Object detection learning : effects of transcranial direct current stimulation, magnetic resonance imaging, and image novelty

This investigation studied the effects of transcranial direct current stimulation (tDCS) on learning of a difficult visual search task. We also examined the effects of several variables relating to context in which the task was performed, and the relationship of these variables to the effects of tDCS. For this discovery-learning task, participants were trained for one hour to detect objects hidden in a virtual environment. Anodal tDCS was applied over the right inferior frontal cortex at 0.1 mA or 2.0 mA for 30 minutes during training. Participants were tested immediately before and after training and again one hour later. Some test stimuli were repeated during training and testing, while others were novel but contained hidden objects similar to those presented during training. In Experiment 1 we present a reanalysis of our previously published data (Clark et al., 2010) and replication data from an additional group of subjects using an optimized task design. Higher tDCS current was associated with increased test performance for both novel and repeated test stimuli. In addition, participants responses were more accurate for repeated than novel test stimuli. An interaction was found between tDCS current and image type, indicating that tDCS performance enhancement was greater for repeated than novel stimuli. These effects were replicated in our second experiment using balanced numbers of novel and repeated test stimuli and a double-blind rather than single-blind design. These results indicate that anodal tDCS over right inferior frontal cortex during training most strongly enhances performance for recognition of objects hidden in images repeated between training and testing, and also enhances the generalization of learned object detection to novel images. In Experiment 2, we examine the effect of high magnetic field on tDCS enhancement of learning by comparing participants tested in active fMRI, at a magnetic field of 3 Tesla, to those tested in a mock MRI scanner, with no active magnetic field. In Experiment 3, we examined the effects of the MRI environment on learning and performance both when participants were trained and received tDCS at a workstation PC and when they were trained and received tDCS in the mock MRI scanner. Results from Experiments 2 and 3 indicate that participants may have been unable or unwilling to perform the task in an MRI environment, and that it is unlikely that either the magnetic field or changed environments from training to test, per se, led to differences in the effects of tDCS present between participants tested inside the MRI scanner environment and those tested at an office workstation PC. The effects of tDCS in these experiments indicate that learning can be enhanced in participants learning a difficult object detection task when participants are willing and able to perform the task. Enhanced learning in the general population could aid millions of people suffering from disability and could even lead to accelerated advancement of society in general

Contribution of Far Field Effects of Cortical tDCS in the Cerebellum to Learning in an Object Detection Paradigm

Transcranial direct current stimulation (tDCS) has been shown to enhance many cognitive and motor functions, and has been used in many areas, including rehabilitation of speech after stroke, cognitive enhancement, and treatment of mental illness. Our lab has demonstrated that, paired with training, anodal tDCS over electrode site F10 as well as cathodal tDCS over site T5 both increased the ability to detect hidden objects in a complex visual environment in a discovery learning paradigm. Stimulation of F10 has further been shown to enhance perceptual sensitivity selectively, without a change to response bias, and this effect was further enhanced when images presented during training were repeated in a post-training, post-stimulation test (Clark et al., 2012; Coffman et al., 2012; Falcone et al., 2012). Furthermore, this increased ability to detect hidden objects persisted for at least 24 hours Falcone et al., 2012). It has also been shown to increase measures of attention, using the Attention Network Task (ANT; Fan, 2002). Specifically, alerting network scores were increased in participants receiving active anode F10 stimulation compared to sham. Since both F10 anode as well as T5 cathode stimulation both resulted in increased learning the object detection task, potential additive effects were inferred, and an F10 anode/T5 cathode electrode montage was investigated. Surprisingly, this montage had an effect of about half of the other two montages (F10 anode/shoulder, T5 cathode/shoulder). Finite element current modeling studies were conducted to investigate more precisely where in the brain the electricity is traveling during these different stimulation protocols. Results suggested that both cephalic/extra-cephalic electrode placements exhibited far-field effects in subcortical areas, bilateral temporal poles, as well as in the cerebellum, albeit with opposite polarities. During F10 anode/shoulder cathode stimulation, a negative electrical field effect was seen in the cerebellum. During T5 cathode/shoulder anode stimulation, the opposite was true: there was a positive field effect in the cerebellum. However, the montage with a bi-cephalic placement showed no such effect in the cerebellum. Based on these modeling data, the difficulty of reaching subcortical areas with tDCS, and the evidence that the cerebellum is not only involved in motor behavior, but cognition as well, the cerebellum was chosen for direct stimulation with tDCS and was hypothesized to be contributing to the learning and attention effects reported in previous studies. Thirty-six participants received either anodal, cathodal, or sham stimulation of the medial posterior cerebellum during training to detect hidden objects in a complex visual environment. Measures of learning, signal detection, and interactions with stimulus type were investigated. Regression models were also built to investigate the contribution of each electrode placement in the two different montages. Measures of attention assessed with the ANT were also investigated. To our surprise, neither anodal nor cathodal stimulation of the cerebellum led to an increase in learning compared to sham stimulation. Furthermore, no effects were observed between groups on signal detection measures, nor was there an effect of group on stimulus type, all of which had previously been reported with F10 stimulation. Likewise, neither anode nor cathode stimulation led to an improvement on measures of attention compared to sham. The conclusion is that the cerebellum does not appear to be involved in the network contributing to learning and performing the object detection task. Although there were no direct effects of anodal or cathodal tDCS of the cerebellum on learning or attention, this study is an important step in elucidating the network involved in the robust finding of increased ability to detect hidden objects after administration of tDCS paired with training, as it rules out one potential contributor

