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.

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.

Serial and parallel processing of tactual information in somatosensory cortex of rhesus monkeys

1992 ◽  
Vol 68 (2) ◽  
pp. 518-527 ◽  
Author(s):  
T. P. Pons ◽  
P. E. Garraghty ◽  
M. Mishkin
Keyword(s):  
Substantial Reduction ◽  
Receptive Fields ◽  
Somatosensory System ◽  
Encounter Rate ◽  
Specific Information ◽  
Tactile Information ◽  
Cortical Areas ◽  
Area 3A ◽  
Area 3B ◽  
Made In

1. Selective ablations of the hand representations in postcentral cortical areas 3a, 3b, 1, and 2 were made in different combinations to determine each area's contribution to the responsivity and modality properties of neurons in the hand representation in SII. 2. Ablations that left intact only the postcentral areas that process predominantly cutaneous inputs (i.e., areas 3b and 1) yielded SII recording sites responsive to cutaneous stimulation and none driven exclusively by high-intensity or "deep" stimulation. Conversely, ablations that left intact only the postcentral areas that process predominantly deep receptor inputs (i.e., areas 3a and 2) yielded mostly SII recording sites that responded exclusively to deep stimulation. 3. Ablations that left intact only area 3a or only area 2 yielded substantial and roughly equal reductions in the number of deep receptive fields in SII. By contrast, ablations that left intact only area 3b or only area 1 yielded unequal reductions in the number of cutaneous receptive fields in SII: a small reduction when area 3b alone was intact but a somewhat larger one when only area 1 was intact. 4. Finally, when the hand representation in area 3b was ablated, leaving areas 3a, 1, and 2 fully intact, there was again a substantial reduction in the encounter rate of cutaneous receptive fields. 5. The partial ablations often led to unresponsive sites in the SII hand representation. In SII representations other than of the hand no such unresponsive sites were found and there were no substantial changes in the ratio of cutaneous to deep receptive fields, indicating that the foregoing results were not due to long-lasting postsurgical depression or effects of anesthesia. 6. The findings indicate that modality-specific information is relayed from postcentral cortical areas to SII along parallel channels, with cutaneous inputs transmitted via areas 3b and 1, and deep inputs via areas 3a and 2. Further, area 3b provides the major source of cutaneous input to SII, directly and perhaps also via area 1. 7. The results are in line with accumulating anatomic and electrophysiologic evidence pointing to an evolutionary shift in the organization of the somatosensory system from the general mammalian plan, in which tactile information is processed in parallel in SI and SII, to a new organization in higher primates in which the processing of tactile information proceeds serially from SI to SII. The presumed functional advantages of this evolutionary shift are unknown.

scholarly journals How Much Support Is There for the Recommendations Made to the General Population during Confinement? A Study during the First Three Days of the COVID–19 Quarantine in Spain

2020 ◽  
Vol 17 (12) ◽  
pp. 4382 ◽  
Author(s):  
Carlos Suso-Ribera ◽  
Ramón Martín-Brufau
Keyword(s):  
General Population ◽  
Effect Sizes ◽  
Personality Profiles ◽  
Quality Of Sleep ◽  
Personality Variables ◽  
The Face ◽  
Anxiety Levels ◽  
The Relationship ◽  
Made In

Background: Recommendations on lifestyles during quarantine have been proposed by researchers and institutions since the COVID–19 crisis emerged. However, most of these have never been tested under real quarantine situations or derive from older investigations conducted mostly in China and Canada in the face of infections other than COVID–19. The present study aimed at exploring the relationship between a comprehensive set of recommended lifestyles, socio–demographic, and personality variables and mood during the first stages of quarantine. Methods: A virtual snow–ball recollection technique was used to disseminate the survey across the general population in Spain starting the first day of mandatory quarantine (15 March 2020) until three days later (17 March). In total, 2683 Spanish adults (mean age = 34.86 years, SD = 13.74 years; 77.7% women) from the general population completed measures on socio–demographic, COVID–related, behavioral, personality/cognitive, and mood characteristics. Results: In the present study, depression and anger were higher than levels reported in a previous investigation before the COVID–19 crisis, while vigor, friendliness, and fatigue were lower. Anxiety levels were comparable. The expected direction of associations was confirmed for the majority of predictors. However, effect sizes were generally small and only a subset of them correlated to most outcomes. Intolerance of unpleasant emotions, neuroticism, and, to a lesser extent, agreeableness, sleep quality, young age, and time spent Internet surfing were the most robust and strongest correlates of mood states. Conclusions: Some recommended lifestyles (i.e., maintaining good quality of sleep and reducing Internet surfing) might be more important than others during the first days of quarantine. Promoting tolerance to unpleasant emotions (e.g., through online, self–managed programs) might also be of upmost importance. So far, recommendations have been made in general, but certain subgroups (e.g., certain personality profiles and young adults) might be especially vulnerable and should receive more attention.

scholarly journals COVID-19 and the importance of space in entrepreneurship research and policy

