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Bi-hemispheric effects on corticospinal excitability induced by repeated sessions of imagery versus observation of actions Restor Neurol Neurosci. 2012;30(6):481-9. doi: 10.3233/RNN-2012-120241. Bi-hemispheric effects on corticospinal excitability induced by repeated sessions of imagery versus observation of actions. Bianco G, Feurra M, Fadiga L, Rossi A, Rossi S. Source Dipartimento di Neuroscienze, Sezione Neurologia and Neurofisiologia Clinica, Azienda Ospedaliera Universitaria Senese, Siena, Italy.
No full textPURPOSE:
To investigate whether repeated sessions of motor imagery and action observation modulate corticospinal excitability (CE) over time, whether these processes are susceptible of any training effect and if such effect might be different for the dominant and non dominant hemisphere.
METHODS:
11 subjects underwent three sessions, spaced 5-7 days, of single-pulse Transcranial Magnetic Stimulation (TMS) of right and left primary motor cortex. Subjects were asked to imagine or observe pinch-grip actions with either hand. Motor evoked potentials (MEPs) were recorded bilaterally from the First Dorsal Interosseus muscle (FDI), acting as main agonist during precision grip.
RESULTS:
Motor imagery consistently enhanced CE with respect to action observation, regardless of hemispheric lateralization and of separate testing sessions. However, motor imagery increased CE only when measured over the non-dominant hemisphere, during the third session with respect to the first one. The increase of CE induced by action observation in the first session was not further modified throughout the remaining two sessions, in either hemisphere.
CONCLUSIONS:
Results suggest that motor imagery is sustained by a cortical network susceptible to training effects only for the non-dominant hemisphere. Such an effect was lacking for action observation, likely because of the innateness of these mechanisms. Results might have implications for rehabilitative purpose
Investigating and modulating physiological and pathological brain oscillations: The role of oscillatory activity in neural plasticity
Get PDFOverclock your brain for gaming? Ethical, social and health care risks
No full text“Overclock your brain using transcranial Direct Current Stimulation (tDCS) to increase the plasticity of your brain. Make your synapses fire faster. Let the force of electricity excite your neurons into firing faster”
This is how Foc.us Labs (http://www.foc.us) introduced a new device to improve performance at video-games. The device is meant for self-administration of imperceptible, transcranial currents to the prefrontal cortex, and can be tuned by a smartphone app. Everybody can buy it by a mouse click. This is an example of how market goals may overcome ethics by threatening users' and gamers' health and imposing high social risks.
Indeed, the boundaries between video-gaming for fun, for money, and the development of gaming addiction are subtle, and hence easily crossable. In the last decade, the online gaming scenario has completely changed. There has been an exponential growth of platforms and dedicated portals, along with a decrease of gamers' age. According to a 2012 survey (Forbes, Dec 20th, 2012, “The Year of eSports”), 4 millions of gamers currently play within the Electronic Sport League, and 8 millions in the North American Major League of Gaming (MLG). During the last year, MLG has observed a +334% increase of live viewings of online tournaments (from 3.5 to 11.7mln; +636% in the last two years), with followers from 175 different countries.
eSport has hence evolved in a very profitable activity. Tech companies support cyber-leagues and major events, providing substantial money prizes (up to 1mln12,000 to 335 billion in 2009, of which $25 billion from online gaming.
Individuals with reduced inhibitory control of prefrontal activity may develop pathological gambling, that is the difficulty to control the impulse to gamble. This may lead to devastating consequences on familiar and social life [1]. Interestingly, Foc.us Labs suggests the prefrontal cortex as target brain site for the self-administration of foc.us tDCS. Given the evidence of a relationship between tDCS on the prefrontal cortex and risk-taking behaviors [2] and [3], prolonged self-administered tDCS over this brain region may induce frequent – if not already addicted – gamers to cross the boundary toward pathological gambling. Social and health care systems do not need additional burden for an already expanding pathology.
tDCS is a non-invasive brain stimulation (NIBS) neuromodulatory technique used in brain research, whose potential clinical applications to treat pathological neuropsychiatric conditions are rapidly growing [4] and [5]. The rationale to use tDCS as a neuromodulatory treatment is that it modifies cortical excitability in a polarity-specific manner, with effects lasting even after the stimulation has ceased. tDCS applied over the prefrontal cortex can induce long-lasting improvements in cognitive abilities [4], as accelerating learning times to identify concealed objects in naturalistic environments, with a dose–response effect of applied current strength [6]. Evidence-based clinical efficacy in large clinical trials on the use of prefrontal tDCS for treatment of depression and other psychiatric disorders is still weak, but randomized, controlled multicentric trials are currently ongoing worldwide (see http://clinicaltrials.gov). These studies will provide an answer about the real efficacy on clinical grounds.
Other types of NIBS techniques (i.e., alternating current and random noise stimulation), which could be also applied through the foc.us device, may speed up logical reasoning abilities by 15% in healthy subjects resolving complex cognitive tasks [7], and improve arithmetic calculation [8], with persisting neuroplastic [4] and [5] and metabolic [9] after-effects. Unlike other NIBS techniques such as repetitive transcranial magnetic stimulation [10], official safety guidelines based on a large consensus within neuroscience community are not yet available for transcranial electrical current stimulation.
