Neurogenesis Drives Stimulus Decorrelation in a Model of the Olfactory Bulb

The reshaping and decorrelation of similar activity patterns by neuronal networks can enhance their discriminability, storage, and retrieval. How can such networks learn to decorrelate new complex patterns, as they arise in the olfactory system? Using a computational network model for the dominant neural populations of the olfactory bulb we show that fundamental aspects of the adult neurogenesis observed in the olfactory bulb -- the persistent addition of new inhibitory granule cells to the network, their activity-dependent survival, and the reciprocal character of their synapses with the principal mitral cells -- are sufficient to restructure the network and to alter its encoding of odor stimuli adaptively so as to reduce the correlations between the bulbar representations of similar stimuli. The decorrelation is quite robust with respect to various types of perturbations of the reciprocity. The model parsimoniously captures the experimentally observed role of neurogenesis in perceptual learning and the enhanced response of young granule cells to novel stimuli. Moreover, it makes specific predictions for the type of odor enrichment that should be effective in enhancing the ability of animals to discriminate similar odor mixtures

Olfactory language and abstraction across cultures

Olfaction presents a particularly interesting arena to explore abstraction in language. Like other abstract domains, such as time, odours can be difficult to conceptualize. An odour cannot be seen or held, it can be difficult to locate in space, and for most people odours are difficult to verbalize. On the other hand, odours give rise to primary sensory experiences. Every time we inhale we are using olfaction to make sense of our environment. We present new experimental data from 30 Jahai hunter-gatherers from the Malay Peninsula and 30 matched Dutch participants from the Netherlands in an odour naming experiment. Participants smelled monomolecular odorants and named odours while reaction times, odour descriptors and facial expressions were measured. We show that while Dutch speakers relied on concrete descriptors, i.e. they referred to odour sources (e.g. smells like lemon), the Jahai used abstract vocabulary to name the same odours (e.g. musty). Despite this differential linguistic categorization, analysis of facial expressions showed that the two groups, nevertheless, had the same initial emotional reactions to odours. Critically, these cross-cultural data present a challenge for how to think about abstraction in language.This article is part of the theme issue 'Varieties of abstract concepts: development, use and representation in the brain'

Consolidation of an Olfactory Memory Trace in the Olfactory Bulb Is Required for Learning-Induced Survival of Adult-Born Neurons and Long-Term Memory

Background: It has recently been proposed that adult-born neurons in the olfactory bulb, whose survival is modulated by learning, support long-term olfactory memory. However, the mechanism used to select which adult-born neurons following learning will participate in the long-term retention of olfactory information is unknown. We addressed this question by investigating the effect of bulbar consolidation of olfactory learning on memory and neurogenesis. Methodology/Principal Findings: Initially, we used a behavioral ecological approach using adult mice to assess the impact of consolidation on neurogenesis. Using learning paradigms in which consolidation time was varied, we showed that a spaced (across days), but not a massed (within day), learning paradigm increased survival of adult-born neurons and allowed long-term retention of the task. Subsequently, we used a pharmacological approach to block consolidation in the olfactory bulb, consisting in intrabulbar infusion of the protein synthesis inhibitor anisomycin, and found impaired learning and no increase in neurogenesis, while basic olfactory processing and the basal rate of adult-born neuron survival remained unaffected. Taken together these data indicate that survival of adult-born neurons during learning depends on consolidation processes taking place in the olfactory bulb. Conclusion/Significance: We can thus propose a model in which consolidation processes in the olfactory bulb determine both survival of adult-born neurons and long-term olfactory memory. The finding that adult-born neuron survival durin

Social odors conveying dominance and reproductive information induce rapid physiological and neuromolecular changes in a cichlid fish

