1
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Fakhar K, Hilgetag CC. Systematic perturbation of an artificial neural network: A step towards quantifying causal contributions in the brain. PLoS Comput Biol 2022; 18:e1010250. [PMID: 35714139 PMCID: PMC9246164 DOI: 10.1371/journal.pcbi.1010250] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2021] [Revised: 06/30/2022] [Accepted: 05/25/2022] [Indexed: 11/24/2022] Open
Abstract
Lesion inference analysis is a fundamental approach for characterizing the causal contributions of neural elements to brain function. This approach has gained new prominence through the arrival of modern perturbation techniques with unprecedented levels of spatiotemporal precision. While inferences drawn from brain perturbations are conceptually powerful, they face methodological difficulties. Particularly, they are challenged to disentangle the true causal contributions of the involved elements, since often functions arise from coalitions of distributed, interacting elements, and localized perturbations have unknown global consequences. To elucidate these limitations, we systematically and exhaustively lesioned a small artificial neural network (ANN) playing a classic arcade game. We determined the functional contributions of all nodes and links, contrasting results from sequential single-element perturbations with simultaneous perturbations of multiple elements. We found that lesioning individual elements, one at a time, produced biased results. By contrast, multi-site lesion analysis captured crucial details that were missed by single-site lesions. We conclude that even small and seemingly simple ANNs show surprising complexity that needs to be addressed by multi-lesioning for a coherent causal characterization. The motto “No causation without manipulation” is canonical to scientific endeavors. In particular, neuroscience seeks to identify which brain elements are causally involved in cognition and behavior, by perturbing them. However, due to multi-dimensional interactions among the elements, this goal has remained challenging. Here, we used an Artificial Neural Network as a ground-truth model to compare the inferential capacities of two principal approaches, lesioning a system one element at a time versus sampling from the set of all possible combinations of lesions. We show that lesioning one element at a time provides misleading results. Hence, we argue for employing exhaustive perturbation regimes. We further advocate using simulation experiments and ground-truth models to verify the assumptions and limitations of current approaches for brain mapping by perturbation.
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Affiliation(s)
- Kayson Fakhar
- Institute of Computational Neuroscience, University Medical Center Eppendorf, Hamburg University, Hamburg, Germany
- * E-mail:
| | - Claus C. Hilgetag
- Institute of Computational Neuroscience, University Medical Center Eppendorf, Hamburg University, Hamburg, Germany
- Department of Health Sciences, Boston University, Boston, Massachusetts, United States of America
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2
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Zhang Q, Zhang L, He W, Zheng X, Zhao Z, Li Y, Xu S, Zheng J, Zhuang X, Jia W, Zhu C, Xu H, Shan C, Chen W, Zhao J, Chen S. Case Report: Visual Deprivation in Pusher Syndrome Complicated by Hemispatial Neglect After Basal Ganglia Stroke. Front Neurol 2021; 12:706611. [PMID: 34630282 PMCID: PMC8494178 DOI: 10.3389/fneur.2021.706611] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2021] [Accepted: 08/05/2021] [Indexed: 12/03/2022] Open
Abstract
We aimed to explore whether motor function and activities of daily life (ADL) could be improved with the application of visual deprivation in two patients with Pusher syndrome complicated by hemispatial neglect after right basal ganglia stroke. We assessed two stroke patients suffering from severe motor disturbances, both tilting heavily to the left, with diagnoses of Pusher syndrome and left hemispatial neglect. Vision in the left eye was deprived using patches during clinical rehabilitation. Motor function promotion was confirmed using the Burke Lateropulsion Scale (BLS), Fugl–Meyer Balance Scale (FMBS), and Holden grade (HG), while the Barthel index (BI) assessed ADL immediately and 1 week after intervention. Both patients regained standing balance immediately using visual deprivation, as well as walking ability, although both scored 0 on the FMBS and HG. After 1 week of treatment, one patient increased to 11 and 3 on the FMBS and HG, respectively, while the BLS score decreased from 12 to 2, and the ADL increased from 23 to 70. The other patient demonstrated increases to 10 and 3 on the FMBS and HG, respectively, with the BLS decreasing from 13 to 3, and the ADL increasing from 25 to 60. Therefore, in the rehabilitation treatment of Pusher syndrome complicated by hemispatial neglect due to basal ganglia stroke, visual deprivation can significantly improve motor function and shorten the treatment course.
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Affiliation(s)
- Qian Zhang
- Rehabilitation Department, The Geriatric Hospital Affiliated to Nanjing Medical University, Nanjing, China
| | - Lixia Zhang
- Rehabilitation Department, The Geriatric Hospital Affiliated to Nanjing Medical University, Nanjing, China
| | - Wei He
- Rehabilitation Department, Rehabilitation Hospital Affiliated to Nanjing Institute of Physical Education, Wuxi, China
| | - Xuemei Zheng
- Rehabilitation Department, Xinjiang Korla Bazhou People's Hospital, Korla, China
| | - Zhengrui Zhao
- Rehabilitation Department, The Geriatric Hospital Affiliated to Nanjing Medical University, Nanjing, China
| | - Yuanli Li
- School of Rehabilitation Science, Shanghai University of Traditional Chinese Medicine, Shanghai, China.,Engineering Research Center of Traditional Chinese Medicine Intelligent Rehabilitation, Ministry of Education, Shanghai, China
| | - Shutian Xu
- School of Rehabilitation Science, Shanghai University of Traditional Chinese Medicine, Shanghai, China.,Engineering Research Center of Traditional Chinese Medicine Intelligent Rehabilitation, Ministry of Education, Shanghai, China
| | - Juan Zheng
- Rehabilitation Department, The Geriatric Hospital Affiliated to Nanjing Medical University, Nanjing, China
| | - Xin Zhuang
- Rehabilitation Department, The Geriatric Hospital Affiliated to Nanjing Medical University, Nanjing, China
| | - Wenting Jia
- Rehabilitation Department, The Geriatric Hospital Affiliated to Nanjing Medical University, Nanjing, China
| | - Chengyuan Zhu
- Rehabilitation Department, The Geriatric Hospital Affiliated to Nanjing Medical University, Nanjing, China
| | - Hua Xu
- Rehabilitation Department, The Geriatric Hospital Affiliated to Nanjing Medical University, Nanjing, China
| | - Chunlei Shan
- School of Rehabilitation Science, Shanghai University of Traditional Chinese Medicine, Shanghai, China.,Engineering Research Center of Traditional Chinese Medicine Intelligent Rehabilitation, Ministry of Education, Shanghai, China.,Center of Rehabilitation Medicine, Yueyang Hospital of Integrated Traditional Chinese and Western Medicine, Shanghai, China
