timing

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 hour 29 hour

“Just Right”“Too Hot” “Too Cold”

Bolles & Stokes (1965)

4am 8am Mid-day 4pm 8pm Midnight

Food

Light Dark

Periodic Timing

11pm 4am 8am Mid-day 4pm 8pm

Food

Light Dark

Paris

New York

Oscillators (Long Intervals)

Example

RRR RRG GGGGGRGRGGRRRGGRGR

432100

10

20

30

40

50

60

Adapted from Roberts (1982)

Five-second blocks

Mea

n re

spon

ses

per

min

ute

Interval Timing

Peak Procedure

141210864200

10

20

30

40

50

60

Five-second blocks

Mean r

esp

onse

s per

min

ute

One vs. Two Seconds

Absolute Difference = 1Weber’s Ratio = 1/2 = 0.5

Weber’s Law

Prediction: Very Easy

Nineteen vs. Twenty Seconds

Absolute Difference = 1Weber’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 s5 s?

2 s

8 s4 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

BisectionTesting

Scalar Timing

N

n=N x T n*=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)

BehaviorSequence: P M T L C

P = PeckM = MoveT = TurnL = LookC = Coo

Start Stop