Early Stages Of Visual Processing Research Articles

Pupil Constriction in the Glare Illusion Modulates the Steady-State Visual Evoked Potentials

The glare illusion enhances the perceived brightness of a central white area surrounded by a luminance gradient, without any actual change in light intensity. In this study, we measured the varied brightness and neurophysiological responses of electroencephalography (EEG) and pupil size with the several luminance contrast patterns of the glare illusion to address the question of whether the illusory brightness changes to the glare illusion process in the early visual cortex. We hypothesized that if the illusory brightness enhancement was created in the early stages of visual processing, the neural response would be similar to how it processes an actual change in light intensity. To test this, we observed the sustained visual cortical response of steady-state visual evoked potentials (SSVEPs), while participants watched flickering dots displayed in the central white area of both the varied luminance contrast of glare illusion and a control stimulus (no glare condition). We found the SSVEP amplitude was lower in the glare illusion than in the control condition, especially under high luminance contrast conditions. Furthermore, we found the probable mechanisms of the inhibited SSVEP amplitude to the high luminance contrast of glare illusion based on the greater pupil constriction, thereby decreasing the amount of light entering the pupil. Thus, the brightness enhancement in the glare illusion is already represented at the primary stage of visual processing linked to the larger pupil constriction.

S8B-02 SESSION 8B: FACE RESEARCH - PART I TOWARD AN OBJECTIVE OUTCOME IN FACIAL REANIMATION SURGERY: AN EYETRACKING STUDY

Introduction: The availability of an objective outcome measure for facial reconstructive surgery remains elusive. Evaluations submitted by external raters or by patient self-report may be influenced by expert knowledge, emotional antecedent, or implicit attitude. These types of subjective ratings, or objective measures such as anthropometric analysis, may unreliably convey how one is perceived by others. We are interested in observers’ instantaneous, reflexive responses to the human face, and how those instinctive responses relate to subjective judgment of a given face. Methods: We explored the visual markers that lead to differential perception of patients before and after facial reanimation surgery. By examining the early stages of visual processing that occur, we intended to measure changes in the focus of impression formation, thereby helping surgeons and their patients prioritize areas for reconstruction. Pre and post operation (>3 months) photographs from 10 patients with unilateral facial nerve palsy who underwent cross facial nerve graft and free gracillis muscle transfer were obtained.40 observers examined each image while an infrared eye-tracking camera continuously recorded their eye movements. The observers were then asked to rate the image for character attributes (attractiveness, trustworthiness, sociability, healthy, and capability, 1–7 scale). Results: (i) The surgical intervention was found to decrease the observers’ attention to the upper lip on the unaffected (non palsy) side, thus equalizing attention to both sides of the lips. (ii) The surgical intervention was found to significantly increase the character ratings for all five attributes compared to pre op controls: (sociable 3.2 to 3.6, trustworthy 3.42 to 3.61, attractive 2.96 to 3.2, health 3.37 to 3.54, p<0.05. (iii) For those pre-operative images of facial palsy, observers’ attention was overwhelming drawn to the area of disproportion. (iv) Our eye tracking methodology clearly reflects a trend towards normalization of gaze attention following surgical intervention. This finding was associated with the improvement in character assessment of the images in the post-op cohort of images. Conclusion: We provide data illustrating a novel and objective technique to evaluate the effect of reconstructive intervention for facial palsy. This information may be used to inform patients about how these areas of facial difference/aging are perceived, and the potential effect that surgical intervention may have on others’ perception of them. This work may assist patients and their surgeons to more meaningfully focus their surgical decision-making priorities.

