Psych 623 Midterm 1

Front 1

Tinbergen’s Questions
About Causes of Behavior
involve 4 levels of analysis. What are they?

Back 1

IMMEDIATE CAUSATION
DEVELOPMENT
EVOLUTION/NATURAL SELECTION
ADAPTIVE FUNCTION

Front 2

Advantages of Animal Models (7)

Back 2

1.Continuity of behavior from one species to another through evolution
2. Simplest system with qualities of interest
3.More economical to develop methods on animals that may be useful for people.
4.Ethical considerations; some manipulations are not permissible in humans
5.Function of behavior often becomes clearer when viewed in a comparative manner
6.Places human system in perspective
7.Generalizations can be gained from animal models then tested in humans

Front 3

Disadvantages of Animal Models (4)

Back 3

1. Enormous species differences
(behaviors may represent adaptations to very specific environments)
2. Behavioral gap between animals and humans is great (Language & Cultural evolution)
3.To get the “cleanest” answers about simplest analyses, the less cognition, the better.
4.Ethical considerations

Front 4

What steps do you take in order to make a strong inference?

Back 4

1) Devise alternative/multiple hypotheses
2) Design and execute experiment that will permit rejection of as many of the hypotheses as possible
3) Retain surviving hypotheses
4) Recycle
Science advances only by disproofs. Common misconception is that goal of scientific enterprise is to develop theories that cannot be disproved. Wrong. Marxist, Freudian, Darwinian theories cannot be disproved

Front 5

What is chronobiology

Back 5

Scientific study of biological clocks and their associated rhythms
Also called Biochronometry
Began in the early 1960s
Had to counteract the dogma of homeostasis in biology and medicine
Core body temperature varies across the 24 h day
-Borrowed terms and concepts extensively from engineering disciplines to describe biological clocks and their associated rhythms

Front 6

RHYTHM

Back 6

A recurrent event that is characterized by its period, frequency, amplitude, and phase.

Front 7

period

Back 7

The length of time required to complete one cycle of the rhythm in question.
For instance, the amount of time required to go from peak to peak or trough to trough.

Front 8

FREQUENCY

Back 8

Computed as the number of completed cycles per unit of time.
For example, 2 cycles per day.

Front 9

amplitude

Back 9

The amount of change above and below the average value.
That is, the distance of the peak or nadir from the average.

Front 10

phase

Back 10

Represents a point on the rhythm relative to some objective time point during the cycle

Front 11

Exogenous versus Endogenous Control of Biological Clocks

Back 11

Some behavioral rhythms have been recognized since ancient times, but they have generally been attributed to exogenous (outside the organism) factors.
Recent evidence indicates that endogenous (inside the organism) timing mechanisms mediate many of the observed rhythms in physiology and behavior.

Front 12

How is it determined whether a rhythm is the result of exogenous factors or an endogenous clock?

Back 12

Isolation experiments

Front 13

Exogenous versus Endogenous Control of Biological Clocks

Back 13

Jean Jacques d’Ortous de Mairan found that the tension–relaxation pattern of a heliotropic plant persisted when isolated from exogenous factors.

Front 14

Recent Evidence that Biological Clocks are Endogenous

Back 14

Animals maintained in constant conditions aboard a spacecraft orbiting far above the earth, and presumably away from subtle geophysical cues, display biological rhythms with periods similar to those observed on earth.

Front 15

Recent Evidence that Biological Clocks are Endogenous

Back 15

Animals maintained in adjacent, but individual, cages in the absence of environmental cues display biological rhythms with slightly different periods, suggesting that they are not being driven by the same subtle geophysical cue;

Front 16

Recent Evidence that Biological Clocks are Endogenous (3)

Back 16

Animals maintained in constant conditions aboard a spacecraft orbiting far above the earth, and presumably away from subtle geophysical cues, display biological rhythms with periods similar to those observed on earth.

Animals maintained in adjacent, but individual, cages in the absence of environmental cues display biological rhythms with slightly different periods, suggesting that they are not being driven by the same subtle geophysical cue;

The period (and phase) of the biological rhythms of one individual can be transferred to another individual by means of tissue transplants.

