Allison B Sekuler

McMaster University, Hamilton, Ontario, Canada

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Publications (157)333.89 Total impact

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    ABSTRACT: The standard model of early vision claims that orientation and spatial frequency are encoded with multiple, quasi-independent channels that have fixed spatial frequency and orientation bandwidths. The standard model was developed using detection and discrimination data collected from experiments that used deterministic patterns such as Gabor patches and gratings used as stimuli. However, detection data from experiments using noise as a stimulus suggests that the visual system may use adjustable-bandwidth, rather than fixed-bandwidth, channels. In our previous work, we used classification images as a key piece of evidence against the hypothesis that pattern detection is based on the responses of channels with an adjustable spatial frequency bandwidth. Here we tested the hypothesis that channels with adjustable orientation bandwidths are used to detect two-dimensional, filtered noise targets that varied in orientation bandwidth and were presented in white noise. Consistent with our previous work that examined spatial frequency bandwidth, we found that detection thresholds were consistent with the hypothesis that observers sum information across a broad range of orientations nearly optimally: absolute efficiency for stimulus detection was 20-30% and approximately constant across a wide range of orientation bandwidths. Unlike what we found with spatial frequency bandwidth, the results of our classification image experiment were consistent with the hypothesis that the orientation bandwidth of internal filters were adjustable. Thus, for orientation summation, both detection thresholds and classification images support the adjustable channels hypothesis. Classification images also revealed hallmarks of inhibition or suppression from uninformative spatial frequencies and/or orientations. This work highlights the limitations of the standard model of summation for orientation. The standard model of orientation summation and tuning was chiefly developed with narrow-band stimuli that were not presented in noise, stimuli that are arguably less naturalistic than the variable bandwidth stimuli presented in noise used in our experiments. Finally, the disagreement between the results from our experiments on spatial frequency summation with the data presented in this paper suggests that orientation may be encoded more flexibly than spatial frequency channels.
    Frontiers in Psychology 01/2014; 5:578. · 2.80 Impact Factor
  • Eugenie Roudaia, Allison B Sekuler, Patrick J Bennett
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    ABSTRACT: THE: CURRENT EXPERIMENTS EXAMINED THE EFFECT OF HEALTHY AGING ON THE INTEGRATION OF ORIENTATION AND POSITION INFORMATION IN SHAPE PERCEPTION: FOLLOWING DAY AND LOFFLER 2009, CONFLICTING CONTOURS WERE CREATED BY SAMPLING THE ORIENTATIONS OF ONE SHAPE EG, A ROUNDED PENTAGON WITH GABORS, AND POSITIONING THEM ON THE CIRCUMFERENCE OF A DIFFERENT SHAPE EG, A CIRCLE IN EXPERIMENT 1, SUBJECTS JUDGED WHETHER THE CONFLICTING CONTOUR LOOKED MORE CIRCULAR THAN A ROUNDED PENTAGON OF VARYING AMPLITUDE, WHICH ALLOWED US TO ESTIMATE THE PERCEIVED SHAPE OF THE CONFLICTING CONTOUR THE RELATIVE AMOUNT OF POSITION AND ORIENTATION INFORMATION WAS MANIPULATED BY VARYING THE NUMBER OF GABORS COMPRISING THE TARGET CONTOUR ORIENTATION INFORMATION DOMINATED THE PERCEPT FOR CONTOURS SAMPLED WITH 15-40 ELEMENTS, PRODUCING A STRONG SHAPE ILLUSION, BUT POSITION INFORMATION DETERMINED THE SHAPE WITH DENSER SAMPLING THE MAGNITUDE OF THIS ORIENTATION DOMINANCE EFFECT WAS EQUAL IN YOUNGER AND OLDER SUBJECTS ACROSS ALL SAMPLING LEVELS IN EXPERIMENT 2, SUBJECTS DISCRIMINATED FIVE CONTOURS THAT DIFFERED IN ORIENTATION AND/OR POSITION INFORMATION BOTH GROUPS SHOWED POOR DISCRIMINATION BETWEEN CONFLICTING CONTOURS AND THEIR PERCEPTUALLY EQUIVALENT RADIAL FREQUENCY PATTERNS, CONFIRMING THE MAIN FINDING OF EXPERIMENT 1 IN ADDITION, OLDER SUBJECTS SHOWED WORSE DISCRIMINATION BETWEEN TWO NONCIRCULAR RADIAL FREQUENCY PATTERNS THAN YOUNGER SUBJECTS IN SUM, INTEGRATION OF ORIENTATION AND POSITION INFORMATION IN SHAPE PERCEPTION IS PRESERVED WITH AGING; HOWEVER, OLDER ADULTS ARE LESS ABLE TO MAKE FINE SHAPE DISCRIMINATIONS BETWEEN NONCIRCULAR SAMPLED CONTOURS:
    Journal of vision. 01/2014; 14(5).
