Sabrina Schneider

Application of functional near-infrared spectroscopy in psychiatry

Two decades ago, the introduction of functional near-infrared spectroscopy (fNIRS) into the field of neuroscience created new opportunities for investigating neural processes within the human cerebral cortex. Since then, fNIRS has been increasingly used to conduct functional activation studies in different neuropsychiatric disorders, most prominently schizophrenic illnesses, affective disorders and developmental syndromes, such as attention-deficit/hyperactivity disorder as well as normal and pathological aging. This review article provides a comprehensive overview of state of the art fNIRS research in psychiatry covering a wide range of applications, including studies on the phenomenological characterization of psychiatric disorders, descriptions of life-time developmental aspects, treatment effects, and genetic influences on neuroimaging data. Finally, methodological shortcomings as well as current research perspectives and promising future applications of fNIRS in psychiatry are discussed. We conclude that fNIRS is a valid addition to the range of neuroscientific methods available to assess neural mechanisms underlying neuropsychiatric disorders. Future research should particularly focus on expanding the presently used activation paradigms and cortical regions of interest, while additionally fostering technical and methodological advances particularly concerning the identification and removal of extracranial influences on fNIRS data as well as systematic artifact correction. Eventually, fNIRS might be a useful tool in practical psychiatric settings involving both diagnostics and the complementary treatment of psychological disorders using, for example, neurofeedback applications.

Show me how you walk and I tell you how you feel - A functional near-infrared spectroscopy study on emotion perception based on human gait

The ability to recognize and adequately interpret emotional states in others plays a fundamental role in regulating social interaction. Body language presents an essential element of nonverbal communication which is often perceived prior to mimic expression. However, the neural networks that underlie the processing of emotionally expressive body movement and body posture are poorly understood. 33 healthy subjects have been investigated using the optically based imaging method functional near-infrared spectroscopy (fNIRS) during the performance of a newly developed emotion discrimination paradigm consisting of faceless avatars expressing fearful, angry, sad, happy or neutral gait patterns. Participants were instructed to judge (a) the presented emotional state (emotion task) and (b) the observed walking speed of the respective avatar (speed task). We measured increases in cortical oxygenated haemoglobin (O2HB) in response to visual stimulation during emotion discrimination. These O2HB concentration changes were enhanced for negative emotions in contrast to neutral gait sequences in right occipito-temporal and left temporal and temporo-parietal brain regions. Moreover, fearful and angry bodies elicited higher activation increases during the emotion task compared to the speed task. Haemodynamic responses were correlated with a number of behavioural measures, whereby a positive relationship between emotion regulation strategy preference and O2HB concentration increases after sad walks was mediated by the ability to accurately categorize sad walks. Our results support the idea of a distributed brain network involved in the recognition of bodily emotion expression that comprises visual association areas as well as body/movement perception specific cortical regions that are also sensitive to emotion. This network is activated less when the emotion is not intentionally processed (i.e. during the speed task). Furthermore, activity of this perceptive network is, mediated by the ability to correctly recognize emotions, indirectly connected to active emotion regulation processes. We conclude that a full understanding of emotion perception and its neural substrate requires the investigation of dynamic representations and means of expression other than the face.

Beyond the N400: complementary access to early neural correlates of novel metaphor comprehension using combined electrophysiological and haemodynamic measurements.