Objective Outcomes in Upper Blepharoplasty

GOALS/PURPOSE: The availability of objective outcome measures for facial reconstructive surgery remains lacking. Evaluations submitted by external raters or by patient self-report may be influenced by expert knowledge, emotional antecedent, or implicit attitude. Visual markers that lead to differential perception of patients before and after upper blepharoplasty were explored. By examining the early stages of visual processing that occur when an observer encounters images of affected individuals, we intended to reveal the focus of impression formation, thereby helping surgeons and their patients pinpoint the facial features that are most salient to viewers. METHODS/TECHNIQUE: Eighty images for 13 patients who underwent upper blepharoplasty, with and without lower blepharoplasty and brow lifts, were collected. Photographs were obtained before and after surgical correction (>3 months postoperative). Twenty lookzone regions were mapped onto each facial image, reflecting the esthetic units of the face. Eighty observers examined the images while an infrared eye tracking camera continuously recorded their eye movements. The observers were then asked to rate the image for character attributes (Attractiveness, Trustworthiness, Sociability, Healthy, and Capability, 17 scale). Factorial analysis of variance and Student’s t test analysis were performed to determine significance of differences between groups. Outcomes measured were the total number of eye fixations within different lookzone regions. Eye tracking data of pre- and postoperative images were analyzed and compared. RESULTS/COMPLICATIONS: Thirteen blepharoplasty patients were identified. (1) The surgical intervention was found to increase observers’ attention to the upper eyelid and periorbital area, and to decrease attention to the forehead, lower eyelid, and midcheek areas. (2) The surgical intervention was found to significantly increase the character ratings for all 5 attributes compared to preoperative controls: Sociable 3.66–4.01, Trustworthy 3.91–4.24, Attractive 3.39–3.75, Healthy 4.26–4.66, Capable 4.27–4.56; (P < 0.05) except for Attractive (P = 0.059). (3) For those preoperative images of brow and upper eyelid ptosis that resulted in clinical eyelid asymmetry, observers’ attention was overwhelming drawn to the area of disproportion. (4) Our eye tracking methodology clearly reflects a trend toward normalization of gaze attention following surgical intervention. This finding was associated with the improvement in character assessment of the images in the postoperative cohort of images. CONCLUSION: We provide data illustrating a novel and objective technique to evaluate the effect of reconstructive intervention for the upper eyelid and/or the brow. This information may be used to inform patients about how these areas of facial difference are perceived, and the potential effect that surgical intervention may have on others’ perception of them. This work may assist patients and their surgeons to more meaningfully focus their surgical decision-making priorities.

Rethinking primary visual cortex function

Neuroscience Understanding how color is coded in the brain is central to vision research. The presently dominant model suggests that color and orientation are separately extracted in the primate primary visual cortex. These characteristics are thought to be represented by neurons located in different cortical columns that project separately to higher visual areas for further processing. Working with macaques, Garg et al. recorded from thousands of neurons using two-photon calcium imaging with single-neuron resolution. Nearly half of sampled hue-selective neurons responded more strongly to equiluminant colored stimuli than to full-contrast achromatic stimuli. A majority of strongly color-preferring neurons were also orientation selective. Processing of orientation and color is thus combined at the earliest stages of visual processing, which challenges existing models. Science , this issue p. [1275][1] [1]: /lookup/doi/10.1126/science.aaw5868

Color and orientation are jointly coded and spatially organized in primate primary visual cortex.

Previous studies support the textbook model that shape and color are extracted by distinct neurons in primate primary visual cortex (V1). However, rigorous testing of this model requires sampling a larger stimulus space than previously possible. We used stable GCaMP6f expression and two-photon calcium imaging to probe a very large spatial and chromatic visual stimulus space and map functional microarchitecture of thousands of neurons with single-cell resolution. Notable proportions of V1 neurons strongly preferred equiluminant color over achromatic stimuli and were also orientation selective, indicating that orientation and color in V1 are mutually processed by overlapping circuits. Single neurons could precisely and unambiguously code for both color and orientation. Further analyses revealed systematic spatial relationships between color tuning, orientation selectivity, and cytochrome oxidase histology.