| | - Wenhua Chen
- Rehabilitation Department, The First People's Hospital Affiliated With Shanghai Jiao Tong University, Shanghai, China
| | - Jingpu Zhao
- Rehabilitation Department, The First Affiliated Hospital of Shenzhen University, Shenzhen, China
| | - Sijing Chen
- Rehabilitation Department, The First Affiliated Hospital of Nanjing Medical University, Nanjing, China
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3
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Dakos AS, Jiang H, Stein BE, Rowland BA. Using the Principles of Multisensory Integration to Reverse Hemianopia. Cereb Cortex 2021; 30:2030-2041. [PMID: 31799618 DOI: 10.1093/cercor/bhz220] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2019] [Revised: 08/03/2019] [Accepted: 08/28/2019] [Indexed: 11/14/2022] Open
Abstract
Hemianopia can be rehabilitated by an auditory-visual "training" procedure, which restores visual responsiveness in midbrain neurons indirectly compromised by the cortical lesion and reinstates vision in contralesional space. Presumably, these rehabilitative changes are induced via mechanisms of multisensory integration/plasticity. If so, the paradigm should fail if the stimulus configurations violate the spatiotemporal principles that govern these midbrain processes. To test this possibility, hemianopic cats were provided spatially or temporally noncongruent auditory-visual training. Rehabilitation failed in all cases even after approximately twice the number of training trials normally required for recovery, and even after animals learned to approach the location of the undetected visual stimulus. When training was repeated with these stimuli in spatiotemporal concordance, hemianopia was resolved. The results identify the conditions needed to engage changes in remaining neural circuits required to support vision in the absence of visual cortex, and have implications for rehabilitative strategies in human patients.
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Affiliation(s)
| | - Huai Jiang
- Department of Neurobiology & Anatomy, Wake Forest University School of Medicine, Winston-Salem, NC 27157-1010, USA
| | - Barry E Stein
- Department of Neurobiology & Anatomy, Wake Forest University School of Medicine, Winston-Salem, NC 27157-1010, USA
| | - Benjamin A Rowland
- Department of Neurobiology & Anatomy, Wake Forest University School of Medicine, Winston-Salem, NC 27157-1010, USA
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4
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Sajid N, Parr T, Gajardo-Vidal A, Price CJ, Friston KJ. Paradoxical lesions, plasticity and active inference. Brain Commun 2020; 2:fcaa164. [PMID: 33376985 PMCID: PMC7750943 DOI: 10.1093/braincomms/fcaa164] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2020] [Revised: 09/07/2020] [Accepted: 09/09/2020] [Indexed: 12/01/2022] Open
Abstract
Paradoxical lesions are secondary brain lesions that ameliorate functional deficits caused by the initial insult. This effect has been explained in several ways; particularly by the reduction of functional inhibition, or by increases in the excitatory-to-inhibitory synaptic balance within perilesional tissue. In this article, we simulate how and when a modification of the excitatory-inhibitory balance triggers the reversal of a functional deficit caused by a primary lesion. For this, we introduce in-silico lesions to an active inference model of auditory word repetition. The first in-silico lesion simulated damage to the extrinsic (between regions) connectivity causing a functional deficit that did not fully resolve over 100 trials of a word repetition task. The second lesion was implemented in the intrinsic (within region) connectivity, compromising the model's ability to rebalance excitatory-inhibitory connections during learning. We found that when the second lesion was mild, there was an increase in experience-dependent plasticity that enhanced performance relative to a single lesion. This paradoxical lesion effect disappeared when the second lesion was more severe because plasticity-related changes were disproportionately amplified in the intrinsic connectivity, relative to lesioned extrinsic connections. Finally, this framework was used to predict the physiological correlates of paradoxical lesions. This formal approach provides new insights into the computational and neurophysiological mechanisms that allow some patients to recover after large or multiple lesions.
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Affiliation(s)
- Noor Sajid
- Wellcome Centre for Human Neuroimaging, University College London, London WC1N 3AR, UK
| | - Thomas Parr
- Wellcome Centre for Human Neuroimaging, University College London, London WC1N 3AR, UK
| | - Andrea Gajardo-Vidal
- Wellcome Centre for Human Neuroimaging, University College London, London WC1N 3AR, UK
| | - Cathy J Price
- Wellcome Centre for Human Neuroimaging, University College London, London WC1N 3AR, UK
| | - Karl J Friston
- Wellcome Centre for Human Neuroimaging, University College London, London WC1N 3AR, UK
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5
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Toba MN, Godefroy O, Rushmore RJ, Zavaglia M, Maatoug R, Hilgetag CC, Valero-Cabré A. Revisiting 'brain modes' in a new computational era: approaches for the characterization of brain-behavioural associations. Brain 2020; 143:1088-1098. [PMID: 31764975 DOI: 10.1093/brain/awz343] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2019] [Revised: 08/07/2019] [Accepted: 08/28/2019] [Indexed: 11/12/2022] Open
Abstract
The study of brain-function relationships is undergoing a conceptual and methodological transformation due to the emergence of network neuroscience and the development of multivariate methods for lesion-deficit inferences. Anticipating this process, in 1998 Godefroy and co-workers conceptualized the potential of four elementary typologies of brain-behaviour relationships named 'brain modes' (unicity, equivalence, association, summation) as building blocks able to describe the association between intact or lesioned brain regions and cognitive processes or neurological deficits. In the light of new multivariate lesion inference and network approaches, we critically revisit and update the original theoretical notion of brain modes, and provide real-life clinical examples that support their existence. To improve the characterization of elementary units of brain-behavioural relationships further, we extend such conceptualization with a fifth brain mode (mutual inhibition/masking summation). We critically assess the ability of these five brain modes to account for any type of brain-function relationship, and discuss past versus future contributions in redefining the anatomical basis of human cognition. We also address the potential of brain modes for predicting the behavioural consequences of lesions and their future role in the design of cognitive neurorehabilitation therapies.