The simultaneous application of different neuroimaging methods combining high temporal and spatial resolution can uniquely contribute to current issues and open questions in the field of pragmatic language perception. In the present study, comprehension of novel metaphors was investigated using near-infrared spectroscopy (NIRS) combined with the simultaneous acquisition of electroencephalography (EEG)/event-related potentials (ERPs). For the first time, we investigated the effects of figurative language on early electrophysiological markers (P200, N400) and their functional relationship to cortical haemodynamic responses within the language network (Brocas area, Wernickes area). To this end, 20 healthy subjects judged 120 sentences with respect to their meaningfulness, whereby phrases were either literal, metaphoric, or meaningless. Our results indicated a metaphor-specific P200 reduction and a linear increase of N400 amplitudes from literal over metaphoric to meaningless sentences. Moreover, there were metaphor related effects on haemodynamic responses accessed with NIRS, especially within the left lateral frontal cortex (Brocas area). Significant correlations between electrophysiological and haemodynamic responses indicated that P200 reductions during metaphor comprehension were associated with an increased recruitment of neural activity within left Wernickes area, indicating a link between variations in neural activity and haemodynamic changes within Wernickes area. This link may reflect processes related to interindividual differences regarding the ability to classify novel metaphors. The present study underlines the usefulness of simultaneous NIRS measurements in language paradigms - especially for investigating the functional significance of neurophysiological markers that have so far been rarely examined - as these measurements are easily and efficiently realizable and allow for a complementary examination of neural activity and associated metabolic changes in cortical areas.

Functional near Infrared Spectroscopy in Psychiatry: A Critical Review

This review deals with the utilisation of functional near infrared (fNIR) spectroscopy for an in vivo assessment of activation changes in brain tissue, which has broadened the range of non-invasive functional imaging methods within the field of neuroscientific research. Due to its simple and quick applicability as well as the absence of side effects, fNIR spectroscopy is particularly well tolerated by psychiatric patients and can hence markedly contribute to the understanding of the neurobiological basis of psychiatric disorders. The optical, light-based method emits near infrared wavelengths of about 700–1000 nm, which are able to penetrate the scalp and skull, into the head. Because near infrared light is distinctively absorbed by the chromophores oxy-haemoglobin (O2Hb) and deoxy-haemoglobin (HHb), the measured relative amount of reflected NIR light can indicate regional oxygenation patterns in cortical brain tissue with a depth resolution of, on average, 1.5 cm and a spatial resolution of about 2–3 cm. Validity and reliability of fNIR spectroscopy measurements to assess task-related cognitive activation have been repeatedly confirmed among healthy subjects. Beyond that, the application of fNIR spectroscopy to detect altered cortical oxygenation in psychiatric patients during cognitive tasks has been greatly intensified over the last two decades. In this context, hypo-frontality, a decrease in frontal lobe activity that is associated with a number of clinical symptoms and psychiatric disorders, has been demonstrated in a wide range of fNIR spectroscopy studies with psychiatric patients. Despite its variety of beneficial properties, the most apparent disadvantages of NIR spectroscopy compared to other imaging techniques are its limited spatial as well as depth resolution and its restriction to cortical areas. Although multimodal approaches based on simultaneous application of NIR spectroscopy combined with other imaging techniques initially revealed promising results, further technical development and a broadened implementation of combined measurements are necessary in order to uncover distinct brain activity alterations in different psychiatric disorders. In addition to the need for further technical improvement of the method, broad and longitudinal applications of fNIR spectroscopy measurements in psychiatric research are required in order to identify robust diagnostic markers which are required to establish NIR spectroscopy as a valid inter-individual screening instrument in psychiatry.

Haemodynamic and electrophysiological markers of pragmatic language comprehension in schizophrenia

Abstract Objectives. The present study aimed at investigating neurophysiological markers of language perception in schizophrenia using simultaneous near-infrared spectroscopy (NIRS) and event-related potentials (ERPs), which have been proven to be useful for studying language processing abilities in psychiatric patients. The study shall help to integrate previous findings from ERP and fMRI studies on figurative language comprehension in schizophrenia and elucidate how electrophysiological and haemodynamic markers of language processing are related. Methods. Twenty-two healthy subjects and 22 schizophrenia patients judged 120 sentences regarding their meaningfulness. Phrases were literal, metaphoric, or meaningless. EEG-fNIRS signals were recorded throughout the entire experiment. Results. Schizophrenia patients showed deficient and delayed sentence comprehension. Both the early N400 and left-hemispheric activation during language comprehension were altered in patients. Correlation analyses showed that metaphor-related ERPs were strongly linked to haemodynamic cortical activity in healthy subjects, but not in patients. Conclusions. Our results indicate group differences in cortical electrophysiological and haemodynamic activation that represent rather general impairments in the processing of complex language. Simultaneous EEG/NIRS applications are useful to depict these neural markers and to investigate their relationship. Future studies are needed to clarify the nature of respective anomalies and their potential as putative neural markers in schizophrenia research.

