IMT Institutional Repository: No conditions. Results ordered -Date Deposited.
2024-03-28T10:47:01Z
EPrints
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http://eprints.imtlucca.it/
2017-09-05T06:41:38Z
2017-09-05T06:41:38Z
http://eprints.imtlucca.it/id/eprint/3781
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/3781
2017-09-05T06:41:38Z
The effects of acute, short-term visual deprivation
on low-frequency EEG activity during wakefulness and sleep
Introduction: experimental evidence indicates that regional changes in slow-wave activity (SWA, 0.5-4.5 Hz) during NREM-sleep, and in theta activity (5-9 Hz) during wakefulness may reflect local variations in sleep need induced by recent experience-dependent brain plasticity1. However, such evidence is mainly based on studies involving the sensorimotor domain. Previous attempts to extend these findings to a purely sensory system –such as the visual system– provided contradictory results. To clarify this issue, here we evaluated the effects of short-term visual deprivation on low-frequency EEG activity during wakefulness and sleep.
Materials and Methods: twelve healthy volunteers (25.5±3.7 yrs, 6 M) participated to two experimental sessions (order counterbalanced across participants), each lasting from ~2.30 pm to ~8.30 am of the following day: a visual deprivation (VD) condition, during which subjects were blindfolded, and a visual stimulation (VS) condition. All activities were rigorously regulated: in VD, subjects had to listen to audiobooks for ~6 h, while in VS they watched movies for a similar amount of time. All participants slept for ~7.5 h (11.30 pm – 7.00 am), while their brain activity was recorded using high-density (hd-)EEG (256 electrodes). Brief test sessions including an auditory psychomotor vigilance test (aPVT) and Likert-scales for sleepiness, alertness and mood were completed every 2 h and ~40 min after awakening. Three 2 min eyes closed hd-EEG recordings were obtained before and after sleep to investigate potential variations in local theta power. Mean SWA, slow wave density and amplitude6 were calculated for the first 20 min of NREM-sleep. Statistical analyses (paired t-tests) were restricted to an occipital and a centro-frontal region of interest (ROI).
Results: relative to VS, VD was associated with reduced N1 and REM latency and with increased REM duration and proportion (p < 0.05). No differences were observed in other sleep parameters. No significant differences between VS and VD were observed in aPVT reaction time, subjective sleepiness, alertness and mood either before or after sleep. In eyes-closed wake recordings before sleep, occipital (but not frontal) theta power was higher after VS than after VD (p < 0.03; ~11.00 pm) and this difference disappeared after a night of sleep (p > 0.23; ~8.00 am). During the first 20 min of NREM-sleep, SWA and slow wave amplitude showed no significant differences across experimental condition. However, the density of occipital (but not frontal) slow waves tended to be higher in VS (p = 0.09). Additional analyses showed that small (amplitude < 30 µV), occipital (but not large and/or frontal) slow waves were significantly more numerous after VS than after VD (p < 0.02).
Discussion: short-term visual deprivation is associated with an occipital decrease in theta activity during wakefulness, and in the density of small, local slow waves during NREM-sleep, likely reflecting local, experience-related changes in cortical plasticity. However, in contrast to previous observations involving the sensorimotor domain, sleep SWA and slow wave amplitude showed no clear changes, suggesting that important regional differences may exist with respect to the morphology of slow waves and their relation to experience-dependent modifications.
Giulio Bernardi
Monica Betta
monica.betta@imtlucca.it
Jacinthe Cataldi
Andrea Leo
Emiliano Ricciardi
emiliano.ricciardi@imtlucca.it
J. Haba-Rubio
Pietro Pietrini
pietro.pietrini@imtlucca.it
R. Heinzer
Francesca Siclari
2017-09-04T15:21:57Z
2017-09-04T15:21:57Z
http://eprints.imtlucca.it/id/eprint/3780
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/3780
2017-09-04T15:21:57Z
Quantifying peripheral sympathetic activation during sleep by means of an automatic method for pulse wave amplitude drop detection
Introduction: drops in pulse wave amplitude (PWA) measured by finger photoplethysmography (PPG) are known to reflect peripheral vasoconstriction resulting from sympathetic activation. Quantifying the amount of sympathetic activation during sleep would be useful to investigate the link between sleep disorders, like sleep apnea, and cardio-vascular morbidity-mortality. However, automatic algorithms allowing for a simple and rapid extraction and characterization of PWA parameters are not readily available. Therefore, in the present study we developed and validated a novel automatic approach to detect and characterize PWA-drops in whole-night polysomnographic (PSG) data.
