Upshot: Albeit mostly supportive of our work, the commentaries we received highlighted a few points that deserve additional explanation, with regard to the notion of learning in our model, the relationship between our model and the brain, as well as the notion of anticipation. This open discussion emphasizes the need for toy computer models, to fuel theoretical discussion and prevent business-as-usual from getting in the way of new ideas.

Context: Constructivist approaches to cognition have mostly been descriptive, and now face the challenge of specifying the mechanisms that may support the acquisition of knowledge. Departing from cognitivism, however, requires the development of a new functional framework that will support causal, powerful and goal-directed behavior in the context of the interaction between the organism and the environment. Problem: The properties affecting the computational power of this interaction are, however, unclear, and may include partial information from the environment, exploration, distributed processing (...) and aggregation of information, emergence of knowledge and directedness towards relevant information. Method: We posit that one path towards such a framework may be grounded in these properties, supported by dynamical systems. To assess this hypothesis, we describe computational models inspired from swarm intelligence, which we use as a metaphor to explore the practical implications of the properties highlighted. Results: Our results demonstrate that these properties may serve as the basis for complex operations, yielding the elaboration of knowledge and goal-directed behavior. Implications: This work highlights aspects of interaction that we believe ought to be taken into account when characterizing the possible mechanisms underlying cognition. The scope of the models we describe cannot go beyond that of a metaphor, however, and future work, theoretical and experimental, is required for further insight into the functional role of interaction with the environment for the elaboration of complex behavior. Constructivist content: Inspiration for this work stems from the constructivist impetus to account for knowledge acquisition based on interaction. (shrink)

Deep brain stimulation — a novel surgical procedure — is emerging as a treatment of last resort for people diagnosed with neuropsychiatric disorders such as severe obsessive-compulsive disorder. The US Food and Drug Administration granted a so-called humanitarian device exemption to allow patients to access this intervention, thereby removing the requirement for a clinical trial of the appropriate size and statistical power. Bypassing the rigors of such trials puts patients at risk, limits opportunities for scientific discovery, and gives device manufacturers (...) unique marketing opportunities. We argue that Congress and federal regulators should revisit the humanitarian device exemption to ensure that it is not used to sidestep careful research that can offer valuable data with appropriate patient safeguards. (shrink)

Using covariant derivatives and the operator definitions of quantum mechanics, gauge invariant Proca and Lehnert equations are derived and the Lorenz condition is eliminated in U(1) invariant electrodynamics. It is shown that the structure of the gauge invariant Lehnert equation is the same in an O(3) invariant theory of electrodynamics.