A major methodological challenge of functional near-infrared spectroscopy (fNIRS) is its high sensitivity to haemodynamic fluctuations in the scalp. Superficial fluctuations contribute on the one hand to the physiological noise of fNIRS, impairing the signal-to-noise ratio, and may on the other hand be erroneously attributed to cerebral changes, leading to false positives in fNIRS experiments. Here we explore the localisation, time course and physiological origin of task-evoked superficial signals in fNIRS and present a method to separate them from cortical signals. We used complementary fNIRS, fMRI, MR-angiography and peripheral physiological measurements (blood pressure, heart rate, skin conductance and skin blood flow) to study activation in the frontal lobe during a continuous performance task. The General Linear Model (GLM) was applied to analyse the fNIRS data, which included an additional predictor to account for systemic changes in the skin.We found that skin blood volume strongly depends on the cognitive state and that sources of task-evoked systemic signals in fNIRS are co-localized with veins draining the scalp. Task-evoked superficial artefacts were mainly observed in concentration changes of oxygenated haemoglobin and could be effectively separated from cerebral signals by GLM analysis. Based on temporal correlation of fNIRS and fMRI signals with peripheral physiological measurements we conclude that the physiological origin of the systemic artefact is a task-evoked sympathetic arterial vasoconstriction followed by a decrease in venous volume.Since changes in sympathetic outflow accompany almost any cognitive and emotional process, we expect scalp vessel artefacts to be present in a wide range of fNIRS settings used in neurocognitive research. Therefore a careful separation of fNIRS signals originating from activated brain and from scalp is a necessary precondition for unbiased fNIRS brain activation maps.
Basic research has established a strong relationship between stimulus induced human motivation for approach-related behavior and left-frontal electrophysiological activity in the alpha band, i.e. frontal alpha asymmetry (FAA). Since approach motivation is also of interest for various fields of applied research, several recent studies investigated the usefulness of FAA as a diagnostic tool of stimulus induced motivational changes. The present review introduces the theory and the methods commonly used in approach/ withdrawal motivation research, and summarizes work on applied FAA with a focus on product design, marketing, brain-computer communication and mental health studies, where approach motivation is of interest. Studies investigating and developing the application of FAA training in the treatment of affective disorders such as major depressive disorder and anxiety disorder are also introduced, highlighting some of the future possibilities.
The purpose of the this article is to provide an overview of the current state of research concerning the development, determining factors and effects of mathematics anxiety, particularly with regard to young elementary school age level populations. Assessment instruments, potential risk-factors, consequences of mathematics anxiety, as well as approaches to intervention are summarized. Owing to the small number of studies focusing on mathematics anxiety in young children, findings from adult studies are briefly recapitulated. The available data emphasizes the need for systematic research that focuses on the one hand on the onset of mathematics anxiety at a young age, and on the other follows the development of longer periods of time. Furthermore, multi-method research designs may be the means to gain deeper insight into the dynamics of causes and effects when the interaction of mathematics anxiety and mathematical abilities are under scrutiny. Only by implementing longitudinal studies that involve different types of data and the formulation of complex models of the dynamics of mathematics anxiety over time, can its determining factors and its effects be generated.
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