Hartwig R. Siebner

Assessment of pedophilia using hemodynamic brain response to sexual stimuli.

CONTEXTnAccurately assessing sexual preference is important in the treatment of child sex offenders. Phallometry is the standard method to identify sexual preference; however, this measure has been criticized for its intrusiveness and limited reliability.nnnOBJECTIVEnTo evaluate whether spatial response pattern to sexual stimuli as revealed by a change in the blood oxygen level-dependent signal facilitates the identification of pedophiles.nnnDESIGNnDuring functional magnetic resonance imaging, pedophilic and nonpedophilic participants were briefly exposed to same- and opposite-sex images of nude children and adults. We calculated differences in blood oxygen level-dependent signals to child and adult sexual stimuli for each participant. The corresponding contrast images were entered into a group analysis to calculate whole-brain difference maps between groups. We calculated an expression value that corresponded to the group result for each participant. These expression values were submitted to 2 different classification algorithms: Fisher linear discriminant analysis and κ -nearest neighbor analysis. This classification procedure was cross-validated using the leave-one-out method.nnnSETTINGnSection of Sexual Medicine, Medical School, Christian Albrechts University of Kiel, Kiel, Germany.nnnPARTICIPANTSnWe recruited 24 participants with pedophilia who were sexually attracted to either prepubescent girls (nxa0=xa011) or prepubescent boys (nxa0=xa013) and 32 healthy male controls who were sexually attracted to either adult women (nxa0=xa018) or adult men (nxa0=xa014).nnnMAIN OUTCOME MEASURESnSensitivity and specificity scores of the 2 classification algorithms.nnnRESULTSnThe highest classification accuracy was achieved by Fisher linear discriminant analysis, which showed a mean accuracy of 95% (100% specificity, 88% sensitivity).nnnCONCLUSIONSnFunctional brain response patterns to sexual stimuli contain sufficient information to identify pedophiles with high accuracy. The automatic classification of these patterns is a promising objective tool to clinically diagnose pedophilia.

SSVEP-modulation by covert and overt attention: Novel features for BCI in attention neuro-rehabilitation.

In this pilot study the effect of attention (covert and overt) on the signal detection and classification of steady-state visual-evoked potential (SSVEP) were investigated. Using the SSVEP-based paradigm, data were acquired from 4 subjects using 3 scalp electroencephalography (EEG) electrodes located on the visual area. Subjects were instructed to perform the attention task in which they attended covertly or overtly to either of the stimuli flickering with different frequencies (6, 7, 8 and 9Hz). We observed a decrease in signal power in covert compared to the overt attention. However, there was a consistent pattern in covert attention causing an increase in the power of the 2nd harmonic of the attended frequency. Encouraging results of this preliminary study indicates that it can be adapted and implemented in the brain-computer interface (BCI) system which could potentially be used as a neuro-rehabilitation tool for individuals with attention deficit.

Global brain atrophy and metabolic dysfunction in LGI1 encephalitis: A prospective multimodal MRI study

BACKGROUNDnChronic cognitive deficits are frequent in leucin-rich glioma-inactivated 1 protein (LGI1) encephalitis. We examined structural and metabolic brain abnormalities following LGI1 encephalitis and correlated findings with acute and follow-up clinical outcomes.nnnMETHODSnNine patients underwent prospective multimodal 3 Tesla MRI 33.1±18months after disease onset, including automated volumetry, diffusion tensor imaging (DTI) and magnetic resonance spectroscopy (MRS). Data were compared to 9 age- and sex-matched healthy controls.nnnRESULTSnAlthough extratemporal lesions were not present on MRI in the acute stage, tract-based spatial statistics analyses of DTI during follow-up showed widespread changes in the cerebral and cerebellar white matter (WM), most prominent in the anterior parts of the corona radiata, capsula interna and corpus callosum. MRS revealed lower glutamine/glutamate WM levels compared to controls. Higher cerebellar gray matter volume was associated with better function at disease onset (measured by the modified Rankin Scale), and higher putaminal volume was associated with better cognition by Addenbrookes Cognitive Examination test at 23.4±7.6months.nnnCONCLUSIONSnPoor clinical outcome following LGI1 encephalitis is associated with global brain atrophy and disintegration of white matter tracts. The pathological changes affect not only temporomesial structures but also frontal lobes and the cerebellum.

