scholarly journals Modulation of Rapid Visual Responses during Reaching by Multimodal Stimuli

2019 ◽  
Author(s):  
Isabel S Glover ◽  
Stuart N Baker
Keyword(s):  
Median Nerve ◽  
Reticular Formation ◽  
Visual Target ◽  
Human Subjects ◽  
Vestibular Stimulation ◽  
Auditory Stimuli ◽  
Visual Responses ◽  
Healthy Human ◽  
Reaching Task ◽  
Upper Limb Function

AbstractThe reticulospinal tract plays an important role in primate upper limb function, but methods for assessing its activity are limited. One promising approach is to measure rapid visual responses (RVRs) in arm muscle activity during a visually-cued reaching task; these may arise from a tecto-reticulospinal pathway. We investigated whether changes in reticulospinal excitability can be assessed non-invasively using RVRs, by pairing the visual stimuli of the reaching task with electrical stimulation of the median nerve, galvanic vestibular stimulation or loud sounds, all of which are known to activate the reticular formation.Surface electromyogram recordings were made from the right deltoid of healthy human subjects as they performed fast reaching movements towards visual targets. Stimuli were delivered up to 200ms before target appearance and RVR was quantified as the EMG amplitude in a window 75-125ms after visual target onset. Median nerve, vestibular and auditory stimuli all consistently facilitated the RVRs, as well as reducing the latency of responses. We propose that this reflects modulation of tecto-reticulospinal excitability, suggesting that the amplitude of RVRs can be used to assess changes in brainstem excitability non-invasively in humans.New & NoteworthyShort latency responses in arm muscles evoked during a visually-driven reaching task have previously been proposed to be tecto-reticulospinal in origin. We demonstrate that these responses can be facilitated by pairing the appearance of a visual target with stimuli that activate the reticular formation – median nerve, vestibular and auditory stimuli. We propose that this reflects non-invasive measurement and modulation of reticulospinal excitability.

scholarly journals Multimodal stimuli modulate rapid visual responses during reaching

2019 ◽  
Vol 122 (5) ◽  
pp. 1894-1908 ◽  
Author(s):  
Isabel S. Glover ◽  
Stuart N. Baker
Keyword(s):  
Median Nerve ◽  
Reticular Formation ◽  
Visual Target ◽  
Human Subjects ◽  
Vestibular Stimulation ◽  
Auditory Stimuli ◽  
Visual Responses ◽  
Healthy Human ◽  
Reaching Task ◽  
Upper Limb Function

The reticulospinal tract plays an important role in primate upper limb function, but methods for assessing its activity are limited. One promising approach is to measure rapid visual responses (RVRs) in arm muscle activity during a visually cued reaching task; these may arise from a tecto-reticulospinal pathway. We investigated whether changes in reticulospinal excitability can be assessed noninvasively using RVRs, by pairing the visual stimuli of the reaching task with electrical stimulation of the median nerve, galvanic vestibular stimulation, or loud sounds, all of which are known to activate the reticular formation. Surface electromyogram (EMG) recordings were made from the right deltoid of healthy human subjects as they performed fast reaching movements toward visual targets. Stimuli were delivered up to 200 ms before target appearance, and RVR was quantified as the EMG amplitude in a window 75–125 ms after visual target onset. Median nerve, vestibular, and auditory stimuli all consistently facilitated the RVRs, as well as reducing the latency of responses. We propose that this facilitation reflects modulation of tecto-reticulospinal excitability, which is consistent with the idea that the amplitude of RVRs can be used to assess changes in brain stem excitability noninvasively in humans. NEW & NOTEWORTHY Short-latency responses in arm muscles evoked during a visually driven reaching task have previously been proposed to be tecto-reticulospinal in origin. We demonstrate that these responses can be facilitated by pairing the appearance of a visual target with stimuli that activate the reticular formation: median nerve, vestibular, and auditory stimuli. We propose that this reflects noninvasive measurement and modulation of reticulospinal excitability.

scholarly journals Three-Dimensional Binocular Kinematics of Torsional Vestibular Nystagmus During Convergence on Head-Fixed Targets in Humans

2001 ◽  
Vol 86 (1) ◽  
pp. 113-122 ◽  
Author(s):  
O. Bergamin ◽  
D. Straumann
Keyword(s):  
Human Subjects ◽  
Three Dimensional ◽  
Vertical Component ◽  
Vestibular Stimulation ◽  
Fixed Target ◽  
Healthy Human ◽  
Retinal Slip ◽  
Gain Reduction ◽  
The Right ◽  
Eye Velocity

