Cervical transcutaneous vagal nerve stimulation (ctVNS) improves human cognitive performance under sleep deprivation stress.

Fatigue is a pervasive public health and safety issue. Common fatigue countermeasures include caffeine or other chemical stimulants. These can be effective in limited circumstances but other non-pharmacological fatigue countermeasures such as non-invasive electrical neuromodulation have shown promise. It is reasonable to suspect that other types of non-invasive neuromodulation may be similarly effective or perhaps even superior. The objective of this research was to evaluate the efficacy of cervical transcutaneous vagal nerve stimulation (ctVNS) to mitigate the negative effects of fatigue on cognition and mood. Two groups (active or sham stimulation) of twenty participants in each group completed 34 h of sustained wakefulness. The ctVNS group performed significantly better on arousal, multi-tasking, and reported significantly lower fatigue ratings compared to sham for the duration of the study. CtVNS could be a powerful fatigue countermeasure tool that is easy to administer, long-lasting, and has fewer side-effects compared to common pharmacological interventions.

The Effects of Anodal Transcranial Direct Current Stimulation on Sleep Time and Efficiency.

A single session of anodal transcranial direct current stimulation (tDCS) has been shown to increase arousal in healthy participants for up to 24 h post-stimulation. However, little is known about the effects of tDCS on subsequent sleep in this population. Based on previous clinical studies, we hypothesized that anodal stimulation to the left dorsolateral prefrontal cortex (lDLPFC) would produce higher arousal with decreased sleep time and stimulation to the primary motor cortex (M1) would have the converse effect. Thirty-six active duty military were randomized into one of three groups (n = 12/group); active anodal tDCS over the lDLPFC, active anodal tDCS over left M1, or sham tDCS. Participants answered questionnaires 3 times a day and wore a wrist activity monitor (WAM) to measure sleep time and efficiency for 3 weeks. On weeks 2 and 3 (order counterbalance), participants received stimulation at 1800 h before 26 h of sustained wakefulness testing (sleep deprived) and at 1800 h without sleep deprivation (non-sleep deprived). There were no significant effects for the non-sleep deprived portion of testing. For the sleep deprived portion of testing, there were main effects of group and night on sleep time. The DLPFC group slept less than the other groups on the second and third night following stimulation. There is no negative effect on mood or sleep quality from a single dose of tDCS when participants have normal sleep patterns (i.e., non-sleep deprived portion of testing). The results suggest that stimulation may result in faster recovery from fatigue caused by acute periods of sleep deprivation, as their recovery sleep periods were less.

Assessing the binocular advantage in aided vision.

Advances in microsensors, microprocessors, and microdisplays are creating new opportunities for improving vision in degraded environments through the use of head-mounted displays. Initially, the cutting-edge technology used in these new displays will be expensive. Inevitably, the cost of providing the additional sensor and processing required to support binocularity brings the value of binocularity into question. Several assessments comparing binocular, binocular, and monocular head-mounted displays for aided vision have concluded that the additional performance, if any, provided by binocular head-mounted displays does not justify the cost. The selection of a biocular [corrected] display for use in the F-35 is a current example of this recurring decision process. It is possible that the human binocularity advantage does not carry over to the aided vision application, but more likely the experimental approaches used in the past have been too coarse to measure its subtle but important benefits. Evaluating the value of binocularity in aided vision applications requires an understanding of the characteristics of both human vision and head-mounted displays. With this understanding, the value of binocularity in aided vision can be estimated and experimental evidence can be collected to confirm or reject the presumed binocular advantage, enabling improved decisions in aided vision system design. This paper describes four computational approaches-geometry of stereopsis, modulation transfer function area for stereopsis, probability summation, and binocular summation-that may be useful in quantifying the advantage of binocularity in aided vision.

Detection of vigilance performance using eye blinks.

Research has shown that sustained attention or vigilance declines over time on task. Sustained attention is necessary in many environments such as air traffic controllers, cyber operators, and imagery analysts. A lapse of attention in any one of these environments can have harmful consequences. The purpose of this study was to determine if eye blink metrics from an eye-tracker are related to changes in vigilance performance and cerebral blood flow velocities. Nineteen participants performed a vigilance task while wearing an eye-tracker on four separate days. Blink frequency and duration changed significantly over time during the task. Both blink frequency and duration increased as performance declined and right cerebral blood flow velocity declined. These results suggest that eye blink information may be an indicator of arousal levels. Using an eye-tracker to detect changes in eye blinks in an operational environment would allow preventative measures to be implemented, perhaps by providing perceptual warning signals or augmenting human cognition through non-invasive brain stimulation techniques.

Systems factorial technology with R.

Systems factorial technology (SFT) comprises a set of powerful nonparametric models and measures, together with a theory-driven experiment methodology termed the double factorial paradigm (DFP), for assessing the cognitive information-processing mechanisms supporting the processing of multiple sources of information in a given task (Townsend and Nozawa, Journal of Mathematical Psychology 39:321-360, 1995). We provide an overview of the model-based measures of SFT, together with a tutorial on designing a DFP experiment to take advantage of all SFT measures in a single experiment. Illustrative examples are given to highlight the breadth of applicability of these techniques across psychology. We further introduce and demonstrate a new package for performing SFT analyses using R for statistical computing.