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    ABSTRACT: Many sensory and cognitive changes accompany normal ageing, including changes to visual attention. Several studies have investigated age-related changes in the control of attention to specific locations (spatial orienting), but it is unknown whether control over the distribution or breadth of attention (spatial focus) also changes with age. In the present study, we employed a dual-stream attentional blink task and assessed changes to the spatial distribution of attention through the joint consequences of temporal lag and spatial separation on second-target accuracy. Experiment 1 compared the rate at which attention narrows in younger (mean age 22.6, SD 4.25) and older (mean age 66.8, SD 4.36) adults. The results showed that whereas young adults can narrow attention to one stream within 133 ms, older adults were unable to do the same within this time period. Experiment 2 showed that older adults can narrow their attention to one stream when given more time (266 ms). Experiment 3 confirmed that age-related changes in retinal illuminance did not account for delayed attentional narrowing in older adults. Considered together, these experiments demonstrate that older adults can narrow their attentional focus, but that they are delayed in initiating this process compared to younger adults. This finding adds to previously reported reductions in attentional dynamics, deficits in inhibitory processes, and reductions in posterior parietal cortex function that accompany normal ageing.
    Psychological Research 12/2013; · 2.47 Impact Factor
  • Yaroslav Konar, Patrick J Bennett, Allison B Sekuler
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    ABSTRACT: Several studies have shown that face identification accuracy is lower in older than younger adults. This effect of aging might be due to age differences in holistic processing, which is thought to be an important component of human face processing. Currently, however, there is conflicting evidence as to whether holistic face processing is impaired in older adults. The current study therefore re-examined this issue by measuring response accuracy in a 1-of-4 face identification task and the composite face effect (CFE), a common index of holistic processing, in older adults. Consistent with previous reports, we found that face identification accuracy was lower in older adults than in younger adults tested in the same task. We also found a significant CFE in older adults that was similar in magnitude to the CFE measured in younger subjects with the same task. Finally, we found that there was a significant positive correlation between the CFE and face identification accuracy. This last result differs from the results obtained in a previous study that used the same tasks and which found no evidence of an association between the CFE and face identification accuracy in younger adults. Furthermore, the age difference was found with subtraction-, regression-, and ratio-based estimates of the CFE. The current findings are consistent with previous claims that older adults rely more heavily on holistic processing to identify objects in conditions of limited processing resources.
    Vision research 06/2013; · 2.29 Impact Factor
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    ABSTRACT: Background/Study Context: The perception of naturalistic events depends on the ability to integrate perceptual information from multiple sensory systems. Currently, little is known about how multisensory integration is affected by normal aging. Methods: The authors conducted two experiments to investigate audiovisual temporal processing in younger (18-29 years) and older (70+ years) adults. In both experiments, participants were presented with a brief visual stimulus and a brief auditory stimulus separated by various temporal offsets, and participants judged which stimulus was presented first. In Experiment 1, the auditory and visual stimuli were presented from the same perceived location, whereas in Experiment 2 they were presented from different locations. Results: The authors found no effect of stimulus location, and no evidence of age-related declines in performance in either experiment. Conclusion: Older adults appear to retain the ability to discriminate the temporal order of audiovisual stimuli and can perform similarly to younger adults.
