Annika Wagener

Allelic variation of serotonin transporter function modulates the brain electrical response for error processing.

A functional length variation in the transcriptional control region of the serotonin transporter gene (5-HTTLPR) influences brain function, personality traits, and susceptibility to psychiatric disorders. Here we measured prefrontal brain function by means of event-related potentials during an error processing paradigm. Physiologically, occurrence of an error elicits two specific electrical responses in the prefrontal cortex, the early error related negativity (Ne/ERN) and the later occurring error positivity (Pe), reflecting different components of error processing. Healthy subjects with one or two copies of the low-activity 5-HTTLPR short variant showed significantly higher amplitudes of the Ne/ERN and a trend to higher amplitudes of the Pe as compared to age- and gender-matched individuals homozygous for the long allele. Performance measures and latencies of these ERP-components did not differ between groups. These results indicate that the 5-HTTLPR short variant is associated with enhanced responsiveness of the brain and further supports the notion that prefrontal brain function is influenced by allelic variation in serotonin transporter function.

Multi-channel near-infrared spectroscopy detects specific inferior-frontal activation during incongruent Stroop trials

Near-infrared spectroscopy (NIRS) is an optical method, which allows non-invasive in vivo measurements of changes in the concentration of oxygenated (O2Hb) and deoxygenated (HHb) hemoglobin in brain tissue. In the present study we investigated 10 healthy subjects by means of multi-channel NIRS (Optical Topography; ETG-100, Hitachi Medical Co., Japan) during performance of congruent and incongruent trials of the Stroop color word task. With a similar pattern of activation for both congruent and incongruent Stroop trials in the NIRS channels located left superior-frontally, the results for O2Hb and the total amount of hemoglobin (Hb-tot) indicate specific activation for interference trials in inferior-frontal areas of the left hemisphere. This result is in line with several neuroimaging studies (fMRI, PET) that have already investigated the frontal activation related to Stroop interference, which further supports the assumption that multi-channel NIRS is sensitive enough to detect spatially specific activation during the performance of cognitive tasks.

Far field potentials from the brain stem after transcutaneous vagus nerve stimulation

Summary. Recently, the vagus nerve has gained particular interest in neuropsychiatry, as neurodegenerative diseases like Alzheimer’s and Parkinson’s disease are supposed to affect the brainstem nuclei of the vagus nerve early in their course. In addition, electric stimulation of the vagus nerve has therapeutic effects in otherwise therapy-refractory epilepsies and depressions. So far, no method is available to assess vagus nerve function in this context. On this background and based on the established techniques of early acoustic evoked potentials we investigated if a transcutaneous electric stimulation of the sensory auricular branch of the vagus nerve innervating parts of the outer ear is feasible in healthy subjects using this hypothesis-generated approach. We were able to record a clear, reproducible Vagus Sensory Evoked Potential (VSEP) measured as far field potential probably originating in vagus nuclei in the brainstem. Further studies are needed to test the interindividual stability and test-retest reliability of this new method before potential diagnostic and therapeutic applications might be evaluated.

Unconscious manipulation of free choice in humans

Previous research has shown that subliminally presented stimuli accelerate or delay responses afforded by supraliminally presented stimuli. Our experiments extend these findings by showing that unconscious stimuli even affect free choices between responses. Thus, actions that are phenomenally experienced as freely chosen are influenced without the actor becoming aware of the manipulation. However, the unconscious influence is limited to a response bias, as participants chose the primed response only in up to 60% of the trials. LRP data in free choice trials indicate that the prime was not ineffective in trials in which participants chose the non-primed response as then it delayed performance of the incongruently primed response.

