| 1. |
- Torbert, R. B., et al.
(författare)
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Electron-scale dynamics of the diffusion region during symmetric magnetic reconnection in space
- 2018
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Ingår i: Science. - : AMER ASSOC ADVANCEMENT SCIENCE. - 0036-8075 .- 1095-9203. ; 362:6421, s. 1391-1395
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Tidskriftsartikel (refereegranskat)abstract
- Magnetic reconnection is an energy conversion process that occurs in many astrophysical contexts including Earth's magnetosphere, where the process can be investigated in situ by spacecraft. On 11 July 2017, the four Magnetospheric Multiscale spacecraft encountered a reconnection site in Earth's magnetotail, where reconnection involves symmetric inflow conditions. The electron-scale plasma measurements revealed (i) super-Alfvenic electron jets reaching 15,000 kilometers per second; (ii) electron meandering motion and acceleration by the electric field, producing multiple crescent-shaped structures in the velocity distributions; and (iii) the spatial dimensions of the electron diffusion region with an aspect ratio of 0.1 to 0.2, consistent with fast reconnection. The well-structured multiple layers of electron populations indicate that the dominant electron dynamics are mostly laminar, despite the presence of turbulence near the reconnection site.
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| 2. |
- Abrahamsson, Per-Anders, et al.
(författare)
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Calcitonin and calcitonin gene-related peptide in the human prostate gland
- 2000
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Ingår i: The Prostate. - 0270-4137. ; 44:3, s. 181-186
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Calcitonin-related peptides have been found in the human prostate, and calcitonin (CT) and calcitonin gene-related peptide (CGRP) have been demonstrated in subpopulations of neuroendocrine (NE) cells. The purpose of this study was to determine the concentrations of CT and CGRP as well as the densities of NE cells in normal prostates, benign prostatic hyperplasia (BPH), and carcinoma of the prostate (CAP). METHODS: In 42 specimens of radical prostatectomy, the number of CT- and CGRP-immunoreactive NE cells in areas of normal and BPH tissue was determined, and compared with CAP tissue using immunocytochemistry. In addition, by radioimmunoassay (RIA), tissue levels of CT and CGRP were analyzed in extracts from areas of normal, BPH, and CAP tissue, as verified by adjacent histologic sections. RESULTS: A significant decrease in CT-immunoreactive NE cells was observed in hyperplastic nodules of BPH in comparison to normal tissue. These findings were in parallel with a significant reduction in tissue CT level in BPH compared to normal tissue. There was also a marked, but statistically nonsignificant, reduction in CT levels in CAP tissue. In contrast, levels of CGRP in BPH and CAP tissue did not show any significant differences compared to normal tissue. CONCLUSIONS: CT and CGRP are present in NE cells of the human prostate. Calcitonin levels are significantly reduced in BPH, in parallel with a decreased number of CT-immunoreactive NE cells, whereas no significant changes in tissue levels of CGRP were observed. The functional significance of these findings is discussed.
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| 3. |
- Farrugia, C. J., et al.
(författare)
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Effects in the Near-Magnetopause Magnetosheath Elicited by Large-Amplitube Alfvenic Fluctuations Terminating in a Field and Flow Discontinuity
- 2018
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Ingår i: Journal of Geophysical Research - Space Physics. - : AMER GEOPHYSICAL UNION. - 2169-9380 .- 2169-9402. ; 123:11, s. 8983-9004
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we report on a sequence of large-amplitude Alfvenic fluctuations terminating in a field and flow discontinuity and their effects on electromagnetic fields and plasmas in the near-magnetopause magnetosheath. An arc-polarized structure in the magnetic field was observed by the Time History of Events and Macroscale Interactions during Substorms-C in the solar wind, indicative of nonlinear Alfven waves. It ends with a combined tangential discontinuity/vortex sheet, which is strongly inclined to the ecliptic plane and at which there is a sharp rise in the density and a drop in temperature. Several effects resulting from this structure were observed by the Magnetospheric Multiscale spacecraft in the magnetosheath close to the subsolar point (11:30 magnetic local time) and somewhat south of the geomagnetic equator (-33 degrees magnetic latitude): (i) kinetic Alfven waves; (ii) a peaking of the electric and magnetic field strengths where E . J becomes strong and negative (-1 nW/m(3)) just prior to an abrupt dropout of the fields; (iii) evolution in the pitch angle distribution of energetic (a few tens of kilo-electron-volts) ions (H+, Hen+, and On+) and electrons inside a high-density region, which we attribute to gyrosounding of the tangential discontinuity/vortex sheet structure passing by the spacecraft; (iv) field-aligned acceleration of ions and electrons that could be associated with localized magnetosheath reconnection inside the high-density region; and (v) variable and strong flow changes, which we argue to be unrelated to reconnection at partial magnetopause crossings and likely result from deflections of magnetosheath flow by a locally deformed, oscillating magnetopause.