    Experimental Aging Research 03/2013; 39(2):179-93. · 1.11 Impact Factor
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    ABSTRACT: In the present study we modified the standard classification image method by subsampling visual stimuli to provide us with a technique capable of examining an individual's face-processing strategy in detail with fewer trials. Experiment 1 confirmed that one testing session (1450 trials) was sufficient to produce classification images that were qualitatively similar to those obtained previously with 10,000 trials (Sekuler, Gaspar, Gold, & Bennett, 2004). Experiment 2 used this method to compare classification images obtained from observers with autism spectrum disorders (ASD) and typically-developing (TD) observers. As was found in Experiment 1, classification images obtained from TD observers suggested that they all discriminated faces based on information conveyed by pixels in the eyes/brow region. In contrast, classification images obtained from ASD observers suggested that they used different perceptual strategies: three out of five ASD observers used a typical strategy of making use of information in the eye/brow region, but two used an atypical strategy that relied on information in the forehead region. The advantage of using the response classification technique is that there is no restriction to specific theoretical perspectives or a priori hypotheses, which enabled us to see unexpected strategies, like ASD's forehead strategy, and thus showed this technique is particularly useful in the examination of special populations.
    Vision research 01/2013; · 2.29 Impact Factor
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    Eugenie Roudaia, Patrick J Bennett, Allison B Sekuler
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    ABSTRACT: The ability to extract contours in cluttered visual scenes, which is a crucial step in visual processing, declines with healthy aging, but the reasons for this decline are not well understood. In three experiments, we examined how the effect of aging on contour discrimination varies as a function of contour and distracter inter-element spacing, collinearity, and stimulus duration. Spiral-shaped contours composed of Gabors were embedded within a field of distracter Gabors of uniform density. In a four alternative forced-choice task, younger and older subjects were required to report the global orientation of the contour. In Experiment 1, the absolute contour element spacing varied from two to eight times the Gabor wavelength and contour element collinearity was disrupted with five levels of orientation jitter. Contour discrimination accuracy was lower in older subjects, but the effect of aging did not vary with contour spacing or orientation jitter. Experiment 2 found that decreasing stimulus durations from 0.8 to 0.04 s had a greater effect on older subjects' performance, but only for less salient contours. Experiment 3 examined the effect of the background on contour discrimination by varying the spacing and orientation of the distracter elements for contours with small and large absolute spacing. As in Experiment, the effect of aging did not vary with absolute contour spacing. Decreasing the distracter spacing, however, had a greater detrimental effect on accuracy in older subjects compared to younger subjects. Finally, both groups showed equally high accuracy when all distracters were iso-oriented. In sum, these findings suggest that aging does not affect the sensitivity of contour integration to proximity or collinearity. However, contour integration in older adults is slower and is especially vulnerable when distracters are denser than contour elements.
    Frontiers in Psychology 01/2013; 4:356. · 2.80 Impact Factor
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    Matthew V Pachai, Allison B Sekuler, Patrick J Bennett
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    ABSTRACT: We measured thresholds in a 1-of-10 face identification task in which stimuli were embedded in orientation-filtered Gaussian noise. For upright faces, the threshold elevation produced by the masking noise varied as a function of noise orientation: significantly greater masking was obtained with horizontal noise than with vertical noise. However, the orientation selectivity of masking was significantly less with inverted faces. The performance of an ideal observer was qualitatively similar to human observers viewing upright faces: the masking function exhibited a peak for horizontally oriented noise although the selectivity of masking was greater than what was observed in human observers. These results imply that significantly more information about facial identity was conveyed by horizontal contours than by vertical contours, and that human observers use this information more efficiently to identify upright faces than inverted faces. We also found a significant positive correlation between selectivity for horizontal information and face identification accuracy for upright, but not inverted faces. Finally, there was a significant positive correlation between horizontal tuning and the size of the face inversion effect. These results demonstrate that the use of information conveyed by horizontal contours is associated with face identification accuracy and the magnitude of the face inversion effect.
