scholarly journals Plasticity, and Its Limits, in Adult Human Primary Visual Cortex

2015 ◽  
Vol 28 (3-4) ◽  
pp. 297-307 ◽  
Author(s):  
Koen V. Haak ◽  
Koen V. Haak ◽  
Antony B. Morland ◽  
Koen V. Haak ◽  
Antony B. Morland ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Primary Visual Cortex ◽  
Neural Plasticity ◽  
Large Scale ◽  
Sampling Bias ◽  
Cortical Reorganization ◽  
Adult Human ◽  
The Face ◽  
New Evidence

There is an ongoing debate about whether adult human primary visual cortex (V1) is capable of large-scale cortical reorganization in response to bilateral retinal lesions. Animal models suggest that the visual neural circuitry maintains some plasticity through adulthood, and there are also a few human imaging studies in support this notion. However, the interpretation of these data has been brought into question, because there are factors besides cortical reorganization, such as the presence of sampling bias and/or the unmasking of task-dependent feedback signals from higher level visual areas, that could also explain the results. How reasonable would it be to accept that adult human V1 does not reorganize itself in the face of disease? Here, we discuss new evidence for the hypothesis that adult human V1 is not as capable of reorganization as in animals and juveniles, because in adult humans, cortical reorganization would come with costs that outweigh its benefits. These costs are likely functional and visible in recent experiments on adaptation — a rapid, short-term form of neural plasticity — where they prevent reorganization from being sustained over the long term.

Thalamic and Cortical Contributions to Neural Plasticity After Limb Amputation

2000 ◽  
Vol 83 (5) ◽  
pp. 3154-3159 ◽  
Author(s):  
S. L. Florence ◽  
T. A. Hackett ◽  
F. Strata
Keyword(s):  
Neural Plasticity ◽  
Large Scale ◽  
Receptive Fields ◽  
Cortical Reorganization ◽  
Limb Amputation ◽  
The Face ◽  
The Relationship ◽  
Area 3B ◽  
Made In ◽  
Stimulation Of

Little is known about the substrates for the large-scale shifts in the cortical representation produced by limb amputation. Subcortical changes likely contribute to the cortical remodeling, yet there is little data regarding the extent and pattern of reorganization in thalamus after such a massive deafferentation. Moreover, the relationship between changes in thalamus and in cortex after injuries of this nature is virtually unexplored. Multiunit microelectrode maps were made in the somatosensory thalamus and cortex of two monkeys that had long-standing, accidental forelimb amputations. In the deprived portion of the ventroposterior nucleus of the thalamus (VP), where stimulation to the hand would normally activate neurons, new receptive fields had emerged. At some recording sites within the deprived zone of VP, neurons responded to stimulation of the remaining stump of the arm and at other sites neurons responded to stimulation of both the stump and the face. This same overall pattern of reorganization was present in the deprived hand representation of cortical area 3b. Thus thalamic changes produced by limb amputation appear to be an important substrate of cortical reorganization. However, a decrease in the frequency of abnormal stump/face fields in area 3b compared with VP and a reduction in the size of the fields suggests that cortical mechanisms of plasticity may refine the information relayed from thalamus.

Planning or Improvisation

2020 ◽  
pp. 116-120
Author(s):  
Alasdair Roberts
Keyword(s):  
United States ◽  
Twentieth Century ◽  
Large Scale ◽  
The United States ◽  
Unintended Consequences ◽  
Governance Strategies ◽  
The Face ◽  
Imperfect Knowledge

This chapter assesses the role of planning in the design of governance strategies. Enthusiasm for large-scale planning—also known as overall, comprehensive, long-term, economic, or social planning—boomed and collapsed in twentieth century. At the start of that century, progressive reformers seized on planning as the remedy for the United States' social and economic woes. By the end of the twentieth century, enthusiasm for large-scale planning had collapsed. Plans could be made, but they were unlikely to be obeyed, and even if they were obeyed, they were unlikely to work as predicted. The chapter then explains that leaders should make plans while being realistic about the limits of planning. It is necessary to exercise foresight, set priorities, and design policies that seem likely to accomplish those priorities. Simply by doing this, leaders encourage coordination among individuals and businesses, through conversation about goals and tactics. Neither is imperfect knowledge a total barrier to planning. There is no “law” of unintended consequences: it is not inevitable that government actions will produce entirely unexpected results. The more appropriate stance is modesty about what is known and what can be achieved. Plans that launch big schemes on brittle assumptions are more likely to fail. Plans that proceed more tentatively, that allow room for testing, learning, and adjustment, are less likely to collapse in the face of unexpected results.