Controlling the Precision-Recall Tradeoff in Differential Dependency Network Analysis

Graphical models have gained a lot of attention recently as a tool for learning and representing dependencies among variables in multivariate data. Often, domain scientists are looking specifically for differences among the dependency networks of different conditions or populations (e.g. differences between regulatory networks of different species, or differences between dependency networks of diseased versus healthy populations). The standard method for finding these differences is to learn the dependency networks for each condition independently and compare them. We show that this approach is prone to high false discovery rates (low precision) that can render the analysis useless. We then show that by imposing a bias towards learning similar dependency networks for each condition the false discovery rates can be reduced to acceptable levels, at the cost of finding a reduced number of differences. Algorithms developed in the transfer learning literature can be used to vary the strength of the imposed similarity bias and provide a natural mechanism to smoothly adjust this differential precision-recall tradeoff to cater to the requirements of the analysis conducted. We present real case studies (oncological and neurological) where domain experts use the proposed technique to extract useful differential networks that shed light on the biological processes involved in cancer and brain function

Applications of transcranial direct current stimulation for understanding brain function

In recent years there has been an exponential rise in the number of studies employing transcranial direct current stimulation (tDCS) as a means of gaining a systems-level understanding of the cortical substrates underlying behaviour. These advances have allowed inferences to be made regarding the neural operations that shape perception, cognition, and action. Here we summarise how tDCS works, and show how research using this technique is expanding our understanding of the neural basis of cognitive and motor training. We also explain how oscillatory tDCS can elucidate the role of fluctuations in neural activity, in both frequency and phase, in perception, learning, and memory. Finally, we highlight some key methodological issues for tDCS and suggest how these can be addressed

Cathodal electrical stimulation of frontoparietal cortex disrupts statistical learning of visual configural information

Attentional performance is facilitated by exploiting regularities and redundancies in the environment by way of incidental statistical learning. For example, during visual search, response times to a target are reduced by repeating distractor configurations-a phenomenon known as contextual cueing (Chun & Jiang, 1998). A range of neuroscientific methods have provided evidence that incidental statistical learning relies on subcortical neural structures associated with long-term memory, such as the hippocampus. Functional neuroimaging studies have also implicated the prefrontal cortex (PFC) and posterior parietal cortex (PPC) in contextual cueing. However, the extent to which these cortical regions are causally involved in statistical learning remains unclear. Here, we delivered anodal, cathodal, or sham transcranial direct current stimulation (tDCS) to the left PFC and left PPC online while participants performed a contextual cueing task. Cathodal stimulation of both PFC and PPC disrupted the early cuing effect, relative to sham and anodal stimulation. These findings causally implicate frontoparietal regions in incidental statistical learning that acts on visual configural information. We speculate that contextual cueing may rely on the availability of cognitive control resources in frontal and parietal regions

