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Tucciarelli R, Ejaz N, Wesselink DB, Kolli V, Hodgetts CJ, Diedrichsen J, Makin TR. Does Ipsilateral Remapping Following Hand Loss Impact Motor Control of the Intact Hand? J Neurosci 2024; 44:e0948232023. [PMID: 38050100 PMCID: PMC10860625 DOI: 10.1523/jneurosci.0948-23.2023] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2023] [Revised: 10/31/2023] [Accepted: 11/21/2023] [Indexed: 12/06/2023] Open
Abstract
What happens once a cortical territory becomes functionally redundant? We studied changes in brain function and behavior for the remaining hand in humans (male and female) with either a missing hand from birth (one-handers) or due to amputation. Previous studies reported that amputees, but not one-handers, show increased ipsilateral activity in the somatosensory territory of the missing hand (i.e., remapping). We used a complex finger task to explore whether this observed remapping in amputees involves recruiting more neural resources to support the intact hand to meet greater motor control demands. Using basic fMRI analysis, we found that only amputees had more ipsilateral activity when motor demand increased; however, this did not match any noticeable improvement in their behavioral task performance. More advanced multivariate fMRI analyses showed that amputees had stronger and more typical representation-relative to controls' contralateral hand representation-compared with one-handers. This suggests that in amputees, both hand areas work together more collaboratively, potentially reflecting the intact hand's efference copy. One-handers struggled to learn difficult finger configurations, but this did not translate to differences in univariate or multivariate activity relative to controls. Additional white matter analysis provided conclusive evidence that the structural connectivity between the two hand areas did not vary across groups. Together, our results suggest that enhanced activity in the missing hand territory may not reflect intact hand function. Instead, we suggest that plasticity is more restricted than generally assumed and may depend on the availability of homologous pathways acquired early in life.
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Affiliation(s)
- Raffaele Tucciarelli
- MRC Cognition & Brain Sciences Unit, University of Cambridge, Cambridge CB2 7EF, United Kingdom
- Institute of Cognitive Neuroscience, University College London, London WC1N 3AZ, United Kingdom
| | - Naveed Ejaz
- Departments of Statistical and Actuarial Sciences and Computer Science, Western University, London, Ontario N6A 5B7, Canada
| | - Daan B Wesselink
- WIN Centre, Nuffield Department of Clinical Neuroscience, University of Oxford, Oxford OX3 9DU, United Kingdom
- Department of Neurobiology, Harvard Medical School, Boston, Massachusetts 02115
| | - Vijay Kolli
- Queen Mary's Hospital, London SW15 5PN, United Kingdom
| | - Carl J Hodgetts
- CUBRIC, School of Psychology, Cardiff University, Cardiff CF24 4HQ, United Kingdom
- Royal Holloway, University of London, Egham TW20 0EX, United Kingdom
| | - Jörn Diedrichsen
- Departments of Statistical and Actuarial Sciences and Computer Science, Western University, London, Ontario N6A 5B7, Canada
- Brain and Mind Institute, Western University, London, Ontario N6A 3K7, Canada
| | - Tamar R Makin
- MRC Cognition & Brain Sciences Unit, University of Cambridge, Cambridge CB2 7EF, United Kingdom
- Institute of Cognitive Neuroscience, University College London, London WC1N 3AZ, United Kingdom
- WIN Centre, Nuffield Department of Clinical Neuroscience, University of Oxford, Oxford OX3 9DU, United Kingdom
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2
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Abstract
Neurological insults, such as congenital blindness, deafness, amputation, and stroke, often result in surprising and impressive behavioural changes. Cortical reorganisation, which refers to preserved brain tissue taking on a new functional role, is often invoked to account for these behavioural changes. Here, we revisit many of the classical animal and patient cortical remapping studies that spawned this notion of reorganisation. We highlight empirical, methodological, and conceptual problems that call this notion into doubt. We argue that appeal to the idea of reorganisation is attributable in part to the way that cortical maps are empirically derived. Specifically, cortical maps are often defined based on oversimplified assumptions of 'winner-takes-all', which in turn leads to an erroneous interpretation of what it means when these maps appear to change. Conceptually, remapping is interpreted as a circuit receiving novel input and processing it in a way unrelated to its original function. This implies that neurons are either pluripotent enough to change what they are tuned to or that a circuit can change what it computes. Instead of reorganisation, we argue that remapping is more likely to occur due to potentiation of pre-existing architecture that already has the requisite representational and computational capacity pre-injury. This architecture can be facilitated via Hebbian and homeostatic plasticity mechanisms. Crucially, our revised framework proposes that opportunities for functional change are constrained throughout the lifespan by the underlying structural 'blueprint'. At no period, including early in development, does the cortex offer structural opportunities for functional pluripotency. We conclude that reorganisation as a distinct form of cortical plasticity, ubiquitously evoked with words such as 'take-over'' and 'rewiring', does not exist.
