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Objective The cortical silent period (CSP) following transcranial magnetic stimulation reflects GABAB-mediated inhibition in the primary motor cortex (M1) and could contribute to understand the pathophysiological substrates of epileptic conditions. Increased CSP duration has been reported in idiopathic generalized epilepsy (IGE) and in partial epilepsy (PE) involving the M1, although other studies yielded discordant findings. We used meta-analysis to systematically assess the consistency of CSP changes in untreated patients with epilepsies. Methods Databases were searched for controlled studies evaluating the CSP in drug-naive or drug-free patients with IGE or PE. For each study, the mean difference with 95% confidence intervals (CIs) between CSP duration obtained in patients and controls was calculated. The effect of motor threshold (MT) on the CSP duration has also been explored by meta-analysis and meta-regression. Results Fourteen studies (267 patients and 234 controls) were included. A significant mean difference (14.16 ms, 95% CI, 1.20, 27.11 ms) was found, with longer CSP in patients than in controls. The mean difference was still greater (18.05 ms) if only the 202 IGE patients were analyzed. No MT difference emerged between patients and controls. Meta-regression showed no relationship between MT and CSP duration. Conclusion Meta-analysis confirms CSP modifications in epilepsies, with enhancement of this cortical inhibitory measure at least in most IGE patients. This provides rationale for further investigations aiming to verify the hypotheses that increased CSP reflects compensatory neural phenomena counteracting transition from the interictal to ictal state and that CSP variability reflects the pathophysiological heterogeneity of epileptic syndromes.

Background Recent neuroimaging data support the hypothesis of a multisensory interplay at low-level sensory-specific cortex. Objective We used an on-line interference approach by rTMS to investigate the role of the left lateral occipital cortex (LOC) in audio–visual (AV) object recognition process. Methods Fifteen healthy volunteers performed a visual identification task of degraded pictures presented alone or simultaneously to coherent or non-coherent sounds. Focal 10-Hz rTMS at an intensity of 100% resting motor threshold was delivered simultaneously to the picture. Two blocks of 60 pictures were randomly displayed in two different experimental conditions: rTMS of the left LOC and over Cz. Results rTMS of the left LOC produced a worsening of the accuracy compared to rTMS over Cz specifically in the coherent AV condition. Conclusion These data support the view that audio–visual interaction effect may occur at early stage of recognition processing.

The stability of hand-held coil positioning with neuronavigated versus conventional transcranial magnetic stimulation (TMS) is still underinvestigated. Eleven operators naïve for neuronavigation were asked to position and maintain a figure-of-eight-shaped coil over a dipole probe placed within of a polystyrene reproduction of the human head and scalp, in correspondence of the right primary motor cortex. Ten monophasic magnetic pulses were delivered at 46% maximal stimulator output (MSO) in two different experimental conditions: (1) assisted by an optically tracked neuronavigational system; and (2) without neuronavigation. With neuronavigated stimulation, both standard deviation and coefficient of variation of the voltages induced in the dipole probe were significantly lower than without neuronavigation. Results were confirmed in four operators performing a longer-lasting experiment using 50 magnetic pulses in each condition, at an intensity of at 40% MSO. Findings show that optically tracked neuronavigation improves the stability of focal coil positioning.

Object identification is enabled through a distributed neural network but the relative contribution of the single components of this network is largely unknown. In the present study, we used online interference by repetitive transcranial magnetic stimulation (rTMS) to investigate the role of the dorso-lateral prefrontal cortex (DLPFC) in identifying semantically different stimuli presented as to make the decision process easy or difficult, according to the amount of sensory information available. Nineteen healthy volunteers performed an object identification task. Stimuli belonging to living and non-living categories were presented at different levels of spatial filtering following a coarse-to-fine order that gradually integrated spatial information. Six-pulse trains of 10-Hz rTMS were delivered at an intensity of 90% resting motor threshold simultaneously to the picture presentation. rTMS of either the left or right DLPFC produced a significant lengthening in the identification process of spatially filtered living stimuli, as shown by the increase in the reaction time, but not of non-filtered living stimuli or of non-living objects. rTMS over the vertex did not interfere with the identification task. These data indicate that DLPFC role in the network underlying object recognition is more crucial when this neural process is challenged by the level of sensory information available to the observer. Specificity of this effect for living objects is discussed taking into account the crucial role of DLPFC in recruitment of cognitive resources for accomplishing perceptual decision-making.