Figure-Ground Modulation in the Human Lateral Geniculate Nucleus Is Distinguishable from Top-Down Attention

Nearly all of the information that reaches the primary visual cortex (V1) of the brain passes from the retina through the lateral geniculate nucleus (LGN) of the thalamus. Although the LGN's role in relaying feedforward signals from the retina to the cortex is well understood [1, 2], the functional role of the extensive feedback it receives from the cortex has remained elusive [3-6]. Here, we investigated whether corticothalamic feedback may contribute to perceptual processing in the LGN in a manner that is distinct from top-down effects of attention [7-10]. We used high-resolution fMRI at 7 Tesla to simultaneously measure responses to orientation-defined figures in the human LGN and V1. We found robust enhancement of perceptual figures throughout the early visual system, which could be distinguished from the effects of covert spatial attention [11-13]. In a secondexperiment, we demonstrated that figure enhancement occurred in the LGN even when the figure and surrounding background were presented dichoptically (i.e., to different eyes). As binocular integration primarily occurs in V1 [14,15], these results implicate a mechanism of automatic, contextually sensitive feedback from binocular visual cortex underlying figure-ground modulation in the LGN. Our findings elucidate the functional mechanisms of this core function of the visual system [16-18], which allows people to segment and detect meaningful figures in complex visual environments. The involvement of the LGN in this rich, contextually informed visual processing-despite showing minimal feedforward selectivity for visual features [19, 20]-underscores the role of recurrent processing at the earliest stages of visual processing.

Dysfunction of Magnocellular/dorsal Processing Stream in Schizophrenia

Background:Patients with schizophrenia show not only cognitive, but also perceptual deficits. Perceptual deficits may affect different sensory modalities. Among these, the impairment of visual information processing is of particular relevance as demonstrated by the high incidence of visual disturbances. In recent years, the study of neurophysiological mechanisms that underlie visuo-perceptual, -spatial and -motor disorders in schizophrenia has increasingly attracted the interest of researchers.Objective:The study aims to review the existent literature on magnocellular/dorsal (occipitoparietal) visual processing stream impairment in schizophrenia. The impairment of relatively early stages of visual information processing was examined using experimental paradigms such as backward masking, contrast sensitivity, contour detection, and perceptual closure. The deficits of late processing stages were detected by examining visuo-spatial and -motor abilities.Results:Neurophysiological and behavioral studies support the existence of deficits in the processing of visual information along the magnocellular/dorsal pathway. These deficits appear to affect both early and late stages of visual information processing.Conclusion:The existence of disturbances in the early processing of visual information along the magnocellular/dorsal pathway is strongly supported by neurophysiological and behavioral observations. Early magnocellular dysfunction may provide a substrate for late dorsal processing impairment as well as higher-level cognition deficits.

Early Brain Sensitivity to Word Frequency and Lexicality During Reading Aloud and Implicit Reading.

The present study investigated the influence of lexical word properties on the early stages of visual word processing (<250 ms) and how the dynamics of lexical access interact with task-driven top-down processes. We compared the brain’s electrical response (event-related potentials, ERPs) of 39 proficient adult readers for the effects of word frequency and word lexicality during an explicit reading task versus a visual immediate-repetition detection task where no linguistic intention is required. In general, we observed that left-lateralized processes linked to perceptual expertise for reading are task independent. Moreover, there was no hint of a word frequency effect in early ERPs, while there was a lexicality effect which was modulated by task demands: during implicit reading, we observed larger N1 negativity in the ERP to real words compared to pseudowords, but in contrast, this modulation by stimulus type was absent for the explicit reading aloud task (where words yielded the same activation as pseudowords). Thus, data indicate that the brain’s response to lexical properties of a word is open to influences from top-down processes according to the representations that are relevant for the task, and this occurs from the earliest stages of visual recognition (within ~200 ms). We conjectured that the loci of these early top-down influences identified for implicit reading are probably restricted to lower levels of processing (such as whole word orthography) rather than the process of lexical access itself.

Higher-level pattern features provide additional information to birds when recognizing and rejecting parasitic eggs.

