Morten Overgaard

Morten Overgaard
Aarhus University | AU · Cognitive Neuroscience Research Unit CNRU

About

124
Publications
33,661
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
3,537
Citations

Publications

Publications (124)
Article
In the search for the neural correlates of consciousness, it is often assumed that there is a stable set within the relevant sensory modality. Within the visual modality, the debate has centred upon whether frontal or occipital activations are the best predictors of perceptual awareness. While not accepted by all as definitive evidence, no‐report a...
Article
Full-text available
Double-blinding subjects to the experiment's purpose is an important standard in neurofeedback studies. However, it is difficult to provide evidence that humans are entirely unaware of certain information. This study used insights from consciousness studies and neurophenomenology to develop a contingency awareness questionnaire for neurofeedback. W...
Article
Full-text available
Neurofeedback is a procedure that measures brain activity in real-time and presents it as feedback to an individual, thus allowing them to self-regulate brain activity with effects on cognitive processes inferred from behavior. One common argument is that neurofeedback studies can reveal how the measured brain activity causes a particular cognitive...
Article
Full-text available
Under labels such as unconscious processing and subliminal perception, identification of stimuli falling below the subjective threshold (whether truly unconscious or not) has been found remarkably accurate in some experiments while completely at chance in others. Here, we first identify that an apparent window of subliminal perception arises in hum...
Article
Full-text available
Accurate insight into subjective experience is crucial for the science of consciousness. The Perceptual Awareness Scale (PAS) was created in 2004 as a method for obtaining precise introspective reports for participants in research projects, and since then, the scale has become increasingly popular. This does not mean, of course, that no critiques h...
Article
Spontaneous neural oscillations are key predictors of perceptual decisions to bind multisensory signals into a unified percept. Research links decreased alpha power in the posterior cortices to attention and audiovisual binding in the sound-induced flash illusion (SIFI) paradigm. This suggests that controlling alpha oscillations would be a way of c...
Article
The Perceptual Awareness Scale (PAS) is often used to probe conscious experience, but the assumptions behind the scale and its validity are rarely tested. Using a continuous colour estimation task to assess perceptual quality, we focus on how well PAS follows perceptual quality and how the presence of the estimation task affects PAS ratings. We var...
Article
Full-text available
The theoretical landscape of scientific studies of consciousness has flourished. Today, even multiple versions of the same theory are sometimes available. To advance the field, these theories should be directly compared to determine which are better at predicting and explaining empirical data. Systematic inquiries of this sort are seen in many subf...
Article
Full-text available
Perceptual decision-making employs a range of higher order metacognitive processes. Two of the most important of these are perceptual awareness; or the clarity with which one reports seeing a perceptual stimulus, and response confidence; or the certainty one has about the correctness of one's own perceptual categorizations. We used a novel false fe...
Article
Full-text available
The question of consciousness in other species, not least species very physically different from humans such as insects, is highly challenging for a number of reasons. One reason is that we do not have any available empirical method to answer the question. Another reason is that current theories of consciousness disagree about the relation between...
Article
People often claim seeing images completely despite performing poorly. This highlights an issue with conscious representations. We introduce an experimental manipulation aiming to disentangle two prevalent positions: Rich views posit that people virtually represent the external world with unlimited capacity; Sparse views state that representations...
Article
In recent years, independent subfields have started to engage with the idea that the same cortical regions that contribute to online perception are recruited during and underlie offline activities like information maintenance in working memory, mental imagery, hallucinations, dreaming, and mind wandering. Accumulating evidence suggests that in all...
Preprint
Full-text available
A patient who does not regain full consciousness after coma is typically classified as being in a vegetative state or a minimally conscious state. While the key determinants in this differential diagnosis are inferred uniquely from the observed behaviour of the patient, nothing can, in principle, be known about the patient's awareness of the extern...
Article
Full-text available
In an attempt to improve attention bias modification (ABM), we tested whether an attentional training protocol which featured monetary operant conditioning of eye-gaze to avoid alcohol stimuli in alcohol-dependent patients could reduce attention, craving and relapse to alcohol. We employed a pilot randomized control trial (RCT) with 21 detoxified a...
