Hannes O. Tiedt

Sex-differences of face coding: evidence from larger right hemispheric M170 in men and dipole source modelling.

The processing of faces relies on a specialized neural system comprising bilateral cortical structures with a dominance of the right hemisphere. However, due to inconsistencies of earlier findings as well as more recent results such functional lateralization has become a topic of discussion. In particular, studies employing behavioural tasks and electrophysiological methods indicate a dominance of the right hemisphere during face perception only in men whereas women exhibit symmetric and bilateral face processing. The aim of this study was to further investigate such sex differences in hemispheric processing of personally familiar and opposite-sex faces using whole-head magnetoencephalography (MEG). We found a right-lateralized M170-component in occipito-temporal sensor clusters in men as opposed to a bilateral response in women. Furthermore, the same pattern was obtained in performing dipole localization and determining dipole strength in the M170-timewindow. These results suggest asymmetric involvement of face-responsive neural structures in men and allow to ascribe this asymmetry to the fusiform gyrus. This specifies findings from previous investigations employing event-related potentials (ERP) and LORETA reconstruction methods yielding rather extended bilateral activations showing left asymmetry in women and right lateralization in men. We discuss our finding of an asymmetric fusiform activation pattern in men in terms of holistic face processing during face evaluation and sex differences with regard to visual strategies in general and interest for opposite faces in special. Taken together the pattern of hemispheric specialization observed here yields new insights into sex differences in face perception and entails further questions about interactions between biological sex, psychological gender and influences that might be stimulus-driven or task dependent.

Persistent hiccups as sole manifestation of right cortical infarction without apparent brainstem lesion

A 71-year-old man complained of persistent hiccups with a sudden onset five days prior to admission. He had a history of hypertension, hyperlipidemia, peripheral arterial disease and minor stroke seven years before. Gastroscopy and chest radiography had been inconclusive; magnetic resonance imaging (MRI) was conducted showing an infarction of the right frontal cortex extending to the anterior insular cortex without any apparent lesions in the brain stem (Fig. 1). Thorough clinical examination after hospitalization on our stroke unit revealed no other neurological symptoms apart from irregular bouts of hiccups with variable frequency. Extensive evaluation of aetiology did not show ipsilateral carotid stenosis, any source of cardiogenic embolism or other (rare) causes; therefore, aetiology was undetermined. EEG-studies showed abnormal activity with slower frequencies within theta-range in right temporal electrodes without epileptic discharges. Symptomatic treatment of hiccups with gabapentin administered at a dosage of 900 mg/day lead to resolution of symptoms within two days, in a follow-up interview the patient reported that even after cessation of gabapentin there was no recurrence of hiccups. Hiccups consist of an inspiratory movement of the diaphragm and intercostal muscles followed by laryngeal closure and usually last for minutes to sometimes hours. However, as in our patient, persistent hiccups lasting longer than 24 h can indicate diseases of the central nervous system. Persistent hiccups are frequently observed beside other brainstem symptoms in patients suffering from infarction of the medulla oblongata [1]. In particular, a hiccup-like motor pattern can be evoked in cats by electrical stimulation applied to the medullary reticular formation close to the nucleus ambiguus containing vagal motoneurons projecting to laryngeal muscles [2]. Autonomic circuits in the lower brain stem are thought to be modulated by a network of cortical structures such as anterior insula, medial prefrontal and cingulate cortex [3]. But there are only a few records of patients experiencing persistent hiccups due to supratentorial lesions involving temporal lobes [4–7] or (left) posterior insula [8]; to our knowledge there is no report of a patient presenting with the exclusive symptom of persistent hiccups following a rather confined lesion of the right anterior insular cortex as seen in our patient. Although the functional anatomy of the insular cortex is still somewhat elusive [9], investigations employing electrocortical stimulation beginning with the well-known experiments of Penfield and Faulk [10] consistently report a topographic organization within the insular cortex with viscerosensitive and visceromotor responses evoked by anterior insular stimulation suggesting a cortical visceral network comprising the anterior insular cortex extending to temporomesial structures [11]. Furthermore, patients suffering stroke including right insular cortex more often develop cardiovascular complications such as arrhythmia and myocardial infarction [12]. It has been suggested that such vegetative complications are caused by dysregulation of sympathoadrenergic functions in the sense of a disinhibition of subcortical autonomic centres [13]. In this view, discontinuation of cortical H. O. Tiedt (&) R. Wenzel Department of Neurology, Charité-Universitätsmedizin Berlin, Campus Benjamin Franklin (CBF), Hindenburgdamm 30, 12203 Berlin, Germany e-mail: hannes.tiedt@charite.de

Subcortical roles in lexical task processing: Inferences from thalamic and subthalamic event-related potentials.

