TDCS guided using fMRI significantly accelerates learning to identify concealed objects

Abstract

The accurate identification of obscured and concealed objects in complex environments was an important skill required for survival during human evolution, and is required today for many forms of expertise. Here we used transcranial direct current stimulation (tDCS) guided using neuroimaging to increase learning rate in a novel, minimally guided discovery-learning paradigm. Ninety-six subjects identified threat-related objects concealed in naturalistic virtual surroundings used in real-world training. A variety of brain networks were found using fMRI data collected at different stages of learning, with two of these networks focused in right inferior frontal and right parietal cortex. Anodal 2.0 mA tDCS performed for 30 minutes over these regions in a series of single-blind, randomized studies resulted in significant improvements in learning and performance compared with 0.1 mA tDCS. This difference in performance increased to a factor of two after a one-hour delay. A dose-response effect of current strength on learning was also found. Taken together, these brain imaging and stimulation studies suggest that right frontal and parietal cortex are involved in learning to identify concealed objects in naturalistic surroundings. Furthermore, they suggest that the application of anodal tDCS over these regions can greatly increase learning, resulting in one of the largest effects on learning yet reported. The methods developed here may be useful to decrease the time required to attain expertise in a variety of settings.

Impact of tDCS on performance and learning of target detection: Interaction with stimulus characteristics and experimental design

“…Some images in the immediate test were repeated from training, while others were novel and had not been seen previously. Examples of stimuli can be found in Clark et al (2012).…”

“…We have previously reported that tDCS can increase learning in a complex visual search task involving the detection of target objects hidden in a virtual environment (Clark et al, 2012). In this study, participants were trained to detect target objects hidden in complex images of simulated environments and classify those images as target object present or target object absent.…”

“…hidden predators and food sources accordingly; therefore, hidden object detection has likely been an important factor in the evolution of human brain networks related to visual attention and perception (Clark et al, 2012). Furthermore, hidden threats to our safety are still present in the much more complex society we live in today, though they may be less prevalent than those we faced in our evolutionary past.…”

“…In the present investigation, we performed a re-analysis of data from Clark et al (2012), examining the effects of stimulus novelty and target presence on test performance accuracy (referred to here as Experiment 1). In addition, we performed a replication experiment, using a new participant sample, with a double-blind, rather than single-blind protocol (Experiment 2) and optimized task design that balanced the numbers of novel and repeated test stimuli.…”

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AbstractWe have previously found that transcranial direct current stimulation (tDCS) over right inferior frontal cortex (RIFC) enhances performance during learning of a difficult visual target detection task (Clark et al, 2012). In order to examine the cognitive mechanisms of tDCS that lead to enhanced performance, here we analyzed its differential effects on responses to stimuli that varied by repetition and target presence, differences related to expectancy by comparing performance in single-and double-blind task designs, and individual differences in skin stimulation and mood.

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