Article
Studies of the neural correlates of consciousness (NCCs) combining MEG/EEG with behavioral data have described two main time ranges relating to conscious perception: 130-320 (the visual awareness negativity; VAN) and 300-500 (P3a) ms after stimulus onset. At the same time, two event-related potential (ERP) peaks have shown an emotional modulation o...
Article
It is widely believed that visual expectations can change the subjective experiences of humans. We investigated how visual expectations in a recognition task affected objective performance and subjective perception. Using a 2-alternative-forced-choice task based on digit recognition of briefly presented and visually masked digits, we found over two...
Article
Full-text available
Abstract Rationale Identifying the predictors of relapse in detoxified alcohol-dependent patients is crucial for effective surveillance procedures and the optimization of treatment. Physiological measures such as functional MRI activity and heart rate variability have been shown as potential markers of relapse prediction. Objectives Our aim was to...
Preprint
Hypnosis has been successfully applied in neurorehabilitation, including for motor disorders, aphasia, pain, and vertigo. However, cognitive rehabilitation using hypnosis has received little attention. Here, we report the data from two such studies on patients with chronic cognitive sequalae following acquired brain injury. Eight sessions of hypnot...
Article
Reports of white dreams, the feeling of having had a dream experience without being able to specify this experience any further, make up almost one third of all dream reports, yet this phenomenon—until very recently—had not yet been in the focus of targeted investigations. White dreams are typically interpreted as forgotten dreams, and are sideline...
Article
Full-text available
The problem of perceptual consciousness—the question of how our subjective experiences (colours as we see them; sounds as we hear them; tastes, etc., as we feel them) could be accounted for in terms of brain processes—is often regarded as the greatest unsolved mystery of our times. In recent literature, one of the most pressing questions in this re...
Article
Full-text available
In consciousness research, it is common to distinguish between phenomenal consciousness and access consciousness. Recently, a number of scientists have attempted to show that phenomenal content can be empirically separated from cognitive access and, accordingly, that the mental content that is accessed is not (always) identical to the content that...
Article
In the present communication, phenomenal consciousness, access consciousness and the closely related concept of working memory are presented in the context of a neurocognitive model—the REF (reorganization of elementary functions) framework. The REF framework is based on connectionist networks within which the ‘units’ are advanced processing module...
Article
In this Letter to the Editor, we seize the opportunity to respond to the recent comments by Anzulewicz and Wierzchoń, and further clarify and extend the scope of our original paper. We re‐emphasize that conscious experiences come in degrees, and that there are several factors that determine this degree. Endorsing the suggestions of Anzulewicz and W...
Preprint
Working memory impairment is prevalent in brain injured patients across lesion aetiologies and severities. Unfortunately, rehabilitation efforts for this impairment have hitherto yielded small- or no effects. Here we show in a randomized actively controlled trial that working memory performance can be effectively restored by suggesting to hypnotize...
Article
Full-text available
Most experiments in consciousness research assume that awareness is a dichotomous 'either/or' phenomenon. However, participants can distinguish multiple levels of subjective experience of simple features (colour, shape etc.), which correlate with their performance in different tasks. As experiments showing multiple levels of perceptual awareness qu...
Article
Full-text available
In the present paper it is argued that the “neural correlate of consciousness” (NCC) does not appear to be a separate “module” – but an aspect of information processing within the neural substrate of various cognitive processes. Consequently, NCC can only be addressed adequately within frameworks that model the general relationship between neural p...
Article
Full-text available
The question of whether conscious experience is best viewed as graded or dichotomous has received much scientific attention in recent years as the answer is relevant not only to models of consciousness, but also to the examination of neural markers of consciousness in patients and infants. Although some studies have found evidence of graded percept...
Data
Modelled probability of using each PAS-rating. How likely were participants (N:Pilot = 16;Experiment 1 = 16;Experiment 2 = 30; Experiment 3 = 16) to use each PAS-rating? PAS-rating under the Control and Illusion condition generally appeared to be comparable. Error bars represent 95% Confidence intervals. (TIF)
Data
Inducer configurations (Experiment 3). Left side: Inducers configured to induce perception of an illusory triangle in either the upper or lower visual field (illusion condition). The lines would always be presented in the illusory triangle. Right side: Inducers configured to avoid inducing perception of an illusory triangle (control condition). The...