Despite a recent explosion of research on pattern recognition, in both neuroscience and computer vision, we lack a basic understanding of how most animals perceive and respond to patterns in the wild. Avian brood parasites and their hosts provide an ideal study system for investigating the mechanisms of pattern recognition. The cuckoo finch, Anomalospiza imberbis, and its host the tawny-flanked prinia, Prinia subflava, lay highly polymorphic eggs with a great deal of variation in colour and patterning, with the cuckoo finch capable of close egg mimicry. Behavioural experiments in Zambia have previously shown that prinias use colour and multiple 'low-level' (occurring in early stages of visual processing) pattern attributes, derived from spatial frequency analysis, when rejecting foreign eggs. Here, we explore the extent to which host birds might also use 'higher-level' pattern attributes, derived from a feature detection algorithm, to make rejection decisions. Using a SIFT-based pattern recognition algorithm, NaturePatternMatch, we show that hosts are more likely to reject a foreign egg if its higher-level pattern features-which capture information about the shape and orientation of markings-differ from those of the host eggs. A revised statistical model explains about 37% variance in egg rejection behaviour, and differences in colour, low-level and higher-level pattern features all predict rejection, accounting for 42, 44 and 14% of the explained variance, respectively. Thus, higher-level pattern features provide a small but measurable improvement to the original model and may be especially useful when colour and low-level pattern features provide hosts with little information. Understanding the relative importance of low- and higher-level pattern features is a valuable goal for future work on animal coloration, especially in the contexts of mimicry, camouflage and individual recognition. This article is part of the theme issue 'The coevolutionary biology of brood parasitism: from mechanism to pattern'.

Coding of low-level position and orientation information in human naturalistic vision.

Orientation and position of small image segments are considered to be two fundamental low-level attributes in early visual processing, yet their encoding in complex natural stimuli is underexplored. By measuring the just-noticeable differences in noise perturbation, we investigated how orientation and position information of a large number of local elements (Gabors) were encoded separately or jointly. Importantly, the Gabors composed various classes of naturalistic stimuli that were equated by all low-level attributes and differed only in their higher-order configural complexity and familiarity. Although unable to consciously tell apart the type of perturbation, observers detected orientation and position noise significantly differently. Furthermore, when the Gabors were perturbed by both types of noise simultaneously, performance adhered to a reliability-based optimal probabilistic combination of individual attribute noises. Our results suggest that orientation and position are independently coded and probabilistically combined for naturalistic stimuli at the earliest stage of visual processing.

Attentional modulation of neural responses to illusory shapes: Evidence from steady-state and evoked visual potentials

Our perception of illusory shapes, such as the classic Kanizsa triangle, is thought to reflect the visual system’s capacity to fill in missing information associated with fragmented or partially occluded objects. Previous work has suggested that such ‘modal’ filling-in arises at relatively early stages of visual processing, prior to the allocation of focused attention, but few studies have examined whether attention influences neural responses to illusory shapes. Here we asked whether spatial attention affects neural activity evoked by illusory shapes by having participants focus on stimuli presented in one visual field (left or right), while ignoring those on the other side. In two separate experiments, we used electroencephalography (EEG) to measure steady-state visual evoked potentials (SSVEPs; Experiment 1) and event-related potentials (ERPs; Experiment 2), elicited by a Kanizsa square in one hemifield and a competing control stimulus, matched for all relevant physical features, in the other. In Experiment 1, the inducers used to construct the Kanizsa and control stimuli flickered at unique frequencies (10 and 13.33 Hz) to elicit SSVEPs. In Experiment 2, segments were removed briefly from static circular placeholders within the left and right visual hemifields to induce ERPs. In both experiments, participants were instructed to attend covertly to the stimulus on the left or right side to detect brief contrast changes of the inducers. SSVEP analyses revealed that illusory shapes that were ignored yielded a significantly larger neural response than those elicited by non-illusory control stimuli. By contrast, when the stimuli were attended, neural responses to the illusory and control stimuli were statistically indistinguishable. Consistent with these steady-state findings, results of the ERP analyses revealed that evoked responses to illusory shapes emerged earlier relative to control stimuli when they were ignored than when they were attended. Taken together the findings suggest that neural activity associated with modal completion is reliably modulated by spatial attention. Specifically, we show that neural responses to actively ignored illusory shapes are elicited earlier and are sustained at a higher amplitude than responses to control stimuli. This advantage for ignored shapes might reflect adaptive signalling of the presence of an object available for future goal-directed behaviour.