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Affiliation(s)
- Tamar R Makin
- MRC Cognition and Brain Sciences Unit, University of CambridgeCambridgeUnited Kingdom
| | - John W Krakauer
- Department of Neuroscience, Johns Hopkins University School of MedicineBaltimoreUnited States
- Department of Neurology, Johns Hopkins University School of MedicineBaltimoreUnited States
- The Santa Fe InstituteSanta FeUnited States
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Sanders Z, Dempsey‐Jones H, Wesselink DB, Edmondson LR, Puckett AM, Saal HP, Makin TR. Similar somatotopy for active and passive digit representation in primary somatosensory cortex. Hum Brain Mapp 2023; 44:3568-3585. [PMID: 37145934 PMCID: PMC10203813 DOI: 10.1002/hbm.26298] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2022] [Revised: 12/11/2022] [Accepted: 03/13/2023] [Indexed: 05/07/2023] Open
Abstract
Scientists traditionally use passive stimulation to examine the organisation of primary somatosensory cortex (SI). However, given the close, bidirectional relationship between the somatosensory and motor systems, active paradigms involving free movement may uncover alternative SI representational motifs. Here, we used 7 Tesla functional magnetic resonance imaging to compare hallmark features of SI digit representation between active and passive tasks which were unmatched on task or stimulus properties. The spatial location of digit maps, somatotopic organisation, and inter-digit representational structure were largely consistent between tasks, indicating representational consistency. We also observed some task differences. The active task produced higher univariate activity and multivariate representational information content (inter-digit distances). The passive task showed a trend towards greater selectivity for digits versus their neighbours. Our findings highlight that, while the gross features of SI functional organisation are task invariant, it is important to also consider motor contributions to digit representation.
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Affiliation(s)
- Zeena‐Britt Sanders
- Wellcome Centre of Integrative NeuroimagingFMRIB, John Radcliffe HospitalOxfordUK
| | - Harriet Dempsey‐Jones
- Institute of Cognitive NeuroscienceUniversity College LondonLondonUK
- School of PsychologyThe University of QueenslandBrisbaneAustralia
| | - Daan B. Wesselink
- Wellcome Centre of Integrative NeuroimagingFMRIB, John Radcliffe HospitalOxfordUK
- Institute of Cognitive NeuroscienceUniversity College LondonLondonUK
| | | | - Alexander M. Puckett
- School of PsychologyThe University of QueenslandBrisbaneAustralia
- Queensland Brain InstituteThe University of QueenslandBrisbaneAustralia
| | - Hannes P. Saal
- Queensland Brain InstituteThe University of QueenslandBrisbaneAustralia
| | - Tamar R. Makin
- Wellcome Centre of Integrative NeuroimagingFMRIB, John Radcliffe HospitalOxfordUK
- Institute of Cognitive NeuroscienceUniversity College LondonLondonUK
- MRC Cognition and Brain Sciences UnitUniversity of CambridgeCambridgeUK
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4
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Wesselink DB, Sanders ZB, Edmondson LR, Dempsey-Jones H, Kieliba P, Kikkert S, Themistocleous AC, Emir U, Diedrichsen J, Saal HP, Makin TR. Malleability of the cortical hand map following a finger nerve block. SCIENCE ADVANCES 2022; 8:eabk2393. [PMID: 35452294 PMCID: PMC9032959 DOI: 10.1126/sciadv.abk2393] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Electrophysiological studies in monkeys show that finger amputation triggers local remapping within the deprived primary somatosensory cortex (S1). Human neuroimaging research, however, shows persistent S1 representation of the missing hand's fingers, even decades after amputation. Here, we explore whether this apparent contradiction stems from underestimating the distributed peripheral and central representation of fingers in the hand map. Using pharmacological single-finger nerve block and 7-tesla neuroimaging, we first replicated previous accounts (electrophysiological and other) of local S1 remapping. Local blocking also triggered activity changes to nonblocked fingers across the entire hand area. Using methods exploiting interfinger representational overlap, however, we also show that the blocked finger representation remained persistent despite input loss. Computational modeling suggests that both local stability and global reorganization are driven by distributed processing underlying the topographic map, combined with homeostatic mechanisms. Our findings reveal complex interfinger representational features that play a key role in brain (re)organization, beyond (re)mapping.
