Plasticity Of Cortical Representations Research Articles

Sally’s Phantom: A Case Study on Plasticity of Cortical Representation

Sally’s Phantom: A Case Study on Plasticity of Cortical Representation

Disparity among muscles: different levels of plasticity of cortical representation of different muscles revealed by transcranial magnetic stimulation.

Disparity among muscles: different levels of plasticity of cortical representation of different muscles revealed by transcranial magnetic stimulation.

Synaptic Neuronal Plasticity

Context: The current study aimed to review research articles concerning cortical representational plasticity following the manipulations of inputs. Evidence Acquisition: This review article compromised previous studies in PubMed, Google Scholar and Scientific Information databases according to the keywords since 1988. Results: CA1 neurons depolarization paired with CA3 presynaptic input result in EPSPs amplitude enhancement called LTP. Theta-burst stimulation of layer IV produced long term potentiation (LTP) in the granular primary motor cortex, but the agranular or primary somatosensory cortex was capable of generating LTP in case of GABAA receptor inhibition. Upper layers (UL)-induced, and White Matter WM-induced plasticity in layer VI corticogeniculate neurons were produced through type-5 metabotropic glutamate and N-methyl-D-aspartate (NMDA) receptors, respectively. Calcineurin and cannabinoid type 1 receptors are involved in WM-induced and UL-induced het-LTD, respectively. Long-term potentiation of inhibitory postsynaptic currents (IPSCs) was produced in FS-GABA neurons in layer II/III of the mouse visual cortex by tetanic activation. Conclusions: In summary, the current study presents rational evidences for specific fundamental forms of plasticity, containing associative long-term potentiation and depression of excitatory and inhibitory postsynaptic potentials.

Experience‐dependent brain plasticity after stroke: effect of ibuprofen and poststroke delay

Despite indications that brain plasticity may be enhanced after stroke, we have described impairment of experience-dependent plasticity in rat cerebral cortex neighboring the stroke-induced lesion. Photothrombotic stroke was centered behind the barrel cortex in one cerebral hemisphere of rats. Plasticity of cortical representation of one row of vibrissae was induced by sensory deprivation of all surrounding whiskers for 1 month, and visualized with [(14)C]-2-deoxyglucose autoradiography. In control rats deprivation resulted in an enlargement of functional cortical representation of the spared row of vibrissae. After a focal stroke neighbouring the barrel cortex, no plasticity of the spared row representation was found. Investigation of plastic changes with deprivation initiated 1 week and 1 month after stroke have shown that later poststroke onset of deprivation resulted in a partial recovery of cortical plasticity in the barrel field. Western blot analysis of proinflammatory enzyme cyclooxygenase-2 (COX-2) expression revealed its strong upregulation in the barrel cortex 24 h after stroke. When chronic treatment with the anti-inflammatory drug ibuprofen (10 mg/kg or 20 mg/kg) accompanied deprivation, plasticity was restored. Ibuprofen applied before the ischemia also prevented the poststroke upregulation of COX-2. The results strongly suggest that poststroke impairment of experience-dependent cortical plasticity is caused by stroke-induced inflammatory reactions that subside with poststroke delay and can be at least partially ameliorated by pharmacological treatment.

Learning-induced plasticity of cortical representations does not affect GAD65 mRNA expression and immunolabeling of cortical neuropil

Two forms of glutamic acid decarboxylase (GAD) are present in inhibitory neurons of the mammalian brain, a 65-kDa isoform (GAD65) and a 67-kDa isoform (GAD67). We have previously found that GAD67 is upregulated during learning-dependent plasticity of cortical vibrissal representations of adult mice. After sensory conditioning involving pairing stimulation of vibrissae with a tail shock, the increase in mRNA expression and density of GAD67-immunoreactive neurons was observed in barrels representing vibrissae activated during the training. In the present study, using the same experimental model, we examined GAD65 mRNA and protein levels in the barrel cortex. For this purpose, we used in situ hybridization and immunohistochemistry. No changes in the level of GAD65 mRNA expression were detected after the training. The pattern of GAD65 mRNA expression was complementary to that observed for GAD67. Immunocytochemical analysis found no changes in immunolabeling of neuropil of the barrels representing the vibrissae activated during the training. The results show that, in contrast to GAD67, cortical plasticity induced by sensory learning does not affect the expression of GAD65.

