Søren K AndersenUniversity of Southern Denmark | SDU
Søren K Andersen
Professor
Establishing new EEG lab. Looking for PostDoc interested in joining via Marie Curie Postdoctoral Fellowship application.
About
77
Publications
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2,603
Citations
Introduction
Additional affiliations
August 2014 - present
March 2013 - July 2014
September 2010 - February 2013
Education
April 2004 - March 2007
September 1998 - March 2004
Publications
Publications (77)
Research on attentional selection of stimulus features has yielded seemingly contradictory results. On the one hand, many experiments in humans and animals have observed a “global” facilitation of attended features across the entire visual field, even when spatial attention is focused on a single location. On the other hand, several event-related p...
Steady-state visual evoked potentials (SSVEPs) are a powerful tool for investigating selective attention. Here, we conducted a combined reanalysis of multiple studies employing this technique in a variety of attentional experiments to, first, establish benchmark effect sizes of attention on amplitude and phase of SSVEPs and, second, harness the pow...
Biological systems must allocate limited percgeptual resources to relevant elements in their environment. This often requires simultaneous selection of multiple elements from the same feature dimension (e.g. colour). To establish the determinants of divided attentional selection of hue, we conducted an experiment that used multicoloured displays wi...
Action video game players (AVGPs) outperform nonvideo game players (NVGPs) on a wide variety of attentional tasks, mediating benefits to perceptual and cognitive decision processes. A key issue in the literature is the extent to which such benefits transfer beyond cognition. Using steady-state visual evoked potentials (SSVEP) as a neural measure of...
Keeping track of the location of multiple moving objects is one of the well documented functions of visual attention. However, the mechanism of attentional selection that supports such continuous tracking is unclear. In particular, it has been proposed that target selection in early visual cortex occurs in parallel, with tracking errors arising due...
Multisensory stimulation is associated with behavioural benefits, including faster processing speed, higher detection accuracy, and increased subjective awareness. These effects are most likely explained by multisensory integration, alertness, or a combination of the two. To examine changes in subjective awareness under multisensory stimulation, we...
Distractor suppression refers to the ability to filter out distracting and task-irrelevant information. Distractor suppression is essential for survival and considered a key aspect of selective attention. Despite the recent and rapidly evolving literature on distractor suppression, we still know little about how the brain suppresses distracting inf...
Distractor suppression refers to the ability to filter out distracting and task-irrelevant information. Distractor suppression is essential for survival and considered a key aspect of selective attention. Despite the recent and rapidly evolving literature on distractor suppression, we still know little about how distracting information is suppresse...
Reward enhances stimulus processing in the visual cortex, but the mechanisms through which this effect occurs remain unclear. Reward prospect can both increase the deployment of voluntary attention and increase the salience of previously neutral stimuli. In this study, we orthogonally manipulated reward and voluntary attention while human participa...
Reward enhances stimulus processing in the visual cortex, but the mechanisms through which this effect occurs remain unclear. Reward prospect can both increase the deployment of voluntary attention and increase the salience of previously neutral stimuli. In this study we orthogonally manipulated reward and voluntary attention while human participan...
Evidence for the influence of unaware signals on behaviour has been reported in both patient groups and healthy observers using the Redundant Signal Effect (RSE). The RSE refers to faster manual reaction times to the onset of multiple simultaneously presented target than those to a single stimulus. These findings are robust and apply to unimodal an...
Colors are represented in the cone-opponent signals, L-M vs S cones, at least up to the level of inputs to the primary visual cortex. We explored the hue selective responses in early cortical visual areas through recordings of steady-state visual evoked potentials (SSVEPs), elicited by a flickering checkerboard whose color smoothly swept around the...
Selective attention focuses visual processing on relevant stimuli in order to allow for adaptive behaviour despite an abundance of distracting information. It has been proposed that increases in alpha band (8 - 12 Hz) amplitude reflect an active mechanism for distractor suppression. If this were the case, increases in alpha band amplitude should be...
Selective attention can enhance the processing of attended features across the entire visual field. Attention also spreads within objects, enhancing all internal locations and task-irrelevant features of selected objects. Here, we examine the extent to which attentional enhancement of a feature spreads across attended and unattended objects. Two fu...
Selective attention may mainly act by enhancing attended or suppressing unattended information. In most experiments, cues indicate to-be-attended rather than to-be-ignored stimuli, thereby potentially biasing selection towards enhancement. Here, we compared cued shifts of feature-selective attention between conditions in which attended stimuli were...
In natural vision, processing of spatial and nonspatial features occurs simultaneously; however, the two types of attention in charge of facilitating this processing have distinct mechanisms. Here, we tested the independence of spatial and feature-based attention at different stages of visual processing by examining color-based attentional selectio...
This study aimed to analyze the covert attentional time course in early body processing areas in women with high body concerns. Therefore, we assessed the effect of pictures of one's own body and other bodies as distractions from a demanding dot detection task in 24 women with low and 20 women with high body concerns. Participants were instructed t...
