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Koch G.,Laboratory of Clinical and Behavioural Neurology | Koch G.,University of Rome Tor Vergata | Bozzali M.,Neuroimaging Laboratory | Bonni S.,Laboratory of Clinical and Behavioural Neurology | And 5 more authors.
PLoS ONE | Year: 2012

Recording of slow spontaneous fluctuations at rest using functional magnetic resonance imaging (fMRI) allows distinct long-range cortical networks to be identified. The neuronal basis of connectivity as assessed by resting-state fMRI still needs to be fully clarified, considering that these signals are an indirect measure of neuronal activity, reflecting slow local variations in de-oxyhaemoglobin concentration. Here, we combined fMRI with multifocal transcranial magnetic stimulation (TMS), a technique that allows the investigation of the causal neurophysiological interactions occurring in specific cortico-cortical connections. We investigated whether the physiological properties of parieto-frontal circuits mapped with short-latency multifocal TMS at rest may have some relationship with the resting-state fMRI measures of specific resting-state functional networks (RSNs). Results showed that the activity of fast cortico-cortical physiological interactions occurring in the millisecond range correlated selectively with the coupling of fMRI slow oscillations within the same cortical areas that form part of the dorsal attention network, i.e., the attention system believed to be involved in reorientation of attention. We conclude that resting-state fMRI ongoing slow fluctuations likely reflect the interaction of underlying physiological cortico-cortical connections. © 2012 Koch et al.

Perri R.,Laboratory of Clinical and Behavioural Neurology | Monaco M.,Laboratory of Clinical and Behavioural Neurology | Fadda L.,Laboratory of Clinical and Behavioural Neurology | Fadda L.,University of Rome Tor Vergata | And 4 more authors.
Journal of Alzheimer's Disease | Year: 2014

The aim of this study was to investigate the neuropsychological correlates of behavioral and psychological symptoms (BPSD) in patients affected by various forms of dementia, namely Alzheimer's disease (AD), frontal-variant frontotemporal dementia (fvFTD), Lewy body dementia (LBD), and subcortical ischemic vascular dementia (SIVD). 21 fvFTD, 21 LBD, 22 AD, and 22 SIVD patients matched for dementia severity received a battery of neuropsychological tests and the Neuropsychiatry Inventory (NPI). The possible association between performance on neuropsychological tests and severity of BPSD was assessed by correlational analysis and multivariate regression. BPSD were present in 99% of patients. Most behavioral symptoms were not related to a particular dementia group or to a specific cognitive deficit. Euphoria and disinhibition were predicted by fvFTD diagnosis. Hallucinations correlated with the severity of visuospatial deficits in the whole sample of patients and were predicted by LBD diagnosis. Apathy, which was found in all dementia groups, correlated with executive functions and was predicted by both reduced set-shifting aptitude and fvFTD diagnosis. The results confirm the high prevalence of BPSD in the mild to moderate stages of dementia and show that most BPSD are equally distributed across dementia groups. Most of the cognitive and behavioral symptoms are independent dimensions of the dementia syndromes. Nevertheless, hallucinations in LBD and euphoria and disinhibition in fvFTD are related to the structural brain alterations that are responsible for cognitive decline in these dementia groups. Finally, apathy arises from damage in the frontal cortical areas that are also involved in executive functions. © 2014-IOS Press and the authors. All rights reserved.

PubMed | Laboratory of Clinical and Behavioural Neurology
Type: Journal Article | Journal: Neurology | Year: 2011

Cortico-cortical circuits originating from the posterior parietal cortex (PPC) of the intact left hemisphere (LH) may become hyperexcitable in patients with hemispatial neglect due to a right hemispheric (RH) stroke.In the current randomized, double-blind, sham-controlled study, we investigated safety and efficacy of continuous theta-burst stimulation (cTBS) in 10 sessions over 2 weeks applied over the intact PPC of the LH in subacute ischemic stroke patients. Severity of neglect was assessed through the standardized Behavioral Inattention Test (BIT). We also measured, by means of bifocal transcranial magnetic stimulation (TMS), how cTBS modified the excitability of the parieto-frontal functional connections in the intact LH.We found that 2 weeks of cTBS, but not sham cTBS, were effective in improving neglect symptoms as measured by BIT score. BIT scores improved by 16.3% after 2 weeks of cTBS and 22.6% at 1 month follow-up. We also found that hyperexcitability of LH parieto-frontal circuits was reduced following treatment with real but not sham cTBS.These findings suggest that a 2-week course of cTBS over the LH PPC may be a potential effective strategy in accelerating recovery from visuospatial neglect in subacute stroke patients, possibly counteracting the hyperexcitability of LH parieto-frontal circuits.This study provides Class III evidence that left posterior parietal cortex theta-burst stimulation improves hemispatial neglect for up to 2 weeks after treatment.

PubMed | Laboratory of Clinical and Behavioural Neurology
Type: Journal Article | Journal: The Neuroscientist : a review journal bringing neurobiology, neurology and psychiatry | Year: 2013

The human brain is characterized by the lateralization of cognitive functions. Multiple lines of evidence suggest the deployment of visuospatial attention is controlled by a frontoparietal network, with a right hemisphere dominance. Among cortical areas included in the network, the right posterior parietal cortex (PPC) has been proposed to be a crucial node and has also been implicated on clinical grounds. Here, the authors provide an overview of the existent literature giving evidence to a functional asymmetry of the parietal cortices in directing visuospatial attention, focusing on those studies seeking to characterize the causal role of PPC, applying transcranial magnetic stimulation and its combination with imaging techniques, such as electroencephalography and fMRI. First, the role of PPC and how this region exerts its control over remote areas of both hemispheres is discussed. The second part discusses studies involving neglect patients shedding light on the complex interplay between left and right PPC, strongly supporting the hemispheric rivalry theory. Finally, studies demonstrating changes of neglect disorders following the manipulation of the unaffected hemisphere activation will be discussed.

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