Materials and Methods: PSG recordings of 9 patients (52±5yrs, 7F) from the HypnoLaus Sleep Cohort were analyzed. The PPG signal was smoothed and detrended before extraction of the PWA signal, defined at each cardiac cycle as the difference between the peak and nadir values of the corresponding PPG-waveform. The time-courses of PWA variance and first-derivative were then evaluated using a moving-window over 5 heartbeats. Candidate time-points for potential PWA-drops were defined as local peaks in the PWA-variance showing correspondent first-derivative negative values. For each PWA-drop candidate, an observation interval was delimited between the closest previous and subsequent PWA maxima, and the maximum percent decrease (amplitude) was computed with respect to the mean of the previous 5 PWA values extracted from stable signal tracts (low local variance and duration >2sec). Then, PWA-drops with amplitude >30% and duration >4 heartbeats were identified, and their amplitude (%), descending slope (%/s) and total duration (s) were estimated. The PWA-drop index was calculated as the number of drops per hour. The algorithm detections were compared with those of an expert scorer who marked PWA-drops with amplitudes >30% (3min scoring window).
Results: with respect to the human scorer, the algorithm achieved a sensitivity of 97.4%, a specificity of 89.5%, and a precision of 49.6%. In spite of the apparently low precision, both visual inspection and a direct comparison between false positive (FP) and true positive (TP) detections showed that the algorithm correctly identified above-threshold drops that were missed by the human scorer (minimum amplitude was 32.1±1.5% for FP, and 37.6±3.7% for TP). Only ~31% of all detected PWA-drops were associated with a (visually scored) EEG-arousal, whereas most EEG-arousals (~72%) showed an association with a PWA-drop. Interestingly, among PWA-drops that were not associated with a scored EEG-arousal, 19-55% (depending on sleep stage) were nevertheless accompanied by a strong increase in high-frequency EEG-power, potentially reflecting a cortical activation not visible to the human eye. Finally, the index, amplitude and duration tended to decrease from light (N1) to deep (N3) NREM sleep (p<0.05, rmANOVA), while REM sleep showed a significantly higher PWA-drop index compared to NREM stages (53.5±19.3d/h vs. 42.1±18.7d/h in N1).
Discussion: the automatic algorithm allowed to reliably detect PWA-drops occurring in all sleep stages, including events not recognized upon standard visual inspection. This automatic algorithm may represent a simple and useful tool to quantify the degree of peripheral sympathetic activation during sleep and may provide relevant information about associated ‘cortical activations’ during sleep.
Monica Betta
monica.betta@imtlucca.it
Giulio Bernardi
Emiliano Ricciardi
emiliano.ricciardi@imtlucca.it
Pietro Pietrini
pietro.pietrini@imtlucca.it
J. Haba-Rubio
Francesca Siclari
R. Heinzer
2017-09-04T14:50:49Z
2017-09-04T14:50:49Z
http://eprints.imtlucca.it/id/eprint/3779
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/3779
2017-09-04T14:50:49Z
Regionally specific features of low-frequency EEG oscillations during REM-sleep
Giulio Bernardi
Monica Betta
monica.betta@imtlucca.it
Yu Xiaoqian
Emiliano Ricciardi
emiliano.ricciardi@imtlucca.it
J. Haba-Rubio
R. Heinzer
Pietro Pietrini
pietro.pietrini@imtlucca.it
Giulio Tononi
Francesca Siclari
2017-09-04T14:47:55Z
2017-09-04T14:47:55Z
http://eprints.imtlucca.it/id/eprint/3778
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/3778
2017-09-04T14:47:55Z
Spontaneous, localized EEG activations in REM sleep: an high-density EEG investigation
Monica Betta
monica.betta@imtlucca.it
Giulio Bernardi
Danilo Menicucci
J. Haba-Rubio
R. Heinzer
Angelo Gemignani
Alberto Landi
Giulio Tononi
Francesca Siclari
2017-03-21T13:49:11Z
2017-09-04T13:34:32Z
http://eprints.imtlucca.it/id/eprint/3678
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/3678
2017-03-21T13:49:11Z
Low-frequency oscillations in REM-sleep: a high density
EEG study
Objectives: Slow waves (0.5–4 Hz) of non-rapid eye movement
(NREM) sleep occur and are regulated locally, in an experiencedependent
manner. However, recent work in mice showed that
region-specific slow waves may also occur in REM sleep. Here we
investigated the presence and cortical distribution of low-frequency
oscillations in human REM sleep using high-density EEG.
