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Antti Revonsuo - One of the best experts on this subject based on the ideXlab platform.
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Subjective Visual Awareness emerges prior to P3.
European Journal of Neuroscience, 2016Co-Authors: Mika Koivisto, Niina Salminen-vaparanta, Simone Grassini, Antti RevonsuoAbstract:Studies on the neural basis of Visual Awareness, the subjective experience of seeing, have found several potential neural correlates of Visual Awareness. Some of them may not directly correlate with Awareness but with post-perceptual processes, such as reporting one's Awareness of the stimulus. We dissociated potential electrophysiological correlates of Visual Awareness from those occurring during response selection and thus co-occurring with post-perceptual processing. The participants performed two GO-NOGO conditions. In the aware-GO condition they responded with a key press when they were aware of the stimulus and withheld responding when they were unaware of it. In the unaware-GO condition they withheld responding when they were aware and responded when they were not aware of the stimulus. Thus, event-related potentials could be measured to aware and unaware trials when responding was required and when not required. The results revealed that the N200 amplitude (180-280 ms) over the occipital and posterior temporal cortex was enhanced in aware trials as compared with trials without Awareness. This effect (Visual Awareness negativity, VAN) did not depend on responding. The amplitude of P3 (350-450 ms) also was enhanced in aware trials as compared with unaware trials. In addition, the amplitudes in the P3 time window depended on responding: they were greater when Awareness was mapped to GO-response than when not, suggesting that P3 reflects post-perceptual processing, that is, it occurs after Awareness has emerged. These findings support theories of Visual Awareness that assume a relatively early onset of Visual Awareness before P3.
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Neuronavigated transcranial magnetic stimulation suggests that area V2 is necessary for Visual Awareness.
Neuropsychologia, 2012Co-Authors: Niina Salminen-vaparanta, Mika Koivisto, Valdas Noreika, Simo Vanni, Antti RevonsuoAbstract:Abstract The primary Visual cortex (V1) has been shown to be critical for Visual Awareness, but the importance of other low-level Visual areas has remained unclear. To clarify the role of human cortical area V2 in Visual Awareness, we applied transcranial magnetic stimulation (TMS) over V2 while participants were carrying out a Visual discrimination task and rating their subjective Awareness. Individual retinotopic maps and modelling of the TMS-induced electric field in V1, V2 and V3d ensured that the electric field was at or under the phosphene threshold level in V1 and V3d, whereas in V2 it was at the higher suppressive level. As earlier shown for the V1, our results imply that also V2 is necessary for conscious Visual experience. Visual Awareness of stimulus presence was completely suppressed when the TMS pulse was delivered 44–84 ms after the onset of Visual stimulus. Visual discrimination and Awareness of stimulus features was impaired when the TMS pulse was delivered 44–104 ms after the Visual stimulus onset. These results suggest that Visual Awareness cannot be generated without an intact V2.
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Event-related brain potential correlates of Visual Awareness
Neuroscience & Biobehavioral Reviews, 2010Co-Authors: Mika Koivisto, Antti RevonsuoAbstract:Electrophysiological recordings during Visual tasks can shed light on the temporal dynamics of the subjective experience of seeing, Visual Awareness. This paper reviews studies on electrophysiological correlates of Visual Awareness operationalized as the difference between event-related potentials (ERPs) in response to stimuli that enter Awareness and stimuli that do not. There are three candidates for such a correlate: enhancement of P1 around 100 ms, enhancement of early posterior negativity around 200 ms (Visual Awareness negativity, VAN), and enhancement of late positivity (LP) in the P3 time window around 400 ms. Review of studies using different manipulations of Awareness suggests that VAN is the correlate of Visual Awareness that most consistently emerges across different manipulations of Visual Awareness. VAN emerges also relatively independent of manipulations of nonspatial attention, but seems to be dependent on spatial attention. The results suggest that Visual Awareness emerges about 200 ms after the onset of Visual stimulation as a consequence of the activation of posterior occipitotemporal and parietal networks.
