Mechanism of Neural Interference

This paper proposes neural mechanisms of transcranial magnetic stimulation (TMS). TMS can stimulate the brain non-invasively through a brief magnetic pulse delivered by a coil placed on the scalp, interfering with specific cortical functions with a high temporal resolution. Due to these advantages, TMS has been a popular experimental tool in various neuroscience fields. However, the neural mechanisms underlying TMSinduced interference are still unknown; a theoretical basis for TMS has not been developed. This paper provides computational evidence that inhibitory interactions in a neural population, not an isolated single neuron, play a critical role in yielding the neural interference induced by TMS

Two–Component Deformable Model

We present an approach for automatic segmentation of the midbrain and substantia nigra in 2D transcranial sonographies (TCS). It combines principles from both deformable shapes and Active Contour Models (ACM). A set of ACM is coupled with a two–component Finite Element Model of the midbrain anatomy, and this shape representation is used in a deformable shape search for the midbrain. A successful search allows automatic initialisation of the ACM for the exact segmentation of the substantia nigra. For improving convergence independent from the initial estimate, deformations are driven by a classifier that distinguishes regional image features, and in this way steers the deformation to inter–tissue boundaries. Experimental results are promising and show that our approach can segment the midbrain from TCS automatically and accurately, compared with other image segmentation methods and manual segmentation.

Paradoxical embolization: a potential cause of cerebral damage in Alzheimer's disease?

Item does not contain fulltextBACKGROUND: There are considerable overlaps between vascular dementia and Alzheimer's disease (AD), with a suggestion that cerebrovascular disease (CVD) contributes to the neurodegenerative pathology of AD. Paradoxical embolization of venous emboli into the systemic circulation through a venous to arterial circulation shunt (v-aCS), the most commonly a patent foramen ovale (PFO), is known to cause cryptogenic stroke in younger people. We reviewed the potential role of paradoxical embolization in AD. METHODS: A review of the literature on paradoxical embolization in neurological disorders and techniques to detect v-aCS and PFO, supplemented by data from our own studies. RESULTS: Before our research, the role of paradoxical embolism in dementia had not been studied. The potential role of embolization in cerebral damage was highlighted by studies in patients undergoing coronary artery bypass or carotid surgery. Paradoxical embolization was found to occur in patients with cryptogenic stroke, migraine, decompression sickles and during hip surgery. The methods for detecting v-aCS or PFO had not been standardized. We found 'significant' v-aCS (equivalent to PFO) in 32% of AD patients compared with 22% of controls, but the study was not sufficiently powered to test the statistic significance of this difference. In AD, there was evidence of an association between 'significant' v-aCS and the severity of white matter hyperintensities on magnetic resonance imaging (MRI). CONCLUSION: Paradoxical embolization through a v-aCS may be a potentially preventable or treatable cause of CVD in AD