Biological Pattern Generation: The Cellular and Computational Logic of Networks in Motion

In 1900, Ramón y Cajal advanced the neuron doctrine, defining the neuron as the fundamental signaling unit of the nervous system. Over a century later, neurobiologists address the circuit doctrine: the logic of the core units of neuronal circuitry that control animal behavior. These are circuits that can be called into action for perceptual, conceptual, and motor tasks, and we now need to understand whether there are coherent and overriding principles that govern the design and function of these modules. The discovery of central motor programs has provided crucial insight into the logic of one prototypic set of neural circuits: those that generate motor patterns. In this review, I discuss the mode of operation of these pattern generator networks and consider the neural mechanisms through which they are selected and activated. In addition, I will outline the utility of computational models in analysis of the dynamic actions of these motor networks

The Primacy of Perplexion. Working Architecture through a Distracted Order of Experience. Part II

The first part of this article was published in NA 1995:1 and discusses the notion of "distracted perception" as an adequate way of describing the present condition of architectural experience. The argument is drawn from a reading of texts by Walter Benjamin, Martin Heidegger and Gianni Vattimo, in which the work of art, and in this text architecture, is given the specific role of penetrating this "veil of distraction" to make meaningful communication possible. An analysis of the fictional space in Virginia Woolf's novel Jacob's Room indicates the role of the imagination in understanding and interpreting the physical traces of an absent subject. In this second part the focal point is shifted to the creation of architectural space today, keeping in mind the established interdependence and difference between selves and realities, imagined inhabitants and architectural spaces

The Primacy of Perplexion. Working Architecture through a Distracted Order of Experience. Part I

The issues addressed in this article moves around a central concern of mine, which is, in its essence, ambiguous. It is idealistic in the sense that it does not give up the belief in the possibility of living a responsible life, within a world of individuals and materiality. It is nihilistic in the sense that it avoids accepting any structures that are higher than the individual, that claim the right to, on an extra-human ground, conduct our decisions. The ambiguity is inherent but, I would argue, necessary. The article has been divided into two parts. Part I puts forward the theoretical position on which the further analysis is grounded and discusses the literary space of Virginia Woolf's novel Jacob's Room as a model for a 'distracted order' of reality. Part II discusses Steven Holl and Lebbeus Woods' respective works (texts and projects), focusing on the possibility of making an architecture that communicates through a 'distracted reality' and the two architects' very different approaches to responsible 'professional' action in today's society

A cambrian origin for vertebrate rods

Vertebrates acquired dim light vision when an ancestral cone evolved into the rod photoreceptor at an unknown stage preceding the last common ancestor of extant jawed vertebrates (~420 million years ago Ma). The jawless lampreys provide a unique opportunity to constrain the timing of this advance, as their line diverged ~505 Ma and later displayed high morphological stability. We recorded with patch electrodes the inner segment photovoltages and with suction electrodes the outer segment photocurrents of Lampetra fluviatilis retinal photoreceptors. Several key functional features of jawed vertebrate rods are present in their phylogenetically homologous photoreceptors in lamprey: crucially, the efficient amplification of the effect of single photons, measured by multiple parameters, and the flow of rod signals into cones. These results make convergent evolution in the jawless and jawed vertebrate lines unlikely and indicate an early origin of rods, implying strong selective pressure toward dim light vision in Cambrian ecosystems

Independent circuits in the basal ganglia for the evaluation and selection of actions

The basal ganglia are critical for selecting actions and evaluating their outcome. Although the circuitry for selection is well understood, how these nuclei evaluate the outcome of actions is unknown. Here, we show in lamprey that a separate evaluation circuit, which regulates the habenula-projecting globus pallidus (GPh) neurons, exists within the basal ganglia. The GPh neurons are glutamatergic and can drive the activity of the lateral habenula, which, in turn, provides an indirect inhibitory influence on midbrain dopamine neurons. We show that GPh neurons receive inhibitory input from the striosomal compartment of the striatum. The striosomal input can reduce the excitatory drive to the lateral habenula and, consequently, decrease the inhibition onto the dopaminergic system. Dopaminergic neurons, in turn, provide feedback that inhibits the GPh. In addition, GPh neurons receive direct projections from the pallium (cortex in mammals), which can increase the GPh activity to drive the lateral habenula to increase the inhibition of the neuromodulatory systems. This circuitry, thus, differs markedly from the "direct" and "indirect" pathways that regulate the pallidal (e.g., globus pallidus) output nuclei involved in the control of motion. Our results show that a distinct reward-evaluation circuit exists within the basal ganglia, in parallel to the direct and indirect pathways, which select actions. Our results suggest that these circuits are part of the fundamental blueprint that all vertebrates use to select actions and evaluate their outcome