    Frontiers in Psychology 01/2013; 4:74. · 2.80 Impact Factor
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    ABSTRACT: Practice in perceptual tasks over hundreds or thousands of trials often leads to long-lasting improvements in performance that generalize only partially to new stimuli. However, the time courses of the general and stimulus-specific aspects of learning are still debated. Some researchers argue that general aspects of the task are learned first in an initial rapid phase of learning and that stimulus-specificity emerges more slowly. In contrast, Hussain et al. (Front Psychol. 2012; 3:226) reported that 105 trials in a 10-AFC face identification task on Day 1 was sufficient to produce stimulus-specific learning in a test phase on Day 2, suggesting that stimulus-specific improvements can emerge rapidly. The current experiments extend these findings by examining 1) whether similar, rapid stimulus-specific learning occurs in a 10-AFC texture identification task; 2) if this rapid stimulus-specificity is long-lasting by increasing the interval between Days 1 and 2 from 24 hours to 1 week; and 3) the effects of reducing practice on Day 1 from 840 to just 21 trials. On Day 1, subjects performed a 10-AFC identification task with band-pass random textures embedded in three levels of external noise. The textures were presented at 7 contrasts that spanned the threshold range; hence the signal-to-noise ratio varied significantly across trials. On Day 2, subjects performed the task with the same or a novel set of textures. The dependent variable was response accuracy, and stimulus-specificity was measured by comparing performance with the same and novel textures on Day 2. We found stimulus-specific learning in subjects who received 840, 105, and 63 trials of practice, but not in subjects who received 21 trials of practice. Our results are consistent with the idea that stimulus-specific learning can emerge rapidly during practice and that this rapid learning is long lasting.Meeting abstract presented at VSS 2013
    Journal of Vision. 01/2013; 13(9):1090.
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    ABSTRACT: The perception of naturalistic events relies on the ability to integrate information from multiple sensory systems, an ability that may change with healthy aging. When two objects move toward and then past one another, their trajectories are perceptually ambiguous: the objects may seem to stream past one another or bounce off one another. Previous research showed that auditory or visual events that occur at the time of disks' coincidence could bias the percept toward bouncing or streaming. We exploited this malleable percept to assay age-related changes in the integration of multiple inter- and intra-modal cues. The disks' relative luminances were manipulated to produce stimuli strongly favoring either bouncing or streaming, or to produce ambiguous motion (equal luminances). A sharp sound coincident with the disks' overlap increased both groups' perception of bouncing, but did so significantly less for older subjects. An occluder's impact on motion perception varied with its duration: a long duration occluder promoted streaming in both groups; a brief occluder promoted bouncing in younger subjects, but not older ones. Control experiments demonstrated that the observed differences between younger and older subjects resulted from neither age-related changes in retinal illuminance nor age-related changes in hearing, pointing to weakened inter- and intra-modal integration with aging. These changes could contribute to previously demonstrated age-related perceptual and memory deficits.
    Frontiers in Psychology 01/2013; 4:267. · 2.80 Impact Factor
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    ABSTRACT: There is substantial evidence that people with Schizophrenia (SCZ) have altered visual perception and cognition, including impaired face processing. However, the mechanism(s) underlying this observation are not yet known. Eye movement studies have found that people with SCZ do not direct their gaze to the most informative regions of the face (e.g., the eyes). This suggests that SCZ patients may be less able to extract the most relevant face information and therefore have decreased calculation efficiency. In addition, research with non-face stimuli indicates that SCZ is associated with increased levels of internal noise. Importantly, both calculation efficiency and internal noise have been shown to underpin face perception among healthy observers. Therefore, the current study applies noise masking to upright and inverted faces to determine if face processing deficits among those with SCZ are the result of changes in calculation efficiency, internal noise, or both. Consistent with previous results, SCZ participants exhibited higher contrast thresholds in order to identify masked target faces. However, higher thresholds were associated with increases in internal noise but unrelated to changes in calculation efficiency. These results suggest that SCZ-related face processing deficits are the result of a decreased noise-to-signal ratio. The source of increased processing noise among these patients is unclear, but may emanate from abnormal neural dynamics.
    Frontiers in Psychology 01/2013; 4:401. · 2.80 Impact Factor
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    ABSTRACT: People with schizophrenia (SCZ) are impaired in several domains of visual processing, including the discrimination and detection of biological motion. However, the mechanisms underlying SCZ-related biological motion processing deficits are unknown. Moreover, whether these impairments are specific to biological motion or represent a more widespread visual motion processing deficit is unclear. In the current study, three experiments were conducted to investigate the contribution of global coherent motion processing to biological motion perception among patients with SCZ. In Experiments 1 and 2, participants with SCZ (n = 33) and healthy controls (n = 33) were asked to discriminate the direction of motion from upright and inverted point-light walkers in the presence and absence of a noise mask. Additionally, participants discriminated the direction of non-biological global coherent motion. In Experiment 3, participants discriminated the direction of motion from upright scrambled walkers (which contained only local motion information) and upright random position walkers (which contained only global form information). Consistent with previous research, results from Experiment 1 and 2 showed that people with SCZ exhibited deficits in the direction discrimination of point-light walkers; however, this impairment was accounted for by decreased performance in the coherent motion control task. Furthermore, results from Experiment 3 demonstrated similar performance in the discrimination of scrambled and random position point-light walkers.
