לוח שנה משולב

The coupling between the spin of an electron and its momentum is recognized to generate a variety of new phases in condensed matter systems. For example, in symmetry broken states, spin-orbit coupling permits exotic low energy excitations such as skyrmions in helimagnets. Recently it was shown that when electrons pass through organic helix-shaped molecules, one spin type passes through much more easily. In other words, although these molecules are not magnetic they act as a spin filter. In my talk I will discuss a potential origin of this surprising effect. I will explain how a strong spin-orbit coupling, which is necessary for spin filtering, emerges in such molecules due to their helical geometry, and how it gives rise to spin dependent transport.

Abstract: Arm amputation provides a powerful model for studying plasticity, as it results in massive input and output loss consequential to losing a hand. Amputation also leads to profound changes in behaviour, driven by individuals’ need to compensate for severe disability (adaptive behaviour). Despite this strong behavioural pressure, research on amputation has been largely restricted to deprivation-driven (and supposedly passive) brain reorganisation, with little regard for the potential interaction between deprivation and behavioural related plasticity. As a consequence, sensory deprivation is widely held to cause maladaptive plasticity, resulting in phantom pain. Using a range of neuroimaging approaches I examine the extent to which experience modulates brain structure and function in amputees and individuals with congenital hand absence. I present evidence to challenge the proposed link between cortical reorganisation and phantom pain, and instead demonstrate preservation of topographic representations of the missing (‘phantom’) hand. I will show that phantom pain is associated with maintained representation of the phantom hand as opposed to brain plasticity, with potential implications on future treatment. Instead I provide new evidence that adaptive behaviour leads to extensive reorganisation, such that the limb engaging in compensation for disability takes over the cortical territory of the missing hand. In amputees, this process of adaptive plasticity occurs well beyond the traditionally conceptualised “critical period”. Finally, I provide new evidence for the relationship between lateralised limb-use patterns and lateralised structural and functional organisation in the resting brain. Based on this evidence, I suggest that plasticity in amputees is experience-dependant, and is not inherently maladaptive.