Chapter 6: Metacontrastand Motion Perception (pp. 219-233 )

Thomas OttoEDNE 016: Dynamic Vision23.01.2007

Visual persistenceA percept persists for some time after the termination of the stimulusVisual persistence is about 120 ms under daylight

Motion smearBurr (1980)Moving objects should be perceived like in a photograph with a 125 ms shutter speed

Suppression of persistenceThe amount of motion smear is far less than may be expected from visual persistenceBurr (1980)

Suppression of persistence & metacontrastA moving stimulus fulfills the definitionof a metacontrast mask Suppression of persistence & metacontrast are similar from the perspective of PHENOMENOLOGY

PhenomenologySuppression of persistence & metacontrast are similar in: - Dependence on luminance

- Spatial and temporal separation

- Eccentricity

Motion de-blurring modelsModels of motion de-blurring can be viewed as models of metacontrast

There are mainly two classesbased on: - motion compensation and fusion

- lateral inhibition

Motion compensationSpatio-temporally oriented receptive fieldsBurr, Ross & Morrone (1986)

Lateral inhibitionThe RECOD modelPurushothaman, Ogmen, Chen & Bedell (1998)

The RECOD model & an isolated targetPurushothaman, Ogmen, Chen & Bedell (1998)The RECOD model predicts extensive smearfor isolated targets

The RECOD model & multiple targetsPurushothaman, Ogmen, Chen & Bedell (1998)The motion smear is basically removed by the transient activity of nearby stimuli

Isolated targetAn isolated target appears to be extensively smearedChen, Bedell & Ogmen (1995)

Confusing summary paragraphThese findings provide evidence against models where motion plays a causal role in metacontrastBreitmeyer & Ogmen (2006)

Isolated targetA velocity of 10 deg/scorresponds to a SOA of about 5 ms given a target-mask separation of 200

Confusing summary paragraph Metacontrast can improve the clarity of form perception by suppressing the smear of moving objects

A careful parametric analysis shows thatmetacontrast and motion involve different mechanisms

Breitmeyer & Ogmen (2006)

SummarySuppression of persistence and metacontrast are similar from the perspective of

STIMULI and PHENOMENOLOGY

There might be ONE mechanism responsible for both phenomena!

The end Thanks for your attention!

Transient and sustained activity

Experimental data vs. model prediction