    Frontiers in Psychology 01/2013; 4:507. · 2.80 Impact Factor
  • Eugenie Roudaia, Allison Sekuler, Patrick Bennett
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    ABSTRACT: Contour integration - the ability to group information across space to extract contours - declines with aging (DelViva & Agostini, IOVS, 2007; Roudaia et. al., Vis.Res., 2008, 2011). Here, we examined how age-related changes in contour integration depend on inter-element distance, contour element collinearity, stimulus duration, and distracter density. In a 4AFC task, younger (mean age: 25 y.) and older (mean age: 66 y.) subjects discriminated the global orientation of spiral-shaped contours sampled with Gabor elements (λ= 0.3 deg, σ=0.11 deg, 90% contrast) and embedded in a field of randomly oriented distracter Gabors. In Experiment 1, stimuli were presented for 1s and their minimum inter-element distance was varied across blocks between 2λ and 8λ. Within each block, contour element collinearity was disrupted by the addition of 5 levels of orientation jitter, ranging from 0 - 60 deg. There was a constant age-related decline in accuracy for all inter-element distances and orientation jitter levels.
    Journal of Vision. 08/2012; 12(9):475.
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    ABSTRACT: When two objects move toward one another, motion at the point of overlap is ambiguous: the objects may stream past one another or bounce off one another. A sound presented around the time of coincidence biases the percept toward bouncing (Sekuler et al., 1997, Zhou et al., 2007). In contrast, a visual occluder that obscures the motion coincidence biases the percept toward streaming (Sekuler and Sekuler, 1999). Because multisensory integration changes with age (Peiffer et al., 2007, Stephen et al., 2010), we exploited the bouncing-streaming percept to assay age-related changes in the integration of multiple inter- and intra-modal cues. We also examined the temporal development of occlusion by determining the percept for occluders of different durations. In 12 interleaved conditions, younger (n=9; mean age=20) and older (n=9; mean age=68) subjects judged whether two moving gray discs bounced or streamed. The discs were presented on their own (control), or accompanied by a sound, an occluder of varying du
    Journal of Vision. 08/2012; 12(9):147.
  • Zahra Hussain, Patrick J Bennett, Allison B Sekuler
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    ABSTRACT: Perceptual learning of 10-AFC texture identification is stimulus specific: after practice, identification accuracy drops substantially when textures are rotated 180°, reversed in contrast polarity, or when a novel set of textures is presented. Here we asked if perceptual learning occurs without any repetition of items during training, and whether exposure to greater stimulus variation during training influences transfer of learning. We trained three groups of subjects in a 10-AFC texture identification task on 2 days. The Standard group viewed a fixed set of 10 textures throughout training. The Variable group viewed 840 novel sets of textures. The Switch group viewed different fixed sets of 10 textures on Days 1 and 2. In all groups, transfer of learning was tested by using fixed sets of textures on Days 3 and 4 and having half of the subjects from each group switch to a novel set on Day 4. During training, the most learning was obtained by the Standard group, and gradual but significant learning was obtained by the other two groups. On Day 4, performance of the Standard group was adversely affected by a switch to novel textures, whereas performance of the Variable and Switch groups remained intact. Hence, slight but significant learning occurred without repetition of items during training, and stimulus specificity was influenced significantly by the type of training. Increasing stimulus variability by reducing the number of times stimuli are repeated during practice may cause subjects to adopt strategies that increase generalization of learning to new stimuli. Alternatively, presenting new stimuli on each trial may prevent subjects from adopting strategies that result in stimulus specific learning.
