How nicotine affects visual attention

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How nicotine affects visual attention
RESEARCH IN COGNITIVE SCIENCE Sept. 14, 2009
Signe A. Vangkilde Cand.psych., Ph.d.-stip.
University of Copenhagen
Center
for Visual Cognition
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Outline
S. VANGKILDE
CENTER FOR VISUAL COGNITION
UNIVERSITY OF
COPENHAGEN

• Introduction and objective
• Experiment Nicotinic manipulation of visual
  attention
• Methods and participants
• Results
• Controlling for confounding factors
• Conclusions Nicotine and attention

3
Outline
S. VANGKILDE
CENTER FOR VISUAL COGNITION
UNIVERSITY OF
COPENHAGEN

• Introduction and objective
• Experiment Nicotinic manipulation of visual
  attention
• Methods and participants
• Results
• Controlling for confounding factors
• Conclusions Nicotine and attention

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Psychopharmacology of attention
S. VANGKILDE
CENTER FOR VISUAL COGNITION
UNIVERSITY OF
COPENHAGEN

• 3 neurotransmitter systems have repeatedly been
  linked to attentional functions
• Acetylcholine (Ach)
• integrity of different memory systems
• maintaining selective attention over time
  (sustained attention)
• effects of selective attention on learning new
  information
• Noradrenaline (NA)
• effects of arousal on selective attention
• distractibility
• working memory functions of the prefrontal
  cortex
• Dopamine (DA)
• executive control

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Acetylcholine and attention
S. VANGKILDE
CENTER FOR VISUAL COGNITION
UNIVERSITY OF
COPENHAGEN

• Cholinergic dysfunction has most often been
  associated with long term memory impairments but
  acetylcholine is probably equally linked to the
  integrity of our attentional functions
• Nicotine is an important cholinergic
  neurotransmitter that has been linked to various
  cognitive functions
• Several studies have observed attentional
  modulations after nicotine, but the exact roles
  played by nicotine and other cholinergic
  substances in attention remain unclear
• Lack of studies manipulating nicotine levels in
  non-smokers
• Lack of a common theoretical framework for
  understanding the findings

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Psychopharmacology of TVA
S. VANGKILDE
CENTER FOR VISUAL COGNITION
UNIVERSITY OF
COPENHAGEN

• General idea
• Use the Theory of visual attention, TVA,
  (Bundesen, 1990) as a general framework for
  understanding the psychopharmacology of visual
  attention
• General method
• Compare drug-induced changes in the value of
  distinct TVA parameters in a double-blind,
  counter-balanced, within-subjects design
• Objective of current experiment
• To clarify at which point in the attentional
  process nicotine exerts its effects by
  identifying the attentional components that are
  affected by nicotine

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Outline
S. VANGKILDE
CENTER FOR VISUAL COGNITION
UNIVERSITY OF
COPENHAGEN

• Introduction and objective
• Experiment Nicotinic manipulation of visual
  attention
• Methods and participants
• Results
• Controlling for confounding factors
• Conclusions Nicotine and attention

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Nicotinic manipulation of visual attention
S. VANGKILDE
CENTER FOR VISUAL COGNITION
UNIVERSITY OF
COPENHAGEN

• Participants
• 20 healthy, non-smoking subjects (17 women),mean
  age 23.4
• 2 experimental sessions (50 minutes, 432 trials)
• Pharmacological manipulation (counter balanced)
• 2 mg nicotine gum or placebo gum, chewed 30 min.
  prior to testing
• Hypothesis
• Nicotinic manipulation will affect parameters
  related to the perceptual threshold and/or speed
  of processing

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Measures
S. VANGKILDE
CENTER FOR VISUAL COGNITION
UNIVERSITY OF
COPENHAGEN

• TVA-based testing
• Accuracy based test of visual attention(Bundesen,
  1990, Psych. Rev.)
• VAS scales monitoring
• Sleepiness
• Dizziness
• Nausea
• Blurred vision
• Dry mouth
• Arousal level