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The earliest electrophysiological correlate of Visual Awareness
Brain and Cognition, 2008Co-Authors: Mika Koivisto, Mikko Lähteenmäki, Thomas Alrik Sørensen, Signe Vangkilde, Morten Overgaard, Antti RevonsuoAbstract:To examine the neural correlates and timing of human Visual Awareness, we recorded event-related potentials (ERPs) in two experiments while the observers were detecting a grey dot that was presented near subjective threshold. ERPs were averaged for conscious detections of the stimulus (hits) and nondetections (misses) separately. Our results revealed that hits, as compared to misses, showed a negativity around 180–350 ms at occipital and posterior temporal sites. It was followed by a positive wave after 400–500 ms, peaking at parietal sites. These correlates were not affected by a manipulation of attention. The early negativity, called ‘Visual Awareness negativity’ (VAN), may be a general, primary electrophysiological correlate of Visual Awareness. The present data show that it can be observed in response to appearance of a stimulus in Visual Awareness and that it generalizes across different manipulations of stimulus visibility.
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The role of selective attention in Visual Awareness of stimulus features: electrophysiological studies.
Cognitive Affective & Behavioral Neuroscience, 2008Co-Authors: Mika Koivisto, Antti RevonsuoAbstract:Attention and Awareness are closely related, but the nature of their relationship is unclear. The present study explores the timing and temporal evolution of their interaction with event-related potentials. The participants attended to specific conjunctions of spatial frequency and orientation in masked (unaware) and unmasked (aware) Visual stimuli. A correlate of Awareness appeared 100–200 msec from stimulus onset similarly to both attended and unattended features. Selection negativity (SN), a correlate of attentional selection, emerged in response to both masked and unmasked stimuli after 200 msec. This double dissociation between correlates of Awareness and SN suggests that the electrophysiological processes associated with feature-based attentional selection and Visual Awareness of features can be dissociated from each other at early stages of processing. In a passive task, requiring no attention to the stimuli, early electrophysiological responses (before 200 msec) related to Awareness were attenuated, suggesting that focal attention modulates Visual Awareness earlier than does selective feature-based attention.
Mika Koivisto - One of the best experts on this subject based on the ideXlab platform.
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Neural correlates of Visual Awareness at stimulus low vs. high-levels of processing.
Neuropsychologia, 2018Co-Authors: Mikel Jimenez, Simone Grassini, Pedro R. Montoro, Dolores Luna, Mika KoivistoAbstract:Abstract A crucial view in the graded vs. dichotomous debate on Visual Awareness proposes that its graded or dichotomous nature may depend on the depth of stimulus processing (or level of processing) associated to the experimental task. In the present study, we explored the behavioral patterns and neural correlates of different degrees of Awareness associated to different depths (i.e. low vs. high) of stimulus processing. The low-level stimulus condition consisted of detecting the location of the target based on its brightness characteristics, whereas the high-level stimulus condition consisted of identifying which of four possible targets (numbers/letters) had appeared. Behavioral results showed that both subjective ratings of Awareness and accuracy levels increased linearly as a function of Awareness and independently of the level of stimulus processing. Additionally, the electrophysiological recordings revealed two correlates of Visual Awareness: enhanced posterior negativity in the N200 time window (VAN, Visual Awareness negativity) and enhanced positivity in the P3 time window (LP, late positivity). Interestingly, we found evidence of Awareness levels modulating N200/VAN amplitudes in a graded manner only for the low-level task, whereas P3/LP amplitudes were modulated in a graded manner for both low and high-level tasks. The finding that the early posterior correlate of Visual Awareness (VAN at 150–250 ms) was sensitive to level of processing is consistent with task effects occurring in the Visual cortex and supports the view that it is mediated by attention to task-relevant features. The amplitudes of P3/LP in both tasks correlate more directly with graded Awareness and behavioral accuracy.
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The effects of working memory load on Visual Awareness and its electrophysiological correlates.