Giulio Bernardi
Monica Betta
monica.betta@imtlucca.it
X. Yu
Emiliano Ricciardi
emiliano.ricciardi@imtlucca.it
J. Haba-Rubio
R. Heinzer
Pietro Pietrini
pietro.pietrini@imtlucca.it
Giulio Tononi
Francesca Siclari
2016-01-28T11:37:59Z
2017-08-04T10:18:57Z
http://eprints.imtlucca.it/id/eprint/3032
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/3032
2016-01-28T11:37:59Z
Sleep reverts changes in human gray and white matter caused by wake-dependent training
Abstract Learning leads to rapid microstructural changes in gray (GM) and white (WM) matter. Do these changes continue to accumulate if task training continues, and can they be reverted by sleep? We addressed these questions by combining structural and diffusion weighted {MRI} and high-density {EEG} in 16 subjects studied during the physiological sleep/wake cycle, after 12 h and 24 h of intense practice in two different tasks, and after post-training sleep. Compared to baseline wake, 12 h of training led to a decline in cortical mean diffusivity. The decrease became even more significant after 24 h of task practice combined with sleep deprivation. Prolonged practice also resulted in decreased ventricular volume and increased {GM} and {WM} subcortical volumes. All changes reverted after recovery sleep. Moreover, these structural alterations predicted cognitive performance at the individual level, suggesting that sleep's ability to counteract performance deficits is linked to its effects on the brain microstructure. The cellular mechanisms that account for the structural effects of sleep are unknown, but they may be linked to its role in promoting the production of cerebrospinal fluid and the decrease in synapse size and strength, as well as to its recently discovered ability to enhance the extracellular space and the clearance of brain metabolites.
Giulio Bernardi
Luca Cecchetti
luca.cecchetti@imtlucca.it
Francesca Siclari
Andreas Buchmann
Xiaoqian Yu
Giacomo Handjaras
Michele Bellesi
Emiliano Ricciardi
emiliano.ricciardi@imtlucca.it
Steven R. Kecskemeti
Brady A. Riedner
Andrew L. Alexander
Ruth M. Benca
Maria Felice Ghilardi
Pietro Pietrini
pietro.pietrini@imtlucca.it
Chiara Cirelli
Giulio Tononi
2015-12-01T12:42:36Z
2016-09-13T09:53:21Z
http://eprints.imtlucca.it/id/eprint/2942
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/2942
2015-12-01T12:42:36Z
Conditional granger causality analysis of fMRI data shows a direct connection from LGN to hMT+ bypassing V1
The human middle temporal complex (hMT+) is devoted to motion perception. To determine whether motion-related neural information may reach hMT+ directly from the thalamus, by-passing the primary visual cortex (V1), we measured effective connectivity in an optic flow fMRI experiment in humans. Conditional Granger Causality analysis was employed to measure direct influences between the lateral geniculate nucleus (LGN) and hMT+, discarding indirect effects mediated by V1. Results indicated the existence of a bilateral alternative pathway for visual motion processing that allows for a direct flow of information from LGN to hMT+. This direct link may play a role in blindsight.