Background: Social plasticity is a pervasive feature of animal behavior. Animals adjust the expression of their social behavior to the daily changes in social life and to transitions between life-history stages, and this ability has an impact in their Darwinian fitness. This behavioral plasticity may be achieved either by rewiring or by biochemically switching nodes of the neural network underlying social behavior in response to perceived social information. Independent of the proximate mechanisms, at the neuromolecular level social plasticity relies on the regulation of gene expression, such that different neurogenomic states emerge in response to different social stimuli and the switches between states are orchestrated by signaling pathways that interface the social environment and the genotype. Here, we test this hypothesis by characterizing the changes in the brain profile of gene expression in response to social odors in the Mozambique Tilapia, Oreochromis mossambicus. This species has a rich repertoire of social behaviors during which both visual and chemical information are conveyed to conspecifics. Specifically, dominant males increase their urination frequency during agonist encounters and during courtship to convey chemical information reflecting their dominance status. Results: We recorded electro-olfactograms to test the extent to which the olfactory epithelium can discriminate between olfactory information from dominant and subordinate males as well as from pre- and post-spawning females. We then performed a genome-scale gene expression analysis of the olfactory bulb and the olfactory cortex homolog in order to identify the neuromolecular systems involved in processing these social stimuli. Conclusions: Our results show that different olfactory stimuli from conspecifics' have a major impact in the brain transcriptome, with different chemical social cues eliciting specific patterns of gene expression in the brain. These results confirm the role of rapid changes in gene expression in the brain as a genomic mechanism underlying behavioral plasticity and reinforce the idea of an extensive transcriptional plasticity of cichlid genomes, especially in response to rapid changes in their social environment.Fundacao para a Ciencia e a Tecnologia (FCT, Portugal) [EXCL/BIA-ANM/0549/2012, Pest-OE/MAR/UI0331/2011]; Dwight W. and Blanche Faye Reeder Centennial Fellowship in Systematic and Evolutionary Biology; Institute for Cellular and Molecular Biology Fellowship; FCTinfo:eu-repo/semantics/publishedVersio