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| 4. |
- Pasculli, Giuseppe, et al.
(författare)
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Psychedelics in developmental stuttering to modulate brain functioning : a new therapeutic perspective?
- 2024
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Ingår i: Frontiers in Human Neuroscience. - : Frontiers Media S.A.. - 1662-5161. ; 18
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Tidskriftsartikel (refereegranskat)abstract
- Developmental stuttering (DS) is a neurodevelopmental speech-motor disorder characterized by symptoms such as blocks, repetitions, and prolongations. Persistent DS often has a significant negative impact on quality of life, and interventions for it have limited efficacy. Herein, we briefly review existing research on the neurophysiological underpinnings of DS -specifically, brain metabolic and default mode/social-cognitive networks (DMN/SCN) anomalies- arguing that psychedelic compounds might be considered and investigated (e.g., in randomized clinical trials) for treatment of DS. The neural background of DS is likely to be heterogeneous, and some contribution from genetically determinants of metabolic deficiencies in the basal ganglia and speech-motor cortical regions are thought to play a role in appearance of DS symptoms, which possibly results in a cascade of events contributing to impairments in speech-motor execution. In persistent DS, the difficulties of speech are often linked to a series of associated aspects such as social anxiety and social avoidance. In this context, the SCN and DMN (also influencing a series of fronto-parietal, somato-motor, and attentional networks) may have a role in worsening dysfluencies. Interestingly, brain metabolism and SCN/DMN connectivity can be modified by psychedelics, which have been shown to improve clinical evidence of some psychiatric conditions (e.g., depression, post-traumatic stress disorder, etc.) associated with psychological constructs such as rumination and social anxiety, which also tend to be present in persistent DS. To date, while there have been no controlled trials on the effects of psychedelics in DS, anecdotal evidence suggests that these agents may have beneficial effects on stuttering and its associated characteristics. We suggest that psychedelics warrant investigation in DS.
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| 5. |
- Alm, Per A
(författare)
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Copper in developmental stuttering.
- 2005
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Ingår i: Folia Phoniatrica et Logopaedica. - : S. Karger AG. - 1021-7762 .- 1421-9972. ; 57:4, s. 216-222
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Tidskriftsartikel (refereegranskat)abstract
- It has previously been reported that men with developmental stuttering showed reduced concentration of copper in the blood, and a negative correlation between the copper level and the severity of stuttering. Disorders of copper metabolism may result in dysfunction of the basal ganglia system and dystonia, a motor disorder sharing some traits of stuttering. It has been shown that copper ions affect the dopamine and the GABA systems. With this background we investigated the plasma level of copper, the copper binding protein ceruloplasmin, and the estimated level of free copper in stuttering adults. Sixteen men with developmental stuttering were compared with 16 men without speech problems. The samples were assayed in one batch in a pseudorandom and counterbalanced order. No significant differences were found between stuttering men and the control group in any of the biological variables, and no negative correlation between copper and the general severity of stuttering was shown. On the contrary, an explorative analysis resulted in a positive correlation between high plasma copper and superfluous muscular activity during stuttering (r = 0.51, p = 0.04). This result indicates that there is no relation between developmental stuttering and low plasma copper in the main population of stuttering adults.
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| 6. |
- Alm, Per A., et al.
(författare)
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Hemispheric Lateralization of Motor Thresholds in Relation to Stuttering
- 2013
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 8:10, s. e76824-
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Tidskriftsartikel (refereegranskat)abstract
- Stuttering is a complex speech disorder. Previous studies indicate a tendency towards elevated motor threshold for the left hemisphere, as measured using transcranial magnetic stimulation (TMS). This may reflect a monohemispheric motor system impairment. The purpose of the study was to investigate the relative side-to-side difference (asymmetry) and the absolute levels of motor threshold for the hand area, using TMS in adults who stutter (n = 15) and in controls (n = 15). In accordance with the hypothesis, the groups differed significantly regarding the relative side-to-side difference of finger motor threshold (p = 0.0026), with the stuttering group showing higher motor threshold of the left hemisphere in relation to the right. Also the absolute level of the finger motor threshold for the left hemisphere differed between the groups (p = 0.049). The obtained results, together with previous investigations, provide support for the hypothesis that stuttering tends to be related to left hemisphere motor impairment, and possibly to a dysfunctional state of bilateral speech motor control.