Neuropsychologia, 2018Co-Authors: Mika Koivisto, Maria Ruohola, Aaro Vahtera, Tuomas Lehmusvuo, Monika IntaiteAbstract:Abstract Consciousness and working memory (WM) have been thought to be closely related, but their exact relationship has remained unclear. The present study focused on the question whether Visual Awareness, the subjective experience of seeing, depends on resources of WM. Three dual-task experiments were run. The participants were asked to report their Awareness of a low-contrast target stimulus while their WM was loaded by a requirement to concurrently maintain verbal information (Experiment 1) or visuo-spatial information (Experiment 2) in WM, or by a concurrent executive task (Experiment 3). Behavioral responses and event-related brain potential (ERP) correlates of Visual Awareness in response to the targets were examined. Experiments 1 and 2 revealed that maintenance of information in WM did not have any effect on reported Visual Awareness and its electrophysiological correlates. Experiment 3 found that executive load decreased reported Visual Awareness, which was reflected in ERPs around 350–550 ms after stimulus onset as a reduction in the amplitudes of P3 to detected stimuli. The earlier, posterior correlate of Visual Awareness in N200 time window (180–280 ms) was not affected by load in any of the conditions. The results suggest that Visual consciousness and WM share resources at a relatively late stage of conscious processing, which involves active manipulation of contents. The findings are in line with a recent view suggesting that a posterior “hot zone” is responsible for Visual Awareness, while frontal regions contribute to higher-level cognitive processes that occur after Visual Awareness has arisen.
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Subjective Visual Awareness emerges prior to P3.
European Journal of Neuroscience, 2016Co-Authors: Mika Koivisto, Niina Salminen-vaparanta, Simone Grassini, Antti RevonsuoAbstract:Studies on the neural basis of Visual Awareness, the subjective experience of seeing, have found several potential neural correlates of Visual Awareness. Some of them may not directly correlate with Awareness but with post-perceptual processes, such as reporting one's Awareness of the stimulus. We dissociated potential electrophysiological correlates of Visual Awareness from those occurring during response selection and thus co-occurring with post-perceptual processing. The participants performed two GO-NOGO conditions. In the aware-GO condition they responded with a key press when they were aware of the stimulus and withheld responding when they were unaware of it. In the unaware-GO condition they withheld responding when they were aware and responded when they were not aware of the stimulus. Thus, event-related potentials could be measured to aware and unaware trials when responding was required and when not required. The results revealed that the N200 amplitude (180-280 ms) over the occipital and posterior temporal cortex was enhanced in aware trials as compared with trials without Awareness. This effect (Visual Awareness negativity, VAN) did not depend on responding. The amplitude of P3 (350-450 ms) also was enhanced in aware trials as compared with unaware trials. In addition, the amplitudes in the P3 time window depended on responding: they were greater when Awareness was mapped to GO-response than when not, suggesting that P3 reflects post-perceptual processing, that is, it occurs after Awareness has emerged. These findings support theories of Visual Awareness that assume a relatively early onset of Visual Awareness before P3.
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neural processing around 200 ms after stimulus onset correlates with subjective Visual Awareness
Neuropsychologia, 2016Co-Authors: Mika Koivisto, Simone GrassiniAbstract:Abstract Does Visual Awareness correlate with early activity in Visual cortex or with later wide-spread neural activation? This question was studied by presenting liminal targets in one of the four quadrants of the screen and asking the participants to make forced-choice localization responses and to rate their subjective Visual Awareness of each target, while electroencephalography was measured. In the analyses of event-related potential (ERP) correlates of Awareness, response accuracy was kept constant so that only the subjectively rated Awareness varied between high-Awareness (‘seen’ rating) and low-Awareness (‘unseen’ rating) targets. High-Awareness-correct trials were associated with enhanced contralateral N200 at 180–280 ms as compared with low-Awareness-correct trials. This effect (Visual Awareness negativity, VAN) also correlated with aware sensitivity to the presence vs. absence of the stimulus (d’). In addition, high-Awareness-correct trials were associated with later enhanced P3 amplitudes (after 350 ms), but this effect correlated only with the response bias (c). ERPs to low-Awareness-correct trials elicited larger contralateral N200 than ERPs to low-Awareness-incorrect trials, and this effect correlated with conservative response bias, suggesting that it reflected weak Awareness rather than unconscious processing. The results suggest that the enhanced N200 correlates with graded Awareness. The results support theories of Visual Awareness in which early activity in Visual cortex gives rise to subjective Visual experiences.