Anna Gaglianese
Mauro Costagli
Giulio Bernardi
Lorenzo Sani
Emiliano Ricciardi
emiliano.ricciardi@imtlucca.it
Pietro Pietrini
pietro.pietrini@imtlucca.it
2015-11-18T10:59:48Z
2016-09-13T09:49:55Z
http://eprints.imtlucca.it/id/eprint/2918
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/2918
2015-11-18T10:59:48Z
Evidence of a direct influence between the thalamus and hMT + independent of V1 in the human brain as measured by fMRI
In the present study we employed Conditional Granger Causality (CGC) and Coherence analysis to investigate whether visual motion-related information reaches the human middle temporal complex (hMT +) directly from the Lateral Geniculate Nucleus (LGN) of the thalamus, by-passing the primary visual cortex (V1). Ten healthy human volunteers underwent brain scan examinations by functional magnetic resonance imaging (fMRI) during two optic flow experiments. In addition to the classical LGN-V1-hMT + pathway, our results showed a significant direct influence of the blood oxygenation level dependent (BOLD) signal recorded in {LGN} over that in hMT+, not mediated by {V1} activity, which strongly supports the existence of a bilateral pathway that connects {LGN} directly to hMT + and serves visual motion processing. Furthermore, we evaluated the relative latencies among areas functionally connected in the processing of visual motion. Using {LGN} as a reference region, hMT + exhibited a statistically significant earlier peak of activation as compared to V1. In conclusion, our findings suggest the co-existence of an alternative route that directly links {LGN} to hMT+, bypassing V1. This direct pathway may play a significant functional role for the faster detection of motion and may contribute to explain persistence of unconscious motion detection in individuals with severe destruction of primary visual cortex (blindsight).
Anna Gaglianese
Mauro Costagli
Giulio Bernardi
Emiliano Ricciardi
emiliano.ricciardi@imtlucca.it
Pietro Pietrini
pietro.pietrini@imtlucca.it
2015-11-18T10:34:31Z
2017-08-04T10:19:56Z
http://eprints.imtlucca.it/id/eprint/2913
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/2913
2015-11-18T10:34:31Z
Spatial processing in the human dorsal pathway relies on supramodal functional connectivity maps
Luca Cecchetti
luca.cecchetti@imtlucca.it
Giacomo Handjaras
Giulio Bernardi
Daniela Bonino
Emiliano Ricciardi
emiliano.ricciardi@imtlucca.it
Pietro Pietrini
pietro.pietrini@imtlucca.it
2015-11-18T10:30:20Z
2016-09-13T09:51:22Z
http://eprints.imtlucca.it/id/eprint/2912
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/2912
2015-11-18T10:30:20Z
Cholinergic enhancement reduces functional connectivity and BOLD variability in visual extrastriate cortex during selective attention
Emiliano Ricciardi
emiliano.ricciardi@imtlucca.it
Giacomo Handjaras
Giulio Bernardi
Pietro Pietrini
pietro.pietrini@imtlucca.it
Maura L. Furey
2015-11-18T10:18:00Z
2016-09-13T09:50:23Z
http://eprints.imtlucca.it/id/eprint/2911
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/2911
2015-11-18T10:18:00Z
Ventral and Dorsal Stream Dissociation During Action Recognition in the Human Brain
Giacomo Handjaras
Giulio Bernardi
Pietro Pietrini
pietro.pietrini@imtlucca.it
Emiliano Ricciardi
emiliano.ricciardi@imtlucca.it
2015-11-17T11:25:36Z
2016-09-13T09:48:43Z
http://eprints.imtlucca.it/id/eprint/2907
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/2907
2015-11-17T11:25:36Z
Expertise modulates brain activity during passive driving: a study in professional and naïve drivers
Giulio Bernardi
Emiliano Ricciardi
emiliano.ricciardi@imtlucca.it
Giacomo Handjaras
Ferdinando Franzoni
Fabio Galetta
Gino Santoro
Pietro Pietrini
pietro.pietrini@imtlucca.it
2015-11-10T13:21:36Z
2016-09-13T09:51:04Z