Neuronal activity of two subfunctions of executive control mechanisms – An event-related fMRI study concerning task switching and response inhibition

Background: Cerebral vasospasm is a major complication of aneurysmal subarachnoid hemorrhage (SAH) and may cause delayed ischemic neurological deficits (DIND). Nimodipine improves the clinical outcome following SAH. A spasmolytic effect of systemic nimodipine administration, however, has not yet been reported. Methods: We prospectively monitored 20 patients with aneurysmal SAH for the occurrence and severity of cerebral vasospasm by use of transcranial Doppler and duplex ultrasound. All subjects received oral applications of nimodipine. Upon development of vasospasm, the oral medication was replaced by intravenous nimodipine (48 mg/day). Results: Seventeen of the 20 patients developed cerebral vasospasm. Replacement of oral nimodipine by intravenous nimodipine was associated with a significant reduction of peak systolic flow velocities (PSV) in spastic but not in non-spastic cerebral vessels ( 22.3 ± 3.9% vs. 4.4 ± 4.6%; p < 0.01). In some cases oralization of intravenous treatment led to a relapse of vasospasm (PSV +46.5 ± 6.6% vs. +0.2 ± 58%; p < 0.001). Conclusion: Intravenous but not oral application of nimodipine reduces the severity of cerebral vasospasms following aneurysmal SAH. Future research may elucidate the impact of the pharmaceutical form on the frequency of vasospastic ischemic lesions in patients with SAH.

P122 Contribution of integrated somatosensory and auditory inputs to the cortical response evoked by transcranial magnetic stimulation: A sham TMS-EEG study

Transcranial Magnetic Stimulation (TMS) can effectively stimulate non-invasively the human cortex. The TMS-evoked cortical response can be recorded with electroencephalography (EEG). However, TMS also stimulates our senses by stimulating peripheral trigeminal nerve fibers and creating a loud click. This implies that the TMS-evoked EEG response not only reflects neural activity induced by transcranial excitations of neurons but also neural activity due to somatosensory and auditory stimulation. To characterize the contribution of multisensory peripheral stimulation to TMS-evoked cortical potentials (TEPs), we recorded the evoked EEG response caused by a somato-auditory sham condition which mimicked real TMS. In 20 healthy individuals, TMS was delivered with a figure-of-eight coil over two target sites (posterior parietal cortex and superior frontal gyrus) using two different coil orientations, perpendicular or parallel to sulcus orientation. The sham condition comprised of simultaneous somatosensory and auditory stimulation over the same hotspots as for real TMS. Somatosensory stimulation was achieved via cutaneous electrical stimulation of the scalp, while the TMS coil was used for auditory stimulation ensuring no electric field was induced in the brain by physically separating the coil from the scalp. EEG was acquired with a 61-channel TMS-compatible EEG system. While the early cortical potentials evoked by real or sham TMS differed, TEPs were closely matched in terms of shape and spatial distribution for late components of the evoked EEG responses 70–200xa0ms after the TMS pulse (see Fig. 1 Download : Download high-res image (666KB) Download : Download full-size image ). This was also the case for the N100 which has been commonly attributed to TMS-induced cortical inhibition. The resemblance of the EEG responses evoked by real and sham TMS challenges the notion that TEPs are mainly reflecting transcranial excitation of cortical neurons. This work has been funded by the Novo Nordisk Foundation Interdisciplinary Synergy Program 2014 [“Biophysically adjusted state-informed cortex stimulation (BASICS); Grant No. NNF14OC0011413].