Data
Probability of categorising the upper line as the longest (Experiment 3, Upper Triangle). Probabilities are reported for each awareness rating and for each line length condition. When participants (n = 16) rated “no experience” (PAS1), they did not perform statistically different from chance level. As awareness increased (PAS2-4), the probability o...
Data
Exploratory analysis of illusion effect across stimulus durations (pilot experiment). A) Probability of using the PAS2 rating on a trial as a function of stimulus duration (n = 16). B) Bias for reporting the upper line as longer in the illusion condition (compared to control condition) is plotted as a function of stimulus duration for PAS2 ratings...
Data
AIC-values for the Simple–and Full models for each PAS-rating, each experiment. The Full model includes whether the illusion was presented or not. The lowest value for each model is marked with bold. A lower AIC-value for the full model indicates that the illusion influenced participant’s line judgement in a measurable way. For all experiments, the...
Data
Probability of categorising the upper line as the longest (Pilot Experiment). Probabilities are reported for each awareness rating and for each line length condition. When participants (n = 16) rated “no experience” (PAS1), they did not perform statistically different from chance level. As awareness increased (PAS2-4), the probability of correct cl...
Data
Probability of categorising the upper line as the longest (Experiment 3, Lower Triangle). Probabilities are reported for each awareness rating and for each line length condition. When participants (n = 16) rated “no experience” (PAS1), they did not perform statistically different from chance level. As awareness increased (PAS2-4), the probability o...
Article
In this paper we argue that awareness comes in degrees, and we propose a novel multi-factor account that spans both subjective experiences and perceptual representations. At the subjective level, we argue that conscious experiences can be degraded by being fragmented, less salient, too generic, or flash-like. At the representational level, we ident...
Article
Full-text available
The relation between first and higher order mental states is currently unknown. In particular, the relation between conscious experience and introspection is difficult as the same methods are used to investigate them. In order to make progress in the scientific understanding of consciousness, introspection or both, it is fundamental to understand w...
Article
Object-substitution masking (OSM) occurs when a briefly displayed target in a search array is surrounded by a mask, which remains onscreen after the target has disappeared. It has been suggested that OSM results from a specific interference with reentrant visual processing, while the initial feedforward processing is left intact. Here, we tested th...
Article
Full-text available
We describe a patient LS, profoundly deaf in both ears from birth, with underdeveloped superior temporal gyri. Without hearing aids, LS displays no ability to detect sounds below a fixed threshold of 60 dBs, which classifies him as clinically deaf. Under these no-hearing-aid conditions, when presented with a forced-choice paradigm in which he is as...
Article
Full-text available
Working memory impairment is prevalent in brain injured patients across lesion aetiologies and severities. Unfortunately, rehabilitation efforts for this impairment have hitherto yielded small or no effects. Here we show in a randomized actively controlled trial that working memory performance can be effectively restored by suggesting to hypnotized...
Article
Full-text available
Introduction: An impairment of visually perceiving backward masked stimuli is commonly observed in patients with schizophrenia, yet it is unclear whether this impairment is the result of a deficiency in first or higher order processing and for which subtypes of schizophrenia it is present. Methods: Here, we compare identification (first order) and...
Article
Guidelines for submitting commentsPolicy: Comments that contribute to the discussion of the article will be posted within approximately three business days. We do not accept anonymous comments. Please include your email address; the address will not be displayed in the posted comment. Cell Press Editors will screen the comments to ensure that they...
Article
Full-text available
In the past decades, sense of control—the feeling that one is in control of one’s actions has gained much scientific interests. Various scales have been used to measure sense of control in previous studies, yet no study has allowed participants to create a scale for rating their control experiences despite advances in the neighboring field of consc...
Article
Full-text available
We present a study investigating how the delay between the intention to act and the following action, influenced the experience of action. In experiments investigating sense of agency and experience of action, the contrast is most often between voluntary and involuntary actions. It is rarely asked whether different types of intentions influence the...
Article
Full-text available
Two electrophysiological components have been extensively investigated as candidate neural correlates of perceptual consciousness: An early, occipitally realized component occurring 130-320 ms after stimulus onset and a late, frontally realized component occurring 320-510 ms after stimulus onset. Recent studies have suggested that the late componen...