http://eprints.imtlucca.it/id/eprint/2884
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/2884
2015-11-10T13:21:36Z
Increased BOLD Variability in the Parietal Cortex and Enhanced Parieto-Occipital Connectivity during Tactile Perception in Congenitally Blind Individuals
Previous studies in early blind individuals posited a possible role of parieto-occipital connections in conveying nonvisual information to the visual occipital cortex. As a consequence of blindness, parietal areas would thus become able to integrate a greater amount of multimodal information than in sighted individuals. To verify this hypothesis, we compared fMRI-measured BOLD signal temporal variability, an index of efficiency in functional information integration, in congenitally blind and sighted individuals during tactile spatial discrimination and motion perception tasks. In both tasks, the BOLD variability analysis revealed many cortical regions with a significantly greater variability in the blind as compared to sighted individuals, with an overlapping cluster located in the left inferior parietal/anterior intraparietal cortex. A functional connectivity analysis using this region as seed showed stronger correlations in both tasks with occipital areas in the blind as compared to sighted individuals. As BOLD variability reflects neural integration and processing efficiency, these cross-modal plastic changes in the parietal cortex, even if described in a limited sample, reinforce the hypothesis that this region may play an important role in processing nonvisual information in blind subjects and act as a hub in the cortico-cortical pathway from somatosensory cortex to the reorganized occipital areas.
Andrea Leo
Giulio Bernardi
Giacomo Handjaras
Daniela Bonino
Emiliano Ricciardi
emiliano.ricciardi@imtlucca.it
Pietro Pietrini
pietro.pietrini@imtlucca.it
2015-11-10T13:06:53Z
2016-09-13T09:47:03Z
http://eprints.imtlucca.it/id/eprint/2880
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/2880
2015-11-10T13:06:53Z
How skill expertise shapes the brain functional architecture: an fMRI study of visuo-spatial and motor processing in professional racing-car and naïve drivers
The present study was designed to investigate the brain functional architecture that subserves visuo-spatial and motor processing in highly skilled individuals. By using functional magnetic resonance imaging (fMRI), we measured brain activity while eleven Formula racing-car drivers and eleven ‘naïve’ volunteers performed a motor reaction and a visuo-spatial task. Tasks were set at a relatively low level of difficulty such to ensure a similar performance in the two groups and thus avoid any potential confounding effects on brain activity due to discrepancies in task execution. The brain functional organization was analyzed in terms of regional brain response, inter-regional interactions and blood oxygen level dependent (BOLD) signal variability. While performance levels were equal in the two groups, as compared to naïve drivers, professional drivers showed a smaller volume recruitment of task-related regions, stronger connections among task-related areas, and an increased information integration as reflected by a higher signal temporal variability. In conclusion, our results demonstrate that, as compared to naïve subjects, the brain functional architecture sustaining visuo-motor processing in professional racing-car drivers, trained to perform at the highest levels under extremely demanding conditions, undergoes both ‘quantitative’ and ‘qualitative’ modifications that are evident even when the brain is engaged in relatively simple, non-demanding tasks. These results provide novel evidence in favor of an increased ‘neural efficiency’ in the brain of highly skilled individuals.
