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Lecture

Timing


Department
Psychology
Course Code
PSY260H1
Professor
Martin Ralph

Page:
of 13
Timing
It is absolutely essential for organisms to time what they do; their physiology, their
chemistry, their behaviour, etc, with their environment. All organisms need to be able to
predict these sorts of things: when things will happen in your environment, what we want
out of the world, when we can get it. When we can get these things changes by season, by
day, and by moment. We are bound by our ability to time things. If you have to run after
game to eat, for example, by being able to predict the presence of a predator/pray and
being able to time and outrun them, we gain safety, shelter, food, etc.
Reproduction is also timed in some animals. Some of these things need to be built into
the organism so that the timing is correct. Other organisms need to time their own cycles
in order to work with the cycles of other animals. For example, if a certain bird does not
time how he eats or reproduces, his food supply may run out (because he does not give it
time to reproduce, etc).
Timing behaviour can also be learned.
Why would animals need to predict the occurrence of significant events (or
conditions)?
• safety/predation
food/prey
climate/seasonality
Reproduction
What mechanisms could be used to predict timing of events or conditions?
Clocks: measured phase
Timers: measured duration
These are different mechanisms that help us time things.
These are actually biological devices and the mechanisms of clocks and timers mimic
these effects; they provide an external means of timing.
Time is measured duration and clocks measure phase.
These mechanisms can be both learned and innate.
Assume that a lot of what is referred to here is innate.
Our innate timing cycles are usually correlated to the cycles of our environment; day,
night, seasons, etc.
Timing is also needed for mating rituals, etc.
Innate mechanisms are produced through evolutionary change. Learned mechanisms are
not derived from evolutionary change are needed to time the things that do not happen on
a regular basis (i.e., crossing the street without getting hit by a car, etc).
We do have an internal mechanism for predicting things that should happen throughout
the day. This can demonstrated with animal research; if a certain something happens
during the day in the animals’ environment, that animal will predict it to happen at the
same time the next day. This can happen with just one experience or it can happen after a
few ‘trials’. You unconsciously and sometimes consciously, pay attention to the time of
day certain events happen; we do this in order to be able to predict things in our future,
and this prediction may last for weeks.
Is the timing innate or learned?
Innate mechanisms are useful for predicting regular events or changes
1. Events tied to the physical cycles of the environment (e.g. circadian, circannual
clocks)
2. Inter-individual signaling mechanisms (e.g. mating rituals, duetting)
Learned mechanisms are useful for predicting cue related events
(interval timers)
Combined mechanisms?
One of the mechanisms we have for timing things is interval timers. This is our ability to
understand how long something has taken. We do this without thinking.
The error we experience in this type of timing is directly proportional to the length of
duration (i.e., someone may say there will be at your house in half an hour, you have half
an hour to do other things, you know it’s only been five minutes, therefore you are not
wondering where they are, but if its been an hour, you will anticipate where they are; you
have a sense of half an hour). We do not think about the fact that we are doing it since we
are more attentive to why we are doing it (waiting for someone, etc). In animal models
we can set up experiments to look at this.
We can teach an animal, simply, with associative or classical conditioning; the light
comes on, and you teach the rat that 30 seconds after the light comes on, it can get food if
it presses a bar. The error they make is directly proportional to the trial takes (i.e., one
minute after light goes on, etc). Error is a scaling property and this points to the fact that
there is some mechanism in the brain that is counting this interval, that something with a
regular beat pattern to it is being tracked by the brain. This mechanism appears to be a
part of the dopamine pathway; there may be neurons that simply keep a regular beat and
neurons that count this. Manipulations to that pathway cause an increase in error of
estimation.
Interval timers:
1. Error is a scalar property of cue-response interval
2. Useful for short durations (sec – minutes)
3. Requires an oscillator and a counter
4. Nigrostriatal dopamine pathway appears to be involved
The caurdate putamen is needed for the counting or estimation of the intervals.
The Nucleus accumens is required for relative reward discrimination.
Most of the learning of time, at this level, has something to do with the activity in the
dopamine pathway. We also have another control over timing; the perception of time.
This perception of time (time dragging on, time skipping, etc) involves a different part of
the brain. The supplementary pre-motor cortex is the part of the brain involved in the
perception of time. If you pay attention to time during a task, your estimation of time is
that it is just long.
It also provides us with a memory of how long things take. An interesting feature of this
system is that, if we pay attention to time, time will drag on. If we have something to do
in that time, our perception of time will shrink. Now, if we wait a week and think back
about that situation, what we find is that we can’t remember what we did in that interval;
the only thing we remember is time doing nothing. Our perception of that time goes away
and we do not remember how long something took to do. When we are not paying
attention to time, we remember the events and the time seems to have slipped away. We
simply have a memory of it taking a long time.
Circadian oscillators are responsible for Time Memory
How do we learn that something happens at particular times of day; is it implicit or
explicit? We will put it in the context of adaptive consequences.
What is the basic idea: animals learn and remember things that happen during certain
times of day.
This requires a circadian oscillator; this is an oscillator that cycles in about 24 hours. This
timer is set by the conditions of our environment. When certain events happen, that timer
is set. This timer tells the day that something significant has occurred and that it will most
likely occur at the same time, the next day. You either predict nothing in this situation or
you predict where bad things and good things happen. When is also crucial to this
prediction.
1. Animals learn, remember, and recall the time of day that significant conditions
occur.
2. In mammals, this ability requires a circadian oscillator that is set by significant
conditions during the day and night.
3. The oscillator is entrained by the suprachiasmatic nucleus.
4. The oscillator is sensitive to changes in
dopamine activity.
5. The oscillator represents the family of circadian devices that determine the day-
to-day patterns of physiology and behaviour
The suprachiasmatic nucleus is where this biological clock resides. This is in the
hypothalamus; in the base of the brain. It produces daily rhythms in all organisms (plants,
animals, etc).
Timing is sensitive to dopamine activity. This clock that is set to significant things in the
environment can be reset using dopamine affecting drugs.