Transient Dynamics versus Fixed Points in Odor Representations by Locust Antennal Lobe Projection Neurons

SummaryProjection neurons (PNs) in the locust antennal lobe exhibit odor-specific dynamic responses. We studied a PN population, stimulated with five odorants and pulse durations between 0.3 and 10 s. Odor representations were characterized as time series of vectors of PN activity, constructed from the firing rates of all PNs in successive 50 ms time bins. Odor representations by the PN population can be described as trajectories in PN state space with three main phases: an on transient, lasting 1–2 s; a fixed point, stable for at least 8 s; and an off transient, lasting a few seconds as activity returns to baseline. Whereas all three phases are odor specific, optimal stimulus separation occurred during the transients rather than the fixed points. In addition, the PNs’ own target neurons respond least when their PN-population input stabilized at a fixed point. Steady-state measures of activity thus seem inappropriate to understand the neural code in this system

Interaction dynamics and autonomy in cognitive systems

The concept of autonomy is of crucial importance for understanding life and cognition. Whereas cellular and organismic autonomy is based in the self-production of the material infrastructure sustaining the existence of living beings as such, we are interested in how biological autonomy can be expanded into forms of autonomous agency, where autonomy as a form of organization is extended into the behaviour of an agent in interaction with its environment (and not its material self-production). In this thesis, we focus on the development of operational models of sensorimotor agency, exploring the construction of a domain of interactions creating a dynamical interface between agent and environment. We present two main contributions to the study of autonomous agency: First, we contribute to the development of a modelling route for testing, comparing and validating hypotheses about neurocognitive autonomy. Through the design and analysis of specific neurodynamical models embedded in robotic agents, we explore how an agent is constituted in a sensorimotor space as an autonomous entity able to adaptively sustain its own organization. Using two simulation models and different dynamical analysis and measurement of complex patterns in their behaviour, we are able to tackle some theoretical obstacles preventing the understanding of sensorimotor autonomy, and to generate new predictions about the nature of autonomous agency in the neurocognitive domain. Second, we explore the extension of sensorimotor forms of autonomy into the social realm. We analyse two cases from an experimental perspective: the constitution of a collective subject in a sensorimotor social interactive task, and the emergence of an autonomous social identity in a large-scale technologically-mediated social system. Through the analysis of coordination mechanisms and emergent complex patterns, we are able to gather experimental evidence indicating that in some cases social autonomy might emerge based on mechanisms of coordinated sensorimotor activity and interaction, constituting forms of collective autonomous agency

What Permits Small Firms to Compete in High-Tech Industries? Inter-Organizational Knowledge Creation in the Taiwanese Computer Industry

This paper addresses a puzzle related to firm size and competition. Since Stephen Hymer´s pioneering contribution (Hymer, 1960/1976), theories of the firm implicitly assume that only large, diversified multinational enterprises can compete in industries that combine high capital intensity, high knowledge-intensity and a high degree of internationalization. Small firms, by definition, have limited resources and capabilities and are unlikely to possess substantial ownership advantages. They also have a limited capacity to influence and shape the development of markets, market structure and technological change. One would thus expect that they are ill-equipped to compete in a knowledge-intensive industry that is highly globalized. Taiwan’s experience in the computer industry tells a different story: despite the dominance of small- and medium-sized enterprises (SMEs), Taiwan successfully competes in the international market for PC-related products, key components and knowledge-intensive services. The paper inquires into how this was possible. It is argued that organizational innovations related to the creation of knowledge are of critical importance. Taiwanese computer firms were able to develop their own distinctive approach: due to their initially very narrow knowledge base, access to external sources of knowledge has been an essential prerequisite for their knowledge creation. Such “inter-organizational knowledge creation” (Nonaka and Takeuchi, 1995) was facilitated by two factors: active, yet selective and continuously adjusted industrial development policies; and a variety of linkages with large Taiwanese business groups, foreign sales and manufacturing affiliates and an early participation in international production networks established by foreign electronics companies. A novel contribution of this paper is its focus on inter-organizational knowledge creation. I first describe Taiwan´s achievements in the computer industry. The dominance of SMEs and their role as a source of flexibility is documented in part II. Part III describes some policy innovations that have shaped the process of knowledge creation. The rest of the paper inquires how inter-organizational knowledge creation has benefited from a variety of linkages with large domestic and foreign firms; I also address some industrial upgrading requirements that result from this peculiar type of knowledge creation.knowledge creation; learning; small firms; networks; firm strategy; industrial policies;

