Psyscope reviews software#

This also highlights that, despite the good fit of the canonical HRF for most situations, the true HRF is known to present some variability. Occasionally, an initial dip is reported but its origin and implications are still under debate (Hu and Yacoub, 2012).

Psyscope reviews software#

Typically, fMRI software model the HRF with a set of gamma functions, commonly designated by canonical HRF, that is characterized by a gradual rise, peaking ~5вЂ“6 s after the stimulus, followed by a return to the baseline (about 12 s after the stimulus) and a small undershoot before stabilizing again, 25вЂ“30 s after (Figure вЂ‹ (Figure1A) 1A) (Miezin et al., 2000 Buxton et al., 2004 Handwerker et al., 2012). The BOLD signal can be characterized by the shape of this HRF, which reflects its vascular origin. This mechanism, which is a function of the properties of the local vascular network, is referred to as the hemodynamic response function (HRF) and has a time course of several seconds after the increase in activity. It is important to note that as local neuronal activity increases, there is an intrinsic delay before regional vasodilation occurs and flow increases. The increase in the oxy-/deoxy-hemoglobin ratio leads to an increase in the MRI signal compared to that of the surrounding tissue. The local influx of oxygenated blood results in a net increase in the balance of oxygenated arterial blood to deoxygenated venous blood (associated with elevated deoxyhemoglobin). Information transfer between neurons is a metabolically demanding process, which requires an increased flow of oxygenated blood, oxyhemoglobin. The resultant indirect determination of brain function is typically represented as a statistical map which reflects regional activity. In summary, the basic concept underlying all fMRI measurement is that an increase in local neuronal activity stimulates both higher energy consumption and increased blood flow. Functional MRI principles and basic concepts have been extensively described and reviewed in the literature (Le Bihan, 1996 Gore, 2003 Amaro and Barker, 2006 Norris, 2006 Logothetis, 2008 Buxton, 2009 Faro and Mohamed, 2010 Ulmer and Jansen, 2010 Poldrack et al., 2011 Bandettini, 2012b UДџurbil and Ogawa, 2015). The magnitude of the BOLD signal is an indirect measure of neuronal activity, and is a composite which reflects changes in regional cerebral blood flow, volume, and oxygenation. Amongst its attributes are high spatial resolution, signal reliability, robustness, and reproducibility.ДЇunctional brain mapping is most commonly performed using the venous blood oxygenation level-dependent (BOLD) contrast technique (Ogawa and Lee, 1990 Ogawa et al., 1990a, b Ogawa, 2012). It is a fundamentally non-invasive method, and one which provides a method to assess brain function with unparalleled spatial specificity.

Introduced in the early nineties, functional Magnetic Resonance Imaging (fMRI) (Bandettini et al., 1992 Kwong et al., 1992 Ogawa et al., 1992 Bandettini, 2012a Kwong, 2012) is a variant of conventional Magnetic Resonance Imaging (MRI) intended to measure brain activity and connectivity.

We have developed this guide both to help those new to the technique to overcome the most critical difficulties in its use, as well as to serve as a resource for the neuroimaging community. Herein we provide a straightforward guide designed to address, for each of the major stages, the techniques, and tools involved in the process. In practice, the researcher/clinician must choose, from many available options, the most suitable software tool for each stage of the fMRI analysis pipeline. However, multiple technical considerations (ranging from specifics of paradigm design to imaging artifacts, complex protocol definition, and multitude of processing and methods of analysis, as well as intrinsic methodological limitations) must be considered and addressed in order to optimize fMRI analysis and to arrive at the most accurate and grounded interpretation of the data. Functional Magnetic Resonance Imaging (fMRI) studies have become increasingly popular both with clinicians and researchers as they are capable of providing unique insights into brain functions.