Characterization of Retinal Functionality at Different Eccentricities in a Diurnal Rodent.

Although the properties of the neurons of the visual system that process central and peripheral regions of the visual field have been widely researched in the visual cortex and the LGN, they have scarcely been documented for the retina. The retina is the first step in integrating optical signals, and despite considerable efforts to functionally characterize the different types of retinal ganglion cells (RGCs), a clear account of the particular functionality of cells with central vs. peripheral fields is still wanting. Here, we use electrophysiological recordings, gathered from retinas of the diurnal rodent Octodon degus, to show that RGCs with peripheral receptive fields (RF) are larger, faster, and have shorter transient responses. This translates into higher sensitivity at high temporal frequencies and a full frequency bandwidth when compared to RGCs with more central RF. We also observed that imbalances between ON and OFF cell populations are preserved with eccentricity. Finally, the high diversity of functional types of RGCs highlights the complexity of the computational strategies implemented in the early stages of visual processing, which could inspire the development of bio-inspired artificial systems.

The Effects of Low and High Levels of Sadness on Scope of Attention: An ERP Study.

Sadness has inconsistent effects on the scope of attention. These differing effects may be attributed to different levels of sadness induced in different experiments. Low levels of sadness can expand the scope of attention, but high levels can narrow it. In this study, we recruited 42 college students and induced different levels of sadness in them by having them view sad images continuously, and then we assigned them Navon’s letter task. The results showed that among participants with local-processing bias, those at lower levels of sadness were slower to identify small letters than were those at high levels of sadness and control condition (watching neutral images). Event-related potential (ERP) results showed that low-sadness participants put more attention resources toward processing large letters (global stimuli). They showed increased amplitude of the P1 component compared with high-sadness participants and participants at control condition. These results suggested that different levels of sadness had different effects on attention scope: low levels of sadness extended the scope but as sadness increased, this extension disappeared. This influence pattern mainly occurred in the early stages of visual processing.

Processing of visual negation

<p id="C2">Previous research focused on the processing of verbal negation, while there was very little research in the area of visual negation. In this study, the lexical decision paradigm was used to explore the mental simulation of visual negation processing in early, middle, and late processing stages to reveal the mechanism of visual negation. To achieve this goal, we performed three experiments. In each experiment on each trial subjects first viewed a picture, and then after a interstimulus interval (ISI) that varied by experiment, viewed a word and had to decide if the word was consistent with the picture or not. <p id="C80">Experiment 1 explored the mental simulation of visual negation in early stage of processing using a short 250ms ISI. Participants reacted more quickly to the negative probes which represented the actual final states, as compared with the affirmative probes which represented the negated states. This implies that, in the early stage of the visual negation processing, the final state has already been simulated in the participants’ representation. Although the results did not confirm the two-step-simulation hypothesis, it supported the suppression / retention hypothesis. <p id="C81">Experiment 2 examined the mental simulation of visual negation in middle stage of processing using a 750ms ISI. The pattern of results was very similar to Experiment 1: participants reacted more quickly to the negative probes that represented the actual final states, as compared with the affirmative probes that represented the negated states. These results imply that the final state was simulated in the participants’ representation during the middle stage of processing. <p id="C82">Experiment 3 explored the late stage of processing using a 1500ms ISI. The results pattern replicated those of Experiment 1 and Experiment 2, that is, the reaction time to negative probes was significantly faster than to affirmative probes. The results demonstrated that in the late stage of the visual negation processing, participants simulated the actual final state of the visual negative pictures but not the negated state of the visual negative pictures. Again, it disconfirmed the two-step simulation hypothesis, but supported the suppression / retention hypothesis. <p id="C83">In sum, taken together the findings from the three experiments, we can draw the following conclusions. The actual state was simulated during the processing of visual negation similarly across the early, middle, and late visual processing stages. These results support the theory that simulation occurs in a single step (the one-step simulation view) rather than the two-step simulation view. Second, the suppression / retention hypothesis for the negated information processing in visual negation has been strongly supported.