Objective::
The ability to perceive the motion of biological objects, such as faces, is a critical component of daily function and correlates with the ability to successfully navigate social situations (social cognition). Deficits in motion perception in schizophrenia were first demonstrated about 20 years ago but remain understudied, especially i...
Directing attention to task-relevant stimuli is crucial for successful task performance, but too much attentional selectivity implies that new and unexpected information in the environment remains undetected. A possible mechanism for optimizing this fundamental trade-off could be an error monitoring system that immediately triggers attentional adju...
Visual object recognition is essential for adaptive interactions with the environment. It is fundamentally limited by crowding, a breakdown of object recognition in clutter. The spatial extent over which crowding occurs is proportional to the eccentricity of the target object, but nevertheless varies substantially depending on various stimulus fact...
Alpha band (8–12 Hz) amplitude increases have been proposed to reflect an active mechanism for distractor suppression. To test this hypothesis, we concurrently recorded alpha band activity and steady-state visual evoked potentials (SSVEPs) elicited by attended and unattended stimuli. Participants covertly attended one of two bilateral letter stream...
Cortical networks that process colour and luminance signals are often studied separately, although colour appearance depends on both colour and luminance. In fact, objects in everyday life are very rarely defined by only colour or only luminance, necessitating an investigation into combined processing of these signals. We used steady-state visual e...
A key property of feature-based attention is global facilitation of the attended feature throughout the visual field. Previously, we presented superimposed red and blue randomly moving dot kinematograms (RDKs) flickering at a different frequency each to elicit frequency-specific steady-state visual evoked potentials (SSVEPs) that allowed us to anal...
Short-term memory (STM) encompasses cognitive functions for the storage, maintenance, and mental manipulation of information that is no longer present in the sensory environment. Selective attention, on the other hand, relates to functions that modulate the processing of sensory events during encoding. We review evidence from a series of three tact...
Background
Steady-state visual evoked potentials have been utilized widely in basic and applied research in recent years. These oscillatory responses of the visual cortex are elicited by flickering stimuli. They have the same fundamental frequency as the driving stimulus and are highly sensitive to manipulations of attention and stimulus properties...
Unlabelled:
Experiments that study feature-based attention have often examined situations in which selection is based on a single feature (e.g., the color red). However, in more complex situations relevant stimuli may not be set apart from other stimuli by a single defining property but by a specific combination of features. Here, we examined sust...
Previous research on attentional selection of features has yielded seemingly contradictory results: many experiments have found "global" facilitation of attended features across the entire visual field, whereas classic event related potential (ERP) studies reported an enhancement of attended features at the attended location only. To test the hypot...
In many common situations such as driving an automobile it is advantageous to attend concurrently to events at different locations (e.g., the car in front, the pedestrian to the side). While spatial attention can be divided effectively between separate locations, studies investigating attention to nonspatial features have often reported a “global e...
Keeping track of multiple moving objects is an essential ability of visual perception. However, the mechanisms underlying this ability are not well understood. We instructed human observers to track five or seven independent randomly moving target objects amid identical nontargets and recorded steady-state visual evoked potentials (SSVEPs) elicited...
Objectives:
Combining behavioral and neurophysiological measurements inevitably implies mutual constraints, such as when the neurophysiological measurement requires fast-paced stimulus presentation and hence the attribution of a behavioral response to a particular preceding stimulus becomes ambiguous. We develop and test a method for validly asses...
Orienting attention to locations in mnemonic representations engages processes that functionally and anatomically overlap the neural circuitry guiding prospective shifts of spatial attention. The attention-based rehearsal account predicts that the requirement to withdraw attention from a memorized location impairs memory accuracy. In a dual-task st...
Previous studies of feature-selective attention have focused on situations in which attention is directed to one of two spatially superimposed stimuli of equal salience. While such overlapping stimuli should maximize stimulus interactions, it is still unknown how bottom-up biases favoring one or the other stimulus influence the efficiency of featur...
It has been shown in both animal and human studies that attentional selection of simple features (e.g. color) enhances processing of this feature across the entire visual field, i.e. it is spatially global. However, it remains unclear whether such global facilitation of features is mandatory or whether it can remain spatially local when the task re...
A better understanding of age-related change in the attentional modulation of perceptual processing may help elucidate cognitive change. For example, increased cognitive interference due to inappropriate processing of irrelevant information has been suggested to contribute to cognitive decline. However, it is not yet clear whether interference effe...
Flickering stimuli evoke an oscillatory brain response with the same frequency as the driving stimulus, the so-called steady-state visual evoked potential (SSVEP). SSVEPs are robust brain signals whose amplitudes are enhanced with attention and thus play a major role in the development and use of non-invasive Brain-Computer Interfaces (BCIs). We co...
Attention filters behaviorally relevant stimuli from the constant stream of sensory information comprising our environment. Research into underlying neural mechanisms in humans suggests that visual attention biases mutual suppression between stimuli resulting from competition for limited processing resources. As a consequence, processing of an atte...
