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Knight RS, Chen T, Center EG, Gratton G, Fabiani M, Savazzi S, Mazzi C, Beck DM. Bypassing input to V1 in visual awareness: A TMS-EROS investigation. Neuropsychologia 2024; 198:108864. [PMID: 38521150 DOI: 10.1016/j.neuropsychologia.2024.108864] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2023] [Revised: 02/07/2024] [Accepted: 03/18/2024] [Indexed: 03/25/2024]
Abstract
Early visual cortex (V1-V3) is believed to be critical for normal visual awareness by providing the necessary feedforward input. However, it remains unclear whether visual awareness can occur without further involvement of early visual cortex, such as re-entrant feedback. It has been challenging to determine the importance of feedback activity to these areas because of the difficulties in dissociating this activity from the initial feedforward activity. Here, we applied single-pulse transcranial magnetic stimulation (TMS) over the left posterior parietal cortex to elicit phosphenes in the absence of direct visual input to early visual cortex. Immediate neural activity after the TMS pulse was assessed using the event-related optical signal (EROS), which can measure activity under the TMS coil without artifacts. Our results show that: 1) The activity in posterior parietal cortex 50 ms after TMS was related to phosphene awareness, and 2) Activity related to awareness was observed in a small portion of V1 140 ms after TMS, but in contrast (3) Activity in V2 was a more robust correlate of awareness. Together, these results are consistent with interactive models proposing that sustained and recurrent loops of activity between cortical areas are necessary for visual awareness to emerge. In addition, we observed phosphene-related activations of the anteromedial cuneus and lateral occipital cortex, suggesting a functional network subserving awareness comprising these regions, the parietal cortex and early visual cortex.
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Affiliation(s)
- Ramisha S Knight
- Beckman Institute, University of Illinois.405 N Mathews Avenue, Urbana, IL, USA; Aptima, Inc. 2555 University Blvd, Fairborn, OH, USA
| | - Tao Chen
- Beckman Institute, University of Illinois.405 N Mathews Avenue, Urbana, IL, USA; Department of Psychology, University of Illinois. 601 E John Street, Champaign, IL, USA.
| | - Evan G Center
- Beckman Institute, University of Illinois.405 N Mathews Avenue, Urbana, IL, USA; Department of Psychology, University of Illinois. 601 E John Street, Champaign, IL, USA; Center for Ubiquitous Computing, University of Oulu, Oulu, Finland
| | - Gabriele Gratton
- Beckman Institute, University of Illinois.405 N Mathews Avenue, Urbana, IL, USA; Department of Psychology, University of Illinois. 601 E John Street, Champaign, IL, USA
| | - Monica Fabiani
- Beckman Institute, University of Illinois.405 N Mathews Avenue, Urbana, IL, USA; Department of Psychology, University of Illinois. 601 E John Street, Champaign, IL, USA
| | - Silvia Savazzi
- Perception and Awareness (PandA) Lab, Department of Neuroscience, Biomedicine and Movement Sciences, University of Verona, Verona, Italy
| | - Chiara Mazzi
- Perception and Awareness (PandA) Lab, Department of Neuroscience, Biomedicine and Movement Sciences, University of Verona, Verona, Italy
| | - Diane M Beck
- Beckman Institute, University of Illinois.405 N Mathews Avenue, Urbana, IL, USA; Department of Psychology, University of Illinois. 601 E John Street, Champaign, IL, USA.
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2
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Kronemer SI, Holness M, Morgan AT, Teves JB, Gonzalez-Castillo J, Handwerker DA, Bandettini PA. Visual imagery vividness correlates with afterimage conscious perception. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.12.07.570716. [PMID: 38168380 PMCID: PMC10760211 DOI: 10.1101/2023.12.07.570716] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2024]
Abstract
Afterimages are illusory, visual conscious perceptions. A widely accepted theory is that afterimages are caused by retinal signaling that continues after the physical disappearance of a light stimulus. However, afterimages have been reported without preceding visual, sensory stimulation (e.g., conditioned afterimages and afterimages induced by illusory vision). These observations suggest the role of top-down, brain mechanisms in afterimage conscious perception. Therefore, some afterimages may share perceptual features with sensory-independent conscious perceptions (e.g., imagery, hallucinations, and dreams) that occur without bottom-up, sensory input. In the current investigation, we tested for a link between the vividness of visual imagery and afterimage conscious perception. Participants reported their vividness of visual imagery and perceived sharpness, contrast, and duration of negative afterimages. The afterimage perceptual features were acquired using perception matching paradigms that were validated on image stimuli. Relating these perceptual reports revealed that the vividness of visual imagery positively correlated with afterimage contrast and sharpness. These behavioral results support shared neural mechanisms between visual imagery and afterimages. This study encourages future research combining neurophysiology recording methods and afterimage paradigms to directly examine the neural mechanisms of afterimage conscious perception.