Sanat olarak oyun, oyun olarak sanat

‘Gerçeklik’, ilk çağlardan günümüze kadar insan aklını meşgul eden bir kavramdır ve tüm düşünce tarihi boyunca dış dünya-insan ilişkilerinde, değişik yorumlamalarla ele alınmıştır. Gerçeklik, insanlık tarihinde, önce dinsel ve mitolojik açılımlarla ifade edilmiş, ardından Antik Yunan’da bu açılımların bir eleştirisi yapılarak, gerçeklik nesnel doğa anlayışına dönüşmüştür. Orta Çağ’da ise, yükselen manevi değerler ve çok tanrıcılıktan, tek tanrıcılığa geçişle, tek ve asıl gerçek ‘Tanrı’ olarak kabul edilmiş, hemen ardından Yeni Çağ’ın başlangıcıyla, rasyonalist düşünce ve bireysellik ön plana geçmiş ve bu bağlamda gerçeklik, akıl yoluyla ulaşılır olan olarak kabul edilmiştir. Modernizm’le doruk noktasına ulaşan, rasyonalist gerçeklik algılayışı, bilim ve teknoloji alanındaki tüm olumlu gelişmelere rağmen insanlığı içinde bulunduğu sorunlardan kurtarmak yerine daha büyük bunalımlara sürüklemesiyle ağır bir eleştiriye maruz kalmış ve 20. yüzyılın ikinci yarısında Postmodernizm, Modernizm’in evrensellik atfettiği gerçekliği, artık tahtından indirmiş, ne kadar insan, ne kadar düşünce varsa o kadar gerçeklik vardır söylemiyle, düşünce tarihindeki gerçeklik anlayışına bu gün için son şeklini vermiştir. Kökenleri en eski insanlık tarihine kadar uzanan sanat’ı ise, “gerçeklik” düşüncesinin tarihteki gelişimi paralelinde değerlendirmemiz gerekir. Biliyoruz ki sanat, ilk çağlarda insanın korkularını ve ibadetlerini yansıtmaya yönelik işlevsel bir içerikle biçimlenirken, tarih boyunca değişen toplum yapısı ve “gerçeklik” algısı, sanatı hem içerik, hem de biçim olarak değişime uğratmıştır. Estetik tarihinde, Platon ve Aristotales’in Mimesis Kuramıyla başlayan, sanatta nesnelliği ön plana çıkartan yaklaşım, zaman zaman yerini öznelliğe bırakmıştır. İşte kuramsal yaklaşımlardaki, bu değişimleri her zaman ortaya çıktığı çağın koşullarıyla birlikte değerlendirmek gerekir. İster nesnel, ister öznel bakış açısıyla sanata yaklaşıyor olalım, sanat özünde, her zaman insanın kendini ve doğayı anlama isteğinin karşılığı olarak ve Mondrian’ın dediği gibi bir “evrene katılma” olayı içinde ortaya çıkar. Ancak buradaki evrene katılma, varolan düzene basit bir dahil oluştan çok, evreni değiştiren bir yaratıcılık sürecini içerir. Ve bu bağlamda sanatsal bir faaliyeti, arkaik insanın gerçeğin belli bir temsiline dayanan, tüm faaliyetleriyle ilişkilendirmek mümkündür. Biliyoruz ki, ilkel, algıladığı “gerçek”liği evrene katılma amacıyla ve temsiliyet biçiminde oynamaktadır. Çeşitli biçimler altındaki ifadelerine tanık olduğumuz oyunu, kendi ilkeselliği içinde ele aldığımız zaman ise; bize, hem ilkelin, hem çocuğun, hem de sanatçının hatta tamamen içgüdüsel sebeplerle oyun oynayan hayvanın bile faaliyetlerini içeren bir bütünsellik sunduğunu görürüz. Şimdiye kadar “oyunun özü nedir?” sorusuna cevap arayan pek çok yaklaşım, doğruluk payı taşımlarına rağmen onu bütünselliği ile ele alamamışlardır. Oysa oyunu kendine ait bir anlam dünyası yaratan bir faaliyet olarak bütünsellik, haz, düzen, kuralların varlığı, özgürlük ve kendiliğindenlik ilkeleri ile açtığımız zaman, oyunda biçim ve içerik ilişkisini tam anlamıyla kurabilmiş ve bu bağlamda da oyunun görünüşe çıktığı her biçimi tanıma imkanına sahip olmuş oluruz. İşte bu çerçeve içinde, Huizinga’nın “oyun” düşüncesinden temellendirdiği, kültür ve kültüre şeklini veren hayat biçimlerinin yanına sanatı da eklemek yanlış görünmüyor. Sanat, bütün boyutları ile insan dünyasını kendine nesne yaparak, insana ilişkin yaşantı olanaklarını, insanın bütünlük isteğinin temsili olarak tekrar tekrar arar ve kurar ve bu faaliyet, tarihin her döneminde özünü oyunsallıktan alır. Huizinga’nın da dile getirdiği gibi; oyunsal unsur, en yüksek faaliyetlerde de varlığını sürdürür. Bu çerçeve içinde sanatı, gerek ilkelin, gerek çocuğun oyunundan ayıran tek fark, kendine konu edindiği problemi bilince çıkarmak farkı ile sezgisel alanda derinleşmesi ve bu anlamda da tam anlamıyla insanı özgürleştiren bir faaliyet olmasıdır. Yani sanat, akılla duygu arasında, bilinçle bilinçdışı arasında, kişiselle evrensel arasında, gelenekselle çağdaş arasında sınır tanımayan, özgür ve bütünsel bir dildir. Başka bir ifade ile oyun, kendine ait bir anlam dünyası yaratan bir faaliyet olarak, hayvanın, çocuğun ve ilkelin hayatında içgüdüsel ve sezgisel alana ait kalmakta, oysa gelişkin biçimiyle, yetişkin insanın hem bilinçte ayrıştıran hem sezgide derinleştiren faaliyeti olarak sanat alanına kadar yükselmektedir. Şunu unutmamalıyız ki; insanlık en eski çağlarda bile, korkularını ve inançlarını dile getirmeye dayalı olarak biçimlerle düzen oluşturma uğraşısında bulunmuştur ve bu uğraş aslında oyunsal bir tavırdan kaynaklanmaktadır ve en başından beri oyuna içkin olan tüm özellikleri de içinde taşır. İster ilkel insanın, kutsal nitelikteki ibadetlerini ve işleve yönelik sanatını ele alalım, ister günümüz sanatını, kavramsal alt yapısıyla oluştuğu biçimlerinde ele alalım, temsile yönelik ifade her zaman için oyunsaldır diyebiliriz. Sanat ta, oyun da, kurallarını kendinden çıkarıp, akla getiren birer faaliyet olarak işlevlerini anlamlarında bulurlar. Bu çerçeve içerisinde oyuna içkin olarak bulduğumuz bütünsellik, düzen, kuralların varlığı, özgürlük, kendiliğindenlik ve haz’ı bu sefer sanatın olmazsa olmaz koşulları olarak tekrar bulmaktayız. Sonuç olarak, sanatsal bir faaliyet, her zaman özünde oyunsal unsur taşır. Sanatçı yarattığı figürlerde bir kişileştirme oyunu oynar, mitlerden veya arketiplerden yararlanarak ilk varoluş ifadesini tekrar tekrar canlandıran bir kurguya yönelir. Her sanatçı, yapıtları aracılığı ile kurduğu bu varoluş ifadesinde, evren içinde kendi evrenini bir kez daha kurmuş olur. Bu anlamda sanat, sanatçının her yapıtı aracılığı ile kendi yeniden doğuşunu simgesel