# Feasibility of Magneto-Encephulography Scan under Color-Tailored Illumination
## 1 Introduction  
Color plays a vital part in day today human communication activities. For instance, color is used as a marketing tool, teaching method, passing messages and many other ways. Different tone and shards of color can influence human emotions and activities [1,2]: stopping vehicles at a red traffic light, wearing a white gown at wedding, and wearing black for a funeral. The influence of color on human is very individual and is dependent on cultural background [3]. Color is linked to a psychological meaning in different ways, e.g., red symbolizes danger, but in color psychology, it is yellow and black. There is no single theory which defines psychological meaning of colors. When it comes to specific color judgments, person, age, sex, culture, and any other factors may be involved [3]. This study is motivated by creating color control software and hardware compatible with a magneto-encephalography (MEG) brain scanner and can be used to study judgements affected by illumination color. Such an instrumentation solution is not trivial due to a low electromagnetic (EM) noise requirement for highly sensitive MEG measurements. Recently, metasurfaces, which can be controlled by brainwaves in real time and can transmit information wirelessly between human brains, were reported [4,5]. It is imperative to establisha low-noise and high quality readout of minute brain currents and to determine effects which can alter them, e.g., a color ambience effect, for such brain-computer interfaces.  
Color plays a significant role in consumer decision making and judgment. As soon as it has been seen by eyes, color creates, first, excitement about the object. The lighting source is a very important factor in producing an initial impression on consumer products. The natural color of the product is deviated by the lighting source [6]. As a result of lighting source, products may give different color quality, such as rich or dull visual effects on a consumer. However, color judgement is very individual and subjective [7]. It is very difficult to compare color quality with different lighting sources. Therefore, the International Commission on Illumination (Commission International de eclairage--CIE) has introduced a new color rendering index (CRI) for quantification of lighting sources, e.g., a temperature of source is widely used in lighting LED appliances defined as cold and warm white. The CRI index can be used to reveal the color of an object and to compare it with natural light. Halogen and incandescent light sources have the highest CRI. However, recent research verified that light emitting diode (LED)-based solid state lights were preferred than halogen and incandescent lights [8]. Due to technological development in the solid state lighting, there are two more color rendition properties introduced, which are color fidelity index (CFI) and color saturation index (CSI). The CFI defines an ability, which makes color more natural, and CSI is the ability to make color distinguishable [9]. In conventional lighting lamps, CFI is optional, and CSI properties are not available. In LED lighting, white light can be generated by the combination of red (R), green (G), blue (B), and amber (A) LEDs. By changing the ratio of RGB-amber LEDs, it can generate different types of white light. As result of this, it is easy to change CSI and CFI [6].  
The aim of the presented work is to design software for the control of chromaticity of illumination by a four basic color RGB-A lamp (Ledigma Ltd., Vilnius, Lithuania) in MEG experiments. The MEG brain scanner maps brain activity by capturing magnetic fields produced by minute electrical currents in the brain [10]. This MEG scanner is located inside an EM-shielded room to reduce interference from external EM sources, and it was tested for feasibility to make MEG scans under RGB-A lamp illumination. Lamp control was changed from wireless to USB connection to meet requirements of a low noise environment required for MEG.