    Vision research 01/2012; 61:89-94. · 2.29 Impact Factor
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    ABSTRACT: Is stimulus specific perceptual learning the result of extended practice or does it emerge early in the time course of learning? We examined this issue by manipulating the amount of practice given on a face identification task on Day 1, and altering the familiarity of stimuli on Day 2. We found that a small number of trials was sufficient to produce stimulus specific perceptual learning of faces: on Day 2, response accuracy decreased by the same amount for novel stimuli regardless of whether observers practiced 105 or 840 trials on Day 1. Current models of learning assume early procedural improvements followed by late stimulus specific gains. Our results show that stimulus specific and procedural improvements are distributed throughout the time course of learning.
    Frontiers in Psychology 01/2012; 3:226. · 2.80 Impact Factor
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    ABSTRACT: Previous research suggests that visual attention can be allocated to locations in space (space-based attention) and to objects (object-based attention). The cueing effects associated with space-based attention tend to be large and are found consistently across experiments. Object-based attention effects, however, are small and found less consistently across experiments. In three experiments we address the possibility that variability in object-based attention effects across studies reflects low incidence of such effects at the level of individual subjects. Experiment 1 measured space-based and object-based cueing effects for horizontal and vertical rectangles in 60 subjects comparing commonly used target detection and discrimination tasks. In Experiment 2 we ran another 120 subjects in a target discrimination task in which rectangle orientation varied between subjects. Using parametric statistical methods, we found object-based effects only for horizontal rectangles. Bootstrapping methods were used to measure effects in individual subjects. Significant space-based cueing effects were found in nearly all subjects in both experiments, across tasks and rectangle orientations. However, only a small number of subjects exhibited significant object-based cueing effects. Experiment 3 measured only object-based attention effects using another common paradigm and again, using bootstrapping, we found only a small number of subjects that exhibited significant object-based cueing effects. Our results show that object-based effects are more prevalent for horizontal rectangles, which is in accordance with the theory that attention may be allocated more easily along the horizontal meridian. The fact that so few individuals exhibit a significant object-based cueing effect presumably is why previous studies of this effect might have yielded inconsistent results. The results from the current study highlight the importance of considering individual subject data in addition to commonly used statistical methods.
    PLoS ONE 01/2012; 7(2):e30693. · 3.53 Impact Factor
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    ABSTRACT: Recent research suggests that faces contain the most information in the horizontal orientation band (Dakin & Watt, J Vis 2009), and the size of the behavioural face inversion effect (bFIE) is correlated with changes in horizontal tuning following inversion (Pachai et al., VSS 2011). Moreover, ERP studies have shown that 1) the N170 is delayed and sometimes increased in amplitude following inversion, 2) the N170 and bFIE are correlated (Jacques and Rossion, NeuroImage 2007), and 3) the N170 inversion effect decreases when horizontal information is scrambled (Jacques et al., VSS 2011). However, the question remains whether the N170 is associated with horizontal tuning, and how that association varies with face inversion. To answer these questions, observers completed a 10AFC identification task using filtered faces. In the full-face condition, faces contained information at all orientations. In the horizontal/vertical conditions, target face information was contained only in orientations within ±35 deg of horizontal/vertical; remaining orientations contained non-informative face information, so stimuli were face-like in all conditions. Initial results from 8 observers, show a bFIE only in the full-face and horizontal conditions. N170 latency, but not amplitude, depended on both orientation filtering and face orientation. Specifically, face inversion increased latency equivalently across filter conditions, whereas latency for upright faces depended on orientation filtering, with the shortest and longest latencies occurring in the full-face and vertical conditions, respectively. When we examined the relationship between the N170 inversion effect for full-faces and the change in behavioural horizontal tuning (horizontal – vertical) following inversion, we found a positive correlation for both latency (r=0.78) and amplitude (r=0.56). To date, our findings reinforce the notion that upright face identification is driven by increased efficiency in processing horizontal face information compared to vertical, and suggest an association between changes in this efficiency following inversion with changes in the N170.Meeting abstract presented at VSS 2012
    Journal of Vision. 01/2012; 12(9):624.
