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Objective Changes in cerebral cortex excitability have been demonstrated after a stroke and are considered relevant for recovery. Repetitive transcranial magnetic stimulation (rTMS) of the brain can modulate cerebral cortex excitability and, when rTMS is given as theta burst stimulation (TBS), LTP- or LTD-like changes can be induced. The aim of present study was to evaluate the effects of TBS on cortical excitability in acute stroke. Methods In 12 acute stroke patients, we explored the effects of facilitatory TBS of the affected hemisphere and of inhibitory TBS of the unaffected hemisphere on cortical excitability to single-pulse transcranial magnetic stimulation (TMS) on both sides. The effects produced by TBS in patients were compared with those observed in a control group of age-matched healthy individuals. Results In patients, both the facilitatory TBS of the affected motor cortex and the inhibitory TBS of the unaffected motor cortex produced a significant increase of the amplitude of MEPs evoked by stimulation of the affected hemisphere. The effects observed in patients were comparable to those observed in controls. Conclusions Facilitatory TBS over the stroke hemisphere and inhibitory TBS over the intact hemisphere in acute phase enhance the excitability of the lesioned motor cortex. Significance TBS might be useful to promote cortical plasticity in stroke patients.

Objective The increase of elderly population prompted growing research for the understanding of cerebral phenomena sustaining learning abilities, with inclusion of long-term potentiation (LTP)-like plasticity phenomena. Aim of the present study was to characterize LTP-like plasticity dependence on age and gender. Methods A LTP-like primary motor cortex plasticity inducing a potentiation of the motor evoked potential (MEP) to focal transcranial magnetic stimulation as a consequence of a paired associative stimulation (PAS) was induced in a 50 healthy subject cohort, equally distributed for gender and age groups (25 young subjects, mean age ± SD = 29.8 ± 4.5 years; elderly 61.1 ± 4.1 years). Results Resting motor thresholds’ excitability level increased in the elderly group, the basal MEP did not depend on gender or age. The PAS-induced primary motor cortex (M1) plastic excitability modulation was similar in young females and males, while it decreased with age in females only. Conclusions A reduction of the PAS-induced M1 plasticity in females after menopause was documented, possibly due to an impairment of intracortical excitatory network activity. Significance A LTP-like plasticity dependence on age was found in female only, suggesting caution in interpreting behavioural studies on learning abilities in dependence on age.

Purpose Transcranial electric stimulations (tES) with amplitude-modulated currents are promising tools to enhance neuromodulation effects. It is essential to select the correct cortical targets and inhibitory/excitatory protocols to reverse changes in specific networks. We aimed at assessing the dependence of cortical excitability changes on the current amplitude of 20 Hz transcranial alternating current stimulation (tACS) over the bilateral primary motor cortex. Methods We chose two amplitude ranges of the stimulations, around 25 μ A/cm2 and 63 μ A/cm2 from peak to peak, with three values (at steps of about 2.5%) around each, to generate, respectively, inhibitory and excitatory effects of the primary motor cortex. We checked such changes online through transcranial magnetic stimulation (TMS)-induced motor evoked potentials (MEPs). Results Cortical excitability changes depended upon current density (p=.001). Low current densities decreased MEP amplitudes (inhibition) while high current densities increased them (excitation). Conclusions tACS targeting bilateral homologous cortical areas can induce online inhibition or excitation as a function of the current density.

Transcranial magnetic stimulation (TMS) has been employed in following up a population of 20 stroke patients in a post-acute, apparently stabilized stage. Neurophysiological and clinical data were recorded in 5 different recording sessions, from the beginning of a neuro-rehabilitation treatment (T0, at about 5 weeks from the ictal event.), followed up for about 4 months (T4), with the purpose to study any modification of the cortical motor output in the course of a neuro-rehabilitation treatment.Motor evoked potentials (MEPs) were simultaneously recorded from 10 muscles of both upper limbs (affected and not-affected); meanwhile, clinical and functional scores were gathered. Spinal responsiveness was investigated via H-reflex and F-wave recordings.We describe a pattern of improving changes still taking place four months after the stroke, even if the maximal amelioration burden was concentrated between T0 and T1 and T1 and T2 recording sessions (T0/admission to T2/42 days from T0=about 80 days from stroke occurrence). In particular, the excitability threshold (ETh) was progressively decreasing in the affected hemisphere (AH; P0.001 between T0 and T4), while MEPs amplitude and latency tended toward normality, more in the resting state than during voluntary contraction. Slopes of neurophysiological and clinical data evolution were taken and trends of amelioration described.These findings suggest that rearrangements of motor cortical neural circuitries are still operating after several months from an acute vascular monohemispheric insult, coupled with a clinical improvement in disability and neurological scores. The steepest part of the slopes were evident in the first 80 days, suggesting that this period is the one in which plastic changes of cortical motor areas are mainly active.

