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1 - Times of our lives, Wright K..doc

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David Rollo

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Article #1 – Time of Our Lives • Biological clocks help keep brains on schedule • Time as “primordial context” -- John Gibbon – fact of life that has been felt by all organisms in every era • cellular chronometers may decide when your time is up • Pacemakers – some are accurate and inflexible others are less reliable but can be controlled consciously – insight into aging and disease o some are set by planetary cycles, others by molecular ones • Cancer, parkinson’s disease and seasonal depression and attention deficit disorder linked to defects in biological clocks • Interval timing – marks time spans such as how fast you may have to run to catch a ball – enlists higher cognitive powers of the cerebral cortex (brain centre that governs perception, memory and conscious thought)—allows you to make judgments of time • fMRI (functional magnetic resonance imaging) (Rao’s studies): brain structures involved in task of deciding which interval is longer consume more oxygen than those that are not involved – fMRI records changes in blood flow and oxygenation every 250 milliseconds – BASAL GANGLIA ACTIVATED FIRST • BASAL GANGLIA – prime suspect in search for interval-timing mechanism – striatum (area in basal ganglia) has population of well connected nerve cells that receive signals from other parts of brain – gathers info from different neuron in another area – thousands of neurons converge on a single neuron • Striatal spiny neurons – interval timing memory • Cortical oscillators – oscillating on their own schedules connect to striatum through millions of signal carrying arms so the spiny neurons can eavesdrop on convos until something gets the corticals attention and stimulation causes the corticals to fire at the same time causing spike in electrical output 300 ms later • End of interval  part of basal ganglia called substantial nigra sends burst of dopamine to striatum which induces spiny neurons to record pattern of cortical oscillations they receive at that moment – TIME STAMP • Spiny neuron learns time stamp of interval for given event – both firing of cortical starting gun and burst of dopamine at the at the beginning of the interval which tells spiny neurons to track patterns of cortical impulses that follow • When spiny neurons recognize time stamp of end of interval they send an electrical pulse from striatum to thalamus which communicates with cortex and higher cognitive functions like memory and decision making take over • TIMING MECHANISM – loops from cortex to striatum to thalamus and back to cortex • If Meck is right and dopamine bursts play important role in framing a time interval then diseases and drugs that affect dopamine levels should disrupt the loop – and this is what they have found • Patients with untreated Parkinson’s disease – release less dopamine into striatum and clocks run slow – underestimate duration of time intervals • Marijuana lowers dopamine availability and slows time • Cocaine and methamphetamine increase availability of dopamine and make interval clock speed up so time expands – adrenaline and other stress hormones work the same way (a second can feel like an hour during unpleasant situations) • Deep concentration or extreme emotion – flood system or bypass it – time may stand still • Interval clock can be trained to greater precision – eg Musicians and athletes can improve timing through practice Somatic Sundial • flexibility of interval timing – start or stop it at will or ignore it o it can work subliminally or conciously • precision of interval timers 5-60% -- don’t work well if your distracted or tense and errors get worse as intervals get longer • interval timers have a precision from 5-60% - don’t work well when distracted or
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