Properties of Visual Field Maps in Health and Disease

The visual world that surrounds us is represented in and processed by multiple topographically organised maps in the human brain. The organising principle underlying these retinotopic maps is also apparent across other sensory modalities and appears highly conserved across species. Moreover, the template for these visual maps is laid down during development, without the need for visual experience. This thesis binds and summarises seven publications describing work to characterise the functional properties of visual maps in the human brain. Initially, we describe TMS and fMRI measurements designed to probe the functional specificity of two spatially distinct but spatially adjacent maps, LO-1 and LO-2. Concurrently I developed software (visualisation tools) for precise dissection of these areas and to more broadly facilitate the visualisation of neuroimaging data. Our experiment revealed a double dissociation in the functional specificity of these areas, with preferential processing of orientation and shape information by LO-1 and LO-2, respectively. We then used fMRI to examine the effect of spatial attention on the responses measured from visual field maps. We showed that attention modulated visual responses by both enhancing attended locations and suppressing unattended locations; these effects were evident in the maps of early visual cortex and subcortical structures including the lateral geniculate and pulvinar nuclei. Finally, we examined the properties of visual field maps in patients with retinal lesions. Although maps can be abnormally organised with certain congenital visual deficits, we asked whether normally developed maps were able to reorganise when input to them is lost later in life, specifically due to central retinal lesions. Our measurements showed no evidence of reorganisation in the maps of patients with macular degeneration: the extent of activity measured in these maps was both highly predictable based on individual retinal lesions and could be reliably simulated in normally sighted individuals

Goddard's Astrophysics Science Divsion Annual Report 2014

The Astrophysics Science Division (ASD, Code 660) is one of the world's largest and most diverse astronomical organizations. Space flight missions are conceived, built and launched to observe the entire range of the electromagnetic spectrum, from gamma rays to centimeter waves. In addition, experiments are flown to gather data on high-energy cosmic rays, and plans are being made to detect gravitational radiation from space-borne missions. To enable these missions, we have vigorous programs of instrument and detector development. Division scientists also carry out preparatory theoretical work and subsequent data analysis and modeling. In addition to space flight missions, we have a vibrant suborbital program with numerous sounding rocket and balloon payloads in development or operation. The ASD is organized into five labs: the Astroparticle Physics Lab, the X-ray Astrophysics Lab, the Gravitational Astrophysics Lab, the Observational Cosmology Lab, and the Exoplanets and Stellar Astrophysics Lab. The High Energy Astrophysics Science Archive Research Center (HEASARC) is an Office at the Division level. Approximately 400 scientists and engineers work in ASD. Of these, 80 are civil servant scientists, while the rest are resident university-based scientists, contractors, postdoctoral fellows, graduate students, and administrative staff. We currently operate the Swift Explorer mission and the Fermi Gamma-ray Space Telescope. In addition, we provide data archiving and operational support for the XMM mission (jointly with ESA) and the Suzaku mission (with JAXA). We are also a partner with Caltech on the NuSTAR mission. The Hubble Space Telescope Project is headquartered at Goddard, and ASD provides Project Scientists to oversee operations at the Space Telescope Science Institute. Projects in development include the Neutron Interior Composition Explorer (NICER) mission, an X-ray timing experiment for the International Space Station; the Transiting Exoplanet Sky Survey (TESS) Explorer mission, in collaboration with MIT (Ricker, PI); the Soft X-ray Spectrometer (SXS) for the Astro-H mission in collaboration with JAXA, and the James Webb Space Telescope (JWST). The Wide-Field Infrared Survey Telescope (WFIRST), the highest ranked mission in the 2010 decadal survey, is in a pre-phase A study, and we are supplying study scientists for that mission

On Electronic Transport through Single Molecules in Nanostructures

Diese Arbeit fasst die Ergebnisse von Transportexperimenten anunterschiedlichen Nanostrukturen zusammen. Zum Einen wird ein Ansatz zur Kontaktierung und Charakterisierung von Makromolekülen auf der Grundlage von Feedback-kontrollierter Elektromigration beschrieben und analysiert. Zum Anderen werden Tieftemperaturmessungen an einem System von Kohlenstoffnanoröhrchen, welches Charakteristiken von untereinanderkapazitiv gekoppelten Quantenpunkten zeigte, präsentiert und interpretiert

Characterising pattern asymmetry in pigmented skin lesions

Abstract. In clinical diagnosis of pigmented skin lesions asymmetric pigmentation is often indicative of melanoma. This paper describes a method and measures for characterizing lesion symmetry. The estimate of mirror symmetry is computed first for a number of axes at different degrees of rotation with respect to the lesion centre. The statistics of these estimates are the used to assess the overall symmetry. The method is applied to three different lesion representations showing the overall pigmentation, the pigmentation pattern, and the pattern of dermal melanin. The best measure is a 100% sensitive and 96% specific indicator of melanoma on a test set of 33 lesions, with a separate training set consisting of 66 lesions