Model based analysis of fMRI-data: Applying the sSoTS framework to the neural basic of preview search.

The current work aims to unveil the neural circuits under- lying visual search over time and space by using a model-based analysis of behavioural and fMRI data. It has been suggested by Watson and Humphreys [31] that the prioritization of new stimuli presented in our visual field can be helped by the active ignoring of old items, a process they termed visual marking. Studies using fMRI link the marking pro- cess with activation in superior parietal areas and the precuneus [4, 18, 27, 26]. Marking has been simulated previously using a neural-level ac- count of search, the spiking Search over Time and Space (sSoTS) model, which incorporates inhibitory as well as excitatory mechanisms to guide visual selection. Here we used sSoTS to help decompose the fMRI signals found in a preview search procedure, when participants search for a new target whilst ignoring old distractors. The time course of activity linked to inhibitory and excitatory processes in the model was used as a regres- sor for the fMRI data. The results showed that different neural networks were correlated with top-down excitation and top-down inhibition in the model, enabling us to fractionate brain regions previously linked to vi- sual marking. We discuss the contribution of model-based analysis for decomposing fMRI data

The spiking search over time and space model (sSoTS): Simulating dual task experiments and the temporal dynamics of preview search

The visual information we receive in the real world is usually prioritized through time as well as space. Evidence presented by Watson and Humphreys [18] supports the view that new information in search tasks is prioritised by (amongst other processes) active ignoring of old items - a process they termed visual marking. In this work we present, an explicit computational model of visual marking using biologically plausible activation functions. The "spiking search over time and space" model (sSoTS) incorporates different synaptic components (NMDA, AMPA, GABA) and a frequency adaptation mechanism based on [Ca2 +] sensitive K+ current. This frequency adaptation current when coupled with a process of active inhibition applied to old items, leads to old items being de-prioritised (and new items prioritised) across time in search. Furthermore, sSoTS can simulate the temporal dynamics of preview search [13] and dual task experimental results [12]. The results indicate that the sSoTS model can provide a biologically plausible account of human search over time as well as space. © Springer-Verlag Berlin Heidelberg 2007

Unexpected and growing interest in land investments? The Asian case

The aim of this chapter is to provide an Asian perspective on land investments with particular reference to the European position in terms of land acquisition. At first, the paper recalls the relevance that land holds as a distinct factor of production and consumption. Then, it investigates the different ways employed to define the recent phenomenon of land-grabbing in the increasing literature review. In order to contribute to the discussion on the issue, the second part of the paper is devoted to the examination of the Asian case. Furthermore, it analyses both the direct and the indirect role played by the European Union in influencing and enhancing the phenomenon of land-grabbing in Asia. The chapter concludes with observations and proposals on the impact of land-grabbing