dipper function within, but not between, cues for depth and lateral motion andrew glennerster, rob...
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‘Dipper function’ within, but not between,
cues for depth and lateral motion
Andrew Glennerster, Rob Campbell
and Andrew Parker
University Laboratory of Physiology, Oxford
Lateral motion is easier to detect than motion in depth (Tyler 1971)
Left eye Right eye
Lateral motion is easier to detect than motion in depth (Tyler 1971)
Left eye Right eye
Tyler (1971) and Harris and Watamaniuk (1995)
Pedestal amplitude (arcmin)
Thr
esho
ld a
mpl
itude
(ar
cmin
)
0 0.1 1 10
0.1
0.01
1
10
100
DepthLateral
} Tyler (71)
DepthLateral
H & W (95)
}
Task: “which interval contained the signal?”
Interval #2
lateral pedestal + depth
}signal
Interval #1
lateral pedestal
e.g.:
Experimental details
Spatial• reference separation 30 arcmin• bar height 40’, width 2’• pixel size 0.45’ @ 2.65m • anti-aliased
Temporal• target bar oscillated sinusoidally • 3 Hz• each interval 1 s
Psychophysics• 2-interval forced choice• one signal amplitude per block• at least 250 trials per point• threshold: amplitude for d’ = 1
Apparatus• Wheatstone stereoscope
Detectlat on lateral pedestal
Pedestal amplitude (arcmin)
Thr
esho
ld a
mpl
itude
(ar
cmin
)
-2
-1
0
1
-2 -1 .5 -1 -0.5 0 0.5 1
0 0.1 1 10
0.1
0.01
1
10
RAAC
Pedestal
Ped + lat
Detectdepth on depth pedestal
Pedestal amplitude (arcmin)
Thr
esho
ld a
mpl
itude
(ar
cmin
)
-2
-1
0
1
-2 -1 .5 -1 -0.5 0 0.5 1
0 0.1 1 10
0.1
0.01
1
10
RAAC
Pedestal
Ped + dep
Tyler (1971) and Harris and Watamanuik (1995)
Pedestal amplitude (arcmin)
Thr
esho
ld a
mpl
itude
(ar
cmin
)
-2
-1
0
1
-2 -1 .5 -1 -0.5 0 0.5 1 1 .5 2
0 0.1 1 10
0.1
0.01
1
10
RAAC
100
DepthLateral
} Tyler (71)
DepthLateral
H & W (95)
}
Normalised thresholds and pedestals
Pedestal amplitudenormalised by threshold of pedestal
Nor
mal
ised
thr
esho
ld a
mpl
itude
-1
-0.5
0
0.5
1
-1 -0.5 0 0.5 1 1 .5 2
RAAC
lat on lateral ped
10 100
0.1
10
dep on depth ped
Detectdepth on lateral pedestal
Pedestal amplitude (arcmin)
Thr
esho
ld a
mpl
itude
(ar
cmin
)
-2
-1
0
1
-2 -1 .5 -1 -0.5 0 0.5 1
0 0.1 1 10
0.1
0.01
1
10
RAAC
Pedestal
Ped + dep
Detect lat on depth pedestal
Pedestal amplitude (arcmin)
Thr
esho
ld a
mpl
itude
(ar
cmin
)
-2
-1
0
1
-2 -1 .5 -1 -0.5 0 0.5 1
0 0.1 1 10
0.1
0.01
1
10
RAAC
Pedestal
Ped + lat
Two subjects
Pedestal amplitude (arcmin)
Thr
esho
ld a
mpl
itude
(ar
cmin
)
-2
-1
0
1
-2 -1 .5 -1 -0.5 0 0.5 1
0 0.1 1 10
0.1
0.01
1
10
RAAC-2
-1
0
1
-2 -1 .5 -1 -0.5 0 0.5 1
0 0.1 1 10
JH
lat on lat ped
dep on dep ped
dep on lat ped
lat on dep ped
Conclusion
• A ‘dipper function’ within one domain (depth with depth pedestal or lat with lateral pedestal)
• In this case, pedestal and target are processed by the same mechanisms
•No ‘dipper function’ for depth with lateral pedestal (and only a small one for lat with depth pedestal)
• This suggests a lack of interaction between the processing of the two types of motion
Normalised thresholds and pedestals
Pedestal amplitude(normalised by threshold for pedestal cue)
Thr
esho
ld a
mpl
itude
(nor
m.
by u
nmas
ked
thre
shol
d)
-1
-0.5
0
0.5
1
-1 .5 -1 -0.5 0 0.5 1 1 .5 2
RAAC
dep on lateral ped
10 100
0.1
10
lat on depth ped
Normalised thresholds and pedestals
Pedestal amplitude(normalised by threshold for pedestal cue)
Thr
esho
ld a
mpl
itude
(nor
m.
by u
nmas
ked
thre
shol
d)
-1
-0.5
0
0.5
1
-1 .5 -1 -0.5 0 0.5 1 1 .5 2
RAAC
dep on lateral ped
10 100
0.1
10
lat on depth pednorm. by lat thresh
lat on lat ped