Neural mechanisms for timing visual events are spatially selective in real-world coordinates. David Burr, Arianna Tozzi, & Concetta Morrone

Plan Brief discussion of event duration Brief discussion of event duration Method Method Results Results Your observations Your observations My observations My observations

“Accurate timing over the subsecond scale is essential for a range of perceptual and motor activities”? It is easy to see the adaptive value in sensitivity to luminance contrast, or colour It is easy to see the adaptive value in sensitivity to luminance contrast, or colour The auditory system uses duration differences of the order of a few msec to distinguish phonemes (“boten” vs “boden”) The auditory system uses duration differences of the order of a few msec to distinguish phonemes (“boten” vs “boden”) Also sound localisation Also sound localisation Roberts (1981) - duration is a controlling variable in rat foraging behaviour (but order of many seconds) Roberts (1981) - duration is a controlling variable in rat foraging behaviour (but order of many seconds) What about 100’s of msec to 2 seconds? What about 100’s of msec to 2 seconds? Motor timing (tap finger with metronome) Motor timing (tap finger with metronome) Perceptual timing? Perceptual timing?

Prolonged exposure to motion reduces perceived speed, and produces a directional aftereffect when viewing a static test Prolonged exposure to motion reduces perceived speed, and produces a directional aftereffect when viewing a static test Does motion adaptation produce a change in the perceived duration as well as the perceived speed of a test stimulus? Does motion adaptation produce a change in the perceived duration as well as the perceived speed of a test stimulus? Does this effect remain fixed to a specific location in Does this effect remain fixed to a specific location in Retinal coordinates? Retinal coordinates? Spatiotopic coordinates? Spatiotopic coordinates?

800 msec Test grating retinotopically same as adapter 600 msec 500 msec Probe 200 – 800 msec: judge shorter or longer than test Adapting to reversing directions of motion produces no directional after effect, but does reduce perceived speed Probe presented at a location that differed retinotopically and spatiotopically from the adapted location to insure its perceived duration was not affected by the adaptation (so should be veridical comparison stimulus)

800 msec Test grating spatiotopically same as adapter Probe 200 – 800 msec: judge shorter or longer than test

800 msec Control (different retinotopic & spatiotopic) Probe 200 – 800 msec: judge shorter or longer than test

Full (no saccade, so retina and spatio same) 800 msec blank 600 msec test Probe 200 – 800 msec: judge shorter or longer than test No explicit statement about probe position in Full, so I assume it was in the same screen position as other conditions. If so, the probe has greater eccentricity in Full than other conditions. It was not at position C, as this was also used for test stimuli in the same session.

Adaptation reduces apparent speed of test at adapted location, and apparent duration increases with stimulus speed Adaptation reduces apparent speed of test at adapted location, and apparent duration increases with stimulus speed Physical speed of test 10 deg per sec Physical speed of test 10 deg per sec Retinotopic 7.1, Spatiotopic 9.3, full 5.2 Retinotopic 7.1, Spatiotopic 9.3, full 5.2 Probe speed was matched to apparent test speed to negate this effect Probe speed was matched to apparent test speed to negate this effect Also did retinotopic, spatiotopic, and full (combined) without adaptation Also did retinotopic, spatiotopic, and full (combined) without adaptation This ruled out the possibility that the effects were caused by the saccade This ruled out the possibility that the effects were caused by the saccade

Neither (control) Full (no saccade) Spatiotopic Retinotopic

Why is spatiotopic effect bigger than spatiotopic plus retinal? Could it be something to do with the greater eccentricity of the probe in the combined (full) condition? Could it be something to do with the greater eccentricity of the probe in the combined (full) condition? Perhaps visual event duration reduces with eccentricity? Perhaps visual event duration reduces with eccentricity? Decreasing the apparent duration of the probe would mean that a greater physical probe duration would be perceived as equal to the test, consistent with the results. Decreasing the apparent duration of the probe would mean that a greater physical probe duration would be perceived as equal to the test, consistent with the results.

Reduced apparent duration of test Reduced apparent speed of test Retinotopic adaptation NOYES Spatiotopic adaptation YESNO Retin. and spat. adaptation YESYES NeitherNO Assume not

Percentage reduction in apparent duration of test relative to control

Control, Full, Retinotopic, Spatiotopic This is because apparent speed of test was slower than probe in same condition, for retinotopic only, and slower things have shorter apparent duration.

Why was there no time order error? The standard (600 msec) was always presented first The standard (600 msec) was always presented first This typically results in subjective shortening relative to the second presented duration (Allan, 1979) This typically results in subjective shortening relative to the second presented duration (Allan, 1979) Time perception research often used counterbalancing to avoid this Time perception research often used counterbalancing to avoid this Figure 2 (control) indicated that this did not occur (mean PSE 600 is veridical) Figure 2 (control) indicated that this did not occur (mean PSE 600 is veridical) This is odd This is odd

Why motion adaptation? What about other after effects? Johnston et al, (2006) report a similar experiment Johnston et al, (2006) report a similar experiment Adaptation to 20 Hz motion reduced the apparent duration of a 10 Hz test at same visual location Adaptation to 20 Hz motion reduced the apparent duration of a 10 Hz test at same visual location And decreased perceived speed of test And decreased perceived speed of test Adaptation to 5 Hz motion had only a minimal effect on duration of 10 Hz test Adaptation to 5 Hz motion had only a minimal effect on duration of 10 Hz test And increased perceived speed of test And increased perceived speed of test Apparent duration of 10 Hz flicker reduced by 20 Hz flickering adapter Apparent duration of 10 Hz flicker reduced by 20 Hz flickering adapter Johnston thinks temporal frequency is the thing that is linked to duration rather than motion per se Johnston thinks temporal frequency is the thing that is linked to duration rather than motion per se But, the experiments show that the effect on duration is independent of any effect on apparent temporal frequency But, the experiments show that the effect on duration is independent of any effect on apparent temporal frequency And, nobody has ruled out adapters that don’t have temporal frequency, e.g. luminance or contrast And, nobody has ruled out adapters that don’t have temporal frequency, e.g. luminance or contrast

This does not rule out a centralised timer Massive evidence for the role of the cerebellum in temporal processing, e.g. Massive evidence for the role of the cerebellum in temporal processing, e.g. ‘baden’ vs ‘baten’: bilateral (but not unilateral) cerebellar lesions remove ability to hear the difference ‘baden’ vs ‘baten’: bilateral (but not unilateral) cerebellar lesions remove ability to hear the difference Cerebellar patients have deficits in perceptual event timing as well as motor timing Cerebellar patients have deficits in perceptual event timing as well as motor timing The cerebellum contains topographic mapping (motor homonculus) The cerebellum contains topographic mapping (motor homonculus) Might it also contain visual spatiotopic topography, from which it supplies timing signals to different locations? Might it also contain visual spatiotopic topography, from which it supplies timing signals to different locations? Same signal might work for auditory space Same signal might work for auditory space