Utilizing synthetic training data for the supervised classification of rat ultrasonic vocalizations

Murine rodents generate ultrasonic vocalizations (USVs) with frequencies that extend to around 120kHz. These calls are important in social behaviour, and so their analysis can provide insights into the function of vocal communication, and its dysfunction. The manual identification of USVs, and subsequent classification into different subcategories is time consuming. Although machine learning approaches for identification and classification can lead to enormous efficiency gains, the time and effort required to generate training data can be high, and the accuracy of current approaches can be problematic. Here we compare the detection and classification performance of a trained human against two convolutional neural networks (CNNs), DeepSqueak and VocalMat, on audio containing rat USVs. Furthermore, we test the effect of inserting synthetic USVs into the training data of the VocalMat CNN as a means of reducing the workload associated with generating a training set. Our results indicate that VocalMat outperformed the DeepSqueak CNN on measures of call identification, and classification. Additionally, we found that the augmentation of training data with synthetic images resulted in a further improvement in accuracy, such that it was sufficiently close to human performance to allow for the use of this software in laboratory conditions.Comment: 25 pages, 5 main figures, 2 table

Mode shifting between storage and recall based on novelty detection in oscillating hippocampal circuits.

ABSTRACT: It has been suggested that hippocampal mode shifting between a storage and a retrieval state might be under the control of acetylcholine (ACh) levels, as set by an autoregulatory hippocampo-septohippocampal loop. The present study investigates how such a mechanism might operate in a large-scale connectionist model of this circuitry that takes into account the major hippocampal subdivisions, oscillatory population dynamics and the time scale on which ACh exerts its effects in the hippocampus. The model assumes that hippocampal mode shifting is regulated by a novelty signal generated in the hippocampus. The simulations suggest that this signal originates in the dentate. Novel patterns presented to this structure lead to brief periods of depressed firing in the hippocampal circuitry. During these periods, an inhibitory influence of the hippocampus on the septum is lifted, leading to increased firing of cholinergic neurons. The resulting increase in ACh release in the hippocampus produces network dynamics that favor learning over retrieval. Resumption of activity in the hippocampus leads to the reinstatement of inhibition. Despite theta-locked rhythmic firing of ACh neurons in the septum, ACh modulation in the model fluctuates smoothly on a time scale of seconds. It is shown that this is compatible with the time scale on which memory processes take place. A number of strong predictions regarding memory function are derived from the model. © 2004 Wiley-Liss, Inc. KEY WORDS: acetylcholine; computational modeling; hippocampus; medial septum; memor

Mechanisms and Consequences of Microtubule-Based Symmetry Breaking in Plant Roots

Directional growth in plants is primarily determined by the axis of cell expansion, which is specified by the net orientation of cortical microtubules. Microtubules guide the deposition of cellulose and other cell wall materials. In rapidly elongating cells, transversely oriented microtubules create material anisotropy in the cell wall that prevents radial cell expansion, channeling cell expansion in the longitudinal direction. Mutations perturbing microtubule organization frequently lead to aberrant cell growth in land plants, with some mutations leading to helical growth patterns (called ‘twisted mutants’), often in roots. This phenotype manifests as right-handed or left-handed twisting of cell files along the long axis of plant organs, which correlates with rightward or leftward organ growth, respectively. Helical growth is a common occurrence in the plant kingdom and serves a variety of purposes, but the molecular mechanisms that produce helical growth and define handedness are not well understood. Furthermore, how molecular-level processes propagate across spatial scales to control organ-level growth is undefined. Here, I used the model plant Arabidopsis thaliana as an experimentally tractable system, focusing on the root organ to study the mechanisms underlying helical growth in plants. In this work, I used roots as a model plant organ to investigate the molecular mechanisms that control symmetry maintenance and symmetry breaking in plants. Arabidopsis roots are ideally suited for this work because of their simple, concentric ring-like cellular anatomy and well-defined process of development. I selected two Arabidopsis twisted mutants with opposite chirality to study whether the emergence of right-handed and left-handed helical growth involves conserved or distinct mechanisms. Cortical microtubules are skewed in the right-handed spr1 mutant, which lacks a microtubule plus end-associated protein that regulates polymerization dynamics. In contrast, cortical microtubules tend to be laterally displaced in the left-handed cmu1 mutant, which lacks a protein that contributes to the attachment of cortical microtubules to the plasma membrane. Using a cell-type specific complementation approach, I showed that both SPR1 and CMU1 gene expression in the epidermis alone is sufficient to maintain wild-type-like straight cell files and root growth. In addition, epidermal expression of SPR1 restores both the morphology and skew of the cortical cell file to wild-type-like. By genetically disrupting cell-cell adhesion in the spr1 mutant, I found that a physical connection between epidermal and cortical cells is required for the epidermis to cause organ-level skewed growth. Together, these data demonstrate that the epidermis plays a central role in maintaining straight root growth, suggesting that twisted plant growth in nature could arise by altering microtubule behavior in the epidermis alone and does not require null alleles in all cells. To examine whether cortical microtubule defects in the spr1-3 mutant affect cell growth, I conducted morphometry analysis. I found that while skewed cortical microtubule orientation correlates with asymmetric epidermal cell morphology and growth in the spr1-3 mutant root meristem, cell file twisting is not manifested until the differentiation zone of the root where cell growth slows down and root hairs emerge. Furthermore, I demonstrated that cell file twisting is not sufficient to generate skewed growth at the organ level, which requires that the root is grown on an agar medium, a mechanically heterogeneous environment. Increasing the stiffness of the agar medium caused the spr1-3 and cmu1 mutant roots to grow straight, indicating that mechanical stimuli influence twisted root growth. Despite their important role in root anchorage, root hairs on the epidermis are not required for skewed root growth, nor for reorienting root skewing in response to changes in the mechanical environment. Overall, this work provides new insights into how symmetry breaking affects root mechanoresponse. Spatial heterogeneity in the composition and organization of the plant cell wall affects its mechanics to control cell shape and directional growth. In the last chapter of this work, I describe a new methodology for imaging plant primary cell walls at the nanoscale using atomic force microscopy coupled with infrared spectroscopy (AFM-IR). I contributed to generating a novel sample preparation technique and employed AFM-IR and spectral deconvolution to generate high-resolution spatial maps of the mechanochemical signatures of the Arabidopsis epidermal cell wall. Cross-correlation analysis of the spatial distribution of chemical and mechanical properties suggested that the carbohydrate composition of cell wall junctions correlates with increased local stiffness. In developing this methodology, this chapter provides an essential foundation for applying AFM-IR to understand the complex mechanochemistry of intact plant cell walls at nanometer resolution

