In the earliest study, Beeli et al. (2008) examined the effects of tDCS over the DLPFC on driving metrics such as speed, headway distance, and lane positioning. Currently, outcomes measured in driving simulators lack gold standard metrics to define meaningful performance changes that translate to real-world driving. Recently, however, research has proposed two composite factors of driving behavior—vehicle control variability and speed—that include metrics like lane positioning, which also have strong face validity as indicators of safe driving (McManus et al., 2024).

Across three sessions, Beeli et al. (2008) tasked 21 participants (20–30 years, all men) to complete a 3-kilometer drive through a city scene with simulated traffic, lights and signs, and pedestrians. The first session was a baseline drive without tDCS. During the other two sessions, the anode and cathode were positioned unilaterally over the DLPFC in a counterbalanced order. Half of the participants randomly received stimulation over the left DLPFC at scalp coordinate F3, while the other half received stimulation over the right DLPFC at scalp coordinate F4. Stimulation was delivered at 1 mA for 15 min offline. Compared to the baseline, participants exhibited fewer speeding violations and maintained greater headway distance when receiving anodal tDCS over the DLPFC compared to cathodal. There were no observable effects of the hemisphere.

Several methodological considerations in this early study must be addressed. Without a sham condition or adequate blinding, it is difficult to disentangle stimulation effects from experimenter influence and participant bias (Boutron et al., 2007). The most common sham procedure ramps up and down the current at the beginning and end of the protocol to mimic initial cutaneous sensations without lasting effects (Woods et al., 2016). Additionally, a between-groups design introduces random variability (Borghini et al., 2014; Lakens, 2013) and fails to account for individual differences in tDCS effects, which can be influenced by anatomical factors (e.g., skull thickness) and behavioral baselines (Bikson et al., 2012; Datta et al., 2012; Horvath et al., 2014; Kim et al., 2014; Li et al., 2015; Opitz et al., 2015; Splittgerber et al., 2020).

Sakai et al. (2014) conducted a sham-controlled, within-groups, single-masked study to address these limitations. Thirteen participants (~35 years, 11 men) were instructed to maintain a specific headway distance from a lead vehicle over a 22-kilometer route. Participants completed this driving task over three testing sessions. In a counterbalanced order, participants received anodal tDCS over the right DLPFC at F4, cathodal tDCS at F4, and sham. Stimulation was set at 1.5 mA for up to 20 min online. There was less variability in headway distance and lane positioning when anodal tDCS was delivered over the DLPFC compared to cathodal and sham. This finding is consistent with research in other domains showing anodal-excitatory effects, but not cathodal-inhibitory effects, for cognitive tasks involving the DLPFC (Jacobson et al., 2012). One explanation could be that the anode likely enhances neuronal firing in active areas, while the cathode may not sufficiently inhibit firing in highly active states.

The neuromodulation field has significantly advanced in the decade since Sakai et al. (2014) published their work. Facchin et al. (2023) explored the effects of different tDCS electrode montages on driving behavior in the latest driving study. Twenty-seven participants (21–30 years, 14 women) completed three 25-min driving sessions while receiving sham tDCS, conventional tDCS, or 4 × 1 HD-tDCS, where four electrodes surround a center electrode of the opposite polarity (Datta et al., 2009; Kuo et al., 2013). Anodal tDCS was applied over the right frontal eye field (FEF) at 1.5 mA over FC4, an area implicated in visuomotor control (Cameron et al., 2015; Grosbras et al., 2005; Nobre et al., 2000). Given that electrode size and material affect spatial resolution, coupled with the structural-functional connectivity of the human brain (Park and Friston, 2013; Sporns, 2013), the DLPFC may have been incidentally targeted during stimulation.

As many can attest, drivers rarely focus on just car following. To this point, Facchin et al. (2023) manipulated driving task difficulty using two variations of stimulus–response detection tasks commonly used in human factors research (Innes et al., 2021). During the drive, the lead car frequently flashed its brake lights, and road signs appeared at random intervals. Participants were asked to brake in response to the lead vehicle and respond to the road signs. Outcomes measured included lane-keeping position, braking reaction time and accuracy, and road sign reaction time and accuracy. Lane maintenance was unaffected by stimulation. Facchin et al. (2023) found that participants responded more quickly, though not more accurately, to the brake lights and road signs when receiving anodal tDCS over the FEF than sham. More prominent effects for these reaction times emerged when stimulation was delivered with HD-tDCS rather than conventional, suggesting heightened response speed to relevant stimuli. Together, these three driving studies indicate that anodal tDCS over the DLPFC may influence distance perception or judgment, observable as changes in distance or faster response times.

