Hamilton, Roy H

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Now showing 1 - 10 of 10
  • Publication
    Fast Forward: Supramarginal Gyrus Stimulation Alters Time Measurement
    (2010-01-01) Hamilton, Roy; Turkeltaub, Peter; Wiener, Martin; Coslett, H. Branch; Matell, Matthew S.
    The neural basis of temporal processing is unclear. We addressed this important issue by performing two experiments in which repetitive transcranial magnetic stimulation (rTMS) was administered in different sessions to the left or right supramarginal gyrus (SMG) or vertex; in both tasks, two visual stimuli were presented serially and subjects were asked to judge if the second stimulus was longer than the first (standard) stimulus. rTMS was presented on 50% of trials. Consistent with a previous literature demonstrating the effect of auditory clicks on temporal judgment, rTMS was associated with a tendency to perceive the paired visual stimulus as longer in all conditions. Crucially, rTMS to the right SMG was associated with a significantly greater subjective prolongation of the associated visual stimulus in both experiments. These findings demonstrate that the right SMG is an important element of the neural system underlying temporal processing and, as discussed, have implications for neural and cognitive models of temporal perception and attention.
  • Publication
    Cognitive Enhancement
    (2014-01-01) Farah, Martha J; Ilieva, Irena; Hamilton, Roy; Smith, M. Elizabeth
    Cognitive enhancement refers to the improvement of cognitive ability in normal healthy individuals. In this article, we focus on the use of pharmaceutical agents and brain stimulation for cognitive enhancement, reviewing the most common methods of pharmacologic and electronic cognitive enhancement, and the mechanisms by which they are believed to work, the effectiveness of these methods and their prevalence. We note the many gaps in our knowledge of these matters, including open questions about the size, reliability and nature of the enhancing effects, and we conclude with recommendations for further research.
  • Publication
    Stimulation of the Prefrontal Cortex Reduces Intentions to Commit Aggression: A Randomized, Double-Blind, Placebo-Controlled, Stratified, Parallel-Group Trial
    (2018-07-18) Choy, Olivia; Raine, Adrian; Hamilton, Roy
    Although prefrontal brain impairments are one of the best-replicated brain imaging findings in relation to aggression, little is known about the causal role of this brain region. This study tests whether stimulating the dorsolateral prefrontal cortex using transcranial direct current stimulation (tDCS) reduces the likelihood of engaging in aggressive acts, and the mechanism underlying this relationship. In a double-blind, stratified, placebo-controlled, parallel-group, randomized trial, 81 human adults (36 males, 45 females) were randomly assigned to an active (N = 39) or placebo (N = 42) condition, and then followed up 1 d after the experiment session. Intentions to commit aggressive acts and behavioral aggression were assessed using hypothetical vignettes and a behavioral task, respectively. The secondary outcome was the perception of the moral wrongfulness of the aggressive acts. Compared with the sham controls, participants who received anodal stimulation reported being less likely to commit physical and sexual assault (p < 0.01). They also judged aggressive acts as more morally wrong (p < 0.05). Perceptions of greater moral wrongfulness regarding the aggressive acts accounted for 31% of the total effect of tDCS on intentions to commit aggression. Results provide experimental evidence that increasing activity in the prefrontal cortex can reduce intentions to commit aggression and enhance perceptions of the moral wrongfulness of the aggressive acts. Findings shed light on the biological underpinnings of aggression and theoretically have the potential to inform future interventions for aggression and violence.
  • Publication
    The Brain, Cognitive Enhancement Devices, and European Regulation
    (2014-09-01) Kuersten, Andreas; Hamilton, Roy H
    From the Introduction: Exciting advances in neuroscience have given rise to devices—now being sold worldwide—which hold the promise of enhancing human cognition. This concerns Maslen et al.—authors of the article, The Regulation of Cognitive Enhancement Devices: Extending the Medical Model—because there are unaddressed possible harms from such equipment. Cognitive enhancement devices (CEDs) are currently entering the European market without special regulations. Their unique ability to influence the brain in potentially deleterious ways is not being accounted for by the law, exposing consumers to risk. In arguing for such regulation, Maslen et al. present risk analyses of certain devices that interact with the brain. They then propose CED-specific additions to existing European medical device regulation. First, they recommend a positive list of CEDs to be regulated. Second, they offer a three-tiered framework for categorizing CEDs, determining market approval, and what level of government scrutiny they receive based on risks and benefits. The authors’ assessment, while demonstrating legitimate concerns, presents a flawed analysis of CEDs and is ultimately unnecessary. We disagree with their definition of CEDs and classifications for certain devices. Moreover, we believe that the regulatory gap Maslen et al. seek to address is not as profound as they portray. Steps are underway to fill this gap in the immediate future, obviating the need for their proposal. Finally, we argue that the authors incorrectly balance risk and benefit when determining CED market approval.