When a human subject is oscillated about the nasooccipital axis and fixes upon targets along the horizontal head-fixed meridian, angular eye velocity includes a vertical component that increases with the horizontal eccentricity of the line-of-sight. This vertical eye movement component is necessary to prevent retinal slip. We asked whether fixation on a near head-fixed target during the same torsional vestibular stimulation would lead to differences of vertical eye movements between the right and the left eye, as the directions of the two lines-of-sight are not parallel during convergence. Healthy human subjects ( n = 6) were oscillated (0.3 Hz, ±30°) about the nasooccipital axis on a three-dimensional motor-driven turntable. Binocular movements were recorded using the dual search coil technique. A head-fixed laser dot was presented 1.4 m (far head-fixed target) or 0.25 m (near head-fixed target) in front of the right eye. We found highly significant ( P < 0.01) correlations (R binocular = 0.8, monocular = 0.59) between the convergence angle and the difference of the vertical eye velocity between the two eyes. The slope of the fitted linear regression between the two parameters ( s = 0.45) was close to the theoretical slope necessary to prevent vertical retinal slippage (predicted s = 0.5). Covering the left eye did not significantly change the slope ( s = 0.52). In addition, there was a marked gain reduction (∼35%) of the torsional vestibuloocular reflex (VOR) between viewing the far and the near targets, confirming earlier results by others. There was no difference in torsional gain reduction between the two eyes. Lenses of +3 dpt positioned in front of both eyes to decrease the amount of accommodation did not further change the gain of the torsional VOR. In conclusion, ocular convergence on a near head-fixed target during torsional vestibular stimulation leads to deviations in vertical angular velocity between the two eyes necessary to prevent vertical double vision. The vertical deviation velocity is mainly linked to the amount of convergence, since it also occurs during monocular viewing of the near head-fixed target. This suggests that convergence during vestibular stimulation automatically leads to an alignment of binocular rotation axes with the visual axes independent of retinal slip.

scholarly journals A Re-evaluation of Whether Non-monosynaptic Homonymous H Reflex Facilitation Tests Propriospinal Circuits

2021 ◽  
Vol 15 ◽  
Author(s):  
Karen M. Fisher ◽  
Stuart N. Baker
Keyword(s):  
Median Nerve ◽  
Human Subjects ◽  
Conditioning Stimulus ◽  
Macaque Monkey ◽  
H Reflex ◽  
Healthy Human ◽  
Median Nerve Stimulation ◽  
Important Pathway ◽  
Peripheral Axon ◽  
Forearm Flexor

The C3–C4 propriospinal system is an important pathway mediating movement in cats; it contributes to movements in primates (including humans), and may have a role in recovery after lesion. Validated clinical tests of this system would find many applications, therefore we sought to test whether non-monosynaptic homonymous facilitation of the forearm flexor H reflex is mediated solely via a C3–C4 propriospinal pathway. In one anesthetized macaque monkey, median nerve stimulation elicited an H reflex in the flexor carpi radialis (FCR). Median nerve conditioning stimuli at sub-threshold intensities facilitated the H reflex, for inter-stimulus intervals up to 30 ms. Successive spinal surgical hemisections were then made. C2 lesion left the homonymous facilitation intact, suggesting mediation by spinal, not supraspinal pathways. Facilitation also remained after a second lesion at C5, indicating a major role for segmental (C7–C8) rather than propriospinal (C3–C4) interneurons. In separate experiments in five healthy human subjects, a threshold tracking approach assessed changes in peripheral axon excitability after conditioning stimulation. This was found to be enhanced up to 20 ms after the conditioning stimulus, and could partly, although not completely, underlie the H reflex facilitation seen. We conclude that homonymous facilitation of the H reflex in FCR can be produced by segmental spinal mechanisms, as well as by a supranormal period of nerve excitability. Unfortunately, this straightforward test cannot therefore be used for selective assessment of propriospinal circuits.

