1 visually-guided motor actions in humans ken nakayama and joo-hyun song harvard university vision...
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Visually-guided Motor Actions in Humans
Ken Nakayama and Joo-Hyun SongHarvard University
VISION SCIENCESLABORATORY
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Actions: Interaction with The External World
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.
• Discrete responses • Continuous interaction
Actions: Read Out Cognitive Processing
• Visually-guided actions: Instantaneously read out internal processes
Yet, the importance of motor actions is overlooked
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Cognitive Theories in Human Behaviors
• Perception Cognitive decision Action
• Issue of motor control
- Limited to post-cognitive decision-making - Mere reflection of completed cognitive decisions
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Target without distractors Target among distractors
Visually-Guided Manual-Pointing Task
+
Single targetEasy Task
+
Odd-color target Difficult Task
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Hand movement recording: 120Hz with Polhemus Fastrak
Visually-Guided Manual-Pointing Task
QuickTime™ and aSorenson Video 3 decompressorare needed to see this picture.
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Outline
• Part 1: Role of focal attention on latencies and trajectories of manual pointing
• Part 2: Concurrent processing of manual pointing to competing stimuli
• Part 3: Automatic adjustment of visuo-motor readiness
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Outline
• Part 1: Role of focal attention on latencies and trajectories of manual pointing
• Part 2: Concurrent processing of manual pointing to competing stimuli
• Part 3: Automatic adjustment of visuo-motor readiness
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Visual Attention: Selection for Perception & Action
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• Broadly distributed attention for entire displays is sufficient to detect and localize the target
Distributed vs. Focused Attention
• Focused attention needs to be allocated to the target for feature discrimination
( Atkinson & Braddick, 1989; Folk & Egeth, 1989; Johnson & Pashler, 1990; Sagi & Julesz, 1985 a, b; Green, 1992)
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Diagnostic Visual Search Paradigm
Mixed Condition
Target: Red Green Red
+ + +
Blocked Condition
Red Red RedTarget:
+ + +
(Bravo & Nakayama, 1992) Number of distractors
React
ion
Tim
es
Detection(distributed)
MixedBlocked
Discrimination (focused)
MixedBlocked
Saccadic tasks: No subtle discrimination required
(McPeek et al., 1999)
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Role of Focused Attention on Latencies & Trajectories of Manual Pointing
Number of distractorsR
eact
ion
Tim
es
Detection (distributed)
MixedBlocked
Discrimination (focused)
MixedBlocked
+ + +
B. Blocked Condition
+ + +
Green GreenGreen
A. Mixed Condition
Green GreenRed
• Full Movement trajectories over the time course: Interaction between cognitive-decision making for the correct target & motor control
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Reaction Time Indexes
(Initiation)Latency
MovementDuration
Total Time
+
Stimulus onset
Finger lift-off
Target touch
Time
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Total Time (ms)
7 Subjects
Exp 1: Effect of Perceptual Grouping of Distractors
680
700
720
740
760
2 5 8 11
Number of distractors
Mixed
Blocked
280
300
320
340
2 5 8 11Number of distractors
MixedBlocked
Initial latency (ms)
380
400
420
440
460
2 5 8 11Number of distractors
MixedBlocked
Movement duration (ms)
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Exp 1: Effect of Perceptual Grouping of Distractors
-5 0 50
2
4
6
8
10
12
-5 0 50
2
4
6
8
10
12
-5 0 50
2
4
6
8
10
12
-5 0 50
2
4
6
8
10
12 # Distractor=0
Vert
ical M
ovem
en
t
Horizontal Movement (Inches)
Mixed condition
Baseline condition
-5 0 50
2
4
6
8
10
12# Distractors=5
0
2
4
6
8
10
12
-5 0 5-5 0 50
2
4
6
8
10
12# Distractors=2 # Distractors=11
C.
Blocked condition
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Exp 1: Effect of Perceptual Grouping of Distractors
-5 0 50
6
12
Horizontal movement (inches)
Ver
tical
mov
emen
t (in
ches
)
• Initially toward distractors & corrected to the target
• Size & frequency of curved trajectories are correlated with the strength of target-distractor competition (McPeek, Han & Keller, 2003).
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Max Curvature=Max(D)/L
-50
5
05
1002468
1012
Forward
Left Right
D
L
.
0.07
0.08
0.09
0.1
0.11
0.12
0 2 4 6 8 10 12
Number of distractors
Baseline
Mixed
Blocked
Exp 1: Effect of Perceptual Grouping of Distractors
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680
700
720
740
760
2 5 8 11
Number of distractors
Mixed
Blocked
Position within Same Color Sequence
. . .1 8. . .
