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Brain : a Journal of Neurology Jun 2024Control of actions allows adaptive, goal-directed behaviour. The basal ganglia, including the subthalamic nucleus, are thought to play a central role in dynamically...
Control of actions allows adaptive, goal-directed behaviour. The basal ganglia, including the subthalamic nucleus, are thought to play a central role in dynamically controlling actions through recurrent negative feedback loops with the cerebral cortex. Here, we summarize recent translational studies that used deep brain stimulation to record neural activity from and apply electrical stimulation to the subthalamic nucleus in people with Parkinson's disease. These studies have elucidated spatial, spectral and temporal features of the neural mechanisms underlying the controlled delay of actions in cortico-subthalamic networks and demonstrated their causal effects on behaviour in distinct processing windows. While these mechanisms have been conceptualized as control signals for suppressing impulsive response tendencies in conflict tasks and as decision threshold adjustments in value-based and perceptual decisions, we propose a common framework linking decision-making, cognition and movement. Within this framework subthalamic deep brain stimulation can lead to suboptimal choices by reducing the time that patients take for deliberation before committing to an action. However, clinical studies have consistently shown that the occurrence of impulse control disorders is reduced, not increased, after subthalamic deep brain stimulation surgery. This apparent contradiction can be reconciled when recognizing the multifaceted nature of impulsivity, its underlying mechanisms and modulation by treatment. While subthalamic deep brain stimulation renders patients susceptible to making decisions without proper forethought, this can be disentangled from effects related to dopamine comprising sensitivity to benefits vs. costs, reward delay aversion and learning from outcomes. Alterations in these dopamine-mediated mechanisms are thought to underlie the development of impulse control disorders, and can be relatively spared with reduced dopaminergic medication after subthalamic deep brain stimulation. Together, results from studies using deep brain stimulation as an experimental tool have improved our understanding of action control in the human brain and have important implications for treatment of patients with Neurological disorders.
PubMed: 38869168
DOI: 10.1093/brain/awae184 -
Revista de Neurologia Jun 2024Patients who have suffered a stroke may present with visuospatial neglect (VSN). In clinical practice, different degrees of impairment can be observed among patients...
INTRODUCTION
Patients who have suffered a stroke may present with visuospatial neglect (VSN). In clinical practice, different degrees of impairment can be observed among patients with VSN; however, there is no consensus regarding the criteria and tests used to determine them.
AIM
This study aims to classify patients with VSH based on their level of impairment and to study their response to computerized cognitive training.
PATIENTS AND METHODS
The sample consisted of 34 patients (19 men and 15 women) with a mean age of 47.59 ± 8.39 years. All patients underwent a neuropsychological exploration protocol composed of specific tests that assess visuospatial attention and others to evaluate multiple cognitive domains. All participants underwent computerized cognitive training consisting of 15 one-hour sessions.
RESULTS
A cluster analysis was performed that divided the sample into three groups: group 1: mildly affected VSN (n = 17), group 2: moderately affected VSN (n = 11), and group 3: severely affected VSN (n = 6). Statistically significant differences were found in all tests of the visuospatial attention protocol, both in the pre-treatment and post-treatment evaluation.
CONCLUSIONS
There are different levels of impairment among patients with VSN, differences that persist after applying computerized cognitive training. These results suggest that the evolution of VSN follows a homogeneous pattern linked to the initial level of impairment. These findings, although preliminary, may be relevant to neurorehabilitation professionals.
Topics: Humans; Perceptual Disorders; Female; Male; Middle Aged; Retrospective Studies; Adult; Neuropsychological Tests; Aged
PubMed: 38867681
DOI: 10.33588/rn.7812.2024085 -
Clinical Oral Implants Research Jun 2024This study explored factors affecting speech improvement in patients with an edentulous maxilla after the delivery of a complete-arch implant-supported fixed dental...
OBJECTIVE
This study explored factors affecting speech improvement in patients with an edentulous maxilla after the delivery of a complete-arch implant-supported fixed dental prosthesis (IFDP).