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Affiliation(s)
- Sharif I. Kronemer
- Section on Functional Imaging Methods, Laboratory of Brain and Cognition, National Institute of Mental Health (NIMH), National Institutes of Health (NIH), Bethesda, MD
| | - Micah Holness
- Section on Functional Imaging Methods, Laboratory of Brain and Cognition, National Institute of Mental Health (NIMH), National Institutes of Health (NIH), Bethesda, MD
| | - A. Tyler Morgan
- Section on Functional Imaging Methods, Laboratory of Brain and Cognition, National Institute of Mental Health (NIMH), National Institutes of Health (NIH), Bethesda, MD
- Functional Magnetic Resonance Imaging Core Facility, NIMH, NIH, Bethesda, MD
| | - Joshua B. Teves
- Section on Functional Imaging Methods, Laboratory of Brain and Cognition, National Institute of Mental Health (NIMH), National Institutes of Health (NIH), Bethesda, MD
| | - Javier Gonzalez-Castillo
- Section on Functional Imaging Methods, Laboratory of Brain and Cognition, National Institute of Mental Health (NIMH), National Institutes of Health (NIH), Bethesda, MD
| | - Daniel A. Handwerker
- Section on Functional Imaging Methods, Laboratory of Brain and Cognition, National Institute of Mental Health (NIMH), National Institutes of Health (NIH), Bethesda, MD
| | - Peter A. Bandettini
- Section on Functional Imaging Methods, Laboratory of Brain and Cognition, National Institute of Mental Health (NIMH), National Institutes of Health (NIH), Bethesda, MD
- Functional Magnetic Resonance Imaging Core Facility, NIMH, NIH, Bethesda, MD
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3
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Lane TJ, Liou TH, Kung YC, Tseng P, Wu CW. Functional blindsight and its diagnosis. Front Neurol 2024; 15:1207115. [PMID: 38385044 PMCID: PMC10879618 DOI: 10.3389/fneur.2024.1207115] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2023] [Accepted: 01/22/2024] [Indexed: 02/23/2024] Open
Abstract
Even when brain scans fail to detect a striate lesion, functional evidence for blindsight can be adduced. In the aftermath of an automobile accident, JK became blind. Results of ophthalmic exams indicated that the blindness must be cortical. Nevertheless, multiple MRI scans failed to detect structural damage to the striate cortex. Prior to the accident JK had been an athlete; after the accident he retained some athletic abilities, arousing suspicions that he might be engaged in fraud. His residual athletic abilities-e.g., hitting a handball or baseball, or catching a Frisbee-coupled with his experienced blindness, suggested blindsight. But due to the apparent absence of striate lesions, we designed a series of tasks for temporal and spatial dimensions in an attempt to detect functional evidence of his disability. Indeed, test results revealed compelling neural evidence that comport with his subjective reports. This spatiotemporal task-related method that includes contrasts with healthy controls, and detailed understanding of the patient's conscious experience, can be generalized for clinical, scientific and forensic investigations of blindsight.
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Affiliation(s)
- Timothy Joseph Lane
- Graduate Institute of Mind, Brain, and Consciousness, Taipei Medical University, Taipei City, Taiwan
- Brain and Consciousness Research Centre, Taipei Medical University, Taipei City, Taiwan
- Institute of European and American Studies, Academia Sinica, Taipei City, Taiwan
| | - Tsan-Hon Liou
- Graduate Institute of Mind, Brain, and Consciousness, Taipei Medical University, Taipei City, Taiwan
- Department of Physical Medicine and Rehabilitation, School of Medicine, College of Medicine, Taipei Medical University, Taipei City, Taiwan
- Department of Physical Medicine and Rehabilitation, TMU Shuang Ho Hospital, New Taipei City, Taiwan
| | - Yi-Chia Kung
- Department of Radiology, National Defense Medical Center, Tri-Service General Hospital, Taipei City, Taiwan
- Taiwan Institute of Neuroscience, National Yang Ming Chiao Tung University, Hsinchu, Taiwan
| | - Philip Tseng
- Graduate Institute of Mind, Brain, and Consciousness, Taipei Medical University, Taipei City, Taiwan
- Brain and Consciousness Research Centre, Taipei Medical University, Taipei City, Taiwan
- Department of Psychology, National Taiwan University, Taipei City, Taiwan
- Research Center for Mind, Brain and Learning, National Chengchi University, Taipei City, Taiwan
| | - Changwei W. Wu
- Graduate Institute of Mind, Brain, and Consciousness, Taipei Medical University, Taipei City, Taiwan
- Brain and Consciousness Research Centre, Taipei Medical University, Taipei City, Taiwan
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4
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Kwon S, Fahrenthold BK, Cavanaugh MR, Huxlin KR, Mitchell JF. Perceptual restoration fails to recover unconscious processing for smooth eye movements after occipital stroke. eLife 2022; 11:67573. [PMID: 35730931 PMCID: PMC9255960 DOI: 10.7554/elife.67573] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2021] [Accepted: 06/21/2022] [Indexed: 11/28/2022] Open
Abstract
The visual pathways that guide actions do not necessarily mediate conscious perception. Patients with primary visual cortex (V1) damage lose conscious perception but often retain unconscious abilities (e.g. blindsight). Here, we asked if saccade accuracy and post-saccadic following responses (PFRs) that automatically track target motion upon saccade landing are retained when conscious perception is lost. We contrasted these behaviors in the blind and intact fields of 11 chronic V1-stroke patients, and in 8 visually intact controls. Saccade accuracy was relatively normal in all cases. Stroke patients also had normal PFR in their intact fields, but no PFR in their blind fields. Thus, V1 damage did not spare the unconscious visual processing necessary for automatic, post-saccadic smooth eye movements. Importantly, visual training that recovered motion perception in the blind field did not restore the PFR, suggesting a clear dissociation between pathways mediating perceptual restoration and automatic actions in the V1-damaged visual system.