Front 17

Circadian

Back 17

Revolution of planet
24 h (22-26 h)

Front 18

Circatidal

Back 18

Tides
12.4 h (11-14 h)

Front 19

Circalunar

Back 19

Phases of the moon
29.5 days (26-32 days)

Front 20

Circannual

Back 20

Seasons of the year
365.25 days (300-400 days)

Front 21

COMPARISON OF BIOLOGICAL RHYTHMS

Back 21

Circadian, Revolution of planet
24 h (22-26 h)
Circatidal, Tides
12.4 h (11-14 h)
Circalunar, Phases of the moon
29.5 days (26-32 days)
Circannual, Seasons of the year
365.25 days (300-400 days)

Front 22

Figure 10.6; page 505

Back 22

The rhythms persist in the absence of the geophysical cue to which they are normally synchronized (entrained), with a period that approximates that of the geophysical cycle.
Ultradian (shorter than circadian) rhythms
Infradian (longer than circadian) rhythms (persist in constant conditions, but do not correspond to any known geophysical cue)

Front 23

Usefulness of biological clocks (2)

Back 23

Synchronizing the activities of animals with their environments (including social)
To prepare for predictable events (e.g., winter, night, etc.)
Synchronizing the internal physiological and biochemical processes of animals
To promote efficient functioning

Front 24

General Characteristics of biological clocks and rhythms (6)

Back 24

inherited, tempature independent, relatively resistant to the influence of chemicals, entrainment is limited to specific ranges, independent of behavioral feedback, bio clocks are found at every level of organization in an organism,

Front 25

One of theGeneral Characteristics of Biological Clocks and Rhythms is that they are
inherited. Describe this.

Back 25

When mutant animals with free-running circadian rhythms > 25 hrs are mated with each other, their offspring tend to have longer free-running periods than the offspring of mutants with free-running rhythms < 23 hrs (and vice versa)

Front 26

General Characteristics of Biological Clocks and Rhythms
Temperature independence
Describe

Back 26

activities or events that change body temperature don't significantly alter circadian clocks
otherwise there would be speed-ups and slow-downs and eventually all resemblance to a 24 hr period would be lost

Front 27

General Characteristics of Biological Clocks and Rhythms
Relatively resistant to the influence of chemicals -describe

Back 27

If not, the food consumed would constantly be altering biological clocks.
A few pharmacological manipulations have been shown, however, to affect clocks
Protein synthesis inhibitors
Alcohol (EtOH)
Lithium
Heavy water (deuterium)

Front 28

General Characteristics of Biological Clocks and Rhythms
Entrainment is limited to specific ranges-describe

Back 28

A circadian rhythm can be entrained to a 23 h day by providing 11.5 h of light and 11.5 h of dark (same for 12.5 h light/12.5 h dark).
However, 10 h light and 10 h dark does not result in entrainment to a 20 hr day
Instead, results in free-running with sporadic entrainment attained at irregular intervals.
In hamsters, wheel running can be entrained to the following range: 18-26 hrs.

Front 29

General Characteristics of Biological Clocks and Rhythms
Independence from behavioral feedback. Describe.

Back 29

Suppose a hamster housed in DD is expressing a 24.25 h cycle of wheel running onset.
Then, the hamster's wheel is locked for 10 days.
Then it is unlocked.
What time will the hamster begin to run?
2 possible predictions:
1) 15 min after last time-- suggesting that the clock suspended time-keeping while the rhythm of wheel running activity was not being expressed
2) 150 min after last time suggesting that the clock continued to run even in the absence of behavioral feedback. Prediction #2 is the correct answer.

Front 30

General Characteristics of Biological Clocks and Rhythms
Biological clocks are found at every level of organization within an organism. Describe.

Back 30

Single-celled organisms possess circadian rhythms so the machinery necessary to generate a rhythm must exist at the level of individual cells.
So, in multi-cellular organisms, does every cell possess its own biological clock?
Perhaps, but in multi-cellular organisms, it appears as if these individual biological clocks have been organized into some sort of hierarchical fashion with feedback imposed from above.
E.g., cells taken from hamster adrenals and maintained in culture will free-run at different rates. In the intact hamster, they free-run at the same rate.

