1,720,997 research outputs found
Engagement of a parieto-cerebellar network in prism adaptation. A double-blind high-definition transcranial direct current stimulation study on healthy individuals
No full text: Prism Adaptation (PA) is a non-invasive method to investigate visuomotor control. Recent neurostimulation studies have proposed an interpretation of the mechanisms underlying PA based on functioning of brain networks, instead of focusing on single brain areas. To test the functioning of the network during a classical PA procedure, here we used for the first time High-Definition transcranial Direct Current Stimulation (HD-tDCS) to simultaneously inhibit or facilitate brain activity in two main nodes of the network, namely the parietal cortex and the cerebellum, in healthy individuals. The main results showed that simultaneous anodal HD-tDCS over the two regions reduced terminal errors during exposure to prism glasses as compared to cathodal and sham stimulation. Conversely, cathodal HD-tDCS reduced after-effect as compared to anodal and sham stimulation following prism removal. Overall, these results provide new insights on the network related to the deployment of PA mechanisms and demonstrate the feasibility of using non-invasive HD-tDCS to modulate the adaptive mechanisms of PA
Psychophysiological indices of late-life depression: A systematic review
No full textBackground: Major depression in the older population has a profound impact on patients’ quality of life and is associated with an increased risk of developing several medical illnesses. Psychophysiological methods, such as electroencephalography (EEG), functional near-infrared spectroscopy (fNIRS), and eye-tracking, have provided evidence of physiological changes associated with depression in adult life. However, these aspects have not been thoroughly investigated during late-life (over 60 years of age). Methods: A systematic review of the scientific literature covering the studies published between 1990 and 2022 was performed to describe the current evidence on easily attainable psychophysiological factors (detected by EEG, fNIRS and eye-tracking) associated with depression in late-life. Results: Twelve studies were included in the systematic review. The included studies showed some consistent physiological patterns associated with late-life depression, such as brain hypoactivation in frontal and temporal areas and attentional biases toward emotional stimuli. No reliable patterns in EEG asymmetry and power spectrum were found, in contrast to studies on early-life depression. Limitations: The small number of available studies, together with the heterogeneity in the techniques and methods used, highlight the need for further research to reliably identify the psychophysiological aspects of depression in late-life. Conclusions: Physiological indices of late-life depression, as assessed by EEG, fNIRS and eye-tracking, may differ from those of early-life. The study of these indices could better clarify the physiological mechanisms underlying late-life depression with possible clinical and research implications. Recommendations for future research are also discussed
Pleasant touch: Behavioural and hemodynamic responses to a protocol for systematic assessment of tactile stimulation
No full textPleasant touch is a form of tactile stimulation mediated by tactile C afferent fibres. It involves the encoding of the emotional value associated with tactile stimulation and subserves important social functions. Although pleasant touch has gathered increased interest in recent years, no protocol has been proposed to assess it with a robust and reliable method. In the present study we adopted a rigorous protocol for evaluating the pleasantness or unpleasantness of 9 tactile (pleasant, unpleasant, or neutral) stimuli delivered on eight body areas in healthy individuals. We recorded participants' ratings on pleasantness and intensity of the stimulus, as well as their activity in the prefrontal cortex (PFC) by functional near-infrared spectroscopy (fNIRS). A questionnaire evaluated participants' subjective experience of touch in everyday life. The behavioural results confirmed the effectiveness of the protocol as the stimuli selected to evoke pleasantness were perceived as significantly more pleasant than unpleasant and neutral ones, whereas unpleasant stimuli were perceived as more intense than all other stimuli. The participants reported the palm of the hand, particularly the left one, as the most sensitive area to tactile stimulation. Judgements of pleasantness were positively correlated with subjective experience of touch in everyday life. fNIRS data showed increased activity in the prefrontal cortex particularly during stimulation with pleasant and unpleasant stimuli, consistent with behavioural findings. Overall, this study contributes to understand the processing of pleasant touch and its neural correlates, while introducing a rigorous protocol for investigating tactile stimulation. This protocol holds promise for future utilisation in both healthy and clinical populations
The role of the dorsolateral prefrontal cortex in early threat processing: a TMS study
No full textPrevious studies demonstrated that excitatory (high frequency) offline transcranial magnetic stimulation (TMS) over the left and right dorsolateral prefrontal cortex (DLPFC) modulates attention allocation on threatening stimuli in non-clinical samples. These studies only employed offline TMS protocol that did not allow investigating the effect of the stimulation on the early stage of threat processing. In this study, the role of the right and left dorsolateral prefrontal cortex in early threat processing was investigated in high and low anxious individuals by means of an inhibitory single-pulse online TMS protocol. Our results demonstrated the role of the left DLPFC in an early stage of threat processing and that this effect is modulated by individuals' anxiety level. The inhibitory stimulation of the left DLPFC determined a disengagement bias in high anxious individuals, while the same stimulation determined an attentional avoidance in low anxious individuals. The findings of the present study suggest that right and left DLPFC are differently involved in early threat processing of healthy individuals