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Affiliation(s)
- Monica N Toba
- Laboratory of Functional Neurosciences (EA 4559), University Hospital of Amiens and University of Picardy Jules Verne, Amiens, France
| | - Olivier Godefroy
- Laboratory of Functional Neurosciences (EA 4559), University Hospital of Amiens and University of Picardy Jules Verne, Amiens, France
| | - R Jarrett Rushmore
- Laboratory of Cerebral Dynamics, Plasticity and Rehabilitation, Boston University School of Medicine, Boston, MA 02118, USA.,Department of Psychiatry, Massachusetts General Hospital, Boston, MA, USA.,Psychiatry Neuroimaging Laboratory, Brigham and Women's Hospital, Boston, MA, USA
| | - Melissa Zavaglia
- Institute of Computational Neuroscience, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.,Focus Area Health, Jacobs University Bremen, Germany
| | - Redwan Maatoug
- Cerebral Dynamics, Plasticity and Rehabilitation Group, FRONTLAB Team, Brain and Spine Institute, ICM, Paris, France.,Sorbonne Université, INSERM UMR S 1127, CNRS UMR 7225, F-75013, and IHU-A-ICM, Paris, France
| | - Claus C Hilgetag
- Institute of Computational Neuroscience, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.,Health Sciences Department, Boston University, 635 Commonwealth Ave. Boston, MA 02215, USA
| | - Antoni Valero-Cabré
- Laboratory of Cerebral Dynamics, Plasticity and Rehabilitation, Boston University School of Medicine, Boston, MA 02118, USA.,Cerebral Dynamics, Plasticity and Rehabilitation Group, FRONTLAB Team, Brain and Spine Institute, ICM, Paris, France.,Sorbonne Université, INSERM UMR S 1127, CNRS UMR 7225, F-75013, and IHU-A-ICM, Paris, France.,Cognitive Neuroscience and Information Technology Research Program, Open University of Catalonia (UOC), Barcelona, Catalunya, Spain
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6
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Abstract
BACKGROUND Noninvasive brain stimulation can modulate neural processing within the motor cortex and thereby might be beneficial in the rehabilitation of hemispatial neglect after stroke. METHODS We review the pertinent literature regarding the use of transcranial direct current stimulation (tDCS) and transcranial magnetic stimulation in order to facilitate recovery of hemispatial neglect after stroke. RESULTS Twenty controlled trials (including 443 stroke patients) matched our inclusion criteria. Methodology and results of each study are presented in a comparative approach. Current data seem to indicate a better efficiency of repetitive transcranial magnetic stimulation, compared to tDCS to ameliorate hemispatial neglect after stroke. CONCLUSIONS Noninvasive brain stimulation has the potential to facilitate recovery of hemispatial neglect after stroke, but until today, there are not enough data to claim its routine use.
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7
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Valero-Cabré A, Toba MN, Hilgetag CC, Rushmore RJ. Perturbation-driven paradoxical facilitation of visuo-spatial function: Revisiting the 'Sprague effect'. Cortex 2019; 122:10-39. [PMID: 30905382 DOI: 10.1016/j.cortex.2019.01.031] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2018] [Revised: 12/17/2018] [Accepted: 01/30/2019] [Indexed: 01/29/2023]
Abstract
The 'Sprague Effect' described in the seminal paper of James Sprague (Science 153:1544-1547, 1966a) is an unexpected paradoxical effect in which a second brain lesion reversed functional deficits induced by an earlier lesion. It was observed initially in the cat where severe and permanent contralateral visually guided attentional deficits generated by the ablation of large areas of the visual cortex were reversed by the subsequent removal of the superior colliculus (SC) opposite to the cortical lesion or by the splitting of the collicular commissure. Physiologically, this effect has been explained in several ways-most notably by the reduction of the functional inhibition of the ipsilateral SC by the contralateral SC, and the restoration of normal interactions between cortical and midbrain structures after ablation. In the present review, we aim at reappraising the 'Sprague Effect' by critically analyzing studies that have been conducted in the feline and human brain. Moreover, we assess applications of the 'Sprague Effect' in the rehabilitation of visually guided attentional impairments by using non-invasive therapeutic approaches such as transcranial magnetic stimulation (TMS) and transcranial direct-current stimulation (tDCS). We also review theoretical models of the effect that emphasize the inhibition and balancing between the two hemispheres and show implications for lesion inference approaches. Last, we critically review whether the resulting inter-hemispheric rivalry theories lead toward an efficient rehabilitation of stroke in humans. We conclude by emphasizing key challenges in the field of 'Sprague Effect' applications in order to design better therapies for brain-damaged patients.
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Affiliation(s)
- Antoni Valero-Cabré
- Cerebral Dynamics, Plasticity and Rehabilitation Group, Frontlab Team, Brain and Spine Institute, ICM, Paris, France; CNRS UMR 7225, Inserm UMR S 1127, Sorbonne Universités, UPMC Paris 06, F-75013, IHU-A-ICM, Paris, France; Laboratory for Cerebral Dynamics, Plasticity & Rehabilitation, Boston University School of Medicine, Boston, MA, USA.
| | - Monica N Toba
- Laboratory of Functional Neurosciences (EA 4559), University Hospital of Amiens and University of Picardy Jules Verne, Amiens, France
| | - Claus C Hilgetag
- Institute of Computational Neuroscience, University Medical Center Eppendorf, Hamburg University, Germany; Department of Health Sciences, Boston University, Boston, MA, USA
| | - R Jarrett Rushmore
- Laboratory for Cerebral Dynamics, Plasticity & Rehabilitation, Boston University School of Medicine, Boston, MA, USA.
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8
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Abstract
The purpose of this perspective is twofold: 1) to alert and inform the neurospychology and neurology communities on how animal models can improve our understanding of spatial neglect in humans, and 2) to serve as a guide to rehabilitation strategies. Spatial neglect is a neurological syndrome that is inextricably linked to the ability to overtly or covertly reorient attention to new loci. Literature describing variants of neglect leads to the perception of lesion-induced neglect as a uniquely human syndrome for which there are limited treatment options. To the contrary, neglect has been reversed in laboratory animals, and results show that adequate neural representations and motor mechanisms for reversal are present despite damaged or deactivated cerebral cortex. These results and conclusions provoke thought on strategies that can be employed on humans to cancel neglect, and they suggest that long-term amelioration of neglect can be induced by training of specific bypass circuits.