Front 31

Circadian "master" clocks have been isolated after demonstrating that lesions eliminate circadian rhythms. What are examples of some of these ciradian clocks?

Back 31

Eyes of amphibians
Pineal glands of fish, reptiles, and birds
Suprachiasmatic nuclei (SCN) of the anterior hypothalamus in mammals

Front 32

Suprachiasmatic nuclei (SCN) of the anterior hypothalamus in mammals is considered a circadian "master" clock. Discuss some of the features of the SCN.

Back 32

Slices from the SCN maintain circadian rhythms of electrical activity
SCN transplants cause recipient's rhythm to match that of donor
Environmental light entrains oscillations of SCN

Front 33

SCN are the master clocks
of which animals?

Back 33

mammals

Front 34

What pathway for output from the master clock has been extensively studied in mammals?

Back 34

SCN-->PVN-->MFB-->SCG-->Pineal pathway


(where neural information is transduced into a hormonal message)

Front 35

Are there different clocks for rhythms of different lengths or are longer rhythms simply the result of the multiplication of shorter rhythms?

Back 35

E.g., is the 4-day (96 h) estrous cycle of a hamster the result of a 4-day clock cycling once or a 1-day clock cycling 4 times?
Evaluated in studies of free-running rhythms in female hamsters.
Phase shifts of entrainment were accompanied by proportionate shifts in estrous cycle (light- dark cycle changed to 25 h, then estrous cycle changed to 100 h-- if reduced to 20 h, then estrous cycle switched to 80 h)

Front 36

Is the 4-day (96 h) estrous cycle of a hamster the result of a 4-day clock cycling once or a 1-day clock cycling 4 times?

Back 36

Evaluated in studies of free-running rhythms in female hamsters.
Phase shifts of entrainment were accompanied by proportionate shifts in estrous cycle (light- dark cycle changed to 25 h, then estrous cycle changed to 100 h-- if reduced to 20 h, then estrous cycle switched to 80 h)

Front 37

Day length affects

Back 37

melatonin

Front 38

Biological rhythms affect

Back 38

physiology

Front 39

A zeitgeber is any environmental factor that provides a temporal cue. In the absence of a zeitgeber, you'll see what type of activity?

Back 39

No zeitgeber means free running activity

Front 40

Without zeitgebers, behaviors that show rhythm are driven by..

Back 40

the biological clock

Front 41

entraining

Back 41

process by which brief exposure to light resets the clock

Front 42

It is easier to phase ___ than to phase ___

Back 42

easier to phase DELAY than to phase ADVANCE

Front 43

What is happening when you phase Delay?

Back 43

retraining to light is occuring later

phase delay occurs when you travel east to west

Front 44

Phase delay occurs when you travel from __ to __.

Back 44

east to west.
When this occurs, the subjective day is lengthened.

Front 45

Traveling from west to East is an example of phase ___.
Is this easy or difficult?

Back 45

west to east = advance.
This is very difficult.
Subjective day is shorter

Front 46

What is a skeleton period?

Back 46

A skeleton period is a light dark cycle where dawn and dusk are represented by 2 separate light periods

For example,
A regular period would be 15L:9D
but a skeleton period would be
15L:1D:7L:1D

Front 47

Define subjective day.

Back 47

Subjective day is when you are active; what you usually do during the light per

Front 48

When you sever the SCN and activity changes, what is this called?

Back 48

splitting

Front 49

What does tau allow you to determine?

Back 49

Tau allows you to determine circadian time.

Front 50

Discuss potential values of tau.

Back 50

Tau NEVER equals 24.

Taus are either <24 or >24.

Front 51

What information explains how we entrain to 24 hours?

Back 51

late/early subjective night differences explain how we entrain to 24 hours.

Front 52

Why does the dead zone appear on a prc and how is it represented graphically?

Back 52

The dead zone occurs because any light observed during the subjective day doesn't effect activity.

The dead zone is represented as a flat, horizontal line on the PRC.

Front 53

Under what circumstances does a phase delay occur?

Back 53

Phase delays occur if we delay the onset of the light flash such that the light flash occurs early in the subjective day (might want to ask about this)

Front 54

To cause a phase advance, what should you do?

