Noémie Ligot

The pace of prosodic phrasing couples the listener's cortex to the reader's voice.

We studied online coupling between a readers voice and a listeners cortical activity using a novel, ecologically valid continuous listening paradigm. Whole‐scalp magnetoencephalographic (MEG) signals were recorded from 10 right‐handed, native French‐speaking listeners in four conditions: a female (Exp1f) and a male (Exp1m) reading the same text in French; a male reading a text in Finnish (Exp 2), a language incomprehensible for the subjects, and a male humming Exp1 text (Exp 3). The fundamental frequency (f0) of the readers voice was recorded with an accelerometer attached to the throat, and coherence was computed between f0 time‐course and listeners MEG. Similar levels of right‐hemisphere‐predominant coherence were found at ˜0.5 Hz in Exps 1–3. Dynamic imaging of coherent sources revealed that the most coherent brain regions were located in the right posterior superior temporal sulcus (pSTS) and posterior superior temporal gyrus (pSTG) in Exps 1–2 and in the right supratemporal auditory cortex in Exp 3. Comparison between speech rhythm and phrasing suggested a connection of the observed coherence to pauses at the sentence level both in the spoken and hummed text. These results demonstrate significant coupling at ∼0.5 Hz between readers voice and listeners cortical signals during listening to natural continuous voice. The observed coupling suggests that voice envelope fluctuations, due to prosodic rhythmicity at the phrasal and sentence levels, are reflected in the listeners cortex as rhythmicity of about 2‐s cycles. The predominance of the coherence in the right pSTS and pSTG suggests hemispherical asymmetry in processing of speech sounds at subsentence time scales. Hum Brain Mapp, 2013.

External globus pallidus stimulation modulates brain connectivity in Huntington's disease.

Positron emission tomography with O-15-labeled water was used to study at rest the neurophysiological effects of bilateral external globus pallidus (GPe) deep brain stimulation in patients with Huntingtons disease (HD). Five patients were compared with a control group in the on and off states of the stimulator. External globus pallidus stimulation decreased neuronal activity and modulated cerebral connectivity within the basal ganglia-thalamocortical circuitry, the sensorimotor, and the default-mode networks. These data indicate that GPe stimulation modulates functional integration in HD patients in accordance with the basal ganglia-thalamocortical circuit model.

Impact of focal interictal epileptiform discharges on behaviour and cognition in children

It is hypothesised that focal interictal epileptiform discharges (IED) may exert a deleterious effect on behaviour and cognition in children. This hypothesis is supported by the abnormally high prevalence of IED in several developmental disorders, like specific language impairment, and of cognitive and behavioural deficits in epileptic children after excluding confounding factors such as underlying structural brain lesions, drug effects, or the occurrence of frequent or prolonged epileptic seizures. Neurophysiological and functional neuroimaging evidence suggests that IED may impact cognition through either transient effects on brain processing mechanisms, or through more long-lasting effects leading to prolonged inhibition of brain areas distant from but connected with the epileptic focus (i.e. remote inhibition effect). Sustained IED may also impair sleep-related learning consolidation processes. Nowadays, the benefits of anti-epileptic treatment aimed at reducing IED are not established except in specific situations like epileptic encephalopathies with continuous spike and waves during slow-wave sleep. Well-designed pharmacological studies are still necessary to address this issue.

Metabolic evidence for episodic memory plasticity in the nonepileptic temporal lobe of patients with mesial temporal epilepsy.

Purpose:  Metabolic changes have been described in the nonepileptic temporal lobe of patients with unilateral mesiotemporal lobe epilepsy (MTLE) associated with hippocampal sclerosis (HS). To better understand the functional correlate of this metabolic finding, we have sought to characterize brain regions in patients with MTLE that show correlation between unilateral episodic memory performances, as assessed by intracarotid amobarbital test (IAT), and interictal regional cerebral metabolism measured by [18F]‐fluorodeoxyglucose positron emission tomography (FDG‐PET).

Default mode network hypometabolism in epileptic encephalopathies with CSWS.

Previous studies investigating cerebral metabolic changes associated with continuous spike-waves during sleep (CSWS) compared the metabolism of children with CSWS with that of healthy adults, precluding any assessment in brain areas showing physiologic age-related metabolic changes. Here, we investigated the metabolic and connectivity changes characterizing the acute phase of CSWS activity by comparing awake brain metabolism of children with CSWS with that of pediatric pseudo-controls. Positron emission tomography using [18F]-fluorodeoxyglucose (FDG-PET) was performed in 17 awake children with cryptogenic CSWS (5 girls, age: 5-11 years). Voxel-based analyses identified significant metabolic changes in CSWS patients compared with 18 pediatric pseudo-controls (12 girls, age: 6-11 years, non-CSWS focal cryptogenic epilepsy with normal FDG-PET). CSWS-induced changes in the contribution of brain areas displaying metabolic changes to the level of metabolic activity in other brain areas were investigated using pathophysiological interaction. Hypermetabolism in perisylvian regions bilaterally and hypometabolism in lateral and mesial prefrontal cortex, precuneus, posterior cingulate cortex and parahippocampal gyri characterized the acute phase of CSWS (p<0.05 FWE). No change in thalamic metabolism was disclosed. Altered functional connectivity was found between hyper- and hypometabolic regions in CSWS patients compared with pediatric pseudo-controls. This study demonstrates hypometabolism in key nodes of the default mode network (DMN) in awake patients with CSWS, in relation with a possible phenomenon of sustained remote inhibition from the epileptic foci. This hypometabolism might account for some of the acquired cognitive or behavioral features of CSWS epileptic encephalopathies. This study failed to find any evidence of thalamic metabolic changes, which supports the primary involvement of the cortex in CSWS genesis.