Automatic Detection of Orientation Contrast Occurs at Early but Not Earliest Stages of Visual Cortical Processing in Humans.

Orientation contrast is formed when some elements orient differently from their surroundings. Although orientation contrast can be processed in the absence of top-down attention, the underlying neural mechanism for this automatic processing in humans is controversial. In particular, whether automatic detection of orientation contrast occurs at the initial feedforward stage in the primary visual cortex (i.e., V1) remains unclear. Here, we used event-related potentials (ERPs) to examine the automatic processing of orientation contrast in humans. In three experiments, participants completed a task at fixation while orientation contrasts were presented in the periphery, either in the upper visual field (UVF) or the lower visual field (LVF). All experiments showed significant positive potentials evoked by orientation contrasts over occipital areas within 100 ms after stimulus onset. These contrast effects occurred 10–20 ms later than the C1 components evoked by identically located abrupt onset stimuli which indexes the initial feedforward activity in V1. Compared with those in the UVF, orientation contrasts in the LVF evoked earlier and stronger activities, probably reflecting a LVF advantage in processing of orientation contrast. Even when orientation contrasts were rendered almost invisible by backward masking (in Experiment 2), the early contrast effect in the LVF was not disrupted. These findings imply that automatic processing of orientation contrast could occur at early visual cortical processing stages, but was slightly later than the initial feedforward processing in human V1; such automatic processing may involve either recurrent processing in V1 or feedforward processing in early extrastriate visual cortex.Highlights -We examined the earliest automatic processing of orientation contrast in humans with ERPs.-Significant orientation contrast effect started within 100 ms in early visual areas.-The earliest orientation contrast effect occurred later than the C1 evoked by abrupt onset stimuli.-The earliest orientation contrast effect was independent of top-down attention and awareness.-Automatic detection of orientation contrast arises slightly after the initial feedforward processing in V1.

Contextual working memory for trans-saccadic object recognition using reinforcement learning and informative local descriptors

Previous research on behavioural modelling of saccade-driven image interpretation (Henderson, 1982 Psychological Science 8 51 ^ 55) has emphasised the sampling of informative parts under visual attention to guide visual perception. We propose two major innovations to trans-saccadic object recognition: first, we model contextual tuning at the early visual processing stage. Salience in pre-processing is determined from descriptors in terms of local gradient histogram patterns - SIFT features (Lowe, 2004 International Journal of Computer Vision 60 91 ^ 110). SIFT features are scale-, rotation-, and to a high degree illumination-tolerant, in a substantial extension to previously used edge features (Rybak et al, 1998 Vision Research 38 2387 ^ 2400) or appearance patterns (Paletta et al, 2004 Perception 33 Supplement, 126). Descriptors that are informative with respect to an information theoretic framework (Fritz et al, 2004, in Proceedings of the International Conference on Pattern Recognition volume 2, pp 15 ^ 18) are selected and weighted according to contextual salience. Second, we develop a behavioural strategy for saccade-driven information access, operating on contextually selected features and attention shifts, being performed in terms of a partially observable Markovian decision process and represented by a short-term working memory generating discriminative perception ^ action sequences. It is developed under exploration and reinforcement feedback using Q-learning, a machine-learning methodology representing operant conditioning. Saccadic targets are selected for attention only in a local neighbourhood of a currently focused descriptor. The learned strategy proposes next actions that support expected maximisation of reward, eg minimisation of entropy in posterior object discrimination. We demonstrate the performance of using the sensory ^motor context of trans-saccadic outdoor object recognition, efficiently identifying building facades from different viewpoints, distances, and varying illumination conditions.

