Link to media article:

Minutes for Group Meetings:

Group Members:

Jess Tompsett z3414542

Tommy Torgersen z3361730

Lehana de Silva z3375992

Damoon Mehrpour z3220205

1. Introduction:

"Take it, it’ll make you shoot better” is a newspaper article published in the Sydney Morning Herald (9/02/12). It reports on the potential use of recent neuroscientific advances in military training programs. The article also discusses the social and ethical implications of employing these new technologies for military gain. The neuroscientific advances discussed include the use of transcranial direct current stimulation (tDCS) for improved threat detection. tDCS involves delivery of a mild electric current to the brain and is now a widely used procedure in neuroscience. Recently it has been found to enhance perceptual sensitivity and accelerate learning (Falcone, Coffman, Clark, & Parasuraman, 2012).

This particular article is of specific interest to our group due to its exploration of recent and future neuroscientific advances. It presents an insight into the possible avenues for research development as well as its current real world applications. The social and ethical implications of such technologies are issues that all members of our group will encounter at some point, not only during our chosen careers but also as members of a society that chooses to implement them.

2. Context:

There are at least two ways in which tDCS can be effective in making soldiers shoot better. Firstly in detecting stimuli in the environment faster and more accurately, especially if said stimuli was threatening. Secondly, it would help in improving the speed and accuracy of the response to the stimuli. There is strong evidence to support that tDCS can enhance soldiers response to targets, by improving perception in the environment, and motor responses to changes in the environment. The following analyzed research contextually supports such effects of the procedure. Each study investigates the cognitive and/or motor enhancing effects of tDCS on task performance.

The tDCS procedure involves delivery of a direct current with low intensity, typically between 0.5-2 mA (Madhavan & Shah, 2012). Two sponge electrodes that are moistened with a NaCL solution in order to minimise discomfort are placed on the subject’s head. The active electrode is placed over the area of the cortex to be stimulated whereas the second electrode usually is placed on a region contralateral to the active electrode. Furthermore, the duration of the current normally varies between 5-20 minutes, which then gives a current density of 0.02-1 mA/cm2. There are two different types of stimulation; anodal (positive) stimulation, which enhances neuronal excitability, and cathodal (negative) stimulation, which has an inhibitory effect on neuronal firing. (Madhavan & Shah, 2012).

The efficiency of the procedure depends on the current density, which controls the strength of the induced electrical field (Madhavan & Shah, 2012). The standardised density and charge values are safe to use without adverse risks. No neural damage or negative change in cognitive functioning has been found in healthy subjects. It is however pointed out that special care should be taken if the patient has any alternation of the skull, such as fracture or trepanation, likewise if the patient has decreased integrity to the skin surface. These issues may result in tissue damage because of the increased current densities (Madhavan & Shah, 2012). However, for a healthy subject, the most adverse side effect may be a slight burning sensation or a mild sensation of pain under the electrodes. Normally the subject may only feel a mild tingling sensation during the treatment. The review lastly points to the importance that the subject has no metallic implants near the electrodes because of the cortical excitability in anodal treatment.

The physiological effects of tDCS are dependent on the polarity of the charge being delivered. Anodal currents have an excitatory effect on neurons by facilitating membrane depolarization, which in turn allows them to fire more readily. Cathodal current stimulation has an inhibitory effect. It achieves this by inducing the hyperpolarisation of cell membranes therefore making it less likely that an action potential will occur. tDCS on its own is not the source of action potentials, it merely alters the membrane potential of neurons surrounding the electrode which in turn either facilitates or inhibits neuronal firing (Loo, Sachdev, & Arul-Anandam, 2009). This is due to the density of the current that is passed through the electrode being smaller than that required to cause an action potential in cortical neurons. As the effects of tDCS last much longer than the duration of the procedure, its affects cannot solely be attributed to immediate changes in membrane potential.

