Barrels by the sea: Barrels XX meeting report

The 20th annual Barrels meeting brought together researchers who utilize behavioral, physiological, anatomical, and molecular techniques to understand the structure and function of the barrel system. Barrels XX featured talks on the role inhibition has in shaping cortical responses within the barrel system, the molecular cues that influence the development of the whisker-to-barrel system, and the synaptic plasticity that can shape responses within the system. The meeting highlighted why the whisker-to-barrel system is an ideal model to investigate the development of cortical circuitry and how its functioning can influence behavioral responses.     

Barrels XXIII: Barrels by the shore

The 23rd annual Barrels meeting was held on the University of California, San Diego campus and highlighted the latest advances in the whisker-to-barrel pathway and beyond. The annual meeting brought together investigators from a dozen countries to present their data in posters and short talks. The meeting focused on several themes, first the barrel system was used as a model to study the consequences that result from alterations in the normal pattern(s) of development. A second session focused on what happens to whisker information once it leaves the layer IV barrel. A third session addressed issues of coding within the barrel system and a final session highlighted the latest advances in the engineering of transgenic mouse lines. The meeting highlighted the utility of the barrel system to study cortical circuitry in the normal and pathological state.     

Barrels XXX meeting report: Barrels in Baltimore

The Barrels meeting annually brings together researchers focused on the rodent whisker to cortical barrel system prior to the Society for Neuroscience meeting. The 2017 meeting focused on the classification of cortical interneurons, the role interneurons have in shaping brain dynamics, and finally on the circuitry underlying oral sensations. The meeting highlighted the latest advancements in this rapidly advancing field.     

Barrels XXII meeting report: Barrels blow into the Windy City

The 22nd Annual Barrels Meeting blew into Evanston, near the Windy City, in November 2009 as the meeting was hosted on the Evanston, IL campus of Northwestern University. The longest running satellite meeting to the Society for Neuroscience Meeting annually brings together researchers from around the world focused on the development, function, behavior, and physiology of the rodent whisker-to-barrel system and other associated cortical and subcortical areas. The 2009 edition of the meeting was focused on three central themes: the molecular development and developmental plasticity in barrel cortex, optical analysis of barrel cortex function, and the coding of touch. The main symposia were complemented by short talks, data blitz sessions, and a poster session.     

Barrels XXXII meeting report: whiskers in the windy city

Abstract

The 32nd Annual Barrels meeting was hosted at the Northwestern University Feinberg School of Medicine in Chicago, Illinois on October 17th and 18th, 2019. The annual meeting brings together researchers who utilize the rodent whisker-to-barrel system as a means to understand cortical function and development. This year’s meeting focussed on social behaviours, development and cerebellar functions within the barrel system and beyond.     

Barrels XXIX: Barrels go Hollywood

Barrels XXIX brought together researchers focusing on the rodent barrel cortex and associated systems. The meeting revolved around three themes: thalamocortical interactions in motor control, touch in rodent, monkey, and humans, and the nature of the multisensory computations the brain makes. Over two days these topics were covered as well as many more presentations that focused on the physiology, behavior, and development of the rodent whisker-to-barrel cortex system.     

Barrels XXXI comes to the inland empire

The 31st annual Barrels meeting was held on the campus of the University of California, Riverside on the first two days of November, 2018. The meeting focuses on the whisker to cortical barrel pathway and the systems it impacts. This year’s meeting focussed on the neural mechanisms of motor control, the functions of higher order thalamic nuclei and adaptable perception and decision-making.     

