An Experiment on Behavior Generalization and the Emergence of Linguistic Compositionality in Evolving Robots

Populations of simulated agents controlled by dynamical neural networks are trained by artificial evolution to access linguistic instructions and to execute them by indicating, touching or moving specific target objects. During training the agent experiences only a subset of all object/action pairs. During post-evaluation, some of the successful agents proved to be able to access and execute also linguistic instructions not experienced during training. This owes to the development of a semantic space, grounded in the sensory motor capability of the agent and organised in a systematised way in order to facilitate linguistic compositionality and behavioural generalisation. Compositionality seems to be underpinned by a capability of the agents to access and execute the instructions by temporally decomposing their linguistic and behavioural aspects into their constituent parts (i.e., finding the target object and executing the required action). The comparison between two experimental conditions, in one of which the agents are required to ignore rather than to indicate objects, shows that the composition of the behavioural set significantly influences the development of compositional semantic structures

Chapter 3: Chemical Exchange Saturation Transfer (CEST) Contrast Agents

This chapter considers the development of safe and sensitive chemical exchange saturation transfer (CEST) contrast agents for MRI. CEST MRI is a contrast mechanism that enables the amplified detection of solutes based on the exchange of their labile protons with water. This chapter describes the general theory of CEST agents and their practical uses. Consideration is then given to the acquisition of CEST spectra, including instrumentation, sample conditions and data analysis, as well as the determination of the number of inner-sphere water molecules (q) for metal-based CEST complexes and proton exchange rates (kex). The preparation and characterization of paramagnetic micelles and liposomes is also discussed as well as the acquisition of CEST MR phantom images