Pharmacological studies have demonstrated that tDCS causes changes in neurotransmitter receptors. One such receptor is the N-methyl-D-aspartate (NMDA)- Glutamatergic receptor. NMDA is an agonist that binds to NMDA-glutamate channels which are non selective to cations. (Brunoni et al., 2012). These ion channels are thought to be crucial to synaptic plasticity. Trials, in which NMDA receptors were blocked, showed an absence of after-effects typically associated with tDCS thus implicating them in the prolonged effects of the procedure. Conversely the modulation of GABAergic receptors results in delayed excitability followed by a period of enhanced and prolonged excitability, when induced by anodal tDCS (Brunoni et al., 2012). Furthermore, the blockage of sodium and calcium gated ion channels results in a decreased response to anodal tDCS but shows no effect on the response to cathodal tDCS. Thus suggesting that the depolarization of neurons via anodal tDCS is achieved via modulation of these ion channels. Amphetamines have also been shown to enhance the tDCS induced plasticity by increasing monoaminergic activity (Brunoni et al., 2012). Some studies have also suggested that the effects of tDCS are dependent on the orientation, type and depth of the neuron in question (Kabakov, Muller, Pascual-Leone, Jensen, & Rotenberg, 2012).

2.1 The areas of the brain affected by tDCS

The medial-temporal area of the visual cortex, also known as V5, mediates motion processing. A study proposed that the improvement in performance caused by cathodal tDCS of the V5 area of the visual cortex was due to a focusing effect on the complex motion perception conditions involved in their task (Antal et al., 2004). The data suggested that the V5 area is critically involved in complex motion perception and identification processes important for visuomotor coordination.

In the study, experimenters increased or decreased the excitability of the primary motor and primary visual cortex by the application of 7 minutes of anodal and cathodal tDCS in healthy human subjects while they were performing a visuomotor tracking task involving hand movements. The experimenters found that the percentage of correct tracking movements increased specifically during and immediately after cathodal stimulation, which decreases cortical excitability, only when V5 was stimulated. None of the other stimulation conditions affected visuomotor performance.

2.2 The effects of tDCS on perceptual processing

Results from a research paper clearly show that tDCS augments both skill acquisition and retention in a complex detection task (Falcone et al., 2012). Further, they suggest that the benefits are rooted in an improvement in sensitivity, rather than changes in response bias. Stimulation-driven acceleration of learning and its retention over 24 hours may result from increased activation of prefrontal cortical regions that provide top down attentional control signals to object recognition areas.

The researchers examined the influence of stimulation of the right inferior frontal cortex using tDCS on perceptual learning and retention, using signal detection theory to distinguish effects on perceptual sensitivity from response bias. On completion of training, experimenters found that participants in the active stimulation group had more than double the perceptual sensitivity of the control group. Furthermore, the performance enhancement was maintained for 24 hours.

2.3 The effects of tDCS on target detection

coffman study.jpg
Figure 1: Percentage of correct responses during different phases of training and testing. (a) Shows the effect of training. Participants’ performance increased significantly with training across both experiments and remained significantly different from baseline following the 1-h break. (b) Shows the effect of current. Participants in Experiment 2 performed in a similar manner as those in Experiment 1 (broken lines).

In a study, the authors concluded that indicate that the
enhancement of performance with tDCS is sensitive to stimulus repetition and target presence, but not to changes in expectancy, mood, or type of blinded task design (Coffman et al., 2012).

The experimenters applied tDCS over the right inferior frontal cortex at 0.1 mA or 2.0 mA for the first 30 min. Participants were tested immediately before and after training and again 1 h later. Experimenters found that the higher tDCS current was associated with increased performance for all test stimuli, but was greatest for repeated test stimuli with the presence of hidden-targets. This finding was replicated in a second set of subjects using a double-blind task design. Accuracy for target detection discrimination sensitivity (hits - false alarms) was greater for 2.0 mA current (1.77) compared with 0.1 mA (0.95), with no differences in response bias.

2.4 The effects of tDCS on memory

Literature also states findings that support the existence of a consolidation mechanism, susceptible to anodal tDCS, which contributes to offline effects but not to online effects or long-term retention (Reis et al., 2009).