Giulio Bernardi
Emiliano Ricciardi
emiliano.ricciardi@imtlucca.it
Lorenzo Sani
Anna Gaglianese
Alessandra Papasogli
Riccardo Ceccarelli
Ferdinando Franzoni
Fabio Galetta
Gino Santoro
Rainer Goebel
Pietro Pietrini
pietro.pietrini@imtlucca.it
2015-11-10T12:53:24Z
2017-08-04T10:19:22Z
http://eprints.imtlucca.it/id/eprint/2877
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/2877
2015-11-10T12:53:24Z
It’s not all in your car: functional and structural correlates of exceptional driving skills in professional racers
Driving is a complex behavior that requires the integration of multiple cognitive functions. While many studies have investigated brain activity related to driving simulation under distinct conditions, little is known about the brain morphological and functional architecture in professional competitive driving, which requires exceptional motor and navigational skills. Here, 11 professional racing-car drivers and 11 “naïve” volunteers underwent both structural and functional brain magnetic resonance imaging (MRI) scans. Subjects were presented with short movies depicting a Formula One car racing in four different official circuits. Brain activity was assessed in terms of regional response, using an Inter-Subject Correlation (ISC) approach, and regional interactions by mean of functional connectivity. In addition, voxel-based morphometry (VBM) was used to identify specific structural differences between the two groups and potential interactions with functional differences detected by the ISC analysis. Relative to non-experienced drivers, professional drivers showed a more consistent recruitment of motor control and spatial navigation devoted areas, including premotor/motor cortex, striatum, anterior, and posterior cingulate cortex and retrosplenial cortex, precuneus, middle temporal cortex, and parahippocampus. Moreover, some of these brain regions, including the retrosplenial cortex, also had an increased gray matter density in professional car drivers. Furthermore, the retrosplenial cortex, which has been previously associated with the storage of observer-independent spatial maps, revealed a specific correlation with the individual driver's success in official competitions. These findings indicate that the brain functional and structural organization in highly trained racing-car drivers differs from that of subjects with an ordinary driving experience, suggesting that specific anatomo-functional changes may subtend the attainment of exceptional driving performance.
Giulio Bernardi
Luca Cecchetti
luca.cecchetti@imtlucca.it
Giacomo Handjaras
Lorenzo Sani
Anna Gaglianese
Riccardo Ceccarelli
Ferdinando Franzoni
Fabio Galetta
Gino Santoro
Rainer Goebel
Emiliano Ricciardi
emiliano.ricciardi@imtlucca.it
Pietro Pietrini
pietro.pietrini@imtlucca.it
2015-11-10T12:03:08Z
2016-09-13T09:48:12Z
http://eprints.imtlucca.it/id/eprint/2874
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/2874
2015-11-10T12:03:08Z
Cholinergic enhancement reduces functional connectivity and BOLD variability in visual extrastriate cortex during selective attention
Enhancing cholinergic function improves performance on various cognitive tasks and alters neural responses in task specific brain regions. We have hypothesized that the changes in neural activity observed during increased cholinergic function reflect an increase in neural efficiency that leads to improved task performance. The current study tested this hypothesis by assessing neural efficiency based on cholinergically-mediated effects on regional brain connectivity and BOLD signal variability. Nine subjects participated in a double-blind, placebo-controlled crossover fMRI study. Following an infusion of physostigmine (1 mg/h) or placebo, echo-planar imaging (EPI) was conducted as participants performed a selective attention task. During the task, two images comprised of superimposed pictures of faces and houses were presented. Subjects were instructed periodically to shift their attention from one stimulus component to the other and to perform a matching task using hand held response buttons. A control condition included phase-scrambled images of superimposed faces and houses that were presented in the same temporal and spatial manner as the attention task; participants were instructed to perform a matching task. Cholinergic enhancement improved performance during the selective attention task, with no change during the control task. Functional connectivity analyses showed that the strength of connectivity between ventral visual processing areas and task-related occipital, parietal and prefrontal regions reduced significantly during cholinergic enhancement, exclusively during the selective attention task. Physostigmine administration also reduced BOLD signal temporal variability relative to placebo throughout temporal and occipital visual processing areas, again during the selective attention task only. Together with the observed behavioral improvement, the decreases in connectivity strength throughout task-relevant regions and {BOLD} variability within stimulus processing regions support the hypothesis that cholinergic augmentation results in enhanced neural efficiency. This article is part of a Special Issue entitled ‘Cognitive Enhancers’.