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TVA paradigm
S. VANGKILDE
CENTER FOR VISUAL COGNITION
UNIVERSITY OF
COPENHAGEN
Fixation cross in target colour(1000 ms)
Stimulus display(10-20-50-80-140-200 ms)
Interval(100 ms)
Mask(500 ms)
No interval
Subject reports(Inter-trial interval)
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Demonstrationof TVA paradigm
S. VANGKILDE
CENTER FOR VISUAL COGNITION
UNIVERSITY OF
COPENHAGEN
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S. VANGKILDE
CENTER FOR VISUAL COGNITION
UNIVERSITY OF
COPENHAGEN
TVA paradigm

• Main parameters
• t0 threshold of conscious perception
• C visual processing speed
• K capacity of visual short term memory
• a selectivity
• w_index lateralization of attentional weights

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TVA parameters graphically
S. VANGKILDE
CENTER FOR VISUAL COGNITION
UNIVERSITY OF
COPENHAGEN
17
VAS measures
S. VANGKILDE
CENTER FOR VISUAL COGNITION
UNIVERSITY OF
COPENHAGEN
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VAS measures
S. VANGKILDE
CENTER FOR VISUAL COGNITION
UNIVERSITY OF
COPENHAGEN
Effect Sleepiness Dizziness Nausea Vision Mouth Arousal
Drug (main) ns
Time (main) ns
Drug x Time ns ns ns
In a repeated measures ANOVA with two within-subjects factorsDrug (Nicotine and Placebo) Time (Baseline, Pre-test, Post-test) p lt .05, p lt .01, ns non-significant In a repeated measures ANOVA with two within-subjects factorsDrug (Nicotine and Placebo) Time (Baseline, Pre-test, Post-test) p lt .05, p lt .01, ns non-significant In a repeated measures ANOVA with two within-subjects factorsDrug (Nicotine and Placebo) Time (Baseline, Pre-test, Post-test) p lt .05, p lt .01, ns non-significant In a repeated measures ANOVA with two within-subjects factorsDrug (Nicotine and Placebo) Time (Baseline, Pre-test, Post-test) p lt .05, p lt .01, ns non-significant In a repeated measures ANOVA with two within-subjects factorsDrug (Nicotine and Placebo) Time (Baseline, Pre-test, Post-test) p lt .05, p lt .01, ns non-significant In a repeated measures ANOVA with two within-subjects factorsDrug (Nicotine and Placebo) Time (Baseline, Pre-test, Post-test) p lt .05, p lt .01, ns non-significant In a repeated measures ANOVA with two within-subjects factorsDrug (Nicotine and Placebo) Time (Baseline, Pre-test, Post-test) p lt .05, p lt .01, ns non-significant
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Nicotine and VSTM capacity (K)
S. VANGKILDE
CENTER FOR VISUAL COGNITION
UNIVERSITY OF
COPENHAGEN
Capacity of visual short term memory is
unaffected by nicotine,t(19) 1.78, p gt .05, r
.38
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Nicotine and perceptual threshold (t0)
S. VANGKILDE
CENTER FOR VISUAL COGNITION
UNIVERSITY OF
COPENHAGEN
Nicotine induces a significant decrease in the
perceptual threshold, t(19) 2.31, p .032, r
.47
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Nicotine and perceptual threshold (t0)
S. VANGKILDE
CENTER FOR VISUAL COGNITION
UNIVERSITY OF
COPENHAGEN
Nicotine induces a significant decrease in the
perceptual threshold, t(19) 2.31, p .032, r
.47
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Nicotine and processing speed (C)
S. VANGKILDE
CENTER FOR VISUAL COGNITION
UNIVERSITY OF
COPENHAGEN
After nicotine processing speed is significantly
reduced, t(19) 3.86, p .001, r .66
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Nicotine and processing speed (C)
S. VANGKILDE
CENTER FOR VISUAL COGNITION
UNIVERSITY OF
COPENHAGEN
After nicotine processing speed is significantly
reduced, t(19) 3.86, p .001, r .66
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Nicotine and selectivity (a)
S. VANGKILDE
CENTER FOR VISUAL COGNITION
UNIVERSITY OF
COPENHAGEN
Nicotine significantly impairs selectivity, t(19)
-2.99, p .008, r .57
No selectivity
Perfectselectivity
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Nicotine and selectivity (a)
S. VANGKILDE
CENTER FOR VISUAL COGNITION
UNIVERSITY OF
COPENHAGEN
Nicotine significantly impairs selectivity, t(19)
-2.99, p .008, r .57
Less selective
More selective
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Nicotine and distribution of attention
S. VANGKILDE
CENTER FOR VISUAL COGNITION
UNIVERSITY OF
COPENHAGEN
After nicotine attention is more evenly
distributed, t(19) -2.96, p .008, r .56
Left-sidedbias
Right-sidedbias
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Nicotine and distribution of attention
S. VANGKILDE
CENTER FOR VISUAL COGNITION
UNIVERSITY OF
COPENHAGEN
After nicotine attention is more evenly
distributed, t(19) -2.96, p .008, r .56
Left-sidedbias
Right-sidedbias
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Controlling for confounding factors
S. VANGKILDE
CENTER FOR VISUAL COGNITION
UNIVERSITY OF
COPENHAGEN