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    ABSTRACT: Previous research suggests that visual attention can be allocated to locations in space (space-based attention) and to objects (object-based attention). The cueing effects associated with space-based attention tend to be large and are found consistently across experiments. Object-based attention effects, however, are small and found less consistently across experiments. In three experiments we address the possibility that variability in object-based attention effects across studies reflects low incidence of such effects at the level of individual subjects. Experiment 1 measured space-based and object-based cueing effects for horizontal and vertical rectangles in 60 subjects comparing commonly used target detection and discrimination tasks. In Experiment 2 we ran another 120 subjects in a target discrimination task in which rectangle orientation varied between subjects. Using parametric statistical methods, we found object-based effects only for horizontal rectangles. Bootstrapping methods were used to measure effects in individual subjects. Significant space-based cueing effects were found in nearly all subjects in both experiments, across tasks and rectangle orientations. However, only a small number of subjects exhibited significant object-based cueing effects. Experiment 3 measured only object-based attention effects using another common paradigm and again, using bootstrapping, we found only a small number of subjects that exhibited significant object-based cueing effects. Our results show that object-based effects are more prevalent for horizontal rectangles, which is in accordance with the theory that attention may be allocated more easily along the horizontal meridian. The fact that so few individuals exhibit a significant object-based cueing effect presumably is why previous studies of this effect might have yielded inconsistent results. The results from the current study highlight the importance of considering individual subject data in addition to commonly used statistical methods.
  • Lisa R Betts, Allison B Sekuler, Patrick J Bennett
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    ABSTRACT: Contrast-dependent interactions between classical (CRF) and non-classical regions (nCRF) of visual neuron receptive fields are well documented in primate visual cortex. Physiological models that describe CRF and nCRF interactions in single neurons have recently been applied to psychophysical measures of spatial summation and suppression in motion perception of young adults (Tadin & Lappin, 2005). We wished to determine whether such models could account for the reduction in spatial suppression that occurs in normal aging (Betts et al., 2005). We applied three models to duration thresholds obtained in a simple motion discrimination task using drifting Gabor stimuli that ranged in spatial frequency from 0.5 to 4c/deg. We found that a model in which the center CRF and surrounding nCRF are represented as spatially-overlapping excitatory and inhibitory 2D Gaussians with independent contrast response functions, which we call the Gain model, could account for the effects of aging simply by increasing the spatial extent of the CRF. Two additional models were evaluated. The Size model, which varied the size of the CRF as a function of contrast, produced CRF and nCRF size constants that departed significantly from physiological estimates of receptive field sizes. The Drive model, which yoked the activation of the suppressive nCRF to the CRF response, yielded reasonable fits to the data and suggested an age-related decline in the strength of suppression from the nCRF. However, the Drive model estimated the CRF size parameter to be equal to, or even slightly larger than, the nCRF size parameter, which is inconsistent with the physiological literature. Our findings therefore suggest that the Gain model provides the most plausible estimates of receptive field sizes. Based on this model, age-related increases in the size of central excitatory receptive fields relative to the inhibitory surrounds may contribute to behavioral measures of reduced spatial suppression found in older observers.
    Vision research 11/2011; 53(1):1-14. · 2.29 Impact Factor

Publication Stats

3k Citations
333.89 Total Impact Points

Institutions

  • 2001–2014
    • McMaster University
      • • Department of Psychology, Neuroscience & Behaviour
      • • Department of Psychology, Neuroscience, and Behavior
      Hamilton, Ontario, Canada
  • 2013
    • Trinity College Dublin
      • Institute of Neuroscience
      Dublin, Leinster, Ireland
    • Queen's University
      Kingston, Ontario, Canada
  • 2008–2013
    • National Institute of Advanced Industrial Science and Technology
      Tsukuba, Ibaraki, Japan
  • 2011–2012
    • University of Nottingham
      • School of Psychology
      Nottingham, ENG, United Kingdom
  • 2008–2010
    • University of Glasgow
      • School of Psychology
      Glasgow, SCT, United Kingdom
  • 2009
    • York University
      • Centre for Vision Research
      Toronto, Ontario, Canada
  • 2007
    • Brandeis University
      • Volen Center for Complex Systems
      Waltham, MA, United States
  • 2005
    • University of Pennsylvania
      • Department of Psychology
      Philadelphia, PA, United States
  • 1993–2003
    • University of Toronto
      • Department of Psychology
      Toronto, Ontario, Canada
  • 2000
    • University of Freiburg
      Freiburg, Baden-Württemberg, Germany
  • 1990
    • University of California, Berkeley
      • Department of Psychology
      Berkeley, MO, United States