Emiliano Ricciardi
emiliano.ricciardi@imtlucca.it
Giacomo Handjaras
Giulio Bernardi
Pietro Pietrini
pietro.pietrini@imtlucca.it
Maura L. Furey
2015-11-10T11:31:09Z
2016-09-13T09:43:51Z
http://eprints.imtlucca.it/id/eprint/2868
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/2868
2015-11-10T11:31:09Z
The direct, not V1-mediated, functional influence between the thalamus and middle temporal complex in the human brain is modulated by the speed of visual motion
Abstract The main visual pathway that conveys motion information to the middle temporal complex (hMT+) originates from the primary visual cortex (V1), which, in turn, receives spatial and temporal features of the perceived stimuli from the lateral geniculate nucleus (LGN). In addition, visual motion information reaches hMT+ directly from the thalamus, bypassing the V1, through a direct pathway. We aimed at elucidating whether this direct route between {LGN} and hMT+ represents a ‘fast lane’ reserved to high-speed motion, as proposed previously, or it is merely involved in processing motion information irrespective of speeds. We evaluated functional magnetic resonance imaging (fMRI) responses elicited by moving visual stimuli and applied connectivity analyses to investigate the effect of motion speed on the causal influence between {LGN} and hMT+, independent of V1, using the Conditional Granger Causality (CGC) in the presence of slow and fast visual stimuli. Our results showed that at least part of the visual motion information from {LGN} reaches hMT+, bypassing V1, in response to both slow and fast motion speeds of the perceived stimuli. We also investigated whether motion speeds have different effects on the connections between {LGN} and functional subdivisions within hMT+: direct connections between {LGN} and MT-proper carry mainly slow motion information, while connections between {LGN} and {MST} carry mainly fast motion information. The existence of a parallel pathway that connects the {LGN} directly to hMT+ in response to both slow and fast speeds may explain why {MT} and {MST} can still respond in the presence of {V1} lesions.
Anna Gaglianese
Mauro Costagli
Kenichi Ueno
Emiliano Ricciardi
emiliano.ricciardi@imtlucca.it
Giulio Bernardi
Pietro Pietrini
pietro.pietrini@imtlucca.it
Kang Cheng
2015-11-10T11:22:29Z
2016-09-13T09:45:04Z
http://eprints.imtlucca.it/id/eprint/2866
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/2866
2015-11-10T11:22:29Z
Local sleep in wakefulness and behavioral performance
Giulio Bernardi
Francesca Siclari
D. Dentico
X. Yu
Corinna Zennig
Emiliano Ricciardi
emiliano.ricciardi@imtlucca.it
Pietro Pietrini
pietro.pietrini@imtlucca.it
Giulio Tononi
2015-11-10T11:01:36Z
2016-09-13T09:44:33Z
http://eprints.imtlucca.it/id/eprint/2863
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/2863
2015-11-10T11:01:36Z
A topographical organization for action representation in the human brain
How the human brain represents distinct motor features into a unique finalized action still remains undefined. Previous models proposed the distinct features of a motor act to be hierarchically organized in separated, but functionally interconnected, cortical areas. Here, we hypothesized that distinct patterns across a wide expanse of cortex may actually subserve a topographically organized coding of different categories of actions that represents, at a higher cognitive level and independently from the distinct motor features, the action and its final aim as a whole. Using functional magnetic resonance imaging and pattern classification approaches on the neural responses of 14 right-handed individuals passively watching short movies of hand-performed tool-mediated, transitive, and meaningful intransitive actions, we were able to discriminate with a high accuracy and characterize the category-specific response patterns. Actions are distinctively coded in distributed and overlapping neural responses within an action-selective network, comprising frontal, parietal, lateral occipital and ventrotemporal regions. This functional organization, that we named action topography, subserves a higher-level and more abstract representation of finalized actions and has the capacity to provide unique representations for multiple categories of actions. Hum Brain Mapp 36:3832–3844, 2015. © 2015 Wiley Periodicals, Inc.