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Affiliation(s)
- Daan B. Wesselink
- Institute of Cognitive Neuroscience, University College London, London, UK
- Wellcome Centre for Integrative Neuroimaging, University of Oxford, Oxford, UK
- Department of Neurobiology, Harvard Medical School, Boston, MA, USA
- Corresponding author.
| | - Zeena-Britt Sanders
- Wellcome Centre for Integrative Neuroimaging, University of Oxford, Oxford, UK
| | - Laura R. Edmondson
- Active Touch Laboratory, Department of Psychology, The University of Sheffield, Sheffield, UK
| | - Harriet Dempsey-Jones
- Institute of Cognitive Neuroscience, University College London, London, UK
- Wellcome Centre for Integrative Neuroimaging, University of Oxford, Oxford, UK
- School of Psychology, University of Queensland, Brisbane, Australia
| | - Paulina Kieliba
- Institute of Cognitive Neuroscience, University College London, London, UK
| | - Sanne Kikkert
- Wellcome Centre for Integrative Neuroimaging, University of Oxford, Oxford, UK
| | - Andreas C. Themistocleous
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
- Brain Function Research Group, University of the Witwatersrand, Johannesburg, South Africa
| | - Uzay Emir
- Wellcome Centre for Integrative Neuroimaging, University of Oxford, Oxford, UK
| | - Jörn Diedrichsen
- Brain and Mind Institute, University of Western Ontario, London, Canada
| | - Hannes P. Saal
- Active Touch Laboratory, Department of Psychology, The University of Sheffield, Sheffield, UK
| | - Tamar R. Makin
- Institute of Cognitive Neuroscience, University College London, London, UK
- Wellcome Centre for Integrative Neuroimaging, University of Oxford, Oxford, UK
- Wellcome Centre for Human Neuroimaging, University College London, London, UK
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5
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Muret D, Root V, Kieliba P, Clode D, Makin TR. Beyond body maps: Information content of specific body parts is distributed across the somatosensory homunculus. Cell Rep 2022; 38:110523. [PMID: 35294887 PMCID: PMC8938902 DOI: 10.1016/j.celrep.2022.110523] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2021] [Revised: 12/10/2021] [Accepted: 02/21/2022] [Indexed: 11/23/2022] Open
Abstract
The homunculus in primary somatosensory cortex (S1) is famous for its body part selectivity, but this dominant feature may eclipse other representational features, e.g., information content, also relevant for S1 organization. Using multivariate fMRI analysis, we ask whether body part information content can be identified in S1 beyond its primary region. Throughout S1, we identify significant representational dissimilarities between body parts but also subparts in distant non-primary regions (e.g., between the hand and the lips in the foot region and between different face parts in the foot region). Two movements performed by one body part (e.g., the hand) could also be dissociated well beyond its primary region (e.g., in the foot and face regions), even within Brodmann area 3b. Our results demonstrate that information content is more distributed across S1 than selectivity maps suggest. This finding reveals underlying information contents in S1 that could be harnessed for rehabilitation and brain-machine interfaces. We replicate the high univariate selectivity profile of the somatosensory homunculus We use multivariate fMRI analysis to identify information content beyond selectivity Significant body part and action-related content are found throughout the homunculus Functional information is available, even in regions selective to other body parts
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Affiliation(s)
- Dollyane Muret
- Institute of Cognitive Neuroscience, University College London, 17 Queen Square, London WC1N 3AZ, UK.
