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Scientific Reports Jun 2024Visual hallucinations in Lewy body disease (LBD) can be differentiated based on phenomenology into minor phenomena (MVH) and complex hallucinations (CVH). MVH include a...
Visual hallucinations in Lewy body disease (LBD) can be differentiated based on phenomenology into minor phenomena (MVH) and complex hallucinations (CVH). MVH include a variety of phenomena, such as illusions, presence and passage hallucinations occurring at early stages of LBD. The neural mechanisms of visual hallucinations are largely unknown. The hodotopic model posits that the hallucination state is due to abnormal activity in specialized visual areas, that occurs in the context of wider network connectivity alterations and that phenomenology of VH, including content and temporal characteristics, may help identify brain regions underpinning these phenomena. Here we investigated both the topological and hodological neural basis of visual hallucinations integrating grey and white matter imaging analyses. We studied LBD patients with VH and age matched healthy controls (HC). VH were assessed using a North-East-Visual-Hallucinations-Interview that captures phenomenological detail. Then we applied voxel-based morphometry and tract based spatial statistics approaches to identify grey and white matter changes. First, we compared LBD patients and HC. We found a reduced grey matter volume and a widespread damage of white tracts in LBD compared to HC. Then we tested the association between CVH and MVH and grey and white matter indices. We found that CVH duration was associated with decreased grey matter volume in the fusiform gyrus suggesting that LBD neurodegeneration-related abnormal activity in this area is responsible for CVH. An unexpected finding was that MVH severity was associated with a greater integrity of white matter tracts, specifically those connecting dorsal, ventral attention networks and visual areas. Our results suggest that networks underlying MVH need to be partly intact and functional for MVH experiences to occur, while CVH occur when cortical areas are damaged. The findings support the hodotopic view and the hypothesis that MVH and CVH relate to different neural mechanisms, with wider implications for the treatment of these symptoms in a clinical context.
Topics: Humans; Hallucinations; Lewy Body Disease; Gray Matter; Female; White Matter; Male; Aged; Magnetic Resonance Imaging; Aged, 80 and over; Case-Control Studies; Middle Aged
PubMed: 38926597
DOI: 10.1038/s41598-024-65536-w -
Nature Jun 2024A deep understanding of how the brain controls behaviour requires mapping neural circuits down to the muscles that they control. Here, we apply automated tools to...
A deep understanding of how the brain controls behaviour requires mapping neural circuits down to the muscles that they control. Here, we apply automated tools to segment neurons and identify synapses in an electron microscopy dataset of an adult female Drosophila melanogaster ventral nerve cord (VNC), which functions like the vertebrate spinal cord to sense and control the body. We find that the fly VNC contains roughly 45 million synapses and 14,600 neuronal cell bodies. To interpret the output of the connectome, we mapped the muscle targets of leg and wing motor neurons using genetic driver lines and X-ray holographic nanotomography. With this motor neuron atlas, we identified neural circuits that coordinate leg and wing movements during take-off. We provide the reconstruction of VNC circuits, the motor neuron atlas and tools for programmatic and interactive access as resources to support experimental and theoretical studies of how the nervous system controls behaviour.
PubMed: 38926570
DOI: 10.1038/s41586-024-07389-x -
Scientific Reports Jun 2024Based on the auditory periphery and the small head size, Etruscan shrews (Suncus etruscus) approximate ancestral mammalian conditions. The auditory brainstem in this...
Based on the auditory periphery and the small head size, Etruscan shrews (Suncus etruscus) approximate ancestral mammalian conditions. The auditory brainstem in this insectivore has not been investigated. Using labelling techniques, we assessed the structures of their superior olivary complex (SOC) and the nuclei of the lateral lemniscus (NLL). There, we identified the position of the major nuclei, their input pattern, transmitter content, expression of calcium binding proteins (CaBPs) and two voltage-gated ion channels. The most prominent SOC structures were the medial nucleus of the trapezoid body (MNTB), the lateral nucleus of the trapezoid body (LNTB), the lateral superior olive (LSO) and the superior paraolivary nucleus (SPN). In the NLL, the ventral (VNLL), a specific ventrolateral VNLL (VNLLvl) cell population, the intermediate (INLL) and dorsal (DNLL) nucleus, as well as the inferior colliculus's central aspect were discerned. INLL and VNLL were clearly separated by the differential distribution of various marker proteins. Most labelled proteins showed expression patterns comparable to rodents. However, SPN neurons were glycinergic and not GABAergic and the overall CaBPs expression was low. Next to the characterisation of the Etruscan shrew's auditory brainstem, our work identifies conserved nuclei and indicates variable structures in a species that approximates ancestral conditions.