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Neuronavigated transcranial magnetic stimulation suggests that area V2 is necessary for Visual Awareness.
Neuropsychologia, 2012Co-Authors: Niina Salminen-vaparanta, Mika Koivisto, Valdas Noreika, Simo Vanni, Antti RevonsuoAbstract:Abstract The primary Visual cortex (V1) has been shown to be critical for Visual Awareness, but the importance of other low-level Visual areas has remained unclear. To clarify the role of human cortical area V2 in Visual Awareness, we applied transcranial magnetic stimulation (TMS) over V2 while participants were carrying out a Visual discrimination task and rating their subjective Awareness. Individual retinotopic maps and modelling of the TMS-induced electric field in V1, V2 and V3d ensured that the electric field was at or under the phosphene threshold level in V1 and V3d, whereas in V2 it was at the higher suppressive level. As earlier shown for the V1, our results imply that also V2 is necessary for conscious Visual experience. Visual Awareness of stimulus presence was completely suppressed when the TMS pulse was delivered 44–84 ms after the onset of Visual stimulus. Visual discrimination and Awareness of stimulus features was impaired when the TMS pulse was delivered 44–104 ms after the Visual stimulus onset. These results suggest that Visual Awareness cannot be generated without an intact V2.
Geraint Rees - One of the best experts on this subject based on the ideXlab platform.
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What does Neural Plasticity Tell us about Role of Primary Visual Cortex (V1) in Visual Awareness
Frontiers in Psychology, 2011Co-Authors: Juha Silvanto, Geraint ReesAbstract:The complete loss of Visual Awareness resulting from a lesion to the primary Visual cortex (V1) suggests that this region is indispensable for conscious Visual perception. There are however a number cases of conscious perception in the absence of V1 which appear to challenge this conclusion. These include reports of patients with bilateral V1 lesions sustained at an early age whose conscious vision has spontaneously recovered, as well as stroke patients who have recovered some conscious vision with the help of rehabilitation programs. In addition, the phenomenon of hemianopic completion and percepts induced by brain stimulation suggest that V1 may not be necessary for conscious perception in all circumstances. Furthermore, that the Visual abilities in the cat are associated with the recovery of normal extrastriate tuning properties rather than emulation of V1 functions suggests that there is nothing unique about the functional properties of this region in Visual Awareness. Rather, the dramatic effect of a V1 lesion on Visual Awareness may be due to its role in providing the majority of extrastriate Visual input, the loss of which abolishes normal neural responsiveness throughout the Visual cortex.
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Neuroimaging of Visual Awareness in patients and normal subjects.
Current Opinion in Neurobiology, 2001Co-Authors: Geraint ReesAbstract:The immediacy and directness of our Visual experience belies the complexity of the underlying neural mechanisms, which remain incompletely understood. Recent neuroimaging studies suggest that activity in ventral Visual cortex is necessary but not sufficient for Visual Awareness. Experiments in both patients and normal subjects indicate that parietal and frontal areas make an important contribution to Visual Awareness, suggesting that reciprocal interactions between dorsal frontoparietal areas and ventral Visual cortex may provide a fundamental neural substrate for conscious Visual experience.
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What can functional imaging reveal about the role of attention in Visual Awareness
Neuropsychologia, 2001Co-Authors: Geraint Rees, Nilli LavieAbstract:This review focuses on neuroimaging studies that address the relationship between selective attention, neural activity and Visual Awareness. Withdrawing attention from particular Visual stimuli reduces modality-specific processing in posterior Visual cortex, and when attention is fully engaged elsewhere, even highly salient but task-irrelevant stimuli can fail to evoke activity and reach Awareness. However, the link between Visual attention and Awareness extends beyond posterior Visual cortex to also encompass regions of parietal and prefrontal cortex. Activity in the posterior Visual cortex may be necessary but not sufficient for Awareness, without a contribution from frontal and parietal cortex. Consistent with this, enhanced interactions between parietal, frontal and posterior Visual cortex are observed as a function of both Visual attention and Visual Awareness; and lesions of parietal cortex disrupt both Visual attention and Awareness. Taken together, these data suggest that distributed interactions between modality-specific posterior Visual cortex and frontoparietal areas subserve both Visual attention and Visual Awareness.
