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Jaw-opening reflex after CO2 laser stimulation of the perioral region in man.
No full textCO2 laser pulses selectively excite A-delta and C mechano-thermal nociceptors in the superficial layers of the skin. To study the jaw-opening reflex elicited by a purely nociceptive input, we delivered laser pulses to the perioral region in 15 subjects. Sensory threshold was very low (9 mJ/mm2). High-intensity noxious laser pulses (more than 4 x sensory threshold) evoked a single phase of electromyogram suppression (laser silent period, LSP) at an onset latency of 70 ms in the contracted masseter and temporal muscles, bilaterally. Even maximum-intensity laser pulses failed to activate the suprahyoid muscles. The recovery curves to paired laser stimuli showed that at short interstimulus intervals the test LSP was strongly suppressed. At about 380 ms it recovered to 50\%, i.e. its recovery curve resembled that of the masseter late silent period after electrical mental nerve stimulation (SP2). In experiments studying the interaction with heterotopic stimuli and non-nociceptive responses, chin-taps or electrical shocks delivered to the supraorbital, infraorbital or mental nerves before laser stimulation strongly suppressed the LSP. A preceding perioral laser pulse strongly suppressed the masseter SP evoked by supraorbital stimulation and the SP2 evoked by mental stimulation, but left SPI unaffected. We conclude that the perioral A-delta fibre input elicits a jaw-opening reflex simply by inhibiting the jaw-closers. The LSP response is mediated by a multisynaptic chain of brainstem interneurons and shares with the masseter SP2 part of the central circuit in the ponto-medullary region. We also propose that a common centre processes the various inputs for jaw opening
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
Excitability of the central masticatory pathways in patients with painful temporomandibular disorders
No full textMuch is unclear about the pathophysiological mechanisms underlying painful temporomandibular disorders. In addition to various other theories, masticatory muscle dysfunction and pain have also been attributed to primary central nervous system hyperactivity. We assessed this possibility in a study using recent neurophysiological techniques. From among outpatients whose diagnosis of temporomandibular disorders had been obtained in stomatognathic facilities, we studied 10 patients with bilateral pain and 15 patients with unilateral pain, in whom electromyographic examination of the trigeminal reflexes disclosed normal findings except for absence or amplitude asymmetry of the jaw jerk. Transcranial magnetic stimulation yielded masseter motor evoked potentials of normal latency and amplitude, but five patients had to exert a near-maximum contraction to obtain their responses. The masseter silent periods elicited by the double-shock technique recovered normally. Because these tests measure the excitability of the masticatory system (including motor cortex, corticobulbar and corticoreticular connections, reticular interneurones and lower motoneurones), the lack of facilitation in these patients' responses excluded central hyperactivity as the primary cause of their masticatory dysfunction and pain. (C) 1997 International Association for the Study of Pain. Published by Elsevier Science B.V
In systemic sclerosis patients, Bosentan is safe and effective for digital ulcer prevention and it seems to attenuate the development of pulmonary arterial hypertension
No full text[No abstract available
Studio osservazionale su pazienti di entrambi i sessi con IMA con ST sopraslivellato: considerazioni sulla sede ECG-grafica d’esordio
No full textPostherpetic neuralgia in a patient with a lesion involving the dorsal horn of the cervical spinal cord.
No full textCortical mechanisms mediating the inhibitory period after magnetic stimulation of the facial motor area.
No full textWe studied the silent period (SP) that interrupts voluntary electromyographic activity (EMG) in facial muscles, after transcranial magnetic stimulation (TMS), in normal subjects. High-intensity magnetic stimulation with a 12-cm round coil centered at the vertex induced a long-lasting SP (215 ms), whereas supramaximal stimulation of the facial nerve only induced a short (< 20 ms) and incomplete EMG suppression, and cutaneous stimuli had no inhibitory effect at all. Cutaneous trigeminal stimulation delivered after TMS evoked blink-like reflexes, showing that facial motoneurons were not inhibited during the SP. Simultaneous recordings from perioral muscles (large cortical representation) and from orbicularis oculi and masseter muscles (small cortical representation) showed SPs of identical duration. Focal stimuli with a figure-of-eight coil showed that positioning of the coil was critical and that the optimal scalp sites for evoking the largest motor potentials and longest SPs coincided. Low-intensity stimulation occasionally elicited short SPs without a preceding motor potential. We conclude that the SP induced in facial muscles by TMS results from the excitation of cortical inhibitory interneurons surrounding the upper motoneurons
Trigeminal responses to laser stimuli.
No full textThe majority of the studies on laser evoked potentials (LEPs) have been focused on hand and foot stimulations and only lately on the trigeminal system. Because of a high receptor density in the facial skin and the very short conduction distance, LEP recordings after trigeminal stimulation are easier and quicker than those after stimulation of the limb extremities. Laser pulses with a stimulus intensity close to perception threshold can evoke well-defined LEPs. Few trials are sufficient to yield stable and reproducible averages. Even ultralate LEPs related to the C-fibre input are comparatively easily obtained from the trigeminal territory. The brain generators of the main LEP waves are probably very close for the trigeminal and limb stimulations. Trigeminal LEPs have been found absent or delayed in patients with trigeminal neuralgia, trigeminal neuropathies, posterior fossa tumors, and brainstem infarctions or demyelinating plaques. Conversely, trigeminal LEPs appear to be enhanced in patients with migraine. High-intensity pulses directed to any trigeminal division also elicit reflex responses: a blink-like reflex in the orbicularis oculi and a single silent period in the contracting masseter muscle. The availability of a neurophysiological method of assessing function of the trigeminal nociceptive pathways reaching both the cerebral cortex and the brainstem reflex circuits, has provided new opportunities for investigating the pathophysiology of orofacial pain syndromes
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
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