marisa carrasco psychology and neural science, nyu psychology and neural science, nyu marisa...
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Marisa Carrasco Psychology and Neural Science, NYU
Visual Attention
• Introduction
• definition of the construct
• a bit of history
• Spatial attention and early vision
• contrast
• spatial resolution
• some experimental methods
• Feature based attention
• Visual search
Attention
Visual attention•facilitation and selection of information
•overt attention – head and eye movements
•covert attention – monitor the environment inform eye movements
•spatial attention
•feature based attention
Publications on “Visual attention”
Carrasco (Vision Research, 2011) Visual attention: The
past 25 years
Publications on “Visual attention”
Carrasco (Vision Research, 2011) Visual attention: The
past 25 years
“Everyone knows what attention is. It is the taking possession by the mind, in clear and vivid form, of one out of what seem several simultaneously possible objects or trains of thought. Focalization, concentration, of consciousness are of its essence. It implies withdrawal from some things in order to deal effectively with others…”
The Principles of Psychology William James (1890)
Helmholtz on covert attention (1867)
“It is a curious fact that the observer may be gazing steadily at the two pinholes and holding them in exact coincidence, and yet at the same time he can concentrate his attention on any part of the dark field he likes, so that when the spark comes, he will get an impression about objects in that particular region only.
In this experiment the attention is entirely independent of the position and accommodation of the eyes, or indeed, of any known variations in or on the organ of vision.
Thus it is possible, simply by a conscious and voluntary effort, to focus the attention on some definite spot in an absolutely dark and featureless field.”
Physiological Optics, Vol, 3, p. 455. Thoemmes Press Ed.
Limited resources•The high-energy cost of neuronal activity
involved in cortical computation limits our ability to process information
- constant overall energy consumption available to the brain
- neuronal metabolic cost depends on the spike rate; the cost of a single spike is high
- average discharge rate of active neurons determines how many neurons can be active concurrently […1%! ]
•The brain needs machinery for the system to allocate energy according to task demand… selective attention. Lennie, Current Bio ‘03
Capacity limitation
•As visual information traverses the successive cortical areas of the ventral visual stream, the size of receptive fields increase.
•Neurons in higher order areas with large receptive fields have to deal with many visual stimuli that appear simultaneously within their receptive fields.
Visual attention
+
endogenous exogenous
voluntary involuntary
controlled reflexive
goal-driven stimulus-driven
sustained: 300 ms transient 80–20 ms
Spatial covert attention
Attention – key role in perception
•1980s and early 90s:
• necessary for effortful processing
• ‘glue’ that binds simple features into an object
• what attention does?
• what processes does it affect?
• last decade, effects of attention on perception:
• psychophysics
• single-unit recording
• neuroimaging
Posner’s paradigm
Posner, Nissen, & Ogden (1978)
Posner, Nissen, & Ogden (1978)
Campbell & Robson (68)
Sen
sitiv
ity (
1 / T
hres
hold
)
Spatial Frequency (cpd)
-
+
- +
+
Con
tras
t
Attention enhances sensitivity
neutral
peripheral
1 cpd 2 cpd 4 cpd 8 cpd
Carrasco, Penpeci & Eckstein, Vis.Res. 2000
Experimental trial
Pestilli & Carrasco, 2005
valid/neutral – invalid/neutral
Pestilli & Carrasco, JoV 07
adaptation
Exogenous attention and adaptation
Attention: response gain ~ Ling & Carrasco, Vis. Res.
06
Adaptation: contrast gain
Benefit and cost are similar regardless of adaptation state
Attention overcomes adaptation and restores contrast sensitivity
Pestilli & Carrasco, JoV 07
low high
stimulus contrast
Responses increase with contrast
fMRI acquisition5 participants
3T Siemens, Allegra
Surface coil (Nova medical)
19 slices, perpendicular to calcarine sulcus
Voxel size: 3X3X3 mm
TR = 2 s, TE = 30 ms
Liu, Pestilli & Carrasco, Neuron 2005
V1
V2
V3V3A/B
V7
hV4LO1
LO2
V2
V3
V3A/B
V7
hV4
LO2LO1
Retinotopy and visual areas
dorsalmedial
separate cue/stimulus (ROI)
size: 3°eccentricity: 6° separation: 1° contrast: 100%
Trial sequence
fixation point
invalid valid
precue 50 ms
ISI50 ms
Time display150 ms
response1750 ms
Precue Trialorientation of the tilted Gabor ?
fixation point
invalid valid
precue 50 ms
ISI50 ms
Time display150 ms
response1750 ms
invalid valid
Precue Trial Postcue Trial
Trial sequence
Performance
n = 51 SEM
Accuracy Reaction time (ms)
* *
Valid-precue Invalid-precue Valid-postcue Invalid-postcue
*
* *
BOLD time series
Valid-precue Invalid-precue Valid-postcue Invalid-postcue distracter
Error bars 1 s.e.m
Attention modulation index (AMI)
Peakval-pre – Peakbaseline
Peakval-pre + Peakbaseline
AMI =
•an uninformative peripheral precue concurrently increases performance and retinotopically specific stimulus-evoked activity in early visual areas
•cueing effect increases gradually from V1 to V3a
(feedback or feedforward?)
Liu, Pestilli & Carrasco, Neuron 2005a
fMRI exogenous attention
Reynolds, Pasternak & Desimone, 2000
Single unit recording
YES. Wundt, Mach, Helmholtz & Titchener
W. JamesNO. FechnerYes, but it does not ever lead us astray
Does attention intensify the sensory representation?
- non-predictive peripheral cue - 2 x 2 AFC task: orientation
contingent on apparent contrast
.
.
.
.
.
fixation point 500 ms
cue 67 ms
ISI 53 ms
stimuli 40 ms
response 1 s
neutral cue peripheral cue
Methods
“what is the orientation of the higher contrast
stimulus?”
1 10
SOA - 500 ms
100
n = 16
1 10
0
50
100
n = 16
100
% p
erc
eiv
ed
con
trast
: Te
st >
Sta
nd
ard
Test cuedNeutral cueStandard cued
Contrast appearance
SOA - 100 ms
Contrast of test stimulus
Attention alters contrast appearance
Test Cued Neutral Standard Cued
16% 22% 28%
Carrasco, Ling & ReadNature Neurosci, 2004
Liu, Abrams & Carrasco, Psych.Sci. 2009
Endogenous attention
Liu, Abrams & Carrasco, Psych.Sci. 2009
Attention affects RSVP performance
Liu, Abrams & Carrasco, Psych.Sci. 2009
Attention & appearance•contrast Carrasco, Ling & Read, 2004; Liu, Abrams & Carrasco, 2009,
Anton-Erxleben, Abrams & Carrasco 2011
•spatial frequency Goebell & Carrasco, 2005
• Abrams, Barbot & Cattasco, 2011
•apparent size Anton-Erxleben & Treue, 2007
•motion coherence Liu, Fuller & Carrasco, 2006
•flicker Montagna & Carrasco, 2006
•speed Turatto et al., 2007;
Anton-Erxleben, Herrmann & Carrasco, 2013
•saturation, not hue Fuller & Carrasco, 2006