| | - Victoria Root
- Institute of Cognitive Neuroscience, University College London, 17 Queen Square, London WC1N 3AZ, UK; Wellcome Centre of Integrative Neuroimaging, University of Oxford, Oxford OX3 9DU, UK
| | - Paulina Kieliba
- Institute of Cognitive Neuroscience, University College London, 17 Queen Square, London WC1N 3AZ, UK
| | - Danielle Clode
- Institute of Cognitive Neuroscience, University College London, 17 Queen Square, London WC1N 3AZ, UK; Dani Clode Design, 40 Hillside Road, London SW2 3HW, UK
| | - Tamar R Makin
- Institute of Cognitive Neuroscience, University College London, 17 Queen Square, London WC1N 3AZ, UK; Wellcome Trust Centre for Neuroimaging, University College London, London WC1N 3AR, UK
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Amoruso E, Dowdall L, Kollamkulam MT, Ukaegbu O, Kieliba P, Ng T, Dempsey-Jones H, Clode D, Makin TR. Intrinsic somatosensory feedback supports motor control and learning to operate artificial body parts. J Neural Eng 2022; 19:016006. [PMID: 34983040 PMCID: PMC10431236 DOI: 10.1088/1741-2552/ac47d9] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2021] [Revised: 12/09/2021] [Accepted: 01/04/2022] [Indexed: 11/11/2022]
Abstract
Objective.Considerable resources are being invested to enhance the control and usability of artificial limbs through the delivery of unnatural forms of somatosensory feedback. Here, we investigated whether intrinsic somatosensory information from the body part(s) remotely controlling an artificial limb can be leveraged by the motor system to support control and skill learning.Approach.We used local anaesthetic to attenuate somatosensory inputs to the big toes while participants learned to operate through pressure sensors a toe-controlled and hand-worn robotic extra finger. Motor learning outcomes were compared against a control group who received sham anaesthetic and quantified in three different task scenarios: while operating in isolation from, in synchronous coordination, and collaboration with, the biological fingers.Main results.Both groups were able to learn to operate the robotic extra finger, presumably due to abundance of visual feedback and other relevant sensory cues. Importantly, the availability of displaced somatosensory cues from the distal bodily controllers facilitated the acquisition of isolated robotic finger movements, the retention and transfer of synchronous hand-robot coordination skills, and performance under cognitive load. Motor performance was not impaired by toes anaesthesia when tasks involved close collaboration with the biological fingers, indicating that the motor system can close the sensory feedback gap by dynamically integrating task-intrinsic somatosensory signals from multiple, and even distal, body-parts.Significance.Together, our findings demonstrate that there are multiple natural avenues to provide intrinsic surrogate somatosensory information to support motor control of an artificial body part, beyond artificial stimulation.
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Affiliation(s)
- E Amoruso
- Institute of Cognitive Neuroscience, University College London, London, United Kingdom
| | - L Dowdall
- Institute of Cognitive Neuroscience, University College London, London, United Kingdom
| | - M T Kollamkulam
- Institute of Cognitive Neuroscience, University College London, London, United Kingdom
| | - O Ukaegbu
- Institute of Cognitive Neuroscience, University College London, London, United Kingdom
- East London NHS Foundation Trust, London, United Kingdom
| | - P Kieliba
- Institute of Cognitive Neuroscience, University College London, London, United Kingdom
| | - T Ng
- Royal Free London NHS Foundation Trust, London, United Kingdom
| | - H Dempsey-Jones
- Institute of Cognitive Neuroscience, University College London, London, United Kingdom
| | - D Clode
- Institute of Cognitive Neuroscience, University College London, London, United Kingdom
| | - T R Makin
- Institute of Cognitive Neuroscience, University College London, London, United Kingdom
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7
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Maimon-Mor RO, Schone HR, Henderson Slater D, Faisal AA, Makin TR. Early life experience sets hard limits on motor learning as evidenced from artificial arm use. eLife 2021; 10:66320. [PMID: 34605407 PMCID: PMC8523152 DOI: 10.7554/elife.66320] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2021] [Accepted: 10/01/2021] [Indexed: 11/13/2022] Open
Abstract
The study of artificial arms provides a unique opportunity to address long-standing questions on sensorimotor plasticity and development. Learning to use an artificial arm arguably depends on fundamental building blocks of body representation and would therefore be impacted by early life experience. We tested artificial arm motor-control in two adult populations with upper-limb deficiencies: a congenital group—individuals who were born with a partial arm, and an acquired group—who lost their arm following amputation in adulthood. Brain plasticity research teaches us that the earlier we train to acquire new skills (or use a new technology) the better we benefit from this practice as adults. Instead, we found that although the congenital group started using an artificial arm as toddlers, they produced increased error noise and directional errors when reaching to visual targets, relative to the acquired group who performed similarly to controls. However, the earlier an individual with a congenital limb difference was fitted with an artificial arm, the better their motor control was. Since we found no group differences when reaching without visual feedback, we suggest that the ability to perform efficient visual-based corrective movements is highly dependent on either biological or artificial arm experience at a very young age. Subsequently, opportunities for sensorimotor plasticity become more limited.