Glyn W. Humphreys - One of the best experts on this subject based on the ideXlab platform.
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semantically induced distortions of Visual Awareness in a patient with balint s syndrome
Cognition, 2009Co-Authors: David Soto, Glyn W. HumphreysAbstract:Abstract We present data indicating that Visual Awareness for a basic perceptual feature (colour) can be influenced by the relation between the feature and the semantic properties of the stimulus. We examined semantic interference from the meaning of a colour word (‘‘RED”) on simple colour (ink related) detection responses in a patient with simultagnosia due to bilateral parietal lesions. We found that colour detection was influenced by the congruency between the meaning of the word and the relevant ink colour, with impaired performance when the word and the colour mismatched (on incongruent trials). This result held even when remote associations between meaning and colour were used (i.e. the word ‘‘PEA” influenced detection of the ink colour red). The results are consistent with a late locus of conscious Visual experience that is derived at post-semantic levels. The implications for the understanding of the role of parietal cortex in object binding and Visual Awareness are discussed.
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Semantically induced distortions of Visual Awareness in a patient with Balint’s syndrome
Cognition, 2009Co-Authors: David Soto, Glyn W. HumphreysAbstract:Abstract We present data indicating that Visual Awareness for a basic perceptual feature (colour) can be influenced by the relation between the feature and the semantic properties of the stimulus. We examined semantic interference from the meaning of a colour word (‘‘RED”) on simple colour (ink related) detection responses in a patient with simultagnosia due to bilateral parietal lesions. We found that colour detection was influenced by the congruency between the meaning of the word and the relevant ink colour, with impaired performance when the word and the colour mismatched (on incongruent trials). This result held even when remote associations between meaning and colour were used (i.e. the word ‘‘PEA” influenced detection of the ink colour red). The results are consistent with a late locus of conscious Visual experience that is derived at post-semantic levels. The implications for the understanding of the role of parietal cortex in object binding and Visual Awareness are discussed.
Michał Wierzchoń - One of the best experts on this subject based on the ideXlab platform.
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Transcranial Magnetic Stimulation-Induced Motor Cortex Activity Influences Visual Awareness Judgments.
Frontiers in Neuroscience, 2020Co-Authors: Justyna Hobot, Marcin Koculak, Borysław Paulewicz, Kristian Sandberg, Michał WierzchońAbstract:The influence of non-Visual information on Visual Awareness judgments has recently gained substantial interest. Using single-pulse transcranial magnetic stimulation (TMS), we investigate the potential contribution of evidence from the motor system to judgment of Visual Awareness. We hypothesized that TMS-induced activity in the primary motor cortex (M1) would increase reported Visual Awareness as compared to the control condition. Additionally, we investigated whether TMS-induced motor-evoked potential (MEP) could measure accumulated evidence for stimulus perception. Following stimulus presentation and TMS, participants first rated their Visual Awareness verbally using the Perceptual Awareness Scale (PAS), after which they responded manually to a Gabor orientation identification task. Delivering TMS to M1 resulted in higher average Awareness ratings as compared to the control condition, in both correct and incorrect identification task response trials, when the hand with which participants responded was contralateral to the stimulated hemisphere (TMS-response-congruent trials). This effect was accompanied by longer PAS response times (RTs), irrespective of the congruence between TMS and identification response. Moreover, longer identification RTs were observed in TMS-response-congruent trials in the M1 condition as compared to the control condition. Additionally, the amplitudes of MEPs were related to the Awareness ratings when response congruence was taken into account. We argue that MEP can serve as an indirect measure of evidence accumulated for stimulus perception and that longer PAS RTs and higher amplitudes of MEPs in the M1 condition reflect integration of additional evidence with Visual Awareness judgment. In conclusion, we advocate that motor activity influences perceptual Awareness judgments.