• Retest reliability
• Error rate
• Drug order
• Statistical assumptions

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Retest reliability
S. VANGKILDE
CENTER FOR VISUAL COGNITION
UNIVERSITY OF
COPENHAGEN

• 14 healthy young subjects (7 women, 7 men)
• 2 sessions of TVA based testing(same paradigm, ¾
  number of trials)
• Tested at least three weeks apart

  Session 1(mean) Session 2(mean) F(1,13) p
t0 0.012 0.012 0.529 0.48
K 3.32 3.36 4.298 0.06
C 38 40 0.281 0.61
alpha 0.59 0.48 2.717 0.12
w_index 0.45 0.44 0.974 0.34
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Nicotine and error rates
S. VANGKILDE
CENTER FOR VISUAL COGNITION
UNIVERSITY OF
COPENHAGEN
Error rates are slightly and just significantly
increased after nicotine,t(19) -2.20, p .04,
r .45
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Controlling for Error rate
S. VANGKILDE
CENTER FOR VISUAL COGNITION
UNIVERSITY OF
COPENHAGEN

• Are changes in error rate driving the observed
  effects?
• Two groups based on increase in error rate after
  nicotine
• Two-way repeated measures ANOVAs with Drug as
  within subjects factor (levels Nicotine
  Placebo) and Error group as between subjects
  factor (levels High Low Error group) were
  conducted for t0, C, alpha, w_index

  F(1,18) Main effect (Drug) F(1,18) Interaction effect(Drug x Nic session)
t0 5.066 0.037 0.007 0.805
C 14.497 0.001 0.527 0.163
alpha 9.330 0.009 1.839 0.659
w_index 10.010 0.005 3.760 0.068
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Controlling for drug order
S. VANGKILDE
CENTER FOR VISUAL COGNITION
UNIVERSITY OF
COPENHAGEN

• Is the drug order influencing the effects?
• Two-way repeated measures ANOVAs with Drug as the
  within subject factor (levels Nicotine
  Placebo) and Nicotine session as between subjects
  factor (levels Nic. in session 1 Nic. in
  session 2) were con-ducted for the relevant
  parameters t0, C, alpha, w_index, and error rate

  F(1,18) Main effect (Drug) F(1,18) Interaction effect(Drug x Nic session)
t0 6.095 0.024 1.656 0.214
C 14.101 0.001 1.345 0.261
alpha 8.450 0.009 0.012 0.913
w_index 8.403 0.010 0.084 0.775
Error rate 4.358 0.051 1.334 0.263
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Non-parametric control
S. VANGKILDE
CENTER FOR VISUAL COGNITION
UNIVERSITY OF
COPENHAGEN

