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Marcantoni I, Piccolantonio G, Ghoushi M, Valenti M, Reversi L, Mariotti F, Foschi N, Lattanzi S, Burattini L, Fabri M, Polonara G. Interhemispheric functional connectivity: an fMRI study in callosotomized patients. Front Hum Neurosci 2024; 18:1363098. [PMID: 38812473 PMCID: PMC11133720 DOI: 10.3389/fnhum.2024.1363098] [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: 12/29/2023] [Accepted: 04/18/2024] [Indexed: 05/31/2024] Open
Abstract
Introduction Functional connectivity (FC) is defined in terms of temporal correlations between physiological signals, which mainly depend upon structural (axonal) connectivity; it is commonly studied using functional magnetic resonance imaging (fMRI). Interhemispheric FC appears mostly supported by the corpus callosum (CC), although several studies investigating this aspect have not provided conclusive evidence. In this context, patients in whom the CC was resected for therapeutic reasons (split-brain patients) provide a unique opportunity for research into this issue. The present study was aimed at investigating with resting-state fMRI the interhemispheric FC in six epileptic patients who have undergone surgical resection of the CC. Methods The analysis was performed using fMRI of the Brain Software Library; the evaluation of interhemispheric FC and the recognition of the resting-state networks (RSNs) were performed using probabilistic independent component analysis. Results Generally, bilateral brain activation was often observed in primary sensory RSNs, while in the associative areas, such as those composing the default mode and fronto-parietal networks, the activation was often unilateral. Discussion These results suggest that even in the absence of the CC, some interhemispheric communication is still present. This residual FC might be supported through extra-callosal pathways that are likely subcortical, making it possible for some interhemispheric integration. Further studies are needed to confirm these conclusions.
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Affiliation(s)
- Ilaria Marcantoni
- Dipartimento di Ingegneria dell'Informazione, Università Politecnica delle Marche, Ancona, Italy
| | - Giusi Piccolantonio
- Dipartimento di Ingegneria per Medicina di Innovazione, Università di Verona, Verona, Italy
| | - Mojgan Ghoushi
- Dipartimento di Scienze Radiologiche, Azienda Ospedaliera-Universitaria Umberto I, Ancona, Italy
| | - Marco Valenti
- Dipartimento di Scienze Radiologiche, Azienda Ospedaliera-Universitaria Umberto I, Ancona, Italy
| | - Luca Reversi
- Dipartimento di Scienze Radiologiche, Azienda Ospedaliera-Universitaria Umberto I, Ancona, Italy
| | - Francesco Mariotti
- Dipartimento di Scienze Radiologiche, Azienda Ospedaliera-Universitaria Umberto I, Ancona, Italy
| | - Nicoletta Foschi
- Dipartimento di Scienze Neurologiche, Azienda Ospedaliera-Universitaria Umberto I, Ancona, Italy
| | - Simona Lattanzi
- Dipartimento di Medicina Sperimentale e Clinica, Università Politecnica delle Marche, Ancona, Italy
| | - Laura Burattini
- Dipartimento di Ingegneria dell'Informazione, Università Politecnica delle Marche, Ancona, Italy
| | - Mara Fabri
- Dipartimento di Scienze della Vita e dell’Ambiente, Università Politecnica delle Marche, Ancona, Italy
| | - Gabriele Polonara
- Dipartimento di Scienze Cliniche Specialistiche e Odontostomatologiche, Università Politecnica delle Marche, Ancona, Italy
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Pinto Y, Villa MC, Siliquini S, Polonara G, Passamonti C, Lattanzi S, Foschi N, Fabri M, de Haan EHF. Visual integration across fixation: automatic processes are split but conscious processes remain unified in the split-brain. Front Hum Neurosci 2023; 17:1278025. [PMID: 38021222 PMCID: PMC10667445 DOI: 10.3389/fnhum.2023.1278025] [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: 08/15/2023] [Accepted: 09/26/2023] [Indexed: 12/01/2023] Open
Abstract
The classic view holds that when "split-brain" patients are presented with an object in the right visual field, they will correctly identify it verbally and with the right hand. However, when the object is presented in the left visual field, the patient verbally states that he saw nothing but nevertheless identifies it accurately with the left hand. This interaction suggests that perception, recognition and responding are separated in the two isolated hemispheres. However, there is now accumulating evidence that this interaction is not absolute; for instance, split-brain patients are able to detect and localise stimuli anywhere in the visual field verbally and with either hand. In this study we set out to explore this cross-hemifield interaction in more detail with the split-brain