Choe et al. (2016) examined the impact of tDCS on skill acquisition and performance across various simulated flight tasks, using scenarios with computer-based simulations that align with Federal Aviation Administration (FAA) Industry Training Standards (FITS) to enhance real-world training relevance (Williams, 2012). Though the performance was tested on flight tasks of varying difficulty, results were only published for the easiest task. Across four sessions, 32 participants (ages 21–64, 31 men) attempted to replicate a landing demonstrated in an instructional video under daylight conditions with complete visibility. Measured outcomes included landing gravitational force (g-force), deviations from flight path, vertical speed, and vertical speed variance. While g-force assessment captures landing skill at the most challenging and critical phase of flight, the entire approach is considered with path and vertical speed deviations. Learning rates were measured across sessions, within sessions, and between trials or scenarios (5 trials per session).

Choe et al. (2016) treated stimulation application and location as between-group factors. Half the participants received anodal tDCS (2 mA, 1 h online), while the other half received sham. Stimulation was delivered over the right DLPFC (anodes F6/FC6) or the left motor cortex (anodes CP1/CP3). No significant effects emerged for the motor cortex group. In the DLPFC group, there was less variability in landing g-force observed during the third and fourth sessions, suggesting that tDCS may be more beneficial for trained tasks over time. Choe et al. (2016) also collected EEG and functional near-infrared spectroscopy (fNIRS) data that suggests that participants who received active tDCS exhibited altered neuronal activity in the DLPFC and motor cortex compared to those who received sham. Interestingly, behavioral outcomes are commonly observed when delivering anodal excitation over the motor cortex, but not cognitive regions like the DLPFC (Jacobson et al., 2012; Tremblay et al., 2014). The broad influence of the DLPFC on cognitive functions, especially when considering varying stimulation parameters, makes predicting specific behavioral outcomes difficult.

This initial flight study was conducted under relatively simple conditions to facilitate task performance. However, more realistic scenarios may include bad weather, a narrow runway, or auditory distractions. Accordingly, Mark et al. (2023) adjusted the workload during landing. Twenty-four glider pilots (ages 18–22, mostly men) were recruited and categorized as novices or experts based on experience. Participants completed three runs in a single session, with a pre- and post-training run flanking a tDCS run. In the training run, participants received either sham or anodal tDCS over the right DLPFC at AF8 (1.5 mA, 30 min online). Feedback about performance was presented after each trial (72 trials in total). Measures included landing g-force, landing descent speed, and flair.

Mark et al. (2023) observed significant stimulation effects only for landing g-force. Specifically, participants who received active tDCS compared to those who received sham landed more smoothly when comparing pre-training to training and post-training. This skill-learning effect was more pronounced in novices than experts, similar to findings in electronic sports (Toth et al., 2021), suggesting novices may benefit more from tDCS. The study took place in a functional magnetic resonance imaging (fMRI) machine, revealing that active tDCS than sham increases DLPFC activity and enhances connectivity between the DLPFC and cerebellum, a region involved in error-feedback learning (Doya, 1999).

Targeting other brain regions with tDCS, such as the posterior parietal cortex (PPC), which guides the visuospatial orienting of selective attention (Behrmann et al., 2004; Culham and Valyear, 2006; Kravitz et al., 2011; Lo et al., 2019; Rojas et al., 2018), could clarify the brain-behavior relationship in flight skill acquisition. In the most recent study, Feltman and Kelley (2024) recruited 22 pilots (~37 years, all men) to complete a 90-min round-trip flight while receiving anodal tDCS over the PPC at P4 (2 mA, 20 min total) and sham. Stimulation timing was treated as a between-groups condition between groups. Participants in the offline stimulation group received anodal tDCS (2 mA, 20 min) and sham before flight. Those in the online group received sham and anodal tDCS (2 mA) delivered for 10 min at 30 and 60 min into the flight.

Toward the end of each flight leg, an emergency required participants to disengage autopilot and land safely. Altitude, airspeed, and heading were measured throughout the flight, while glideslope (vertical) and localizer (lateral) deviations were recorded during the approach. Significant effects emerged only for glideslope deviations in the online group, with online anodal tDCS associated with better alignment to the glide path than sham. These findings align with the role of the PPC in visuospatial attention. Together, these flight studies suggest that tDCS over the DLPFC and PPC may enhance landing smoothness, each investigating different aspects of stimulation and simulation parameters.