Back 54

Put light at the end of the subjective night

Front 55

What will happen if you have add light during subjective day?

Back 55

Nothing. Addition of light during the subjective day has no effect.

Front 56

How are phase delays and phase advances represented on a phase response curve?

Back 56

delays = valleys
advances = peaks

Front 57

If you have light at the beginning of subjective night..

Back 57

you'll sleep longer the next day (I think that this would represent phase delay).

Front 58

If you have light at the end of subjective night..

Back 58

you'll go to bed earlier
This is phase advancing.

Front 59

phase delay

Back 59

occurs if we delay the onset of the light flash

Front 60

Why doesn't tau equal 24?

Back 60

It's not easy to entrain to changing day lengths.
Tau is either less than 24 or greater than 24

Front 61

What are three inferences that we can make from the phase response curve?

Back 61

1. there must be a max T cycle
2. Minimum T is 20-22 hours
3. when you use brief light pulses, a process called masking occurs

Front 62

What is a t cycle?

Back 62

the length of day

Front 63

What are the min and max t cycles (lengths of day)?

Back 63

min 20-22
max 27 hrs

Front 64

Describe Aschoff's rule.

Back 64

1. Nocturnal animals have constant dark taus (per of circad rhythm) and constant light taus. Diurnal animals have DD taus> LL taus.
2. Period of tau shortens as light intensity increases

Front 65

If you have a long tau (or if you extend the length of tau)..

Back 65

you will become active later and later

Front 66

When is melatonin secreted?

Back 66

at night

Front 67

If you cut the neural connection between the optic lobes and the rest of the nervous system in a cockroach, what happens?

Back 67

the ability to generate circadian rhythms is lost.

Thus, cockroach rhythm generation is neural, not endocrine.

Front 68

What kind of pacemaker is the SCN?

Back 68

The SCN is a master pacemaker.

Front 69

What innervates the SCN?

Back 69

the retinohypothalamic tract

Front 70

Mammals are the only creatures that don't....

Back 70

have photoreceptors outside the eyes.

Front 71

When light is introduced, what neurotransmitter is released to the retinohypothalamic tract?

Back 71

glutamate

Front 72

Where does the IGL get its light information?

Back 72

the hypothalamus

Front 73

What is the fuction of the IGL?

Back 73

The IGL gets light info from the hypothalamus and entrains.

Front 74

What is the neurotransmitter associated with the IGL?

Back 74

neuropeptide Y

Front 75

What are the two inputs to the SCN?

Back 75

1. RHT
2. IGL

Front 76

What type of synapse is the RHT?

Back 76

RHT is monosynaptic.

Front 77

The IGL and the RHT both provide inputs to the SCN. Do they use the same pathway to do this?

Back 77

No. IGL uses a separate path.

Front 78

What are the functions of the IGL?

Back 78

entrainment, synchronization, nonphotic cues (like motor activity).

Front 79

What is one of the regulatory functions of the SCN?

Back 79

The SCN is able to regulate the secretion of melatonin

Front 80

What are the sources of output from the SCN?

Back 80

1. ant hypothal
2. lat and dorsal medial hypothal
3. IGL
4. lat septal nucleus = motivates agression

Front 81

If you take the SCN out of its host, what will happen to the mechanism by which it fires?

Back 81

Nothing. If you take out the SCN it will still fire in a rhythmic manner.

Front 82

What is true of cells from the same SCN that are separated from one another?

Back 82

Cels from the same SCN that are separated from one another are NOT phase locked.

Front 83

When you transpant the SCN of one hamster into another hamster...

Back 83

You implant the phase relationship of the donor into the recipient.

Front 84

Do circadian rhythms require neural efferents?

Back 84

No. Circadian rhythms do not require neural efferents but some of the endocrine ones do.

Front 85

What are the functional characteristics of all biological clocks (ultradian, circadian, circannual clocks, etc.)?