Functional reorganization of visual cortex maps after ischemic lesions is accompanied by changes in expression of cytoskeletal proteins and NMDA and GABA(A) receptor subunits.

Reorganization of cortical representations after focal visual cortex lesions has been documented. It has been suggested that functional reorganization may rely on cellular mechanisms involving modifications in the excitatory/inhibitory neurotransmission balance and on morphological changes of neurons peripheral to the lesion. We explored functional reorganization of cortical retinotopic maps after a focal ischemic lesion in primary visual cortex of kittens using optical imaging of intrinsic signals. After 1, 2, and 5 weeks postlesion (wPL), we addressed whether functional reorganization correlated in time with changes in the expression of MAP-2, GAP-43, GFAP, GABA(A) receptor subunit alpha1 (GABA(A)alpha1), subunit 1 of the NMDA receptor (NMDAR1), and in neurotransmitter levels at the border of the lesion. Our results show that: (1) retinotopic maps reorganize with time after an ischemic lesion; (2) MAP-2 levels increase gradually from 1wPL to 5wPL; (3) MAP-2 upregulation is associated with an increase in dendritic-like structures surrounding the lesion and a decrease in GFAP-positive cells; (4) GAP-43 levels reach the highest point at 2wPL; (5) NMDAR1 and glutamate contents increase in parallel from 1wPL to 5wPL; (6) GABA(A)alpha1 levels increase from 1wPL to 2wPL but do not change after this time point; and (7) GABA contents remain low from 1wPL to 5wPL. This is a comprehensive study showing for the first time that functional reorganization correlates in time with dendritic sprouting and with changes in the excitatory/inhibitory neurotransmission systems previously proposed to participate in cortical remodeling and suggests mechanisms by which plasticity of cortical representations may occur.

Lesions of the Basal Forebrain Cholinergic System Impair Task Acquisition and Abolish Cortical Plasticity Associated with Motor Skill Learning

The contribution of the basal forebrain cholinergic system in mediating plasticity of cortical sensorimotor representations was examined in the context of normal learning. The effects of specific basal forebrain cholinergic lesions upon cortical reorganization associated with learning a skilled motor task were investigated, addressing, for the first time, the functional consequences of blocking cortical map plasticity. Results demonstrate that disrupting basal forebrain cholinergic function disrupts cortical map reorganization and impairs motor learning. Cholinergic lesions do not impair associative fear learning or overall sensorimotor function. These results support the hypothesis that the basal forebrain cholinergic system may be specifically implicated in forms of learning requiring plasticity of cortical representations.

Delayed upregulation of GABA A alpha1 receptor subunit mRNA in somatosensory cortex of mice following learning-dependent plasticity of cortical representations

Experience-dependent modifications of cortical representational maps are accompanied by changes in several components of GABAergic inhibitory neurotransmission system. We examined with in situ hybridization to 35S-labeled oligoprobe changes of expression of GABA A receptor alpha1 subunit mRNA in the barrel cortex of mice after sensory conditioning training. One day and 5 days after the end of short lasting (3 daily sessions) training an increased expression of GABA A alpha1 mRNA was observed at the cortical site where the plastic changes were previously found. Learning associated activation of the cerebral cortex increases expression of GABA A receptor mRNA after a short post-training delays.

