Inga Griskova-Bulanova

Closed eyes condition increases auditory brain responses in schizophrenia.

The 40-Hz auditory steady-state responses (ASSRs) of 14 medicated schizophrenic patients were recorded in eyes-open and eyes-closed conditions as previously done in healthy volunteers. Patients show significantly increased precision of the evoked response with eyes closed, and a significant increase of broad-band noise activity when eyes are open.

Effect of attention on 40 Hz auditory steady-state response depends on the stimulation type: Flutter amplitude modulated tones versus clicks

Auditory steady-state responses (ASSRs) are used to test the ability of local cortical networks to generate gamma frequency activity in patients with psychiatric disorders. For the effective use of ASSRs in research and clinical applications, it is necessary to find a comfortable stimulation type and to know how ASSRs are modulated by the tasks given to the subjects during the recording session. We aimed to evaluate the suitability of flutter amplitude modulated tone (FAM) stimulation for generation of ASSRs: subjective pleasantness of FAMs and attentional effects on FAM-elicited 40Hz ASSRs were assessed. Commonly used click stimulation was used for comparison. FAMs produced ASSRs that were stable over the variety of tasks - they were not modulated by attentional demands during the task; responses to clicks were reduced and less synchronized during distraction. FAM stimuli were rated as less unpleasant and less arousing than click stimuli, thus being more pleasant to the subjects. Our findings suggest that FAM stimulation might be more suitable in conditions, where attention is difficult to control, i.e. in clinical settings.

40 Hz auditory steady-state response in schizophrenia: Sensitivity to stimulation type (clicks versus flutter amplitude-modulated tones)

Auditory steady-state response (ASSR) at 40Hz has been proposed as a potential biomarker for schizophrenia. The ASSR studies in patients have used click stimulation or amplitude-modulated tones. However, the sensitivity of 40Hz ASSRs to different stimulation types in the same group of patients has not been previously evaluated. Two stimulation types for ASSRs were tested in this study: (1) 40Hz clicks and (2) flutter-amplitude modulated tones. The mean phase-locking index, evoked amplitude and event-related spectral perturbation values were compared between schizophrenia patients (n=26) and healthy controls (n=20). Both stimulation types resulted in the observation of impaired phase-locking and power measures of late (200-500ms) 40Hz ASSR in patients compared to healthy controls. The early-latency (0-100ms) 40Hz ASSR part was diminished in the schizophrenia group in response to clicks only. The late-latency 40Hz ASSR parameters obtained through different stimulation types correlated in healthy subjects but not in patients. We conclude that flutter amplitude-modulated tone stimulation, due to its potential to reveal late-latency entrainment deficits, is suitable for use in clinical populations. Careful consideration of experimental stimulation settings can contribute to the interpretation of ASSR deficits and utilization as a potential biomarker.

Brain responses and self-reported indices of interoception: Heartbeat evoked potentials are inversely associated with worrying about body sensations

Interoception may be defined as a group of senses reflecting physiological state of the body; however the link between physiological and self-reported indices of interoception is not well established. We aimed to elucidate the relationship between the CNS representation of interoceptive processing - the late part of the heartbeat evoked potential (HEP) - and the self-reported interoceptive abilities and tendencies as assessed with the scales of Multidimensional Assessment of Interoceptive Awareness (MAIA) questionnaire. The HEP amplitudes at 400-600ms and MAIA scores from 30 healthy participants were subjected to the cluster-based permutation tests on the t-values of Pearson correlations. HEP amplitudes were positively associated with individual scores on the Not-Worrying scale of MAIA at Cz in the time window from 400ms to 545ms after the R peak. No other MAIA scales were related to the late HEP amplitudes, suggesting that scales and HEPs measure different aspects that are not directly interrelated. This supports the need to treat interoception as a multidimensional construct.

Interoception and gender: What aspects should we pay attention to?

Interoception is involved in both somatic and mental disorders with different prevalence between genders; however, gender differences are often neglected. To examine the potential gender differences in interoceptive awareness, we recruited 376 healthy subjects (51% males, aged 17-30years), to fill in the Multidimensional Assessment of Interoceptive Awareness (MAIA). Of that sample, in a subgroup of 40 subjects (50% males), interoceptive accuracy was assessed by heartbeat counting task (HCT). The results on interroceptive awareness suggest that females tendto notice bodily sensations more often, better understand relations between bodily sensations and emotional states, worry or experience more emotional distress with sensations of pain or discomfort and see body as less safe. The results of interoceptive accuracy further suggest that females are less efficient in consciously detecting heartbeats. Therefore, gender should be considered when interoceptive evaluation is performed in disorders associated to bodily sensations and to the emotional/mood states.