Article
Full-text available
Contrasting conditions with and without awareness has been the preferred method for investigating the neural correlates of consciousness (NCC) for decades, yet recently it has been suggested that further insights can be made by moving beyond this method, specifically by meticulously controlling that potential precursors and consequences of the NCC...
Article
Full-text available
Copyright statement: © 2014 Michael, Sandberg, Skewes, Wolf, Blicher, Overgaard and Frith. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution and reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original...
Article
Full-text available
Exclusion tasks have been proposed as objective measures of unconscious perception as they do not depend upon subjective ratings. In exclusion tasks, participants have to complete a task without using a previously presented prime. Use of the prime is taken as evidence for unconscious processing in the absence of awareness, yet it may also simply in...
Article
The contents of consciousness and of short-term memory are hard to disentangle. As it seems intuitive that we represent attended objects in short-term memory and in experience, to many, it also seems intuitive to equate this content. Here we investigated memory resolution for orientation of a probed target in combination with a conscious evaluation...
Article
Object substitution masking (OSM) occurs when a briefly presented target in a search array is surrounded by small dots that remain visible after the target disappears. The reduction of target visibility occurring after OSM has been suggested to result from a specific interference with reentrant visual processing. Here, we tested a prediction derive...
Article
After decades of research, blindsight is still a mysterious and controversial topic in consciousness research. Currently, many researchers tend to think of it as an ideal phenomenon to investigate neural correlates of consciousness, whereas others believe that blindsight is in fact a kind of degraded vision rather than “truly blind”. This article c...
Article
Full-text available
During binocular rivalry, visual perception alternates spontaneously between two different monocular images. Such perceptual reversals are slowed or halted if stimuli are presented intermittently with inter-stimulus intervals larger than ~400ms - a phenomenon called stabilization. Often, the neural correlates of reversal and stabilization are studi...
Article
Full-text available
This article proposes a new model to interpret seemingly conflicting evidence concerning the correlation of consciousness and neural processes. Based on an analysis of research of blindsight and subliminal perception, the reorganization of elementary functions and consciousness framework suggests that mental representations consist of functions at...
Article
Full-text available
Although it is well established that regions of premotor cortex (PMC) are active during action observation, it remains controversial whether they play a causal role in action understanding. In the experiment reported here, we used off-line continuous theta-burst stimulation (cTBS) to investigate this question. Participants received cTBS over the ha...
Article
Full-text available
Object-substitution masking (OSM) occurs when a briefly presented target in a search array is surrounded by small dots that remain visible after the target disappears. The reduction of target visibility occurring after OSM has been suggested to result from a specific interference with reentrant visual processing while the initial feedforward proces...
Article
Our subjective confidence about particular events is related to but independent from the objective certainty of the stimuli we encounter. Surprisingly, previous investigations of the neurophysiological correlates of confidence and uncertainty have largely been carried out separately. After systematically reviewing the blood oxygenation-level depend...
Article
Full-text available
Studies indicate that conscious perception is related to changes in neural activity within a time window that varies between 130 and 320 msec after stimulus presentation, yet it is not known whether such neural correlates of conscious perception are stable across time. Here, we examined the generalization across time within individuals and across d...
Article
The role of conscious intention in relation to motoric movements has become a major topic of investigation in neuroscience. Traditionally, reports of conscious intention have been compared to various features of the readiness-potential (RP) - an electrophysiological signal that appears before voluntary movements. Experiments, however, tend to study...
Article
Full-text available
How do we know whether our own actions were voluntary or involuntary? Intentional theories of sense of agency suggest that we consciously perceive the intentions that accompany our actions, but reconstructive theories suggest that we perceive our actions only through the body movements and other effects that they produce. Intentions would then be m...
Article
Full-text available
One of the most common forms of synesthesia is between colors and graphemes (Colizoli, Murre, & Rouw, 2012). Numerous studies have investigated different aspects of attention and synesthesia, e.g. effects of Stroop-like interference by colors that are incongruent with the synesthetic experience. Here we attempt to isolate how specific components of...
Article
Full-text available
Previous studies indicate that conscious face perception may be related to neural activity in a large time window around 170-800 msec after stimulus presentation, yet in the majority of these studies changes in conscious experience are confounded with changes in physical stimulation. Using multivariate classification on MEG data recorded when parti...