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Affiliation(s)
- Bertram R Payne
- Cerebral Dynamics, Rehabilitation and Plasticity, Department of Anatomy and Neurobiology, Boston University School of Medicine, MA 02118, USA.
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9
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Snyder A, Bahramali H, Hawker T, Mitchell DJ. Savant-like Numerosity Skills Revealed in Normal People by Magnetic Pulses. Perception 2016; 35:837-45. [PMID: 16836048 DOI: 10.1068/p5539] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Oliver Sacks observed autistic twins who instantly guessed the exact number of match-sticks that had just fallen on the floor, saying in unison “111”. To test the suggestion that normal individuals have the capacity for savant numerosity, we temporarily simulated the savant condition in normal people by inhibiting the left anterior temporal lobe of twelve participants with repetitive transcranial magnetic stimulation (rTMS). This site has been implicated in the savant condition. Ten participants improved their ability to accurately guess the number of discrete items immediately following rTMS and, of these, eight became worse at guessing as the effects of the pulses receded. The probability of as many as eight out of twelve people doing best just after rTMS and not after sham stimulation by chance alone is less than one in one thousand.
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Affiliation(s)
- Allan Snyder
- Centre for the Mind, Australian National University, Canberra, ACT 0200, Australia.
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10
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Causal functional contributions and interactions in the attention network of the brain: an objective multi-perturbation analysis. Brain Struct Funct 2015; 221:2553-68. [PMID: 26002616 DOI: 10.1007/s00429-015-1058-z] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2014] [Accepted: 05/06/2015] [Indexed: 10/23/2022]
Abstract
Spatial attention is a prime example for the distributed network functions of the brain. Lesion studies in animal models have been used to investigate intact attentional mechanisms as well as perspectives for rehabilitation in the injured brain. Here, we systematically analyzed behavioral data from cooling deactivation and permanent lesion experiments in the cat, where unilateral deactivation of the posterior parietal cortex (in the vicinity of the posterior middle suprasylvian cortex, pMS) or the superior colliculus (SC) cause a severe neglect in the contralateral hemifield. Counterintuitively, additional deactivation of structures in the opposite hemisphere reverses the deficit. Using such lesion data, we employed a game-theoretical approach, multi-perturbation Shapley value analysis (MSA), for inferring functional contributions and network interactions of bilateral pMS and SC from behavioral performance in visual attention studies. The approach provides an objective theoretical strategy for lesion inferences and allows a unique quantitative characterization of regional functional contributions and interactions on the basis of multi-perturbations. The quantitative analysis demonstrated that right posterior parietal cortex and superior colliculus made the strongest positive contributions to left-field orienting, while left brain regions had negative contributions, implying that their perturbation may reverse the effects of contralateral lesions or improve normal function. An analysis of functional modulations and interactions among the regions revealed redundant interactions (implying functional overlap) between regions within each hemisphere, and synergistic interactions between bilateral regions. To assess the reliability of the MSA method in the face of variable and incomplete input data, we performed a sensitivity analysis, investigating how much the contribution values of the four regions depended on the performance of specific configurations and on the prediction of unknown performances. The results suggest that the MSA approach is sensitive to categorical, but insensitive to gradual changes in the input data. Finally, we created a basic network model that was based on the known anatomical interactions among cortical-tectal regions and reproduced the experimentally observed behavior in visual orienting. We discuss the structural organization of the network model relative to the causal modulations identified by MSA, to aid a mechanistic understanding of the attention network of the brain.
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11
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Takahata K, Saito F, Muramatsu T, Yamada M, Shirahase J, Tabuchi H, Suhara T, Mimura M, Kato M. Emergence of realism: Enhanced visual artistry and high accuracy of visual numerosity representation after left prefrontal damage. Neuropsychologia 2014; 57:38-49. [PMID: 24631259 DOI: 10.1016/j.neuropsychologia.2014.02.022] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2013] [Revised: 02/01/2014] [Accepted: 02/24/2014] [Indexed: 10/25/2022]
Abstract
Over the last two decades, evidence of enhancement of drawing and painting skills due to focal prefrontal damage has accumulated. It is of special interest that most artworks created by such patients were highly realistic ones, but the mechanism underlying this phenomenon remains to be understood. Our hypothesis is that enhanced tendency of realism was associated with accuracy of visual numerosity representation, which has been shown to be mediated predominantly by right parietal functions. Here, we report a case of left prefrontal stroke, where the patient showed enhancement of artistic skills of realistic painting after the onset of brain damage. We investigated cognitive, functional and esthetic characteristics of the patient׳s visual artistry and visual numerosity representation. Neuropsychological tests revealed impaired executive function after the stroke. Despite that, the patient׳s visual artistry related to realism was rather promoted across the onset of brain damage as demonstrated by blind evaluation of the paintings by professional art reviewers. On visual numerical cognition tasks, the patient showed higher performance in comparison with age-matched healthy controls. These results paralleled increased perfusion in the right parietal cortex including the precuneus and intraparietal sulcus. Our data provide new insight into mechanisms underlying change in artistic style due to focal prefrontal lesion.