• Parametric tests were used for all analyses
• With a sample size of 20 it is difficult to
  ascertain that the parametric assumptions are met
• Possible solution ?use non-parametric tests (e.g.
  Wilcoxons Signed Ranks Test)

  PLA_mean NIC_mean T p r
t0 0.012 0.009 35 -0.49
K 3.57 3.44 51.5 ns -0.39
C 56.33 45.03 17 -0.73
alpha 0.4 0.52 38 0.56
w_index 0.47 0.5 38 0.56
Error rate 0.15 0.17 19 0.47
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Outline
S. VANGKILDE
CENTER FOR VISUAL COGNITION
UNIVERSITY OF
COPENHAGEN

• Introduction and objective
• Experiment Nicotinic manipulation of visual
  attention
• Methods and participants
• Results
• Controlling for confounding factors
• Conclusions Nicotine and attention

35
Nicotine and TVA
S. VANGKILDE
CENTER FOR VISUAL COGNITION
UNIVERSITY OF
COPENHAGEN

• Nicotine seems to
• Decrease threshold of conscious perception (?t0
  30)
• Slow down later visual processing (?C 18)
• Decrease selectivity (?a 30)
• Leave VSTM capacity unaffected (?K lt 3)
• Even out distribution of attentional weights
  (?w_Index 7)
• Median values

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?t0 ?C ?a
S. VANGKILDE
CENTER FOR VISUAL COGNITION
UNIVERSITY OF
COPENHAGEN

• Attentional weights have to be calculated and
  allocated before the race towards encoding
  starts
• The duration of t0 probably reflects the
  calculation and allocation of attentional weights
  (among other things)
• Fast, but sloppy weight estimations would lead
  to
• smaller t0, i.e. lower perceptual threshold
• less precise resource allocation ? smaller C,
  i.e. effectively slower processing of information
• less clear difference between of target weights
  and distractor weight ? higher a ? worse
  selectivity

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Summary of findings
S. VANGKILDE
CENTER FOR VISUAL COGNITION
UNIVERSITY OF
COPENHAGEN

• Increased levels of nicotine in the brain result
  in a lower perceptual threshold thus advancing
  the point in time at which encoding of
  information into visual short-term memory is
  begun.
• However, a nicotine surplus also induces trade
  offs by
• slowing down the speed of processing,
• weakening the attentional selectivity thus
  making subjects more prone to spend
  valuable resources on irrelevant information, and
• increasering the probability of making errors
• Finally, nicotine does not seem to affect the
  capacity of visual short term memory.
• Therefore, nicotine is modulating important
  aspects of attention but some attentional
  functions degrade by higher levels of nicotine.

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Thanks!
S. VANGKILDE
CENTER FOR VISUAL COGNITION
UNIVERSITY OF
COPENHAGEN
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A Theory of Visual Attention
S. VANGKILDE
CENTER FOR VISUAL COGNITION
UNIVERSITY OF
COPENHAGEN
RACE(between categorizations)
Visual inputs
Visualshort term memory
Visuallong term memory
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S. VANGKILDE
CENTER FOR VISUAL COGNITION
UNIVERSITY OF
COPENHAGEN
D G C E B
F R J
p
ß
?1, ?2, ?3, ... ?n
w1, w2, w3, ... wn
v1, v2, v3, ... vn
VLTM
Rate
Race
VSTM
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?t0 ?C ?a
S. VANGKILDE
CENTER FOR VISUAL COGNITION
UNIVERSITY OF
COPENHAGEN

• The duration of t0 probably reflects the
  calculation of attentional weights (among other
  things)
• Attentional weights have to be calculated and
  allocated before the race towards encoding
  starts
• Sloppy weight estimations
• smaller t0, i.e. lower perceptual threshold
• less precise resource allocation ? smaller C,
  i.e. effectively slower processing of information
• less clear difference between weights of targets
  and weights of distractors ? higher a ? worse
  selectivity