Cerebellar cathodal tDCS interferes with recalibration and spatial realignment during prism adaptation procedure in healthy subjects
No full textBi-cephalic parietal and cerebellar direct current stimulation interferes with early error correction in prism adaptation: Toward a complex view of the neural mechanisms underlying visuomotor control
No full textPrism Adaptation (PA) represents a valid tool to assess short-term visuomotor plasticity. Two adaptive processes are involved during PA: recalibration, contributing to early error compensation, and spatial realignment, contributing to after-effect development. Classical models on PA posit that adaptive mechanisms underlying PA rely on segregated regions in the brain. Indeed, they ascribe recalibration to the activity of the Posterior Parietal Cortex (PPC) and spatial realignment to the activity of the Cerebellum. The present experiment challenges the idea of a clear-cut separation of the role of the brain areas involved in PA, proposing an interpretation in terms of interrelated brain regions. To this purpose we interfered with the activity of the PPC and the Cerebellum by means of complementary protocols of stimulation. Bi-cephalic transcranial Direct Current Stimulation was delivered simultaneously on the PPC and the Cerebellum during PA in two groups of participants receiving real stimulation with opposite polarities (anode on PPC and cathode on Cerebellum or vice-versa) and in a control group (Sham stimulation). Differences in mean errors between groups were analyzed. Results show that the two groups of real stimulation exhibited larger displacements in early error compensation compared to the Sham Group, but they did not differ from each other. No group difference was found in late error compensation and after-effect. In conclusion, the present findings provide the first direct evidence that a brain circuit connecting the PPC and the Cerebellum is involved in early stages of visuomotor adaptation, and pave the way for updating classical models of PA
Proposal for a new tool assessing validity performance in forensic neuropsychological testing: the Test of Malingering in Abstraction Skills (TOMAS)
No full textObjective: the assessment of malingering in forensic neuropsychological testing can be supported by the use of performance validity tests (PVTs). When designing PVTs, test material should be easy enough to be insensitive to real cognitive dysfunction, but at the same time difficult enough not to appear overtly as a measure of poor effort. In the present paper, we aimed at proposing a new instrument, the Test of Malingering in Abstraction Skills (TOMAS), for detecting poor effort possibly due to malingering in forensic neuropsychological assessment; in designing the instrument, we ensured that the test had a credible level of difficulty to keep satisfactory sensitivity. Method: the TOMAS was developed as a standalone tool utilising items selected from standardised and validated neuropsychological tests assessing verbal abstraction skills. In three studies we developed the final version of the test, assessed its association with demographic and cognitive variables, and estimated its sensitivity, specificity and criterion validity in comparison with the Rey 15-items test using a simulation paradigm involving healthy participants. Results: the final version of the TOMAS includes two sections (Part A and Part B) providing multiple indexes that have an adequate discriminating power, with satisfactory sensitivity and specificity values; the discriminating power of the TOMAS is higher than that of the Rey 15-items test. Conclusion: the multiple indexes provided by the TOMAS may support clinicians in assessing poor effort during neuropsychological examination. Future evidence is needed to fully establish the validity of the instrument in clinical and forensic samples
The involvement of rTPJ in intention attribution during social decision making: A TMS study
No full textThe mini-Ultimatum Game (mini-UG) is a bargaining game used to assess the reactions of a responder to unfair offers made by a proposer under different intentionality conditions. Previous studies employing this task showed the activation of responders' right temporoparietal junction (rTPJ), which could be related to its involvement in judgments of intentionality. To verify this hypothesis, in the present study we applied online transcranial magnetic stimulation (TMS) over the rTPJ in responders during the mini-UG, in which we manipulated intention attribution implicitly. A cover story was employed to induce participants to believe they were interacting with another agent. We expected that interfering with the rTPJ could affect the ability of responders to assume proposers' perspective, producing higher rates of rejections of unfair offers when offers are perceived as independent from responders' intentionality to inequality. Twenty-six healthy women voluntarily participated in the study. In the mini-UG, an unfair distribution of the proposer (8/2 offer) was pitted against one of three alternative offers: fair-alternative (5/5), no-alternative (8/2), hyperfair-alternative (2/8). During the task, a train of TMS pulses was delivered at proposers' offer presentation in blocks of active (rTPJ) or control (Vertex) stimulation according to an ABAB design. As expected, findings showed that rejection of the no-alternative offers was higher under TMS stimulation of the rTPJ compared with the control TMS. This effect was modulated by the degree of trustworthiness in the cover story. These data contribute defining the mechanisms and brain areas underpinning social decision making as assessed by bargaining tasks
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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