2020 ◽  
Vol 38 (8) ◽  
pp. 697-710 ◽  
Author(s):  
Steffen Korsgaard ◽  
Richard A Hunt ◽  
David M Townsend ◽  
Mads Bruun Ingstrup
Keyword(s):  
Economic System ◽  
Large Scale ◽  
Local Economies ◽  
Spatial Perspective ◽  
Entrepreneurship Research ◽  
Digital Platform ◽  
The Face ◽  
The Relationship ◽  
Research And Policy

Given the COVID-19 crisis, the importance of space in the global economic system has emerged as critical in a hitherto unprecedented way. Even as large-scale, globally operating digital platform enterprises find new ways to thrive in the midst of a crisis, small and medium-sized enterprises (SMEs) nestled in local economies have proven to be fragile to shocks, causing countless local economies to unravel in the face of severe challenges to survival. Here, we discuss the role of entrepreneurship in re-building local economies that are more resilient. Specifically, we take a spatial perspective and highlight how the COVID-19 crisis has uncovered problems in the current tendency for thin contextualisation and promotion of globalisation. Based on this critique, we outline new perspectives for thinking about the relationship between entrepreneurship, resilience and local economies. Here, a particular emphasis is given to resilience building through deeply contextualised policies and research, localised flows of products and labour, and the diversification of local economies.

scholarly journals Effect of electrical stimulation of receptive fields in people with lower limb amputation on variables of gait

IBRO Reports ◽  
2020 ◽  
Vol 9 ◽  
pp. 78-84
Author(s):  
Michael Pleus ◽  
Thomas Koller ◽  
Felix Tschui ◽  
Marion Grögli ◽  
Christina M. Spengler
Keyword(s):  
Electrical Stimulation ◽  
Lower Limb ◽  
Receptive Fields ◽  
Lower Limb Amputation ◽  
Limb Amputation ◽  
Stimulation Of

Defensive Movements Evoked by Air Puff in Monkeys

2003 ◽  
Vol 90 (5) ◽  
pp. 3317-3329 ◽  
Author(s):  
Dylan F. Cooke ◽  
Michael S. A. Graziano
Keyword(s):  
Startle Response ◽  
Receptive Fields ◽  
Initial Position ◽  
The Body ◽  
Precentral Gyrus ◽  
Cortical Areas ◽  
The Face ◽  
Ventral Intraparietal Area ◽  
Specific Reactions ◽  
Stimulation Of

Electrical stimulation of two connected cortical areas in the monkey brain, the ventral intraparietal area (VIP) in the intraparietal sulcus and the polysensory zone (PZ) in the precentral gyrus, evokes a specific set of movements. In one interpretation, these movements correspond to those typically used to defend the body from objects that are near, approaching, or touching the skin. The present study examined the movements evoked by a puff of air aimed at various locations on the face and body of fascicularis monkeys to compare them to the movements evoked by stimulation of VIP and PZ. The air-puff-evoked movements included a movement of the eyes from any initial position toward a central region and a variety of stereotyped facial, shoulder, head, and arm movements. These movements were similar to those reported on stimulation of VIP and PZ. One difference between the air-puff-evoked movements and those evoked by stimulation of VIP and PZ is that the air puff evoked an initial startle response (a bilaterally symmetric spike in muscle activity) followed by a more sustained, lateralized response, specific to the site of the air puff. In contrast, stimulation of VIP and PZ evoked mainly a sustained, lateralized response, specific to the site of the receptive fields of the stimulated neurons. We speculate that VIP and PZ may contribute to the control of defensive movements, but that they may emphasize the more spatially specific reactions that occur after startle.

scholarly journals STRENGTHENING THE ECONOMIC UNION: THE CHARTER AND THE AGREEMENT ON INTERNAL TRADE

2011 ◽  
Vol 12 (1, 2 & 3) ◽  
pp. 2002 ◽  
Author(s):  
Sujit Choudhry
Keyword(s):  
Public Policy ◽  
Large Scale ◽  
Policy Instruments ◽  
Economic Mobility ◽  
Constitutional Amendment ◽  
Constitutional Change ◽  
The Face ◽  
Economic Union ◽  
The Relationship ◽  
Internal Trade

The standard story in public policy and constitutional circles on the relationship between the Constitution and the Canadian Economic Union is a story of constitutional failure: that the Constitution has proven to be ineffective at furthering the integration of the Canadian economy.1 As a consequence, securing this goal requires either constitutional amendment or, in the face of the impossibility of large-scale constitutional change, the use of non-constitutional policy instruments such as the Agreement on Internal Trade, an intergovernmental agreement designed to remove barriers to interprovincial economic mobility.2 In this paper, I challenge this view. My argument is that constitutional litigation under the Charter’s3 mobility rights provisions can serve as an effective alternative to the various mechanisms (adjudication and negotiation) established under the AIT to further the integration of the Canadian economy. Moreover, I suggest how constitutional litigation can actually strengthen the AIT, rather than simply serve as an alternative to it.