Topics: Animals; Shrews; Superior Olivary Complex; Auditory Pathways; Neurons; Inferior Colliculi; Calcium-Binding Proteins; Brain Stem; Male; Olivary Nucleus
PubMed: 38926520
DOI: 10.1038/s41598-024-65451-0 -
Scientific Reports Jun 2024In electroretinographic (ERG) recordings of zebrafish, the light stimulus is usually delivered by a fiber optic cable. The purpose of this study was to determine whether...
In electroretinographic (ERG) recordings of zebrafish, the light stimulus is usually delivered by a fiber optic cable. The purpose of this study was to determine whether the angle of incidence of the stimulus light from the fiber optic cable will affect the amplitudes and implicit times of the ERGs of zebrafish larvae. The larvae were positioned on their side with the right eye pointed upward. The light stimuli were delivered by a fiber optic cable from three directions of the larvae: frontal 0° (F0°), dorsal 30°(D30°), and ventral 30°(V30°). Photopic ERGs were recorded from 16 larvae at age 5-6 days post-fertilization. Our results showed that the mean amplitude of the b-wave elicited at D30° and V30° stimulation was significantly smaller than that elicited at F0° stimulation (P = 0.014 and P = 0.019, respectively). In addition, the mean amplitude of the d-wave elicited at D30° and V30° stimulation was significantly smaller than that elicited at F0° stimulation (P < 0.0001 and P = 0.015, respectively). However, the difference between the b-wave amplitudes elicited at D30° and V30° stimuli were not significant (P = 0.98), and the d-wave amplitudes were also not significantly different (P = 0.20). The average b-wave amplitudes elicited at D30° stimulation was 84.6 ± 15.7% and V30° stimulation was 84.8 ± 17.4% relative to that of F0° stimulation. The average d-wave amplitudes elicited by D30° stimulation was 85.5 ± 15.2% and by V30° stimulation was 79.0 ± 11.0% relative to that of F0° stimulation. The differences in the implicit times of the b- and d-wave elicited by the different directions of stimulation were not significant (P = 0.52 and P = 0.14, respectively). We conclude that the amplitude of the photopic ERGs is affected by the angle of the incident light. Thus, it would be better to use ganzfeld stimuli to elicit maximum b- and d-wave amplitudes of the photopic ERGs of zebrafish larvae.
Topics: Animals; Zebrafish; Electroretinography; Larva; Photic Stimulation; Light; Retina
PubMed: 38926421
DOI: 10.1038/s41598-024-65017-0 -
ENeuro Jun 2024Layer 6 corticothalamic (L6 CT) neurons provide massive input to the thalamus, and these feedback connections enable the cortex to influence its own sensory input by...
Layer 6 corticothalamic (L6 CT) neurons provide massive input to the thalamus, and these feedback connections enable the cortex to influence its own sensory input by modulating thalamic excitability. However, the functional role(s) feedback serves during sensory processing is unclear. One hypothesis is that CT feedback is under the control of extra-sensory signals originating from higher-order cortical areas, yet we know nothing about the mechanisms of such control. It is also unclear whether such regulation is specific to CT neurons with distinct thalamic connectivity. Using mice (either sex) combined with in vitro electrophysiology techniques, optogenetics, and retrograde labeling, we describe studies of vibrissal primary motor cortex (vM1) influences on different CT neurons in the vibrissal primary somatosensory cortex (vS1) with distinct intrathalamic axonal projections. We found that vM1 inputs are highly selective, evoking stronger postsynaptic responses in Dual ventral posterior medial nucleus (VPm) and posterior medial nucleus (POm) projecting CT neurons located in lower L6a than VPm-only projecting CT cells in upper L6a. A targeted analysis of the specific cells and synapses involved revealed that the greater responsiveness of Dual CT neurons was due to their distinctive intrinsic membrane properties and synaptic mechanisms. These data demonstrate that vS1 has at least two discrete L6 CT subcircuits distinguished by their thalamic projection patterns, intrinsic physiology, and functional connectivity with vM1. Our results also provide insights into how a distinct CT subcircuit may serve specialized roles specific to contextual modulation of tactile-related sensory signals in the somatosensory thalamus during active vibrissa movements. Layer 6 corticothalamic (L6 CT) feedback circuits are ubiquitous across mammalian species and modalities, and their activities have a strong influence on thalamic excitability and information throughput to the neocortex. Despite clear evidence of CT effects on the thalamus, we know relatively little about how CT cells themselves are regulated. Our results show that input from the primary motor cortex strongly excites a subclass of CT neurons in the primary somatosensory cortex that innervate both core and higher-order somatosensory nuclei rather than those exclusively targeting core somatosensory thalamus. The cortico-cortico-thalamic pathway formed by these connections establishes a circuit-level substrate for supporting CT influence operating under the guidance of ongoing motor activities.