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Affiliation(s)
- Keisuke Takahata
- Department of Neuropsychiatry, Keio University School of Medicine, 35 Shinanomachi, Shinjuku, Tokyo 160-8582, Japan; Clinical Neuroimaging Team, Molecular Neuroimaging Program, Molecular Imaging Center, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage, Chiba, Chiba 263-8555, Japan.
| | - Fumie Saito
- Department of Neuropsychiatry, Keio University School of Medicine, 35 Shinanomachi, Shinjuku, Tokyo 160-8582, Japan.
| | - Taro Muramatsu
- Department of Neuropsychiatry, Keio University School of Medicine, 35 Shinanomachi, Shinjuku, Tokyo 160-8582, Japan.
| | - Makiko Yamada
- Clinical Neuroimaging Team, Molecular Neuroimaging Program, Molecular Imaging Center, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage, Chiba, Chiba 263-8555, Japan.
| | - Joichiro Shirahase
- Department of Neuropsychiatry, Keio University School of Medicine, 35 Shinanomachi, Shinjuku, Tokyo 160-8582, Japan; Center for Stress Research (CSR), Keio University, 35 Shinanomachi, Shinjuku, Tokyo 160-8582, Japan.
| | - Hajime Tabuchi
- Department of Neuropsychiatry, Keio University School of Medicine, 35 Shinanomachi, Shinjuku, Tokyo 160-8582, Japan.
| | - Tetsuya Suhara
- Clinical Neuroimaging Team, Molecular Neuroimaging Program, Molecular Imaging Center, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage, Chiba, Chiba 263-8555, Japan.
| | - Masaru Mimura
- Department of Neuropsychiatry, Keio University School of Medicine, 35 Shinanomachi, Shinjuku, Tokyo 160-8582, Japan.
| | - Motoichiro Kato
- Department of Neuropsychiatry, Keio University School of Medicine, 35 Shinanomachi, Shinjuku, Tokyo 160-8582, Japan; Center for Stress Research (CSR), Keio University, 35 Shinanomachi, Shinjuku, Tokyo 160-8582, Japan.
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12
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Bocci T, Pietrasanta M, Cerri C, Restani L, Caleo M, Sartucci F. Visual callosal connections: role in visual processing in health and disease. Rev Neurosci 2014; 25:113-27. [DOI: 10.1515/revneuro-2013-0025] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2013] [Accepted: 09/07/2013] [Indexed: 11/15/2022]
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13
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Ossandón JP, Onat S, Cazzoli D, Nyffeler T, Müri R, König P. Unmasking the contribution of low-level features to the guidance of attention. Neuropsychologia 2012; 50:3478-87. [PMID: 23044277 DOI: 10.1016/j.neuropsychologia.2012.09.043] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2011] [Revised: 09/19/2012] [Accepted: 09/26/2012] [Indexed: 11/18/2022]
Affiliation(s)
- José P Ossandón
- Universität Osnabrück, Institut für Kognitionswissenschaft, Albrechtstr. 28, 49076 Osnabrück, Germany.
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14
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Chica AB, Valero-Cabre A, Paz-Alonso PM, Bartolomeo P. Causal Contributions of the Left Frontal Eye Field to Conscious Perception. Cereb Cortex 2012; 24:745-53. [DOI: 10.1093/cercor/bhs357] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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15
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Chica AB, Bartolomeo P, Valero-Cabré A. Dorsal and ventral parietal contributions to spatial orienting in the human brain. J Neurosci 2011; 31:8143-9. [PMID: 21632936 PMCID: PMC6622880 DOI: 10.1523/jneurosci.5463-10.2010] [Citation(s) in RCA: 124] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2010] [Accepted: 11/17/2010] [Indexed: 11/21/2022] Open
Abstract
Influential functional magnetic resonance imaging (fMRI)-based models have involved a dorsal frontoparietal network in the orienting of both endogenous and exogenous attention, and a ventral system in attentional reorienting to task-relevant events. Nonetheless, given the low temporal resolution and susceptibility to epiphenomenal activations of fMRI, such depictions remain highly debated. We hereby benefited from the high temporal resolution and causal power of event-related transcranial magnetic stimulation to explore the implications of key dorsal and ventral parietal regions in those two types of attention. We provide for the first time causal evidence of right intraparietal sulcus involvement in both types of attentional orienting, while we link the temporoparietal junction with the orienting of exogenous but not endogenous spatial attention.
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Affiliation(s)
- Ana B. Chica
- INSERM-U975, Centre de Recherche de l'Institut du Cerveau et de la Moëlle Epinière (CRICM) and Université Pierre et Marie Curie (UPMC), Groupe Hospitalier Pitié-Salpêtrière, F-75013 Paris, France
| | - Paolo Bartolomeo
- INSERM-U975, Centre de Recherche de l'Institut du Cerveau et de la Moëlle Epinière (CRICM) and Université Pierre et Marie Curie (UPMC), Groupe Hospitalier Pitié-Salpêtrière, F-75013 Paris, France
- Assistance Publique-Hôpitaux de Paris, Groupe Hospitalier Pitié-Salpêtrière, Fédération de Neurologie, 75013 Paris, France
- Department of Psychology, Catholic University, 20123 Milan, Italy
| | - Antoni Valero-Cabré
- Centre National de la Recherche Scientifique (CNRS) UMR 7225, Centre de Recherche de l'Institut de Cerveau et da la Moëlle Epinière (CRICM), Université Pierre et Marie Curie (UPMC), 75651 Paris, France
- Laboratory for Cerebral Dynamics, Plasticity, and Rehabilitation, Department of Anatomy and Neurobiology, Boston University School of Medicine, Boston, Massachusetts 02118, and
- Cognitive Neuroscience and Information Technology Research Program, School of Psychology, Open University of Catalonia (UOC), 08018 Barcelona, Spain
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16
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Affiliation(s)
- Klaas Enno Stephan
- Laboratory for Social and Neural Systems Research, Institute for Empirical Research in Economics, University of Zurich, Zurich, Switzerland
- Wellcome Trust Centre for Neuroimaging, Institute of Neurology, University College London, London, United Kingdom
- * E-mail:
| | | | - Claus C. Hilgetag
- School of Engineering and Science, Jacobs University Bremen, Bremen, Germany
- Department of Health Sciences, Boston University, Boston, Massachusetts, United States of America
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17
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Motter AE. Improved network performance via antagonism: From synthetic rescues to multi-drug combinations. Bioessays 2010; 32:236-245. [PMID: 20127700 PMCID: PMC2841822 DOI: 10.1002/bies.200900128] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Recent research shows that a faulty or sub-optimally operating metabolic network can often be rescued by the targeted removal of enzyme-coding genes – the exact opposite of what traditional gene therapy would suggest. Predictions go as far as to assert that certain gene knockouts can restore the growth of otherwise nonviable gene-deficient cells. Many questions follow from this discovery: What are the underlying mechanisms? How generalizable is this effect? What are the potential applications? Here, I approach these questions from the perspective of compensatory perturbations on networks. Relations are drawn between such synthetic rescues and naturally occurring cascades of reaction inactivation, as well as their analogs in physical and other biological networks. I specially discuss how rescue interactions can lead to the rational design of antagonistic drug combinations that select against resistance and how they can illuminate medical research on cancer, antibiotics, and metabolic diseases.