Back 85

inherited, temp independent, relatively resistant to the influence of chemicals, Entrainment is limited to specific ranges, Independence from behavioral feedback
Biological clocks are found at every level of organization within an organism.
( in other words, Single-celled organisms possess circadian rhythms so the machinery necessary to generate a rhythm must exist at the level of individual cells)

Front 86

How have past investigators experimentally confirmed that the daily clock is indeed an endogenous timer?

Back 86

isolation experiments, I think
1.Jean Jacques d’Ortous de Mairan found that the tension–relaxation pattern of a heliotropic plant persisted when isolated from exogenous factors
2. Jurgen Aschoff, a medical doctor and physiologist, expanded on Kleitman's human isolation experiments.He concluded that humans — like the plants investigated by de Mairan — have endogenous circadian cycles.
3. Animals maintained in constant conditions aboard a spacecraft orbiting far above the earth, and presumably away from subtle geophysical cues, display biological rhythms with periods similar to those observed on earth.
Animals maintained in adjacent, but individual, cages in the absence of environmental cues display biological rhythms with slightly different periods, suggesting that they are not being driven by the same subtle geophysical cue;
The period (and phase) of the biological rhythms of one individual can be transferred to another individual by means of tissue transplants.

Front 87

What is the experimental evidence that the SCN is an important biological clock? What is the evidence that other extra-SCN clocks might also exist in mammals? --in other vertebrates?

Back 87

Circadian clocks have been isolated after demonstrating that lesions eliminate circadian rhythms
Other extra-SCN clocks that might also exist in mamals:
Eyes of amphibians
Pineal glands of fish, reptiles, and birds
Suprachiasmatic nuclei (SCN) of the anterior hypothalamus in mammals

Front 88

Flying squirrels become active at dusk, but dusk comes earlier and earlier in the fall and later and later in the spring. Yet, a flying squirrel follows these seasonal changes in timing of dusk. What is it about clock function that permits this flexibility? Explain.

Back 88

????????

Front 89

What is the pathway by which there is output from the clock?

Back 89

SCN-->PVN-->MFB-->SCG-->Pineal pathway

Front 90

Usefulness of biological clocks

Back 90

Synchronizing the activities of animals with their environments (including social)
To prepare for predictable events (e.g., winter, night, etc.)
Synchronizing the internal physiological and biochemical processes of animals
To promote efficient functioning

Front 91

Need to look up definitions of ultradian & infradian, be/c I have this approaching 9 hrs. Definitions I do have are on the back of this card

Back 91

Circadian, Revolution of planet
24 h (22-26 h)
Circatidal, Tides
12.4 h (11-14 h)
Circalunar, Phases of the moon
29.5 days (26-32 days)
Circannual, Seasons of the year
365.25 days (300-400 days)
Ultradian (shorter than circadian) rhythms
Infradian (longer than circadian) rhythms (persist in constant conditions, but do not correspond to any known geophysical cue)

Front 92

Circadian, Revolution of planet
24 h (22-26 h)
Circatidal, Tides
12.4 h (11-14 h)
Circalunar, Phases of the moon
29.5 days (26-32 days)
Circannual, Seasons of the year
365.25 days (300-400 days)
What is something that is important to note about all of these?

Back 92

The rhythms persist in the absence of the geophysical cue to which they are normally synchronized (entrained), with a period that approximates that of the geophysical cycle

Front 93

So, in multi-cellular organisms, does every cell possess its own biological clock?

Back 93

Perhaps, but in multi-cellular organisms, it appears as if these individual biological clocks have been organized into some sort of hierarchical fashion with feedback imposed from above.
E.g., cells taken from hamster adrenals and maintained in culture will free-run at different rates. In the intact hamster, they free-run at the same rate.

Front 94

Discuss the idea of the autonomous clock.(Peifer)

Back 94

He studied the daily movements of plants; he found that when these plants grew from the seed in continuous darkness they displayed no movement
However, when exposed to brief periods of illumination where light acts as a zeitgeber, the plant was easily able to induce such movement, and when returned to darkness, the plant possessed a persisting daily rhythm of leaf movement.
It was then postulated that plants and animals possess independent cyclical biochemical systems with inherited natural periods of oscillations and when other factors are constant, the period length is a characteristic of the genetic strain.
This period (rarely found to be exactly 24 hours) was called the "free running period” or “t”.