MATERIALS AND METHODS
Patients who had received IFDP for edentulous maxilla were enrolled, and various potential speech improvement-related factors were considered, including patient demographics, anterior residual bone volume, preoperative facial features, preoperative acoustic parameters, and adaptation time. Acoustic analysis and perceptual ratings were used to assess three fricatives [s], [f], and [ɕ]. Correlation and regression analyses were conducted to assess the association between changes in fricatives and potential factors (α = .05).
RESULTS
The study included 50 patients (18 females and 32 males, aged 50.62 ± 15.71 years, range 19-76). Significant correlations were found among the change in the center of gravity (ΔCoG) of [s] and anterior residual bone volume, zygomatic implants number and proportion (p < .05). These correlations were largely mirrored in the perceptual score (ΔPS) changes. After controlling for age, sex, preoperative acoustic parameters, and adaptation time, the ΔCoG and ΔPS of fricatives were mainly correlated with the anterior residual bone volume, preoperative acoustic parameters, and adaptation time.
CONCLUSION
Speech improvements post-IFDP delivery are mainly related to preoperative speech characteristics, anterior residual bone volume, and adaptation time. The residual bone volume's impact on consonants varies with specific articulatory gestures. This study provides insights into forecasting speech outcomes following IFDP restoration and provides recommendations and methods for data collection in developing future prediction models.
PubMed: 38867397
DOI: 10.1111/clr.14311 -
Magnetic Resonance in Medical Sciences... Jul 2024Diffusion-weighted MRI (dMRI) provides a unique non-invasive view of human brain tissue properties. The present review article focuses on tractometry analysis methods... (Review)
Review
Diffusion-weighted MRI (dMRI) provides a unique non-invasive view of human brain tissue properties. The present review article focuses on tractometry analysis methods that use dMRI to assess the properties of brain tissue within the long-range connections comprising brain networks. We focus specifically on the major white matter tracts that convey visual information. These connections are particularly important because vision provides rich information from the environment that supports a large range of daily life activities. Many of the diseases of the visual system are associated with advanced aging, and tractometry of the visual system is particularly important in the modern aging society. We provide an overview of the tractometry analysis pipeline, which includes a primer on dMRI data acquisition, voxelwise model fitting, tractography, recognition of white matter tracts, and calculation of tract tissue property profiles. We then review dMRI-based methods for analyzing visual white matter tracts: the optic nerve, optic tract, optic radiation, forceps major, and vertical occipital fasciculus. For each tract, we review background anatomical knowledge together with recent findings in tractometry studies on these tracts and their properties in relation to visual function and disease. Overall, we find that measurements of the brain's visual white matter are sensitive to a range of disorders and correlate with perceptual abilities. We highlight new and promising analysis methods, as well as some of the current barriers to progress toward integration of these methods into clinical practice. These barriers, such as variability in measurements between protocols and instruments, are targets for future development.
Topics: Humans; White Matter; Visual Pathways; Diffusion Tensor Imaging; Brain; Diffusion Magnetic Resonance Imaging; Image Processing, Computer-Assisted; Vision Disorders
PubMed: 38866532
DOI: 10.2463/mrms.rev.2024-0007 -
Perception Jun 2024Researchers have been focusing on perceptual characteristics of autism spectrum disorder (ASD) in terms of sensory hyperreactivity. Previously, we demonstrated that...
Researchers have been focusing on perceptual characteristics of autism spectrum disorder (ASD) in terms of sensory hyperreactivity. Previously, we demonstrated that temporal resolution, which is the accuracy to differentiate the order of two successive vibrotactile stimuli, is associated with the severity of sensory hyperreactivity. We currently examined whether an increase in the perceptual intensity of a tactile stimulus, despite its short duration, is derived from high temporal resolution and high frequency of sensory temporal summation. Twenty ASD and 22 typically developing (TD) participants conducted two psychophysical experimental tasks to evaluate of vibrotactile stimulus with same amplitude and to evaluate temporal resolution. The sensory hyperreactivity was estimated using self-reported questionnaire. There was no relationship between the temporal resolution and the duration of detectable stimuli in both groups. However, the ASD group showed severe sensory hyperreactivity in daily life than TD group, and the ASD participants with severe sensory hyperreactivity tended to have high temporal resolution, not high sensitivity of detectable duration. Contrary to the hypothesis, there might be different processing between temporal resolution and sensitivity for stimulus detection. We suggested that the atypical temporal processing would affect to sensory reactivity in ASD.
