Peripheral intraneural stimulation can provide tactile information to amputees. However, efforts are still necessary to identify encoding strategy eliciting percepts that are felt as both natural and ...effective for prosthesis control. Here we compared the naturalness and efficacy of different encoding strategies to deliver neural stimulation to trans-radial amputees implanted with intraneural electrodes. Biomimetic frequency modulation was perceived as more natural, while amplitude modulation enabled better performance in tasks requiring fine identification of the applied force. Notably, the optimal combination of naturalness and sensitivity of the tactile feedback can be achieved with “hybrid” encoding strategies based on simultaneous biomimetic frequency and amplitude neuromodulation. These strategies improved the gross manual dexterity of the subjects during functional task while maintaining high levels of manual accuracy. They also improved prosthesis embodiment, reducing abnormal phantom limb perceptions (“telescoping effect”). Hybrid strategies are able to provide highly sensitive and natural percepts and should be preferred.
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•Biomimetic hybrid sensory encodings are perceived as highly natural•Biomimetic hybrid sensory encodings restore rich tactile sensitivity•Biomimetic hybrid sensory encodings improve manual dexterity and accuracy•Biomimetic hybrid sensory encodings enhance prosthesis embodiment
Sensory encoding strategies are used to convey sensory information to upper limb amputees. Valle et al. present strategies based on biomimetic approaches that improve sensation naturalness, tactile sensitivity, manual dexterity, and prosthesis embodiment.
•Alzheimer's disease is associated with pathological changes in connectivity and network structures.•Review of recent graph theory application to EEG data.•Aging and cognitive decline were evaluated.
...Graph theory applications had spread widely in understanding how human cognitive functions are linked to dynamics of neuronal network structure, providing a conceptual frame that can reduce the analytical brain complexity. This review summarizes methodological advances in this field. Electroencephalographic functional network studies in pathophysiological aging will be presented, focusing on neurodegenerative disease −such Alzheimer’s disease-aiming to discuss whether network science is changing the traditional concept of brain disease and how network topology knowledge could help in modeling resilience and vulnerability of diseases. Aim of this work is to open discussion on how network model could better describe brain architecture.
•Network science and graph theory applications can help in understanding how human cognitive functions are linked to neuronal network structure.•The present review focuses on pivotal recent studies ...regarding graph theory application on functional dynamic connectivity investigated by electroencephalographic (EEG) analysis.•Graph analysis applications represent an interesting probe to analyze the distinctive features of real life by focusing on functional connectivity networks.•Application of graph theory to patient data might provide more insight into the pathophysiological processes underlying brain disconnection.•Graph theory might aid in monitoring the impact of eventual pharmacological and rehabilitative treatments.
Network science and graph theory applications have recently spread widely to help in understanding how human cognitive functions are linked to neuronal network structure, thus providing a conceptual frame that can help in reducing the analytical brain complexity and underlining how network topology can be used to characterize and model vulnerability and resilience to brain disease and dysfunction. The present review focuses on few pivotal recent studies of our research team regarding graph theory application in functional dynamic connectivity investigated by electroencephalographic (EEG) analysis. The article is divided into two parts. The first describes the methodological approach to EEG functional connectivity data analysis. In the second part, network studies of physiological aging and neurological disorders are explored, with a particular focus on epilepsy and neurodegenerative dementias, such as Alzheimer's disease.
The growing interest in the preclinical stage of Alzheimer's disease (AD) led investigators to identify modifiable risk and predictive factors useful to design early intervention strategies. The ...preclinical stage of AD is characterized by β-amyloid (Aβ) aggregation into amyloid plaques and tau phosphorylation and aggregation into neurofibrillary tangles. There is a consensus on the importance of sleep within this context: the bidirectional relationship between sleep and AD pathology is supported by growing evidence that proved that the occurrence of sleep changes starting from the preclinical stage of AD, many years before the onset of cognitive decline. Hence, we review the most recent studies on sleep disturbances related to Aβ and the effects of sleep deprivation on Aβ accumulation in animal and human models. We also discuss evidence on the role of sleep in clearing the brain of toxic metabolic by-products, with original findings of the clearance activity of the glymphatic system stimulated by sleep. Furthermore, starting from new recent advances about the relationship between slow-wave sleep (SWS) and Aβ burden, we review the results of recent electroencephalographic (EEG) studies in order to clarify the possible role of SWS component disruption as a novel mechanistic pathway through which Aβ pathology may contribute to cognitive decline and, conversely, the eventual useful role of SWS in facilitating Aβ clearance. Finally, we discuss some promising innovative, effective, low-risk, non-invasive interventions, although empirical evidence on the efficacy of sleep interventions in improving the course of AD is at the very beginning.
Hand loss is a highly disabling event that markedly affects the quality of life. To achieve a close to natural replacement for the lost hand, the user should be provided with the rich sensations that ...we naturally perceive when grasping or manipulating an object. Ideal bidirectional hand prostheses should involve both a reliable decoding of the user's intentions and the delivery of nearly "natural" sensory feedback through remnant afferent pathways, simultaneously and in real time. However, current hand prostheses fail to achieve these requirements, particularly because they lack any sensory feedback. We show that by stimulating the median and ulnar nerve fascicles using transversal multichannel intrafascicular electrodes, according to the information provided by the artificial sensors from a hand prosthesis, physiologically appropriate (near-natural) sensory information can be provided to an amputee during the real-time decoding of different grasping tasks to control a dexterous hand prosthesis. This feedback enabled the participant to effectively modulate the grasping force of the prosthesis with no visual or auditory feedback. Three different force levels were distinguished and consistently used by the subject. The results also demonstrate that a high complexity of perception can be obtained, allowing the subject to identify the stiffness and shape of three different objects by exploiting different characteristics of the elicited sensations. This approach could improve the efficacy and "life-like" quality of hand prostheses, resulting in a keystone strategy for the near-natural replacement of missing hands.