patient DDC and carried out two experiments. The aim of these experiments is to unveil the unity of deliberate and automatic processing in the context of visual integration across hemispheres. Experiment 1 suggests that automatic processing is split in this context. In contrast, when the patient is forced to adopt a conscious, deliberate, approach, processing seemed to be unified across visual fields (and thus across hemispheres). First, we looked at the confidence that DDC has in his responses. The experiment involved a simultaneous "same" versus "different" matching task with two shapes presented either within one hemifield or across fixation. The results showed that we replicated the observation that split brain patients cannot match across fixation, but more interesting, that DDC was very confident in the across-fixation condition while performing at chance-level. On the basis of this result, we hypothesised a two-route explanation. In healthy subjects, the visual information from the two hemifields is integrated in an automatic, unconscious fashion via the intact splenium, and this route has been severed in DDC. However, we know from previous experiments that some transfer of information remains possible. We proposed that this second route (perhaps less visual; more symbolic) may become apparent when he is forced to use a deliberate, consciously controlled approach. In an experiment where he is informed, by a second stimulus presented in one hemifield, what to do with the first stimulus that was presented in the same or the opposite hemifield, we showed that there was indeed interhemispheric transfer of information. We suggest that this two-route model may help in clarifying some of the controversial issues in split-brain research.
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Affiliation(s)
- Yair Pinto
- Department of Psychology, University of Amsterdam, Amsterdam, Netherlands
- Amsterdam Brain and Cognition (ABC) Center, University of Amsterdam, Amsterdam, Netherlands
| | | | - Sabrina Siliquini
- Child Neuropsychiatry Unit, Marche Polytechnic University, Ancona, Italy
| | - Gabriele Polonara
- Department of Odontostomatologic and Specialized Clinical Sciences, Marche Polytechnic University, Ancona, Italy
| | | | - Simona Lattanzi
- Department of Experimental and Clinical Medicine, Marche Polytechnic University, Ancona, Italy
| | - Nicoletta Foschi
- Epilepsy Center-Neurological Clinic, Azienda “Ospedali Riuniti”, Ancona, Italy
| | - Mara Fabri
- Department of Experimental and Clinical Medicine, Marche Polytechnic University, Ancona, Italy
| | - Edward H. F. de Haan
- Department of Psychology, University of Amsterdam, Amsterdam, Netherlands
- Amsterdam Brain and Cognition (ABC) Center, University of Amsterdam, Amsterdam, Netherlands
- Donders Institute, Radboud University, Nijmegen, Netherlands
- St. Hugh’s College, Oxford University, Oxford, United Kingdom
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Rosenblum L, Kreß A, Arikan BE, Straube B, Bremmer F. Neural correlates of visual and tactile path integration and their task related modulation. Sci Rep 2023; 13:9913. [PMID: 37337037 DOI: 10.1038/s41598-023-36797-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2022] [Accepted: 06/09/2023] [Indexed: 06/21/2023] Open
Abstract
Self-motion induces sensory signals that allow to determine travel distance (path integration). For veridical path integration, one must distinguish self-generated from externally induced sensory signals. Predictive coding has been suggested to attenuate self-induced sensory responses, while task relevance can reverse the attenuating effect of prediction. But how is self-motion processing affected by prediction and task demands, and do effects generalize across senses? In this fMRI study, we investigated visual and tactile self-motion processing and its modulation by task demands. Visual stimuli simulated forward self-motion across a ground plane. Tactile self-motion stimuli were delivered by airflow across the subjects' forehead. In one task, subjects replicated a previously observed distance (Reproduction/Active; high behavioral demand) of passive self-displacement (Reproduction/Passive). In a second task, subjects travelled a self-chosen distance (Self/Active; low behavioral demand) which was recorded and played back to them (Self/Passive). For both tasks and sensory modalities, Active as compared to Passive trials showed enhancement in early visual areas and suppression in higher order areas of the inferior parietal lobule (IPL). Contrasting high and low demanding active trials yielded supramodal enhancement in the anterior insula. Suppression in the IPL suggests this area to be a comparator of sensory self-motion signals and predictions thereof.
