Putting spatial attention on the map: timing and localization of stimulus selection processes in striate and extrastriate visual areas

Temporal Unfolding of Racial Ingroup Bias in Neural Responses to Perceived Dynamic Pain in Others

In this study, we investigated how empathic neural responses unfold over time in different empathy networks when viewing same-race and other-race individuals in dynamic painful conditions. We recorded magnetoencephalography signals from Chinese adults when viewing video clips showing a dynamic painful (or non-painful) stimulation to Asian and White models' faces to trigger painful (or neutral) expressions. We found that perceived dynamic pain in Asian models modulated neural activities in the visual cortex at 100 ms-200 ms, in the orbitofrontal and subgenual anterior cingulate cortices at 150 ms-200 ms, in the anterior cingulate cortex around 250 ms-350 ms, and in the temporoparietal junction and middle temporal gyrus around 600 ms after video onset. Perceived dynamic pain in White models modulated activities in the visual, anterior cingulate, and primary sensory cortices after 500 ms. Our findings unraveled earlier dynamic activities in multiple neural circuits in response to same-race (vs other-race) individuals in dynamic painful situations.

Transcranial magnetic stimulation on the right dorsal attention network modulates the center-surround profile of the attentional focus

Psychophysical observations indicate that the spatial profile of visuospatial attention includes a central enhancement around the attentional focus, encircled by a narrow zone of reduced excitability in the immediate surround. This inhibitory ring optimally amplifies relevant target information, likely stemming from top-down frontoparietal recurrent activity modulating early visual cortex activations. However, the mechanisms through which neural suppression gives rise to the surrounding attenuation and any potential hemispheric specialization remain unclear. We used transcranial magnetic stimulation to evaluate the role of two regions of the dorsal attention network in the center-surround profile: the frontal eye field and the intraparietal sulcus. Participants performed a psychophysical task that mapped the entire spatial attentional profile, while transcranial magnetic stimulation was delivered either to intraparietal sulcus or frontal eye field on the right (Experiment 1) and left (Experiment 2) hemisphere. Results showed that stimulation of right frontal eye field and right intraparietal sulcus significantly changed the center-surround profile, by widening the inhibitory ring around the attentional focus. The stimulation on the left frontal eye field, but not left intraparietal sulcus, induced a general decrease in performance but did not alter the center-surround profile. Results point to a pivotal role of the right dorsal attention network in orchestrating inhibitory spatial mechanisms required to limit interference by surrounding distractors.

Turning the Light Switch on Binding: Prefrontal Activity for Binding and Retrieval in Action Control

According to action control theories, responding to a stimulus leads to the binding of response and stimulus features into a common representation, that is, an event file. Repeating any component of an event file retrieves all previously bound information, leading to performance costs for partial repetitions measured in so-called binding effects. Although otherwise robust and stable, binding effects are typically completely absent in "localization tasks," in which participants localize targets with spatially compatible responses. Yet, it is possible to observe binding effects in such when location features have to be translated into response features. We hypothesized that this modulation of binding effects is reflected in task involvement of the dorsolateral pFC (DLPFC). Participants localized targets with either direct (i.e., spatially compatible key) or translated (i.e., diagonally opposite to the spatially compatible key) responses. We measured DLPFC activity with functional near-infrared spectroscopy. On the behavioral level, we observed binding effects in the translated response condition, but not in the direct response condition. Importantly, prefrontal activity was also higher in the translated mapping condition. In addition, we found some evidence for the strength of the difference in binding effects in behavioral data being correlated with the corresponding effects in prefrontal activity. This suggests that activity in the DLPFC reflects the amount of executive control needed for translating location features into responses. More generally, binding effects seem to emerge only when the task at hand involves DLPFC recruitment.

Crossmodal visual predictions elicit spatially specific early visual cortex activity but later than real visual stimuli

Previous studies have indicated that crossmodal visual predictions are instrumental in controlling early visual cortex activity. The exact time course and spatial precision of such crossmodal top-down influences on the visual cortex have been unknown. In the present study, participants were exposed to audiovisual combinations comprising one of two sounds and a Gabor patch either in the top left or in the bottom right visual field. Event-related potentials (ERPs) were recorded to these frequent crossmodal combinations (standards) as well as to trials in which the visual stimulus was omitted (omissions) or the visual and auditory stimuli were recombined (deviants). Standards and deviants elicited an ERP between 50 and 100 ms of opposite polarity known as the C1 effect commonly associated with retinotopic processing in early visual cortex. By contrast, a C1 effect was not observed in omission trials. Spatially specific omission and mismatch effects (deviants minus standards) started only later with a latency of 230 ms and 170 ms, respectively. These results suggest that crossmodal visual predictions control visual cortex activity in a spatially specific manner. However, visual predictions do not modulate visual cortex activity with the same timing as visual stimulation activates these areas but rather seem to involve distinct neural mechanisms. This article is part of the theme issue 'Decision and control processes in multisensory perception'.

Independent spatiotemporal effects of spatial attention and background clutter on human object location representations

Spatial attention helps us to efficiently localize objects in cluttered environments. However, the processing stage at which spatial attention modulates object location representations remains unclear. Here we investigated this question identifying processing stages in time and space in an EEG and fMRI experiment respectively. As both object location representations and attentional effects have been shown to depend on the background on which objects appear, we included object background as an experimental factor. During the experiments, human participants viewed images of objects appearing in different locations on blank or cluttered backgrounds while either performing a task on fixation or on the periphery to direct their covert spatial attention away or towards the objects. We used multivariate classification to assess object location information. Consistent across the EEG and fMRI experiment, we show that spatial attention modulated location representations during late processing stages (>150 ms, in middle and high ventral visual stream areas) independent of background condition. Our results clarify the processing stage at which attention modulates object location representations in the ventral visual stream and show that attentional modulation is a cognitive process separate from recurrent processes related to the processing of objects on cluttered backgrounds.