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Affiliation(s)
- Roni O Maimon-Mor
- WIN Centre, Nuffield Department of Clinical Neuroscience, University of Oxford, Oxford, United Kingdom.,Institute of Cognitive Neuroscience, University College London, London, United Kingdom
| | - Hunter R Schone
- Institute of Cognitive Neuroscience, University College London, London, United Kingdom.,Laboratory of Brain & Cognition, NIMH, National Institutes of Health, Bethesda, United States
| | | | - A Aldo Faisal
- Departments of Bioengineering and of Computing, Imperial College London, London, United Kingdom
| | - Tamar R Makin
- Institute of Cognitive Neuroscience, University College London, London, United Kingdom
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Ravikanth D, Hariharan P. Psychophysics Experiment to Check the Temperature Impacts Over Human Fingertips for the Application of Textural Applications in Haptics Technology. ARABIAN JOURNAL FOR SCIENCE AND ENGINEERING 2021. [DOI: 10.1007/s13369-021-05334-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
AbstractPsychophysical methods in haptic technology help in comparative study and eventually be a data set to achieve realism over skin sensation. Textural based haptic applications are widely developed using tactile displays over human fingertips. The tactile displays work on open-loop admittance feedback system and are controlled with flexible parameters by ignoring the impact of noise or disturbance variables. Human skin undergoes various noise factors like temperature, humidity, sweat, and influence of alternative senses. This paper presents the newly adopted method of psychophysics to study the influence of environmental conditions over perceiving textural surfaces. The paper adopts the detection mode of psychophysics which uses perception time as an output parameter for understanding perception memory of the human skin. We have recorded the period of the perception in three environmental conditions over human subjects under a single blindfold method to study the behaviour of human skin at fingertips. The perception time of stimulus is analysed with arithmetic average roughness value (Ra) to understand the tolerance factor required during tactile based textural applications. The proposed method is simple to structure and improves in creating the dataset required to consider the noise factor for an open-loop admission feedback system.
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Dempsey-Jones H, Steudte-Schmiedgen S, Browning M, Makin TR, Woud ML, Harmer CJ, Margraf J, Reinecke A. Human perceptual learning is delayed by the N-methyl-D-aspartate receptor partial agonist D-cycloserine. J Psychopharmacol 2021; 35:253-264. [PMID: 33570017 PMCID: PMC7924109 DOI: 10.1177/0269881120986349] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
BACKGROUND The optimisation of learning has long been a focus of scientific research, particularly in relation to improving psychological treatment and recovery of brain function. Previously, partial N-methyl-D-aspartate agonists have been shown to augment reward learning, procedural learning and psychological therapy, but many studies also report no impact of these compounds on the same processes. AIMS Here we investigate whether administration of an N-methyl-D-aspartate partial agonist (D-cycloserine) modulates a previously unexplored process - tactile perceptual learning. Further, we use a longitudinal design to investigate whether N-methyl-D-aspartate-related learning effects vary with time, thereby providing a potentially simple explanation for apparent mixed effects in previous research. METHODS Thirty-four volunteers were randomised to receive one dose of 250 mg D-cycloserine or placebo 2 h before tactile sensitivity training. Tactile perception was measured using psychophysical methods before and after training, and 24/48 h later. RESULTS The placebo group showed immediate within-day tactile perception gains, but no further improvements between-days. In contrast, tactile perception remained at baseline on day one in the D-cycloserine group (no within-day learning), but showed significant overnight gains on day two. Both groups were equivalent in tactile perception by the final testing - indicating N-methyl-D-aspartate effects changed the timing, but not the overall amount of tactile learning. CONCLUSIONS In sum, we provide first evidence for modulation of perceptual learning by administration of a partial N-methyl-D-aspartate agonist. Resolving how the effects of such compounds become apparent over time will assist the optimisation of testing schedules, and may help resolve discrepancies across the learning and cognition domains.