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Affiliation(s)
- Sunwoo Kwon
- Herbert Wertheim School of Optometry and Vision Science, University of California, Berkeley, Berkeley, United States
| | | | - Matthew R Cavanaugh
- Center for Visual Science, University of Rochester, Rochester, United States
| | - Krystel R Huxlin
- Department of Brain and Cognitive Sciences, University of Rochester, Rochester, United States
| | - Jude F Mitchell
- Department of Brain and Cognitive Sciences, University of Rochester, Rochester, United States
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5
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Schmid D, Schneider S, Schenk T. How to test blindsight without light-scatter artefacts? Neuropsychologia 2022; 173:108308. [PMID: 35716799 DOI: 10.1016/j.neuropsychologia.2022.108308] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2021] [Revised: 06/01/2022] [Accepted: 06/13/2022] [Indexed: 11/27/2022]
Abstract
Light-scatter artefacts are a methodological problem in testing residual visual capacities (RVCs), for instance blindsight, in patients with homonymous visual field defects (HVFDs). The term light-scatter artefact describes the phenomenon that light from targets directed towards the HVFD can stray into the sighted visual field. This might enable an observer to respond correctly to information directed at her blind field despite the fact that she is unable to process that information in the blind field itself. In this manuscript, we present a review of the relevance of light-scatter in visual neuroscience, discuss factors that influence the impact of light-scatter and evaluate means to test for light-scatter artefacts. Furthermore, we present findings from an empirical study that was aimed at developing tests for RVCs that are free of light-scatter artefacts. Previous studies on light scatter only used small sample sizes and equipment that is no longer in use. Hence, their results cannot be generalized to future experiments making it necessary to run laborious light-scatter tests for every new study on RVCs. To avoid this, we hereby start a pool of stimuli and paradigms which demonstrably do not elicit light-scatter artefacts. To this end, we investigated 21 healthy young participants in three frequently used RVC-paradigms: (1) temporal 2AFC task, (2) movement direction discrimination, and (3) redundant target paradigm. For each paradigm, we applied the blind-spot method. But first, we had to establish that our testing paradigm was sufficiently sensitive to detect light-scatter artefacts. For this, we used conditions that are known to produce strong light scatter and a paradigm that is very sensitive to such effects. Specifically, we presented white targets on a black background in a dark room. The stimuli were presented to observers' blind spot. To check for light-scatter artefacts, we used a target-detection task in a temporal 2AFC format. We obtained clear light-scatter artefacts. Participants produced reliably above-chance detection performance under these conditions. The other two luminance conditions, measured in an illuminated room, did not produce light-scatter artefacts. Accuracy in the temporal 2AFC task was at chance level for white targets on a grey background at the blind-spot position. Additionally, black targets on a grey background avoided light-scatter artefacts in all three RVC-paradigms. In future, researchers can apply these stimulus and illumination conditions when using one of the three above paradigms in their studies. Using these conditions, they will be able to avoid light-scatter artefacts without having to perform their own blind-spot tests.
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Affiliation(s)
- Doris Schmid
- Department of Psychology, Ludwig-Maximilians-Universität München, Leopoldstr. 13, 80802, Munich, Germany.
| | - Sebastian Schneider
- Department of Psychology, Ludwig-Maximilians-Universität München, Leopoldstr. 13, 80802, Munich, Germany.
| | - Thomas Schenk
- Department of Psychology, Ludwig-Maximilians-Universität München, Leopoldstr. 13, 80802, Munich, Germany.
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6
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Derrien D, Garric C, Sergent C, Chokron S. The nature of blindsight: implications for current theories of consciousness. Neurosci Conscious 2022; 2022:niab043. [PMID: 35237447 PMCID: PMC8884361 DOI: 10.1093/nc/niab043] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2021] [Revised: 11/08/2021] [Accepted: 01/13/2022] [Indexed: 11/16/2022] Open
Abstract
Blindsight regroups the different manifestations of preserved discriminatory visual capacities following the damage to the primary visual cortex. Blindsight types differentially impact objective and subjective perception, patients can report having no visual awareness whilst their behaviour suggests visual processing still occurs at some cortical level. This phenomenon hence presents a unique opportunity to study consciousness and perceptual consciousness, and for this reason, it has had an historical importance for the development of this field of research. From these studies, two main opposing models of the underlying mechanisms have been established: (a) blindsight is perception without consciousness or (b) blindsight is in fact degraded vision, two views that mirror more general theoretical options about whether unconscious cognition truly exists or whether it is only a degraded form of conscious processing. In this article, we want to re-examine this debate in the light of recent advances in the characterization of blindsight and associated phenomena. We first provide an in-depth definition of blindsight and its subtypes, mainly blindsight type I, blindsight type II and the more recently described blindsense. We emphasize the necessity of sensitive and robust methodology to uncover the dissociations between perception and awareness that can be observed in brain-damaged patients with visual field defects at different cognitive levels. We discuss these different profiles of dissociation in the light of both contending models. We propose that the different types of dissociations reveal a pattern of relationship between perception, awareness and metacognition that is actually richer than what is proposed by either of the existing models. Finally, we consider this in the framework of current theories of consciousness and touch on the implications the findings of blindsight have on these.