Noninvasive brain stimulation techniques can modulate cognitive processing

Recent methods that allow a noninvasive modulation of brain activity are able to modulate human cognitive behavior. Among these methods are transcranial electric stimulation and transcranial magnetic stimulation that both come in multiple variants. A property of both types of brain stimulation is that they modulate brain activity and in turn modulate cognitive behavior. Here, we describe the methods with their assumed neural mechanisms for readers from the economic and social sciences and little prior knowledge of these techniques. Our emphasis is on available protocols and experimental parameters to choose from when designing a study. We also review a selection of recent studies that have successfully applied them in the respective field. We provide short pointers to limitations that need to be considered and refer to the relevant papers where appropriate

Non-invasive brain stimulation can induce paradoxical facilitation. Are these neuroenhancements transferable and meaningful to security services?

For ages, we have been looking for ways to enhance our physical and cognitive capacities in order to augment our security. One potential way to enhance our capacities may be to externally stimulate the brain. Methods of non-invasive brain stimulation (NIBS), such as repetitive transcranial magnetic stimulation (rTMS) and transcranial electrical stimulation (tES), have been recently developed to modulate brain activity. Both techniques are relatively safe and can transiently modify motor and cognitive functions outlasting the stimulation period. The purpose of this paper is to review data suggesting that NIBS can enhance motor and cognitive performance in healthy volunteers. We frame these findings in the context of whether they may serve security purposes. Specifically, we review studies reporting that NIBS induces paradoxical facilitation in motor (precision, speed, strength, acceleration endurance, and execution of daily motor task) and cognitive functions (attention, impulsive behavior, risk-taking, working memory, planning, and deceptive capacities). Although transferability and meaningfulness of these NIBS-induced paradoxical facilitations into real-life situations are not clear yet, NIBS may contribute at improving training of motor and cognitive functions relevant for military, civil, and forensic security services. This is an enthusiastic perspective that also calls for fair and open debates on the ethics of using NIBS in healthy individuals to enhance normal functions

The effect of tDCS on task relevant and irrelevant perceptual learning of complex objects

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Modulating Applied Task Performance via Transcranial Electrical Stimulation

Basic and applied research are increasingly adopting transcranial electrical stimulation (tES) for modulating perceptual, cognitive, affective, and motor processes. Industry and defense applications of tES hold potential for accelerating training and knowledge acquisition and sustaining work-related performance in the face of fatigue, workload, and stress. This mini-review article describes the promises and perils of tES, and reviews research testing its influence on two broad applied areas: sustaining and dividing attention, and operating in virtual environments. Also included is a discussion of challenges related to viable mechanistic explanations for tES effectiveness, attempts at replication and consideration of null results, and the potential importance of individual differences in predicting tES influences on human performance. Finally, future research directions are proposed to address these challenges and help develop a fuller understanding of tES viability for enhancing real-world performance

Transcranial Direct Current Stimulation (tDCS) Improves Performance on Spelling and Word Detection Tasks

Deficits in written language involving spelling can have negative effects on a person’s education and occupation. Conventional spelling therapy is a time consuming and cost-prohibitive option, if even available, highlighting the need for improved methods for remediation. One possible way to address this need may be through the use of transcranial direct current stimulation (tDCS). This study sought to examine the effects of tDCS on performance during spelling, word detection, and facial recognition tasks. Active or sham tDCS was randomly assigned to typically functioning adults. The anode electrode was placed over Broca’s area (F7 in the 10/20 EEG system) and the cathode was positioned over the upper right arm. Outcome was assessed before, during, immediately after tDCS, and again 3-5 days after tDCS. Data was analyzed using analysis of variance (ANOVA) to examine if group differences existed. Significant differences were found between active and sham tDCS on both the spelling and word-search tests. There was no significant difference between active and sham tDCS on either of the facial recognition tasks