Parietofrontal oscillations show hand-specific interactions with top-down movement plans

To generate a hand-specific reach plan, the brain must integrate hand-specific signals with the desired movement strategy. Although various neurophysiology/imaging studies have investigated hand-target interactions in simple reach-to-target tasks, the whole brain timing and distribution of this process remain unclear, especially for more complex, instruction-dependent motor strategies. Previously, we showed that a pro/anti pointing instruction influences magnetoencephalographic (MEG) signals in frontal cortex that then propagate recurrently through parietal cortex (Blohm G, Alikhanian H, Gaetz W, Goltz HC, DeSouza JF, Cheyne DO, Crawford JD. NeuroImage 197: 306-319, 2019). Here, we contrasted left versus right hand pointing in the same task to investigate 1) which cortical regions of interest show hand specificity and 2) which of those areas interact with the instructed motor plan. Eight bilateral areas, the parietooccipital junction (POJ), superior parietooccipital cortex (SPOC), supramarginal gyrus (SMG), medial/anterior interparietal sulcus (mIPS/aIPS), primary somatosensory/motor cortex (S1/M1), and dorsal premotor cortex (PMd), showed hand-specific changes in beta band power, with four of these (M1, S1, SMG, aIPS) showing robust activation before movement onset. M1, SMG, SPOC, and aIPS showed significant interactions between contralateral hand specificity and the instructed motor plan but not with bottom-up target signals. Separate hand/motor signals emerged relatively early and lasted through execution, whereas hand-motor interactions only occurred close to movement onset. Taken together with our previous results, these findings show that instruction-dependent motor plans emerge in frontal cortex and interact recurrently with hand-specific parietofrontal signals before movement onset to produce hand-specific motor behaviors.NEW & NOTEWORTHY The brain must generate different motor signals depending on which hand is used. The distribution and timing of hand use/instructed motor plan integration are not understood at the whole brain level. Using MEG we show that different action planning subnetworks code for hand usage and integrating hand use into a hand-specific motor plan. The timing indicates that frontal cortex first creates a general motor plan and then integrates hand specificity to produce a hand-specific motor plan.

Flexible attention system: Appearance time of split attention changes in accordance with the task difficulty level

Although it is often assumed that spatial attention exists in the form of a unitary focus, the split-attention hypothesis proposes that attention can be simultaneously divided into two spatially noncontiguous positions and that the space in between can be ignored. However, whether split attention occurs directly based on the generation of attentional benefit or whether it requires a gradual divide from a unitary focus over time has not been clarified. In the present study, by using two spatial salient cues to direct the attention allocation of participants, we aimed to investigate whether attention requires time to divide from a unitary focus and whether the appearance time of split attention varies when the task difficulty level increases between experiments. The results showed that attention required time to divide from a unitary focus, and the position between the two cued positions was not excluded by attention when the stimulus-onset asynchrony (SOA) was 60 ms. However, as the task difficulty increased between experiments, the appearance time of split attention was earlier. These findings suggest that the appearance time of split attention has a certain flexibility and can be changed according to the task requirement, thus implying that split attention and unitary attention present some common attention mechanisms and that a split or unitary mode can be flexibly selected for an attention system.

Modulation of the Earliest Component of the Human VEP by Spatial Attention: An Investigation of Task Demands

Spatial attention modulations of initial afferent activity in area V1, indexed by the first component “C1” of the human visual evoked potential, are rarely found. It has thus been suggested that early modulation is induced only by special task conditions, but what these conditions are remains unknown. Recent failed replications—findings of no C1 modulation using a certain task that had previously produced robust modulations—present a strong basis for examining this question. We ran 3 experiments, the first to more exactly replicate the stimulus and behavioral conditions of the original task, and the second and third to manipulate 2 key factors that differed in the failed replication studies: the provision of informative performance feedback, and the degree to which the probed stimulus features matched those facilitating target perception. Although there was an overall significant C1 modulation of 11%, individually, only experiments 1 and 2 showed reliable effects, underlining that the modulations do occur but not consistently. Better feedback induced greater P1, but not C1, modulations. Target-probe feature matching had an inconsistent influence on modulation patterns, with behavioral performance differences and signal-overlap analyses suggesting interference from extrastriate modulations as a potential cause.

Neural underpinnings of dyslexia as a disorder of visuo‐spatial attention

For nearly 100 years, the underlying cause of dyslexia has been a matter of much debate, with widely varying viewpoints that have ranged from considering dyslexia as largely a learning disability to claims that it is essentially a perceptual defect occurring early along the visual pathway. This paper reviews some of this literature with particular reference to the studies that have implicated a defect in the afferent visual pathways in the aetiology of the disorder, then goes on to outline a neural theory of how functionally distinct parallel pathways in vision interact with each other in the process of reading and suggests how a defect in these pathways can lead to reading difficulties. Central to the proposed scheme is the suggestion that a fast-track pathway, arising from the magnocellular cells in the retina and acting through an attentional mechanism, has a gating function in spotlighting the individual letters of a text in a sequential fashion. That such gating occurs at the level of the primary visual cortex is supported by recent physiological evidence concerning attentional mechanisms.

Shifting Attention in Feature Space: Fast Facilitation of the To-Be-Attended Feature Is Followed by Slow Inhibition of the To-Be-Ignored Feature

In an explorative study, we investigated the time course of attentional selection shifts in feature-based attention in early visual cortex by means of steady-state visual evoked potentials (SSVEPs). To this end, we presented four flickering random dot kinematograms with red/blue, horizontal/vertical bars, respectively. Given the oscillatory nature of SSVEPs, we were able to investigate neural temporal dynamics of facilitation and inhibition/suppression when participants shifted attention either within (i.e., color to color) or between feature dimensions (i.e., color to orientation). Extending a previous study of our laboratory [Müller, M. M., Trautmann, M., & Keitel, C. Early visual cortex dynamics during top-down modulated shifts of feature-selective attention. Journal of Cognitive Neuroscience, 28, 643-655, 2016] to a full factorial design, we replicated a critical finding of our previous study: Facilitation of color was quickest, regardless of the origin of the shift (from color or orientation). Furthermore, facilitation of the newly to-be-attended and inhibition/suppression of the then to-be-ignored feature is not a time-invariant process that occurs instantaneously, but a biphasic one with longer time delays between the two processes. Interestingly, inhibition/suppression of the to-be-ignored feature after the shifting cue had a much longer latency with between- compared to within-dimensional shifts (by about 130-150 msec). The exploratory nature of our study is reasoned by two limiting factors: (a) Identical to our precursor study, we found no attentional SSVEP amplitude time course modulation for orientation, and (b) the signal-to-noise ratio for single trials was too poor to allow for reliable statistical testing of the latencies that were obtained with running t tests of averaged data.