Transient Neurologic Deficits: Can Transient Ischemic Attacks Be Discrimated from Migraine Aura without Headache?

BACKGROUND Transient neurologic deficits (TNDs) are often considered first to be transient ischemic attacks (TIAs) but TND with normal brain imaging is also characteristic of other prevalent conditions like migraine aura leading to potential confusion. We aimed to determine if migraine aura with headache (MA) and migraine aura without headache (MAWH) can be distinguished from TIA on clinical or paraclinical ground using validated international criteria. METHODS Clinical and paraclinical data from 32 patients with TIA were compared with 32 patients with MAWH and 32 with MA. Participants underwent a thorough evaluation including standardized clinical examination, laboratory testing, magnetic resonance imaging of the brain, cardiovascular work-up, and electroencephalogram. RESULTS Patient with TIA were significantly older (65.41 ± 16.93 years) than patients with MAWH (50.41 ± 19.69, P = .002) or MA (40.56 ± 11.72, P = .00001), and were mostly male (male:female = .82) compared with the 2 other groups. History of stroke, high blood pressure, and dyslipidemia were significantly more frequent in patients with TIA. Visual deficits occurred in 63% of patients with MAWH, 41% for patients with MA, and 10% for patients with TIA. In patients with TIA, the TND was inaugural in 94% of cases, conversely to MAWH and MA in which TND was inaugural in only 19% and 38%, respectively (P ≤ .0001). CONCLUSIONS Despite some sociodemographic, clinical, and paraclinical differences in the presentation of these TND, there is no feature accurately distinguishing between TIA and TND associated with migrainous phenomena when validated actual criteria are used, leading to probable confusion in most studies. There is a need to develop reliable criteria and/or tests for this purpose.

No evidence of thalamic metabolic abnormality associated with continuous spike-and-wave during sleep

Lombardia, Italy; Emory+Children’s Pediatric Research Center, Atlanta, Georgia, U.S.A.; Children’s Memorial Hospital, Chicago, Illinois, U.S.A.; Ann and Robert H. Lurie Children’s Hospital of Chicago, Chicago, Illinois, U.S.A.; Hospital de Santa Maria, Lisbon, Portugal; University of Colorado Anschutz Medical Campus, Aurora, Colorado, U.S.A.; The Children’s Hospital, Aurora, Colorado, U.S.A.; Texas Children’s Hospital, Houston, Texas, U.S.A.; Baylor College of Medicine, Houston, Texas, U.S.A.; University of Oklahoma College of Medicine, Oklahoma City, Oklahoma, U.S.A.; Boston Children’s Hospital, Boston, Massachusetts, U.S.A.; Harvard Medical School, Boston, Massachusetts, U.S.A.; Washington University School of Medicine, St. Louis, Missouri,U.S.A.; Cleveland Clinic, Cleveland, Ohio, U.S.A.; The Royal Children’s Hospital Melbourne, Parkville, Victoria, Australia; Bruce Lefroy Centre for Genetic Health Research, Murdoch Children’s Research Institute, Parkville, Victoria, Australia; University of Melbourne, Melbourne, Victoria, Australia; and Medical College of Georgia at Augusta University, Augusta, Georgia, U.S.A.

Occipital transcranial magnetic stimulation discriminates transient neurological symptoms of vascular origin from migraine aura without headache

OBJECTIVES The diagnosis of transient neurological attacks (TNA) relies on medical history. Transient ischemic attack is often considered until proven otherwise, because of lack of objective paraclinical tools that can help discriminate TIA from differential diagnoses such as migraine aura. This may lead to needless and potentially harmful stroke secondary prevention in many cases. This study aimed at determining the yield of occipital transcranial magnetic stimulation (oTMS) in discriminating TNA of vascular origin from migraine aura without headache (MAWH). METHODS Ten patients with acute TNA of vascular origin and ten patients with migraine aura without headache (MAWH), without prior history of migrainous headache, were prospectively included. TNA of vascular origin were considered for individuals presenting unilateral focal symptoms with full resolution within 24hours and positive diffusion weighted imaging (DWI+). For individuals with MAWH, diagnostic criteria were either ICHD-III beta or Fischer criteria for a first episode of MAWH. All participants underwent one session of oTMS. Induction and threshold of phosphene induction were recorded. RESULTS In TNA of vascular origin, MRI disclosed cortical lesions in nine and one sub-cortical lesion. Phosphenes were induced in 9/10 subjects with MAWH with a mean threshold of 66% of the maximal intensity, whereas oTMS induced phosphenes in only one subject with TNA of vascular origin at a threshold of 85%. CONCLUSIONS In this pilot study, oTMS was found to be an effective tool to discriminate between MAWH and transient neurological symptoms of vascular origin.