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Affiliation(s)
- Adilson E Motter
- Department of Physics and Astronomy and Northwestern Institute on Complex Systems, Northwestern University, Evanston, IL, USA
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18
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Snyder A. Explaining and inducing savant skills: privileged access to lower level, less-processed information. Philos Trans R Soc Lond B Biol Sci 2009; 364:1399-405. [PMID: 19528023 PMCID: PMC2677578 DOI: 10.1098/rstb.2008.0290] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
I argue that savant skills are latent in us all. My hypothesis is that savants have privileged access to lower level, less-processed information, before it is packaged into holistic concepts and meaningful labels. Owing to a failure in top-down inhibition, they can tap into information that exists in all of our brains, but is normally beyond conscious awareness. This suggests why savant skills might arise spontaneously in otherwise normal people, and why such skills might be artificially induced by low-frequency repetitive transcranial magnetic stimulation. It also suggests why autistic savants are atypically literal with a tendency to concentrate more on the parts than on the whole and why this offers advantages for particular classes of problem solving, such as those that necessitate breaking cognitive mindsets. A strategy of building from the parts to the whole could form the basis for the so-called autistic genius. Unlike the healthy mind, which has inbuilt expectations of the world (internal order), the autistic mind must simplify the world by adopting strict routines (external order).
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Affiliation(s)
- Allan Snyder
- Centre for the Mind, University of Sydney, New South Wales 2006, Australia.
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19
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Gallate J, Chi R, Ellwood S, Snyder A. Reducing false memories by magnetic pulse stimulation. Neurosci Lett 2008; 449:151-4. [PMID: 19022348 DOI: 10.1016/j.neulet.2008.11.021] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2008] [Revised: 10/21/2008] [Accepted: 11/10/2008] [Indexed: 10/21/2022]
Abstract
False memories are ubiquitous and often to our detriment. Yet, certain pathologies, including anterior temporal lobe dementia and autism, can lead to literal recall and thus greater resistance to false memories. This inspired us to reduce false memories by temporarily inhibiting the left anterior temporal lobe, using low frequency magnetic pulse stimulation. This site has been implicated in semantic memory and conceptual labelling. After active stimulation, participants in the sham/TMS group had 36% fewer false memories than they had with sham stimulation, and intact veridical memory. This is comparable to the improvement that people with autism and semantic dementia show over "normal" individuals. This finding suggests a potential method for reducing certain types of false memories.
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Affiliation(s)
- Jason Gallate
- Centre for the Mind, University of Sydney, Sydney, NSW 2006, Australia
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20
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Valero-Cabré A, Pascual-Leone A, Rushmore RJ. Cumulative sessions of repetitive transcranial magnetic stimulation (rTMS) build up facilitation to subsequent TMS-mediated behavioural disruptions. Eur J Neurosci 2008; 27:765-74. [PMID: 18279329 DOI: 10.1111/j.1460-9568.2008.06045.x] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Affiliation(s)
- Antoni Valero-Cabré
- Laboratory for Cerebral Dynamics, Plasticity and Rehabilitation, Department of Anatomy and Neurobiology, Boston University School of Medicine, Boston, MA 02118, USA.
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21
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Stephan KE, Marshall JC, Penny WD, Friston KJ, Fink GR. Interhemispheric integration of visual processing during task-driven lateralization. J Neurosci 2007; 27:3512-22. [PMID: 17392467 PMCID: PMC2636903 DOI: 10.1523/jneurosci.4766-06.2007] [Citation(s) in RCA: 125] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The mechanisms underlying interhemispheric integration (IHI) remain poorly understood, particularly for lateralized cognitive processes. To test competing theories of IHI, we constructed and fitted dynamic causal models to functional magnetic resonance data from two visual tasks that operated on identical stimuli but showed opposite hemispheric dominance. Using a systematic Bayesian model selection procedure, we found that, in the ventral visual stream, which was activated by letter judgments, interhemispheric connections mediated asymmetric information transfer from the nonspecialized right to the specialized left hemisphere when the latter did not have direct access to stimulus information. Notably, this form of IHI did not engage all areas activated by the task but was specific for areas in the lingual and fusiform gyri. In the dorsal stream, activated by spatial judgments, it did not matter which hemisphere received the stimulus: interhemispheric coupling increased bidirectionally, reflecting recruitment of the nonspecialized left hemisphere. Again, not all areas activated by the task were involved in this form of IHI; instead, it was restricted to interactions between areas in the superior parietal gyrus. Overall, our results provide direct neurophysiological evidence, in terms of effective connectivity, for the existence of context-dependent mechanisms of IHI that are implemented by specific visual areas during task-driven lateralization.
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Affiliation(s)
- Klaas E Stephan
- Wellcome Trust Centre for Neuroimaging, Institute of Neurology, University College London, London WC1N 3BG, United Kingdom.
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22
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Niemeier M, Stojanoski B, Greco AL. Influences of time and spatial frequency on the perceptual bias: Evidence for competition between hemispheres. Neuropsychologia 2007; 45:1029-40. [PMID: 17049566 DOI: 10.1016/j.neuropsychologia.2006.09.006] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2006] [Revised: 09/10/2006] [Accepted: 09/11/2006] [Indexed: 11/29/2022]
Abstract
Perceptual biases for various visual features, such as size, luminance and numerosity, have been implicated with a right-hemisphere dominance in spatial and attentional functions and/or an asymmetrical competition between the two hemispheres. However, the mechanisms underlying these biases are poorly understood. For example, it has been largely ignored that processing of those features is closely interconnected with spatial frequency filters. To probe the influence of spatial frequencies on perceptual biases, here we used a new gratingscales task in neurologically healthy participants. We found that perceptual bias was strongly influenced within a bandwidth of spatial frequencies and that this bias correlated with a bias for luminance depending on presentation time. Furthermore, our participants, divided into two subgroups of perceptually "sensitive" and "insensitive" performers, showed considerably different, presentation time-dependent patterns of perceptual bias. While both groups were biased to the left, insensitive performers more than sensitive performers, these biases varied in a mirror-symmetric manner such that one group showed peaks of bias at times when the other group showed minima and vice versa. Our data suggest that perceptual bias results from an interhemispheric competition within a right-dominant system responsive to spatial frequencies, luminance and perhaps other magnitudes including abstract ones.