Spatial attention modulates earliest visual processing: An electrical neuroimaging study

Several studies showed that shifting of visuospatial attention modulates sensory processing at multiple levels of the visual pathways and beyond, including the occipital striate cortices level. However, inconsistent findings have been reported thus leaving these issues still disputed. 21 participants took part to the present study (the EEG signals of 4 of them were discarded due to artifacts). We used ERPs and their neural sources to investigate whether shifting spatial attention in space across the horizontal meridian of the visual field affected striate cortices activation at the earliest latency. Time-series of scalp topographical maps indicated that, unlike ERPs to attentional-neutral central cues, ERPs to attention-directing local cues showed earliest polarity inversions as a function of stimulated field and processing latency range considered, at occipital-parietal electrodes. In between 60-75 ms, attentional shifting cues elicited a positivity for both visual fields, whereas at a later latency (75–90 ms) they elicited a positivity and a negativity for the upper and lower visual hemifields, respectively. Computed neural sources included striate, besides extrastriate, cortices for both visual hemifields and latency ranges. Conjointly, behavioral responses to targets were faster when they were preceded by local than by neutral cues, and when presented in the upper than the lower hemifield. Our findings support the hypothesis that attention shifts may affect early sensory processing in visual cortices.

Reliability analysis of individual visual P1 and N1 maps indicates the heterogeneous topographies involved in early visual processing among human subjects

There is a lack of studies regarding the reliability of the event-related components (ERPs) of an electroencephalogram (EEG) used to assess cognitive processing in human subjects. To explore the reliability scores for the P1 and N1 components in two sessions (separated by an average of 116 days), twenty subjects performed a visual lateralized detection paradigm and EEG recording (58 channels) were employed. The session factor did not modulate the P1/N1 latencies. The visual field factor (left (LVF) or right (RVF)) was a determinant for the P1 and N1 topographical distributions as shown in previous studies. Moreover, topographical maps of the grand average showed a very strong correlation level between sessions (>0.9). Finally, individual maps demonstrated that the classic contralateral pattern for the P1 and N1 components was not always present in all subjects. In particular, compared to the N1 component, the P1 component exhibited a more complex set of individual topographical distributions, revealing that some steps are more heterogeneous among human subjects in early visual processing.

No Evidence that Predictions and Attention Modulate the First Feedforward Sweep of Cortical Information Processing

Predictive coding models propose that predictions (stimulus likelihood) reduce sensory signals as early as primary visual cortex (V1), and that attention (stimulus relevance) can modulate these effects. Indeed, both prediction and attention have been shown to modulate V1 activity, albeit with fMRI, which has low temporal resolution. This leaves it unclear whether these effects reflect a modulation of the first feedforward sweep of visual information processing and/or later, feedback-related activity. In two experiments, we used electroencephalography and orthogonally manipulated spatial predictions and attention to address this issue. Although clear top-down biases were found, as reflected in pre-stimulus alpha-band activity, we found no evidence for top-down effects on the earliest visual cortical processing stage (<80 ms post-stimulus), as indexed by the amplitude of the C1 event-related potential component and multivariate pattern analyses. These findings indicate that initial visual afferent activity may be impenetrable to top-down influences by spatial prediction and attention.

Feed-forward visual processing suffices for coarse localization but fine-grained localization in an attention-demanding context needs feedback processing

It is well known that simple visual tasks, such as object detection or categorization, can be performed within a short period of time, suggesting the sufficiency of feed-forward visual processing. However, more complex visual tasks, such as fine-grained localization may require high-resolution information available at the early processing levels in the visual hierarchy. To access this information using a top-down approach, feedback processing would need to traverse several stages in the visual hierarchy and each step in this traversal takes processing time. In the present study, we compared the processing time required to complete object categorization and localization by varying presentation duration and complexity of natural scene stimuli. We hypothesized that performance would be asymptotic at shorter presentation durations when feed-forward processing suffices for visual tasks, whereas performance would gradually improve as images are presented longer if the tasks rely on feedback processing. In Experiment 1, where simple images were presented, both object categorization and localization performance sharply improved until 100 ms of presentation then it leveled off. These results are a replication of previously reported rapid categorization effects but they do not support the role of feedback processing in localization tasks, indicating that feed-forward processing enables coarse localization in relatively simple visual scenes. In Experiment 2, the same tasks were performed but more attention-demanding and ecologically valid images were used as stimuli. Unlike in Experiment 1, both object categorization performance and localization precision gradually improved as stimulus presentation duration became longer. This finding suggests that complex visual tasks that require visual scrutiny call for top-down feedback processing.

Self-Construal Priming Affects Holistic Face Processing and Race Categorization, but Not Face Recognition

Self-construal priming can affect an individual’s cognitive processing. Participants who were primed with interdependent self-construal showed more holistic process bias than those who were primed with independent self-construal. The holistic processing of a face also differs across cultures. As such, the purpose of the present study was to explore whether the cultural differences in holistic face processing can be interpreted from the perspective of self-construal, as well as to investigate the relationship between self-construal and holistic face processing/face recognition/race categorization. In Experiment 1, participants were primed with control, interdependent, or independent self-construal, respectively, and then they completed a feature-space same-different task (Experiment 1A) or a composite face effect task (Experiment 1B). Results showed no priming effect in Experiment 1A, whereas independent self-construal priming resulted in less holistic processing in Experiment 1B. In Experiment 2, participants were primed with control, collective/interdependent, relational, or independent self-construal, respectively, and then they completed a Vanderbilt Holistic Face Processing Test and Cambridge Face Memory Test. Participants who were primed as independent showed greater congruency effect than the relational group. Self-construal priming had no effect on face recognition. In Experiment 3, we manipulated self-construal in the same way as that in Experiment 2 and monitored the eye movement of Chinese participants while they learned, recognized, and categorized their own-/other-race faces. Self-construal priming had no effect on face recognition. Compared with other groups, collective-/interdependent-self priming increased the fixation time of eyes and decreased the fixation time of nose in the race categorization task. These results indicated that the cultural differences in self-construal could not mirror the cultural differences in face processing in a simple way.

