Posts Tagged tES
Recruitment Status : Recruiting
[Abstract] Basic and functional effects of transcranial Electrical Stimulation (tES)—An introduction
We propose to fuse two currently separate research lines on novel therapies for stroke rehabilitation: brain-computer interface (BCI) training and transcranial electrical stimulation (TES). Speciﬁcally, we show that BCI technology can be used to learn personalized decoding models that relate the global conﬁguration of brain rhythms in individual subjects (as measured by EEG) to their motor performance during 3D reaching movements. We demonstrate that our models capture substantial across-subject heterogeneity, and argue that this heterogeneity is a likely cause of limited effect sizes observed in TES for enhancing motor performance. We conclude by discussing how our personalized models can be used to derive optimal TES parameters, e.g., stimulation site and frequency, for individual patients.
Motor deﬁcits are one of the most common outcomes of stroke. According to the World Health Organization, 15 million people worldwide suffer a stroke each year. Of these, ﬁve million are permanently disabled. For this third, upper limb weakness and loss of hand function are among the most devastating types of disabilities, which affect the quality of their daily life . Despite a wide range of rehabilitation therapies, including medication treatment , conventional physiotherapy , and robot physiotherapy , only approximately 20% of patients achieve some form of functional recovery in the ﬁrst six months , .
Current research on novel therapies includes neurofeedback training based on brain-computer interface (BCI) technology and transcranial electrical stimulation (TES). The former approach attempts to support cortical reorganization by providing haptic feedback with a robotic exoskeleton that is congruent to movement attempts, as decoded in real-time from neuroimaging data , . The latter type of research aims to reorganize cortical networks in a way that supports motor performance, because post-stroke alterations of cortical networks have been found to correlate with the severity of motor deﬁcits , . While initial evidence suggested that both approaches, BCIbased training  and TES , have a positive impact, the signiﬁcance of these results over conventional physiotherapy was not always achieved by different studies , , .
One potential explanation for the difﬁculty to replicate the initially promising ﬁndings is the heterogeneity of stroke patients. Different locations of stroke-induced structural changes
are likely to result in substantial across-patient variance in the functional reorganization of cortical networks. As a result, not all patients may beneﬁt from the same neurofeedback or stimulation protocol. We thus propose to fuse these two research themes and use BCI technology to learn personalized models that relate the conﬁguration of cortical networks to each patient’s motor deﬁcits. These personalized models may then be used to predict which TES parameters, e.g., spatial location and frequency band, optimally support rehabilitation in each individual patient.
In this study, we address the ﬁrst step towards personalized TES for stroke rehabilitation. Using a transfer learning framework developed in our group , we show how to create personalized decoding models that relate the EEG of healthy subjects during a 3D reaching task to their motor performance in individual trials. We further demonstrate that the resulting decoding models capture substantial acrosssubject heterogeneity, thereby providing empirical support for the need to personalize models. We conclude by reviewing our ﬁndings in the light of TES studies to improve motor performance in healthy subjects, and discuss how personalized TES parameters may be derived from our models.[…]
[Abstract] Transcranial Electrical Stimulation in Post-Stroke Cognitive Rehabilitation: European Psychologist: Vol 21, No 1
The current book starts with an overview of the past, by providing a brief history of how transcranial electrical stimulation has been used to enhance cognition and improve health. The rest of the book discusses current knowledge in the field, and provides an excellent overview of different lines of research, such as those in animals, healthy humans, and patients. The aim of this last chapter is to discuss further directions for research in the field of transcranial electrical stimulation (tES).
Over the different chapters it becomes clear that research using tES has demonstrated improvements in different cognitive and non-cognitive functions, ranging from perception and motor movement to attention, working memory, language, and mathematical abilities. These results show that such improvements are not limited to typical populations but can also affect young adults and the elderly, and neurological and psychiatric patients. These results are indeed promising, but suffer from some limitations that have been discussed in various of these chapters, as well as elsewhere (Pascual-Leone, Horvath, & Robertson, 2012; Rothwell, 2012). Some of these limitations include low sample size, artificial tasks with reduced ecological validity, lack of consistency in the montage that led to the enhancement effects, and need for replication. I will not extend the discussion on these points, as they are rather trivial and are not limited to the current field. Instead I will discuss what I perceive as the directions in which the field of tES should, and hopefully will, go. It was difficult deciding which sections to include in this respect, and I have chosen to limit our discussion to 10 sections. I will conclude the chapter with a brief discussion of the challenges that the field is facing.
Low-intensity transcranial electrical stimulation (tES) methods are a group of noninvasive brain stimulation techniques, whereby currents are applied with intensities typically ranging between 1 and 2 mA, through the human scalp. These techniques have been shown to induce changes in cortical excitability and activity during and after the stimulation in a reversible manner. They include transcranial direct current simulation (tDCS), transcranial alternating current simulation (tACS), and transcranial random noise stimulation (tRNS).
Currently, an increasing number of studies have been published regarding the effects of tES on cognitive performance and behavior. Processes of learning and increases in cognitive performance are accompanied by changes in cortical plasticity. tES can impact upon these processes and is able to affect task execution. Many studies have been based on the accepted idea that by increasing cortical excitability (e.g., by applying anodal tDCS) or coherence of oscillatory activity (e.g., by applying tACS) an increase in performance should be detected; however, a number of studies now suggest that the basic knowledge of the mechanisms of action is insufficient to predict the outcome of applied stimulation on the execution of a cognitive or behavioral task, and so far no standard paradigms for increasing cortical plasticity changes during learning or cognitive tasks have been established.
The aim of this review is to summarize recent findings with regard to the effects of tES on behavior concentrating on the motor and visual areas…