Minimizing Carry-Over Effects After Treatment Failure and Maximizing Therapeutic Outcome

2014 ◽  
Vol 222 (3) ◽  
pp. 171-178 ◽  
Author(s):  
Mareile Hofmann ◽  
Nathalie Wrobel ◽  
Simon Kessner ◽  
Ulrike Bingel
Keyword(s):  
Treatment Failure ◽  
Human Subjects ◽  
Subsequent Treatment ◽  
Clinical Samples ◽  
Administration Route ◽  
Healthy Human ◽  
Negative Experiences ◽  
Analgesic Treatment ◽  
Balanced Design ◽  
Carry Over

According to experimental and clinical evidence, the experiences of previous treatments are carried over to different therapeutic approaches and impair the outcome of subsequent treatments. In this behavioral pilot study we used a change in administration route to investigate whether the effect of prior treatment experience on a subsequent treatment depends on the similarity of both treatments. We experimentally induced positive or negative experiences with a topical analgesic treatment in two groups of healthy human subjects. Subsequently, we compared responses to a second, unrelated and systemic analgesic treatment between both the positive and negative group. We found that there was no difference in the analgesic response to the second treatment between the two groups. Our data indicate that a change in administration route might reduce the influence of treatment history and therefore be a way to reduce negative carry-over effects after treatment failure. Future studies will have to validate these findings in a fully balanced design including larger, clinical samples.

Detection of Soluble Fibrin Monomer Complexes in Blood by Means of Protamine Sulphate Test

1968 ◽  
Vol 20 (01/02) ◽  
pp. 044-049 ◽  
Author(s):  
B Lipiński ◽  
K Worowski
Keyword(s):  
Human Subjects ◽  
Coronary Thrombosis ◽  
Mean Value ◽  
Healthy Human ◽  
Protamine Sulphate ◽  
Soluble Fibrin ◽  
Fibrin Monomer ◽  
Dog Plasma ◽  
The Mean ◽  
Precipitable Protein

SummaryIn the present paper described is a simple test for detecting soluble fibrin monomer complexes (SFMC) in blood. The test consists in mixing 1% protamine sulphate with diluted oxalated plasma or serum and reading the optical density at 6190 Å. In experiments with dog plasma, enriched with soluble fibrin complexes, it was shown that OD read in PS test is proportional to the amount of fibrin recovered from the precipitate. It was found that SFMC level in plasma increases in rabbits infused intravenously with thrombin and decreases after injection of plasmin with streptokinase. In both cases PS precipitable protein in serum is elevated indicating enhanced fibrinolysis. In healthy human subjects the mean value of OD readings in plasma and sera were found to be 0.30 and 0.11, while in patients with coronary thrombosis they are 0.64 and 0.05 respectively. The origin of SFMC in circulation under physiological and pathological conditions is discussed.

Chronic stress decreases circulating endocannabinoid 2-arachidonoylglycerol in healthy human subjects

2015 ◽  
Author(s):  
Buqing Yi ◽  
Igor Nichiporuk ◽  
Matthias Feuerecker ◽  
Gustav Schelling ◽  
Alexander Chouker
Keyword(s):  
Chronic Stress ◽  
Human Subjects ◽  
Healthy Human ◽  
Healthy Human Subjects

scholarly journals Acacia Gum Is Well Tolerated While Increasing Satiety and Lowering Peak Blood Glucose Response in Healthy Human Subjects

Nutrients ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 618
Author(s):  
Riley Larson ◽  
Courtney Nelson ◽  
Renee Korczak ◽  
Holly Willis ◽  
Jennifer Erickson ◽  
...  
Keyword(s):  
Blood Glucose ◽  
Human Subjects ◽  
Area Under The Curve ◽  
Soluble Fiber ◽  
Healthy Human ◽  
Glucose Response ◽  
Blood Glucose Response ◽  
Acacia Gum ◽  
Fiber Treatment ◽  
Healthy Human Subjects

Acacia gum (AG) is a non-viscous soluble fiber that is easily incorporated into beverages and foods. To determine its physiological effects in healthy human subjects, we fed 0, 20, and 40 g of acacia gum in orange juice along with a bagel and cream cheese after a 12 h fast and compared satiety, glycemic response, gastrointestinal tolerance, and food intake among treatments. Subjects (n = 48) reported less hunger and greater fullness at 15 min (p = 0.019 and 0.003, respectively) and 240 min (p = 0.036 and 0.05, respectively) after breakfast with the 40 g fiber treatment. They also reported being more satisfied at 15 min (p = 0.011) and less hungry with the 40 g fiber treatment at 30 min (p = 0.012). Subjects reported more bloating, flatulence, and GI rumbling on the 40 g fiber treatment compared to control, although values for GI tolerance were all low with AG treatment. No significant differences were found in area under the curve (AUC) or change from baseline for blood glucose response, although actual blood glucose with 20 g fiber at 30 min was significantly less than control. Individuals varied greatly in their postprandial glucose response to all treatments. AG improves satiety response and may lower peak glucose response at certain timepoints, and it is well tolerated in healthy human subjects. AG can be added to beverages and foods in doses that can help meet fiber recommendations.

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