Holcombe:PositionAndMotion

SUPA Sydney University Perception and Action Lab Primer editing help refcard

• Biphasic Neuron Extrap
• A-V flash lag

Following on from [1]

• The idea of separate position representations (e.g. for first- and second-order motion as suggested by Pavan & Mather 2008) is really fascinating
• Nicolls,Mattingley,Berberovic,Smith,&Bradshaw(2004) review horiz/vert asymmetries we should check out for ideas
• To explain the Cai & Schlag smooth pursuit flash mislocalisation effect, Rotman, Brenner , Smeets (2005) suggest that efference copy motion signal is combined with (absent) retinal motion of flash to yield extrapolation. They present their whack-a-mole targets for variable duration and find the longer the exposure duration, the less mislocalization in the direction of the eye movement. They theorize that the reason is that the longer targets have more retinal motion opposite the pursuit, so this cancels the efference copy to eliminate the extrapolation. An alternative account is that longer exposure improves the integration with spatiotopically stationary landmarks, reducing the reliance on the retinotopic code. Since this does not help for targets moving with the eyes, would have to posit that stabilization thanks to landmarks doesn't happen with moving targets. But this seems unlikely. I would like to see 1) Mislocalization when target moves in orthogonal direction 2) Whether variability (presumably spatial in both cases, since we find spatial for Cai&Schlag), which might implicate growth of a spatial code.

Phenomenon	Spatial Bias	Temporal Bias	Spatial Variab	Temporal Variab	Foveo	attn effect	vectors sum	landmarks
Flash-lag	some	little	0	80ms	petal[1]	?	yes	less spatial var?
Cai	.5deg	0	?	0	??
Hazelhoff,[2]	0	large	??	discrepant Ss[3]	??	??	??
Whitney&Cav	signif	0	??	betting0	??	large
Frohlich	.5deg	0	?	0	fugal	large
deValois		large	miniscule	miniscule	fugal[1]
Motion adapt					fugal
timed buttonpress

Temporal variability might arise from:

1. Position shifting that increases with velocity, with constant noise added to velocity
2. Uncertainty in *when* the judgment was supposed to be made
3. For any effects caused by afferent latency (Hazelhoff?), variability in latency

deValois stands out as only temporal bias with spatial variability. Then why doesn't Cai and Frohlich have temporal bias? Only easy explanation would be the possibly-greater blur of the deValois stimuli, so we have to check that. Increasing eccentricity would also increase the spatial uncertainty[4] perhaps allowing temporal to manifest

Refs

1. Linares D and Holcombe AO. Position perception: influence of motion with displacement dissociated from the influence of motion alone. J Neurophysiol. 2008 Nov;100(5):2472-6. DOI:10.1152/jn.90682.2008 |

2. Hazelhoff FF, Wiersma H. Die Wahrnehmungszeit [The sensation time]. Zeitschrift für Psychologie. 1924;96:171-188

3. Linares D, Holcombe AO. Unpublished results. 2008

4. White JM, Levi DM, and Aitsebaomo AP. Spatial localization without visual references. Vision Res. 1992 Mar;32(3):513-26. DOI:10.1016/0042-6989(92)90243-c |