Analysis of Production and Location Decisions by Means of Multi-Criteria Analysis

During the last few years economists and operations researchers have paid much attention to multi-criteria analysis as a tool in modern decision-making. The basic feature of multi-criteria analysis is the fact that a wide variety of relevant decision aspects can be taken into account without a necessity to translate all these aspects in monetary terms. This article will give a brief survey of these new methods in both a quantitative and in a qualitative sense. After this survey the relevance of multi-criteria analysis for entrepreneurial decisions in the field of production and investments will be exposed. The analysis will be illustrated by means of two examples of entrepreneurial decision-problems, which have been solved by means of multi-criteria analysis

Incipient Social Groups: An Analysis via In-Vivo Behavioral Tracking

Social psychology is fundamentally the study of individuals in groups, yet there remain basic unanswered questions about group formation, structure, and change. We argue that the problem is methodological. Until recently, there was no way to track who was interacting with whom with anything approximating valid resolution and scale. In the current study we describe a new method that applies recent advances in image-based tracking to study incipient group formation and evolution with experimental precision and control. In this method, which we term "in vivo behavioral tracking," we track individuals' movements with a high definition video camera mounted atop a large field laboratory. We report results of an initial study that quantifies the composition, structure, and size of the incipient groups. We also apply in-vivo spatial tracking to study participants' tendency to cooperate as a function of their embeddedness in those crowds. We find that participants form groups of seven on average, are more likely to approach others of similar attractiveness and (to a lesser extent) gender, and that participants' gender and attractiveness are both associated with their proximity to the spatial center of groups (such that women and attractive individuals are more likely than men and unattractive individuals to end up in the center of their groups). Furthermore, participants' proximity to others early in the study predicted the effort they exerted in a subsequent cooperative task, suggesting that submergence in a crowd may predict social loafing. We conclude that in vivo behavioral tracking is a uniquely powerful new tool for answering longstanding, fundamental questions about group dynamics

Participatory Development of a Forage Grass Cultivar

Perennial forage grasses exist in both nature and agriculture as a highly heterogeneous mixture of genotypes. Extreme environments, fluctuating environments, and severe managements can impose selection pressures that will result in loss of unadapted genotypes. Mortality of unadapted genotypes leads to dominance of fewer highly adapted genotypes which may be useful as superior germplasm in other similar environments

Factors enhancing the choice of higher resource commitment entry modes in international new ventures

The choice of entry mode in foreign markets is an important strategic decision with major consequences for the success of international new ventures (INVs). It is generally accepted that these firms choose relatively low-resource commitment entry modes to operate in foreign markets. Nevertheless, some researchers have suggested that higher resource commitment entry modes in foreign markets also seem to be competitive strategies for INVs. In this study, from a marketing/international entrepreneurship interface perspective and focusing on organizational issues, we center our attention on international market orientation as a neglected yet important factor in INVs’ choice of higher resource commitment entry modes in foreign markets. We suggest that an entrepreneurial orientation and the timing of international entry are important correlates to an international market orientation. We also suggest that the international learning effort of INVs through their international market orientation has a direct, positive impact on the resources these companies commit to their foreign markets through the use of higher resource commitment entry modes. Accordingly, the model proposes a positive effect of entrepreneurial orientation and early international entry on international market orientation which, in turn, is positively related to higher resource commitment entry modes. The hypotheses were tested on country-level data from Spain, using a structural equation model to analyze relationships between the latent variables. This study extends previous international entrepreneurship research, including insights on antecedents of international new ventures’ choice of resource commitment entry modes in foreign markets. The paper also goes further than previous international entrepreneurship research, by addressing the strategic consequences of rapid entry into foreign markets. Additionally, the results of this work encourage international entrepreneurs to look beyond the explicit value of experiential market knowledge to realize the potential value of international market orientation as an antecedent to higher resource commitment entry modes