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Affiliation(s)
- Diane Derrien
- Integrative Neuroscience and Cognition Center, UMR 8002, CNRS & Université de Paris, Paris 75006, France
- Institut de Neuropsychologie, Neurovision, NeuroCognition, Fondation Ophtalmologique Rothschild, Paris 75019, France
| | - Clémentine Garric
- Inserm, CHU Lille, U1172—LilNCog (JPARC)—Lille Neuroscience & Cognition, University of Lille, Lille 59000, France
| | - Claire Sergent
- Integrative Neuroscience and Cognition Center, UMR 8002, CNRS & Université de Paris, Paris 75006, France
| | - Sylvie Chokron
- Integrative Neuroscience and Cognition Center, UMR 8002, CNRS & Université de Paris, Paris 75006, France
- Institut de Neuropsychologie, Neurovision, NeuroCognition, Fondation Ophtalmologique Rothschild, Paris 75019, France
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7
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Ding J, Ye Z, Xu F, Hu X, Yu H, Zhang S, Tu Y, Zhang Q, Sun Q, Hua T, Lu ZL. Effects of top-down influence suppression on behavioral and V1 neuronal contrast sensitivity functions in cats. iScience 2022; 25:103683. [PMID: 35059603 PMCID: PMC8760559 DOI: 10.1016/j.isci.2021.103683] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2021] [Revised: 11/16/2021] [Accepted: 12/20/2021] [Indexed: 02/09/2023] Open
Abstract
To explore the relative contributions of higher-order and primary visual cortex (V1) to visual perception, we compared cats' behavioral and V1 neuronal contrast sensitivity functions (CSF) and threshold versus external noise contrast (TvC) functions before and after top-down influence of area 7 (A7) was modulated with transcranial direct current stimulation (tDCS). We found that suppressing top-down influence of A7 with cathode-tDCS, but not sham-tDCS, reduced behavioral and neuronal contrast sensitivity in the same range of spatial frequencies and increased behavioral and neuronal contrast thresholds in the same range of external noise levels. The neuronal CSF and TvC functions were highly correlated with their behavioral counterparts both before and after the top-down suppression. Analysis of TvC functions using the Perceptual Template Model (PTM) indicated that top-down influence of A7 increased both behavioral and V1 neuronal contrast sensitivity by reducing internal additive noise and the impact of external noise. Top-down suppression lowers both behavioral and V1 neuronal CSF functions Top-down suppression raises both behavioral and V1 neuronal TvC functions The neuronal CSFs and TvCs are highly correlated with their behavioral counterparts Top-down influence lowers internal additive noise and impact of external noise in V1
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Affiliation(s)
- Jian Ding
- College of Life Sciences, Anhui Normal University, Wuhu, Anhui 241000, China
| | - Zheng Ye
- College of Life Sciences, Anhui Normal University, Wuhu, Anhui 241000, China
| | - Fei Xu
- College of Life Sciences, Anhui Normal University, Wuhu, Anhui 241000, China
| | - Xiangmei Hu
- College of Life Sciences, Anhui Normal University, Wuhu, Anhui 241000, China
| | - Hao Yu
- College of Life Sciences, Anhui Normal University, Wuhu, Anhui 241000, China
| | - Shen Zhang
- College of Life Sciences, Anhui Normal University, Wuhu, Anhui 241000, China
| | - Yanni Tu
- College of Life Sciences, Anhui Normal University, Wuhu, Anhui 241000, China
| | - Qiuyu Zhang
- College of Life Sciences, Anhui Normal University, Wuhu, Anhui 241000, China
| | - Qingyan Sun
- College of Life Sciences, Anhui Normal University, Wuhu, Anhui 241000, China
| | - Tianmiao Hua
- College of Life Sciences, Anhui Normal University, Wuhu, Anhui 241000, China
| | - Zhong-Lin Lu
- Divison of Arts and Sciences, NYU Shanghai, Shanghai 200122, China.,Center for Neural Science and Department of Psychology, New York University, New York, NY 10003, USA.,NYU-ECNU Institute of Brain and Cognitive Science, NYU Shanghai, Shanghai 200062, China
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8
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Spared perilesional V1 activity underlies training-induced recovery of luminance detection sensitivity in cortically-blind patients. Nat Commun 2021; 12:6102. [PMID: 34671032 PMCID: PMC8528839 DOI: 10.1038/s41467-021-26345-1] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2020] [Accepted: 09/29/2021] [Indexed: 11/19/2022] Open
Abstract
Damage to the primary visual cortex (V1) causes homonymous visual-field loss long considered intractable. Multiple studies now show that perceptual training can restore visual functions in chronic cortically-induced blindness (CB). A popular hypothesis is that training can harness residual visual functions by recruiting intact extrageniculostriate pathways. Training may also induce plastic changes within spared regions of the damaged V1. Here, we link changes in luminance detection sensitivity with retinotopic fMRI activity before and after visual discrimination training in eleven patients with chronic, stroke-induced CB. We show that spared V1 activity representing perimetrically-blind locations prior to training predicts the amount of training-induced recovery of luminance detection sensitivity. Additionally, training results in an enlargement of population receptive fields in perilesional V1, which increases blind-field coverage and may support further recovery with subsequent training. These findings uncover fundamental changes in perilesional V1 cortex underlying training-induced restoration of conscious luminance detection sensitivity in CB. In humans, stroke damage to V1 causes large visual field defects. Spared V1 activity prior to training predicts the amount of training-induced recovery in luminance detection sensitivity. Moreover, visual training changes population receptive field properties within residual V1 circuits.