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Affiliation(s)
- Lisa Rosenblum
- Department Neurophysics, Philipps-Universität Marburg, Karl-Von-Frisch-Straße 8a, 35043, Marburg, Germany.
- Center for Mind, Brain and Behavior, Philipps-Universität Marburg and Justus-Liebig-Universität Giessen, Giessen, Germany.
| | - Alexander Kreß
- Department Neurophysics, Philipps-Universität Marburg, Karl-Von-Frisch-Straße 8a, 35043, Marburg, Germany
- Center for Mind, Brain and Behavior, Philipps-Universität Marburg and Justus-Liebig-Universität Giessen, Giessen, Germany
| | - B Ezgi Arikan
- Center for Mind, Brain and Behavior, Philipps-Universität Marburg and Justus-Liebig-Universität Giessen, Giessen, Germany
- Department of Psychology, Justus-Liebig-Universität Giessen, Giessen, Germany
| | - Benjamin Straube
- Center for Mind, Brain and Behavior, Philipps-Universität Marburg and Justus-Liebig-Universität Giessen, Giessen, Germany
- Translational Neuroimaging Marburg, Department of Psychiatry and Psychotherapy, Philipps-Universität Marburg, Marburg, Germany
| | - Frank Bremmer
- Department Neurophysics, Philipps-Universität Marburg, Karl-Von-Frisch-Straße 8a, 35043, Marburg, Germany
- Center for Mind, Brain and Behavior, Philipps-Universität Marburg and Justus-Liebig-Universität Giessen, Giessen, Germany
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Abstract
While the desire to uncover the neural correlates of consciousness has taken numerous directions, self-face recognition has been a constant in attempts to isolate aspects of self-awareness. The neuroimaging revolution of the 1990s brought about systematic attempts to isolate the underlying neural basis of self-face recognition. These studies, including some of the first fMRI (functional magnetic resonance imaging) examinations, revealed a right-hemisphere bias for self-face recognition in a diverse set of regions including the insula, the dorsal frontal lobe, the temporal parietal junction, and the medial temporal cortex. In this systematic review, we provide confirmation of these data (which are correlational) which were provided by TMS (transcranial magnetic stimulation) and patients in which direct inhibition or ablation of right-hemisphere regions leads to a disruption or absence of self-face recognition. These data are consistent with a number of theories including a right-hemisphere dominance for self-awareness and/or a right-hemisphere specialization for identifying significant social relationships, including to oneself.
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de Haan EHF, Scholte HS, Pinto Y, Foschi N, Polonara G, Fabri M. Singularity and consciousness: A neuropsychological contribution. J Neuropsychol 2021; 15:1-19. [PMID: 33522716 PMCID: PMC8048575 DOI: 10.1111/jnp.12234] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2020] [Revised: 10/22/2020] [Indexed: 12/03/2022]
Abstract
In common sense experience based on introspection, consciousness is singular. There is only one ‘me’ and that is the one that is conscious. This means that ‘singularity’ is a defining aspect of ‘consciousness’. However, the three main theories of consciousness, Integrated Information, Global Workspace and Recurrent Processing theory, are generally not very clear on this issue. These theories have traditionally relied heavily on neuropsychological observations and have interpreted various disorders, such as anosognosia, neglect and split‐brain as impairments in conscious awareness without any reference to ‘the singularity’. In this review, we will re‐examine the theoretical implications of these impairments in conscious awareness and propose a new way how to conceptualize consciousness of singularity. We will argue that the subjective feeling of singularity can coexist with several disunified conscious experiences. Singularity awareness may only come into existence due to environmental response constraints. That is, perceptual, language, memory, attentional and motor processes may largely proceed unintegrated in parallel, whereas a sense of unity only arises when organisms need to respond coherently constrained by the affordances of the environment. Next, we examine from this perspective psychiatric disorders and psycho‐active drugs. Finally, we present a first attempt to test this hypothesis with a resting state imaging experiment in a split‐brain patient. The results suggest that there is substantial coherence of activation across the two hemispheres. These data show that a complete lesioning of the corpus callosum does not, in general, alter the resting state networks of the brain. Thus, we propose that we have separate systems in the brain that generate distributed conscious. The sense of singularity, the experience of a ‘Me‐ness’, emerges in the interaction between the world and response‐planning systems, and this leads to coherent activation in the different functional networks across the cortex.
