Top-down inputs enhance orientation selectivity in neurons of the primary visual cortex during perceptual learning.

Perceptual learning has been used to probe the mechanisms of cortical plasticity in the adult brain. Feedback projections are ubiquitous in the cortex, but little is known about their role in cortical plasticity. Here we explore the hypothesis that learning visual orientation discrimination involves learning-dependent plasticity of top-down feedback inputs from higher cortical areas, serving a different function from plasticity due to changes in recurrent connections within a cortical area. In a Hodgkin-Huxley-based spiking neural network model of visual cortex, we show that modulation of feedback inputs to V1 from higher cortical areas results in shunting inhibition in V1 neurons, which changes the response properties of V1 neurons. The orientation selectivity of V1 neurons is enhanced without changing orientation preference, preserving the topographic organizations in V1. These results provide new insights to the mechanisms of plasticity in the adult brain, reconciling apparently inconsistent experiments and providing a new hypothesis for a functional role of the feedback connections

Studying and Supporting Writing in Student Organizations as a High-Impact Practice

Institutions of postsecondary education, and the field of writing across the curriculum and in the disciplines (WAC/WID) in particular, need to do more to trouble learning paradigms that employ writing only in service to particular disciplines, only in traditional learning environments, and only in particular languages, or in service to an overly narrow or generalized idea of who students are, where they\u27re going, and what they need to get there. In relating a cross-section of a larger effort to study and support writing as a high-impact practice in a student chapter of an international nonprofit humanitarian engineering student organization, I will demonstrate that WAC/WID can and should empower students to use writing in student organizations, especially those that align with the four learning outcomes deemed essential by the National Leadership Council for Liberal Education and America\u27s Promise, as a means of integrating into and interrogating their social and political realities, and reshaping postsecondary education to better meet their needs and goals as individual learners and as citizens in a deliberative democracy

Social plasticity in the fish brain: Neuroscientific and ethological aspects

© 2019 Elsevier B.V. Social plasticity, defined as the ability to adaptively change the expression of social behavior according to previous experience and to social context, is a key ecological performance trait that should be viewed as crucial for Darwinian fitness. The neural mechanisms for social plasticity are poorly understood, in part due to skewed reliance on rodent models. Fish model organisms are relevant in the field of social plasticity for at least two reasons: first, the diversity of social organization among fish species is staggering, increasing the breadth of evolutionary relevant questions that can be asked. Second, that diversity also suggests translational relevance, since it is more likely that “core” mechanisms of social plasticity are discovered by analyzing a wider variety of social arrangements than relying on a single species. We analyze examples of social plasticity across fish species with different social organizations, concluding that a “core” mechanism is the initiation of behavioral shifts through the modulation of a conserved “social decision-making network” along with other relevant brain regions, by monoamines, neuropeptides, and steroid hormones. The consolidation of these shifts may be mediated via neurogenomic adjustments and regulation of the expression of plasticity-related molecules (transcription factors, cell cycle regulators, and plasticity products)

Postsynaptic protein organization revealed by electron microscopy.

Neuronal synapses are key devices for transmitting and processing information in the nervous system. Synaptic plasticity, generally regarded as the cellular basis of learning and memory, involves changes of subcellular structures that take place at the nanoscale. High-resolution imaging methods, especially electron microscopy (EM), have allowed for quantitative analysis of such nanoscale structures in different types of synapses. In particular, the semi-ordered organization of neurotransmitter receptors and their interacting scaffolds in the postsynaptic density have been characterized for both excitatory and inhibitory synapses by studies using various EM techniques such as immuno-EM, electron tomography of high-pressure freezing and freeze-substituted samples, and cryo electron tomography. These techniques, in combination with new correlative approaches, will further facilitate our understanding of the molecular organization underlying diverse functions of neuronal synapses

Sleep-like slow oscillations improve visual classification through synaptic homeostasis and memory association in a thalamo-cortical model

The occurrence of sleep passed through the evolutionary sieve and is widespread in animal species. Sleep is known to be beneficial to cognitive and mnemonic tasks, while chronic sleep deprivation is detrimental. Despite the importance of the phenomenon, a complete understanding of its functions and underlying mechanisms is still lacking. In this paper, we show interesting effects of deep-sleep-like slow oscillation activity on a simplified thalamo-cortical model which is trained to encode, retrieve and classify images of handwritten digits. During slow oscillations, spike-timing-dependent-plasticity (STDP) produces a differential homeostatic process. It is characterized by both a specific unsupervised enhancement of connections among groups of neurons associated to instances of the same class (digit) and a simultaneous down-regulation of stronger synapses created by the training. This hierarchical organization of post-sleep internal representations favours higher performances in retrieval and classification tasks. The mechanism is based on the interaction between top-down cortico-thalamic predictions and bottom-up thalamo-cortical projections during deep-sleep-like slow oscillations. Indeed, when learned patterns are replayed during sleep, cortico-thalamo-cortical connections favour the activation of other neurons coding for similar thalamic inputs, promoting their association. Such mechanism hints at possible applications to artificial learning systems.Comment: 11 pages, 5 figures, v5 is the final version published on Scientific Reports journa