Functional MRI and EEG Index Complementary Attentional Modulations

Functional magnetic resonance imaging (fMRI) and electroencephalography (EEG) are two noninvasive methods commonly used to study neural mechanisms supporting visual attention in humans. Studies using these tools, which have complementary spatial and temporal resolutions, implicitly assume they index similar underlying neural modulations related to external stimulus and internal attentional manipulations. Accordingly, they are often used interchangeably for constraining understanding about the impact of bottom-up and top-down factors on neural modulations. To test this core assumption, we simultaneously manipulated bottom-up sensory inputs by varying stimulus contrast and top-down cognitive modulations by changing the focus of spatial attention. Each of the male and female subjects participated in both fMRI and EEG sessions performing the same experimental paradigm. We found categorically different patterns of attentional modulation on fMRI activity in early visual cortex and early stimulus-evoked potentials measured via EEG (e.g., the P1 component and steady-state visually-evoked potentials): fMRI activation scaled additively with attention, whereas evoked EEG components scaled multiplicatively with attention. However, across longer time scales, a contralateral negative-going potential and oscillatory EEG signals in the alpha band revealed additive attentional modulation patterns like those observed with fMRI. These results challenge prior assumptions that fMRI and early stimulus-evoked potentials measured with EEG can be interchangeably used to index the same neural mechanisms of attentional modulations at different spatiotemporal scales. Instead, fMRI measures of attentional modulations are more closely linked with later EEG components and alpha-band oscillations. Considered together, hemodynamic and electrophysiological signals can jointly constrain understanding of the neural mechanisms supporting cognition.SIGNIFICANCE STATEMENT fMRI and EEG have been used as tools to measure the location and timing of attentional modulations in visual cortex and are often used interchangeably for constraining computational models under the assumption that they index similar underlying neural processes. However, by varying attentional and stimulus parameters, we found differential patterns of attentional modulations of fMRI activity in early visual cortex and commonly used stimulus-evoked potentials measured via EEG. Instead, across longer time scales, a contralateral negative-going potential and EEG oscillations in the alpha band exhibited attentional modulations similar to those observed with fMRI. Together, these results suggest that different physiological processes assayed by these complementary techniques must be jointly considered when making inferences about the neural underpinnings of cognitive operations.

Orienting spatial attention to sounds enhances visual processing

Attention, the mechanism by which information is selected for further processing, has mostly been studied within the visual system. While this research has been exceptionally successful, it is important to understand how attention operates across the sensory modalities. This review focuses on recent studies showing that orienting to a peripheral, salient sound affects visual processing: it enhances visual perception, boosts visual-cortical responses, and modulates visual cortex activity before the appearance of a visual object. Critically, all of these effects are spatially selective, indicating that spatial attention facilitates perceptual processing at an attended location across sensory modalities. The neural changes in visual cortex triggered by the sounds not only resemble some of the neural modulations reported in uni-modal visual attention studies, but also reveal some important differences.

Neural Correlates of Enhanced Visual Attentional Control in Action Video Game Players: An Event-Related Potential Study

Action video game players (AVGPs) outperform non–action video game players (NAVGPs) on a range of perceptual and attentional tasks. Although several studies have reported neuroplastic changes within the frontoparietal networks of attention in AVGPs, little is known about possible changes in attentional modulation in low-level visual areas. To assess the contribution of these different levels of neural processing to the perceptual and attentional enhancements noted in AVGPs, visual event-related potentials (ERPs) were recorded from 14 AVGPs and 14 NAVGPs during a target discrimination task that required participants to attend to rapid sequences of Gabor patches under either focused or divided attention conditions. AVGPs responded faster to target Gabors in the focused attention condition compared with the NAVGPs. Correspondingly, ERPs to standard Gabors revealed a more pronounced negativity in the time range of the parietally generated anterior N1 component in AVGPs compared with NAVGPs during focused attention. In addition, the P2 component of the visual ERP was more pronounced in AVGPs than in NAVGPs over the hemisphere contralateral to the stimulus position in response to standard Gabors. Contrary to predictions, however, attention-modulated occipital components generated in the low-level extrastriate visual pathways, including the P1 and posterior N1, showed no significant group differences. Thus, the main neural signature of enhanced perceptual and attentional control functions in AVGPs appears linked to an attention-dependent parietal process, indexed by the anterior N1 component, and possibly to more efficient higher-order perceptual processing, indexed by the P2 component.

Differential effects of learned associations with words and pseudowords on event-related brain potentials

Associated stimulus valence affects neural responses at an early processing stage. However, in the field of written language processing, it is unclear whether semantics of a word or low-level visual features affect early neural processing advantages. The current study aimed to investigate the role of semantic content on reward and loss associations. Participants completed a learning session to associate either words (Experiment 1, N = 24) or pseudowords (Experiment 2, N = 24) with different monetary outcomes (gain-associated, neutral or loss-associated). Gain-associated stimuli were learned fastest. Behavioural and neural response changes based on the associated outcome were further investigated in separate test sessions. Responses were faster towards gain- and loss-associated than neutral stimuli if they were words, but not pseudowords. Early P1 effects of associated outcome occurred for both pseudowords and words. Specifically, loss-association resulted in increased P1 amplitudes to pseudowords, compared to decreased amplitudes to words. Although visual features are likely to explain P1 effects for pseudowords, the inversed effect for words suggests that semantic content affects associative learning, potentially leading to stronger associations.

Electrophysiological Measure of Impaired Information Processing in Drivers with Hematological Malignancy

The broad goal of this study is to measure remote effects of cancer on brain physiology and behaviors that underpin instrumental activities of daily living such as automobile driving. Studies of hematological malignancies (HM) have demonstrated impairments in multiple brain functions shown to be critical for safe automobile driving. In the current pilot study, brain physiology during driving simulation was examined in 14 HM patients and 13 healthy comparison drivers. Electroencephalography was used to measure the eye fixation-related potential (EFRP)-a positive amplitude deflection evoked approximately 100 milliseconds after eye movement termination. Previous studies have demonstrated sensitivity of EFRP activity to information-processing capacity. All drivers completed visual search tasks to evaluate the relationship between driving-related changes in performance and EFRP activity. Results showed smaller EFRP amplitudes in drivers who had: (1) greater driving-related changes in visual search performance (p = 0.03, Cohen's d = 0.91); and (2) HM diagnosis (p = 0.18, Cohen's d = 0.54). Extending previous studies, these results provide neural evidence of reduced information-processing capacity associated with cancer diagnosis. Future large-scale studies are needed to confirm these results, given the high level of uncertainty and small sample size. This study provides a novel platform for linking changes in brain physiology and safety-critical driving behaviors.

How Ocular Dominance and Binocularity Are Reflected by the Population Receptive Field Properties

Purpose

The neural substrate of binocularity and sighting ocular dominance in humans is not clear. By utilizing the population receptive field (pRF) modeling technique, we explored whether these phenomena are associated with amplitude and pRF size differences.

