1,720,983 research outputs found
The role of the left inferior frontal gyrus in episodic encoding of faces: An interference study by repetitive transcranial magnetic stimulation
No full textDespite extensive research on face recognition, only a few studies have examined the integration of perceptual features with semantic, biographical, and episodic information. In order to address this issue, we used repetitive transcranial magnetic stimulation (rTMS) to target the left inferior frontal gyrus (IFG) and the left occipital face area (OFA) during a face recognition task. rTMS was delivered during the encoding of "context" faces (i.e., linked to an occupation, e.g., "lawyer") and "no-context" faces (i.e., linked to a nonword pattern, e.g., "xxxx"). Subjects were then asked to perform a recognition memory task. Accuracy at retrieval showed a mild decrease after left OFA stimulation, whereas rTMS over the left IFG drastically compromised memory performance selectively for no-context faces. On the other hand, absence of rTMS interference on context faces might be due either to the fact that pairing an occupation to a face makes the memory trace stronger, therefore less susceptible to rTMS interference, or to a different functional specificity of the left IFG subregions. © 2010 Psychology Press
Changes of motor cortical excitability in human subjects from wakefulness to early stages of sleep: a combined transcranial magnetic stimulation and electroencephalographic study.
No full textThe effect of sleep on human motor cortical excitability was investigated by evaluating the latency and amplitude of motor evoked potentials in ten subjects using transcranial magnetic stimulation. Motor evoked potentials and electroencephalographic data were recorded simultaneously and analyzed. Recordings were performed before, during and after a sleep period. A significant decrease in motor evoked potentials amplitude and a slight change in motor evoked potentials latency were noted in the recordings during the different sleep stages with a return to baseline values on awakening. A decrease in motor cortical excitability is suggested as explaining the effect of sleep
Modulation of cortical oscillatory activities induced by varying single-pulsetranscranial magnetic stimulation intensity over the left primary motor area: a combined EEG and TMS study.
No full textCombined transcranial magnetic stimulation/electroencephalography (TMS/EEG) was used to study the activation and interaction of cortical regions to a variety of focused sub- and suprathreshold magnetic pulses over the left primary motor cortex (M1) in ten healthy subjects. Five single-pulse TMS conditions were performed based on the individual resting motor threshold (RMT): (1) 80%; (2) 100%; (3) 120%; (4) 130%; and (5) sham. Simple self-paced movements of the right first finger were also executed. We evaluated the reactions to magnetic stimulation and movement conditions using event-related power and event-related coherence transformations of alpha and beta rhythms. Event-related power reflected regional oscillatory activity of neural assemblies, while event-related coherence reflected the inter-regional functional coupling of oscillatory neural activity. The event-related power transformation revealed that the magnetic pulse modulated cortical oscillations within the first half second for both frequency ranges. For the alpha rhythm, threshold TMS induced a small decrease in the amplitude of EEG oscillations over the stimulation site, while for both rhythms, a progressive synchronization was observed as the intensity of TMS was increased in both hemispheres. Movement onset produced a greater bilateral decrease of power compared with the effects of a magnetic pulse. The event-related coherence revealed that TMS enhanced the electrode connectivity of both hemispheres. Additionally, it was more enhanced within the first 500 ms following stimulation and was seen only for the alpha frequency rhythm. The increase of functional connectivity between cortical areas was minor for magnetic stimulation conditions compared with that for finger movements. The single-pulse TMS over M1 partially modulated the motor cortex generators of oscillatory activity, while a simple active self-paced movement of the right first finger induced greater cortex activation and coupling between cortical regions. We propose that finger movements impose higher functional demands on the motor system compared to artificial magnetic stimulation. These findings are consistent with the possibility that the human motor system may be based on network-like oscillatory cortical activity and might be modulated by brief electromagnetic sub- and suprathreshold pulses applied to M1, suggesting a phenomenon of resetting
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Long-lasting effects of high frequency repetitive transcranial magnetic stimulation in major depressed patients
No full textThe majority of previous clinical studies have indicated that repetitive transcranial magnetic stimulation (rTMS) may have antidepressant effects. Herein, we investigated the longitudinal, long-term antidepressant efficacy of daily left prefrontal cortex (PFC) rTMS for a 1-week period. Nineteen patients were randomly assigned to two treatment groups at 90% of individual motor threshold (MT): Twelve received active repetitive transcranial magnetic stimulation and seven received sham treatment. Each patient underwent five sessions of twenty 2-s trains of 20 Hz rTMS with 800 stimuli/day. The Beck Depression Inventory and the Hamilton Depression Rating Scale were used to assess severity of depression at 1, 4 and 12 weeks post-therapy. A significant reduction of baseline depression scores was observed after 1 week of active treatment that lasted for 1 month, indicating improvement of depressive symptoms. No significant effects were observed in patients receiving sham treatment. The results of this controlled study are in agreement with the findings of previous studies suggesting that daily left PFC rTMS has an antidepressant effect
Variations on the Author
Full text link“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
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe 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
Corticospinal excitability in human subjects during nonrapid eye movement sleep: Single and paired-pulse transcranial magnetic stimulation study
No full textThe mechanisms responsible for changes in brain function during normal sleep are poorly understood. In this study, we aimed to investigate the effects of sleep on human corticospinal excitability by estimating resting motor threshold (RMT), and latency and amplitude of motor-evoked potentials (MEPs) after delivering transcranial magnetic stimulation (TMS) in ten healthy subjects. We also aimed to study short-interval intracortical inhibition (SICI) during sleep with paired-pulse TMS (pp-TMS). Ten healthy volunteers were studied. They were monitored immediately before, during and after a 3-h sleep (from 1 p.m. to 4 p.m., immediately after the mid-day meal). EEG was continuously recorded during sleep and the various sleep stages were identified off line. Every 10 min, subjects received ten single stimuli (to estimate RMT, MEP latency and amplitude) and six paired stimuli (to estimate SICI). MEP amplitude decreased and latency and RMT increased during the various sleep stages and returned to baseline values on awakening. Post hoc comparisons showed a significant difference in pp-TMS MEP amplitudes between the sleep and all the other conditions. The changes in TMS evoked variables during the different sleep stages indicate that during nonrapid eye movement sleep, cortical pyramidal neuron excitability (as measured by RMT, MEP latency and amplitude) progressively diminishes and the efficiency of the intracortical GABA-ergic network (as assessed by three pp-TMS) increases. On awakening, these sleep-induced changes in corticospinal excitability return rapidly to values observed during wakefulness
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe 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
- …