PubMed: 38863412
DOI: 10.1177/03010066241259729 -
PLoS Biology Jun 2024Despite the diverse genetic origins of autism spectrum disorders (ASDs), affected individuals share strikingly similar and correlated behavioural traits that include...
Shared behavioural impairments in visual perception and place avoidance across different autism models are driven by periaqueductal grey hypoexcitability in Setd5 haploinsufficient mice.
Despite the diverse genetic origins of autism spectrum disorders (ASDs), affected individuals share strikingly similar and correlated behavioural traits that include perceptual and sensory processing challenges. Notably, the severity of these sensory symptoms is often predictive of the expression of other autistic traits. However, the origin of these perceptual deficits remains largely elusive. Here, we show a recurrent impairment in visual threat perception that is similarly impaired in 3 independent mouse models of ASD with different molecular aetiologies. Interestingly, this deficit is associated with reduced avoidance of threatening environments-a nonperceptual trait. Focusing on a common cause of ASDs, the Setd5 gene mutation, we define the molecular mechanism. We show that the perceptual impairment is caused by a potassium channel (Kv1)-mediated hypoexcitability in a subcortical node essential for the initiation of escape responses, the dorsal periaqueductal grey (dPAG). Targeted pharmacological Kv1 blockade rescued both perceptual and place avoidance deficits, causally linking seemingly unrelated trait deficits to the dPAG. Furthermore, we show that different molecular mechanisms converge on similar behavioural phenotypes by demonstrating that the autism models Cul3 and Ptchd1, despite having similar behavioural phenotypes, differ in their functional and molecular alteration. Our findings reveal a link between rapid perception controlled by subcortical pathways and appropriate learned interactions with the environment and define a nondevelopmental source of such deficits in ASD.
PubMed: 38857283
DOI: 10.1371/journal.pbio.3002668 -
BioRxiv : the Preprint Server For... May 2024Albinism is an inherited disorder characterized by disrupted melanin production in the eye, and often in the skin and hair. This retinal hypopigmentation is accompanied...
Albinism is an inherited disorder characterized by disrupted melanin production in the eye, and often in the skin and hair. This retinal hypopigmentation is accompanied by pathological decussation of many temporal retinal afferents at the optic chiasm during development, ultimately resulting in partially superimposed representations of opposite visual hemifields in each cortical hemisphere. Within these aberrant regions of hemifield overlap, individual voxels have been shown to have bilateral, dual population receptive fields (pRFs) responding to roughly mirror-image locations across the vertical meridian. Nonetheless, how these two conflicting inputs combine to determine a voxel's response to image contrast is still unknown. To address this, we stimulated the right and left hemifields with separately controlled sinusoidal gratings, each having a variety of contrasts (0, 8, 20, 45, 100%), and extracted voxel-wise BOLD response amplitudes to each contrast combination in visual areas V1-V3. We then compared voxels' responses to each hemifield stimulated individually with conditions when both hemifields were stimulated simultaneously. We hypothesized that simultaneous stimulation of the two pRF components will result in either a suppressive or facilitative interaction. However, we found that BOLD responses to simultaneous stimulation appeared to reflect simple summation of the neural activity from the individual hemifield conditions. This suggests that the superimposed opposite hemifield representations do not interact. Thus, dual pRFs in albinism likely reflect two co-localized, but functionally independent populations of neurons each of which respond to a single hemifield. This finding is commensurate with psychophysical studies which have shown no clear perceptual interaction between opposite visual hemifields in human albinism.