The authors investigated the effect of non-invasive cortical stimulation on the extended time course of learning a novel and challenging motor skill task. A skill measure was chosen to reflect shifts in the task’s speed–accuracy tradeoff function (SAF). Subjects practiced the task over 5 consecutive days while receiving tDCS over the primary motor cortex (M1). Using the skill measure, Reis and colleagues assessed the impact of anodal (relative to sham) tDCS on both within day (online) and between day (offline) effects and on the rate of forgetting during a 3-month follow-up (long-term retention). The research found that there was greater total (online plus offline) skill acquisition with anodal tDCS compared to sham, which was mediated through a selective enhancement of offline effects. Anodal tDCS did not change the rate of forgetting relative to sham across the 3-month follow-up period, and consequently the skill measure remained greater with anodal tDCS at 3 months.

2.5 The effects of tDCS on identifying concealed objects

Figure 2: Examples of training and testing stimuli. Test stimuli were either repeated from training (centre panels) or novel, but similar to those viewed during training (right panels). Half of the images contained objects (upper panels), while the other half did not (lower panels). The target object is the rectangular gray object located behind the metal trash can, which indicates an explosive device.

Brain imaging and stimulation studies suggest that right frontal and parietal
cortex are involved in learning to identify concealed objects in naturalistic surroundings (Clark et al., 2012). Furthermore, Clark and colleagues suggest that the application of anodal tDCS over these regions can greatly increase learning.

In this paper, the experimenters used tDCS to increase learning rate in a novel, minimally guided discovery-learning paradigm. 96 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. The authors found that anodal 2.0 mA tDCS performed for 30 min 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.

3. Analysis:

The article is centred on a report by the Royal Society, Britain's national academy of science. The issue being discussed contains universal relevance because the details of the report can imaginably impact any one person - and a wide range of professions. The article is targeted at the lay man - it summarises the key findings in the original report, omits neuroscientific jargon, figures, tables, and other key elements of a scientific report, and concisely and selectively incorporates the opinion of a select group of people.

The article was written in the Sydney Morning Herald. Fairfax owns SMH, and Fairfax is a corporation that ultimately exists to make money. As such, they will distort the truth if it allows them to make money. For example, the headline and the subsequent image underneath it do not describe the content of the article. They imply the article will talk about designer drugs that will improve shooting, whereas the relevant literature only forms two lines in the whole article. Additionally, there are no references, no evidence for their claim of a drug that will improve shooting. This can be considered a major drawback as it is very misleading to the reader.

The authors do compromise much in depth of information to keep the article simple. For instance, the article quotes the lead researcher involved in the study on tDCS. They don't quote the study directly, but by using the person most influential in shaping the paper, the article gains credibility in accurately reporting what the study was about, what was found in the results, and how the results were interpreted. The article initially quotes Rod Flower, chairman of the report's working group, and quotes Scott Grafton at the University of California, another researcher involved in findings in the relevant field. The article also includes findings from Darpa, the US military research organisation, providing some context for the report, and giving some insight into the current state of research the field.

To their credit, the authors go to great lengths to emphasise the importance of ethics in brain-machine interfaces, sourcing a Rod Flower, who is also a professor of pharmacology at the William Harvey Research Institute at Barts and the London hospital. As such the article has a sense of balance, reporting as much on the apparent benefits from the application of the research, and contrasting the benefits with its potential ethical ramifications.

4. Appendix (Search Strategy):

We came upon this article during our first group meeting when we searched through the neuroscience article archives of the Sydney Morning Herald website (a webpage we all frequented). We were immediately intrigued by the title “Take it, it’ll make you shoot better” and upon reading the article, became fascinated by the unique and somewhat futuristic sounding idea of a neuroscientific procedure that involved the use of electrical stimulation of the brain to enhance task performance. The article proposed many uses for the new technology such as improving attention and memory and aiding in the treatment of psychiatric disorders, however we became particularly interested in the article’s main focus, which was the preliminary use of tDCS by the US military to enhance soldiers’ perceptual processing of targets.