Subcortical functions for language capacities are poorly defined, but may be investigated in the context of deep brain stimulation. Here, we studied event‐related potentials recorded from electrodes in the subthalamic nucleus (STN) and the thalamic ventral intermediate nucleus (VIM) together with surface‐EEG. Participants completed a lexical decision task (LDT), which required the differentiation of acoustically presented words from pseudo‐words by button press. Target stimuli were preceded by prime‐words. In recordings from VIM, a slow potential shift apparent at the lower electrode contacts persisted during target stimulus presentation (equally for words and pseudo‐words). In contrast, recordings from STN electrodes showed a short local activation on prime‐words but not target‐stimuli. In both depth‐recording regions, further components related to contralateral motor responses to target words were evident. On scalp level, mid‐central activations on (pseudo)lexical stimuli were obtained, in line with the expression of N400 potentials. The prolonged activity recorded from VIM, exclusively accompanying the relevant LDT phase, is in line with the idea of thalamic “selective engagement” for supporting the realization of the behavioral focus demanded by the task. In contrast, the phasic prime related activity rather indicates “procedural” STN functions, for example, for trial sequencing or readiness inhibition of prepared target reactions. Hum Brain Mapp 38:370–383, 2017.

Theory of mind performance in Parkinson’s disease is associated with motor and cognitive functions, but not with symptom lateralization

Abstract Next to the typical motor signs, Parkinson’s disease (PD) goes along with neuropsychiatric symptoms, amongst others affecting social cognition. Particularly, Theory of Mind (ToM) impairments have mostly been associated with right hemispherical brain dysfunction, so that it might prevail in patients with left dominant PD. Fourty-four PD patients, twenty-four with left and twenty with right dominant motor symptoms, engaged in the Reading the Mind in the Eyes (RME) and the Faux Pas Detection Test (FPD) to assess affective and cognitive ToM. The results were correlated with performance in further cognitive tests, and analyzed with respect to associations with the side of motor symptom dominance and severity of motor symptoms. No association of ToM performance with right hemispheric dysfunction was found. RME results were inversely correlated with motor symptom severity, while FPD performance was found to correlate with the performance in verbal fluency tasks and the overall cognitive evaluation. Affective ToM was found associated with motor symptom severity and cognitive ToM predominantly with executive function, but no effect of PD lateralization on this was identified. The results suggest that deficits in social cognition occur as a sequel of the general corticobasal pathology in PD, rather than as a result of hemisphere-specific dysfunction.

Thalamic deep brain stimulation decelerates automatic lexical activation.

Background Deep Brain Stimulation (DBS) of the thalamic ventral intermediate nucleus (VIM) is a therapeutic option for patients with essential tremor. Despite a generally low risk of side effects, declines in verbal fluency (VF) have previously been reported. Objectives We aimed to specify effects of VIM‐DBS on major cognitive operations needed for VF task performance, represented by clusters and switches. Clusters are word production spurts, thought to arise from automatic activation of associated information pertaining to a given lexical field. Switches are slow word‐to‐word transitions, presumed to indicate controlled operations for stepping from one lexical field to another. Patients & methods Thirteen essential tremor patients with VIM‐DBS performed verbal fluency tasks in their VIM‐DBS ON and OFF conditions. Clusters and switches were formally defined by mathematical criteria. All results were compared to those of fifteen healthy control subjects, and significant OFF‐ON‐change scores were correlated to stimulation parameters. Results Patients produced fewer words than healthy controls. DBS ON compared to DBS OFF aggravated this deficit by prolonging the intervals between words within clusters, whereas switches remained unaffected. This stimulation effect correlated with more anterior electrode positions. Conclusion VIM‐DBS seems to influence word output dynamics during verbal fluency tasks on the level of word clustering. This suggests a perturbation of automatic lexical co‐activation by thalamic stimulation, particularly if delivered relatively anteriorly. The findings are discussed in the context of the hypothesized role of the thalamus in lexical processing. HighlightsVerbal fluency output was reduced in patients with thalamic deep brain stimulation.Active vs. inactive stimulation prolonged pauses within lexical clusters.The effect increased with more rostral stimulation in the target area.

Phenotypic Variability in Autosomal Dominant Familial Alzheimer Disease due to the S170F Mutation of Presenilin-1

Background: In rare cases, patients with Alzheimer disease (AD) present at an early age and with a family history suggestive of an autosomal dominant mode of inheritance. Mutations of the presenilin-1 (PSEN1) gene are the most common causes of dementia in these patients. Early-onset and particularly familial AD patients frequently present with variable non-amnestic cognitive symptoms such as visual, language or behavioural changes as well as non-cognitive, e.g. motor, symptoms. Objective: To investigate the phenotypic variability in carriers of the PSEN1 S170F mutation. Methods: We report a family with 4 patients carrying the S170F mutation of whom 2 underwent detailed clinical examinations. We discuss our current findings in the context of previously reported S170F cases. Results: The clinical phenotype was consistent regarding initial memory impairment and early onset in the late twenties found in all S170F patients. There were frequent non-amnestic cognitive changes and, at early stages of the disease, indications of a more pronounced disturbance of visuospatial abilities as compared to face and object recognition. Non-cognitive symptoms most often included myoclonus and cerebellar ataxia. A review of the available case reports indicates some phenotypic variability associated with the S170F mutation including different constellations of symptoms such as parkinsonism and delusions. Conclusion: The variable clinical findings associated with the S170F mutation highlight the relevance of atypical phenotypes in the context of research and under a clinical perspective. CSF sampling and detection of Aβ species may be essential to indicate AD pathology in unclear cases presenting with cognitive and motor symptoms at a younger age.