| 1. |
- Ackerley, Rochelle, 1980, et al.
(författare)
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Cutaneous warmth, but not touch, increases muscle sympathetic nerve activity during a muscle fatigue hand-grip task
- 2020
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Ingår i: Experimental Brain Research. - : Springer Science and Business Media LLC. - 0014-4819 .- 1432-1106. ; 238, s. 1035-1042
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Tidskriftsartikel (refereegranskat)abstract
- In homeostasis, somatosensory C fibre afferents are hypothesised to mediate input to the brain about interactions with external stimuli and sympathetic efference provides the output that regulates bodily functions. We aimed to test this hypothesis and whether different types of innocuous somatosensory input have differential effects. Healthy volunteers performed a muscle fatigue (hand-grip) task to exhaustion, which produces increased muscle sympathetic nerve activity (MSNA), as measured through microneurography. Participants completed the muscle fatigue task without concurrent cutaneous sensory stimulation (control) or we applied skin warming (heat pack) as a C fibre stimulation, slow brush stroking as C and A beta fibre stimulation, or vibration as A beta fibre stimulation, to the participant's forearm. We also measured heart rate, the duration of the hand-grip task, and ratings of pain at the end of the task. Concurrent skin warming showed increased MSNA compared to the other conditions. Tactile stimuli (brushing, vibration) were not significantly different to the control (no intervention) condition. Warming increased the pain from the muscle contraction, whereas the tactile stimuli did not. We interpret the effect of warming on MSNA as providing relevant afferent information during muscle contraction, which needed to be counteracted via vasoconstriction to maintain homeostasis. Brushing and vibration were less homeostatically relevant stimuli for the muscle contraction and hence had no significant effect. The findings add sensory specificity to our current understanding of homeostatic regulation through somatosensory afferent and sympathetic efferent pathways.
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| 2. |
- Ahlen, Elsa, et al.
(författare)
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Learning to read upside-down: a study of perceptual expertise and its acquisition
- 2014
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Ingår i: Experimental Brain Research. - : Springer Verlag (Germany). - 0014-4819 .- 1432-1106. ; 232:3, s. 1025-1036
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Tidskriftsartikel (refereegranskat)abstract
- Reading is an expert visual and ocular motor function, learned mainly in a single orientation. Characterizing the features of this expertise can be accomplished by contrasts between reading of normal and inverted text, in which perceptual but not linguistic factors are altered. Our goal was to examine this inversion effect in healthy subjects reading text, to derive behavioral and ocular motor markers of perceptual expertise in reading, and to study these parameters before and after training with inverted reading. Seven subjects engaged in a 10-week program of 30 half-hour sessions of reading inverted text. Before and after training, we assessed reading of upright and inverted single words for response time and word-length effects, as well as reading of paragraphs for time required, accuracy, and ocular motor parameters. Before training, inverted reading was characterized by long reading times and large word-length effects, with eye movements showing more and longer fixations, more and smaller forward saccades, and more regressive saccades. Training partially reversed many of these effects in single word and text reading, with the best gains occurring in reading aloud time and proportion of regressive saccades and the least change in forward saccade amplitude. We conclude that reading speed and ocular motor parameters can serve as markers of perceptual expertise during reading and that training with inverted text over 10 weeks results in significant gains of reading expertise in this unfamiliar orientation. This approach may be useful in the rehabilitation of patients with hemianopic dyslexia.
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| 3. |
- Björnsdotter, Malin, et al.
(författare)
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Feeling good : on the role of C fiber mediated touch in interoception.
