1,720,993 research outputs found
Short and middle-latency Median Nerve (MN) SEPs recorded by depth electrodes in human pre-SMA and SMA-proper
No full textOBJECTIVE: To analyse waveforms, latencies and amplitudes of Median Nerve (MN) SEPs recorded by stereotactically electrodes implanted in the SMA of 14 epileptic patients (9 in pre-SMA,3 in SMA-proper, 2 in both) in order to evaluate which short and middle-latency SEPs are generated in this area and which could be the physiological relevance of these responses. METHODS: Short and middle-latency MN SEPs were recorded by chronically implanted electrodes in the fronto-temporal cortex and in particular in the mesial frontal region of 14 drug-resistant epileptic patients. MN stimulations of 100 micros were delivered by skin electrodes at the wrist; stimulus intensity was adjusted slightly above the motor threshold. RESULTS: The main result of this study is that middle-latency SEPs were originated in pre-SMA but not in SMA-proper as demonstrated by both referential and bipolar recordings. In particular off-line computed bipolar traces between neighbouring contacts implanted in the pre-SMA and in the frontal external regions showed a phase reversal at the deepest contacts located in pre-SMA. Conversely, bipolar recordings between neighbouring contacts implanted in the SMA-proper and in the frontal external regions showed inversion recovery at more superficial contacts, implanted in area 6. Finally, we confirmed that no short-latency MN SEP (and in particular the N30) is originated in the whole SMA. CONCLUSIONS: Among premotor areas, somatosensory inputs seem to reach pre-SMA and area 6 but not SMA-proper. SIGNIFICANCE: This study assessed that no scalp SEP in the first 100 ms after MN stimulus could be generated in SMA-proper
THE PROGNOSTIC VALUE OF EVOKED RESPONSES FROM PRIMARY SOMATOSENSORY AND AUDITORY CORTEX IN COMATOSE PATIENTS
No full textSomatosensory evoked potentials after multisegmental upper limb stimulation in diagnosis of cervical spondylotic myelopathy
No full textRadial, median, and ulnar nerve somatosensory evoked potentials (SEPs) were recorded, with non-cephalic reference montage, in 38 patients with clinical signs of cervical myelopathy and MRI evidence of spondylotic compression of the cervical cord. Upper Limb SEPs are useful in spondylotic myelopathy because SEPs were abnormal in all patients for at least one of the stimulated nerves and SEP abnormalities were bilateral in all patients but one. Reduction of the amplitude of the N13 potential indicating a segmental dysfunction of the cervical cord was the most frequent abnormality; it occurred in 93.4%, 84.2%, and 64.5% of radial, median, and ulnar nerve SEPs respectively. A second finding was that the P14 far-field potential was more sensitive than the cortical N20 potential to slowing of conduction in the dorsal column fibres. The high percentage of N13 abnormalities in the radial and median rather than in the ulnar nerve SEPs correlated well with the radiological compression level, mainly involving the C5-C6 vertebral segments. Therefore the recording of the N13 response is a reliable diagnostic tool in patients with cervical spondylotic myelopathy and P14 abnormalities, though less frequent, can be useful in assessing subclinical dorsal column dysfunction
Giant central N20-P22 with normal area 3b N20-P20: An argument in favour of an area 3a generator of early median nerve cortical SEPs?
No full textSomatosensory disinhibition in dystonia
No full textDespite the fact that somatosensory processing is inherently dependent on inhibitory functions, only excitatory aspects of the somatosensory feedback have so far been assessed in dystonic patients. We studied the recovery functions of spinal N13, brainstem P14, parietal N20, P27, and frontal N30 somatosensory evoked potentials (SEPS) after paired median nerve stimulation in 10 patients with dystonia and in 10 normal subjects. The recovery functions were assessed (conditioning stimulus: S1; test stimulus: S2) at interstimuls intervals (ISIs) of 5, 20, and 40 ms. SEPs evoked by S2 were calculated by subtracting the SEPs of the S1 only response from the SEPs of the response to the paired stimuli (S1 + S2), and their amplitudes were compared with those of the control response (S1) at each ISI considered. This ratio, (S2/S1)*100, investigates changes in the excitability of the somatosensory system. No significant difference was found in SEP amplitudes for single stimulus (S1) between dystonic patients and normal subjects. The (S2/S1)*100 ratio at the ISI of 5 ms did not significantly differ between dystonic patients and normal subjects, but at ISIS of 20 and 40 ms, this ratio was significantly higher in patients than in normals for spinal N13 and cortical N20, P27, N30 SEPs
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
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
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
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