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Affiliation(s)
- Harriet Dempsey-Jones
- Wellcome Centre for Integrated Neuroimaging, University of Oxford, Oxford, UK
- School of Psychology, University of Queensland, Brisbane, Australia
| | - Susann Steudte-Schmiedgen
- Department of Psychotherapy and Psychosomatic Medicine, Technische Universität Dresden, Dresden, Germany
| | - Michael Browning
- Department of Psychiatry, University of Oxford, Oxford, UK
- Oxford Health NHS Foundation Trust, Oxford, UK
| | - Tamar R Makin
- Wellcome Centre for Integrated Neuroimaging, University of Oxford, Oxford, UK
- Institute of Cognitive Neuroscience, University College London, London, UK
| | - Marcella L Woud
- Department of Clinical Psychology and Psychotherapy, Ruhr-University Bochum, Bochum, Germany
| | - Catherine J Harmer
- Department of Psychiatry, University of Oxford, Oxford, UK
- Oxford Health NHS Foundation Trust, Oxford, UK
| | - Juergen Margraf
- Department of Clinical Psychology and Psychotherapy, Ruhr-University Bochum, Bochum, Germany
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Dempsey-Jones H, Wesselink DB, Friedman J, Makin TR. Organized Toe Maps in Extreme Foot Users. Cell Rep 2020; 28:2748-2756.e4. [PMID: 31509738 PMCID: PMC6899508 DOI: 10.1016/j.celrep.2019.08.027] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2018] [Revised: 03/28/2019] [Accepted: 08/05/2019] [Indexed: 12/11/2022] Open
Abstract
Although the fine-grained features of topographic maps in the somatosensory cortex can be shaped by everyday experience, it is unknown whether behavior can support the expression of somatotopic maps where they do not typically occur. Unlike the fingers, represented in all primates, individuated toe maps have only been found in non-human primates. Using 1-mm resolution fMRI, we identify organized toe maps in two individuals born without either upper limb who use their feet to substitute missing hand function and even support their profession as foot artists. We demonstrate that the ordering and structure of the artists’ toe representation mimics typical hand representation. We further reveal “hand-like” features of activity patterns, not only in the foot area but also similarly in the missing hand area. We suggest humans may have an innate capacity for forming additional topographic maps that can be expressed with appropriate experience. We ask if extreme behavior can cause the (re)emergence of somatotopic maps We investigated two foot artists, born without arms 7T fMRI shows individuated maps of up to 5 toes in the artists but not controls Activity in artists’ foot and hand areas was more “hand-like” than in controls
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Affiliation(s)
| | - Daan B Wesselink
- Institute of Cognitive Neuroscience, University College London, London WC1N 3AZ, UK; Wellcome Centre for Integrative Neuroimaging, University of Oxford, Oxford OX3 9DU, UK.