Methods

The visual field maps of 13 subjects were scanned (3-T Skyra) while viewing drifting bar stimuli. Both eyes (binocular condition), the dominant eye and the nondominant eye (two monocular conditions) were stimulated in separate sessions. For each condition, pRF size and amplitude were assessed. Binocular summation ratios were calculated by dividing binocular by mean monocular values (amplitude and pRF size).

Results

No differences in pRF size were seen between the viewing conditions within each region, that is, either between binocular and monocular or between dominant and nondominant viewing conditions. Binocular amplitudes were higher than the monocular amplitudes, but similar among the dominant and nondominant eyes. Binocular summation ratios derived from amplitudes were significantly higher than one (∼1.2), while those ratios derived from pRF size were not. These effects were found in all studied areas along the visual hierarchy, starting in V1.

Conclusions

Neither the amplitude nor the pRF size show intereye difference and therefore cannot explain the different roles of the dominant and the nondominant eyes. Binocular, as compared to monocular vision, resulted in higher amplitudes, while receptive fields' sizes were similar, suggesting increased binocular response intensity as the basis for the binocular summation phenomenon. Our results could be applicable in imaging studies of monocular disease and studies that deal with nondisparity binocularity effects.

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.

Temporal and spectral EEG dynamics can be indicators of stealth placement

Stealth placement marketing, where consumers are unaware that they are being marketed to, attempts to reduce the audiences' resistance to traditional persuasive advertising. It is a form of advertising that involves targeted exposure of brands or products incorporated in other works, usually with or without explicit reference to the brands or products. Brand placement can be presented in different visual and auditory forms in video programs. The present study proposed that different 'representations' (i.e., representable or non-representable) and 'sounds' (i.e., speech or musical sound) of brand placement can affect the viewers' perception of the brand. Event-related potential results indicated significant differences in P1, N1, P2, N270, and P3. Further, event-related spectral perturbation results indicated significant differences in theta, alpha, beta, and gamma (30-100 Hz), in the right parietal, right occipital area, and limbic lobe. 'Non-representable' or 'speech sound' brand placement induced significant temporal and spectral EEG dynamics in viewers.

The engagement of cortical areas preceding exogenous vergence eye movements

Source analyses on event related potentials (ERPs) derived from the electroencephalogram (EEG) were performed to examine the respective roles of cortical areas preceding exogenously triggered saccades, combined convergences, and combined divergences. All eye movements were triggered by the offset of a central fixation light emitting diode (LED) and the onset of a lateral LED at various depths in an otherwise fully darkened room. Our analyses revealed that three source pairs, two located in the frontal lobe–the frontal eye fields (FEF) and an anterior frontal area–, and one located within the occipital cortex, can account for 99.2% of the observed ERPs. Overall, the comparison between source activities revealed the largest activity in the occipital cortex, while no difference in activity between FEF and the anterior frontal area was obtained. For all sources, increased activity was observed for combined vergences, especially combined convergences, relative to saccades. Behavioral results revealed that onset latencies were longest for combined convergences, intermediate for combined divergences, and the shortest for saccades. Together, these findings fit within a perspective in which both occipital and frontal areas play an important role in retinal disparity detection. In the case of saccades and combined divergences stimulus-locked activity was larger than response-locked activity, while no difference between stimulus- and response-locked activity was observed for combined convergences. These findings seem to imply that the electrophysiological activity preceding exogenous eye movements consists of a sensory-related part that is under cortical control, while subcortical structures may be held responsible for final execution.

Attentional ERPs distinguish aging and early Alzheimer's dementia

The early detection of Alzheimer's disease requires our distinguishing it from cognitive aging. Here, we test whether spatial attentional changes might support that distinction. We engaged young normal (YN), older normal (ON), and patients with early Alzheimer's dementia (EAD) in an attentionally cued, self-movement heading discrimination task while we recorded push-button response times and event related potentials. YNs and ONs show the behavioral effects of attentional shifts from the cue to the target, whereas EAD patients did not (p < 0.001). YNs and ONs also show the shifting lateralization of a newly described attentional event related potentials component, whereas EAD patients did not (p < 0.001). Our findings suggest that spatial inattention in EAD patients may contribute to heading direction processing impairments that distinguish them from ONs and undermine their navigational capacity and driving safety.

Detailed spatiotemporal brain mapping of chromatic vision combining high-resolution VEP with fMRI and retinotopy

Neuroimaging studies have identified so far, several color-sensitive visual areas in the human brain, and the temporal dynamics of these activities have been separately investigated using the visual-evoked potentials (VEPs). In the present study, we combined electrophysiological and neuroimaging methods to determine a detailed spatiotemporal profile of chromatic VEP and to localize its neural generators. The accuracy of the present co-registration study was obtained by combining standard fMRI data with retinotopic and motion mapping data at the individual level. We found a sequence of occipito activities more complex than that typically reported for chromatic VEPs, including feed-forward and reentrant feedback. Results showed that chromatic human perception arises by the combined activity of at the least five parieto-occipital areas including V1, LOC, V8/VO, and the motion-sensitive dorsal region MT+. However, the contribution of V1 and V8/VO seems dominant because the re-entrant activity in these areas was present more than once (twice in V8/VO and thrice in V1). This feedforward and feedback chromatic processing appears delayed compared with the luminance processing. Associating VEPs and neuroimaging measures, we showed for the first time a complex spatiotemporal pattern of activity, confirming that chromatic stimuli produce intricate interactions of many different brain dorsal and ventral areas.

Weak surround suppression of the attentional focus characterizes visual selection in the ventral stream in autism

Neurophysiological findings in the typical population demonstrate that spatial scrutiny for visual selection determines a center-surround profile of the attentional focus, which is the result of recurrent processing in the visual system. Individuals with autism spectrum disorder (ASD) manifest several anomalies in their visual selection, with strengths in detail-oriented tasks, but also difficulties in distractor inhibition tasks. Here, we asked whether contradictory aspects of perception in ASD might be due to a different center-surround profile of their attentional focus. In two experiments, we tested two independent samples of children with ASD, comparing them with typically developing (TD) peers. In Experiment 1, we used a psychophysical task that mapped the entire spatial profile of the attentional focus. In Experiment 2, we used dense-array electroencephalography (EEG) to explore its neurophysiological underpinnings. Experiment 1 results showed that the suppression, surrounding the attentional focus, was markedly reduced in children with ASD. Experiment 2 showed that the center-surround profile in TD children resulted in a modulation of the posterior N2 ERP component, with cortical sources in the lateral-occipital and medial/inferior temporal areas. In contrast, children with ASD did not show modulation of the N2 and related activations in the ventral visual stream. Furthermore, behavioural and neurophysiological measures of weaker suppression predicted more severe autistic symptomatology. The present findings, showing an altered center-surround profile during attentional selection, give an important insight to understand superior visual processing in autism as well as the experiencing of sensory overload.