Nah-Infrarot-Spektroskopie in der Psychiatrie

ZusammenfassungDie Nah-Infrarot-Spektroskopie (NIRS) ist eine nichtinvasive optische Methode zur Messung der regionalen Hirngewebeoxygenierung in vivo. Licht aus dem nah-infraroten Spektrum kann die Schädelkalotte durchdringen und wird im Hirngewebe hauptsächlich von Oxy- (O2Hb) und Deoxyhämoglobin (HHb) absorbiert. Aus der Relation von in das Gehirn abgegebenem zu reflektiertem Nah-Infrarot-Licht kann daher spektrophotometrisch die regionale Konzentrationsänderung von O2Hb und HHb berechnet werden. Es wurde bereits gezeigt, dass NIRS nicht nur massive Hirndurchblutungsstörungen bei schweren neurologischen Erkrankungen erfassen kann, sondern dass die Methode auch ausreichend sensitiv ist, um bei gesunden Probanden aufgabenspezifische Aktivierungsmuster während definierter kognitiver Prozesse zu messen. Erste Untersuchungen an psychiatrischen Patienten weisen auf veränderte regionale Hirngewebsoxygenierungen im Vergleich zu Kontrollgruppen während kognitiver Aktivierungsaufgaben hin. NIRS hat aufgrund seiner unkomplizierten, schnellen Durchführung, seiner Nebenwirkunsfreiheit und der hohen Akzeptanz bei psychiatrischen Patienten eindeutige Vorteile im Vergleich zu anderen Methoden der funktionellen Bildgebung, die die Methode auch als potenzielles Screeningverfahren in der Psychiatrie attraktiv erscheinen lassen. Voraussetzung dafür ist allerdings, dass sich in Zukunft stabile und reliable NIRS-Parameter mit diagnostischem und/oder prognostischem Wert für bestimmte psychiatrische Erkrankungen entwickeln lassen, was nur durch eine breitere Nutzung dieser Methode in der psychiatrischen Forschung in Verbindung mit bereits etablierten Methoden der Neurophysiologie und der funktionellen Bildgebung gelingen wird.SummaryNear-infrared spectroscopy (NIRS) is a noninvasive optical method for in vivo measurement of regional brain tissue oxygenation. Light from the near-infrared spectrum can penetrate the skull and is mainly absorbed by oxyhaemoglobin (O2Hb) and desoxyhaemoglobin (HHb). From the amount of reflected near-infrared light in relation to the amount absorbed by brain tissue, regional changes in O2Hb and HHb concentrations can be calculated spectrophotometrically. It has been shown that NIRS is not only able to measure massive disturbances in cerebral blood circulation due to serious neurological diseases, but that it also is sensitive enough to assess task-specific patterns of activation in healthy subjects during circumscribed cognitive processes. Preliminary investigations indicate altered regional brain tissue oxygenation in psychiatric patients during cognitive activation tasks. The NIRS outmatches other functional imaging methods in that it has no side effects and is well tolerated by psychiatric patients. Furthermore, it can be applied quickly and easily. Thus, NIRS is a potential screening method in psychiatric settings, provided that robust parameters of reliable diagnostic and/or prognostic value can be developed for individual psychiatric illnesses. However, this will depend on broader application of the method combined with established neurophysiological procedures and functional imaging techniques in psychiatric research.

Near-infrared optical topography to assess activation of the parietal cortex during a visuo-spatial task.

Multi-channel near-infrared spectroscopy (NIRS) is a relatively new method to investigate the brain activation, based on changes in oxygenated haemoglobin (O2Hb) and deoxygenated haemoglobin (HHb). Recently, it has been shown that NIRS seems to be able to detect even small changes in O2Hb and HHb concentration due to cognitive demands. This study aimed at investigating the changes in O2Hb and HHb concentrations of the parietal cortex during a spatial task, a modified version of the Benton Line Orientation Task [Gur, R. C., Alsop, D., Glahn, D., Petty, R., Swanson, C. L., Maldjian, J. A., et al. (2000). An fMRI study of sex differences in regional activation to a verbal and a spatial task. Brain & Language, 74(2), 157-170.]. Twenty-four subjects were measured with NIRS while they had to estimate the orientation of a given line or to name the colour of the line in the control condition. Both conditions consisted of three activation phases each lasting 30 s, with a 10 s baseline and a 20 s post resting period. For assessing the changes in O2Hb and HHb concentrations, we measured with 24 NIRS channels over the parietal cortex using the NIRS apparatus ETG-100 (Hitachi Medical Ltd.). O2Hb concentration significantly increased during the active phase compared to the baseline for both conditions, but was significantly higher in the active phase for the line orientation condition compared to the colour naming condition bilaterally parieto-occipital. For the HHb concentrations, we only found significant decreases for both conditions but no differences between the conditions. The results of our study underscore the value of multi-channel NIRS for assessing cortical activation during cognitive tasks.