RT
5
Target:
(Maljkovic & Nakayama, 1994; Bichot & Schall, 1999; McPeek et al., 1999)
Exp 2: Effect of Perceptual Priming
Total Time Attended target feature repetition
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Exp 2: Effect of Perceptual Priming
650
675
700
725
750
775
0 1 2 3 4 5 6 7
Order in sequence
Blocked Baseline
7 Subjects
Total time (ms)
Order in sequence400
425
450
475
500
0 1 2 3 4 5 6 7
Blocked Baseline
Movement duration
Order in sequence
240
245
250
255
260
265
270
0 1 2 3 4 5 6 7
Blocked Baseline
Initial latency
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Maximum curvature
Exp 2: Effect of Perceptual Priming
0.05
0.075
0.1
0.125
0.15
0.175
0 1 2 3 4 5 6 7
Order in sequence
Max
imum
cur
vatu
re
Blocked Baseline
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Discussion
• Focused attention is closely associated with manual-pointing process though subtle discrimination is not required. • Trajectory curvature is reduced as decreasing competition between target and distractors by perceptual grouping and cumulative priming
• Interactive processes between target selection and motor control may challenge assumption of serial processing in traditional cognitive theories
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Outline
• Part 1: Role of focal attention on latencies and trajectories of manual pointing
• Part 2: Concurrent processing of manual pointing to competing stimuli
• Part 3: Automatic adjustment of visuo-motor readiness
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Assumption of Serial Processing & Optimal Planning
Perception
Cognitive decision
Action• A single movement is planned & executed serially at a time
• An optimal trajectory is planned• Straight trajectories• Bell-shaped velocity profile
( Flash & Hogan, 1985; Uno, Kawato, & Suzuki, 1989; Engelbrecht, 2001)
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• Reaching trajectories swerves away from distractors ( Tipper, Lortie, & Baylis, 1992; Tipper, Howard, & Houghton, 1998, 2000)
• Dorsal premotor areas encode multiple action plans concurrently, even before cognitive decision is made (Cisek & Kalaska, 2002, 2005)
Multiple Reaching Plans For potential Targets
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
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Are they concurrently planned?
• Do we execute every hand movement after target selection is finalized? • Or, do we sometimes initiate hand movements before completing target selection? • Can movements to competing stimuli be concurrently processed?
When selecting a target among multiple distractors…
+
Odd-color target
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Concurrent Processing of Saccades
Target
InitialsaccadeCorrective
saccade
(McPeek, Skavenski, & Nakayama, 2000)
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Concurrent Processing of Visually-Guided Manual Pointing
vs.
Tiny mass/inertia
High mass/inertia
Hand/arm
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+
Trial 1: Odd-color target
Main Experiment
+
Trial 2: Single target (Baseline)
Trial 3
Trial 4+
+
. .
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Down
Left Right
Up
Single target trials
Movement Trajectories:Single Target
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Down
Left Right
Up
Movement Trajectories:Single Target
Single target trials
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Down
Left Right
Up
Movement Trajectories:Single Target
Single target trials
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Odd-color target trials
Down
Left Right
Up
Movement Trajectories:Odd-Color Target
Single target trials
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Down
Left Right
Up
Movement Trajectories:Odd-Color Target
Odd-color target trialsSingle target trials
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Down
Left Right
Up
Movement Trajectories:Odd-Color Target
Odd-color target trialsSingle target trials
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Down
Left Right
Up
Odd-color target trialsSingle target trials
Movement Trajectories:Odd-Color Target
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Are Initial & Corrective Movements Planned Concurrently ?
• Curved trajectories- Influences of competing distractors on planning & execution of pointing movements
• Are initial & corrective movements concurrently planned, overlapping in time?