Giacomo Handjaras
Giulio Bernardi
Francesca Benuzzi
Paolo Nichelli
Pietro Pietrini
pietro.pietrini@imtlucca.it
Emiliano Ricciardi
emiliano.ricciardi@imtlucca.it
2015-11-10T10:57:50Z
2016-09-13T09:43:34Z
http://eprints.imtlucca.it/id/eprint/2862
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/2862
2015-11-10T10:57:50Z
Spatial imagery relies on a sensory independent, though sensory sensitive, functional organization within the parietal cortex: A fMRI study of angle discrimination in sighted and congenitally blind individuals
Abstract Although vision offers distinctive information to space representation, individuals who lack vision since birth often show perceptual and representational skills comparable to those found in sighted individuals. However, congenitally blind individuals may result in impaired spatial analysis, when engaging in ‘visual’ spatial features (e.g., perspective or angle representation) or complex spatial mental abilities. In the present study, we measured behavioral and brain responses using functional magnetic resonance imaging in sighted and congenitally blind individuals during spatial imagery based on a modified version of the mental clock task (e.g., angle discrimination) and a simple recognition control condition, as conveyed across distinct sensory modalities: visual (sighted individuals only), tactile and auditory. Blind individuals were significantly less accurate during the auditory task, but comparable-to-sighted during the tactile task. As expected, both groups showed common neural activations in intraparietal and superior parietal regions across visual and non-visual spatial perception and imagery conditions, indicating the more abstract, sensory independent functional organization of these cortical areas, a property that we named supramodality. At the same time, however, comparisons in brain responses and functional connectivity patterns across experimental conditions demonstrated also a functional lateralization, in a way that correlated with the distinct behavioral performance in blind and sighted individuals. Specifically, blind individuals relied more on right parietal regions, mainly in the tactile and less in the auditory spatial processing. In sighted, spatial representation across modalities relied more on left parietal regions. In conclusions, intraparietal and superior parietal regions subserve supramodal spatial representations in sighted and congenitally blind individuals. Differences in their recruitment across non-visual spatial processing in sighted and blind individuals may be related to distinctive behavioral performance and/or mental strategies adopted when they deal with the same spatial representation as conveyed through different sensory modalities.
Daniela Bonino
Emiliano Ricciardi
emiliano.ricciardi@imtlucca.it
Giulio Bernardi
Lorenzo Sani
Claudio Gentili
Tomaso Vecchi
Pietro Pietrini
pietro.pietrini@imtlucca.it
2015-11-10T10:32:22Z
2016-09-13T09:43:21Z
http://eprints.imtlucca.it/id/eprint/2859
This item is in the repository with the URL: http://eprints.imtlucca.it/id/eprint/2859
2015-11-10T10:32:22Z
Neural and Behavioral Correlates of Extended Training during Sleep Deprivation in Humans: Evidence for Local, Task-Specific Effects
Recent work has demonstrated that behavioral manipulations targeting specific cortical areas during prolonged wakefulness lead to a region-specific homeostatic increase in theta activity (5–9 Hz), suggesting that theta waves could represent transient neuronal OFF periods (local sleep). In awake rats, the occurrence of an OFF period in a brain area relevant for behavior results in performance errors. Here we investigated the potential relationship between local sleep events and negative behavioral outcomes in humans.Volunteers participated in two prolonged wakefulness experiments (24 h), each including 12 h of practice with either a driving simulation (DS) game or a battery of tasks based on executive functions (EFs). Multiple high-density EEG recordings were obtained during each experiment, both in quiet rest conditions and during execution of two behavioral tests, a response inhibition test and a motor test, aimed at assessing changes in impulse control and visuomotor performance, respectively. In addition, fMRI examinations obtained at 12 h intervals were used to investigate changes in inter-regional connectivity.The EF experiment was associated with a reduced efficiency in impulse control, whereas DS led to a relative impairment in visuomotor control. A specific spatial and temporal correlation was observed between EEG theta waves occurring in task-related areas and deterioration of behavioral performance. The fMRI connectivity analysis indicated that performance impairment might partially depend on a breakdown in connectivity determined by a “network overload.”Present results demonstrate the existence of an association between theta waves during wakefulness and performance errors and may contribute explaining behavioral impairments under conditions of sleep deprivation/restriction.
Giulio Bernardi
Francesca Siclari
Xiaoqian Yu
Corinna Zennig
Michele Bellesi
Emiliano Ricciardi
emiliano.ricciardi@imtlucca.it
Chiara Cirelli
Maria Felice Ghilardi
Pietro Pietrini
pietro.pietrini@imtlucca.it
Giulio Tononi