Nah-Infrarot-Spektroskopie in der Psychiatrie@@@Near-infrared spectroscopy in psychiatry

ZusammenfassungDie Nah-Infrarot-Spektroskopie (NIRS) ist eine nichtinvasive optische Methode zur Messung der regionalen Hirngewebeoxygenierung in vivo. Licht aus dem nah-infraroten Spektrum kann die Schädelkalotte durchdringen und wird im Hirngewebe hauptsächlich von Oxy- (O2Hb) und Deoxyhämoglobin (HHb) absorbiert. Aus der Relation von in das Gehirn abgegebenem zu reflektiertem Nah-Infrarot-Licht kann daher spektrophotometrisch die regionale Konzentrationsänderung von O2Hb und HHb berechnet werden. Es wurde bereits gezeigt, dass NIRS nicht nur massive Hirndurchblutungsstörungen bei schweren neurologischen Erkrankungen erfassen kann, sondern dass die Methode auch ausreichend sensitiv ist, um bei gesunden Probanden aufgabenspezifische Aktivierungsmuster während definierter kognitiver Prozesse zu messen. Erste Untersuchungen an psychiatrischen Patienten weisen auf veränderte regionale Hirngewebsoxygenierungen im Vergleich zu Kontrollgruppen während kognitiver Aktivierungsaufgaben hin. NIRS hat aufgrund seiner unkomplizierten, schnellen Durchführung, seiner Nebenwirkunsfreiheit und der hohen Akzeptanz bei psychiatrischen Patienten eindeutige Vorteile im Vergleich zu anderen Methoden der funktionellen Bildgebung, die die Methode auch als potenzielles Screeningverfahren in der Psychiatrie attraktiv erscheinen lassen. Voraussetzung dafür ist allerdings, dass sich in Zukunft stabile und reliable NIRS-Parameter mit diagnostischem und/oder prognostischem Wert für bestimmte psychiatrische Erkrankungen entwickeln lassen, was nur durch eine breitere Nutzung dieser Methode in der psychiatrischen Forschung in Verbindung mit bereits etablierten Methoden der Neurophysiologie und der funktionellen Bildgebung gelingen wird.SummaryNear-infrared spectroscopy (NIRS) is a noninvasive optical method for in vivo measurement of regional brain tissue oxygenation. Light from the near-infrared spectrum can penetrate the skull and is mainly absorbed by oxyhaemoglobin (O2Hb) and desoxyhaemoglobin (HHb). From the amount of reflected near-infrared light in relation to the amount absorbed by brain tissue, regional changes in O2Hb and HHb concentrations can be calculated spectrophotometrically. It has been shown that NIRS is not only able to measure massive disturbances in cerebral blood circulation due to serious neurological diseases, but that it also is sensitive enough to assess task-specific patterns of activation in healthy subjects during circumscribed cognitive processes. Preliminary investigations indicate altered regional brain tissue oxygenation in psychiatric patients during cognitive activation tasks. The NIRS outmatches other functional imaging methods in that it has no side effects and is well tolerated by psychiatric patients. Furthermore, it can be applied quickly and easily. Thus, NIRS is a potential screening method in psychiatric settings, provided that robust parameters of reliable diagnostic and/or prognostic value can be developed for individual psychiatric illnesses. However, this will depend on broader application of the method combined with established neurophysiological procedures and functional imaging techniques in psychiatric research.

Temporal Cueing of Target-Identity and Target-Location

In four experiments either a short or a long foreperiod preceded the presentation of one of two targets, presented either in the center of the screen (Experiment 1) or at one of two locations (Experiments 2-4). Participants were to identify the presented target by pressing a left or a right button as quickly as possible. In Experiment 1, each of the two targets and in Experiment 2, each of the two locations appeared frequently after one and infrequently after the other foreperiod. Experiments 3 and 4 explored the combined effects of disparate frequency distributions of targets and locations to the two foreperiods. Reaction times and error rates revealed faster processing and/or less errors for respectively those targets and locations which were frequent after the current foreperiod. The data suggest that besides location-specific target expectancies (Hoffmann & Kunde, 1999) also time-specific expectancies for those targets and target-locations are formed which are likely at the respective point in time.

The specificity of temporal expectancy: Evidence from a variable foreperiod paradigm

In speeded choice tasks with variable foreperiods (FPs), individuals behaviourally adapt to various frequency manipulations. Adaptations have been shown to frequencies of different stimulus–response events, to frequencies of different foreperiods, and to frequencies of different event–foreperiod combinations. We have investigated how participants adapt to a situation where all three frequency manipulations are done simultaneously. Three variable foreperiod experiments are reported. In Experiment 1, one target (the peak distributed target) appeared particularly frequently after one particular FP (the peak foreperiod), while another target was less frequent and equally distributed over all foreperiods. In Experiment 2, the equally distributed target was overall more frequent than the peak distributed one. In both experiments, performance advantages for the peak distributed target were specific to the peak foreperiod, and performance advantages at the peak foreperiod were specific to the peak distributed targets. A third experiment showed that, when two differently frequent target are both equally distributed over FPs, the performance distribution over FPs is not significantly different between both targets. Together, the results suggest that participants were able to simultaneously and specifically adapt to frequency manipulations in events, foreperiods, and event–foreperiod combinations.