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Affiliation(s)
- Matthias Niemeier
- Centre for Computational Cognitive Neuroscience, Department of Life Sciences, Canada
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23
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Abstract
According to the dominant focus model, the differential activation of the thalamocortical network is a sufficient condition for the diversity of states of consciousness to occur, and coherent patterns of interactive forebrain activation peaks are sufficient to generate specific conscious figures against ground. These minimal assumptions are consonant with the known properties of unilateral neglect. It becomes unnecessary to suppose that consciousness is an independent entity, occupies a dedicated location in the brain, is contingent on a minimal level of neural complexity, plays a causal role in enabling perception or action, or evolved because it plays any such role.
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Affiliation(s)
- Marcel Kinsbourne
- Department of Psychology, New School University, New York, NY 10003, USA.
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24
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Keinan A, Sandbank B, Hilgetag CC, Meilijson I, Ruppin E. Fair attribution of functional contribution in artificial and biological networks. Neural Comput 2004; 16:1887-915. [PMID: 15265327 DOI: 10.1162/0899766041336387] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
This letter presents the multi-perturbation Shapley value analysis (MSA), an axiomatic, scalable, and rigorous method for deducing causal function localization from multiple perturbations data. The MSA, based on fundamental concepts from game theory, accurately quantifies the contributions of network elements and their interactions, overcoming several shortcomings of previous function localization approaches. Its successful operation is demonstrated in both the analysis of a neurophysiological model and of reversible deactivation data. The MSA has a wide range of potential applications, including the analysis of reversible deactivation experiments, neuronal laser ablations, and transcranial magnetic stimulation "virtual lesions," as well as in providing insight into the inner workings of computational models of neurophysiological systems.
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Affiliation(s)
- Alon Keinan
- School of Computer Sciences, Tel-Aviv University, Tel-Aviv, Israel.
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25
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Payne BR, Rushmore RJ. Functional circuitry underlying natural and interventional cancellation of visual neglect. Exp Brain Res 2003; 154:127-53. [PMID: 14625667 DOI: 10.1007/s00221-003-1660-9] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2003] [Accepted: 07/28/2003] [Indexed: 10/26/2022]
Abstract
A large body of work demonstrates that lesions at multiple levels of the visual system induce neglect of stimuli in the contralesional visual field and that the neglect dissipates as neural compensations naturally emerge. Other studies show that interventional manipulations of cerebral cortex, superior colliculus or deep-lying midbrain structures have the power to attenuate, or cancel, the neglect and reinstate orienting into a neglected hemifield, and even into a profound cortically blind field. These results, and those derived from experiments on the behavioral impacts of unilateral and bilateral lesions, lead us to evaluate the repercussions of unilateral and bilateral deactivations, neural compensations and cancellations of attentional deficits in terms of an overarching hypothesis of neglect. The cancellations can be both striking and enduring, and they suggest that therapeutic strategies can be developed to reverse or ameliorate neglect in human patients. Animal studies show that in many instances of neglect adequate representations and the accompanying motor mechanisms are present despite the lesion and they simply need to be unmasked and brought into use to effect a remedy.
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Affiliation(s)
- Bertram R Payne
- Cerebral Dynamics, Department of Anatomy and Neurobiology, Boston University School of Medicine, W702, Boston, MA 02118, USA.
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26
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Payne BR, Lomber SG, Rushmore RJ, Pascual-Leone A. Cancellation of visuoparietal lesion-induced spatial neglect. Exp Brain Res 2003; 150:395-8. [PMID: 12698319 DOI: 10.1007/s00221-003-1473-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2003] [Accepted: 03/16/2003] [Indexed: 10/20/2022]
Abstract
In humans lesions of right visuoparietal cortex induce a neglect of the contralesional visual field that is characterized in its mild form by inattentiveness to objects and events and, in its more severe form, by a condition that has many features that are indistinguishable from blindness. Here we show that spatial neglect can be induced in cats by lesions of posterior and inferior visuoparietal cortex, and that the lesion-induced neglect can be cancelled by cooling deactivation of the same region in the opposite hemisphere.
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Affiliation(s)
- Bertram R Payne
- Cerebral Dynamics, Department of Anatomy and Neurobiology, Boston University School of Medicine, 700 Albany Street, Boston, MA 02118, USA.
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27
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Hilgetag CC, Kötter R, Théoret H, Claßen J, Wolters A, Pascual-Leone A. Bilateral competitive processing of visual spatial attention in the human brain. Neurocomputing 2003. [DOI: 10.1016/s0925-2312(02)00776-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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28
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Hilgetag CC, Lomber SG, Rushmore RJ, Payne BR. Topographic restoration of visual spatial attention in the cortically blind cat. Neurocomputing 2002. [DOI: 10.1016/s0925-2312(02)00480-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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29
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Parker GJM, Stephan KE, Barker GJ, Rowe JB, MacManus DG, Wheeler-Kingshott CAM, Ciccarelli O, Passingham RE, Spinks RL, Lemon RN, Turner R. Initial demonstration of in vivo tracing of axonal projections in the macaque brain and comparison with the human brain using diffusion tensor imaging and fast marching tractography. Neuroimage 2002; 15:797-809. [PMID: 11906221 DOI: 10.1006/nimg.2001.0994] [Citation(s) in RCA: 152] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Diffusion tensor imaging (DTI), a magnetic resonance imaging technique, is used to infer major axonal projections in the macaque and human brain. This study investigates the feasibility of using known macaque anatomical connectivity as a "gold-standard" for the evaluation of DTI tractography methods. Connectivity information is determined from the DTI data using fast marching tractography (FMT), a novel tract-tracing (tractography) method. We show for the first time that it is possible to determine, in an entirely noninvasive manner, anatomical connection pathways and maps of an anatomical connectivity metric in the macaque brain using a standard clinical scanner and that these pathways are consistent with known anatomy. Analogous human anatomical connectivity is also presented for the first time using the FMT method, and the results are compared. The current limitations of the methodology and possibilities available for further studies are discussed.