Several experimental studies have shown that, nevertheless motor symptoms are late events in the natural history of Alzheimer’s disease (AD), neuropathological progression in the motor cortex parallels that in other brain cortices generally considered more specific targets of the aggression. In the last years we have clearly demonstrated that motor cortex excitability is enhanced in AD since the early stages of the disease and this is probably related to its severity and progression. To further investigate, for the first time without peripheral or attentional confounding effects, the neurophysiological hallmarks of motor cortex functionality in AD we used here transcranial magnetic stimulation (TMS) combined with electroencephalography (EEG). We then demonstrated that in mild AD, despite the lack of clinical manifestations, the sensorimotor system is strongly hyper-excitable and its connectivity is deeply rearranged with the recruitment of additional neural sources, the activation of reverberant circuits and their integration in the distributed excitatory network subtending sensorimotor functions.

Introduction Recent evidences suggested that imperceptible transcranial alternating current stimulation (tACS) resonates in a frequency-specific manner with the endogenous cortical oscillatory activity. Such a phenomenon causes behavioral consequences on perceptual, motor and cognitive tasks. In the motor system, 20 Hz tACS in beta range, coincident with the idling rhythm of the motor cortex at rest, increased corticospinal output. Objectives To assess how tACS modulates corticospinal excitability in a differential frequency dependent fashion during motor imagery and rest, we delivered transcranial oscillatory frequencies on the primary motor cortex ranging from theta to gamma band. Thus, we aimed to verify whether facilitatory tACS effects persisted during motor imagery, a cognitive task which desynchronizes the rolandic 20 Hz rhythm of quiescent motor areas, thereby becoming theoretically less susceptible to resonance effects of beta stimulation. Materials and methods Eighteen fully healthy right-handed volunteers (8 females, 10 males; mean age 32.2 ± 7.05 years) underwent fourteen different randomized conditions. Both for motor imagery and for resting condition, a “basal 1” session (without tACS), tACS on the left motor cortex at 5 Hz ( θ band), 10 Hz ( α band), 20 Hz ( β band), 40 Hz ( γ band), as well as 20 Hz on the right parietal cortex (as a control for unspecific effects on cortical excitability) and a “basal 2” session (again without tACS), were run. Each session of stimulation lasted 1.5–2 min. TMS was applied over the sponge electrode used for tACS overlying the left M1. Corticospinal excitability changes during stimulation at different frequencies were indexed by motor evoked potentials (MEPs) through navigated Transcranial Magnetic Stimulation (TMS) of the primary motor cortex. MEPs were recorded from the right First Dorsal Interosseus. For motor imagery tasks, subjects were requested to visually imagine a thumb-index finger pinch grip with their right hand. Each TMS pulse was delivered 1–2 s after the initiation of the motor imagery task as well as for rest condition. Results A General Estimation Equation (factors motor imagery and rest x frequency conditions) showed that the maximal increase of corticospinal excitability took place when tACS was applied at 5 Hz and an additional slighter effect of 10 Hz tACS with subjects engaged in a motor imagery task. On the other hand, tACS at 20 Hz confirmed the maximal increase of corticospinal excitability with subjects at rest. Conclusions On one hand results confirmed the frequency-dependence effects of tACS. On the other hand a state-dependent effect of tACS emerged. The MEPs increase in theta range stimulation during motor imagery may reflect reinforcement of working memory processes required to mentally elaborate and “execute” the task. We infer that tACS induces an entrainment effect by dragging the endogenous oscillatory activity to the one induced by stimulation. This indicates that human brain motor processes might be driven and promoted by application of external sinusoidal electrical forces. Download high-res image (87KB) Download full-size image

S5.3 Prognostic value of contralesional delta band EEG activity in acute stroke G. Assenza1, F. Zappasodi2, P. Pasqualetti3, S. Assenza4, M. Ercolani5, L. Fraioli6, C. Gaudino7, F. Passarelli8, F. Tibuzzi9, F. Vernieri1, P.M. Rossini1, F. Tecchio10 1Neurologia Clinica, Universita Campus Biomedico, Rome, Italy, 2Department of Clinical Sciences and Bioimaging, G. D’Annunzio University, Chieti-Pescara, Italy, 3Medical Statistics & Information Technology, Fatebenefratelli Association for Research, Rome, Italy, 4Casa di Cura San Raffaele Cassino, Cassino, Italy, 5AFaR, Department of Neuroscience, Hosp. Fatebenefratelli, Isola Tiberina, Rome, Italy, 6Casa di Cura San Raffaele Cassino, Rome, Italy, 7Radiologia e Diagnostica per immagini, Universita Campus Biomedico, Rome, Italy, 8Dipartimento di Neuroscienze Ospedale Fatefenefratelli, Isola Tiberina, Rome, Italy, 9Dipartimento di Neuroscienze Ospedale Fatebenefratelli Isola Tiberina, Rome, Italy, 10LET’S Laboratory of Electrophysiology for Translational neuroScience Unita MEG Osp. FBF Isola tiberina, Rome, Italy