The Cortical Representation of the Hand in Macaque and Human Area S-I: High Resolution Optical Imaging

High-resolution images of the somatotopic hand representation in macaque monkey primary somatosensory cortex (area S-I) were obtained by optical imaging based on intrinsic signals. To visualize somatotopic maps, we imaged optical responses to mild tactile stimulation of each individual fingertip. The activation evoked by stimulation of a single finger was strongest in a narrow transverse band ( approximately 1 x 4 mm) across the postcentral gyrus. As expected, a sequential organization of these bands was found. However, a significant overlap, especially for the activated areas of fingers 3-5, was found. Surprisingly, in addition to the finger-specific domains, we found that for each of the fingers, weak stimulation activated also a second "common patch" of cortex, located just medially to the representation of the finger. These results were confirmed by targeted multiunit and single-unit recordings guided by the optical maps. The maps remained very stable over many hours of recording. By optimizing the imaging procedures, we were able to obtain the functional maps extremely rapidly (e.g., the map of five fingers in the macaque monkey could be obtained in as little as 5 min). Furthermore, we describe the intraoperative optical imaging of the hand representation in the human brain during neurosurgery and then discuss the implications of the present results for the spatial resolution accomplishable by other neuroimaging techniques, relying on responses of the microcirculation to sensory-evoked electrical activity. This study demonstrates the feasibility of using high-resolution optical imaging to explore reliably short- and long-term plasticity of cortical representations, as well as for applications in the clinical setting.

Cortical plasticity: from synapses to maps.

It has been clear for almost two decades that cortical representations in adult animals are not fixed entities, but rather, are dynamic and are continuously modified by experience. The cortex can preferentially allocate area to represent the particular peripheral input sources that are proportionally most used. Alterations in cortical representations appear to underlie learning tasks dependent on the use of the behaviorally important peripheral inputs that they represent. The rules governing this cortical representational plasticity following manipulations of inputs, including learning, are increasingly well understood. In parallel with developments in the field of cortical map plasticity, studies of synaptic plasticity have characterized specific elementary forms of plasticity, including associative long-term potentiation and long-term depression of excitatory postsynaptic potentials. Investigators have made many important strides toward understanding the molecular underpinnings of these fundamental plasticity processes and toward defining the learning rules that govern their induction. The fields of cortical synaptic plasticity and cortical map plasticity have been implicitly linked by the hypothesis that synaptic plasticity underlies cortical map reorganization. Recent experimental and theoretical work has provided increasingly stronger support for this hypothesis. The goal of the current paper is to review the fields of both synaptic and cortical map plasticity with an emphasis on the work that attempts to unite both fields. A second objective is to highlight the gaps in our understanding of synaptic and cellular mechanisms underlying cortical representational plasticity.

Rapidly induced auditory plasticity: the ventriloquism aftereffect.

Cortical representational plasticity has been well documented after peripheral and central injuries or improvements in perceptual and motor abilities. This has led to inferences that the changes in cortical representations parallel and account for the improvement in performance during the period of skill acquisition. There have also been several examples of rapidly induced changes in cortical neuronal response properties, for example, by intracortical microstimulation or by classical conditioning paradigms. This report describes similar rapidly induced changes in a cortically mediated perception in human subjects, the ventriloquism aftereffect, which presumably reflects a corresponding change in the cortical representation of acoustic space. The ventriloquism aftereffect describes an enduring shift in the perception of the spatial location of acoustic stimuli after a period of exposure of spatially disparate and simultaneously presented acoustic and visual stimuli. Exposure of a mismatch of 8 degrees for 20-30 min is sufficient to shift the perception of acoustic space by approximately the same amount across subjects and acoustic frequencies. Given that the cerebral cortex is necessary for the perception of acoustic space, it is likely that the ventriloquism aftereffect reflects a change in the cortical representation of acoustic space. Comparisons between the responses of single cortical neurons in the behaving macaque monkey and the stimulus parameters that give rise to the ventriloquism aftereffect suggest that the changes in the cortical representation of acoustic space may begin as early as the primary auditory cortex.

Synaptic mechanisms of cortical representational plasticity: somatosensory and corticocortical EPSPs in reorganized raccoon SI cortex.