When the topic was approved, Dr. Vickery mentioned that there would be alot of local research on the subject and so upon beginning this project we realised the significance of rigorous contextual investigation.

The main search engines we used were Scopus, PsycINFO and other UNSW scientific databases. Our research produced a rich selection of very contemporary studies. We considered many sources but only included and analysed those that were specifically relevant to the enhancing effects of tDCS on perceptual processing as contained in the SMH article.

Following the completion of the draft and reviewer comments we made a number of changes to our project after considering the feedback from our peers:
  1. We considered the comment from Thomas Barlow that the context section of our page was 'too dry' as it was an analysis of one relevant study after the other. To remedy this we divided our context section into the implications of tDCS that were discussed in the article and analysed our research in terms of these implications. We also added more images to our page and made it more aesthetically appealing and engaging overall.
  2. We took on board Satya Sinha's feedback that we should 'add subheadings, number the different sections, and display these changes in the Table Of Contents'. As such, every study has its own subsection in the context part of the project, have been numbered in chronological order, and are accessible in the Table Of Contents.
  3. We also used Kathryn Kacperek's advice on clarifying the procedure of anodal and cathodal stimulation. We re-wrote the part and we are now very confident in its clarity.

The material contained in the Wiki page is therefore an examination of relevant sources and a critical analysis of our media item, which aim to elucidate the process and wide reaching effects of this ground-breaking new technology.

neural researc.png
Neural research ... a future weapon.


Antal, A., Nitsche, M.A., Kruse, W., Kincses, T.Z., Hoffman, K., & Paulus, W. (2004). Facilitation of visuo-motor learning by transcranial direct current stimulation of the motor and extrastriate visual areas in humans. European Journal of Neuroscience, 19(10), 521-527.

Brunoni, A. R., Nitsche, M. A., Bolognini, N., Bikson, M., Wagner, T., Merabet, L., et al. (2012). Clinical research with transcranial diresct current stimultion (tDCS): Challenges and future directions. Brain Stimulation Journal.

Clark, V.P., Coffman, B.A., Mayer, A.R., Weisend, M.P., Lane, T.D.R., Calhoun, V.D., Raybourn, E.M., Garcia, C.M., & Wassermann, E.M. (2012). TDCS guided using fMRI significantly accelerates learning to identify concealed objects. NeuroImage, 59(1), 117-128.

Coffman B.A., Trumbo, M.C., Flores, R.A., Garcia, C.M., van der Merwe, A.J., Wassermann, E.M., Weisend, M.P., & Clark, V.P. (2012). Impact of tDCS on performance and learning of target detection: interaction with stimulus characteristics and experimental. Neuropsychologia, 50(7), 1594-1602.

Falcone, B., Coffman, B.A., Clark, V.P., & Parasuraman, R. (2012). Transcranial Direct Current Stimulation Augments Perceptual Sensitivity and 24-Hour Retention in a Complex Threat Detection Task. PLoS ONE, 7(4), 1-10.

Kabakov, A., Muller , P., Pascual-Leone, A., Jensen, F., & Rotenberg, A. (2012). Contribution of axonal orientation to pathway-dependent modulation of excitatory transmission by direct current stimulation in isolated rat hippocampus. Children's Hospital Boston, Department of Neurology. PubMed.

Loo, C., Sachdev, P., & Arul-Anandam, A. P. ( 2009). Transcranial direct current stimulation - what is the evidence for its efficacy and safety? University of New South Wales, Prince of Wales Hospital, School of Psychiatry. Medicine Reports Ltd.

Madhavan, S., & Shah, B. (2012). Enhancing motor skill learning with transcrannial direct current stimulation – a concise review with applications to stroke. Frontiers in Psychiatry, 3, 1-9.

Reis, J., Schambra, H.M., Cohen, L.G., Buch, E.R., Fritsch, B., Zarahn, E., Celnik, P.A., & Krakauer, J.W. (2009). Noninvasive cortical stimulation enhances motor skill acquisition over multiple days through an effect on consolidation . PNAS, 106(5), 1590-1595.