PubMed: 38926084
DOI: 10.1523/ENEURO.0255-24.2024 -
Veterinary Anaesthesia and Analgesia Jun 2024To evaluate the effect of body position on transesophageal atrial pacing (TEAP) in dogs.
OBJECTIVE
To evaluate the effect of body position on transesophageal atrial pacing (TEAP) in dogs.
STUDY DESIGN
Prospective, experimental trial.
ANIMALS
A total of eight mixed-breed dogs, median body mass 25 kg (range 11-31 kg).
METHODS
TEAP was performed using a 6 Fr (2 mm) pacing catheter introduced transorally and positioned in the lower esophagus in left lateral recumbency. The catheter was withdrawn in 5 mm increments until successful TEAP. The minimum pacing threshold (MPT) was determined at each 5 mm increment until atrial capture could not be achieved at a maximal pulse amplitude of 40 mA. The zone of capture (ZOC) was the total distance over which TEAP was achieved. The same process was repeated in right lateral, ventral and dorsal recumbency. A linear mixed model was used to assess the impact of body position on TEAP and ZOC.
RESULTS
TEAP was achieved in all body positions. There was significant random effect of individual dogs on ZOC (p = 0.048) but not on MPT (p = 0.109). MPT was 11.56 ± 8.65 mA (mean ± SD), 8.43 ± 2.29 mA, 10.63 ± 6.91 mA and 10 ± 7.44 mA for dorsal, left and right lateral, and ventral recumbency, respectively. ZOC was 5.12 ± 2.08 cm, 6.35 ± 2.41 cm, 5.94 ± 3.23 cm and 5.31 ± 2.2 cm for dorsal, left lateral and right lateral, and ventral recumbency, respectively. Neither ZOC (p = 0.363) nor MPT (p = 0.716) varied significantly between body positions.
CONCLUSIONS AND CLINICAL RELEVANCE
TEAP can be performed successfully in all body positions in dogs. Body position did not significantly influence MPT or ZOC values for TEAP. Further studies are needed to compare the efficacy of TEAP with the efficacy of standard pharmacological therapy for management of bradycardia during general anesthesia in dogs.
PubMed: 38926065
DOI: 10.1016/j.vaa.2024.06.001 -
BMJ Case Reports Jun 2024Large ventral hernias require complex surgical techniques, such as component separation. We are presenting a case of an incisional hernia measuring 15×8 cm. The...
Large ventral hernias require complex surgical techniques, such as component separation. We are presenting a case of an incisional hernia measuring 15×8 cm. The hernia was covered with an overlying thin layer of skin and hernia sac. The skin of this layer was densely adherent to the underlying hernial sac. Because of the thin hernial sac and adherent nature of the skin, approximately 3 cm of the hernial sac was preserved. We used this hernial sac as the anterior sheath 'extension' for a tension-free closure. Posterior component separation with transverse abdominis muscle release was done to close the posterior layer without tension and to place a 23×16 cm mesh in the retrorectus plane. By using the hernial sac in repair, we avoided anterior component separation and achieved tension-free closure of the anterior layer.
Topics: Humans; Hernia, Ventral; Incisional Hernia; Herniorrhaphy; Surgical Mesh; Female; Male; Middle Aged
PubMed: 38925674
DOI: 10.1136/bcr-2024-261046 -
Urology Jun 2024To analyze current standards in urethroplasty by urologists employing buccal mucosal grafts (BMG) for treating urethral stricture disease (USD).
OBJECTIVES
To analyze current standards in urethroplasty by urologists employing buccal mucosal grafts (BMG) for treating urethral stricture disease (USD).
METHODS
An IRB-approved online survey was distributed to members of the Society of Genitourinary Reconstructive Surgeons (GURS) between July and October 2022 to assess BMG utilization in urethroplasty. Questions covered surgeon experience, graft harvest site, graft length, surgical technique, and perceived success rates.