Sensorimotor Integration in the Precentral Gyrus: Polysensory Neurons and Defensive Movements

2004 ◽  
Vol 91 (4) ◽  
pp. 1648-1660 ◽  
Author(s):  
Dylan F. Cooke ◽  
Michael S. A. Graziano
Keyword(s):  
Electrical Stimulation ◽  
Sensorimotor Integration ◽  
Receptive Fields ◽  
The Body ◽  
Auditory Stimuli ◽  
Precentral Gyrus ◽  
Defensive Reaction ◽  
Defensive Reactions ◽  
The Face ◽  
Stimulation Of

The precentral gyrus of monkeys contains a polysensory zone in which the neurons respond to tactile, visual, and sometimes auditory stimuli. The tactile receptive fields of the polysensory neurons are usually on the face, arms, or upper torso, and the visual and auditory receptive fields are usually confined to the space near the tactile receptive fields, within about 30 cm of the body. Electrical stimulation of this polysensory zone, even in anesthetized animals, evokes a specific set of movements. The movements resemble those typically used to defend the body from objects that are near, approaching, or touching the skin. In the present study, to determine whether the stimulation-evoked movements represent a normal set of defensive movements, we tested whether they include a distinctive, nonsaccadic, centering movement of the eyes that occurs during defensive reactions. We report that this centering movement of the eyes is evoked by stimulation of sites in the polysensory zone. We also recorded the activity of neurons in the polysensory zone while the monkey made defensive reactions to an air puff on the face. The neurons became active during the defensive movement, and the magnitude of this activity was correlated with the magnitude of the defensive reaction. These results support the hypothesis that the polysensory zone in the precentral gyrus contributes to the control of defensive movements. More generally, the results support the view that the precentral gyrus can control movement at the level of complex sensorimotor tasks.

scholarly journals Targeted cortical reorganization using optogenetics in non-human primates

eLife ◽  
2018 ◽  
Vol 7 ◽  
Author(s):  
Azadeh Yazdan-Shahmorad ◽  
Daniel B Silversmith ◽  
Viktor Kharazia ◽  
Philip N Sabes
Keyword(s):  
Large Scale ◽  
Network Connectivity ◽  
Cortical Reorganization ◽  
Strongly Correlated ◽  
Hebbian Plasticity ◽  
Two Measures ◽  
Evoked Activity ◽  
Large Scale Networks ◽  
Induced Changes ◽  
Stimulation Of

Brain stimulation modulates the excitability of neural circuits and drives neuroplasticity. While the local effects of stimulation have been an active area of investigation, the effects on large-scale networks remain largely unexplored. We studied stimulation-induced changes in network dynamics in two macaques. A large-scale optogenetic interface enabled simultaneous stimulation of excitatory neurons and electrocorticographic recording across primary somatosensory (S1) and motor (M1) cortex (Yazdan-Shahmorad et al., 2016). We tracked two measures of network connectivity, the network response to focal stimulation and the baseline coherence between pairs of electrodes; these were strongly correlated before stimulation. Within minutes, stimulation in S1 or M1 significantly strengthened the gross functional connectivity between these areas. At a finer scale, stimulation led to heterogeneous connectivity changes across the network. These changes reflected the correlations introduced by stimulation-evoked activity, consistent with Hebbian plasticity models. This work extends Hebbian plasticity models to large-scale circuits, with significant implications for stimulation-based neurorehabilitation.

scholarly journals Evidence for the organization of chromatin in megabase pair-sized loops arranged along a random walk path in the human G0/G1 interphase nucleus.

1995 ◽  
Vol 130 (6) ◽  
pp. 1239-1249 ◽  
Author(s):  
H Yokota ◽  
G van den Engh ◽  
J E Hearst ◽  
R K Sachs ◽  
B J Trask
Keyword(s):  
Random Walk ◽  
Dna Sequences ◽  
Large Scale ◽  
Loop Model ◽  
Interphase Nuclei ◽  
Attachment Sites ◽  
The Relationship ◽  
Made In ◽  
Random Walk Path

We determined the folding of chromosomes in interphase nuclei by measuring the distance between points on the same chromosome. Over 25,000 measurements were made in G0/G1 nuclei between DNA sequences separated by 0.15-190 megabase pairs (Mbp) on three human chromosomes. The DNA sequences were specifically labeled by fluorescence in situ hybridization. The relationship between mean-square interphase distance and genomic separation has two linear phases, with a transition at approximately 2 Mbp. This biphasic relationship indicates the existence of two organizational levels at scales > 100 kbp. On one level, chromatin appears to be arranged in large loops several Mbp in size. Within each loop, chromatin is randomly folded. On the second level, specific loop-attachment sites are arranged to form a supple, backbonelike structure, which also shows characteristic random walk behavior. This random walk/giant loop model is the simplest model that fully describes the observed large-scale spatial relationships. Additional evidence for large loops comes from measurements among probes in Xq28, where interphase distance increases and then locally decreases with increasing genomic separation.

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