• Difficulty of decomposing curved trajectories into discrete two movements
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Estimate of Corrective Movement Onset
Average Baseline Trajectory
Time (ms)
Pos
ition
(inch
es)
0 40 80 120 160 200 240 280 320 360-5
-4
-3
-2
-1
0
1
2
3
4
5
Left
Cen
ter
Rig
ht
-1.5SD
+1.5SD
InitialMovement
CorrectiveMovement
StimulusOnset
+
Initial latency
Corrective latency
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Corrective Latency vs. Initial Latency
8 subjects
243 Trials
0
10
20
30
40
50
60
0 50 100 150 200 250 300 350 400 450 500
Latency(ms)
Number of trials
Corrective latencyInitial latency
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Difference Between Corrective & Initial Latencies
243 Trials
0
5
10
15
20
25
30
35
-400 -300 -200 -100 0 100 200 300 400
Differece betweencorrective and initial latencies (ms)
Number of trials
8 subjects
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Time Cost Of Executing two Concurrently Planned Movements
Vel
ocity
alo
ng t
he c
urve
500 10000
10
20
30
40
Time(ms)
Curved Straight
Straight
Curved
Odd-Color
+
Non-optimal properties
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Time Cost Of Executing two Concurrently Planned Movements
8 subjects
0
100
200
300
400
500
600
700
800
Initial latency Movementduration
Total time
Time (ms)
Curved trajectory
Straight trajectory
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Displaced target
Initial target
~150-250 ms
+
++
Fixation
Time
35% Trials: Displaced
65% Trials: Baseline
Time
+
+
Fixation
Control Experiment:Double-Step Task
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Control Experiment:Double-Step Task
931 Trials
0
50
100
150
200
250
300
0 50 100 150 200 250 300 350 400 450 500
Latency(ms)
Number of trials
Corrective latencyInitial latency
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Discussion
• The cost of planning corrective movements may be negligible because these can be planned in parallel with initial movements.
• Like saccades, pointing movements to competing stimuli can be concurrently processed.
• Hand movements are sometimes initiated before cognitive decision-making for the correct target is completed.
• The visuo-motor system is less concerned with planning a single optimal trajectory as long as the ultimate talk goal is achieved
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Outline
• Part 1: Role of focal attention on latencies and trajectories of manual pointing
• Part 2: Concurrent processing of manual pointing to competing stimuli
• Part 3: Automatic adjustment of visuo-motor readiness
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Down
Left Right
Up
Single Target
• Fast initiation & straight trajectory
Influence of Trial Difficulty on Manual Pointing Strategies
+
Single targetEasy Task
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Single Target
Down
Left Right
Up
• Fast initiation & straight trajectory
Influence of Trial Difficulty on Manual Pointing Strategies
+
Single targetEasy Task
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Single Target
Down
Left Right
Up
• Fast initiation & straight trajectory
Influence of Trial Difficulty on Manual Pointing Strategies
+
Single targetEasy Task
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Odd-Color Target
• Slow initiation & straight trajectory
• Fast initiation but curved trajectory
Influence of Trial Difficulty on Manual Pointing Strategies
+
Odd-color target Difficult Task
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Odd-Color Target
• Slow initiation & straight trajectory
• Fast initiation but curved trajectory
Influence of Trial Difficulty on Manual Pointing Strategies
+
Odd-color target Difficult Task
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Odd-Color Target
• Slow initiation & straight trajectory
• Fast initiation but curved trajectory
Influence of Trial Difficulty on Manual Pointing Strategies
+
Odd-color target Difficult Task
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• How does intermixing trials of varying difficulty influence latency & accuracy criteria of visually-guided manual pointing?
• What mechanism adjusts latency & accuracy criteria in visually-guided manual-pointing tasks?
• How does the time course of latency & accuracy criteria adjust?
Questions
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• Predictability Knowing upcoming trial type may lead to initiation
latency & accuracy adjustment
• Trial Type RepetitionContinuous repetition of the same type trials may lead
to initiation latency & accuracy adjustment
Initiation latency & accuracy criteria for trials of
varying difficulty may be influenced by either …
Predictability vs. Repetition
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Alternating(Odd-color)
Mixed
++
+
+
. .
.
+
. .
.
+
+
+
(Single)
+
+
+
++
+
+
+
. .
. .
. .
Exp1. Dissociation of Predictability & Past Experience
To compare influences of predictability and past trial type repetition on initiation latency & accuracy
adjustment
Blocked
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Exp1. Dissociation of Predictability & Past Experience
Prediction for Adjustment
Blocked Mixed Alternating
Predictability Yes No Yes
Trial Repetition
Yes No No
Cognitive knowledge of the next trial but frequent trial type switch
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Blocked Mixed Alternating
Predictability Yes No Yes
Trial Repetition
Yes No No
200
250
300
350
400
Blocked Mixed Alternated
Single targetOdd color target
N=9
Initiation Latency
√
Adjustment of Initiation Latency Criteria
Alternating
Initi
atio
n la
tenc
y(m
s)Not simply due to task
switchingNo difference in error
rates ( over 98%)
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Blocked Mixed Alternating
Predictability Yes No Yes
Trial Repetition
Yes No No
Movement duration
√
Adjustment of Initiation Latency Criteria
300
350
400
450
500
Blocked Mixed Alternating
Movement duration(ms)
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.
