How does the brain determine what to learn and what not to learn? Previous studies showed that a feature or stimulus on which subjects performed a task was learned, while the features or stimuli that were irrelevant to the task were not learned. This led some researchers to conclude that attention to a stimulus was necessary for the stimulus to be learned. This thought was challenged by the discovery of a task-irrelevant perceptual learning, in which learning occurred by mere exposure to the unattended and subthreshold stimulus. However, this exposure-based learning does not necessarily indicate that all presented stimuli are learned. Rather, recent studies showed that the occurrence of this learning was very selective for the following new findings: unattended stimulus learning occurred only (1) when the unattended stimulus was associated temporally with the processing of an attended target, (2) when the unattended stimulus was synchronously presented with reinforcers, such as internal or external rewards, and (3) when the unattended stimulus had subliminal properties. These selectivities suggest some degrees of similarity between task-relevant and task-irrelevant perceptual learning, which has been the motivation for making a united model in which both task-relevant and task-irrelevant learning are formed with similar or same mechanisms.
Excessive use of online games can have negative influences on mental health and daily functioning. Although the effects of transcranial direct current stimulation (tDCS) have been investigated for the treatment of addiction, it has not been evaluated for excessive online game use. This study aimed to investigate the feasibility and tolerability of tDCS over the dorsolateral prefrontal cortex (DLPFC) in online gamers.
A total of 15 online gamers received 12 active tDCS sessions over the DLPFC (anodal left/cathodal right, 2 mA for 30 min, 3 times per week for 4 weeks). Before and after tDCS sessions, all participants underwent 18F-ﬂuoro-2-deoxyglucose positron emission tomography scans and completed the Internet Addiction Test (IAT), Brief Self Control Scale (BSCS), and Beck Depression Inventory-II (BDI-II).
After tDCS sessions, weekly hours spent on games (p = .02) and scores of IAT (p < .001) and BDI-II (p = .01) were decreased, whereas BSCS score was increased (p = .01). Increases in self-control were associated with decreases in both addiction severity (p = .002) and time spent on games (p = .02). Moreover, abnormal right-greater-than-left asymmetry of regional cerebral glucose metabolism in the DLPFC was partially alleviated (p = .04).
Our preliminary results suggest that tDCS may be useful for reducing online game use by improving interhemispheric balance of glucose metabolism in the DLPFC and enhancing self-control. Larger sham-controlled studies with longer follow-up period are warranted to validate the efficacy of tDCS in gamers.
Authors:Sung Bin Park, Byung Heung Park, Sang Mun Jeong, Jin Mok Hur, Chung Seok Seo, Seung-Hoon Choi, and Seong Won Park
Electrochemical behavior of the reduction of uranium oxide was studied in a LiCl-Li2O molten salt system with an integrated cathode assembly. The mechanism for the electrolytic reduction of uranium oxide was
studied through cyclic voltammetry. By means of a chronopotentiometry, the effects of the thickness of the uranium oxide,
the thickness of the MgO membrane and the material of the conductor of an integrated cathode assembly on the overpotential
of the cathode were investigated. From the voltamograms, the reduction potential of the uranium oxide and Li2O was obtained and the two mechanisms of the electrolytic reduction were considered with regard to the applied cathode potential.
From the chronopotentiograms, the exchange current, the transfer coefficient and the maximum allowable current based on the
Tafel behavior were obtained with regard to the thickness of the uranium oxide, and of the MgO membrane and the material of
the conductor of an integrated cathode assembly.
Authors:Hyeonseok Jeong, Jin Kyoung Oh, Eun Kyoung Choi, Jooyeon Jamie Im, Sujung Yoon, Helena Knotkova, Marom Bikson, In-Uk Song, Sang Hoon Lee, and Yong-An Chung
Background and aims
Some online gamers may encounter difficulties in controlling their gaming behavior. Previous studies have demonstrated beneficial effects of transcranial direct current stimulation (tDCS) on various kinds of addiction. This study investigated the effects of tDCS on addictive behavior and regional cerebral metabolic rate of glucose (rCMRglu) in problematic online gamers.
Problematic online gamers were randomized and received 12 sessions of either active (n = 13) or sham tDCS (n = 13) to the dorsolateral prefrontal cortex over 4 weeks (anode F3/cathode F4, 2 mA for 30 min, 3 sessions per week). Participants underwent brain 18F-fluoro-2-deoxyglucose positron emission tomography scans and completed questionnaires including the Internet Addiction Test (IAT), Brief Self-Control Scale (BSCS), and Behavioral Inhibition System/Behavioral Activation System scales (BIS/BAS) at the baseline and 4-week follow-up.
Significant decreases in time spent on gaming (P = 0.005), BIS (P = 0.03), BAS-fun seeking (P = 0.04), and BAS-reward responsiveness (P = 0.01), and increases in BSCS (P = 0.03) were found in the active tDCS group, while decreases in IAT were shown in both groups (P < 0.001). Group-by-time interaction effects were not significant for these measures. Increases in BSCS scores were correlated with decreases in IAT scores in the active group (β = −0.85, P < 0.001). rCMRglu in the left putamen, pallidum, and insula was increased in the active group compared to the sham group (P for interaction < 0.001).
Discussion and conclusions
tDCS may be beneficial for problematic online gaming potentially through changes in self-control, motivation, and striatal/insular metabolism. Further larger studies with longer follow-up period are warranted to confirm our findings.