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Task demands modulate the effects
of perceptual expectations in
early visual cortex
Elexa St. John-Saaltink
Christian Utzerath, Peter Kok
Hakwan Lau, & Floris de Lange
ICON, July 31st, 2014
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Expectations shape what we perceive
…and how our brains process sensory input.
Oliva & Torrabla, 2007Kok et al., 2012
Todorovic et al., 2011
Expectations in perception
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Is expectation suppression automatic?
• Larsson & Smith (2012): No expectation suppression when attention is diverted.
• However, expectation suppression:
• During passive viewing (Alink et al., 2010);
• When task irrelevant (Den Ouden et al., 2009).
Hypothesis: Expectation suppression depends on which processing resources are available.
Expectations in perception
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Divert attention away from predictable stimuli to a task at fixation; compare a perceptual load to a working memory (WM) load.
– If expectation does not require attention, there should still be an expectation effect.
– If expectation is dependent on either perceptual or WM resources, task and expectation will interact.
Rationale
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Perceptual load: 1-back on noisy letters
WM load: 2-back on colours
Design
Predictable Non-predictable
Target Target
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Experimental paradigm
200 ms300 ms
200 ms650-950 ms
~1.5 s
- Cue-predictability blocked (12 trials, 18 s)
- One task per run (5.4 m, 18 blocks)
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Neural effects in early visual cortex
• Expectation suppression during perceptual task (p=0.0079).
• Interaction with task: WM load abolishes expectation effect (p=0.040).
V1
V2 V3
N=33
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• Bilateral cuneus (Right: p<0.001 FWEclust; Left: p=0.013 FWEclust)
Preparatory attentional states (Macalusco et al., 2003);
Associative recognition memory (Yonelinas et al., 2001).
• Right insula (p=0.014 FWEclust)
Expectation violations (Casey et al., 2000);
Response scales with unpredictability (Huettel et al., 2005; Turk-Browne et al., 2010).
Re
gre
sso
r w
eig
ht
Unpredictable
Predictable
Perceptualtask
WMtask
Where else is this interaction present?
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Seed: Bilateral cuneus
Where in the brain is there increased connectivity with these regions as function of predictability, specifically for the task where the expectation cue has an effect?
• Hippocampus (Left SVC: p=0.033; Right SVC: p=0.057)
Sensitive to predictability in the environment (Harrison et al., 2006; Strange et al., 2005; Turk-Browne et al., 2010);
Involved in associative learning and memory (Chua et al., 2007).
Connectivity changes mirroring interaction
Re
gre
sso
r w
eig
ht
Unpredictable
Predictable
Perceptualtask
WMtask
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• Predictable stimuli do not need to be attended in order to be suppressed by expectation.
• However, this effect is task dependent requires WM resources.
– Expectations evoke stimulus-specific representations in primary visual cortex (Kok et al., 2014).
– WM required to bring online stimulus templates?
• Explanation for the discrepancies in the literature:
– Critically, Larsson & Smith (2012) used a WM task.
• Insula & hippocampus are candidate regions for signallingperceptual uncertainty.
• Combined with Yi et al. (2004), further evidence
that expectation suppression (ES) & repetition
suppression (RS) are distinct mechanisms:
Conclusions
RSESPercept.
load
WM load
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Affiliations
Peter Kok
Floris de Lange
Christian Utzerath
Hakwan Lau
Prediction & Attention Lab
Consciousness &Cognition Lab
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• Superior temporal gyrus (STG) (Right: p<0.001
FWEclust; Left: p<0.001 FWEclust)
Predictable stimulus sequences (Berns et al., 2001); and timing (Lewis & Miall, 2003).
Often, but not exclusively, auditory stimuli.
Areas that respond to predictability?
Re
gre
sso
r w
eig
ht
Unpredictable
Predictable
Perceptualtask
WMtask
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Unrepeatedperipheral stimuli
Repeatedperipheral stimuli
Yi et al., Nature Neuroscience 2004
• Tasks at fixation with perceptual or WM load, measured neural activity to the surround (repeats vs. non-repeats).
Time (s)
fMR
Isig
na
l ch
an
ge
(%
)
Perceptualload
WM load
Neural response to peripheral stimulus
Perceptual load: 1-back on noisy facesWM load: 2-back on faces (no noise)
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• Tasks at fixation with perceptual or WM load, measured neural activity to the surround (repeats vs. non-repeats).
Time (s)
fMR
Isig
na
l ch
an
ge
(%
)
Perceptualload
WM load
Neural response to peripheral stimulus
Perceptual load: 1-back on noisy facesWM load: 2-back on faces (no noise)
Perceptual load: 1-back on noisy lettersWM load: 2-back on colours
V1
Yi et al., Nature Neuroscience 2004
Perceptualload
WM load