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9
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Is the primary visual cortex necessary for blindsight-like behavior? Review of transcranial magnetic stimulation studies in neurologically healthy individuals. Neurosci Biobehav Rev 2021; 127:353-364. [PMID: 33965459 DOI: 10.1016/j.neubiorev.2021.04.038] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2020] [Revised: 04/28/2021] [Accepted: 04/29/2021] [Indexed: 12/20/2022]
Abstract
The visual pathways that bypass the primary visual cortex (V1) are often assumed to support visually guided behavior in humans in the absence of conscious vision. This conclusion is largely based on findings on patients: V1 lesions cause blindness but sometimes leave some visually guided behaviors intact-this is known as blindsight. With the aim of examining how well the findings on blindsight patients generalize to neurologically healthy individuals, we review studies which have tried to uncover transcranial magnetic stimulation (TMS) induced blindsight. In general, these studies have failed to demonstrate a completely unconscious blindsight-like capacity in neurologically healthy individuals. A possible exception to this is TMS-induced blindsight of stimulus presence or location. Because blindsight in patients is often associated with some form of introspective access to the visual stimulus, and blindsight may be associated with neural reorganization, we suggest that rather than revealing a dissociation between visually guided behavior and conscious seeing, blindsight may reflect preservation or partial recovery of conscious visual perception after the lesion.
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10
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Key B, Zalucki O, Brown DJ. Neural Design Principles for Subjective Experience: Implications for Insects. Front Behav Neurosci 2021; 15:658037. [PMID: 34025371 PMCID: PMC8131515 DOI: 10.3389/fnbeh.2021.658037] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2021] [Accepted: 04/07/2021] [Indexed: 02/04/2023] Open
Abstract
How subjective experience is realized in nervous systems remains one of the great challenges in the natural sciences. An answer to this question should resolve debate about which animals are capable of subjective experience. We contend that subjective experience of sensory stimuli is dependent on the brain's awareness of its internal neural processing of these stimuli. This premise is supported by empirical evidence demonstrating that disruption to either processing streams or awareness states perturb subjective experience. Given that the brain must predict the nature of sensory stimuli, we reason that conscious awareness is itself dependent on predictions generated by hierarchically organized forward models of the organism's internal sensory processing. The operation of these forward models requires a specialized neural architecture and hence any nervous system lacking this architecture is unable to subjectively experience sensory stimuli. This approach removes difficulties associated with extrapolations from behavioral and brain homologies typically employed in addressing whether an animal can feel. Using nociception as a model sensation, we show here that the Drosophila brain lacks the required internal neural connectivity to implement the computations required of hierarchical forward models. Consequently, we conclude that Drosophila, and those insects with similar neuroanatomy, do not subjectively experience noxious stimuli and therefore cannot feel pain.