Behavioral changes induced so far by transcranial electric stimulation of the brain are generally modest, and do not impact everyday life activities. However, this is not sufficient to reassure about prolonged, uncontrolled, use of self-stimulation outside the lab boundaries. It cannot be excluded that long periods of stimulation, even with intensities of few milliamps, may raise safety issues [4] and [5] especially if the tDCS device is used by a lay person with no medical or credited supervision. In addition, it is worth noticing that animal models of brain damage following transcranial electrical stimulation have been documented [11]. Although a direct transfer of these effects on humans is premature, the sentence “The foc.us gamer headset offers no medical benefits, is not a medical device, and is not regulated by the FDA” appearing on http://www.foc.us is worryingly misleading in light of the above considerations.
Moreover, NIBS is not, and should not be intended as, a magic tool which selectively increases brain performance following a simple additive process. The human brain is a magnificent example of evolution-driven engineering, whose neural networks are dynamically integrated and organized both at local and global scale. The effects of a prolonged exposure to an external intervention might not be intended, as Foc.us labs claims, as merely localized under the electrode, and consequently it would not only affect the single function supported by that region, but also other processes. The prefrontal cortex, which is highly interconnected with much of the brain, including other cortical, subcortical and brain stem sites, is indeed a key hub for several executive, cognitive, affective and emotional functions [12]. It is therefore unlikely that prolonged daily self-stimulation of this region will result only in a selective improvement of gaming abilities. Additionally, potential undesired functional compensation is possible, involving other functional networks and, in turn cognitive domains.
Besides eSport and pathological gambling, there should be a serious concern on what types of consequences an uncontrolled clearance of NIBS through the foc.us or similar “brain-doping” tools may result in. Considering its emerging cognition-boosting capability [7], [8] and [9], or even just its documented efficacy as a painkiller [5], NIBS based on self-administered currents may turn into a worrisome scenario in the next decade. Given its easy accessibility to the public and the misleading communication about potential side-effects that we are documenting here, a firm information campaign supported by the scientific community is needed.
Finally, as Foc.us Labs states itself, the possibility to self-modulate one's own brain activity without any medical or external control makes this practice somehow conceptually similar to the “overclocking” process that gamers easily apply on their computer hardware, by boosting central or graphical processors performance beyond the limit fixed by manufacturers. The direct comparison of informatics and biological models incorporated in the Human-Information-Processing theory is a groundbreaking theoretical advance for the understanding of principles governing human brain functioning. Clearly, there are major concerns about going too far with the brain-computer analogy. It is worth to keep in mind that hardware overclocking usually corresponds to an initial increase in hardware performance, but it inevitably leads to its premature wearing out. What about the brain
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
State-dependent effects of transcranial oscillatory currents on the motor system during action observation
Get PDFWe applied transcranial alternating current stimulation (tACS) to the primary motor cortex (M1) at different frequencies during an index–thumb pinch-grip observation task. To estimate changes in the corticospinal output, we used the size of motor evoked potentials (MEPs) obtained by transcranial magnetic stimulation (TMS) of M1 using an online MRI-guided simultaneous TMS-tACS approach. The results of the beta-tACS confirm a non-selective increase in corticospinal excitability in subjects at rest; an increase was observed for both of the tested hand muscles, the first dorsal interosseous (FDI) and the abductor digiti minimi (ADM). However, during action observation of the pinch-grip movement, the increase of corticospinal excitability was only observed for the prime mover FDI muscle and took place during alpha-tACS, while gamma-tACS affected both the FDI and control muscle (ADM) responses. These phenomena likely reflect the hypothesis that the mu and gamma rhythms specifically index the downstream modulation of primary sensorimotor areas by engaging mirror neuron activity. The current neuromodulation approach confirms that tACS can be used to induce neurophysiologically detectable state-dependent enhancement effects, even in complex motor-cognitive tasks. © 2019, The Author(s)
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
State-dependent effects of transcranial oscillatory currents on the motor system: what you think matters
Get PDFImperceptible transcranial alternating current stimulation (tACS) changes the endogenous cortical oscillatory activity in a frequency-specific manner. In the human motor system, tACS coincident with the idling beta rhythm of the quiescent motor cortex increased the corticospinal output. We reasoned that changing the initial state of the brain (i.e., from quiescence to a motor imagery task that desynchronizes the local beta rhythm) might also change the susceptibility of the corticospinal system to resonance effects induced by beta-tACS. We tested this hypothesis by delivering tACS at different frequencies (theta, alpha, beta, and gamma) on the primary motor cortex at rest and during motor imagery. Motor-evoked potentials (MEPs) were obtained by transcranial magnetic stimulation (TMS) on the primary motor cortex with an online-navigated TMS-tACS setting. During motor imagery, the increase of corticospinal excitability was maximal with theta-tACS, likely reflecting a reinforcement of working memory processes required to mentally process and "execute" the cognitive task. As expected, the maximal MEPs increase with subjects at rest was instead obtained with beta-tACS, substantiating previous evidence. This dissociation provides new evidence of state and frequency dependency of tACS effects on the motor system and helps discern the functional role of different oscillatory frequencies of this brain region. These findings may be relevant for rehabilitative neuromodulatory interventions
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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