PubMed: 38853944
DOI: 10.1101/2024.05.26.595603 -
Brain and Nerve = Shinkei Kenkyu No... Jun 2024Unilateral spatial neglect (USN) is a symptom of unilateral brain damage resulting in failure to report sensory phenomena in the contra-lesional space. It is associated... (Review)
Review
Unilateral spatial neglect (USN) is a symptom of unilateral brain damage resulting in failure to report sensory phenomena in the contra-lesional space. It is associated with motor impairment as well as sensory deficits. Recent research suggests that USN, may be caused by a disruption in the interhemispheric balance of the visual attention network. Based on this hypothesis, non-invasive brain stimulation (NIBS), such as repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS), is utilized in the rehabilitation of USN patients. Presently, inhibitory stimulation by continuous theta burst stimulation (cTBS) on contra-lesional parietal cortex are believed to be the most promising method. Conversely, compensation by attentional network of the non-lesioned hemisphere plays an important role in the recovery of USN. Recent imaging studies revealed that functional and structural connectivity of attentional networks within a lesioned hemisphere and between lesioned and non-lesioned hemispheres affects spontaneous recovery and effectiveness of rehabilitation approach such as prism adaptation therapy. These findings are useful in elucidating the pathophysiology of USN and predicting functional outcome. Furthermore, we hope that understanding the pathophysiology will enable the development of new rehabilitation strategies and appropriate treatment selection.
Topics: Humans; Perceptual Disorders; Transcranial Magnetic Stimulation; Transcranial Direct Current Stimulation; Attention
PubMed: 38853505
DOI: 10.11477/mf.1416202674 -
Brain and Nerve = Shinkei Kenkyu No... Jun 2024Unilateral spatial neglect is the failure of brain-damaged patients to report, respond, or orient to novel or meaningful stimuli presented to the contralateral side of... (Review)
Review
Unilateral spatial neglect is the failure of brain-damaged patients to report, respond, or orient to novel or meaningful stimuli presented to the contralateral side of the lesion. This usually involves the right cerebral hemisphere. Neglect presents with no restriction in gaze direction and results in difficulty across various aspects of daily activities, distinguishing it from simple homonymous hemianopia. The basic mechanisms underlying neglect is rightward bias of spatial attention, while non-direction-specific cognitive problems may contribute to clinical expressions of neglect.
Topics: Humans; Perceptual Disorders; Space Perception; Attention; Functional Laterality
PubMed: 38853504
DOI: 10.11477/mf.1416202673 -
Clinical Linguistics & Phonetics Jun 2024Speech training apps are being developed that provide automatic feedback concerning children's production of known target words, as a score on a 1-5 scale. However, this...
Speech training apps are being developed that provide automatic feedback concerning children's production of known target words, as a score on a 1-5 scale. However, this 'goodness' scale is still poorly understood. We investigated listeners' ratings of 'how many stars the app should provide as feedback' on children's utterances, and whether listener agreement is affected by clinical experience and/or access to anchor stimuli. In addition, we explored the association between goodness ratings and clinical measures of speech accuracy; the Percentage of Consonants Correct (PCC) and the Percentage of Phonemes Correct (PPC). Twenty speech-language pathologists and 20 non-expert listeners participated; half of the listeners in each group had access to anchor stimuli. The listeners rated 120 words, collected from children with and without speech sound disorder. Concerning reliability, intra-rater agreement was generally high, whereas inter-rater agreement was moderate. Access to anchor stimuli was associated with higher agreement, but only for non-expert listeners. Concerning the association between goodness ratings and the PCC/PPC, correlations were moderate for both listener groups, under both conditions. The results indicate that the task of rating goodness is difficult, regardless of clinical experience, and that access to anchor stimuli is insufficient for achieving reliable ratings. This raises concerns regarding the 1-5 rating scale as the means of feedback in speech training apps. More specific listener instructions, particularly regarding the intended context for the app, are suggested in collection of human ratings underlying the development of speech training apps. Until then, alternative means of feedback should be preferred.
PubMed: 38853471
DOI: 10.1080/02699206.2024.2355470