Challenges of proper placebo control for non‐invasive brain stimulation in clinical and experimental applications

Davis, Nick J.; Gold, Edward; Pascual‐Leone, Álvaro; Bracewell, R. Martyn

doi:10.1111/ejn.12307

Cited by 98 publications

(93 citation statements)

References 42 publications

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“…At the end of the session, current was automatically ramped down to 0.0 mA over a 10-s period. The sham tDCS condition was administered using an inactive stimulation protocol, rather than the “off-target” active protocol, in order to minimize subject risk (Davis et al 2013). The same electrode montage, session duration, and ramp-up procedures as the real tDCS condition were followed, except that current was only delivered for the first 60 s of the session before being automatically ramped back down to zero.…”

Section: Methodsmentioning

confidence: 99%

Effects of transcranial direct current stimulation (tDCS) on multiscale complexity of dual-task postural control in older adults

Zhou

et al. 2015

Exp Brain Res

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Transcranial direct current stimulation (tDCS) targeting the prefrontal cortex reduces the size and speed of standing postural sway in younger adults, particularly when performing a cognitive dual task. Here, we hypothesized that tDCS would alter the complex dynamics of postural sway as quantified by multiscale entropy (MSE). Twenty healthy older adults completed two study visits. Center-of-pressure (COP) fluctuations were recorded during single-task (i.e., quiet standing) and dual-task (i.e., standing while performing serial subtractions) conditions, both before and after a 20-min session of real or sham tDCS. MSE was used to estimate COP complexity within each condition. The percentage change in complexity from single- to dual-task conditions (i.e., dual-task cost) was also calculated. Before tDCS, COP complexity was lower (p = 0.04) in the dual-task condition as compared to the single-task condition. Neither real nor sham tDCS altered complexity in the single-task condition. As compared to sham tDCS, real tDCS increased complexity in the dual-task condition (p = 0.02) and induced a trend toward improved serial subtraction performance (p = 0.09). Moreover, those subjects with lower dual-task COP complexity at baseline exhibited greater percentage increases in complexity following real tDCS (R = −0.39, p = 0.05). Real tDCS also reduced the dual-task cost to complexity (p = 0.02), while sham stimulation had no effect. A single session of tDCS targeting the prefrontal cortex increased standing postural sway complexity with concurrent non-postural cognitive task. This form of noninvasive brain stimulation may be a safe strategy to acutely improve postural control by enhancing the system's capacity to adapt to stressors.

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Section: Methodsmentioning

confidence: 99%

Effects of transcranial direct current stimulation (tDCS) on multiscale complexity of dual-task postural control in older adults

Zhou

et al. 2015

Exp Brain Res

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“…For sham stimulation the figure-of-eight coil was oriented tangentially over the scalp vertex, such that the magnetic flux was dispersed in the air (e.g. Davis et al, 2014).…”

Section: Tmsmentioning

confidence: 99%

Timing of spatial priming within the fronto-parietal attention network: A TMS study

et al. 2015

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“…Ensure that the overall number, gender and average age of participants is comparable between groups as in Pope and Miall . However, differentiating sham and real stimulation is easier at higher current strengths 42 . This could be problematic in a within-participants design, but not so in a between-participants design as described here.…”

Section: Performing Cerebellar Tdcsmentioning

confidence: 99%

Modulating Cognition Using Transcranial Direct Current Stimulation of the Cerebellum

Pope

2015

JoVE

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Numerous studies have emerged recently that demonstrate the possibility of modulating, and in some cases enhancing, cognitive processes by exciting brain regions involved in working memory and attention using transcranial electrical brain stimulation. Some researchers now believe the cerebellum supports cognition, possibly via a remote neuromodulatory effect on the prefrontal cortex. This paper describes a procedure for investigating a role for the cerebellum in cognition using transcranial direct current stimulation (tDCS), and a selection of information-processing tasks of varying task difficulty, which have previously been shown to involve working memory, attention and cerebellar functioning. One task is called the Paced Auditory Serial Addition Task (PASAT) and the other a novel variant of this task called the Paced Auditory Serial Subtraction Task (PASST). A verb generation task and its two controls (noun and verb reading) were also investigated. All five tasks were performed by three separate groups of participants, before and after the modulation of cortico-cerebellar connectivity using anodal, cathodal or sham tDCS over the right cerebellar cortex. The procedure demonstrates how performance (accuracy, verbal response latency and variability) could be selectively improved after cathodal stimulation, but only during tasks that the participants rated as difficult, and not easy. Performance was unchanged by anodal or sham stimulation. These findings demonstrate a role for the cerebellum in cognition, whereby activity in the left prefrontal cortex is likely dis-inhibited by cathodal tDCS over the right cerebellar cortex. Transcranial brain stimulation is growing in popularity in various labs and clinics. However, the after-effects of tDCS are inconsistent between individuals and not always polarity-specific, and may even be task-or loadspecific, all of which requires further study. Future efforts might also be guided towards neuro-enhancement in cerebellar patients presenting with cognitive impairment once a better understanding of brain stimulation mechanisms has emerged.

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Challenges of proper placebo control for non‐invasive brain stimulation in clinical and experimental applications

Cited by 98 publications

References 42 publications

Effects of transcranial direct current stimulation (tDCS) on multiscale complexity of dual-task postural control in older adults

Effects of transcranial direct current stimulation (tDCS) on multiscale complexity of dual-task postural control in older adults

Timing of spatial priming within the fronto-parietal attention network: A TMS study

Modulating Cognition Using Transcranial Direct Current Stimulation of the Cerebellum

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