Introduction definition of the construct a bit of history Spatial attention and early vision contrast spatial resoluti

1. 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

2. Introduction a bit of history some experimental methods definition of the construct spatial vs. feature-based vs. object-based spatial: overt vs. covert attention covert: endogenous (sustained) vs. exogenous (transient) Spatial attention and early vision contrast sensitivity endogenous : contrast gain exogenous: response gain endogenous attention potentiates effects of adaptation Contrast sensitivity Exogenous: cost at unattended location Exogenous overcomes adaptation and restores sensitivity Attention signatures: Attention-plus-external noise paradigm

3. There is consensus that performance improves at the attended location, in general, and that contrast sensitivity is increased, in particular. BUT, what happens at the unattended location? Transient or exogenous attention: observers are explicitly told that the cue is non-informative; There is consensus that performance improves at the attended location, in general, and that contrast sensitivity is increased, in particular. BUT, what happens at the unattended location? Transient or exogenous attention: observers are explicitly told that the cue is non-informative;

4. Left panel: ratio of sensitivity valid/neutral yields benefit; ratio of sensitivity invalid/neutral yields cost. Right panel: histogram plots the frequency distribution of contrast thresholds. For both eccentricities the median contrast threshold is lower for valid than neutral condition, which in turn is lower than for invalid condition. All 5 observers showed same pattern of resultsLeft panel: ratio of sensitivity valid/neutral yields benefit; ratio of sensitivity invalid/neutral yields cost. Right panel: histogram plots the frequency distribution of contrast thresholds. For both eccentricities the median contrast threshold is lower for valid than neutral condition, which in turn is lower than for invalid condition. All 5 observers showed same pattern of results

5. Adaptation also affects contrast gain.Adaptation also affects contrast gain.

8. Effect of attention on asymptote and threshold. Effect of adaptation on threshold only.Effect of attention on asymptote and threshold. Effect of adaptation on threshold only.

9. Transient 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 This suggests that attention affects the normalized signal once the effect of contrast adaptation has taken place, and that these two ?mechanisms act separately to change contrast sensitivity.This suggests that attention affects the normalized signal once the effect of contrast adaptation has taken place, and that these two ?mechanisms act separately to change contrast sensitivity.

10. YES. Wundt, Mach, Helmholtz & Titchener W. James long-standing debate about how and when attention affect perceptionlong-standing debate about how and when attention affect perception

11. Methods Does attention alter appearance? Strong debate: james vs. fechner� Surprisingly, not addressed experimentally until recently�Does attention alter appearance? Strong debate: james vs. fechner� Surprisingly, not addressed experimentally until recently�

12. Stimuli

16. Attention & appearance spatial frequency Goebell & Carrasco, 2005 apparent size Anton-Erxleben & Treue, 2007 motion coherence Liu, Fuller & Carrasco, 2006 flicker Montagna & Carrasco, 2006 speed Turatto et al., 2007 saturation, not hue Fuller & Carrasco, 2006

17. Covert attention enhanced contrast sensitivity at attended location; diminished sensitivity at unattended location transient: performance � response gain appearance restores effects of adaptation (contrast gain) sustained: performance � contrast gain strengthens adaptation

23. 

24. Perceptual template w/ certain tuning characteristics (e.g., a spatial frequency filter) Nonlinear transducer function Nm - A multiplicative internal noise - Gaussian distributed with mean 0 and standard deviation % to the total energy in the input stimulus. Na - Independent additive internal noise - Gaussian distributed with mean 0 and a fixed standard deviation A decision process that operates on the noisy internal representation of the stimulus - detection, discrimination, AFC, yes - no taskPerceptual template w/ certain tuning characteristics (e.g., a spatial frequency filter) Nonlinear transducer function Nm - A multiplicative internal noise - Gaussian distributed with mean 0 and standard deviation % to the total energy in the input stimulus. Na - Independent additive internal noise - Gaussian distributed with mean 0 and a fixed standard deviation A decision process that operates on the noisy internal representation of the stimulus - detection, discrimination, AFC, yes - no task

25. mathematically equivalent to internal additive noise reduction. Attention turns up the gain. Stimulus enhancement affects both the signal and the external noise in the input stimulus in the same way. No retuning of the perceptual template. focusing perceptual analysis on the appropriate spatial region or content characteristics of the stimulus. Performance improvements in the region of high external noise, where there is external noise to exclude. This implies retuning of the perceptual template - retuning sets of perceptual channels or changing the channels entering into the decision multiplicative noise increases with increasing contrast in the stimulus display. Improvements in both high and low levels of external noise, with slightly larger effects in high external noise - no such effect has been observed How to distinguish mechanism mixtures? By measuring TVC functions at multiple performance levels. IF stimulus enhancement or External noise exclusion, the magnitude of the attention effect is the same (on the log contrast axis) at different performance levels. That is not the case for multiplicative noise reduction. mathematically equivalent to internal additive noise reduction. Attention turns up the gain. Stimulus enhancement affects both the signal and the external noise in the input stimulus in the same way. No retuning of the perceptual template. focusing perceptual analysis on the appropriate spatial region or content characteristics of the stimulus. Performance improvements in the region of high external noise, where there is external noise to exclude. This implies retuning of the perceptual template - retuning sets of perceptual channels or changing the channels entering into the decision multiplicative noise increases with increasing contrast in the stimulus display. Improvements in both high and low levels of external noise, with slightly larger effects in high external noise - no such effect has been observed How to distinguish mechanism mixtures? By measuring TVC functions at multiple performance levels. IF stimulus enhancement or External noise exclusion, the magnitude of the attention effect is the same (on the log contrast axis) at different performance levels. That is not the case for multiplicative noise reduction.

26. Attention-plus-external noise paradigm Response cue eliminates decisional structural uncertainty - observers are explicitly informed of the target location in all experimental conditionsResponse cue eliminates decisional structural uncertainty - observers are explicitly informed of the target location in all experimental conditions

28. Signal enhancement suprathreshold target stimulus no distracters no local or global masks no location uncertainty response cue

29. PTM