Functional brain imaging of walking while talking – An fNIRS study

Since functional imaging of whole body movements is not feasible with functional magnetic resonance imaging (fMRI), the present study presents in vivo functional near-infrared spectroscopy (fNIRS) as a suitable technique to measure body movement effects on fronto-temporo-parietal cortical activation in single- and dual-task paradigms. Previous fNIRS applications in studies addressing whole body movements were typically limited to the assessment of prefrontal brain areas. The current study investigated brain activation in the frontal, temporal and parietal cortex of both hemispheres using functional near-infrared spectroscopy (fNIRS) with two large 4×4 probe-sets with 24 channels each during single and dual gait tasks. 12 young healthy adults were measured using fNIRS walking on a treadmill: the participants performed two single-task (ST) paradigms (walking at different speeds, i.e. 3 and 5km/h) and a dual task (DT) paradigm where a verbal fluency task (VFT) had to be executed while walking at 3km/h. The results show an increase of activation in Brocas area during the more advanced conditions (ST 5km/h vs. ST 3km/h, DT vs. ST 3km/h, DT vs. 5km/h), while the corresponding area on the right hemisphere was also activated. DT paradigms including a cognitive task in conjunction with whole body movements elicit wide-spread cortical activation patterns across fronto-temporo-parietal areas. An elaborate assessment of these activation patterns requires more extensive fNIRS assessments than the traditional prefrontal investigations, e.g. as performed with portable fNIRS devices.

Quetiapine and flupentixol differentially improve anterior cingulate cortex function in schizophrenia patients: an event-related potential study

Atypical antipsychotic agents are a frequently and effectively used treatment in schizophrenia and psychotic disorders. Other than conventional antipsychotics, which mainly exert their pharmacological effect in subcortical dopaminergic systems, atypical antipsychotics additionally affect partly serotonergically innervated structures within prefrontal areas, such as the anterior cingulate cortex (ACC). However, only few controlled, randomized studies have so far investigated direct and indirect effects of atypical antipsychotics on the ACC and, up until now, no clinical investigation has exclusively addressed the specific effects of quetiapine on ACC function. The present study assessed ACC function in 18 quetiapine-medicated patients and 13 flupentixol-treated patients suffering from schizophrenia by means of the error-related negativity (ERN), a neurophysiological marker of ACC function, in a pre-post design. Between-group comparisons revealed different effects of quetiapine and flupentixol on ACC function despite similar improvement in psychopathology, cognitive performance and quality of life. Whereas atypical treatment was associated with an increase in amplitudes over time, there were prolonged ERN peak latencies in patients treated with the typical agent. Moreover, treatment effects depended on baseline prefrontal cortex function in both groups. We conclude that both flupentixol and quetiapine improve prefrontal function especially in patients with weak initial ACC function which might be due to their shared affinity for serotonin receptors in frontal brain regions. However, since this affinity is more pronounced for quetiapine, patients treated with quetiapine seemed to profit more evidently concerning their prefrontal cortex function compared to patients of the flupentixol group, who exhibited a compensatory prolongation of processes.

Influence of different stimulation parameters on the somatosensory evoked potentials of the nervus vagus--how varied stimulation parameters affect VSEP.