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Affiliation(s)
- Brian Key
- School of Biomedical Sciences, The University of Queensland, Brisbane, QLD, Australia
| | - Oressia Zalucki
- School of Biomedical Sciences, The University of Queensland, Brisbane, QLD, Australia
| | - Deborah J. Brown
- School of Historical and Philosophical Inquiry, The University of Queensland, Brisbane, QLD, Australia
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11
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Sanchez-Lopez J, Cardobi N, Pedersini CA, Savazzi S, Marzi CA. What cortical areas are responsible for blindsight in hemianopic patients? Cortex 2020; 132:113-134. [PMID: 32977179 DOI: 10.1016/j.cortex.2020.08.007] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2020] [Revised: 06/07/2020] [Accepted: 08/07/2020] [Indexed: 12/25/2022]
Abstract
The presence of above-chance unconscious behavioral responses following stimulus presentation to the blind hemifield of hemianopic patients (blindsight) is a well-known phenomenon. What is still lacking is a systematic study of the neuroanatomical bases of two distinct aspects of blindsight: the unconscious above chance performance and the phenomenological aspects that may be associated. Here, we tested 17 hemianopic patients in two tasks i.e. movement and orientation discrimination of a visual grating presented to the sighted or blind hemifield. We classified patients in four groups on the basis of the presence of above chance unconscious discrimination without or with perceptual awareness reports for stimulus presentation to the blind hemifield. A fifth group was represented by patients with interruption of the Optic Radiation. In the various groups we carried out analyses of lesion extent of various cortical areas, probabilistic tractography as well as assessment of the cortical thickness of the intact hemisphere. All patients had lesions mainly, but not only, in the occipital lobe and the statistical comparison of their extent provided clues as to the critical anatomical substrate of unconscious above-chance performance and of perceptual awareness reports, respectively. In fact, the two areas that turned out to be critical for above-chance performance in the discrimination of moving versus non-moving visual stimuli were the Precuneus and the Posterior Cingulate Gyrus while for perceptual awareness reports the crucial areas were Intracalcarine, Supracalcarine, Cuneus, and the Posterior Cingulate Gyrus. Interestingly, the proportion of perceptual awareness reports was higher in patients with a spared right hemisphere. As to probabilistic tractography, all pathways examined yielded higher positive values for patients with perceptual awareness reports. Finally, the cortical thickness of the intact hemisphere was greater in patients showing above-chance performance than in those at chance. This effect is likely to be a result of neuroplastic compensatory mechanisms.
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Affiliation(s)
- Javier Sanchez-Lopez
- Physiology and Psychology Section, Department of Neuroscience, Biomedicine and Movement Sciences, University of Verona, Verona, Italy.
| | - Nicolò Cardobi
- Physiology and Psychology Section, Department of Neuroscience, Biomedicine and Movement Sciences, University of Verona, Verona, Italy.
| | - Caterina A Pedersini
- Physiology and Psychology Section, Department of Neuroscience, Biomedicine and Movement Sciences, University of Verona, Verona, Italy.
| | - Silvia Savazzi
- Physiology and Psychology Section, Department of Neuroscience, Biomedicine and Movement Sciences, University of Verona, Verona, Italy; Perception and Awareness (PandA) Laboratory, University of Verona, Verona, Italy; National Institute of Neuroscience, Verona, Italy.
| | - Carlo A Marzi
- Physiology and Psychology Section, Department of Neuroscience, Biomedicine and Movement Sciences, University of Verona, Verona, Italy; National Institute of Neuroscience, Verona, Italy.
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12
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Chokron S, Dubourg L, Garric C, Martinelli F, Perez C. Dissociations between perception and awareness in hemianopia. Restor Neurol Neurosci 2020; 38:189-201. [PMID: 31929128 DOI: 10.3233/rnn-190951] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The most common visual defect to follow a lesion of the retrochiasmal pathways is homonymous hemianopia (HH), whereby patients are blind to the contralesional visual field of each eye. Homonymous hemianopia has been studied in terms of its deleterious consequences on perceptual, cognitive and motor tasks as well as because it represents an interesting model of vision loss after a unilateral lesion of the occipital lobe. From a behavioral perspective, in addition to exhibiting a severe deficit in their contralesional visual field, HH patients can also exhibit dissociations between perception and awareness. Firstly, HH patients suffering from anosognosia may be unaware of their visual field defect. Secondly, HH patients can present with unconscious visual abilities in the blind hemifield, a phenomenon referred to as blindsight. Thirdly, recent reports demonstrate that HH patients can suffer from a subtle deficit in their ipsilesional visual field that they are unaware of, a condition called sightblindness (i.e. the reverse case of 'blindsight'). Finally, HH patients may also exhibit visual hallucinations in their blind field; however, such patients are not systematically aware that their perceptions are unreal. In this review, we provide an overview of the visual-field losses in HH patients after a left or right unilateral occipital lesion. Furthermore, we explore the implications of these four phenomena for models of visual processing and rehabilitation of visual field defects in HH patients. Finally, in contrast to the traditional view that HH is solely a visual-field defect, we discuss why this deficit is an interesting model for studying the dissociation between perception and awareness.