olarak gerçekleştirebildiği arketipsel bir alana uzanır. Huizinga’nın dediği gibi, eğer oyun belirgin imgelerin kullanımına, gerçeğin belli bir temsiline dayanıyorsa, sanat ta tam olarak, varoluşun imgeleştirildiği bir oyundur, oyunun görünüşe çıktığı bir biçimdir. Sanatçının kullandığı malzeme ne olursa olsun, veya başka bir ifade ile sanatçı hangi disiplin içinde hareket ederse etsin, oyun olarak sanat, insanın kozmos içindeki varoluşunu tekrar tekrar anlamlandıran bir ifadedir, bir dildir, bir kurgudur. Bu anlamda seramik te bir ifade olarak oyunsaldır. Seramiğin tarih içindeki serüvenine baktığımızda, ilk çağlardan 20. yüzyıla gelinceye kadar, seramik sanatçısı yöneldiği her üslup aracılığı ile (işlevsel seramikten, işlevsel olmayan seramiğe, geleneksel tarzdan, Funk’a, Kavramsal Sanat’a kadar) oyunsal bir tavırla yaratmaktadır. SUMMARY Human intelligence has been occupied with the concept of “Reality” since the Stone Age. The concept of “Reality” has been considered from different points of views concerning the relation between the world and the human being. “Reality” has at first been interpreted in terms of religious and mythological senses in human history. In ancient Greek this understanding was criticized and “Reality” concept has transformed into an objective understanding of the nature. During the middle ages, monotheist thinking has considered ‘God’ to be the only reality. This was followed by the new age understanding of rationalism where reality becomes something which can only reached by logic. Despite all the achievements and progress in science and technology, the rationalist reality perception that was shaped in modernist thinking has been widely criticized as it led the human kind into a greater crises rather than solving the problems it faced. As a result, postmodernism changed the understanding that interpreted reality having a “universal” nature and stated clearly that there are as many realities as there are people and ideas. We have to evaluate the concept of art in parallel with the evolution of the concept of “reality” in history. We know that art that has been shaped after religious beliefs, worships, and fears of the Stone Age men. The ever changing social structure and reality perception has transformed art both in terms of its content and its shape. If look at the history of aesthetics we see that the objectivity approach of Platon and Aristotle which started with the theory of Mimesis left its place to subjectivity in time. Our approach to art may be objective or subjective, but regardless of the approach we adopt, we always find, in the essence of art, the desire to understand humanity and nature and a willingness to “join the universe”. Joining the universe in this context is not just an act of becoming a part of a system that already exists; it involves a creative process which also transforms the universe while becoming a part of it. In this sense, we can say that the ancient man played as to add what he perceived as the “reality” to the universe. When we look at the play of the ancient men, children, artists, or even the animals; we see that the activities considered as play have a holistic nature. Until now the question ‘What is the essence of play?’ has not been answered taking into consideration all the complex realities lying behind it. If we consider play as a holistic activity, a means to gain satisfaction, a medium where order and rules exist, we can reach the point where we can understand all its forms. Under these circumstances, it would not be wrong to add art to the life forms, those that Huizinga based on play, which shape our culture. All aspects of art make the world we live in an object to ourselves and the essence of all this is based on play. As Huizinga says, elements of play can be found even in the highest activities of the human kind. In this sense, the difference between art and the ancient man’s or child’s play can be found at the conscious deep investigation of the problem during artistic activity. This makes art a totally free, borderless language between the universe and the human being, between human senses and intelligence, between the conscious and the unconscious, between personal and universal, and between traditional and contemporary. In other words, play, which derives its own meaning through its own activities, is instinctive in the world of animals, ancient men, and children. In the adult’s world, however, play becomes an artistic show. Even the ancient man has tired to create an order using different forms to express his beliefs and fears. This is actually emanates from a game-playing attitude and carries all the elements of game: Holistic and orderly nature, existence of rules, freedom, spontaneity, and pleasure. As a result, we can say that an artistic activity always carries game elements in itself. The artist plays a game of personalization with the figures he creates and characterizes the expression of existence over and over again. Each artist, through such an expression of existence, creates his own individual universe within the universe. Art, in this sense, is a way of expressing the rebirth of the artist through his own art-work. As Huizinga says, if game relies on the usage of specific symbols and is a characteristic representation of reality; then art is a game where existence itself is symbolized. Whatever material the artist chooses to use or the discipline he chooses to follow, art as a game is a re-representation of the existence of the human kind in the universe. In this sense, ceramic arts also carry game elements. Throughout the history of ceramics, independent of the style the ceramic artist adopts (functional, non-functional, traditional, Funk, conceptual art), he creates with a game-like attitude