Acupuncture in Neurological Disorders: An Evidence-Based Overview

2020 ◽  
pp. 449-494
Author(s):  
Alexandra Dimitrova
Keyword(s):  
Neurological Disorders ◽  
Large Scale ◽  
Healthcare Providers ◽  
Evidence Based ◽  
Tunnel Syndrome ◽  
Meta Analyses ◽  
New Evidence ◽  
Common Misconceptions

Over the past 20 years acupuncture has been rapidly gaining in popularity both in clinical practice and in research. New evidence for the benefits of acupuncture in various disorders is emerging seemingly every week, and recent large-scale systematic reviews and meta-analyses have suggested that acupuncture’s benefits in pain conditions can be maintained long term. At present the strongest evidence for acupuncture in the treatment of neurological disorders is in the fields of migraine, tension headaches, diabetic neuropathy, carpal tunnel syndrome, and Bell’s palsy. Recent trials suggest that acupuncture may be used as an adjunct in stroke rehabilitation and in improving the quality of life in patients with Parkinson’s disease and dementia. Despite recent mechanistic research advances, much remains unknown about acupuncture’s mechanism of action and there are common misconceptions about the origins of modern-day acupuncture. As acupuncture is being rapidly integrated into mainstream medical practice and increasingly being sought by patients, healthcare providers and neurologists in particular need to be educated about its applications and benefits for various neurological disorders. Our hope is that this chapter will serve toward this educational goal.

scholarly journals Visual epidural field potentials possess high functional specificity in single trials

2019 ◽  
Vol 122 (4) ◽  
pp. 1634-1648 ◽  
Author(s):  
Benjamin Fischer ◽  
Andreas Schander ◽  
Andreas K. Kreiter ◽  
Walter Lang ◽  
Detlef Wegener
Keyword(s):  
Visual Cortex ◽  
Minimally Invasive ◽  
Primary Visual Cortex ◽  
Neuronal Activity ◽  
Large Scale ◽  
Field Potentials ◽  
Operating Characteristics ◽  
Invasive Approach ◽  
Spatial Selectivity ◽  
Minimal Invasiveness

Recordings of epidural field potentials (EFPs) allow neuronal activity to be acquired over a large region of cortical tissue with minimal invasiveness. Because electrodes are placed on top of the dura and do not enter the neuronal tissue, EFPs offer intriguing options for both clinical and basic science research. On the other hand, EFPs represent the integrated activity of larger neuronal populations and possess a higher trial-by-trial variability and a reduced signal-to-noise ratio due the additional barrier of the dura. It is thus unclear whether and to what extent EFPs have sufficient spatial selectivity to allow for conclusions about the underlying functional cortical architecture, and whether single EFP trials provide enough information on the short timescales relevant for many clinical and basic neuroscience purposes. We used the high spatial resolution of primary visual cortex to address these issues and investigated the extent to which very short EFP traces allow reliable decoding of spatial information. We briefly presented different visual objects at one of nine closely adjacent locations and recorded neuronal activity with a high-density epidural multielectrode array in three macaque monkeys. With the use of receiver operating characteristics (ROC) to identify the most informative data, machine-learning algorithms provided close-to-perfect classification rates for all 27 stimulus conditions. A binary classifier applying a simple max function on ROC-selected data further showed that single trials might be classified with 100% performance even without advanced offline classifiers. Thus, although highly variable, EFPs constitute an extremely valuable source of information and offer new perspectives for minimally invasive recording of large-scale networks. NEW & NOTEWORTHY Epidural field potential (EFP) recordings provide a minimally invasive approach to investigate large-scale neural networks, but little is known about whether they possess the required specificity for basic and clinical neuroscience. By making use of the spatial selectivity of primary visual cortex, we show that single-trial information can be decoded with close-to-perfect performance, even without using advanced classifiers and based on very few data. This labels EFPs as a highly attractive and widely usable signal.

scholarly journals How the mechanisms of long-term synaptic potentiation and depression serve experience-dependent plasticity in primary visual cortex

2014 ◽  
Vol 369 (1633) ◽  
pp. 20130284 ◽  
Author(s):  
Sam F. Cooke ◽  
Mark F. Bear
Keyword(s):  
Visual Cortex ◽  
Primary Visual Cortex ◽  
Visual Learning ◽  
Excitatory Input ◽  
Monocular Deprivation ◽  
Hebbian Plasticity ◽  
Circuit Components ◽  
Cortical Synapses ◽  
Visual Cortical

Donald Hebb chose visual learning in primary visual cortex (V1) of the rodent to exemplify his theories of how the brain stores information through long-lasting homosynaptic plasticity. Here, we revisit V1 to consider roles for bidirectional ‘Hebbian’ plasticity in the modification of vision through experience. First, we discuss the consequences of monocular deprivation (MD) in the mouse, which have been studied by many laboratories over many years, and the evidence that synaptic depression of excitatory input from the thalamus is a primary contributor to the loss of visual cortical responsiveness to stimuli viewed through the deprived eye. Second, we describe a less studied, but no less interesting form of plasticity in the visual cortex known as stimulus-selective response potentiation (SRP). SRP results in increases in the response of V1 to a visual stimulus through repeated viewing and bears all the hallmarks of perceptual learning. We describe evidence implicating an important role for potentiation of thalamo-cortical synapses in SRP. In addition, we present new data indicating that there are some features of this form of plasticity that cannot be fully accounted for by such feed-forward Hebbian plasticity, suggesting contributions from intra-cortical circuit components.

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