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| 7. |
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| 8. |
- Alm, Per A, 1963-, et al.
(författare)
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Neuropathic pain: transcranial electric motor cortex stimulation using high frequency random noise : Case report of a novel treatment
- 2013
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Ingår i: Journal of Pain Research. - 1178-7090. ; 6, s. 479-486
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES: Electric motor cortex stimulation has been reported to be effective for many cases of neuropathic pain, in the form of epidural stimulation or transcranial direct current stimulation (tDCS). A novel technique is transcranial random noise stimulation (tRNS), which increases the cortical excitability irrespective of the orientation of the current. The aim of this study was to investigate the effect of tRNS on neuropathic pain in a small number of subjects, and in a case study explore the effects of different stimulation parameters and the long-term stability of treatment effects.METHODS: THE STUDY WAS DIVIDED INTO THREE PHASES: (1) a double-blind crossover study, with four subjects; (2) a double-blind extended case study with one responder; and (3) open continued treatment. The motor cortex stimulation consisted of alternating current random noise (100-600 Hz), varying from 0.5 to 10 minutes and from 50 to 1500 μA, at intervals ranging from daily to fortnightly.RESULTS: One out of four participants showed a strong positive effect (also compared with direct-current-sham, P = 0.006). Unexpectedly, this effect was shown to occur also for very weak (100 μA, P = 0.048) and brief (0.5 minutes, P = 0.028) stimulation. The effect was largest during the first month, but remained at a highly motivating level for the patient after 6 months.DISCUSSION: The study suggests that tRNS may be an effective treatment for some cases of neuropathic pain. An important result was the indication that even low levels of stimulation may have substantial effects.
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| 9. |
- Alm, Per A
(författare)
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On the Causal Mechanisms of Stuttering
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Stuttering is one of the most common speech disorders. However, the etiology is poorly understood, and is likely to be heterogeneous. The aim of this thesis was to clarify causal mechanisms, focusing the brain. The project included theoretical development based on published data, and a broad approach of explorative studies and testing of hypotheses. The theoretical work focused the basal ganglia, leading to a model based on the dual premotor systems hypothesis (G. Goldberg, 1985, 1991), which defines two parallel premotor systems: the medial (the basal ganglia and the SMA), and the lateral (the lateral premotor cortex and the cerebellum). Stuttering is suggested to be caused by a disturbance of the medial system, in most cases in the basal ganglia. The core dysfunction is proposed to be impaired "go-signals" from the medial system, supposed to trigger the next motor segment in speech. According to this model, under some conditions speech control is shifted from the medial to the lateral system, thereby bypassing the dysfunction and resulting in fluent speech. The lateral system is suggested to be active when speech is combined with sensory input, like chorus speech or metronome. Also the effect of altered auditory feedback in reducing stuttering is proposed to be based on this mechanism. It seems as the lateral system is able control speech timing without sensory input, but that this demands increased attention to some particular aspect of speech, as occurs in imitation of dialects, exaggerated rhythm, reduced speech rate, or role play. Also singing is suggested to be based on the lateral system. Superfluous muscular activation accompanying stuttering may be a type of dystonia: involuntary contractions related to the basal ganglia disturbance. The high prevalence of stuttering at age 2.5 to 3 years is proposed to reflect a normally occurring peak in the number of dopamine receptors at this age. A total of 35 stuttering adults participated. Two studies, of copper metabolism and "startle prepulse inhibition", did not indicate any significant differences in comparison with matched controls. It has previously been reported that stuttering may be associated with increased neuromuscular reactivity, measured as exaggerated eye-blink in response to noise. This aspect was investigated. The stuttering group showed somewhat stronger eye-blink, though not statistically significant. Strong eye-blink was not related to anxiety, but was clearly related to low calcium, which is known to increase the excitability of the nervous system. The stuttering group showed somewhat lower calcium, and a weak tendency towards more severe stuttering in case of low calcium. It is possible that low calcium can increase the severity of stuttering in some cases. A subgroup reported some traits of childhood ADHD, and this group typically also reported neurological incidents before the onset of stuttering. The subgroup without traits of ADHD typically reported having stuttering relatives but no neurological incident.
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| 10. |
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