Governance and City Regeneration – A New Methodological Approach for Design and Evaluation

Governance has become a central topic among policymakers. There is an international consensus that policymaking is evolving from a traditional top-down government approach towards a system of governing that focuses on engaging the citizens within an area (Cabus, 2003). New forms of governance targeting urban competitiveness are increasingly oriented to vertical (between lower and high levels of government and cooperation forms between entities and firms along the production chain) and horizontal (between firms or different municipalities or public and private entities) cooperation (OEDC, 2005). Urban renewal policies underwent significant changes in recent decades. Synthetically, the following periods can be distinguished: 1970s: “hard†urban renewal – extensive physical interventions; 1980s: “soft†urban renewal - efforts to keep the original population in place; 1990s: “integrated urban renewal†- combining physical, economic and social interventions (Tosics, 2010). And over the last few years there has been a gradual shift in the understanding of what should be the tools and objectives of urban regeneration policies, with a greater emphasis on process-related and ‘soft’ issues of stakeholder engagement, partnership formation, leadership development, ‘institutional capacity’ development, knowledge and learning (Magalhães, 2004). This shift in the understanding of urban regeneration processes accomplishes the growing importance in literature of concepts like urban governance, institutional relational density, creativity, social capital, city branding and place marketing. The main purpose of this paper is to propose a new methodology for territorial analysis and planning focused on urban regeneration processes and its governance mechanisms. A new methodology that seeks, for each specific urban context, contribute to the following results: 1) Help select the most appropriate governance model to be adopted for each process of urban regeneration, 2) Monitor the partnership process and help promote the partnership guidance; 3) Support the design process and the definition of the strategic approach and projects, 4) Monitor the process of implementing the strategy and support multidimensional and multiscale evaluation of its results; 5) Evaluate the socio-economic and territorial impacts of urban regeneration processes.

Modulation of human corticospinal excitability by paired associative stimulation in patients with amyotrophic lateral sclerosis and effects of Riluzole

BACKGROUND Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease that causes an impairment in both the upper and lower motor neurons. The recent description of numerous non-motor signs points to an involvement of the neocortex networks that is more complex than was previously believed. Paired associative stimulation (PAS), a combination of transcranial magnetic stimulation (TMS) and peripheral nerve stimulation, can enhance motor output in the contralateral hand through an NMDA-mediated sensorimotor mechanism. OBJECTIVE To describe the effects of PAS on ALS patients before and after Riluzole intake compared with healthy subjects. METHODS PAS was used to detect differences between 24 newly-diagnosed ALS patients and 25 age-matched healthy controls. MEP amplitude from the abductor pollicis brevis was considered before PAS, immediately after (T0) and after 10 (T10), 20 (T20), 30 (T30) and 60 (T60) minutes. Statistical significance was calculated using RM-ANOVA. RESULTS In healthy controls, PAS significantly increased MEP amplitude at T10, T20 and T30 (p < 0.05). In ALS patients, a significant increase in MEP amplitude was also observed after 60 min (p < 0.05), thus demonstrating NMDA-mediated enhanced facilitatory plasticity. After two weeks of riluzole intake, no MEP amplitude increase was evident after PAS at any time point. In three monomelic-onset ALS patients, sensorimotor facilitation was evident only in the hemisphere corresponding to the affected side and appeared in the opposite hemisphere when the patients manifested contralateral symptoms. CONCLUSIONS PAS may be considered a useful tool when investigating NMDA-mediated neocortical networks in ALS patients and the modulation of such networks after anti-glutamatergic drug intake

Neural Substrates of Chronic Pain in the Thalamocortical Circuit

Chronic pain (CP), a pathological condition with a large repertory of signs and symptoms, has no recognizable neural functional common hallmark shared by its diverse expressions. The aim of the present research was to identify potential dynamic markers shared in CP models, by using simultaneous electrophysiological extracellular recordings from the rat ventrobasal thalamus and the primary somatosensory cortex. We have been able to extract a neural signature attributable solely to CP, independent from of the originating conditions. This study showed disrupted functional connectivity and increased redundancy in firing patterns in CP models versus controls, and interpreted these signs as a neural signature of CP. In a clinical perspective, we envisage CP as disconnection syndrome and hypothesize potential novel therapeutic appraisal