- 2010
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Ingår i: Experimental Brain Research. - : Springer. - 0014-4819 .- 1432-1106. ; 207:3, s. 149-155
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Tidskriftsartikel (refereegranskat)abstract
- The human skin is innervated by a network of thin, slow-conducting afferent (C and Aδ) fibers, transmitting a diverse range of information. Classically, these fibers are described as thermo-, noci- or chemoreceptive, whereas mechanoreception is attributed exclusively to thick, fast-conducting (Aβ) afferents. A growing body of evidence, however, supports the notion that C tactile afferents comprise a second anatomically and functionally distinct system signaling touch in humans. This review discusses established as well as recent findings which highlight fundamental differences in peripheral and central information coding and processing between Aβ and C mechanoreception. We conclude that from the skin through the brain, C touch shares more characteristics with interoceptive modalities (e.g. pain, temperature, and itch) than exteroceptive Aβ touch, vision or hearing. In this light, we discuss the motivational-affective role of C touch as an integral part of a thin-fiber afferent homeostatic network for the maintenance of physical and social well-being.
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| 4. |
- Liedgren, Christer, et al.
(författare)
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Projection of thalamic neurons to cat primary vestibular cortical fields studied by means of retrograde axonal transport of horseradish peroxidase
- 1976
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Ingår i: Experimental Brain Research. - : Springer. - 0014-4819 .- 1432-1106. ; 24:3, s. 237-243
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Tidskriftsartikel (refereegranskat)abstract
- The two vestibular cortical projection areas in the anterior suprasylvian sulcus and post-cruciate dimple regions were defined by evoked potential technique in anaesthetized cats. The thalamic location of neurons with axon terminals in these fields was determined using the method of retrograde axonal transport of horseradish peroxidase. The ascending vestibular pathway appeared to be separated also at the thalamic level, where cells in the ventro-posterolateral nucleus were found to project to the post cruciate dimple and cells in the posterior nuclear group to the anterior suprasylvian vestibular cortical fields.
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| 5. |
- Magnusson, Anna, 1972-, et al.
(författare)
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GABAB receptors contribute to vestibular compensation after unilateral labyrinthectomy in pigmented rats
- 2000
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Ingår i: Experimental Brain Research. - : Springer Science and Business Media LLC. - 0014-4819 .- 1432-1106. ; 134:1, s. 32-41
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Tidskriftsartikel (refereegranskat)abstract
- The horizontal vestibulo-ocular reflex was studied in pigmented rats, which had been unilaterally, chemically labyrinthectomised 6–144 days previously. During this partially compensated stage after unilateral labyrinthectomy (UL), both static and dynamic deficits remain. The former was evaluated by recording of spontaneous eye movements in darkness, and the latter by estimating the slow-phase velocity (SPV) gain of compensatory eye movements during horizontal vestibular stimulation. The GABAB agonist baclofen caused a reversal of the remaining ipsilesional drift of the eyes in darkness into a nystagmus with a contralesional slow phase. The GABAB antagonist CGP 36742 caused a decompensation by exaggerating the remaining ipsilesional eye drift. Further, baclofen equilibrated or reversed the asymmetry between ipsi- and contralesional SPV gains during horizontal sinusoidal rotations at 0.2 Hz and 0.8 Hz. This was achieved by an increase in the ipsilesional gain and a decrease in the contralesional gain. The phase lead during sinusoidal rotation (0.2 Hz) was larger following rotation to the lesioned side than to the intact side in UL rats. This asymmetry was reversed by baclofen. CGP 36742 inhibited the effects of baclofen, while the antagonist per se aggravated SPV gain and phase lead asymmetries in UL rats during vestibular stimulation. Per- and post-rotatory nystagmus induced by velocity step stimulation revealed an imperfect velocity-storage function in UL animals, which was modulated by baclofen. An investigation of the baclofen effect on SPV gain asymmetry during different time intervals after chemical UL showed a completely developed effect on the 6th day. Bilateral flocculectomy did not alter the effects of baclofen on UL animals. It is concluded that physiological stimulation of GABAB receptors contributes to minimise the vestibulo-oculomotor asymmetry during the partially compensated period after UL. Administration of an agonist or an antagonist changes the asymmetry towards the ipsi- or contralesional side, possibly by altering the spontaneous neuronal activity in the bilateral medial vestibular nuclei. The results are compatible with a hypothesis, supported by in vitro slice experiments, that the efficacy of GABAB receptors is up-regulated on the ipsilesional side and down-regulated on the contralesional side.