RESULTS
Of 350 invited GURS members, 134 responded (38%). 69% were GURS fellowship-trained, performing 10-30 urethroplasties annually. 95% harvested their own grafts, with 99% preferring buccal mucosa as the primary site. Buccal mucosa was favored over fasciocutaneous flap for penile urethroplasty, regardless of circumcision status (95% with, 84% without). For bulbar urethroplasty with BMG, dorsal graft placement was favored (66%) over ventral (34%). Most surgeons (90%) preferred multiple BMGs over combined graft/flap for panurethral strictures. When harvesting long grafts, 56% preferred using both cheeks. Anastomotic urethroplasty was preferred over buccal graft urethroplasty for short bulbomembranous stenosis post-radiotherapy (63% vs. 37%). Surgeons reported a success rate of 80-90% (53%).
CONCLUSIONS
The expanded scope of reconstructive urology has led to increased use of BMG in diverse urethral reconstructions. Buccal grafts are now preferred for penile, bulbar, and panurethral strictures, demonstrating high perceived success rates in the reconstructive community.
PubMed: 38925372
DOI: 10.1016/j.urology.2024.06.019 -
Current Biology : CB Jun 2024Environmental cues, through Pavlovian learning, become conditioned stimuli that invigorate and guide animals toward rewards. Dopamine (DA) neurons in the ventral...
Environmental cues, through Pavlovian learning, become conditioned stimuli that invigorate and guide animals toward rewards. Dopamine (DA) neurons in the ventral tegmental area (VTA) and substantia nigra (SNc) are crucial for this process, via engagement of a reciprocally connected network with their striatal targets. Critically, it remains unknown how dopamine neuron activity itself engages dopamine signals throughout the striatum, across learning. Here, we investigated how optogenetic Pavlovian cue conditioning of VTA or SNc dopamine neurons directs cue-evoked behavior and shapes subregion-specific striatal dopamine dynamics. We used a fluorescent biosensor to monitor dopamine in the nucleus accumbens (NAc) core and shell, dorsomedial striatum (DMS), and dorsolateral striatum (DLS). We demonstrate spatially heterogeneous, learning-dependent dopamine changes across striatal regions. Although VTA stimulation-evoked robust dopamine release in NAc core, shell, and DMS, predictive cues preferentially recruited dopamine release in NAc core, starting early in training, and DMS, late in training. Negative prediction error signals, reflecting a violation in the expectation of dopamine neuron activation, only emerged in the NAc core and DMS. Despite the development of vigorous movement late in training, conditioned dopamine signals did not emerge in the DLS, even during Pavlovian conditioning with SNc dopamine neuron activation, which elicited robust DLS dopamine release. Together, our studies show a broad dissociation in the fundamental prediction and reward-related information generated by VTA and SNc dopamine neuron populations and signaled by dopamine across the striatum. Further, they offer new insight into how larger-scale adaptations across the striatal network emerge during learning to coordinate behavior.
PubMed: 38925117
DOI: 10.1016/j.cub.2024.05.069 -
Journal of Neural Engineering Jun 2024Speech brain-computer interfaces (BCIs) have the potential to augment communication in individuals with impaired speech due to muscle weakness, for example in ALS and...
OBJECTIVE
Speech brain-computer interfaces (BCIs) have the potential to augment communication in individuals with impaired speech due to muscle weakness, for example in ALS and other neurological disorders. However, to achieve long-term, reliable use of a speech BCI, it is essential for speech-related neural signal changes to be stable over long periods of time. Here we study, for the first time, the stability of speech-related electrocorticographic (ECoG) signals recorded from a chronically implanted ECoG BCI over a 12 month period.
APPROACH
ECoG signals were recorded by an ECoG array implanted over the ventral sensorimotor cortex (vSMC) in a clinical trial participant with ALS. Because ECoG-based speech decoding has most often relied on broadband high gamma signal changes relative to baseline (non-speech) conditions, we studied longitudinal changes of high gamma band (HG) power at baseline and during speech, and we compared these with residual high frequency (HF) noise levels at baseline. Stability was further assessed by longitudinal measurements of signal-to-noise ratio (SNR), activation ratio (ActR), and peak speech-related HG response magnitude (HG response peaks). Lastly, we analyzed the stability of the event-related HG power changes (HG responses) for individual syllables at each electrode.
MAIN RESULTS
We found that speech-related ECoG signal responses were stable over a range of syllables activating different articulators for the first year after implantation.
SIGNIFICANCE
Together, our results indicate that ECoG can be a stable recording modality for long-term speech BCI systems for those living with severe paralysis.
CLINICALTRIALS
gov, registration number NCT03567213.
PubMed: 38925110
DOI: 10.1088/1741-2552/ad5c02