P086 A data-driven method for TMS pulse artefact reduction from EEG data: sPCA

Question Electroencephalographic recording during transcranial magnetic stimulation (EEG/TMS) is used to investigate the state of cortical activity and connectivity (EEG) relative to the non-invasive stimulation of the cortex (TMS). Amplifiers with high dynamics are used to acquire EEG while TMS is performed, but they record also the whole dynamic of the pulse artefact. This is many orders of magnitude higher than the cortical activity, and here we present the procedure that is able to deal with this artefact: ‘the squared principal component analysis (sPCA)’. Methods First principal component analysis (PCA) was applied on raw data. There the time interval related to the artefact was identified by the derivative. Using the newly identified interval, a second PCA is applied on trials that maximally correlate among them. Finally, the artefact is reduced by selecting the principal component that maximally represents the pulse-related artefact. Results This pre-processing procedure applied on single subject dataset minimizes the pulse artefact without impacting the recorded cortical activity. The cleaned data are then approachable with standard procedures used in TMS/EEG analysis.. Conclusions sPCA is an automatic procedure completely data-driven and operator independent. This approach combined with other techniques could give new possibilities to unveil first cortical responses covered by TMS- related artefacts.

P301 Contribution of somatosensory and auditory processing to the TMS evoked cortical response: A sham TMS-EEG study

Objectives Transcranial Magnetic Stimulation (TMS) is capable to non-invasively stimulate the human cortex. Electroencephalography (EEG) can record the cortical response evoked by TMS (TEPs), which are a summation of the brain responses to the TMS-induced electric field in the cortex, and to the multisensory peripheral stimulation derived from the TMS coil discharge. This multisensory stimulation is composed by a somatosensory component relative to the activation of trigeminal nerve fibers and by an auditory component due to the loud click of the coil. Here, we aim to describe the contribution of somatosensory and auditory processing to the TEPs by comparing a somatosensory-auditory sham condition with real TMS. Methods In 18 healthy individuals, TMS was delivered with a figure-of-eight coil over two target sites (parietal and frontal) using two coil orientations. On the same target sites, a sham condition was applied by delivering a cutaneous electrical stimulation concurrently with the TMS click. The EEG was recorded with a 61-channel TMS-compatible system. Results The potentials evoked by real TMS and by somatosensory-auditory sham TMS were highly similar in terms of shape and spatial distribution, particularly at later latencies, 70–200xa0ms, after stimulus administration. Conclusion The present results challenge a straight-forward interpretation of TEPs as an index of cortical connectivity of the focally stimulated brain region, because of the strong contribution of TMS-induced somatosensory and auditory stimulation. This work has been funded by the Novo Nordisk Foundation Interdisciplinary Synergy Program 2014 [“Biophysically adjusted state-informed cortex stimulation (BASICS); Grant No. NNF14OC0011413 ].

ID 345 – “What”, “When”, “Whether” – The electrophysiological correlates of voluntary action in virtual environment

The study of (Libet, 1985) gave rise to active discussion among scientists over the nature of the will and volition, suggesting that intention to perform voluntary action can be predicted from prior neural activity. (Brass and Haggart, 2008) proposed three different classes of voluntary decisions: ”what” type of action to perform, “when” to act, and “whether” to act or not. Those distinct decisions might involve different neural pathways and anatomical regions, including medial pFC, ACC, preSMA and SMA, PMC, and parietal cortex. In our study, we repeatedly confront participants with the three classes of decisions in a natural, yet still strictly controlled experimental setup, involving navigating a car through a virtual environment. For each participant we acquired high-resolution EEG data with 128-channel Biosemi ActiveTwo system, structural MR brain image (3T Philips), and recorded electrode coordinates with Localite neuro-navigation system. We demonstrate electrophysiological differences in activation of brain regions related to different classes of decisions, in terms of spatial distribution and time-frequency modulation. The event-related modulation of EEG signals, along with subject-specific T1 images, session-specific electrode coordinates, and set of spatial filters are then used to localize decision-relevant neuroanatomical sources distributed over frontal and posterior cortical regions.