The sum of the left minus right difference over a 2 s period surrounding this peak is taken as an estimate of lateralization or the laterality index (LI). Within a specified period of interest, the peak difference is located. Using these averages, a difference signal is calculated as the left minus right signals. ![]() Through a series of steps, AVERAGE normalizes the left and right signals, marks potential artefacts, integrates variation due to the cardiac cycle, adjusts for baseline activity, and averages the resulting signals over the series of suitable epochs. (1997) and is demonstrated in their software AVERAGE. The basic processing paradigm was developed by Deppe et al. Language tasks have also been developed for children ( Lohmann et al., 2005 Bishop et al., 2009) and a video description of Bishop et al.’s technique is available ( Bishop et al., 2010). Offline, the recorded blood flow velocity can be analysed to determine an individual's cerebral dominance for a particular task (for a detailed account see Ringelstein et al., 1990). During a series of such trials, Doppler probes, held in place at a position over the temporal window of the skull, insonate the middle cerebral arteries within the left and right hemispheres. Participants are then asked to verbally report the generated words to confirm task compliance and following this, a rest period is required to return blood flow to baseline levels. (1996,1998b), which has also been used successfully in fMRI ( Benson et al., 1999). The standard fTCD paradigm for the assessment of language lateralisation is word generation introduced by Knecht et al. In this paper we report on a newly developed, open source, software package for processing fTCD data. Because fTCD is non-invasive, inexpensive, and portable, it is becoming more popular for psychological research comparing lateralization in special conditions such as Specific Language Impairment, autism, and dyslexia ( Whitehouse and Bishop, 2008 Illingworth and Bishop, 2009), as well as children ( Bishop et al., 2009 Stroobant et al., 2010 Haag et al., 2010). The technique has good test–retest reliability ( Knecht et al., 1998b Stroobant and Vingerhoets, 2001) and provides results which are comparable to the Wada procedure ( Knecht et al., 1998a Knake et al., 2003) as well as fMRI ( Knecht et al., 1999 Somers et al., 2011). Hemispheric lateralization of a cognitive domain is assumed if a greater increase in blood flow velocity can be reliably observed within one hemisphere during a domain specific task. Functional lateralization is assessed by concurrent measurement of blood flow velocity in homologue cerebral arteries in the two hemispheres. One common application for fTCD is the assessment of language lateralization (for a review of applications see Stroobant and Vingerhoets, 2000), which may be for pre-surgical determination or psychological research. While more complex techniques (e.g., functional Magnetic Resonance Imaging, fMRI or Magnetoencephalography) allow for relatively precise localization of activity, fTCD simply measures blood flow in a particular artery. Please consult your device documentation for instructions.Functional transcranial Doppler ultrasonography (fTCD) is a non-invasive imaging technique which assesses changes in blood flow velocity in the cerebral arteries with high temporal resolution ( Aaslid et al., 1982). On mobile devices, you can save the bookmark as an easy-access icon similar to other apps. ![]() For example, if you select "Weather for a location," then select a location, the bookmark will return to your location on your next visit. ![]() You may bookmark the URL to return later to the same view with the selected settings. The URL will automatically update as you select the view and settings. This view is similar to a radar application on a phone that provides radar, current weather, alerts and the forecast for a location. This view combines radar station products into a single layer called a mosaic and storm based alerts. This view provides specific radar products for a selected radar station and storm based alerts. This site is organized into views that provide relevant radar products and weather information for a common task or goal.
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