| | - Jason Friedman
- Physical Therapy Department, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv 699 7801, Israel; Sagol School of Neuroscience, Tel Aviv University, Tel Aviv 699 7801, Israel
| | - Tamar R Makin
- Institute of Cognitive Neuroscience, University College London, London WC1N 3AZ, UK
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11
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Makin TR, Flor H. Brain (re)organisation following amputation: Implications for phantom limb pain. Neuroimage 2020; 218:116943. [PMID: 32428706 PMCID: PMC7422832 DOI: 10.1016/j.neuroimage.2020.116943] [Citation(s) in RCA: 65] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2019] [Revised: 05/10/2020] [Accepted: 05/11/2020] [Indexed: 12/11/2022] Open
Abstract
Following arm amputation the region that represented the missing hand in primary somatosensory cortex (S1) becomes deprived of its primary input, resulting in changed boundaries of the S1 body map. This remapping process has been termed 'reorganisation' and has been attributed to multiple mechanisms, including increased expression of previously masked inputs. In a maladaptive plasticity model, such reorganisation has been associated with phantom limb pain (PLP). Brain activity associated with phantom hand movements is also correlated with PLP, suggesting that preserved limb functional representation may serve as a complementary process. Here we review some of the most recent evidence for the potential drivers and consequences of brain (re)organisation following amputation, based on human neuroimaging. We emphasise other perceptual and behavioural factors consequential to arm amputation, such as non-painful phantom sensations, perceived limb ownership, intact hand compensatory behaviour or prosthesis use, which have also been related to both cortical changes and PLP. We also discuss new findings based on interventions designed to alter the brain representation of the phantom limb, including augmented/virtual reality applications and brain computer interfaces. These studies point to a close interaction of sensory changes and alterations in brain regions involved in body representation, pain processing and motor control. Finally, we review recent evidence based on methodological advances such as high field neuroimaging and multivariate techniques that provide new opportunities to interrogate somatosensory representations in the missing hand cortical territory. Collectively, this research highlights the need to consider potential contributions of additional brain mechanisms, beyond S1 remapping, and the dynamic interplay of contextual factors with brain changes for understanding and alleviating PLP.
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Affiliation(s)
- Tamar R Makin
- Institute of Cognitive Neuroscience, University College London, London, United Kingdom; Wellcome Centre for Human Neuroimaging, University College London, London, UK.
| | - Herta Flor
- Institute of Cognitive and Clinical Neuroscience, Central Institute of Mental Health, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany; Department of Psychology, School of Social Sciences, University of Mannheim, Germany; Center for Neuroplasticity and Pain (CNAP), Department of Health Science and Technology, Aalborg University, Aalborg, Denmark
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12
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Remapping in Cerebral and Cerebellar Cortices Is Not Restricted by Somatotopy. J Neurosci 2019; 39:9328-9342. [PMID: 31611305 PMCID: PMC6867820 DOI: 10.1523/jneurosci.2599-18.2019] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2018] [Revised: 07/16/2019] [Accepted: 08/05/2019] [Indexed: 12/27/2022] Open
Abstract
A fundamental organizing principle in the somatosensory and motor systems is somatotopy, where specific body parts are represented separately and adjacently to other body parts, resulting in a body map. Different terminals of the sensorimotor network show varied somatotopic layouts, in which the relative position, distance, and overlap between body-part representations differ. Since somatotopy is best characterized in the primary somatosensory (S1) and motor (M1) cortices, these terminals have been the main focus of research on somatotopic remapping following loss of sensory input (e.g., arm amputation). Cortical remapping is generally considered to be driven by the layout of the underlying somatotopy, such that neighboring body-part representations tend to activate the deprived brain region. Here, we challenge the assumption that somatotopic layout restricts remapping, by comparing patterns of remapping in humans born without one hand (hereafter, one-handers, n = 26) across multiple terminals of the sensorimotor pathway. We first report that, in the cerebellum of one-handers, the deprived hand region represents multiple body parts. Importantly, the native representations of some of these body parts do not neighbor the deprived hand region. We further replicate our previous findings, showing a similar pattern of remapping in the deprived hand region of the cerebral cortex in one-handers. Finally, we report preliminary results of a similar remapping pattern in the putamen of one-handers. Since these three sensorimotor terminals (cerebellum, cerebrum, putamen) contain different somatotopic layouts, the parallel remapping they undergo demonstrates that the mere spatial layout of body-part representations may not exclusively dictate remapping in the sensorimotor systems. SIGNIFICANCE STATEMENT When a hand is missing, the brain region that typically processes information from that hand may instead process information from other body parts, a phenomenon termed remapping. It is commonly thought that only body parts whose information is processed in regions neighboring the hand region could “take up” the resources of this now deprived region. Here we demonstrate that information from multiple body parts is processed in the hand regions of both the cerebral cortex and cerebellum. The native brain regions of these body parts have varying levels of overlap with the hand regions of the cerebral cortex and cerebellum, and do not necessarily neighbor the hand regions. We therefore propose that proximity between brain regions does not limit brain remapping.
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