Multi-modal diffeomorphic demons registration based on point-wise mutual information

In this paper we propose a variational approach for multimodal image registration based on the diffeomorphic demons algorithm. Diffeomorphic demons has proven to be a robust and efficient way for intensity-based image registration. However, the main drawback is that it cannot deal with multiple modalities. We propose to replace the standard demons similarity metric (image intensity differences) by point-wise mutual information (PMI) in the energy function. By comparing the accuracy between our PMI based diffeomorphic demons and the B-Spline based free-form deformation approach (FFD) on simulated deformations, we show the proposed algorithm performs significantly better.

Left posterior parietal theta burst stimulation affects gestural imitation regardless of semantic content.

OBJECTIVE Neuro-imaging studies have suggested that the ability to imitate meaningless and meaningful gestures may differentially depend on superior (SPL) and inferior (IPL) parietal lobule. Therefore, we hypothesized that imaging-guided neuro-navigated continuous theta burst stimulation (cTBS) over left SPL mainly affects meaningless and over left IPL predominantly meaningful gestures. METHODS Twelve healthy subjects participated in this study. High resolution structural MRI was used for imaging guided neuro-navigation cTBS. Participants were targeted with one train of cTBS in three experimental sessions: sham stimulation over vertex and real cTBS over left SPL and IPL, respectively. An imitation task, including 24 meaningless and 24 meaningful gestures, was performed 'offline'. RESULTS cTBS over both left IPL and SPL significantly interfered with gestural imitation. There was no differential effect of SPL and IPL cTBS on gesture type (meaningless versus meaningful). CONCLUSIONS Our findings confirm that left posterior parietal cortex plays a predominant role in gestural imitation. However, the hypothesis based on the dual route model suggesting a differential role of SPL and IPL in the processing of meaningless and meaningful gestures could not be confirmed. SIGNIFICANCE Left SPL and IPL play a common role within the posterior-parietal network in gestural imitation regardless of semantic content.

Different visual exploration of tool-related gestures in left hemisphere brain damaged patients is associated with poor gestural imitation.

According to the direct matching hypothesis, perceived movements automatically activate existing motor components through matching of the perceived gesture and its execution. The aim of the present study was to test the direct matching hypothesis by assessing whether visual exploration behavior correlate with deficits in gestural imitation in left hemisphere damaged (LHD) patients. Eighteen LHD patients and twenty healthy control subjects took part in the study. Gesture imitation performance was measured by the test for upper limb apraxia (TULIA). Visual exploration behavior was measured by an infrared eye-tracking system. Short videos including forty gestures (20 meaningless and 20 communicative gestures) were presented. Cumulative fixation duration was measured in different regions of interest (ROIs), namely the face, the gesturing hand, the body, and the surrounding environment. Compared to healthy subjects, patients fixated significantly less the ROIs comprising the face and the gesturing hand during the exploration of emblematic and tool-related gestures. Moreover, visual exploration of tool-related gestures significantly correlated with tool-related imitation as measured by TULIA in LHD patients. Patients and controls did not differ in the visual exploration of meaningless gestures, and no significant relationships were found between visual exploration behavior and the imitation of emblematic and meaningless gestures in TULIA. The present study thus suggests that altered visual exploration may lead to disturbed imitation of tool related gestures, however not of emblematic and meaningless gestures. Consequently, our findings partially support the direct matching hypothesis.

The Legal Character of Sino-African Tied Aid: Cunning Fox or Wise Dragon?

Paper presented by Charlotte Sieber-Gasser at the African IEL Network Conference, 5th-6th of May 2011, The Mandela Institute, Johannesburg (South Africa) Sino-African trade has seen a fifty-fold increase in the years 1999 to 2008. China became the second most important trading partner for the African economy and already overtook the US as the most important trading partner in some African regions. However, all of this trade is taking place independent from legal regulation by a preferential or other trade agreement. Interestingly, Sino-African trade has seen particular increase in countries that have agreed to tied aid arrangements with China. Taking a closer look at these tied aid arrangements (the so-called Angola-Model) reveals, that some aspects might indeed have a positive effect on Sino-African trade in general. Several grey areas might potentially conflict with WTO-law. However, tied aid is excluded from the GATS, the GATT, and the GPA – in other words, it is outside the sphere of WTO-law. The paper analyses three critical aspects of the Angola-Model version of tied aid with reference to WTO-law, and elaborates the importance of regulating trade-distorting aspects of modern tied aid.