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Objective: To study electroencephalography–electromyography (EEG–EMG) relationships in patients with different forms of progressive myoclonic epilepsies (PME).Methods: EEG–EMG auto-spectra, coherence and phase functions were estimated by means of bivariate and time varying autoregressive (AR) models in 15 patients: 8 with Unverricht–Lundborg, 4 with Lafora body disease, and 3 with sialidosis.Results: The coherence spectra of the EMG epochs including action myoclonus and contralateral frontocentral EEG derivations showed a main beta peak (average coherence: 0.60–0.79) in all patients, regardless of the type of PME. The time lag from cortex to muscle was 13.0–21.3 ms. Significantly, coherent gamma activity was consistently found only in the 3 patients with sialidosis; the most heterogeneous results were obtained in the patients with Lafora disease, who showed a more complex coherence profile. Periods of normal muscle contractions, which could be recorded in patients with Unverricht–Lundborg PME, were characterised by the presence of an EEG–EMG beta coherence peak on the same frequency as in the case of action myoclonus, but with a lower coherence value.Conclusions: AR models were capable of describing EEG–EMG relationships in patients with PME, and indicated that coherent cortical and EMG beta oscillations are crucially involved in the generation of myoclonus. Moreover, they could detect the uneven spectral profiles characterising the different forms of PME. [Copyright &y& Elsevier]

Abstract: Objective: To evaluate the relationship between sensory hyperexcitability as revealed by giant SEPs and the SEP recovery function (SEP-R) in a series of patient with progressive myoclonic epilepsy of Unverricht–Lundborg type, identified as epilepsy, progressive myoclonic 1A (EPM1A), MIM #254800. Methods: We evaluated SEPs by applying median nerve stimuli and SEP-R using paired stimuli at inter-stimulus intervals (ISIs) of between 20 and 600ms in 25 patients and 20 controls. The SEPs were considered “giant” if the N20P25 and P25N33 amplitudes exceeded normal mean values by +3SD. Results: During the paired-stimulus protocol, the SEPs elicited by the second stimulus (S2) were detectable at all ISIs but consistently suppressed in the 13 patients with giant SEPs reflecting a significantly delayed SEP-R. Maximal suppression roughly corresponded to the plateau of a broad middle latency (>100ms) wave pertaining to the S1 response. Conclusions: The cortical processing dysfunction generating giant SEPs in EPM1A patients consistently combines with a long-lasting suppression of hyperexcitability that leads to a delayed giant SEP-R without obstructing the response to incoming stimuli. Significance: The delayed SEP-R is not due to true inhibition but the suppression of aberrant hyper-synchronisation sustaining giant SEPs. A broad middle latency SEP component adds a significantly suppressive effect. This suggests that cortico-subcortical circuitries contribute to both the gigantism and the delayed SEP-R. [Copyright &y& Elsevier]

Abstract: Previous studies have demonstrated that the event-related potential (ERP) evoked by a note shows substantial differences depending on whether the note is part of a melodic context or presented in an unstructured repetition. In particular, the N2 component has been found to have considerably increased latency and a more frontal topography for notes presented in a melody. An open question is whether such effect is related to the ‘meaningfulness’ of a note sequence, that is due to the formation of abstract melodic entities, rather than more simply an indicator of cognitive load associated with processing a structurally-complex sequence as opposed to an unstructured repetition. In this study, we addressed this issue by recording ERPs from 10 healthy non-musicians listening to eight one-part unfamiliar tonal melodies and eight sequences of random notes. The two stimuli were matched for distribution of pitch, intervals and note duration as well as for entropy of the time-series of pitch and duration. While tonal melodies were rated more meaningful (p <0.001) and pleasant (p <0.001) by all participants, no effects were found for the N2 component amplitude (p ≥0.8) and latency (p =0.2). Combined with previous findings, this indicates that the N2 evoked by each individual note responds to the structural complexity of the note sequence, i.e., to the presence of pitch and duration changes, but not to higher-level processing related to the formation of abstract melodic entities. In contrast, we found that the amplitude of the P2 component was marginally (p =0.04) elevated for random notes as compared to tonal melodies. This may be related to attentional modulation, or more specifically to associative components of auditory processing. [ABSTRACT FROM AUTHOR]

Abstract: Objective: To evaluate the EEG recorded in photosensitive idiopathic generalised epilepsy (IGE) patients at rest and during 14Hz IPS, frequency capable of inducing photoparoxysmal responses (PPRs). Methods: Power spectrum density and coherence profiles were estimated using a block autoregressive parametric model (AR) in 28 patients and 22 controls. Results: At rest, the intra- and inter-hemispheric coherence spectra showed a significantly larger number of coherence peaks in the gamma band in patients with respect to controls. During intermittent photic stimulation (IPS), coherent gamma activity is mainly presented as IPS frequency harmonics; moreover, the patients’ mean coherence values significantly increased. In six patients re-evaluated with IPS after putting on glasses with Z1 blue lens (which counteracts PPR) the spectral and coherence profiles tended to return to the resting ones. Conclusions: Patients are endowed with inherited EEG hyper-synchrony as shown by the large number of coherence peaks detectable under resting conditions, whereas IPS enhances intra- and inter-hemispheric mean coherence values in the gamma band. The persistence of alpha activity peaks during IPS in most controls but not in patients suggests that the alpha generating network plays a significant role in counteracting PPR. Significance: Both gamma and alpha EEG generators are involved in the PPR generation and in the widespread synchronisation characterising the IGE-associated photosensitivity. [Copyright &y& Elsevier]

Abstract: Objective: To characterise flash visual evoked potentials (FVEPs) in 20 patients with Creutzfeldt–Jacob disease (CJD), and assess the relationships between spontaneous EEG patterns and the responses to individual stimuli. Methods: We analysed the shape and time course of periodic sharp wave complexes (PSWCs) and responses to 1Hz flashes. In nine patients, we applied an algorithm based on an autoregressive model with exogenous input (ARX) to estimate responses to individual random flashes and their interaction with PSWCs. Results: The FVEPs included P1 and N1 components in all patients, and the P2 peak in 18. Eight patients showed giant FVEPs (N1-P2>60 V), all of whom had an MM polymorphism in codon 129 of the prion protein gene; in seven cases, the presence of giant FVEPs correlated with a prominent and almost continuous periodic EEG pattern. Giant N1-P2 abnormally spread on the anterior scalp regions, and had a different waveform distribution from that of the PSWCs. In five patients with a normal or slightly enlarged average N1-P2 amplitude, single sweep (ARX) analysis revealed a period of relative refractoriness following individual PSWCs. In four patients with ‘giant’ FVEPs, the individual responses occurred regardless of the interval between the stimulus and previous PSWC, but their amplitude had an inverse relationship with the interval length. Conclusions: Giant responses to flash stimuli are a common finding in CJD patients (40% of our cases). Single sweep ARX analysis showed that PSWCs were followed by a period of partial refractoriness, which prevented most of the individual responses to flashes, but not giant FVEPs. The association between prominent spontaneous paroxysms and giant FVEPs suggests that both are due to a common hyperexcitable change favouring neuronal synchronisation. Significance: Our data contribute to clarifying the debated problem of the occurrence of giant FVEPs in CJD and their relationships with the spontaneous periodic EEG pattern. [Copyright &y& Elsevier]