Selecting multiple features delays perception, but only when targets are horizontally arranged

Based on the finding that perception is lagged by attention split on multiple features (Lo et al., 2012), this study investigated how the feature-based lag effect interacts with the target spatial arrangement. Participants were presented with gratings the spatial frequencies of which constantly changed. The task was to monitor two gratings of the same or different colors and report their spatial frequencies right before the stimulus offset. The results showed a perceptual lag wherein the reported value was closer to the physical value some time prior to the stimulus offset. This lag effect was larger when the two gratings were of different colors than when they were the same color. Furthermore, the feature-based lag effect was statistically significant when the two gratings were horizontally arranged but not when they were vertically or diagonally arranged. A model is proposed to explain the effect of target arrangement: When targets are horizontally arranged, selecting an additional feature delays perception. When targets are vertically or diagonally arranged, target selection for the lower field is prioritized. This prioritization on the lower target might prompt observers to only select the lower target and ignore the upper one, and this causes more perceptual errors without delaying perception.

Several studies with significant C1 attention effects survive critical analysis

In a discussion paper (Slotnick, this issue), I conducted a selective review of spatial attention studies to compare experimental parameters and determine whether particular stimulus, task, or analysis conditions were more likely to produce significant attentional modulation of the event-related potential (ERP) C1 component. It was concluded that to maximize C1 attention effects, stimuli should be in the upper visual field, there should be distractors, conditions should be high perceptual or attentional load, there should be exogenous cuing, and effects should be measured at midline parietal-occipital electrodes POz, Pz, and CPz. Commentaries were received by Fu (this issue), Qu and Ding (this issue), Zani and Proverbio (this issue), Pitts and Hillyard (this issue), Di Russo (this issue), and Mohr and Kelly (this issue). Comments included additional ideas to amplify C1 attention effects, support for some conclusions, and challenges to some conclusions. The challenges led to a more in depth analysis of many issues pertaining to C1 attention effects including optimal electrode and stimulus locations, null V1 source localization attention effects, whether all significant C1 attention effects can be discounted, and the number of studies with null versus significant C1 attention effects. Analysis of the studies that survived critical analysis, which included several that observed significant C1 attention effects, led to the same conclusions as Slotnick (this issue). Lines of future research include replicating studies that have observed C1 attention effects using identical experimental parameters and systematically manipulating parameters to determine the impact of each parameter on C1 spatial attention effects.

Attentional modulation of early visual areas

This special issue of Cognitive Neuroscience focuses on the debate regarding whether spatial attention can rapidly modulate the event-related potential (ERP) C1 component, which reflects the initial feedforward signal in V1. A discussion paper by Baumgartner, Graulty, Hillyard, and Pitts (this issue) included an empirical experiment that failed to replicate the significant C1 attention effects of Kelly, Gomez-Ramirez, and Foxe. Commentaries were received by Ding (this issue), Klein (this issue), Pourtois, Rossi, Vuilleumier, and Rauss (this issue), Kelly and Mohr (this issue), Slagter, Alilovic, and Van Gaal (this issue), and Fu (this issue). The author response highlighted that C1 attention effects may be obtained in only limited conditions, considered problems of investigating C1 attention effects, and proposed future strategies. An empirical paper by Herde, Rossi, Pourtois, and Rauss (this issue) found that C1 was modulated by stimulus predictability, which indicates higher-level cognitive processes can modulate V1. A second discussion paper (Slotnick, this issue) compared experimental parameters across spatial attention studies and concluded certain stimulus, task, and analysis conditions were more likely to produce significant C1 attention effects. Commentaries were received by Fu (this issue), Qu and Ding (this issue), Zani and Proverbio (this issue), Pitts and Hillyard (this issue), Di Russo (this issue), and Mohr and Kelly (this issue). The author response included a more in depth analysis, and several studies that observed significant C1 attention effects survived critical analysis. The topics considered in this issue have clarified the current state of this debate and provided directions for future research.

The spatiotemporal characteristics of the C1 component and its modulation by attention

Slotnick (this issue) provided a selective review of studies on the attentional modulation of the C1 component of the visual evoked potential, and offers a number of guidelines to maximize the likelihood of observing such modulation in terms of electrode choice, stimulus placement, and types of attentional cue and target stimulus. However, the broader literature pertaining to attentional modulation of the C1 does not support many of these guidelines, and the question of why exactly C1 modulations are so rare remains very much open. Here, we provide clarifications that are critical to an accurate appraisal of the current state of this literature.

Still wanted: a reproducible demonstration of a genuine C1 attention effect

Slotnick (this issue) has specified a number of experimental parameters that appear critical for enabling an attention-related modulation of the C1 component. These include stimulus presentation in the upper visual field, the presence of distractors, a high perceptual or attentional load, and measurements at midline occipito-parietal sites. While we agree with many of these recommendations, we would modify others and even dispute a few. Despite the employment of these parameters in a few existing studies, there has not yet been a convincing, reproducible demonstration of a modulation of the C1 component by spatial attention that can be localized to primary visual cortex.

Grounding by Attention Simulation in Peripersonal Space: Pupils Dilate to Pinch Grip But Not Big Size Nominal Classifier

Grammatical categories represent implicit knowledge, and it is not known if such abstract linguistic knowledge can be continuously grounded in real-life experiences, nor is it known what types of mental states can be simulated. A former study showed that attention bias in peripersonal space (PPS) affects reaction times in grammatical congruency judgments of nominal classifiers, suggesting that simulated semantics may include reenactment of attention. In this study, we contrasted a Chinese nominal classifier used with nouns denoting pinch grip objects with a classifier for nouns with big object referents in a pupil dilation experiment. Twenty Chinese native speakers read grammatical and ungrammatical classifier-noun combinations and made grammaticality judgment while their pupillary responses were measured. It was found that their pupils dilated significantly more to the pinch grip classifier than to the big object classifier, indicating attention simulation in PPS. Pupil dilations were also significantly larger with congruent trials on the whole than in incongruent trials, but crucially, congruency and classifier semantics were independent of each other. No such effects were found in controls.