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| 6. |
- Manouchehri, Vahideh, et al.
(författare)
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The impact of simulated hemianopia on visual search for faces, words, and cars
- 2022
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Ingår i: Experimental Brain Research. - : SPRINGER. - 0014-4819 .- 1432-1106. ; 240, s. 2835-2846
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Tidskriftsartikel (refereegranskat)abstract
- Tests of visual search can index the effects of perceptual load and compare the processing efficiency for different object types, particularly when one examines the set-size effect, the increase in search time for each additional stimulus in an array. Previous studies have shown that the set-size effect is increased by manoeuvres that impede object processing, and in patients with object processing impairments. In this study, we examine how the low-level visual impairment of hemianopia affects visual search for complex objects, using a virtual paradigm. Forty-two healthy subjects performed visual search for faces, words, or cars with full-viewing as well as gaze-contingent simulations of complete left or right hemianopia. Simulated hemianopia lowered accuracy and discriminative power and increased response times and set-size effects, similarly for faces, words and cars. A comparison of set-size effects between target absent and target present trials did not show a difference between full-view and simulated hemianopic conditions, and a model of decision-making suggested that simulated hemianopia reduced the rate of accumulation of perceptual data, but did not change decision thresholds. We conclude that simulated hemianopia reduces the efficiency of visual search for complex objects, and that such impairment should be considered when interpreting results from high-level object processing deficits.
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| 7. |
- Uysal, Hilmi, et al.
(författare)
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Medium-latency reflex response of soleus elicited by peroneal nerve stimulation
- 2009
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Ingår i: EXPERIMENTAL BRAIN RESEARCH. - : Springer Science and Business Media LLC. - 0014-4819 .- 1432-1106. ; 193:2, s. 275-286
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Tidskriftsartikel (refereegranskat)abstract
- A medium-latency response (MLR) has been recorded from soleus during stance and walking, and has been attributed to stretch-evoked volleys in group II afferents. The present paper describes a MLR in soleus evoked by stimulating the deep peroneal nerve, documents its characteristics and addresses its likely origin. The MLR of soleus was recorded in healthy subjects and hemiplegic patients, following electrical stimulation of the deep peroneal nerve at the fibula at rest, during voluntary dorsiflexion, during plantar flexion, during external restraint to the ankle dorsiflexion movement, during limb cooling, during limb ischaemia and 1 h after the ingestion of tizanidine. The dorsiflexion movement of the foot was measured using an accelerometer. During cooling, ischaemia and after tizanidine, changes in the MLR were compared with changes in the soleus H reflex, Achilles tendon reflex and, during cooling, F waves of abductor hallucis. The MLR was facilitated by voluntary dorsiflexion, was suppressed during plantar flexion, disappeared when ankle movement was prevented, and was enhanced in patients with spastic hemiplegia. Cooling delayed the MLR significantly more than the Achilles tendon reflex and the abductor hallucis F wave. During ischaemia the response was significantly less affected than the Achilles tendon reflex and the soleus H reflex. Tizanidine suppressed the MLR, but not the soleus H and tendon reflexes. The latencies and the experiments using cooling, ischaemia and tizanidine implicate soleus group II afferents in the genesis of this response.
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| 8. |
- Ödkvist, Lars, et al.
(författare)
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Vestibular and somatosensory inflow to the vestibular projection area in the post cruciate dimple region of the gat cerebral cortex
- 1975
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Ingår i: Experimental Brain Research. - : Springer. - 0014-4819 .- 1432-1106. ; 22:2, s. 185-196
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Tidskriftsartikel (refereegranskat)abstract
- In anesthetized cats 251 cells within the cortical vestibular projection area, adjacent to the post-cruciate dimple, were analyzed as to their input characteristics employing extracellular recording techniques. The post cruciate dimple vestibular field, which is located in area 3a, has a high degree of convergence between vestibular and peripheral somatosensory input. The latter is not restricted to muscle afferents but includes cutaneous modalities. The functional significance of this vestibular cortical projection field is discussed.
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