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Affiliation(s)
- Geoffrey J M Parker
- NMR Research Unit, Institute of Neurology, University College London, Queen Square, London WC1N 3BG, United Kingdom
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30
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Lomber SG, Payne BR, Cornwell P. Role of the superior colliculus in analyses of space: superficial and intermediate layer contributions to visual orienting, auditory orienting, and visuospatial discriminations during unilateral and bilateral deactivations. J Comp Neurol 2001; 441:44-57. [PMID: 11745634 DOI: 10.1002/cne.1396] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The superior colliculus (SC) has been implicated in spatial analyses of the environment, although few behavioral studies have explicitly tested this role. To test its imputed role in spatial analyses, we used a battery of four spatial tasks combined with unilateral and bilateral cooling deactivation of the upper and intermediate layers of the superior colliculus. We tested the abilities of cats to orient to three different stimuli: (1) moving visual, (2) stationary visual, (3) stationary white-noise aural. Furthermore, we tested the ability of the cats to discriminate the relative spatial position of a landmark. Unilateral cooling deactivation of the superficial layers of the SC induced a profound neglect of both moving and stationary visual stimuli presented in, and landmark objects located within, the contralateral hemifield. However, responses to auditory stimuli were unimpaired. Unilateral cooling deactivation of both the superficial and intermediate layers induced a profound contralateral neglect of the auditory stimulus. Additional and equivalent deactivation of the opposite SC largely restored orienting to either moving visual or auditory stimuli, and restored landmark position reporting to normal levels. However, during bilateral SC deactivation, orienting to the static visual stimulus was abolished throughout the entire visual field. Overall, unilateral SC deactivation results show that the upper and intermediate layers of the SC contribute in different ways to guiding behavioral responses to visual and auditory stimuli cues. Finally, bilateral superior colliculus deactivations reveal that other structures are sufficient to support spatial analyses and guide visual behaviors in the absence of neural operations in the superior colliculus, but only under certain circumstances.
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Affiliation(s)
- S G Lomber
- Laboratory for Visual Perception and Cognition, Department of Anatomy and Neurobiology, Boston University School of Medicine, Boston, MA 02118, USA.
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31
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Hilgetag CC, Théoret H, Pascual-Leone A. Enhanced visual spatial attention ipsilateral to rTMS-induced 'virtual lesions' of human parietal cortex. Nat Neurosci 2001; 4:953-7. [PMID: 11528429 DOI: 10.1038/nn0901-953] [Citation(s) in RCA: 424] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The breakdown of attentional mechanisms after brain damage can have drastic behavioral consequences, as in patients suffering from spatial neglect. While much research has concentrated on impaired attention to targets contralateral to sites of brain damage, here we report the ipsilateral enhancement of visual attention after repetitive transcranial magnetic stimulation (rTMS) of parietal cortex at parameters known to reduce cortical excitability. Normal healthy subjects received rTMS (1 Hz, 10 mins) over right or left parietal cortex. Subsequently, detection of visual stimuli contralateral to the stimulated hemisphere was consistently impaired when stimuli were also present in the opposite hemifield, mirroring the extinction phenomenon commonly observed in neglect patients. Additionally, subjects' attention to ipsilateral targets improved significantly over normal levels. These results underline the potential of focal brain dysfunction to produce behavioral improvement and give experimental support to models of interhemispheric competition in the distributed brain network for spatial attention.
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Affiliation(s)
- C C Hilgetag
- Boston University School of Medicine, Department of Anatomy and Neurobiology, 700 Albany Street W746, Boston, Massachusetts 02118, USA.
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32
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33
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Abstract
Transcranial magnetic stimulation has been used to investigate almost all areas of cognitive neuroscience. This article discusses the most important (and least understood) considerations regarding the use of transcranial magnetic stimulation for cognitive neuroscience and outlines advances in the use of this technique for the replication and extension of findings from neuropsychology. We also take a more speculative look forward to the emerging development of strategies for combining transcranial magnetic stimulation with other brain imaging technologies and methods in the cognitive neurosciences.
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Affiliation(s)
- V Walsh
- Department of Experimental Psychology, University of Oxford, South Parks Road, Oxford, OX1 3UD, UK.
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34
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Young MP, Hilgetag CC, Scannell JW. On imputing function to structure from the behavioural effects of brain lesions. Philos Trans R Soc Lond B Biol Sci 2000; 355:147-61. [PMID: 10703050 PMCID: PMC1692718 DOI: 10.1098/rstb.2000.0555] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
What is the link, if any, between the patterns of connections in the brain and the behavioural effects of localized brain lesions? We explored this question in four related ways. First, we investigated the distribution of activity decrements that followed simulated damage to elements of the thalamocortical network, using integrative mechanisms that have recently been used to successfully relate connection data to information on the spread of activation, and to account simultaneously for a variety of lesion effects. Second, we examined the consequences of the patterns of decrement seen in the simulation for each type of inference that has been employed to impute function to structure on the basis of the effects of brain lesions. Every variety of conventional inference, including double dissociation, readily misattributed function to structure. Third, we tried to derive a more reliable framework of inference for imputing function to structure, by clarifying concepts of function, and exploring a more formal framework, in which knowledge of connectivity is necessary but insufficient, based on concepts capable of mathematical specification. Fourth, we applied this framework to inferences about function relating to a simple network that reproduces intact, lesioned and paradoxically restored orientating behaviour. Lesion effects could be used to recover detailed and reliable information on which structures contributed to particular functions in this simple network. Finally, we explored how the effects of brain lesions and this formal approach could be used in conjunction with information from multiple neuroscience methodologies to develop a practical and reliable approach to inferring the functional roles of brain structures.
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Affiliation(s)
- M P Young
- Department of Psychology, University of Newcastle upon Tyne, UK.
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35
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Young MP, Hilgetag C, Scannell JW. Models of paradoxical lesion effects and rules of inference for imputing function to structure in the brain. Neurocomputing 1999. [DOI: 10.1016/s0925-2312(99)00012-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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