Front 95

If daily light signals are not important, then one might be tempted to conclude that some less obvious difference between night and day is cueing the plant and driving the rhythm of leaf movements (e.g., changes in temperature or other cues). Why is this not the case?

Back 95

the daily periodicity of plants housed in continuous illumination was slightly different from the exact 24-hour periodicity seen in plants kept under natural daily illumination.

Front 96

What conclusions could they make if the bees continued to feed at the same time in unchanging environmental conditions?
How did they know what time it was?

Back 96

some reliable clock to compensate for its constantly shifting ‘compass’.
, but I am not sure...does zeitgeist have anything to do with this?

Front 97

What does it mean when we say that the biological clock is temperature compensated?

Back 97

varies very little at different constant temperatures.

Front 98

Discuss the temporal organization of bio clocks.

Back 98

They control an organisms’ behavior and activities so that they occur at the "right time".
For example, clocks coordinate when males and females of the same species become fertile so that the period of maximum fertility coincides, thus establishing a breeding season.
In cyanobacteria (blue-green algae), there is both photosynthesis and nitrogen fixation but the latter process cannot occur in the presence of oxygen.
These processes therefore need to be separated.
Under the control of a biological clock these 2 processes are temporally segregated: photosynthesis occurs during the day, fixation during the night

Temporal Organization between Species.
Biological clocks function such that certain species are active, for example, during the day, while others are active during the night.
If a prey species is active during the night, then the clock of its predator will ensure it “wakes up" so it does not miss out on a potential meal.
In the same way, prey species may become active at times when the predators are usually not active (to avoid becoming a meal!)






Evolution of Biological Clocks


Anticipation of an Organisms Environment.
By registering local time and events (such as high and low tide), biological clocks allow organisms to prepare for and anticipate their environment.
Predictive Homeostasis is a good example of this –
an organism can activate certain systems preempting the changes that will occur in the environment e.g. in humans cortisol levels are raised before we wake up, increasing the metabolic rate so we have the energy necessary for the day ahead

Front 99

Describe Aschoff's rule

Back 99

Aschoff's rule


Nocturnal animals have DD taus less than LL taus, diurnal animals have DD taus greater than LL taus.


Period of tau shortens as light intensity increases in diurnal (day-active) animals and lengthens as light intensity increases in nocturnal (night-active) animals.

Front 100

Output from mamalian clock

Back 100

SCN-->PVN-->MFB-->SCG-->Pineal pathway

Front 101

Environmental factors such as light-dark cycles, clocks etc. that give clues as to external cycles are called...

Back 101

zeitgebers

Front 102

In the absence of any zeitgeber, behaviors that show rhythmicity are driven by an ...

Back 102

internal timing device - a biological clock.

Front 103

What happens if an animal is removed from exposure to zeitgebers?

Back 103

Many studies in humans and other mammals have shown that, in the absence of zeitgebers, i.e. when the biological clock is allowed to free-run, activity has a period of 22.5 to 26 hours.
This period is incredibly robust, it does not deviate by more than a few minutes in a year and is unaffected by food/water intake, exposure to LSD, removal of endocrine glands or electroconvulsive shock (Richter, 1967).
However the clock can be reset by brief exposure to light - a phenomenon called entraining.

Front 104

entraining is...

Back 104

resetting the clock by brief exposure to light

Front 105

In the absence of zeitgebers, the biological clock will..

Back 105

free run

Front 106

There is a number of ways in which the environment or changes in behavior can make the internal clock 'out of synch' with the external world.
Sudden mismatches between 'subjective' time and the external LD cycle are called....

Back 106

phase shifts

Front 107

what are some of the situations in which phase shifts occur?

Back 107

jet lag and ‘rapid rotation’ shift work.

Front 108

When traveling from East to West the subjective day is _____, re-entraining to light occurs _____ and adaptation is ________.