Brain activity is complex; a reflection of its structural and functional organization. Among other measures of complexity, the fractal dimension is emerging as being sensitive to neuronal damage ...secondary to neurological and psychiatric diseases. Here, we calculated Higuchi's fractal dimension (HFD) in resting-state eyes-closed electroencephalography (EEG) recordings from 41 healthy controls (age: 20-89 years) and 67 Alzheimer's Disease (AD) patients (age: 50-88 years), to investigate whether HFD is sensitive to brain activity changes typical in healthy aging and in AD. Additionally, we considered whether AD-accelerating effects of the copper fraction not bound to ceruloplasmin (also called "free" copper) are reflected in HFD fluctuations. The HFD measure showed an inverted U-shaped relationship with age in healthy people (R2 = .575, p < .001). Onset of HFD decline appeared around the age of 60, and was most evident in central-parietal regions. In this region, HFD decreased with aging stronger in the right than in the left hemisphere (p = .006). AD patients demonstrated reduced HFD compared to age- and education-matched healthy controls, especially in temporal-occipital regions. This was associated with decreasing cognitive status as assessed by mini-mental state examination, and with higher levels of non-ceruloplasmin copper. Taken together, our findings show that resting-state EEG complexity increases from youth to maturity and declines in healthy, aging individuals. In AD, brain activity complexity is further reduced in correlation with cognitive impairment. In addition, elevated levels of non-ceruloplasmin copper appear to accelerate the reduction of neural activity complexity. Overall, HDF appears to be a proper indicator for monitoring EEG-derived brain activity complexity in healthy and pathological aging.
Increasing evidence supports the notion that brain plasticity involves distinct functional and structural components, each entailing a number of cellular mechanisms operating at different time ...scales, synaptic loci, and developmental phases within an extremely complex framework. However, the exact relationship between functional and structural components of brain plasticity/connectivity phenomena is still unclear and its explanation is a major challenge within modern neuroscience. Transcranial magnetic stimulation (TMS), with or without electroencephalography (EEG), is a sensitive and objective measure of the effect of different kinds of noninvasive manipulation of the brain's activity, particularly of the motor cortex. Moreover, the key feature of TMS and TMS-EEG coregistration is their crucial role in tracking temporal dynamics and inner hierarchies of brain functional and effective connectivities, possibly clarifying some essential issues underlying brain plasticity. All together, the findings presented here are significant for the adoption of the TMS and TMS-EEG coregistration techniques as a tool for basic neurophysiologic research and, in the future, even for clinical diagnostics purposes.
Transcranial direct current stimulation (tDCS) is able to generate a long-term increase or decrease in the neuronal excitability that can modulate cognitive tasks, similar to repetitive transcranial ...magnetic stimulation. The aim of this study was to explore the effects of tDCS on a language task in young healthy subjects. Anodal, cathodal and sham tDCS were applied to the left dorsolateral prefrontal cortex (DLPFC) before two picture naming experiments, a preliminary study (i.e., experiment 1) and a main study (i.e., experiment 2). The results show that anodal tDCS of the left DLPFC improves naming performance, speeding up verbal reaction times after the end of the stimulation, whereas cathodal stimulation had no effect. We hypothesize that the cerebral network dedicated to lexical retrieval processing is facilitated by anodal tDCS to the left DLPFC. Although the mechanisms responsible for facilitation are not yet clear, the results presented herein implicate a facilitation lasting beyond the end of the stimulation that imply cortical plasticity mechanisms. The opportunity to non-invasively interact with the functioning of these plasticity mechanisms will surely open new and promising scenarios in language studies in basic and clinical neuroscience fields.
Highlights • Numerous studies have shown that repetitive transcranial magnetic stimulation (rTMS) produced significant clinical effects in patients with various neurological and psychiatric ...disorders. • This review presents guidelines on the therapeutic use of rTMS issued by a group of European experts. • Level A or B evidence supports an efficacy of rTMS protocols in depression, pain, motor stroke and schizophrenia.
The aim of this study is to validate the Italian version of the Pittsburgh Sleep Quality Index (PSQI), comparing five different groups of individuals (healthy young and elderly, sleep apnoea syndrome ...patients, depressed patients, individuals with dementia) by both questionnaire scores and polysomnographic measures. Fifty individuals (10 for each group) participated in the study. Each of them filled in the PSQI and slept for two consecutive nights in the sleep laboratory. The PSQI showed an overall reliability coefficient (Cronbach’s α) of 0.835, indicating a high degree of internal consistency. The mean PSQI global score showed significant differences between groups, with an impaired overall quality of sleep in patients’ groups with respect to both the healthy groups. Results also indicated that the best cut-off score (differentiating “good” from “bad” sleepers) is 5. Pittsburgh Sleep Quality Index is a useful, valid and reliable tool for the assessment of sleep quality, with an overall efficiency comparable to the mother language version and differentiate “good” from “bad” sleepers. The Italian version of the questionnaire provides a good and reliable differentiation between normal and pathological groups, with higher scores reported by people characterized by impaired objectively evaluated sleep quality.
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