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Affiliation(s)
- Sylvie Chokron
- Integrative Neuroscience and Cognition Center, CNRS, UMR 8242 et Université Paris-Descartes, Paris, France
| | - Lucas Dubourg
- Institut de Neuropsychologie, Neurovision, NeuroCognition, Fondation Ophtalmologique Adolphe de Rothschild, Paris, France.,Integrative Neuroscience and Cognition Center, CNRS, UMR 8242 et Université Paris-Descartes, Paris, France
| | - Clémentine Garric
- Laboratoire de Sciences Cognitives et Affectives, SCALab, CNRS UMR, Faculté de Médecine, Pôle Recherche et Université de Lille, Lille, France
| | - Fiora Martinelli
- Integrative Neuroscience and Cognition Center, CNRS, UMR 8242 et Université Paris-Descartes, Paris, France
| | - Céline Perez
- Institut de Neuropsychologie, Neurovision, NeuroCognition, Fondation Ophtalmologique Adolphe de Rothschild, Paris, France.,Integrative Neuroscience and Cognition Center, CNRS, UMR 8242 et Université Paris-Descartes, Paris, France
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Mazzi C, Tagliabue CF, Mazzeo G, Savazzi S. Reliability in reporting perceptual experience: Behaviour and electrophysiology in hemianopic patients. Neuropsychologia 2019; 128:119-126. [PMID: 29355647 PMCID: PMC6562273 DOI: 10.1016/j.neuropsychologia.2018.01.017] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2017] [Revised: 01/07/2018] [Accepted: 01/15/2018] [Indexed: 12/02/2022]
Abstract
Patients with hemianopia can present with the so called blindsight phenomenon: the ability to perform above chance in the absence of acknowledged awareness. Proper awareness reports are, thus, crucial to distinguish pure forms of blindsight from forms of conscious, yet degraded, vision. It has, in fact, been recently shown that 1) dichotomous and graded measures to assess awareness can lead to different behavioural results in patients with hemianopia and that 2) different grades of perceptual clarity show different electrophysiological correlates in healthy participants. Here, in hemianopic patients, we assessed awareness by means of the four-point Perceptual Awareness Scale (PAS) and investigated its neural correlates with Event Related Potentials (ERPs). Results showed that patients, in most of the cases, can rate the clarity of their perceptual experience in a graded manner. Moreover, graded perceptual experiences correlated with the amplitude of deflections in ERPs. These results call for the need to assess perceptual awareness with graded measures and for the importance to use electrophysiological data to correlate behaviour with neural processing.
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Affiliation(s)
- Chiara Mazzi
- Perception and Awareness (PandA) Laboratory, Department of Neuroscience, Biomedicine and Movement Sciences, University of Verona, Verona, Italy; National Institute of Neuroscience, Verona, Italy
| | - Chiara Francesca Tagliabue
- Perception and Awareness (PandA) Laboratory, Department of Neuroscience, Biomedicine and Movement Sciences, University of Verona, Verona, Italy; National Institute of Neuroscience, Verona, Italy
| | - Gaetano Mazzeo
- Perception and Awareness (PandA) Laboratory, Department of Neuroscience, Biomedicine and Movement Sciences, University of Verona, Verona, Italy; National Institute of Neuroscience, Verona, Italy
| | - Silvia Savazzi
- Perception and Awareness (PandA) Laboratory, Department of Neuroscience, Biomedicine and Movement Sciences, University of Verona, Verona, Italy; National Institute of Neuroscience, Verona, Italy.
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Mazzi C, Savazzi S. The Glamor of Old-Style Single-Case Studies in the Neuroimaging Era: Insights From a Patient With Hemianopia. Front Psychol 2019; 10:965. [PMID: 31114532 PMCID: PMC6502964 DOI: 10.3389/fpsyg.2019.00965] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2018] [Accepted: 04/11/2019] [Indexed: 11/23/2022] Open
Affiliation(s)
- Chiara Mazzi
- Perception and Awareness (PandA) Lab, Department of Neuroscience, Biomedicine and Movement Sciences, University of Verona, Verona, Italy.,National Institute of Neuroscience, Verona, Italy
| | - Silvia Savazzi
- Perception and Awareness (PandA) Lab, Department of Neuroscience, Biomedicine and Movement Sciences, University of Verona, Verona, Italy.,National Institute of Neuroscience, Verona, Italy
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15
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Sabel BA, Flammer J, Merabet LB. Residual vision activation and the brain-eye-vascular triad: Dysregulation, plasticity and restoration in low vision and blindness - a review. Restor Neurol Neurosci 2019; 36:767-791. [PMID: 30412515 PMCID: PMC6294586 DOI: 10.3233/rnn-180880] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Vision loss due to ocular diseases such as glaucoma, optic neuropathy, macular degeneration, or diabetic retinopathy, are generally considered an exclusive affair of the retina and/or optic nerve. However, the brain, through multiple indirect influences, has also a major impact on functional visual impairment. Such indirect influences include intracerebral pressure, eye movements, top-down modulation (attention, cognition), and emotionally triggered stress hormone release affecting blood vessel dysregulation. Therefore, vision loss should be viewed as the result of multiple interactions within a “brain-eye-vascular triad”, and several eye diseases may also be considered as brain diseases in disguise. While the brain is part of the problem, it can also be part of the solution. Neuronal networks of the brain can “amplify” residual vision through neuroplasticity changes of local and global functional connectivity by activating, modulating and strengthening residual visual signals. The activation of residual vision can be achieved by different means such as vision restoration training, non-invasive brain stimulation, or blood flow enhancing medications. Modulating brain functional networks and improving vascular regulation may offer new opportunities to recover or restore low vision by increasing visual field size, visual acuity and overall functional vision. Hence, neuroscience offers new insights to better understand vision loss, and modulating brain and vascular function is a promising source for new opportunities to activate residual vision to achieve restoration and recovery to improve quality of live in patients suffering from low vision.
