Timing Periodic Timing –Cyclical behaviour controlled by 24 hour clock time or (circadian) Interval Timing –Stopwatch timing

4pm 8pm Midnight 4am 8am Mid-day ACTIVITY Light off Light on Periodic Timing Controlled by daily time or by light off?

Roberts (1965) Activity cycle slightly less than 24 hours in constant dim light Restoring visual cues produces a gradual shift back to correct time. Entrainment: light acts as a zeitgeber (resets 24 hour clock)

Bolles & Stokes 24 hour19 hour29 hour “Just Right”“Too Hot”“Too Cold”

Bolles & Stokes (1965)

4am 8am Mid-day 4pm 8pm Midnight Food Light Dark Periodic Timing 11pm 4am 8amMid-day 4pm8pm Food Light Dark Paris New York

Oscillators (Long Intervals)

Example RRRRRGGGGGGRGRGGRRRGGRGR

Interval Timing

Peak Procedure

One vs. Two Seconds Absolute Difference = 1 Weber’s Ratio = 1/2 = 0.5 Weber’s Law Prediction: Very Easy

Nineteen vs. Twenty Seconds Absolute Difference = 1 Weber’s Ratio = 1/20 = 0.05 Weber’s Law Prediction: Very Hard

Long or Short? 2 s 8 s Choose Lever 1 Choose Lever 2 2 s 8 s 5 s? 2 s 8 s 4 s? 4 is twice 2 8 is twice 4 (2 + 8) / 2 = 5 Absolute Ratio ((2)(8)) 1/2 = 4

Temporal Discrimination Long CS Short CS

Absolute = (8+2) / 2 = 5 Relative = ((8)(2)) 1/2 = 4 Bisection Testing

Scalar Timing N n=N x Tn*=N x T x K N x T b = about 2/3

Scalar Timing How do remember times scale to real time? –Error is relative error is a constant proportion of the timed interval called scalar timing –So, if the memory of time is just right, k = 1.0 too early, k < 1.0 too late, k > 1.0

Dopamine Clock Speed Theory –Agonists (speed clock, left-shifted, K < 1.0) –Antagonist (slowed clock, right shifted, K >1.0) Threshold Theory –Agonists lower threshold (impulsivity) –Antagonist increase threshold (sluggish) Striatum Theory –D1 affects general motivation (number of responses) –D2 affects response timing (time of peak)

Some Data

Parkinson's Dopamine D1 depletion causes reduced motivation to respond (decrease in amount of responding) Dopamine D2 depletion causes a leftward shift (late timing) External stimulus might replace internal cues from the striatum

Learning-to-Time (LET) Behavior Sequence: PMTLC P = Peck M = Move T = Turn L = Look C = Coo StartStop