Barrels III: Proceedings of a Satellite Symposium of the 1990 Society for Neuroscience Meeting

On October 27 and 28, 1990, approximately 100 somatosensory neurobiologists met in St. Louis, Missouri to discuss the current state of inquiry into the organization of the somatosensory system, emphasizing those portions of the system devoted to processing of inputs from digitized cutaneous organs, such as the rodent mystacial vibrissae. Given the homeomorphic relationship between the vibrissae and cortical and subcortical barrels, a large number of laboratories now employ this model to ask fundamental questions about central processing of sensory inputs, mechanisms controlling topographic pattern formation, and substrates for injury-induced neuronal reorganization. The focus of the third annual Barrels Symposium (Barrels III) was on behavioral aspects of the whisker sense, cholinergic regulation of cortical modules, and genetic and peripheral determinants of barrel development.     

Barrels XXVIII take the Windy City by storm

The 28th annual Barrels meeting was held prior to the Society for Neuroscience meeting in October 2015 at the Northwestern University School of Law in Chicago, Illinois. The meeting brought together researchers focused on the rodent sensorimotor system. The meeting focused on modern techniques to decipher cortical circuits, social interactions among rodents, and decision-making. The meeting allowed investigators to share their work via short talks, poster presentations, and a data blitz.     

An ocean full of BARRELS: Barrels XXVI meeting report

The 26th annual Barrels meeting was convened on the campus of the University of California San Diego, not far from the shores of the Pacific Ocean. The meeting focused on three main themes: the structure and function of the thalamic reticular nucleus, the neurovasculature system and its role in brain metabolism, and the origins and functions of cortical GABAergic interneurons. In addition to the major themes, there were short talks, a data blitz, and a poster session which highlighted the diversity and quality of the research ongoing in the rodent whisker-to-barrel system.     

Barrels VIII: Proceedings of a Satellite Symposium of the 1995 Society for Neuroscience Meeting

A meeting of somatosensory and developmental biologists was held on November 10 and 11, 1995, in San Diego, California, to consider recent findings pertaining to the somatosensory system. The focus of this, the eighth annual Barrels Symposium (Barrels VIII), was on somatosensory circuits and plasticity, and the development of somatosensory primary afferent projections and barrel-like aggregates in the brainstem, thalamus, and cortex     

Subbarrel Patterns in Somatosensory Cortical Barrels Can Emerge from Local Dynamic Instabilities

Complex spatial patterning, common in the brain as well as in other biological systems, can emerge as a result of dynamic interactions that occur locally within developing structures. In the rodent somatosensory cortex, groups of neurons called “barrels” correspond to individual whiskers on the contralateral face. Barrels themselves often contain subbarrels organized into one of a few characteristic patterns. Here we demonstrate that similar patterns can be simulated by means of local growth-promoting and growth-retarding interactions within the circular domains of single barrels. The model correctly predicts that larger barrels contain more spatially complex subbarrel patterns, suggesting that the development of barrels and of the patterns within them may be understood in terms of some relatively simple dynamic processes. We also simulate the full nonlinear equations to demonstrate the predictive value of our linear analysis. Finally, we show that the pattern formation is robust with respect to the geometry of the barrel by simulating patterns on a realistically shaped barrel domain. This work shows how simple pattern forming mechanisms can explain neural wiring both qualitatively and quantitatively even in complex and irregular domains.     

Proceedings of the Barrels II Workshop: cortical circuits

The second session of the Barrels II Workshop focused on the function of cortical circuitry in the rodent vibrissa-to-barrel system. The session began with talks by Asaf Keller (University of Maryland), Christopher Moore (MIT), and David Pinto (Brown University). These presentations were followed by shorter talks by Mark Andermann (MIT), Alison Barth (Carnegie-Mellon University), Dirk Feldmeyer (Max Planck Institute), Cathy Garabedian (UCSF), Garrett Stanley (Harvard University), and Simona Temereanca (University of Pittsburgh). Presentations covered several central themes, including the functional organization of cortical circuitry, thalamocortical response transformations, temporal response properties, and the role of vibrissa resonance in high frequency representations. For simplicity, this review is organized by these central themes and does not follow the order of presentations at the meeting.     

