Investigating directed influences between activated brain areas in a motor-response task using fMRI

Localization of cognitive processes is a strength of functional neuroimaging. However, information about functional interactions between brain areas is crucial for a deeper understanding of brain function. We applied vector autoregressive modeling in the context of Granger causality as a method to analyze directed connectivity in a standard event-related fMRI study using a simple auditory-motor paradigm. The basic idea is to use temporal information in stochastic time series of a brain region in order to predict signal time courses in other brain regions. Thus, we predicted that the method should demonstrate causal influence of the auditory cortex and the supplementary motor area (SMA) on primary motor cortex. Eleven right-handed healthy female subjects were instructed to press a ball with either their left or their right hand when hearing the command "Ieft" or "right" in the scanner. Influence to the left motor cortex was found from bilateral auditory cortex as well as from the SMA in 9 of I I subjects. Granger causality to the right motor cortex existed from bilateral auditory cortex in 5 and from SMA in 6 subjects. Granger causality to the SMA existed from right auditory cortex in 7 subjects and from left auditory cortex in 8 subjects. Our findings in a simple task show that even under suboptimal circumstances (a relatively long TR of 2440 ms), Granger causality can be a useful tool to explore effective connectivity. Temporally optimized scanning should increase that potential

Investigating directed influences between activated brain areas in a motor-response task using fMRI

Localization of cognitive processes is a strength of functional neuroimaging. However, information about functional interactions between brain areas is crucial for a deeper understanding of brain function. We applied vector autoregressive modeling in the context of Granger causality as a method to analyze directed connectivity in a standard event-related fMRI study using a simple auditory-motor paradigm. The basic idea is to use temporal information in stochastic time series of a brain region in order to predict signal time courses in other brain regions. Thus, we predicted that the method should demonstrate causal influence of the auditory cortex and the supplementary motor area (SMA) on primary motor cortex. Eleven right-handed healthy female subjects were instructed to press a ball with either their left or their right hand when hearing the command "Ieft" or "right" in the scanner. Influence to the left motor cortex was found from bilateral auditory cortex as well as from the SMA in 9 of I I subjects. Granger causality to the right motor cortex existed from bilateral auditory cortex in 5 and from SMA in 6 subjects. Granger causality to the SMA existed from right auditory cortex in 7 subjects and from left auditory cortex in 8 subjects. Our findings in a simple task show that even under suboptimal circumstances (a relatively long TR of 2440 ms), Granger causality can be a useful tool to explore effective connectivity. Temporally optimized scanning should increase that potential

Die bioelektronische Schnittstelle implantierbarer Hörsysteme

The distinct feeling of wanting to act and thereby causing our own actions is crucial to our self-perception as free human agents. Disturbances of the link between intention and action occur in several disorders. Little is known, however, about the neural correlates of wanting or intending to act. To investigate these for simple voluntary movements, we used a paradigm involving hypnotic paralysis and functional magnetic resonance imaging. Eight healthy women were instructed to sequentially perform left and right hand movements during a normal condition, as well as during simulated weakness, simulated paralysis and hypnotic paralysis of the right hand. Right frontopolar cortex was selectively hypoactivated for attempted right hand movement during simulated paralysis while it was active in all other conditions. Since simulated paralysis was the only condition lacking an intention to move, the activation in frontopolar cortex might be related to the intention or volition to move

Food security in rural areas of Limpopo Province, South Africa

Publication of this article was funded by the Stellenbosch University Open Access Fund.The original publication is available at http://link.springer.com/journal/12571Although South Africa is food secure as a nation, many households remain food insecure. The government has recognized several key food security challenges in the Integrated Food Security Strategy (IFSS). However, South Africa still lacks specific and accepted methods to measure food security and currently has no regulated way of monitoring the food security status of its population. This article reports on an investigation into the food security situation of rural households in the Limpopo Province. Qualitative and quantitative data were gathered across five districts in the province. The study sample eventually involved 599 households in the rural areas of Limpopo. This allowed a thorough description of household characteristics and livelihoods and an assessment of the food security and poverty levels in the area. The findings showed that 53 % of the sampled rural households declared themselves to be severely food insecure. Multivariate analyses were used to identify the main food security status. These determinants were mainly human capital (education, household size and dependency ratio), household income and district in which the households were situated. The findings indicated that policy priorities should be focused on the promotion of rural education and creating an enabling environment for the rural labour market.Stellenbosch UniversityPublishers' versio

Report on survey in Sekhukhune to pilot the development of a food insecurity and vulnerability modelling system (FIVIMS) for South Africa

Commissioned by the FIVIMS Consortium, MarchThe data has been analysed and presented in this report to enable potential users of FIVIMS to understand vulnerability and food insecurity in Sekhukhune through the description and characterisation of diverse livelihood strategies and the measurement of key food security outcomes