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Visual Awareness judgments are sensitive to accuracy feedback in stimulus discrimination tasks.
Consciousness and Cognition, 2020Co-Authors: Marta Siedlecka, Borysław Paulewicz, Michał Wereszczyński, Michał WierzchońAbstract:Abstract In this study we tested the hypothesis that perceptual Awareness judgments are sensitive to accuracy feedback about the previous action. We used a perceptual discrimination task in which participants reported their stimulus Awareness. We created two conditions: No-feedback and Feedback (discrimination accuracy feedback was provided at the end of each trial). The results showed that Visual Awareness judgments are related to the accuracy of current and previous responses. Participants reported lower stimulus Awareness for incorrectly versus correctly discriminated stimuli in both conditions; they also reported lower stimulus Awareness in trials preceded by incorrect discrimination responses, compared to trials preceded by correct discrimination responses. This difference was significantly stronger in the Feedback condition, in which we also observed post-error slowing for PAS ratings. We discuss the relation between Visual Awareness and the effects of performance monitoring and interpret the results in the context of current theories of consciousness.
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TMS-induced motor activation increases Visual Awareness
2019Co-Authors: Justyna Hobot, Marcin Koculak, Borysław Paulewicz, Kristian Sandberg, Michał WierzchońAbstract:The influence of non-perceptual information on Visual Awareness has recently gained substantial interest. Here, we investigated a potential contribution of evidence from the motor system to Visual Awareness ratings using single-pulse Transcranial Magnetic Stimulation (sp-TMS). We hypothesized that TMS-induced activation of motor cortex will increase the subjective Awareness ratings as compared to sham stimulation. Additionally, we investigated whether TMS-induced motor evoked potentials (MEPs) could be treated as a measure of evidence accumulation resulting in behavioral response. Participants performed a Visual identification task and rated their subjective experience with Perceptual Awareness Scale (PAS). During the task, we delivered sp-TMS and recorded MEPs with EMG placed on participants hand. Delivering sp-TMS to primary motor cortex resulted in higher average PAS ratings as compared to the control condition, but only in trials where stimulation was congruent with the response performed. Additionally, reaction times in the identification task were also higher in congruent trials. MEP amplitudes correlated with PAS ratings when response congruence was taken into account. We argue that activity in motor cortex influences Visual Awareness of the participants. Subsequently, MEP might serve as an indirect measure of both perceptual and non-perceptual evidence accumulated for Visual Awareness ratings. Finally, we conclude that the integration of additional information results in prolonged RTs in the identification task. Our results suggest that task-related motor activity influences Visual Awareness, extending the classical view on how Visual Awareness is shaped.
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Visual Awareness judgments are sensitive to the outcome of performance monitoring
2019Co-Authors: Marta Siedlecka, Borysław Paulewicz, Michał Wereszczyński, Michał WierzchońAbstract:Can previous mistakes influence our Visual Awareness? In this study we tested the hypothesis that perceptual Awareness judgments are sensitive to the results of performance monitoring, and specifically to internal or external accuracy feedback about previous behaviour. We used perceptual discrimination task in which participants reported their stimulus Awareness. We created two conditions: No-feedback and Feedback (discrimination accuracy feedback at the end of each trial). The results showed that Visual Awareness judgments are related to the accuracy of current and previous response. Participants reported lower stimulus Awareness for incorrectly versus correctly discriminated stimuli in both conditions, but also lower Awareness level in correct trials preceded by trials in which discrimination was incorrect, compared to trials preceded by correct discrimination. This difference was significantly stronger in Feedback condition. Moreover, in Feedback condition we observed 9post-error slowing9 for both discrimination response and PAS rating. We discuss the relation between the effects of performance monitoring and Visual Awareness and interpret the results in the context of current theories of consciousness. Keywords: Visual Awareness, PAS, performance monitoring, error detection, feedback
