
decrease with the internal and external signals and clocks.
b) Priority: Feeding has high survival value therefore it takes priority over other behaviors such as
mating. Animals would seek food over seeking others. A hungry man would see the moon as roti, and
the man whose stomach is full can think of the beloved face like the moon.
c) Purposive: very much goal directed when food is sought and animal is hungry. The behavior would
continue till hunger is sated.
d) Persistence: Food seeking is persistent. It would continue till the goal has been achieved and enough
food taken in.
Although there are many set points within the feeding cycle, there are two major set points which have
to be maintained by the feeding behaviors
a) Body weight set point. This set point ensures that the body weight is maintained at a constant so if
you are 120 or 200 pounds your body works to maintain that weight
b) Body energy and fat content. Within each organism there is a glucose set point and a lipid set point
which the body works to maintain and monitor.
However, remember if the Energy intake is equal to the energy expenditure, i.e. Intake= output, there
would be no weight gain. The body weight would be maintained at a constant level. Weight gain and
weight loss would occur if the equation is imbalanced either for input or output of food.
What are the factors regulating food intake.
This is an interesting question as feeding may occur in the absence of hunger signals. For example,
when we see cakes in a bakery window, or smell samosas frying, there is an urge to eat, an immediate
desire which overrides the full stomach signals!! Or we may defer eating because there is a high priority
for some other activity (run for life, or prepare for exams--- food becomes a low priority)
"Feeding is under a multifactor control and the multiplicity if signals means that there are a number of
feedbacks loops for the initiation and termination of food intake" (Mogensen and Carlson 1977, p10, cf
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Mogensen 1980). This can be understood if we look at the body's requirements, that even though
glucose and fats are the main sources of energy and metabolism, there is also need for proteins for
growth, maintenance (and for NT systems).
If we analyze them intuitively we can identify several possible reasons why we eat and what sets our
hunger signals: we feel hungry because
a) We salivate (Pavlovian dogs!) or our stomach sends signals (rumbles), or we smell food, or because
the body sends signals. These can be classified into the following categories.
Oral, /Peripheral, (also odor) Gastric and Metabolic (neural)
Oral/ peripheral factors: The taste odor, sight and texture of food has role (though small) in the control
of food intake. Animals eat more if the food looks and tastes good, and less if the food tastes bad.
Mouth palatability (how good it tastes and looks) and variety: increases food intake in rats and humans
alike. Palatibility is a very important source of obesity­ eating when not required by the body
Rats like high fat foods very much, and increased total feeding response, and become obese, the same
for mice. Rats would eat quinine adulterated food only if they are starving (wouldn't anyone else?)
Teitlebaum and Epstein (1962) inserted a nasopharyngeal gastric tube which by passed the mouth
region. Rats were trained to send food through tube to stomach- their intake is only how much required
to maintain body weight
Therefore more than mouth and the stomach region are involved in feeding. Snowdon (1969) report that
rats maintain lower than normal weight levels if food is not routed through mouth (oral). There are some
signals from the mouth, (odor and taste).
Another study of eliminating oral factors on food intake is to administer nutrients through intravenous
infusions. Experiments by Nickoliadis and Rowland (1976) "When infusion equaled or was greater than
the normal daily intake, there was an increase of oral intake of the diet..." indicating that there were
some oral factors involved in feeding.
Sight of Food stimuli also leads to an initiation of and increase in eating response even when sated or
full.
In man and higher mammalians, the experience and cognitive factors are important in feeding behaviors.
Therefore, eating different foods, raw or cooked, liking Chinese, Japanese, Thai, Greek, Ethiopian food
is learnt, using different cooking spices are also learnt. The taste aversions are also learnt such as
cultural, religious and other constraints. There are some animals such as snakes, frogs and lizards not
thought edible in majority of the developed world but there are some cultures where these are relished!
We may like the head of the goat and trotters (siri paiy), but they may not be the food of choice in most
countries. What we eat, how we eat (chopsticks/ knives or forks or banana leaves and hands), cooked or
uncooked vegetarian or meat depends on our region. Therefore, human food and eating is determined by
cultural, religious and regional factors,
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
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6. Mogensen, G.J. (1977) The Neurobiology of Behavior. Lawrence Erlbaum 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