Stimulus-specific behavioral responses of zebrafish to a large range of odors exhibit individual variability

Background Odor-driven behaviors such as feeding, mating, and predator avoidance are crucial for animal survival. The neural pathways processing these behaviors have been well characterized in a number of species, and involve the activity of diverse brain regions following stimulation of the olfactory bulb by specific odors. However, while the zebrafish olfactory circuitry is well understood, a comprehensive characterization linking odor-driven behaviors to specific odors is needed to better relate olfactory computations to animal responses. Results Here, we used a medium-throughput setup to measure the swimming trajectories of 10 zebrafish in response to 17 ecologically relevant odors. By selecting appropriate locomotor metrics, we constructed ethograms systematically describing odor-induced changes in the swimming trajectory. We found that adult zebrafish reacted to most odorants using different behavioral programs and that a combination of a few relevant behavioral metrics enabled us to capture most of the variance in these innate odor responses. We observed that individual components of natural food and alarm odors do not elicit the full behavioral response. Finally, we show that zebrafish blood elicits prominent defensive behaviors similar to those evoked by skin extract and activates spatially overlapping olfactory bulb domains. Conclusion Altogether, our results highlight a prominent intra- and inter-individual variability in zebrafish odor-driven behaviors and identify a small set of waterborne odors that elicit robust responses. Our behavioral setup and our results will be useful resources for future studies interested in characterizing innate olfactory behaviors in aquatic animals

Learning-dependent neurogenesis in the olfactory bulb determines long-term olfactory memory

International audienceInhibitory interneurons of the olfac-tory bulb are subjected to permanent adult neurogen-esis. Their number is modulated by learning, suggesting that they could play a role in plastic changes of the bulbar network associated with olfactory memory. Adult male C57BL/6 mice were trained in an associative olfactory task, and we analyzed long-term retention of the task 5, 30, and 90 d post-training. In parallel, we assessed the fate of these newborn cells, mapped their distribution in the olfactory bulb and measured their functional implication using the immediate early gene Zif268. In a second set of experiments , we pharmacologically modulated glutamater-gic transmission and using the same behavioral task assessed the consequences on memory retention and neurogenesis. Finally, by local infusion of an anti-mitotic drug, we selectively blocked neurogenesis during acquisition of the task and looked at the effects on memory retention. First we demonstrated that retrieval of an associative olfactory task recruits the newborn neurons in odor-specific areas of the olfactory bulb selected to survive during acquisition of the task and that it does this in a manner that depends on the strength of learning. We then demonstrated that acquisition is not dependent on neu-rogenesis if long-term retention of the task is abolished by blocking neurogenesis. Adult-born neurons are thus involved in changes in the neural representation of an odor; this underlies long-term olfactory memory as the strength of learning is linked to the duration of this memory. Neurogenesis thus plays a crucial role in long-term olfactory memory.-Sultan, S., Mandairon, N., Kermen, F., Garcia, S., Sacquet, J., Didier, A. Learning-dependent neurogenesis in the olfactory bulb determines long-term olfactory memory. FASEB J. 24, 2355-2363 (2010). www.fasebj.or