Summary: Vagus somatosensory evoked potentials are a method for assessing the function of the vagus nerve, which were shown to be altered in neurodegenerative diseases like Alzheimers and Parkinsons disease. Various parameters of the stimulation such as the electrode position and the stimulus intensity have already been investigated. In this study, the focus is on the systematic examination of the other parameters of the stimulation of the vagus somatosensory evoked potentials: stimulus duration, interstimulus interval, and, again, the stimulation intensity. Thirty young and healthy subjects were examined using five different sets of stimulation parameters, and 24 were included in the further analysis. The results show that a reduction of the stimulus duration and a decrease in stimulus intensity have a significant effect on the amplitudes. A shortening of the interstimulus interval does not seem to have such an effect, but this stimulation is rated more painful and unpleasant than the standard stimulation. Overall, the standard stimulation used so far seems to be the most preferable condition.

Effects of transcranial direct current stimulation on craving, heart-rate variability and prefrontal hemodynamics during smoking cue exposure

OBJECTIVE Drug-related cue exposure elicits craving and risk for relapse during recovery. Transcranial direct current stimulation is a promising research tool and possible treatment for relapse prevention. Enhanced functional neuroconnectivity is discussed as a treatment target. The goal of this research was to examine whether transcranial direct current stimulation affected cortical hemodynamic indicators of functional connectivity, craving, and heart rate variability during smoking-related cue exposure in non-treatment-seeking smokers. METHOD In vivo smoking cue exposure supported by a 2mA transcranial direct current stimulation (anode: dorsolateral prefrontal cortex, cathode: orbitofrontal cortex; placebo-controlled, randomized, double-blind) in 29 (age: M=25, SD=5) German university students (smoking at least once a week). Cue reactivity was assessed on an autonomous (heart rate variability) and a subjective level (craving ratings). Functional near-infrared spectroscopy measured changes in the concentration of deoxygenated hemoglobin, and seed-based correlation analysis was used to quantify prefrontal connectivity of brain regions involved in cue reactivity. RESULTS Cue exposure elicited increased subjective craving and heart rate variability changes in smokers. Connectivity between the orbitofrontal and dorsolateral prefrontal cortex was increased in subjects receiving verum compared to placebo stimulation (d=0.66). Hemodynamics in the left dorsolateral prefrontal cortex, however, increased in the group receiving sham stimulation (η2=0.140). Transcranial direct current stimulation did not significantly alter craving or heart rate variability during cue exposure. CONCLUSION Prefrontal connectivity - between regions involved in the processing of reinforcement value and cognitive control - was increased by anodal transcranial direct current stimulation during smoking cue exposure. Possible clinical implications should be considered in future studies.

1609 – How first- and second-generation antipsychotics differentially improve anterior cingulate cortex (ACC) function in schizophrenic patients - an event-related potential study

Introduction/objectives Second-generation antipsychotics (SGAs) are a frequently and effectively used treatment in schizophrenia and psychotic disorders. Other than First-generation antipsychotics (FGAs), which mainly exert their pharmacologic effect in subcortical dopaminergic systems, SGAs additionally affect partly serotonergically innervated structures within prefrontal areas, such as the Anterior Cingulate Cortex (ACC). However, only few controlled, randomized studies have so far investigated direct and indirect effects of SGAs on the ACC. Aims The present study investigated differential effects of one SGA (quetiapine) and one FGA (flupentixol) on the human action monitoring system. Methods ACC function in 18 quetiapine-medicated patients and 13 flupentixol-treated patients suffering from schizophrenia was assessed by means of the error-related negativity (ERN), a neurophysiological marker of ACC function, in a pre-post design. Results Between-group comparisons revealed different effects of quetiapine and flupentixol on ACC function despite similar improvement in psychopathology, cognitive performance and quality of life. Whereas SGA treatment was associated with an increase in amplitudes over time, there were prolonged ERN peak latencies in patients treated with the FGA. Moreover, treatment effects depended on baseline PFC function in both groups. Conclusions We conclude that both flupentixol and quetiapine improve prefrontal function especially in patients with weak initial ACC function which might be due to their shared affinity for 5HT-receptors in frontal brain regions. However, since this affinity is more pronounced for SGAs, patients treated with quetiapine seemed to profit more evidently concerning PFC function compared to patients of the flupentixol group, who exhibited a compensatory prolongation of processes.