Posterior parietal cortex (PPC) has connections with motor and premotor cortex, thought to transfer information relevant for planning movements in space. We used twin-coil transcranial magnetic ...stimulation (tcTMS) methods to show that the functional interplay between human right PPC and ipsilateral motor cortex (M1) varies with current motor plans. tcTMS during the reaction time of a reach task revealed facilitatory influences of right PPC on right M1 only when planning a (contralateral) leftward rather than rightward reach, at two specific time intervals (50 and 125 ms) after an auditory cue. The earlier reach-direction-specific facilitatory influence from PPC on M1 occurred when subjects were blindfolded or when the targets were presented briefly, so that visual feedback corrections could not occur. PPC-M1 interplay was similar within the left hemisphere but was specific to (contralateral) rightward planned reaches, with peaks at 50 and 100 ms. Functional interplay between human parietal and motor cortex is enhanced during early stages of planning a reach in the contralateral direction.
Abstract Background The gene encoding brain-derived neurotrophic factor ( BDNF ) has been suggested as a candidate for major depression, and for depression susceptibility in different neurological ...and psychiatric diseases. No study has investigated the role of BDNF genetic variation and depressive symptoms in Alzheimer's disease (AD). Objective The aim of this study was to assess the genetic contribution of BDNF Val66Met functional polymorphism to AD-related depression. Methods Two-hundred and sixty-four AD patients underwent clinical and neuropsychological examination as well as an evaluation of behavioral and psychiatric disturbances. They were subsequently divided into two subgroups according to the presence (AD-D) or the absence (AD-nD), based on DSM-IV criteria for depression in AD. In each subject, BDNF Val66Met functional polymorphism and apolipoprotein E ( APOE ) genotype were evaluated. Results In our sample, 35.2% of patients ( n = 93) reported AD-related depressive symptoms. Compared to patients bearing no polymorphisms ( BDNF G/G), BDNF G/A carriers showed more than twofold-time risk (OR = 2.38; 95%CI = 1.38–4.13), and BDNF A/A carriers had a threefold-time risk (OR = 3.04; 95%CI = 1.15–8.00) for depression in AD. Accordingly, considering the allele frequencies, BDNF A allele was significantly over-represented in AD-D (32.8%) compared to AD-nD (19.0%) (OR = 2.08; 95%CI = 1.38–3.13). An association between the number of carried A allele and the severity of depressive symptoms was observed ( P < 0.002). No effect of APOE genotype on risk for depression was found. Conclusions The present findings provide evidence of BDNF genetic variation role in the susceptibility to AD-related depression. This study puts emphasis on the usefulness of considering genetic background for better defining individualized risk profiles in AD.
Abstract
Objective
Impaired self-awareness (ISA) of altered functional capacities is a common sequelae of severe acquired brain injury that can severely hamper neuro-rehabilitation in this clinical ...population. ISA is frequently associated with anosodiaphoria and/or apathy. Although several scales are available to measure apathy, no tools have been published to specifically assess anosodiaphoria after acquired brain injury. In this paper, we reported an initial effort to develop an anosodiaphoria subscale in a commonly used measure of ISA, that is, the Patient Competency Rating scale-neurorehabilitation form (PCRS-NR).
Method
A sample of 46 participants with severe acquired brain injury completed a functional, ISA, apathy, and anosodiaphoria assessment. One informal caregiver of each patient participated in the study. Thus, we were able to obtain external data on his/her level of functional competencies, and self-awareness, which allowed separating patients with low self-awareness (LSA) from those with high self-awareness (HSA). Finally, the patients were compared with 44 healthy age–gender–years of formal education matched control participants (HCs).
Results
Compared to both patients with HSA and HCs, patients with LSA demonstrated greater anosodiapvhoria and lower levels of functioning than both HSA patients and HCs. A stronger relationship emerged between ISA and anosodiaphoria rather than with apathy.
Conclusions
These initial findings provide support that PCRS scale can be adapted to measure anosodiaphoria as well as ISA. The findings reveal a stronger correlation between this measure of anosodiaphoria and ISA compared with the correlation of apathy to ISA. The present method for measuring anosodiaphoria takes into account the actual levels of patients’ functioning.
Abstract Objective This study examines the effects of subthalamic nucleus (STN) deep brain stimulation (DBS) and pedunculopontine tegmentum (PPTg) DBS in advanced Parkinson's disease using gait ...analysis. Methods Five people underwent bilateral DBS in both the STN and PPTg. Gait analysis was performed one year after neurosurgery using an optoelectronic system. The effects of DBS (STN, PPTg and STN + PPTg) were studied in two clinical conditions: without (Off) and during (On) antiparkinsonian therapy. Results PPTg and STN DBS were associated with changes in spatio-temporal and kinematics variables. Conclusions Although experimental data cannot be generalized widely due to the small sample, PPTg DBS appears to affect the neuronal circuits subserving gait.