1. Reorganizations of representational maps have been described for a variety of sensory and motor regions of cerebral neocortex in several species. The purpose of this study was to investigate synaptic mechanisms of the reorganizations of primary somatosensory cortex that follow removal of a digit or the joining of two digits into a syndactyly. We examined neurons in the cortical representation of digit 4 (d4). Intracellular recording was used to compare somatosensory and corticocortical excitatory postsynaptic potentials (EPSPs) in normal raccoons, with EPSPs recorded in two experimental groups of animals surviving for a mean of 22 wk after removal of d4, or union of d4 with digit 3 (d3). 2. In normal animals with d4 intact, EPSPs were evoked from this on-focus digit in 100% of cortical neurons. EPSPs were evoked from d3 and digit 5 (off-focus digits) in only a minority of neurons in normal raccoons. The incidence of somatosensory EPSPs from off-focus digits increased dramatically after removal of d4 or its union with d3. Latencies of EPSPs evoked from off-focus digits decreased after d4 removal, so that they were as short as latencies from d4 in normal animals. In contrast, for the group of animals with d3-d4 syndactyly, latencies of EPSPs from off-focus digits were not shorter than responses from these digits in normal animals. 3. Corticocortical EPSPs were no more common in animals with d4 removed than in intact animals. Furthermore, corticocortical EPSPs after d4 removal did not differ in their latencies, amplitudes, half-widths, or integrated amplitudes. The only detected change was that corticocortical EPSPs had faster rising phases after removal of d4. In contrast, after d3-d4 syndactyly, corticocortical EPSPs were more common than in normal animals. 4. Digit removal and digital syndactyly had distinctive effects on somatosensory and corticocortical EPSPs. These results do not identify unique synaptic mechanisms for cortical representational plasticity, nor do they specify the involved CNS site(s). Several synaptic mechanisms consistent with the results are considered in the DISCUSSION, including synaptic proliferation to form new synaptic connections and enhanced effectiveness of existing corticocortical synapses.

