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Kiefer M, Kammer T. The Relation Between Subjective and Objective Measures of Visual Awareness: Current Evidence, Attempt of a Synthesis and Future Research Directions. J Cogn 2024; 7:59. [PMID: 39035071 PMCID: PMC11259121 DOI: 10.5334/joc.381] [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: 03/28/2024] [Accepted: 06/23/2024] [Indexed: 07/23/2024] Open
Abstract
Within the realm of consciousness research, different methods of measuring the content of visual awareness are used: On the one hand, subjective measures require a report of sensory experiences related to a stimulus. On the other hand, objective measures rely on the observer's performance to accurately detect or discriminate the stimulus. The most appropriate measure of awareness is currently debated. To contribute to this debate, we review findings on the relation between subjective and objective measures of awareness. Although subjective measures sometimes lag behind objective measures, a substantial number of studies demonstrates a convergence of measures. Based on the reviewed studies, we identify five aspects relevant for achieving a convergence of measures. Future research could then identify and empirically test the boundary conditions, under which a convergence or divergence of subjective and measures of awareness is observed.
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Bertamini M, Oletto CM, Contemori G. The Role of Uniform Textures in Making Texture Elements Visible in the Visual Periphery. Open Mind (Camb) 2024; 8:462-482. [PMID: 38665546 PMCID: PMC11045036 DOI: 10.1162/opmi_a_00136] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2023] [Accepted: 02/25/2024] [Indexed: 04/28/2024] Open
Abstract
There are important differences between central and peripheral vision. With respect to shape, contours retain phenomenal sharpness, although some contours disappear if they are near other contours. This leads to some uniform textures to appear non-uniform (Honeycomb illusion, Bertamini et al., 2016). Unlike other phenomena of shape perception in the periphery, this illusion is showing how continuity of the texture does not contribute to phenomenal continuity. We systematically varied the relationship between central and peripheral regions, and we collected subjective reports (how far can one see lines) as well as judgments of line orientation. We used extended textures created with a square grid and some additional lines that are invisible when they are located at the corners of the grid, or visible when they are separated from the grid (control condition). With respects to subjective reports, we compared the region of visibility for cases in which the texture was uniform (Exp 1a), or when in a central region the lines were different (Exp 1b). There were no differences, showing no role of objective uniformity on visibility. Next, in addition to the region of visibility we measured sensitivity using a forced-choice task (line tilted left or right) (Exp 2). The drop in sensitivity with eccentricity matched the size of the region in which lines were perceived in the illusion condition, but not in the control condition. When participants were offered a choice to report of the lines were present or absent (Exp 3) they confirmed that they did not see them in the illusion condition, but saw them in the control condition. We conclude that mechanisms that control perception of contours operate differently in the periphery, and override prior expectations, including that of uniformity. Conversely, when elements are detected in the periphery, we assign to them properties based on information from central vision, but these shapes cannot be identified correctly when the task requires such discrimination.
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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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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: 3] [Impact Index Per Article: 1.5] [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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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: 8] [Impact Index Per Article: 2.0] [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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Garric C, Caetta F, Sergent C, Chokron S. Making sense of blindsense: a reply to Phillips. Cortex 2020; 127:393-395. [DOI: 10.1016/j.cortex.2020.03.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2020] [Accepted: 03/12/2020] [Indexed: 10/24/2022]
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Phillips I. Making sense of blindsense: A commentary on Garric et al., 2019. Cortex 2020; 127:388-392. [PMID: 31898946 DOI: 10.1016/j.cortex.2019.11.016] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2019] [Accepted: 11/28/2019] [Indexed: 10/25/2022]
Affiliation(s)
- Ian Phillips
- Department of Philosophy, and Department of Psychological and Brain Sciences, Johns Hopkins University, Baltimore, MD, USA.
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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: 2] [Impact Index Per Article: 0.5] [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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