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  • Publication
    Anodal tDCS to Right Dorsolateral Prefrontal Cortex Facilitates Performance for Novice Jazz Improvisers but Hinders Experts
    (2016-11-16) Rosen, David S; Erickson, Brian; Kim, Youngmoo E; Mirman, Daniel; Hamilton, Roy H
    Research on creative cognition reveals a fundamental disagreement about the nature of creative thought, specifically, whether it is primarily based on automatic, associative (Type-1) or executive, controlled (Type-2) processes. We hypothesized that Type-1 and Type-2 processes make differential contributions to creative production that depend on domain expertise. We tested this hypothesis with jazz pianists whose expertise was indexed by the number of public performances given. Previous fMRI studies of musical improvisation have reported that domain expertise is characterized by deactivation of the right-dorsolateral prefrontal cortex (r-DLPFC), a brain area associated with Type-2 executive processing. We used anodal, cathodal, and sham transcranial direct current stimulation (tDCS) applied over r-DLPFC with the reference electrode on the contralateral mastoid (1.5 mA for 15 min, except for sham) to modulate the quality of the pianists' performances while they improvised over chords with drum and bass accompaniment. Jazz experts rated each improvisation for creativity, esthetic appeal, and technical proficiency. There was no main effect of anodal or cathodal stimulation on ratings compared to sham; however, a significant interaction between anodal tDCS and expertise emerged such that stimulation benefitted musicians with less experience but hindered those with more experience. We interpret these results as evidence for a dual-process model of creativity in which novices and experts differentially engage Type-1 and Type-2 processes during creative production.
  • Publication
    Does Transcranial Direct Current Stimulation Improve Healthy Working Memory?: A Meta-Analytic Review
    (2016-08-01) Mancuso, Lauren E.; Hamilton, Roy; Ilieva, Irena P.; Farah, Martha J.
    Transcranial direct current stimulation (tDCS) has been reported to improve working memory (WM) performance in healthy individuals, suggesting its value as a means of cognitive enhancement. However, recent meta-analyses concluded that tDCS has little or no effect on WM in healthy participants. In this article, we review reasons why these meta-analyses may have underestimated the effect of tDCS on WM and report a more comprehensive and arguably more sensitive meta-analysis. Consistent with our interest in enhancement, we focused on anodal stimulation. Thirty-one articles matched inclusion criteria and were included in four primary meta-analyses assessing the WM effects of anodal stimulation over the left and right dorsolateral pFC (DLPFC) and right parietal lobe as well as left DLPFC stimulation coupled with WM training. These analyses revealed a small but significant effect of left DLPFC stimulation coupled with WM training. Left DLPFC stimulation alone also enhanced WM performance, but the effect was reduced to nonsignificance after correction for publication bias. No other effects were significant, including a variety of tested moderators. Additional meta-analyses were undertaken with study selection criteria based on previous meta-analyses, to reassess the findings from these studies using the analytic methods of this study. These analyses revealed a mix of significant and nonsignificant small effects. We conclude that the primary WM enhancement potential of tDCS probably lies in its use during training.
  • Publication
  • Publication
    Does Transcranial Direct Current Stimulation Improve Healthy Working Memory?: A Meta-analytic Review
    (2016-08-01) Mancuso, Lauren E.; Hamilton, Roy H.; Ilieva, Irena P.; Farah, Martha J.
    Transcranial direct current stimulation (tDCS) has been reported to improve working memory (WM) performance in healthy individuals, suggesting its value as a means of cognitive enhancement. However, recent meta-analyses concluded that tDCS has little or no effect on WM in healthy participants. In this article, we review reasons why these meta-analyses may have underestimated the effect of tDCS on WM and report a more comprehensive and arguably more sensitive meta-analysis. Consistent with our interest in enhancement, we focused on anodal stimulation. Thirty-one articles matched inclusion criteria and were included in four primary meta-analyses assessing the WM effects of anodal stimulation over the left and right dorsolateral pFC (DLPFC) and right parietal lobe as well as left DLPFC stimulation coupled with WM training. These analyses revealed a small but significant effect of left DLPFC stimulation coupled with WM training. Left DLPFC stimulation alone also enhanced WM performance, but the effect was reduced to nonsignificance after correction for publication bias. No other effects were significant, including a variety of tested moderators. Additional meta-analyses were undertaken with study selection criteria based on previous meta-analyses, to reassess the findings from these studies using the analytic methods of this study. These analyses revealed a mix of significant and nonsignificant small effects. We conclude that the primary WM enhancement potential of tDCS probably lies in its use during training.
  • Publication
    Ethics of the Electrified Mind: Defining Issues and Perspectives on the Principled Use of Brain Stimulation in Medical Research and Clinical Care
    (2014-01-01) Cabrera, Laura Y; Evans, Emily L; Hamilton, Roy H
    In recent years, non-pharmacologic approaches to modifying human neural activity have gained increasing attention. One of these approaches is brain stimulation, which involves either the direct application of electrical current to structures in the nervous system or the indirect application of current by means of electromagnetic induction. Interventions that manipulate the brain have generally been regarded as having both the potential to alleviate devastating brain-related conditions and the capacity to create unforeseen and unwanted consequences. Hence, although brain stimulation techniques offer considerable benefits to society, they also raise a number of ethical concerns. In this paper we will address various dilemmas related to brain stimulation in the context of clinical practice and biomedical research. We will survey current work involving deep brain stimulation, transcranial magnetic stimulation and transcranial direct current stimulation. We will reflect upon relevant similarities and differences between them, and consider some potentially problematic issues that may arise within the framework of established principles of medical ethics: nonmaleficence and beneficence, autonomy, and justice.