TOPOGRAPHICAL REPRESENTATION OF MUSCLES IN MOTOR CORTEX OF MONKEYS

ArticlesTOPOGRAPHICAL REPRESENTATION OF MUSCLES IN MOTOR CORTEX OF MONKEYSHsiang-Tung Chang, Theodore C. Ruch, and Arthur A. Ward JR.Hsiang-Tung Chang, Theodore C. Ruch, and Arthur A. Ward JR.Published Online:01 Jan 1947https://doi.org/10.1152/jn.1947.10.1.39MoreSectionsPDF (2 MB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat Previous Back to Top Next Download PDF FiguresReferencesRelatedInformation Cited ByNeural Representations Observed24 February 2018 | Minds and Machines, Vol. 28, No. 1Individual Variation in Human Motor-Sensory (Rolandic) CortexJournal of Clinical Neurophysiology, Vol. 24, No. 3Chapter 2 Comparative anatomy and physiology of the corticospinal systemElectrophysiological Methods for Mapping Brain Motor and Sensory CircuitsConstraints on Somatotopic Organization in the Primary Motor CortexMarc H. Schieber1 November 2001 | Journal of Neurophysiology, Vol. 86, No. 5Hsiang-Tung ChangEffect of antagonistic voluntary contraction on motor responses in the forearmClinical Neurophysiology, Vol. 111, No. 6Arthur Allen Ward, Jr., M.D. 1916-1997Epilepsia, Vol. 39, No. 5Functional plasticity of cortical representations of the handFunctional Architecture of Cortical Networks Underlying Visual ReachingChapter 4 Neuronal Substrate for Volitional MovementArchitectionis, somatotopic organization, and ipsilateral cortical connections of the primary motor area (M1) of owl monkeysThe Journal of Comparative Neurology, Vol. 330, No. 2A cortical slow potential is larger before an isolated movement of a single finger than simultaneous movement of two fingersElectroencephalography and Clinical Neurophysiology, Vol. 86, No. 4Modification of Cortical Stimulation for Motor Evoked Potentials under General AnesthesiaNeurosurgery, Vol. 32, No. 2Modification of Cortical Stimulation for Motor Evoked Potentials under General AnesthesiaNeurosurgery, Vol. 32, No. 2Noninvasive mapping of muscle representations in human motor cortexElectroencephalography and Clinical Neurophysiology/Evoked Potentials Section, Vol. 85, No. 1Organization and Adaptability of Muscle Representations in Primary Motor CortexNon-Invasive Mapping of the Human Motor Cortex with PETReviews in the Neurosciences, Vol. 3, No. 3Latency of motor evoked potentials to focal transcranial stimulation varies as a function of scalp positions stimulatedElectroencephalography and Clinical Neurophysiology/Evoked Potentials Section, Vol. 81, No. 2Chapter 11 Neural mechanisms underlying corticospinal and rubrospinal control of limb movementsThe relationship of corpus callosum connections to electrical stimulation maps of motor, supplementary motor, and the frontal eye fields in owl monkeysThe Journal of Comparative Neurology, Vol. 247, No. 3Nervous propagation along ‘central’ motor pathways in intact man: Characteristics of motor responses to ‘bifocal’ and ‘unifocal’ spine and scalp non-invasive stimulationElectroencephalography and Clinical Neurophysiology, Vol. 61, No. 4Chapter IIa Frequency Encoding in Motor SystemsElectrical Activity of the BrainThe Pyramidal Tract1 January 2011The Pyramidal TractMotor FunctionBiofeedback and Differential Conditioning of Response Patterns in the Skeletal Motor SystemSelective adaptation of “command neurons” in the human motor systemNeuropsychologia, Vol. 15, No. 1Mind, It Does MatterLaying the Ghost of ‘Muscles Versus Movements’18 September 2015 | Canadian Journal of Neurological Sciences / Journal Canadien des Sciences Neurologiques, Vol. 2, No. 3Functions of the mammalian cerebral cortex in movementProgress in Neurobiology, Vol. 1THE CONTROL OF MUSCULAR ACTIVITY BY THE CENTRAL NERVOUS SYSTEMPatterns of contraction of distal forelimb muscles produced by intracortical stimulation in catsBrain Research, Vol. 27, No. 1Beginnings of the Nervous SystemThe Response of the Vocal Folds to Electrical Stimulation of the Inferior Frontal Cortex of the Squirrel Monkey8 July 2009 | Acta Oto-Laryngologica, Vol. 61, No. 1-6Changing Concepts of the Precentral Motor AreaLXXXI Cortical Motor Centers of the Laryngeal Muscles in the Cat and Dog29 June 2016 | Annals of Otology, Rhinology & Laryngology, Vol. 73, No. 4Free Behavior and Brain StimulationXX An Experimental Study of Central Motor Innervation of the Laryngeal Muscles in the Cat28 June 2016 | Annals of Otology, Rhinology & Laryngology, Vol. 71, No. 1SECTION OF BIOLOGICAL AND MEDICAL SCIENCES: CONTRAST AND STABILITY IN THE NERVOUS SYSTEM*30 April 2012 | Transactions of the New York Academy of Sciences, Vol. 21, No. 5 Series IIDiscussion on the Differential Diagnosis of Lesions of the Posterior Fossa1 September 2016 | Proceedings of the Royal Society of Medicine, Vol. 46, No. 9Der intraspinale Verlauf und die Endigungen der sensorischen Wurzeln in den Nucleus Gracilis und CuneatusArchiv f�r Psychiatrie und Nervenkrankheiten Vereinigt mit Zeitschrift f�r die Gesamte Neurologie und Psychiatrie, Vol. 187, No. 3Biophysical Aspects of Nervous FunctionProgress in Biophysics and Biophysical Chemistry, Vol. 2Neurophysiology, 1942–1948New England Journal of Medicine, Vol. 240, No. 23NeurologyNew England Journal of Medicine, Vol. 237, No. 17 More from this issue > Volume 10Issue 1January 1947Pages 39-56 https://doi.org/10.1152/jn.1947.10.1.39PubMed20279138History Published online 1 January 1947 Published in print 1 January 1947 Metrics