Does spatial attention modulate the earliest component of the visual evoked potential?

Whether visual spatial attention can modulate feedforward input to human primary visual cortex (V1) is debated. A prominent and long-standing hypothesis is that visual spatial attention can influence processing in V1, but only at delayed latencies suggesting a feedback-mediated mechanism and a lack of modulation during the initial afferent volley. The most promising challenge to this hypothesis comes from an event-related potential (ERP) study that showed an amplitude enhancement of the earliest visual ERP component, called the 'C1', in response to spatially attended relative to spatially unattended stimuli. In the Kelly et al. study, several important experimental design modifications were introduced, including tailoring the stimulus locations and recording electrodes to each individual subject. In the current study, we employed the same methodological procedures and tested for attentional enhancements of the C1 component in each quadrant of the visual field. Using the same analysis strategies as Kelly et al., we found no evidence for an attention-based modulation of the C1 (measured from 50-80 ms). Attention-based amplitude enhancements were clear and robust for the subsequent P1 component (90-140 ms). Thus, despite using methods specifically designed to reveal C1 attention effects, the current study provided no confirmatory evidence for such effects.

Colour categories are reflected in sensory stages of colour perception when stimulus issues are resolved

Debate exists about the time course of the effect of colour categories on visual processing. We investigated the effect of colour categories for two groups who differed in whether they categorised a blue-green boundary colour as the same- or different-category to a reliably-named blue colour and a reliably-named green colour. Colour differences were equated in just-noticeable differences to be equally discriminable. We analysed event-related potentials for these colours elicited on a passive visual oddball task and investigated the time course of categorical effects on colour processing. Support for category effects was found 100 ms after stimulus onset, and over frontal sites around 250 ms, suggesting that colour naming affects both early sensory and later stages of chromatic processing.

Interrelation of attention and prediction in visual processing: Effects of task-relevance and stimulus probability

The potentially interactive influence of attention and prediction was investigated by measuring event-related potentials (ERPs) in a spatial cueing task with attention (task-relevant) and prediction (probabilistic) cues. We identified distinct processing stages of this interactive influence. Firstly, in line with the attentional gain hypothesis, a larger amplitude response of the contralateral N1, and Nd1 for attended gratings was observed. Secondly, conforming to the attenuation-by-prediction hypothesis, a smaller negativity in the time window directly following the peak of the N1 component for predicted compared to unpredicted gratings was observed. In line with the hypothesis that attention and prediction interface, unpredicted/unattended stimuli elicited a larger negativity at central-parietal sites, presumably reflecting an increased prediction error signal. Thirdly, larger P3 responses to unpredicted stimuli pointed to the updating of an internal model. Attention and prediction can be considered as differentiated mechanisms that may interact at different processing stages to optimise perception.

The Relation between Infant Covert Orienting, Sustained Attention and Brain Activity

This study used measures of event-related potentials (ERPs) and cortical source analysis to examine the effect of covert orienting and sustained attention on 3- and 4.5-month-old infants' brain activity in a spatial cueing paradigm. Cortical source analysis was conducted with current density reconstruction using realistic head models created from age-appropriate infant MRIs. The validity effect was found in the P1 ERP component that was greater for valid than neutral trials in the electrodes contralateral to the visual targets when the stimulus onset asynchrony (SOA) was short. Cortical source analysis revealed greater current density amplitude around the P1 peak latency in the contralateral inferior occipital and ventral temporal regions for valid than neutral and invalid trials. The processing cost effect was found in the N1 ERP component that was greater for neutral than invalid trials in the short SOA condition. This processing cost effect was also shown in the current density amplitude around the N1 peak latency in the contralateral inferior and middle occipital and middle and superior temporal regions. Infant sustained attention was found to modulate infants' brain responses in covert orienting by enhancing the P1 ERP responses and current density amplitude in their cortical sources during sustained attention. These findings suggest that the neural mechanisms that underpin covert orienting already exist in 3- to 4.5-month-old, and they could be facilitated by infant sustained attention.

Attentional Gating in Primary Visual Cortex: A Physiological Basis for Dyslexia

The visual magnocellular pathway is known to play a central part in visuospatial attention and in directing attention to specific parts of the visual world in serial search. It is proposed that, in the case of reading, this mechanism is trained to perform a sequential gating of visual information coming into the primary visual cortex to enable further orderly processing by the ventral stream. This scheme, taken together with the potential for plasticity between the different afferent channels in the case of a relative impairment of the magnocellular system, can provide some limited rationale for the beneficial effects that have been claimed for the use of coloured overlays and glasses.

A Preliminary Investigation of the Time Course of Attention Bias Variability in Posttraumatic Stress Disorder: The Moderating Role of Attentional Control

The present study sought to explicate the time-course of posttraumatic stress (PTS)-related attentional bias to threat (ABT) by examining differences in attention bias variability (ABV; a measure which accounts for the temporal dynamics of ABT). A dot-probe task with four presentation durations was used to capture both subliminal and supraliminal stages of processing. Task stimuli consisted of neutral and threat images. Attentional control (AC) was examined as a moderator of the relationship between PTSD and ABV. At an experimental session, participants (PTSD = 11, trauma control = 18) completed questionnaires, a modified dot-probe task, and a stimulus-response task measuring AC. Individuals in the PTSD group exhibited greater ABV compared to trauma control participants. AC moderated this relationship, with participants with PTSD and poor AC exhibiting significantly greater ABV than trauma-exposed control participants with poor AC. These effects remained significant after accounting for traditionally calculated ABT scores and variability on trials for which only neutral stimuli were present, thus ensuring that the observed effects were specific to the presence of threat stimuli and not merely a function of general variability in response times. Findings implicate AC as a buffering mechanism against threat-related attentional dyscontrol among those with PTSD. Clinical implications will be discussed.