Proceedings of the Barrels II Workshop: cortical circuits

The second session of the Barrels II Workshop focused on the function of cortical circuitry in the rodent vibrissa-to-barrel system. The session began with talks by Asaf Keller (University of Maryland), Christopher Moore (MIT), and David Pinto (Brown University). These presentations were followed by shorter talks by Mark Andermann (MIT), Alison Barth (Carnegie-Mellon University), Dirk Feldmeyer (Max Planck Institute), Cathy Garabedian (UCSF), Garrett Stanley (Harvard University), and Simona Temereanca (University of Pittsburgh). Presentations covered several central themes, including the functional organization of cortical circuitry, thalamocortical response transformations, temporal response properties, and the role of vibrissa resonance in high frequency representations. For simplicity, this review is organized by these central themes and does not follow the order of presentations at the meeting.     

Barrels: 25 Years Later

I thank Herb Killackey for his nice introduction. Time flies when you're having fun, and it was a revelation when Herb pointed out that this meeting of Barrels marks 25 years since the publication of my paper with the late Hendrik Van der Loos introducing barrels     

The functional organization of the barrel cortex

The tactile somatosensory pathway from whisker to cortex in rodents provides a well-defined system for exploring the link between molecular mechanisms, synaptic circuits, and behavior. The primary somatosensory cortex has an exquisite somatotopic map where each individual whisker is represented in a discrete anatomical unit, the "barrel," allowing precise delineation of functional organization, development, and plasticity. Sensory information is actively acquired in awake behaving rodents and processed differently within the barrel map depending upon whisker-related behavior. The prominence of state-dependent cortical sensory processing is likely to be crucial in our understanding of active sensory perception, experience-dependent plasticity and learning.     

Local cortical interactions determine the form of cortical plasticity.

Competitive interactions between left and right eye inputs to visual cortex during development are usually explained by the thalamocortical axons competing more or less well for cortical territory during retraction into eye specific domains. Here we review the evidence for competitive and co-operative interactions between cortical columns in barrel cortex which are present several weeks after retraction of thalamocortical axons into barrels. Sensory responses in barrel cortex can be altered by a period of vibrissa deprivation. It was found that responses to previously deprived vibrissae (that had been allowed to regrow) were depressed more if neighboring vibrissae were spared than if all vibrissae were removed simultaneously. Depression of the deprived vibrissa response was greater the closer the cell lay to a spared barrel. It was also found that spared vibrissae responses were potentiated more if several neighboring vibrissae were left intact than if only a single vibrissae was spared. These results suggest a mechanism of cooperative potentiation, perhaps due to intracortical summation of excitation evoked by neighbouring vibrissa stimulation. Thalamic responses to vibrissa stimulation were unaffected by deprivation indicating a cortical origin. One of the consequences of deprivation was that the speed of transmission between barrels was increased for spared and decreased for deprived vibrissa. These results imply that inherent interactions between cortical columns give rise to a property of competition and co-operativity which amplify the effects of sensory deprivation.     

Sexually dimorphic responses to neonatal basal forebrain lesions in mice: II. Cortical morphology

Previous studies in the mouse have shown that neonatal lesions to the cholinergic basal forebrain (nBM) areas result in transient cholinergic depletion of neocortex and precipitate altered cortical morphogenesis. Lesion-induced morphological alterations in cortex persist into adulthood and are accompanied by behavioral changes, including spatial memory deficits. The current study investigated whether neonatal nBM lesions affect male and female mice differently in adulthood. Quantitative morphometry of cortical layer width was employed to assess alterations in cytoarchitecture in neonatally nBM-lesioned and littermate control mice of both sexes following behavioral testing. Our results showed significant decreases in cortical layer IV and V widths across somato/motor cortex in neonatally nBM lesioned mice of both sexes. Sexually dimorphic responses were observed in cortical layer II/III and total cortical width, limited to the area containing the “barrel cortex” representation of the whisker hairs. In lesioned females, layer II/III and total cortical width were decreased relative to female controls, and in lesioned males, layer II/III was increased relative to controls, whereas total cortical width was unchanged. In male but not female mice we observed significant correlations between decreased widths in layer IV and V and impaired performance on a spatial memory task. The current data further support a role of developing cholinergic cortical afferents in the modulation of cortical morphogenesis and cortical circuits involved in cognitive behaviors. In addition, our observations provide further evidence for sexually dimorphic development and function in cognitive centers of the rodent brain. © 1998 John Wiley & Sons, Inc. J Neurobiol 37: 595–606, 1998     