Go and NoGo: modulation of electrophysiological correlates by female sex steroid hormones

RationaleThe behavioral and electrophysiological responses in a Go/NoGo task are objective measures of executive functioning that may be impaired in clinical conditions. Prior to the wider application of Go/NoGo tasks in clinics, it is tempting to evaluate factors causing modulation of the responses.ObjectiveWe aimed to evaluate the effect of different levels of female sex steroids on Go/NoGo task-related ERPs in healthy females.MethodsThirty-four young healthy females performed an equiprobable (50/50) auditory Go/NoGo task. Amplitudes and latencies of N2 and P3 peaks from Fz, Cz, and Pz electrodes were evaluated. 17β-estradiol and progesterone levels in saliva samples were measured. Electrophysiological measures were correlated to 17β-estradiol and progesterone concentrations.ResultsThe diverse pattern of modulation of P3 latencies was shown: higher levels of 17β-estradiol contributed to Go-P3 latency prolongation, and higher levels of progesterone contributed to NoGo-P3 latency shortening. Higher levels of 17β-estradiol were associated with more negative frontal N2 amplitude in both conditions.ConclusionsThe relationship between electrophysiological correlates of executive functioning to individual hormonal levels points to a broader range of variation sources in healthy subjects which might mask or pronounce between-group differences in clinical studies.

Progesterone and Mental Rotation Task: Is There Any Effect?

Mental rotation task (MRT) incorporates elements of spatial abilities, important in many professions, with people of both genders involved. Importantly, these are the areas where spatial tasks might be performed for long time periods; thus adverse effects of mental fatigue are highly unwanted. Substantial variation of MRT performance in relation to estrogen levels has been observed in many studies, whereas the role of progesterone remains elusive. Here we aimed to elucidate the effect of progesterone level on the long-duration (1.5 hours) performance of MRT. We included three groups of subjects: a group of males as a control, a group of females in their follicular phase (low progesterone) and a group of females in their luteal phase (high progesterone), MRT accuracy and response time, subjective fatigue ratings and cardiovascular measures together with 17β-estradiol and progesterone concentrations were analyzed. We found that subjective ratings of fatigue increased, performance accuracy increased, and mean response times decreased during the task in all groups. Females in luteal phase were significantly slower not only than men, but also than females in their follicular phase. An increase in subjective fatigue ratings was positively related to progesterone level—at higher progesterone levels, females felt more tired.

Global field synchronization of 40 Hz auditory steady-state response: Does it change with attentional demands?

Auditory steady-state responses (ASSRs) are increasingly used in research of neuropsychiatric disorders and for brain-computer interface applications. However, results on attentional modulation of ASSRs are inconclusive. The evaluation of large-scale effects of task-related modulation on ASSRs might give better estimation of the induced changes. The aim of the study was to test global field synchronization - a reference-independent evaluation of the amount of phase-locking among all active regions at a given frequency - during tasks differing in attentional demands to 40 Hz auditory stimulation. Twenty seven healthy young males participated in the EEG study with concurrent 40 Hz binaural click stimulation and three experimental tasks: 1) to count presented stimuli (focused attention); 2) to silently read a text (distraction); 3) to stay awake with closed eyes (resting). We showed that during auditory 40 Hz stimulation, the global field synchronization of the EEG increased as compared to the silent baseline period and the largest increase was observed when subjects counted stimuli or rested with closed eyes. Our results provide insights that depending on the method of assessment, the 40 Hz ASSR might be an indicator of both local and complex synchronization processes that are affected by the state (task performed or psychopathology) of the participants.

Low and high gamma auditory steady-states in response to 440 Hz carrier chirp-modulated tones show no signs of attentional modulation

Auditory steady-state responses (ASSRs) are increasingly used as a neurodiagnostical tool and in neurotechnological applications where it is important to test responses at different frequencies. We aimed to evaluate EEG responses to a low-frequency carrier (440 Hz) tone modulated with 500 ms chirps at 1-120 Hz and to test the ability of stimulation to highlight the low and high gamma band activity. Increasing and decreasing modulation rates were applied. Subjective pleasantness of chirps and attentional effects on ASSRs to chirps were assessed. Our results suggest that brief low-frequency tones modulated with chirps can be used to evoke ASSRs and to test responses at low and high gamma frequencies. Moreover, chirps are perceived as moderately arousing and neutrally pleasant, while ASSRs to these sounds are not sensitive to attentional modulation. The abovementioned findings make chirp stimulation suitable for use in populations with increased perceptual sensitivity to auditory stimuli, for instance like patients with schizophrenia.

Gender effects on auditory P300: A systematic review

The evidence suggests that gender-related effects could influence the electrophysiological P300 parameters and stand as an additional source of variation for both clinical and non-clinical subjects. The aim of this paper is to characterize gender-related differences in P300 potential as elicited with simple auditory paradigms. This knowledge (1) is important for the practical assessment of P300 potential in normal and clinical populations, and (2) can provide an insight into the understanding of gender differences in pathophysiology, particularly those with differential risk or prevalence in males and females. With this review it is shown that a limited number of studies encounter possible gender effects on parameters of auditory P300, and the findings need to be read with caution due to methodological limitations of the studies. Nevertheless, evidence supports that the P300 amplitude could be significantly modulated by gender, with greater amplitude in females relative to males. Noteworthy, gender has a minimal effect on the P300 latency, and it is often comparable between males and females. Furthermore, the effect of gender on P300 could be modulated by hormonal background, anatomy and some methodological aspects.