Early Visual Cortex Dynamics during Top–Down Modulated Shifts of Feature-Selective Attention

Shifting attention from one color to another color or from color to another feature dimension such as shape or orientation is imperative when searching for a certain object in a cluttered scene. Most attention models that emphasize feature-based selection implicitly assume that all shifts in feature-selective attention underlie identical temporal dynamics. Here, we recorded time courses of behavioral data and steady-state visual evoked potentials (SSVEPs), an objective electrophysiological measure of neural dynamics in early visual cortex to investigate temporal dynamics when participants shifted attention from color or orientation toward color or orientation, respectively. SSVEPs were elicited by four random dot kinematograms that flickered at different frequencies. Each random dot kinematogram was composed of dashes that uniquely combined two features from the dimensions color (red or blue) and orientation (slash or backslash). Participants were cued to attend to one feature (such as color or orientation) and respond to coherent motion targets of the to-be-attended feature. We found that shifts toward color occurred earlier after the shifting cue compared with shifts toward orientation, regardless of the original feature (i.e., color or orientation). This was paralleled in SSVEP amplitude modulations as well as in the time course of behavioral data. Overall, our results suggest different neural dynamics during shifts of attention from color and orientation and the respective shifting destinations, namely, either toward color or toward orientation.

A multi-pathway hypothesis for human visual fear signaling

A hypothesis is proposed for five visual fear signaling pathways in humans, based on an analysis of anatomical connectivity from primate studies and human functional connectvity and tractography from brain imaging studies. Earlier work has identified possible subcortical and cortical fear pathways known as the "low road" and "high road," which arrive at the amygdala independently. In addition to a subcortical pathway, we propose four cortical signaling pathways in humans along the visual ventral stream. All four of these traverse through the LGN to the visual cortex (VC) and branching off at the inferior temporal area, with one projection directly to the amygdala; another traversing the orbitofrontal cortex; and two others passing through the parietal and then prefrontal cortex, one excitatory pathway via the ventral-medial area and one regulatory pathway via the ventral-lateral area. These pathways have progressively longer propagation latencies and may have progressively evolved with brain development to take advantage of higher-level processing. Using the anatomical path lengths and latency estimates for each of these five pathways, predictions are made for the relative processing times at selective ROIs and arrival at the amygdala, based on the presentation of a fear-relevant visual stimulus. Partial verification of the temporal dynamics of this hypothesis might be accomplished using experimental MEG analysis. Possible experimental protocols are suggested.

It's not all in your car: functional and structural correlates of exceptional driving skills in professional racers

Driving is a complex behavior that requires the integration of multiple cognitive functions. While many studies have investigated brain activity related to driving simulation under distinct conditions, little is known about the brain morphological and functional architecture in professional competitive driving, which requires exceptional motor and navigational skills. Here, 11 professional racing-car drivers and 11 “naïve” volunteers underwent both structural and functional brain magnetic resonance imaging (MRI) scans. Subjects were presented with short movies depicting a Formula One car racing in four different official circuits. Brain activity was assessed in terms of regional response, using an Inter-Subject Correlation (ISC) approach, and regional interactions by mean of functional connectivity. In addition, voxel-based morphometry (VBM) was used to identify specific structural differences between the two groups and potential interactions with functional differences detected by the ISC analysis. Relative to non-experienced drivers, professional drivers showed a more consistent recruitment of motor control and spatial navigation devoted areas, including premotor/motor cortex, striatum, anterior, and posterior cingulate cortex and retrosplenial cortex, precuneus, middle temporal cortex, and parahippocampus. Moreover, some of these brain regions, including the retrosplenial cortex, also had an increased gray matter density in professional car drivers. Furthermore, the retrosplenial cortex, which has been previously associated with the storage of observer-independent spatial maps, revealed a specific correlation with the individual driver's success in official competitions. These findings indicate that the brain functional and structural organization in highly trained racing-car drivers differs from that of subjects with an ordinary driving experience, suggesting that specific anatomo-functional changes may subtend the attainment of exceptional driving performance.

Earliest stages of visual cortical processing are not modified by attentional load

This study investigated the effects of attentional load on neural responses to attended and irrelevant visual stimuli by recording high-density event-related potentials (ERPs) from the scalp in normal adult subjects. Peripheral (upper and lower visual field) and central stimuli were presented in random order at a rapid rate while subjects responded to targets among the central stimuli. Color detection and color-orientation conjunction search tasks were used as the low- and high-load tasks, respectively. Behavioral results showed significant load effects on both accuracy and reaction time for target detections. ERP results revealed no significant load effect on the initial C1 component (60-100 ms) evoked by either central-relevant or peripheral-irrelevant stimuli. Source analysis with dipole modeling confirmed previous reports that the C1 includes the initial evoked response in primary visual cortex. Source analyses indicated that high attentional load enhanced the early (70-140 ms) neural response to central-relevant stimuli in ventral-lateral extrastriate cortex, whereas load effects on peripheral-irrelevant stimulus processing started at 110 ms and were localized to more dorsal and anterior extrastriate cortical areas. These results provide evidence that the earliest stages of visual cortical processing are not modified by attentional load and show that attentional load affects the processing of task relevant and irrelevant stimuli in different ways.

Early recurrent feedback facilitates visual object recognition under challenging conditions

Standard models of the visual object recognition pathway hold that a largely feedforward process from the retina through inferotemporal cortex leads to object identification. A subsequent feedback process originating in frontoparietal areas through reciprocal connections to striate cortex provides attentional support to salient or behaviorally-relevant features. Here, we review mounting evidence that feedback signals also originate within extrastriate regions and begin during the initial feedforward process. This feedback process is temporally dissociable from attention and provides important functions such as grouping, associational reinforcement, and filling-in of features. Local feedback signals operating concurrently with feedforward processing are important for object identification in noisy real-world situations, particularly when objects are partially occluded, unclear, or otherwise ambiguous. Altogether, the dissociation of early and late feedback processes presented here expands on current models of object identification, and suggests a dual role for descending feedback projections.

Neural correlates of attention to emotional facial expressions in dysphoria

The present study investigated whether dysphoric individuals have a difficulty in disengaging attention from negative stimuli and/or reduced attention to positive information. Sad, neutral and happy facial stimuli were presented in an attention-shifting task to 18 dysphoric and 18 control participants. Reaction times to neutral shapes (squares and diamonds) and the event-related potentials to emotional faces were recorded. Dysphoric individuals did not show impaired attentional disengagement from sad faces or facilitated disengagement from happy faces. Right occipital lateralisation of P100 was absent in dysphoric individuals, possibly indicating reduced attention-related sensory facilitation for faces. Frontal P200 was largest for sad faces among dysphoric individuals, whereas controls showed larger amplitude to both sad and happy as compared with neutral expressions, suggesting that dysphoric individuals deployed early attention to sad, but not happy, expressions. Importantly, the results were obtained controlling for the participants' trait anxiety. We conclude that at least under some circumstances the presence of depressive symptoms can modulate early, automatic stages of emotional processing.