6 research outputs found
Frontal eye field, where art thou? Anatomy, function, and non-invasive manipulation of frontal regions involved in eye movements and associated cognitive operations
The planning, control and execution of eye movements in 3D space relies on a distributed system of cortical and subcortical brain regions. Within this network, the Eye Fields have been described in animals as cortical regions in which electrical stimulation is able to trigger eye movements and influence their latency or accuracy. This review focuses on the Frontal Eye Field (FEF) a âhubâ region located in Humans in the vicinity of the pre-central sulcus and the dorsal-most portion of the superior frontal sulcus. The straightforward localization of the FEF through electrical stimulation in animals is difficult to translate to the healthy human brain, particularly with non-invasive neuroimaging techniques. Hence, in the first part of this review, we describe attempts made to characterize the anatomical localization of this area in the human brain. The outcome of functional Magnetic Resonance Imaging (fMRI), Magneto-encephalography (MEG) and particularly, non-invasive mapping methods such a Transcranial Magnetic Stimulation (TMS) are described and the variability of FEF localization across individuals and mapping techniques are discussed. In the second part of this review, we will address the role of the FEF. We explore its involvement both in the physiology of fixation, saccade, pursuit, and vergence movements and in associated cognitive processes such as attentional orienting, visual awareness and perceptual modulation. Finally in the third part, we review recent evidence suggesting the high level of malleability and plasticity of these regions and associated networks to non-invasive stimulation. The exploratory, diagnostic, and therapeutic interest of such interventions for the modulation and improvement of perception in 3D space are discussed
Forecasts for Dark Energy Measurements with Future HI Surveys
We use two independent methods to forecast the dark energy measurements
achievable by combining future galaxy redshift surveys based on the radio HI
emission line with Cosmic Microwave Background (CMB) data from the {\sl Planck}
satellite. In the first method we focus on the `standard ruler' provided by the
baryon acoustic oscillation (BAO) length scale. In the second method we utilize
additional information encoded in the galaxy power spectrum including galaxy
bias from velocity-space distortions and the growth of cosmic structure. We
find that a radio synthesis array with about 10 per cent of the collecting area
of the Square Kilometre Array (SKA), equipped with a wide () field-of-view, would have the capacity to perform a redshift survey to a maximum redshift and
thereby produce dark energy measurements that are competitive with surveys
likely to be undertaken by optical telescopes around 2015. There would then be
powerful arguments for adding collecting area to such a `Phase-1' SKA because
of the square-law scaling of survey speed with telescope sensitivity for HI
surveys, compared to the linear scaling for optical redshift surveys. The full
SKA telescope should, by performing a HI redshift
survey to around 2020, yield an accurate measurement of
cosmological parameters independent of CMB datasets. Combining CMB ({\sl
Planck}) and galaxy power spectrum (SKA) measurements will drive errors in the
dark energy equation-of-state parameter well below the 1 per cent level.
The major systematic uncertainty in these forecasts is the lack of direct
information about the mass function of high-redshift HI-emitting galaxies.Comment: 19 pages; 2 tables; 18 figures. accepted by MNRA