Physics of Microswimmers - Single Particle Motion and Collective Behavior

Locomotion and transport of microorganisms in fluids is an essential aspect of life. Search for food, orientation toward light, spreading of off-spring, and the formation of colonies are only possible due to locomotion. Swimming at the microscale occurs at low Reynolds numbers, where fluid friction and viscosity dominates over inertia. Here, evolution achieved propulsion mechanisms, which overcome and even exploit drag. Prominent propulsion mechanisms are rotating helical flagella, exploited by many bacteria, and snake-like or whip-like motion of eukaryotic flagella, utilized by sperm and algae. For artificial microswimmers, alternative concepts to convert chemical energy or heat into directed motion can be employed, which are potentially more efficient. The dynamics of microswimmers comprises many facets, which are all required to achieve locomotion. In this article, we review the physics of locomotion of biological and synthetic microswimmers, and the collective behavior of their assemblies. Starting from individual microswimmers, we describe the various propulsion mechanism of biological and synthetic systems and address the hydrodynamic aspects of swimming. This comprises synchronization and the concerted beating of flagella and cilia. In addition, the swimming behavior next to surfaces is examined. Finally, collective and cooperate phenomena of various types of isotropic and anisotropic swimmers with and without hydrodynamic interactions are discussed.Comment: 54 pages, 59 figures, review article, Reports of Progress in Physics (to appear

Biologically Plausible Cortical Hierarchical-Classifier Circuit Extensions in Spiking Neurons

Hierarchical categorization inter-leaved with sequence recognition of incoming stimuli in the mammalian brain is theorized to be performed by circuits composed of the thalamus and the six-layer cortex. Using these circuits, the cortex is thought to learn a ‘brain grammar’ composed of recursive sequences of categories. A thalamo-cortical, hierarchical classification and sequence learning “Core” circuit implemented as a linear matrix simulation and was published by Rodriguez, Whitson & Granger in 2004. In the brain, these functions are implemented by cortical and thalamic circuits composed of recurrently-connected, spiking neurons. The Neural Engineering Framework (NEF) (Eliasmith & Anderson, 2003) allows for the construction of large-scale biologically plausible neural networks. Existing NEF models of the basal-ganglia and the thalamus exist but to the best of our knowledge there does not exist an integrated, spiking-neuron, cortical-thalamic-Core network model. We construct a more biologically-plausible version of the hierarchical-classification function of the Core circuit using leaky-integrate-and-fire neurons which performs progressive visual classification of static image sequences relying on the neural activity levels to trigger the progressive classification of the stimulus. We proceed by implementing a recurrent NEF model of the cortical-thalamic Core circuit and then test the resulting model on the hierarchical categorization of images

Class, power, and patronage: the landed elite and politics in Pakistani Punjab

Following their conquest of Punjab, the British erected an administrative apparatus that relied heavily upon the support of the province’s powerful landed elite. The relationship between the two was one of mutual benefit, with the British using their landed allies to ensure the maintenance of order and effective economic accumulation in exchange for state patronage. Over a century and a half later, the politics of Pakistani Punjab continues to be dominated by landowning politicians, despite significant societal changes that could have potentially eroded their power. In order to answer the question of why this is so, this thesis uses a historical institutionalist approach to argue that the administrative framework emerging out of the initial bargain between the colonial state and the landed classes gave rise to a path-dependent process of institutional development in Punjab that allowed the latter to increasingly entrench themselves within the political order during the colonial and post-colonial periods. In doing so, the landed elite were also able to reinforce their bargain with the colonial state and, after independence, the Pakistani military establishment, perpetuating a relationship that facilitated the pursuit of the interests of the actors involved. In order to account for this path-dependent process of institutional development, this thesis treats the initial period of colonial rule in Punjab as a ‘critical juncture’, tracing the factors that led the British to rely on the landed elite for support, and enter into the bargain between the two actors that drove subsequent institutional developments. The thesis then explores the mechanisms used to perpetuate this arrangement over time, focusing in particular on the use, by the state and the landed elite, of legislative interventions, bureaucratic power, and electoral politics, to reinforce and reproduce the institutional framework of politics in Punjab. Finally, the thesis also looks at points in time during which this dominant institutional path has been challenged, albeit unsuccessfully, with a view towards understanding both the circumstances under which such challenges can emerge, and the lessons that can be learnt from these episodes with regards to the prospects for the creation of a democratic and participatory politics in the province