200
250
300
350
400
Blocked Mixed Alternated
Single targetOdd color target
N=9
Adjustment of Initiation Latency Criteria
Alternating
• Homogenization: Initiation latency difference vanished in the mixed & alternating conditions
• No initiation latency differentiation by cognitive knowledge in the alternating condition
• Adjustment of initiation latency criteria by trial type repetitions
+ +++ +Trial sequence
0 0 1 0 1
+
2
Initiation Latency
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60
-50
-25
0
25
50
75
100
1 over 2
Number of the same type trial repetition
0
.
+ +++ +Trial sequence
0 0 1 0 1
+
2
Trial-by-Trial Initiation Latency Adjustment
Moment-to-Moment cumulative learning
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.
200
250
300
350
400
Blocked Mixed Alternated
Single targetOdd color target
N=9
Dissociation of Predictability & Past Experience in Initiation Latency
Alternating
-50
-25
0
25
50
75
100
1 over 2
Number of the same type trial repetition
0
.
No initiation latency differentiation by cognitive knowledge
Cumulative learning from recent experience
Dissociation of the two sources Motor initiation latency is
adjusted by recent experience not by cognitive knowledge
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Adjustment of Accuracy Criteria
Cost of sub-optimal adjustment of latency criteria?
.
200
250
300
350
400
Blocked Mixed Alternated
Single targetOdd color target
N=9
Initiation Latency
Alternating
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Movement Trajectories
Left Right (Inch)
Up
(Inc
h)D
own
Single target
Odd-color target
Blocked Mixed Alternating
-5 0 50
2
4
6
8
10
12
-5 0 50
2
4
6
8
10
12
-5 0 50
2
4
6
8
10
12
-5 0 50
2
4
6
8
10
12
-5 0 50
2
4
6
8
10
12
-5 0 50
2
4
6
8
10
12
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Maximum curvatures.
0.00
0.05
0.10
0.15
0.20
Blocked Mixed Alternated
Single targetOdd color target
N=9
Alternating
More curved trajectory trials in mixed & alternated conditions
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.
200
250
300
350
400
Blocked Mixed Alternated
Single targetOdd color target
N=9
Exp2: Cumulative Learning in Predictable Sequence
Alternating
-50
-25
0
25
50
75
100
1 over 2
Number of the same type trial repetition
0
.
Cumulative learning from recent experience
Questions• Time course with longer sequence?• Predictable sequence?
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Exp2: Cumulative Learning in Predictable Sequence
+ +
++ +
0
+
+
+
++
1 2 3 4 0 1 2 3 4
Odd-color
200
250
300
350
400
0 1 2 3 4
N=9
Number of the same type trial repetition
Singe target
Odd-color target
switching
• 5 single/odd-color target alternation• Alternation informed in advance & Visual cue
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• Intermixing trials of varying difficulty eliminates differences between initiation latencies of easy and difficult trials
Discussion
.
200
250
300
350
400
Blocked Mixed Alternated
Single targetOdd color target
N=9
Alternating
• It is Not task switching : both easy & difficult trials slowed by intermixing
(Allport et al., 1994)
Initiation latency in Exp1
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• Repetition of trials with the same difficulty gradually differentiates initiation latencies by cumulative learning
Discussion
200
250
300
350
400
0 1 2 3 4
N=9
Number of the same type trial repetition
Singe target
Odd-color target
• It is not perceptual priming : both easy and difficult trials facilitated by repetition
(Maljkovic & Nakayama, 1994)
Initiation latency in Exp 2
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• It is not specific to input or output systems: Also, no difference between easy and difficult trials in reading aloud tasks (Lupker et al., 1997)
Discussion
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Fast initiation
• Central mechanism?: Determine sensorimotor readiness by very recent experience: Adjustable gain or threshold setting
Discussion
Time
Threshold
Deci
sion(A
ctiv
ati
on)
Slow initiation
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• Part 1: Role of focal attention on latencies and trajectories of manual pointing
• Part 2: Concurrent processing of manual pointing to competing stimuli
• Part 3: Automatic adjustment of visuo-motor readiness
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• Simple visually-guided action requires the allocation of focused attention to the target • Multiple planning & execution of manual pointing toward competing stimuli can occur
• Visuo-motor action & target selection process are interacting continuously even after motor execution
Conclusion
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• Visuo-motor system is less concerned with planning a single optimal trajectory as long as the ultimate task goal is successfully achieved
• Application: Instantaneous read-out Perceptual/cognitive processing
Conclusion
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Acknowledgements
• Ken Nakayama• Patrick Cavanagh• Yuhong Jiang• Anne Grossetete• Harvard Vision Lab
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Thank you!