Detecting errors in your own and others' actions is associated with discrepancies between intended and expected outcomes. The processing of salient events is associated with dopamine release, the ...balance of which is altered in Parkinson's disease (PD). Errors in observed actions trigger various electrocortical indices (e.g. mid-frontal theta, error-related delta, and error positivity oPe). However, the impact of dopamine depletion to observed errors in the same individual remains unclear. Healthy controls (HCs) and PD patients observed ecological reach-to-grasp-a-glass actions performed by a virtual arm from a first-person perspective. PD patients were tested under their dopaminergic medication (on-condition) and after dopaminergic withdrawal (off-condition). Analyses of oPe, delta, and theta-power increases indicate that while the formers were elicited after incorrect vs. correct actions in all groups, the latter were observed in on-condition but altered in off-condition PD. Therefore, different EEG error signatures may index the activity of distinct mechanisms, and error-related theta power is selectively modulated by dopamine depletion. Our findings may facilitate discovering dopamine-related biomarkers for error-monitoring dysfunctions that may have crucial theoretical and clinical implications.
Question Learning may occur through associative changes in the synaptic strength of neural connections that can be induced by coupling of activity of interconnected neurons with precise timing ...(spike-timing dependent plasticity, STDP). It is debated if this model can be applied in the context of large-scale cortical networks in humans. Methods We combined transcranial magnetic stimulation with concurrent electroencephalography to directly investigate if precise repeated activation of pre and post-synaptic large-scale cortical inputs produces STDP effects within the parietal-prefrontal network of 15 healthy volunteers. Results We found direct evidence for bidirectional STDP after effects over the DLPFC ruled by the PPC pre-synaptic inputs. Specifically, when the pre-synaptic input (PPC) precedes repeatedly the post-synaptic activation (DLPFC) by 10 ms a LTD-like effect of TMS-evoked activity is induced within the DLPFC. When the temporal order of the two stimulated areas is reverted, i.e. the pre-synaptic input (PPC) follows the post-synpatic input (DLPFC), we observed an LTP-like effect. Interestingly, such changes were accompained by PAS-depedendent modulations of the natural frequency of oscillation of the DLPFC, i.e. gamma activity. Conclusions We provide novel evidence that paired associative stimulation of posterior parietal cortex (PPC) and dorsolateral prefrontal cortex (DLPFC) induces bidirectional STDP effects in the post synaptic area (DLPFC) both in the time and in the time/frequency domain.
Background:
In multiple sclerosis (MS), the location of focal lesions does not always correlate with clinical symptoms, suggesting disconnection as a major pathophysiological mechanism. Resting-state ...(RS) functional magnetic resonance imaging (fMRI) is believed to reflect brain functional connectivity (FC) within specific neuronal networks.
Objective:
RS-fMRI was used to investigate changes in FC within two critical networks for the understanding of MS disabilities, namely, the sensory-motor network (SMN) and the default-mode network (DMN), respectively, implicated in sensory-motor and cognitive functions.
Methods:
Thirty-four relapsing–remitting (RR), 14 secondary progressive (SP) MS patients and 25 healthy controls underwent MRI at 3T, including conventional images, T1-weighted volumes, and RS-fMRI sequences. Independent component analysis (ICA) was employed to extract maps of the relevant RS networks for every participant. Group analyses were performed to assess changes in FC within the SMN and DMN in the two MS phenotypes.
Results:
Increased FC was found in both networks of MS patients. Interestingly, specific changes in either direction were observed also between RR and SP MS groups.
Conclusions:
FC changes seem to parallel patients’ clinical state and capability of compensating for the severity of clinical/cognitive disabilities.
Amyloid precursor protein (APP), ADAM 10, and beta-site-APP cleaving enzyme (BACE) alterations were evaluated in platelets of 31 patients with Alzheimer disease (AD) and 15 age-matched controls. A ...significant modification of these proteins and enzymes involved in the amyloid cascade was detected from the earliest clinically detectable disease stage. This observation suggests that AD is associated with an early metabolic derangement toward amyloidogenic pathways and supports the potential value of APP and secretase measurements for early diagnosis of AD.
Early Onset Alzheimer Disease (EOAD) and Late Onset Alzheimer Disease (LOAD) share the same pathological features and are considered the same disorder affecting people at different ages, under 65 ...years for EOAD, over 65 years for LOAD. Whether the different pathological burden could influence also synaptic plasticity mechanisms has never been addressed yet. The aim of our study is to investigate the neurophysiological characteristics of these patients through transcranial magnetic stimulation protocols, comparing with two control groups, respectively old healthy and young healthy age-matched subjects. To verify this hypothesis we evaluated a group of 22 sporadic EOAD and 33 LOAD for plasticity induction of LTP/LTD-like effects using respectively intermittent TBS (iTBS) or continuous TBS (cTBS). Central cholinergic activity was evaluated by means of short afferent inhibition (SAI) protocol. Patients, both EOAD and LOAD, showed an impairment of LTP mechanisms while healthy controls, showed a normal profile of cortical plasticity. SAI protocol results show a positive correlation between SAI dysfunction and aging, reflecting acetylcholine role in aging. The central cholinergic pathway seems to be affected more by age than by the disease process itself. LTP mechanisms are altered in AD patients despite the age, thus representing a reliable marker of disease.
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