Richard A. McKinley

Using Noninvasive Brain Stimulation to Accelerate Learning and Enhance Human Performance

Objective: The authors evaluate the effectiveness of noninvasive brain stimulation, in particular, transcranial direct current stimulation (tDCS), for accelerating learning and enhancing human performance on complex tasks. Background: Developing expertise in complex tasks typically requires extended training and practice. Neuroergonomics research has suggested new methods that can accelerate learning and boost human performance. TDCS is one such method. It involves the application of a weak DC current to the scalp and has the potential to modulate brain networks underlying the performance of a perceptual, cognitive, or motor task. Method: Examples of tDCS studies of declarative and procedural learning are discussed. This mini-review focuses on studies employing complex simulations representative of surveillance and security operations, intelligence analysis, and procedural learning in complex monitoring. Results: The evidence supports the view that tDCS can accelerate learning and enhance performance in a range of complex cognitive tasks. Initial findings also suggest that such benefits can be retained over time, but additional research is needed on training schedules and transfer of training. Conclusion: Noninvasive brain stimulation can accelerate skill acquisition in complex tasks and may provide an alternative or addition to other training methods.

Augmenting Visual Search Performance with Transcranial Direct Current Stimulation (tDCS)

Military personnel endure rigorous and demanding man-hours designated to monitoring and locating targets in tasks such as cyber defense and Unmanned Aerial Vehicle (UAV) operators. These tasks are monotonous and repetitive, which can result in vigilance decrement. The objective of the study was to implement a form of noninvasive brain stimulation known as transcranial DC stimulation (tDCS) over the left frontal eye field (LFEF) region of the scalp to improve cognitive performance. The participants received anodal and cathodal stimulation of 2 mA for 30 min as well as placebo stimulation on 3 separate days while performing the task. The findings suggest that anodal and cathodal stimulation significantly improves detection accuracy. Also, a correlation was detected between percent of eye closure (PERCLOS) and blinking frequency in relation to stimulation condition. Our data suggest that tDCS over the LFEF would be a beneficial countermeasure to mitigate the vigilance decrement and improve visual search performance.

Eye Metrics: An Alternative Vigilance Detector for Military Cyber Operators

Military operators in various environments such as cyber, remotely piloted aircraft, and image analysis are required to use sustained attention or vigilance for long periods. During this time they encounter lapses in attention attributable to the monotonous nature of their tasks. Mistakes during these tasks can have serious consequences. The purpose of this study was to investigate the use of an eye-tracker to detect changes in vigilance performance during a simulated cyber operator task. Twenty participants performed 4 sessions of a 40-min vigilance task while wearing an eye-tracker. Blink frequency, blink duration, PERCLOS (percentage of eye closure), pupil diameter, pupil eccentricity, pupil velocity, and signal detection all had a significant change over time (p < .05) during the task. The significant change of oculometric measurements indicates oculometrics could be used to detect changes in vigilance for military operators. Future research is needed to assess real-time effects of these oculometrics on performance, especially in a real-world setting.

Transcranial Direct Current Stimulation for Fatigue and Attentional Disorders

Abstract Fatigue and attention disorders are common in modern society and can cause significant difficulties in the lives of those afflicted. Increases in cognitive fatigue are typically characterized by a decline in attention, difficulties concentrating, and increased reaction times (Caldwell, 2005). In fact, cognitive impairments caused by just moderate levels of fatigue have been shown to exceed those caused by alcohol intoxication at a blood–alcohol content (BAC) of 0.08 (Dawson and Reid, 1997). While the cause of the fatigue or attentional symptoms vary, there is a growing body of evidence that suggests a benign form of noninvasive brain stimulation known as transcranial direct current stimulation (tDCS) can augment brain activity in a manner that provides therapeutic relief of major symptoms, improves mood, and reduces associated cognitive performance declines.

Single Session Low Frequency Left Dorsolateral Prefrontal Transcranial Magnetic Stimulation Changes Neurometabolite Relationships in Healthy Humans

Background: Dorsolateral prefrontal cortex (DLPFC) low frequency repetitive transcranial magnetic stimulation (LF-rTMS) has shown promise as a treatment and investigative tool in the medical and research communities. Researchers have made significant progress elucidating DLPFC LF-rTMS effects—primarily in individuals with psychiatric disorders. However, more efforts investigating underlying molecular changes and establishing links to functional and behavioral outcomes in healthy humans are needed. Objective: We aimed to quantify neuromolecular changes and relate these to functional changes following a single session of DLPFC LF-rTMS in healthy participants. Methods: Eleven participants received sham-controlled neuronavigated 1 Hz rTMS to the region most activated by a 7-letter Sternberg working memory task (SWMT) within the left DLPFC. We quantified SWMT performance, functional magnetic resonance activation and proton Magnetic resonance spectroscopy (MRS) neurometabolite measure changes before and after stimulation. Results: A single LF-rTMS session was not sufficient to change DLPFC neurometabolite levels and these changes did not correlate with DLPFC activation changes. Real rTMS, however, significantly altered neurometabolite correlations (compared to sham rTMS), both with baseline levels and between the metabolites themselves. Additionally, real rTMS was associated with diminished reaction time (RT) performance improvements and increased activation within the motor, somatosensory and lateral occipital cortices. Conclusion: These results show that a single session of LF-rTMS is sufficient to influence metabolite relationships and causes widespread activation in healthy humans. Investigating correlational relationships may provide insight into mechanisms underlying LF-rTMS.