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Affiliation(s)
- Bernhard A Sabel
- Institute of Medical Psychology, Medical Faculty, Otto-von-Guericke University of Magdeburg, Magdeburg, Germany
| | - Josef Flammer
- Department of Ophthalmology, University of Basel, Basel, Switzerland
| | - Lotfi B Merabet
- Department of Ophthalmology, The Laboratory for Visual Neuroplasticity, Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, USA
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Grasso PA, Làdavas E, Bertini C, Caltabiano S, Thut G, Morand S. Decoupling of Early V5 Motion Processing from Visual Awareness: A Matter of Velocity as Revealed by Transcranial Magnetic Stimulation. J Cogn Neurosci 2018; 30:1517-1531. [DOI: 10.1162/jocn_a_01298] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
Motion information can reach V5/MT through two parallel routes: one conveying information at early latencies through a direct subcortical route and the other reaching V5 later via recurrent projections through V1. Here, we tested the hypothesis that input via the faster direct pathway depends on motion characteristics. To this end, we presented motion stimuli to healthy human observers at different velocities (4.4°/sec vs. 23°/sec) with static stimuli as controls while applying transcranial magnetic stimulation (TMS) pulses over V5 or V1. We probed for TMS interference with objective (two-alternative forced choice [2AFC]) and subjective (awareness) measures of motion processing at six TMS delays from stimulus onset (poststimulus window covered: ∼27–160 msec). Our results for V5–TMS showed earlier interference with objective performance for fast motion (53.3 msec) than slow motion (80 msec) stimuli. Importantly, TMS-induced decreases in objective measures of motion processing did correlate with decreases in subjective measures for slow but not fast motion stimuli. Moreover, V1–TMS induced a temporally unspecific interference with visual processing as it impaired the processing of both motion and static stimuli at the same delays. These results are in accordance with fast moving stimuli reaching V5 through a different route than slow moving stimuli. The differential latencies and coupling to awareness suggest distinct involvement of a direct (i.e., colliculo-extrastriate) connection bypassing V1 depending on stimulus velocity (fast vs. slow). Implication of a direct pathway in the early processing of fast motion may have evolved through its behavioral relevance.
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Cavanaugh MR, Barbot A, Carrasco M, Huxlin KR. Feature-based attention potentiates recovery of fine direction discrimination in cortically blind patients. Neuropsychologia 2017; 128:315-324. [PMID: 29237554 DOI: 10.1016/j.neuropsychologia.2017.12.010] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2017] [Revised: 12/02/2017] [Accepted: 12/04/2017] [Indexed: 01/23/2023]
Abstract
Training chronic, cortically-blind (CB) patients on a coarse [left-right] direction discrimination and integration (CDDI) task recovers performance on this task at trained, blind field locations. However, fine direction difference (FDD) thresholds remain elevated at these locations, limiting the usefulness of recovered vision in daily life. Here, we asked if this FDD impairment can be overcome by training CB subjects with endogenous, feature-based attention (FBA) cues. Ten CB subjects were recruited and trained on CDDI and FDD with an FBA cue or FDD with a neutral cue. After completion of each training protocol, FDD thresholds were re-measured with both neutral and FBA cues at trained, blind-field locations and at corresponding, intact-field locations. In intact portions of the visual field, FDD thresholds were lower when tested with FBA than neutral cues. Training subjects in the blind field on the CDDI task improved FDD performance to the point that a threshold could be measured, but these locations remained impaired relative to the intact field. FDD training with neutral cues resulted in better blind field FDD thresholds than CDDI training, but thresholds remained impaired relative to intact field levels, regardless of testing cue condition. Importantly, training FDD in the blind field with FBA lowered FDD thresholds relative to CDDI training, and allowed the blind field to reach thresholds similar to the intact field, even when FBA trained subjects were tested with a neutral rather than FBA cue. Finally, FDD training appeared to also recover normal integration thresholds at trained, blind-field locations, providing an interesting double dissociation with respect to CDDI training. In summary, mechanisms governing FBA appear to function normally in both intact and impaired regions of the visual field following V1 damage. Our results mark the first time that FDD thresholds in CB fields have been seen to reach intact field levels of performance. Moreover, FBA can be leveraged during visual training to recover normal, fine direction discrimination and integration performance at trained, blind-field locations, potentiating visual recovery of more complex and precise aspects of motion perception in cortically-blinded fields.
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Affiliation(s)
- Matthew R Cavanaugh
- Flaum Eye Institute and Center for Visual Science, University of Rochester, Rochester, NY 14642, USA; Neuroscience Graduate Program, University of Rochester Medical Center, Rochester, NY 14642, USA
| | - Antoine Barbot
- Flaum Eye Institute and Center for Visual Science, University of Rochester, Rochester, NY 14642, USA
| | - Marisa Carrasco
- Department of Psychology and Center for Neural Science, New York University, New York, NY 10003, USA
| | - Krystel R Huxlin
- Flaum Eye Institute and Center for Visual Science, University of Rochester, Rochester, NY 14642, USA
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