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Affiliation(s)
- Edward H F de Haan
- Department of Psychology, University of Amsterdam, the Netherlands.,Amsterdam Brain & Cognition (ABC) Center, University of Amsterdam, the Netherlands
| | - Huibert Steven Scholte
- Department of Psychology, University of Amsterdam, the Netherlands.,Amsterdam Brain & Cognition (ABC) Center, University of Amsterdam, the Netherlands
| | - Yair Pinto
- Department of Psychology, University of Amsterdam, the Netherlands.,Amsterdam Brain & Cognition (ABC) Center, University of Amsterdam, the Netherlands
| | - Nicoletta Foschi
- Epilepsy Center-Neurological Clinic, Azienda "Ospedali Riuniti", Ancona, Italy
| | - Gabriele Polonara
- Department of Odontostomatologic and Specialized Clinical Sciences, Marche Polytechnic University, Ancona, Italy
| | - Mara Fabri
- Department of Experimental and Clinical Medicine, Marche Polytechnic University, Ancona, Italy
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de Haan EHF, Corballis PM, Hillyard SA, Marzi CA, Seth A, Lamme VAF, Volz L, Fabri M, Schechter E, Bayne T, Corballis M, Pinto Y. Split-Brain: What We Know Now and Why This is Important for Understanding Consciousness. Neuropsychol Rev 2020; 30:224-233. [PMID: 32399946 PMCID: PMC7305066 DOI: 10.1007/s11065-020-09439-3] [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] [Received: 11/05/2019] [Accepted: 04/16/2020] [Indexed: 11/25/2022]
Abstract
Recently, the discussion regarding the consequences of cutting the corpus callosum (“split-brain”) has regained momentum (Corballis, Corballis, Berlucchi, & Marzi, Brain, 141(6), e46, 2018; Pinto et al., Brain, 140(5), 1231–1237, 2017a; Pinto, Lamme, & de Haan, Brain, 140(11), e68, 2017; Volz & Gazzaniga, Brain, 140(7), 2051–2060, 2017; Volz, Hillyard, Miller, & Gazzaniga, Brain, 141(3), e15, 2018). This collective review paper aims to summarize the empirical common ground, to delineate the different interpretations, and to identify the remaining questions. In short, callosotomy leads to a broad breakdown of functional integration ranging from perception to attention. However, the breakdown is not absolute as several processes, such as action control, seem to remain unified. Disagreement exists about the responsible mechanisms for this remaining unity. The main issue concerns the first-person perspective of a split-brain patient. Does a split-brain harbor a split consciousness or is consciousness unified? The current consensus is that the body of evidence is insufficient to answer this question, and different suggestions are made with respect to how future studies might address this paucity. In addition, it is suggested that the answers might not be a simple yes or no but that intermediate conceptualizations need to be considered.
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Affiliation(s)
- Edward H F de Haan
- Department of Psychology, University of Amsterdam, Amsterdam, the Netherlands.
| | - Paul M Corballis
- School of Psychology, University of Auckland, Auckland, New Zealand
| | - Steven A Hillyard
- School of Health Sciences, University of California Dan Diego, La Jolla, CA, USA
| | - Carlo A Marzi
- School of Medicine and Surgery, University of Verona, Verona, Italy
| | - Anil Seth
- Sackler Centre for Consciousness Science, Sussex University, Brighton, UK
| | - Victor A F Lamme
- Department of Psychology, University of Amsterdam, Amsterdam, the Netherlands
| | - Lukas Volz
- Klinik für Neurologie, Universitätsklinikum Köln, Kerpener Str, 62, Köln, Germany
| | - Mara Fabri
- Dipartimento di Medicina Sperimentale e Clinica, Via Tronto 10/A, 60020, Ancona, Italy
| | | | - Tim Bayne
- Department of Philosophy, Monash University, Melbourne, Australia
| | | | - Yair Pinto
- Department of Psychology, University of Amsterdam, Amsterdam, the Netherlands
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