50 research outputs found
Multi-band MEG signatures of BOLD connectivity reorganization during visuospatial attention
No full textThe functional architecture of the resting brain, as measured with the blood oxygenation level-dependent functional connectivity (BOLD-FC), is slightly modified during task performance. In previous work, we reported behaviorally relevant BOLD-FC modulations between visual and dorsal attention regions when subjects performed a visuospatial attention task as compared to central fixation (Spadone et al., 2015). Here we use magnetoencephalography (MEG) in the same group of subjects to identify the electrophysiological correlates of the BOLD-FC modulation found in our previous work. While BOLD-FC topography, separately at rest and during visual attention, corresponded to neuromagnetic Band-Limited Power (BLP) correlation in the alpha and beta bands (8–30 Hz), BOLD-FC modulations evoked by performing the visual attention task (Spadone et al. 2015) did not match any specific oscillatory band BLP modulation. Conversely, following the application of an orthogonal spatial decomposition that identifies common inter-subject co-variations, we found that attention–rest BOLD-FC modulations were recapitulated by multi-spectral BLP-FC components. Notably, individual variability of alpha connectivity between Frontal Eye Fields and visual occipital regions, jointly with decreased interaction in the Visual network, correlated with visual discrimination accuracy. In summary, task-rest BOLD connectivity modulations match multi-spectral MEG BLP connectivity
Malvinas Current 2001-2003: mooring velocities
No full textCurrentmeter moorings in the Malvinas Current from 2001-2003 (cf Spadone A. and C. Provost (2009), Variations in the Malvinas Current volume transport since October 1992, J. Geophys. Res. Oceans, 114, C02002, doi:10.1029/2008JC004882.
Spectral signature of attentional reorienting in the human brain
No full textAs we move in the environment, attention shifts to novel objects of interest based on either their sensory salience or behavioral value (reorienting). This study measures with magnetoencephalography (MEG) different properties (amplitude, onset-to-peak duration) of event-related desynchronization/synchronization (ERD/ERS) of oscillatory activity during a visuospatial attention task designed to separate activity related to reorienting vs. maintaining attention to the same location, controlling for target detection and response processes. The oscillatory activity was measured both in fMRI-defined regions of the interest (ROIs) of the dorsal attention (DAN) and visual (VIS) networks, previously defined as task-relevant in the same subjects, or whole-brain in a pre-defined set of cortical ROIs encompassing the main brain networks.
Reorienting attention (shift cues) as compared to maintaining attention (stay cues) produced a temporal sequence of ERD/ERS modulations at multiple frequencies in specific anatomical regions/networks. An early (~330 ms), stronger, transient theta ERS occurred in task-relevant (DAN, VIS) and control networks (VAN, CON, FPN), possibly reflecting an alert/reset signal in response to the cue. A more sustained, behaviorally relevant, low-beta band ERD peaking ~450 ms following shift cues (~410 for stay cues) localized in frontal and parietal regions of the DAN. This modulation is consistent with a control signal re-routing information across visual hemifields. Contralateral vs. ipsilateral shift cues produced in occipital visual regions, a stronger, sustained alpha ERD (peak ~470 ms) and a longer, transient high beta/gamma ERS (peak ~490 ms) related to preparatory visual modulations in advance of target occurrence.
This is the first description of a cascade of oscillatory processes during attentional reorienting in specific anatomical regions and networks. Among these processes, a behaviorally relevant beta desynchronization in the FEF is likely associated with the control of attention shifts
Interindividual variability in functional connectivity as long-term correlate of temporal discounting.
No full textDuring intertemporal choice (IT) future outcomes are usually devaluated as a function of the delay, a phenomenon known as temporal discounting (TD). Based on task-evoked activity, previous neuroimaging studies have described several networks associated with TD. However, given its relevance for several disorders, a critical challenge is to define a specific neural marker able to predict TD independently of task execution. To this aim, we used resting-state functional connectivity MRI (fcMRI) and measured TD during economic choices several months apart in 25 human subjects. We further explored the relationship between TD, impulsivity and decision uncertainty by collecting standard questionnaires on individual trait/state differences. Our findings indicate that fcMRI within and between critical nodes of task-evoked neural networks associated with TD correlates with discounting behavior measured a long time afterwards, independently of impulsivity. Importantly, the nodes form an intrinsic circuit that might support all the mechanisms underlying TD, from the representation of subjective value to choice selection through modulatory effects of cognitive control and episodic prospection
Supporting Natural Language Interaction with the Web
No full textConversational AI is disrupting the way information is accessed. However, there is still a lack of conversational technologies leveraging the Web. This paper introduces an approach to support the notion of Conversational Web Browsing. It illustrates design patterns for navigating websites through conversation and shows how such patterns are sustained by a Web architecture that integrates NLP technologies
Energy consumption of locomotion with orthosis versus Parastep-assisted gait: a single case study.
No full textStudy design: Single case study. Objectives: To evaluate the energy expenditure during ambulation with the Advanced Reciprocating Gait Orthosis (ARGO), with and without functional electrical stimulation (FES), and with the Parastep system in a single subject, in order to avoid the effect of intersubject variability. Setting: The Centre of Sport Medicine and Bioengineering Centre 'Don C Gnocchi' Foundation ONLUS IRCCS, Milano, Italy. Methods: A single patient (lesion level T5-T6) was trained specifically for each walking system and was evaluated after each training period. The effects of FES on muscle conditioning, spasticity and bone density were also evaluated. The HR/VO2 relationship and the energy cost of locomotion were measured during wheelchair (WHCH) use, during locomotion with ARGO (with and without FES) and Parastep system at different speeds. Results: The following was observed at the end of the whole training: (a) circumferences of both lower limbs and quadriceps forces were increased, whereas fatigue index was slightly decreased, spasticity and bone density were unchanged; (b) compared to WHCH locomotion, the slope of HR/VO2 curves with ARGO was higher (slope difference = 51.1 b 1O2-1), with ARGO + FES was similar (slope difference = -5.3 b 1O2-1) and with Parastep was smaller (slope difference = -55.6 b 1O2-1); (c) HR increased linearly with all locomotion systems, but did not rise above 125 bpm with Parastep; (d) the cost of locomotion was higher with Parastep than with ARGO (with and without FES), tested at each velocity; (e) Parastep appears to be easier to use for the subject. Conclusions: (a) FES can improve ambulation with orthosis, but the cost of locomotion remains very high; (b) the Parastep assisted gait elicits a higher energy expenditure than other orthoses, probably due to the lower speed of locomotion and to the high isometric effort of the stimulated muscles. Sponsorship: This work has been partially supported by the Italian Minister of Public Health