Features of the influence of a large-angular-size screen on the optimization of task-oriented activities of an observer in an interactive virtual environment

In this paper, the results of experiments are presented in which the impact of interactive virtual environments combined with the performance of a cognitive task was estimated on the visual system of a healthy observer. Monitors of two angular sizes were used to present the images. To estimate the impacts of the environments, measurements of visual evoked potentials were taken during the perception of two types of images containing low-frequency and high-frequency parts of the spatial frequency spectrum. Measurements were performed both before and after interaction with the virtual environment. It is established that using a screen of a small angular size enhances the analysis of high-frequency images at the early stages of visual information processing. When using a large angular size screen, the processing of both types of image improves at both the early and late stages of analysis. It is assumed that the changes in the evoked potentials are related to the difference in the stimulation of the central and peripheral fields of vision when the angular size of the screen varies.

Prior object-knowledge sharpens properties of early visual feature-detectors

Early stages of visual processing are carried out by neural circuits activated by simple and specific features, such as the orientation of an edge. A fundamental question in human vision is how the brain organises such intrinsically local information into meaningful properties of objects. Classic models of visual processing emphasise a one-directional flow of information from early feature-detectors to higher-level information-processing. By contrast to this view, and in line with predictive-coding models of perception, here, we provide evidence from human vision that high-level object representations dynamically interact with the earliest stages of cortical visual processing. In two experiments, we used ambiguous stimuli that, depending on the observer’s prior object-knowledge, can be perceived as either coherent objects or as a collection of meaningless patches. By manipulating object knowledge we were able to determine its impact on processing of low-level features while keeping sensory stimulation identical. Both studies demonstrate that perception of local features is facilitated in a manner consistent with an observer’s high-level object representation (i.e., with no effect on object-inconsistent features). Our results cannot be ascribed to attentional influences. Rather, they suggest that high-level object representations interact with and sharpen early feature-detectors, optimising their performance for the current perceptual context.

Top-down matching singleton cues have no edge over top-down matching nonsingletons in spatial cueing

In the present study, we investigated in a novel version of the peripheral-cueing paradigm whether object salience influences attentional selection at early stages of visual processing. In each trial, participants searched for targets of one of two possible colors. In the most important condition, the cueing displays consisted of a singleton cue having one target color and three additional nonsingletons of another target color. Hence, all objects in these all-relevant cueing displays had a target color. If singletons initially capture attention in a stimulus-driven way, regular cueing effects (faster responses to targets at the cued location than to targets away from the cue) should be found in these conditions. However, the results suggested otherwise: As compared to a control condition with a singleton cue of a target color among nonsingletons of a nontarget color, the cueing effects in all-relevant cueing displays were strongly reduced. This was also replicated with a very brief cue–target interval. The results suggest top-down contingent capture of attention even during the initial phase of processing salient stimuli, and argue against stimulus-driven capture of attention plus subsequent rapid disengagement.

Cognitive penetration of early vision in face perception.

Cognitive and affective penetration of perception refers to the influence that higher mental states such as beliefs and emotions have on perceptual systems. Psychological and neuroscientific studies appear to show that these states modulate the visual system at the visuomotor, attentional, and late levels of processing. However, empirical evidence showing that similar consequences occur in early stages of visual processing seems to be scarce. In this paper, I argue that psychological evidence does not seem to be either sufficient or necessary to argue in favour of or against the cognitive penetration of perception in either late or early vision. In order to do that we need to have recourse to brain imaging techniques. Thus, I introduce a neuroscientific study and argue that it seems to provide well-grounded evidence for the cognitive penetration of early vision in face perception. I also examine and reject alternative explanations to my conclusion.