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Attentive tracking of multiple objects by humans and monkeys
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Summary
Can Monkeys Mentally Track Multiple Stimuli?
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1 2 30
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Monkey M
%Correct
Items Tracked
Monkey B
Items Tracked
Human (N=5)
Items Tracked
4 Items4 Items
5 Items5 Items
6 Items6 Items
8 Items8 Items
ChanceChance
1) Monkeys can track 2 and humans can track 3-4 items.2) Humans discriminate form changes better on targets.3) In V4 tracked stimuli elicit higher firing rates.4) This response increase is not measurably diminished when a second stimulus is tracked.
Jude F. Mitchell, Kristy A. Sundberg & John H. Reynolds
18 of 29 neurons show significantly higher firing for targets in either 1 of 4 or in 2 of 4 tracking tasks.
* Monkeys made saccades to all targets and to no distracters to receive reward.
* Trajectories were identical to the monkey task. * Rings were replaced with figure 8’s.* At the motion pause, all items changed from 8’s to E’s or 3’s, except one that changed to either a 2 or 5. * Subjects tracked the targets and also reported by key-press whether a 2 or 5 was present.
Attention Task:
V4 responses are enhanced for tracked items. The strength of modulation issimilar for tracking 1 or 2 targets.
References1. Pylyshyn ZW and Storm RW (1988) Tracking multiple independent targets: evidence for a parallel tracking mechanism. Spat Vis. 3(3):179-97.2. Sears CR and Pylyshyn ZW (2000) Multiple object tracking and attentional processing. Can J Exp Psychol. 54(1):1-14.
* Systems Neurobiology Laboratory, The Salk Institute for Biological Studies. Funding provided by NIH Training Grant in Cognitive Neuroscience (J.M.), NSF Graduate Research Fellowship (K.S.), and NEI grant 1R01EY13802 (J.R.).
Task: while maintaining fixation, track all cued stimuli.
4-8 identcal stimuli appear
(200ms)
1-4 targets cued by luminance increment
(200ms)
Stimuli move to pause position
(750 ms)
Stimuli pause(300ms)
Stimuli move tofinal position
(750 ms)Cue off(200ms)
Fixation point disappears: saccade
To ALL targets and NO distracters to earn reward
Yes.Monkeys can track at least 2 stimuli
Are tracked stimuli attended?
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Human (N=5)
Target
% C
orr
ec
t
1 of 4 2 of 4 1 of 5 2 of 5 1 of 6 2 of 6 3 of 6
Items Tracked
1 of 4 2 of 4 1 of 5 2 of 5 1 of 6 2 of 6 3 of 6
Items Tracked
Distracter
Yes.Discriminationis betterfor trackedstimuli.
*
Are V4 Neurons Modulated?
* The monkey attentively tracked targets far from the receptive field while oriented, colored gabors appeared throughout the visual field. The neuron’s spatial receptive field,color, and orientation tuning were computed on the basis of responses to the gabors..
Step 1) Mapping a V4 Unit’s Receptive Field
4 identical stimuli appear
(200ms)
1 targets cued by luminance increment
(100ms)
Stimuli move to pause position
(750 ms)
Stimuli pause(1000ms)
Stimuli move tofinal position
(750 ms)Cue off(100ms)
Fixation point off: saccade to
the target
Tracking Away from RF
Flashing Gabors+
RF
RFRF
RF
RFRF
RFRF
RFRF
RF
RF
RFRF
4 identical stimuli appear
(200ms)
1 targets cued by luminance increment
(100ms)
Stimuli move to pause position
(750 ms)
Stimuli pause(1000ms)
Stimuli move tofinal position
(750 ms)Cue off(100ms)
Fixation point off: saccade to
the target
Tracking Away from RF
Flashing Gabors+
RFRF
RFRFRFRF
RFRF
RFRFRFRF
RFRFRFRF
RFRFRFRF
RFRF
RFRF
RFRFRFRF
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24681012
24681012
24681012
24681012
24681012
24681012
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Response to Flashed Gabor Image In x,y Space broken down by Orientation
# of Repeats per x,y position
0-33 ms
33-67 ms
67-100 ms
100-133 ms
133-167 ms
167-200 ms
ResponseWindow
TIME
x
y+
x
y+
+1.5
-8.75
-6.25 +11.25
Fixation
x
y+
+1.5
-8.75
-6.25 +11.25
Fixation
Example Neuron:
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24681012
24681012
24681012
24681012
24681012
24681012
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# of Repeats per x,y position
0-33 ms
33-67 ms
67-100 ms
100-133 ms
133-167 ms
167-200 ms
TIME
y
x
Response to Flashed Gabor Image In x,y Space broken down by Color
+
Joint Color/Orientation Tuning for Example Cell:
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8
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0-33 ms
33-67 ms
67-100 ms
100-133 ms
133-167 ms
167-200 ms
Response Window
TIME
SpatialResponse
Orientation& Color
Response
y
x
# of Repeats
Orientation
Color
X – stat. sig.> baseline
O – stat. sig.< baseline
4 identical stimuli appear
(200ms)
1 or 2 targets cued by luminance increment
(100ms)
Stimuli move to pause position
(750 ms)
Stimuli Pause(1000 ms)
Stimuli move tofinal position
(750 ms)Cue off(100ms)
Fixation point off: saccadeto ALL targets
RFRF
RFRF
RFRF
RFRFRFRF
RFRFRF
RFRF
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Pe
rce
nt
Co
rre
ct
Performance overRecording Sessions
1 of 4Tracking
2 of 4Tracking
Step 2) Preferred Stimuli Enter and Pause in the Unit’s Receptive Field During Tracking
We recorded 29 cells from Monkey M:
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Time (ms)
Norm
aliz
ed
Response
Mean Response (N=29, All Cells)
Pause Resume
Attended
Unattended
Attended
Unattended
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Time (ms)
Norm
aliz
ed
Response
Pause Resume
Attended
Unattended
Attended
Unattended
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Peak
Norm
aliz
ed
Resp
onse
Modulation = 21.4%
0
10
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50
Peak
Norm
aliz
ed
Resp
onse
Modulation = 29.0%
1of4
Tra
ckin
g2
of4
Tra
ckin
g
AI Index1 of 4 Tracking
AI
Ind
ex
2o
f4
Tra
cki
ng
Relative Attentional Modulation for 1 or 2 Target Tracking
-0.2 -0.1 0 0.1 0.2 0.3-0.2
-0.1
0
0.1
0.2
0.3
AI =Attended - Distracter
Attended + Distracter
Corr. = 0.76
NeuronShown Above
* Stat. Sig.
o Non-Sig.
* Stat. Sig.
o Non-Sig.
There were no significant differencesin the strength of modulation for thetracking of a single or two stimuli.
Pause Period
Stimuli pause(75 ms)
Stimuli pause(75 ms)Form Change
(150 ms)
Example Cell:
Unit C20.1: 1 of 4 Tracking
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140Appear Move Pause Resume End
Tri
alN
um
be
r
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Fir
ing
Ra
te(H
z)
Time (ms)
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Fir
ing
Ra
te(H
z)
Target Distracter0
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g(
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500 1000 1500 2000 2500 3000
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Tri
alN
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be
rF
irin
gR
ate
(Hz)
Time (ms)
Fir
inR
ate
Hz)
Target Distracter
Unit C20.1: 2 of 4 Tracking
Gabor duration 33 msec., One gabor appeared every 8 msec., Resulting in 4 gabors being present at any point in time.
ResponseWindow
Target Distracter
Target Distracter