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Martin Ralph

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 predatorpray 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 learnedWhy would animals need to predict the occurrence of significant events or conditionssafetypredation foodprey climateseasonality ReproductionWhat mechanisms could be used to predict timing of events or conditions Clocks measured phase Timers measured durationThese 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 innateOur 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 ie 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 learnedInnate mechanisms are useful for predicting regular events or changes1Events tied to the physical cycles of the environment eg circadian circannual clocks2Interindividual signaling mechanisms eg mating rituals duettingLearned mechanisms are useful for predicting cue related events interval timers Combined mechanismsOne 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 ie someone may say there will be at your house in half an hour you have half an hour to do other things you know its 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 ie 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 1Error is a scalar property of cueresponse interval2Useful for short durations secminutes3Requires an oscillator and a counter4Nigrostriatal dopamine pathway appears to be involvedThe caurdate putamen is needed for the counting or estimation of the intervals The Nucleus accumens is required for relative reward discrimination
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