Research On Visual Stimulus Synchronization Technology

The stimulus-response experimental mode is a commonly used experimental paradigm,which requires the use of external devices to generate stimuli and simultaneously measure the responses evoked by the brain or limbs,so as to explore the working mechanism of the corresponding brain regions or the pathogenesis of brain diseases.This paradigm is commonly used in brain science,behavioral science,neuroscience and other fields.Researchers in these fields often use software such as Psych Toolbox,Psychopy,E-prime,and Open Sesame to present visual stimuli,and judge the working mechanism and pathogenesis of the body by recording the time of presentation and response.With the improvement of precision and complexity in research,multiple acquisition devices are used at the same time,which requires high timing synchronization precision between multiple devices.Generally,the synchronization error is considered to be less than 1 millisecond.In many stimulus-response experimental paradigms,the timing precision is very high.Accurate measurements can only be achieved under high-precision experimental conditions,such as the accurate detection of brain potentials in brain science experiments,the accurate measurement of response latency in neuroscience,and the accurate judgment of response awareness in behavioral science.At the same time,many brain science experiments cannot be reproduced due to the lack of high-precision standards,which also brings difficulties for many researchers.Therefore,in highprecision stimulus-response experiments,it is necessary to ensure the precision of timing synchronization between multiple devices.However,with the rapid development of computer hardware,serial ports or parallel ports are gradually declining in computers,but they are still widely used in various response devices due to their low price and stable performance.Generally,USB to serial port and USB to parallel port can be used to realize the timing synchronization function between the computer and various external devices.Therefore,in order to achieve high-precision timing synchronization,it is necessary to explore the factors affecting the timing synchronization precision of USB to serial and USB to parallel ports.In response to the above problems,this paper uses Psych Toolbox,Psychopy,Eprime,Open Sesame software to present visual stimuli,and then collects port data through the Saleae Logic pro 8 logic analyzer,and explores the impact of the synchronization delay and timing synchronization precision,as follows:（1）Under the premise of generating visual stimuli,the serial port synchronization signal does not lag behind the stimulus signal,but leads the stimulus signal.This advance is closely related to the refresh rate of the display and the location of stimulus presentation.The higher the refresh rate,the shorter the lookahead,and the closer the stimulus position is to the upper left corner,the shorter the lookahead.At the same time,the synchronization delay of different USB to serial chips shows a very similar distribution（2）Different serial port chips present approximate timing precision.Among the three serial port functions,IOPort has good timing precision,and the timing precision of the serial port is closely related to the operating system.The serial port timing precision of Linux/Ubuntu is obviously better than that of Windows.（3）Under Psych Toolbox and Psycho Py,the synchronization delay between USB to serial port and USB to parallel port is very similar,which is smaller than that in E-prime and Open Sesame;the timing precision of Psych Toolbox is better than that of Psycho Py,E-prime and Open Sesame;the timing precision of USB parallel port is very close to that of USB serial port;the timing precision of Linux is better than Windows.The results of this paper clarify the factors that affect the timing synchronization precision of USB to serial port and USB to parallel port,which can help researchers to better select appropriate ports and software for accurate measurement,and also provide some basic technical reference for researchers to build a high-precision measurement environment.