Back 108

When traveling from East to West the subjective day is lengthened, re-entraining to light occurs later (delay shift) and adaptation is easier (although it can still take several days

Front 109

Discuss skeleton photoperiods

Back 109

A light-dark cycle in which dawn and dusk are represented by two separate light periods, e.g, LDLD1: 7: 1: 15 (the skeleton of LD9 : 15 or of LD17 : 7)
If the two light periods are of equal length, then the skeleton is considered to be symmetric

Front 110

Subjective Day

Back 110

The time during which the organism exhibits the behavior usually associated with light in an LD cycle

Front 111

Splitting

Back 111

Hamsters housed in LL
show ‘splitting’ of their

locomotor activity patterns.

Often the two circadian
oscillations appear to free-run with different t’s.









Splitting


Two oscillators
Pittendrigh and Daan introduced the hypothesis of a pacemaker consisting of two coupled oscillators.
Their proposal of an evening oscillator (E) and a morning oscillator (M) was based on the splitting of activity rhythms in hamsters under constant conditions.
Recently, Illnerova and Vanecek explained the different sensitivity of onset and offset of N-acetyltransferase activity towards light pulses with this model of two coupled oscillators

Front 112

circadian time

Back 112

To understand how light entrains free-running circadian rhythms

Front 113

CT-12

Back 113

CT-12is defined as the onset of locomotor activity (or beginning of subjective night)

Front 114

To convert RT to CT (RT=CTxt/24)
To convert CT to RT (CT=RTx24/t)

Back 114

To convert RT to CT (RT=CTxt/24)
To convert CT to RT (CT=RTx24/t)

Front 115

Imagine that one hamster t =27.00 h and another has t = 14.00 h (impossible)
Both are free-running in DD
A light pulse is given 4 real hours after wheel-running starts
Determine the CT for each animal…

Back 115

Animal #1 CT=RTx24/t = 4 x 24/27= 4 x .89 = 3.56 hCT = CT 15.56 (early subj night)


Animal #2 CT=RTx24/t = 4 x 24/14= 4 x 1.71 = 6.86 hCT = CT 18.86 (late subj night)

Front 116

Because of its short t, Animal #2 has a much shorter subjective day than Animal #1. An individuals t is necessary to convert from RT to CT.

Back 116

Because of its short t, Animal #2 has a much shorter subjective day than Animal #1. An individuals t is necessary to convert from RT to CT.

Front 117

Phase Response Curve (PRC)

Back 117

Graphical representation of how specific light pulses phase shift free-running rhythms as a function of the time that they are given.

Front 118

Because of its short t, Animal #2 has a much shorter subjective day than Animal #1. An individuals t is necessary to convert from RT to CT.

Back 118

Because of its short t, Animal #2 has a much shorter subjective day than Animal #1. An individuals t is necessary to convert from RT to CT.

Front 119

Cockroach Optic Lobes


If one cuts the neural connection between the optic lobes and the rest of the nervous system,

Back 119

the ability to generate circadian rhythms in behavior is lost.

Front 120

If one cuts the neural connection between the optic lobes and the rest of the nervous system, the ability to generate circadian rhythms in behavior is lost.
By contrast, if one simply cuts the optic nerves that bring light information from the eyes to the optic lobes,

Back 120

By contrast, if one simply cuts the optic nerves that bring light information from the eyes to the optic lobes, the locomotor activity rhythm remains intact, but it free-runs under all lighting conditions. The hypothesis that emerges from these results is that the oscillator is somewhere within the optic lobes

Front 121

The idea that the connection of the pacemaker to the rest of the nervous system is neural is reinforced by

Back 121

the lack of rhythmicity if the brain is excised and simply implanted in the abdomen

Front 122

Terry Page found that if one studied roaches with transected optic lobes left in situ for about 40 days, all of the arrhythmic roaches became rhythmic again with no further intervention.
The period of the restored rhythm was similar to that of the original rhythm.
Page first showed that the restoration of rhythmicity was coincident with and dependent on the regrowth of fibers from the optic lobes to the rest of the brain.
The restoration of behavioral rhythmicity is coincident with the restoration of light-evoked responses in the rest of the brain, which depend on an intact neural route from the retina to the optic lobe to the protocerebrum. What does all of this indicate?

Back 122

These results indicate that the oscillator in the optic lobe continues to function after being separated from the brain and that the output mechanism from the pacemaker to the driven systems in the brain can regenerate spontaneously.