Learning-Dependent Plasticity of the Barrel Cortex Is Impaired by Restricting GABA-Ergic Transmission

Experience-induced plastic changes in the cerebral cortex are accompanied by alterations in excitatory and inhibitory transmission. Increased excitatory drive, necessary for plasticity, precedes the occurrence of plastic change, while decreased inhibitory signaling often facilitates plasticity. However, an increase of inhibitory interactions was noted in some instances of experience-dependent changes. We previously reported an increase in the number of inhibitory markers in the barrel cortex of mice after fear conditioning engaging vibrissae, observed concurrently with enlargement of the cortical representational area of the row of vibrissae receiving conditioned stimulus (CS). We also observed that an increase of GABA level accompanied the conditioning. Here, to find whether unaltered GABAergic signaling is necessary for learning-dependent rewiring in the murine barrel cortex, we locally decreased GABA production in the barrel cortex or reduced transmission through GABAA receptors (GABAARs) at the time of the conditioning. Injections of 3-mercaptopropionic acid (3-MPA), an inhibitor of glutamic acid decarboxylase (GAD), into the barrel cortex prevented learning-induced enlargement of the conditioned vibrissae representation. A similar effect was observed after injection of gabazine, an antagonist of GABAARs. At the behavioral level, consistent conditioned response (cessation of head movements in response to CS) was impaired. These results show that appropriate functioning of the GABAergic system is required for both manifestation of functional cortical representation plasticity and for the development of a conditioned response.     

Cytotactin and its proteoglycan ligand mark structural and functional boundaries in somatosensory cortex of the early postnatal mouse

The expression of the extracellular matrix molecules cytotactin, which is synthesized by glia, and cytotactin-binding (CTB) proteoglycan, which is synthesized by neurons, was examined in the developing brain of the mouse, specifically in the cortical barrel field, using highly specific polyclonal antibodies to the purified molecules. Both molecules appeared early in the development of the cortex but were excluded from the centers of the developing barrels at the time of entry and arborization of thalamocortical axons. Of the two major forms of cytotactin (220 and 200 kDa), the larger form predominated during development of the mouse brain and also predominated in mixed neuron-glia cultures but not in pure glial cultures. Both cytotactin and CTB proteoglycan were recognized by various lectins that have been shown in other studies to demarcate the barrel field: both molecules were recognized by lentil lectin and concanavalin A and CTB proteoglycan was also recognized by peanut and wheat germ agglutinins. The HNK-1 carbohydrate antigen, present on cytotactin, CTB proteoglycan, and other adhesion molecules, was also found in the barrel walls and diminished in the barrel hollows. Cytotactin and CTB proteoglycan were preferentially expressed in barrel walls through P12. After this time, their expression became uniform even though the histological pattern of barrel walls and hollows was maintained. The fusion of a row of barrels which results from peripheral damage to a row of whiskers was accompanied by the loss of patterned expression of both molecules following electrocauterization of a row of whisker follicles at P1.5. We conclude that activity from the periphery is important not only to development of anatomical pattern but also of the molecular pattern and that the expression of both glial and neuronal proteins can respond to such activity. The results are consistent with previous studies showing that incoming thalamocortical axons play a primary role in barrel field formation. They also suggest that both the migration of cortical neurons on glia and the refinement of the mapping between the peripheral whisker field and its cortical representation may depend upon the distribution of substrate adhesion molecules.