The focus of attention can be flexibly altered in mnemonic representations of past sensory events. We investigated the neural mechanisms of selection in tactile STM by applying vibrotactile sample stimuli of different intensities to both hands, followed by a symmetrically shaped visual retro-cue. The retro-cue indicated whether the weak or strong s...
Numerous studies have found that emotionally arousing faces or scenes capture visual processing resources. Here we investigated whether emotional distractor words capture attention in an analogous way. Participants detected brief intervals of coherent motion in an array of otherwise randomly moving squares superimposed on words of positive, neutral...
A central controversy in the field of attention is how the brain deals with emotional distractors and to what extent they capture attentional processing resources reflexively due to their inherent significance for guidance of adaptive behavior and survival. Especially, the time course of competitive interactions in early visual areas and whether ma...
According to the attention-based rehearsal hypothesis, maintenance of spatial information is mediated by covert orienting towards memorized locations. In a somatosensory memory task, participants simultaneously received bilateral pairs of mechanical sample pulses. For each hand, sample stimuli were randomly assigned to one of three locations (finge...
Selective attention to a primary task can be biased by the occurrence of emotional distractors that involuntary attract attention due to their intrinsic stimulus significance. What is largely unknown is the time course and magnitude of competitive interactions between a to-be-attended foreground task and emotional distractors. We used pleasant, unp...
Multiple concurrently presented stimuli are thought to compete for neuronal processing resources. Such competitive stimulus interactions can be investigated by "frequency tagging" each stimulus with an individual temporal frequency. In this case, all stimuli will drive distinct steady-state visual evoked potentials (SSVEPs), hence allowing for an a...
A central question in the field of attention is whether visual processing is a strictly limited resource, which must be allocated by selective attention. If this were the case, attentional enhancement of one stimulus should invariably lead to suppression of unattended distracter stimuli. Here we examine voluntary cued shifts of feature-selective at...
Recent studies have suggested that the extent to which primary task demands draw on attentional resources determines whether or not task-irrelevant emotional stimuli are processed. Another important factor that can bias task-relevant and task-irrelevant stimulus competition is the bottom-up factor of stimulus salience. Here, we investigated the eff...
Although attention in older adults is an active research area, feature-selective aspects have not yet been explicitly studied. Here we report the results of an exploratory study involving directed changes in feature-selective attention. The stimuli used were two random dot kinematograms (RDKs) of different colours, superimposed and centrally presen...
We investigated intermodal attention effects on the auditory steady-state response (ASSR) and the steady-state visual evoked potential (SSVEP). For this purpose, 40-Hz amplitude-modulated tones and a stream of flickering (7.5 Hz) random letters were presented concurrently. By means of an auditory or visual target detection task, participants’ atten...
We investigated mechanisms of concurrent attentional selection of location and color using electrophysiological measures in human subjects. Two completely overlapping random dot kinematograms (RDKs) of two different colors were presented on either side of a central fixation cross. On each trial, participants attended one of these four RDKs, defined...
It is well-established that attention can select stimuli for preferential processing on the basis of non-spatial features such as color, orientation, or direction of motion. Evidence is mixed, however, as to whether feature-selective attention acts by increasing the signal strength of to-be-attended features irrespective of their spatial locations...
High-arousing emotional stimuli facilitate early visual cortex, thereby acting as strong competitors for processing resources
in visual cortex. The present study used an electrophysiological approach for continuously measuring the time course of competition
for processing resources in the visual pathway arising from emotionally salient but task-irr...
Successfully locating a dangerous or desirable object within a cluttered visual scene is a commonplace yet highly adaptive skill. In the laboratory, this ability is modeled by visual search experiments in which subjects try to find a target item surrounded by an array of distracting stimuli. Under certain conditions, targets that are distinguishabl...
Multiple objects in a visual scene compete for neuronal representation. We investigated competitive neuronal dynamics in cortical networks of early visual processing in the human brain. Coloured picture streams flickered at 7.42 Hz, evoking the steady-state visual evoked potential (SSVEP), an electrophysiological response of neuronal populations in...
We used an electrophysiological measure of selective stimulus processing (the steady-state visual evoked potential, SSVEP) to investigate feature-specific attention to color cues. Subjects viewed a display consisting of spatially intermingled red and blue dots that continually shifted their positions at random. The red and blue dots flickered at di...
Questions
Question (1)
We are considering to obtain a Jazz eye tracker to be used in conjunction with our existing BioSemi EEG amplifiers. I would be very interested in hearing what experiences other labs have made with such a setup. How convenient and reliable is it to use? How much calibration is necessary? Does the head-mounted eye tracker cause artifacts in the EEG? Is it comfortable for the participant to wear? Is there an easy way to feed back the eye movement data to the stimulation PC during the experiment (e.g. using the Psychophysics Toolbox) or is it suitable mainly for offline analysis together with the EEG data?