Front 123

eyes

Back 123

are the only photoreceptors in mammals

Front 124

Characteristics of SCN

Back 124

. bilateral, paired nuclei
2. a cluster of about 10,000 neurons
3. different cell types
4. presence of neuropeptides

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Glutamate is the main neurotransmitter in the...

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RHT---GLU is released at synapses in SCN in response to light stimulation

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Intergeniculate leaflet (IGL) as an additional source of photic information for entrainment of SCN---projections from IGL to SCN release......

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neuropeptide Y

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INPUT into SCN -2 ways

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Monosynaptic pathway: Retinohypothalamic Tract (RHT

The second passage is the intergeniculate leaflet (IGL)

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Monosynaptic pathway: Retinohypothalamic Tract (RHT

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This derives from specialized photoreceptors that sense light.
The RHT connects to the core of the SCN.
The detection of light is transmitted via the RHT.

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The second passage is the intergeniculate leaflet (IGL)

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Receives data directly from the retina, but the route separates from the RHT.
The IGL terminates in the geniculo-hypothalamic tract (GHT)
The IGL path appears to play an important role in the entrainment, synchronization, by non-photic zeitgebers such as motor activity

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the SCN is able to regulate the production of...

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melatonin

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Where is melatonin secreted?

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pineal gland

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Lesions of the SCN abolish...

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circadian rhythms

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Types of evidence that SCN is circadian pacemaker:

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a. SCNx (destruction of SCN by lesion)----> arrhythmicity
b. electrical or chemical stimulation of SCN----> phase shifts
c. rhythm of neural firing activity and 2DG uptake in SCN in vivo
1. rhythm of neural firing persists after surgical isolation of SCN from neural connections with brain
2. rhythm of neural firing persists in vitro
3. rhythm of 2DG (2-deoxyglucose) uptake indicates rhythm in metabolic rate

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SCN transplant studies

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1. tau mutant hamster has taudd = 20 h (very different from wild-type hamster taudd, which is very close to 24 h
2. lesion SCN of wild-type hamster and implant SCN taken from tau mutant hamster---transplant restores rhythm and tau = 20h, similar to tau of donor hamster)
3. lesion SCN of tau mutant and implant SCN taken from wild- type hamster---rhythmicity is restored and tau is close to 24h (again like that of donor)
4. transplanted SCN restores locomotor activity rhythm, but rhythm can no longer be entrained to light---probably because connections from RHT to SCN are not restored
5. transplanted SCN does not restore pineal melatonin rhythm---neural connections (output) from SCN to pineal are not restored

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Seasonal Gonadal Response is or is not Restored by SCN Transplants

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is not

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Circadian Behavioral Rhythms do or do not Require Neural Efferents

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DO NOT

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SCN Transplants Do or Do Not Restore
the Glucocorticoid Rhythm

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DO NOT

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What can be said about the structure of the SCN?

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It is structurally heterogenous.

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Two main hormones that carry temporal information are...

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melatonin and cortisol

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When does the Peak daily cortisol concentrations occur?

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Peak usually occurs just prior to or immediately after awakening,
Coincides with the onset of locomotor activities in the morning.
Programmed elevation of blood levels of cortisol increases blood pressure and cardiac output prior to the active phase of the day.
We know that the increased cortisol concentrations are not driven by the increased activity levels, because the same circadian rhythm is observed in bedridden patients under constant conditions (Aschoff, 1965).

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Female hamsters display an interesting pattern of activity onset that has been termed “scalloping.” Describe.

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Every 4th night, coincident with estrus, females show a spontaneous phase advance in their activity onset






Estrogen Phase Advances Tau







Estrogens shorten tau


Hamsters are solitary creatures and it has been speculated that the earlier onset of locomotor activity during estrus increases the female’s odds of locating a male.
The scalloping pattern is eliminated by ovariectomy.
Furthermore, estradiol treatment of free-running, ovariectomized hamsters or rats reduces the period of locomotor activity onset, suggesting a direct effect on the clock itself

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Progesterone does what to the period of circadian rhythms?

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Progesterone lengthens the period of circadian rhythms, possibly by counteracting the effects of estradiol