Gamma Spectral Power Research Articles

Assessing attention and cognitive function in completely locked-in state with event-related brain potentials and epidural electrocorticography

Objective. Patients in the completely locked-in state (CLIS), due to, for example, amyotrophic lateral sclerosis (ALS), no longer possess voluntary muscle control. Assessing attention and cognitive function in these patients during the course of the disease is a challenging but essential task for both nursing staff and physicians. Approach. An electrophysiological cognition test battery, including auditory and semantic stimuli, was applied in a late-stage ALS patient at four different time points during a six-month epidural electrocorticography (ECoG) recording period. Event-related cortical potentials (ERP), together with changes in the ECoG signal spectrum, were recorded via 128 channels that partially covered the left frontal, temporal and parietal cortex. Main results. Auditory but not semantic stimuli induced significant and reproducible ERP projecting to specific temporal and parietal cortical areas. N1/P2 responses could be detected throughout the whole study period. The highest P3 ERP was measured immediately after the patient's last communication through voluntary muscle control, which was paralleled by low theta and high gamma spectral power. Three months after the patient's last communication, i.e., in the CLIS, P3 responses could no longer be detected. At the same time, increased activity in low-frequency bands and a sharp drop of gamma spectral power were recorded. Significance. Cortical electrophysiological measures indicate at least partially intact attention and cognitive function during sparse volitional motor control for communication. Although the P3 ERP and frequency-specific changes in the ECoG spectrum may serve as indicators for CLIS, a close-meshed monitoring will be required to define the exact time point of the transition.

Spontaneous dense array gamma activity in children and adolescents with volatile solvent dependence.

Objectives:Children and adolescents with volatile solvent/inhalant dependence have neurocognitive deficits. The study aimed to explore resting state gamma activity, which is a marker of cognitive function, in children and adolescents with inhalant dependence. The study also investigated differences in gamma activity across groups differing in inhaled amounts.Materials and Methods:Clinical and electroencephalographic (EEG) data were collected from nine patients with inhalant dependence. 30–50 Hz spectral power was calculated using Welch's averaged periodogram method. The data were analyzed using descriptive statistics, bi-variate correlation, and nonparametric Mann–Whitney U-test.Results:While significant positive correlation was found between duration of dependence and gamma spectral power in left frontal region, no significant differences were found on comparison of the groups on gamma spectral power.Conclusion:A complex neurobiological interaction is involved in the synaptic modulation brought about by inhalant use and this could be understood by studying changes in EEG parameters especially gamma activity.

Schneiderian first rank symptoms and gamma oscillatory activity in neuroleptic naïve first episode schizophrenia: a 192 channel EEG study.

ObjectiveSchneiderian first-rank symptoms (FRS) and abnormal EEG gamma activity in schizophrenia have been reported independently to have a neurodevelopmental basis. We aimed to investigate spontaneous gamma power in two groups of first episode schizophrenia patients (those who experience FRS and those who do not).MethodsA comparative hospital based study having 37neuroleptic naïve male patients with schizophrenia divided into two groups-FRS(+) and FRS(-) groups based on the presence of FRS. Thirty age, sex, education and handedness matched individuals served as controls (N). All participants underwent a 192-channel resting Electroencephalography (EEG) recording. Gamma spectral power was calculated for low- (30-50 Hz) and high-gamma 1 & 2 (51-70 and 71-100 Hz) bands. Spectral power was compared between three groups using MANOVA and supplementary one-way ANOVA with Bonferroni test controlling for multiple comparisons. Linear regression was used to identifying predictor variables for FRS. Pearson correlation coefficient was computed between spectral power parameters and various clinical variables.ResultsSignificantly higher high gamma band-1 power was observed over right frontal (p<0.05), parietal (p<0.05) and temporal (p<0.05) regions in FRS(+) than FRS(-) group and normal controls. Right parietal high gamma-1 power and paranoid cluster on PANSS significantly predicted number of FRS in total schizophrenia patients; paranoid cluster on PANSS showed significant correlation with number of FRS in FRS(+) group.ConclusionFindings of our study add to the evidence that areas contained within the hetero modal association cortex are associated with FRS. The study findings also strengthen the neurodevelopmental basis of FRS in schizophrenia.

High frequency spectral power of sleep EEG increases with depressive and insomnia symptoms in kidney transplant recipients

The prevalence of depression and insomnia is high among kidney transplant recipients and the co-occurence of the two disorders is frequent. Hyperarousal of the central nervous system (CNS) might play a role in the pathomechanism of both conditions. The hypervigilant state of the CNS is characterized by heightened beta- and gamma spectral power of the EEG. We investigated whether depressive and isomnia symptoms correlate with high frequency spectral power among kidney transplant recipients. Fitfy-six kidney tranplant recipients participated in the study (35 males, mean age 49 ± 13 years, BMI 26 ± 4 kg/m 2 , estimated glomerular filtration rate 50 ± 17 ml/min). Symptoms of insomnia and depression were measured by the Athens Insomnia Scale (AIS) and the Center for Epidemiologic Studies Depression Scale (CESD), respectively. After one-night polysomnography (PSG) each recording was visually scored and EEG absolute spectral power was computed within the sigma (11.25–15 Hz), beta1 (15.25–25 Hz), beta2 (25.25–35 Hz), and gamma (35.25–45 Hz) frequency bands. AIS score correlated with sleep latency ( r = 0.274, p < 0.05) among the PSG macrostructure parameters while CESD score did not correlate with any PSG variables. CESD score correlated with NREM and REM gamma ( r = 0.35; r = 0.27), beta2 ( r = 0.28; r = 0.3), beta1 ( r = 0.32; r = 0.27) spectra, respectively. AIS score correlated with NREM and REM gamma ( r = 0.27; r = 0.31), beta2 ( r = 0.27; r = 0.44), NREM sigma ( r = 0.29) and REM beta1 ( r = 0.37) spectra, respectively ( p < 0.05 for each correlation). In multivariable linear model after controlling for age, gender, kidney function and BMI, the CESD score was an independent predictor of NREM gamma (Beta: 0.276; p < 0.05) and AIS was in independent relation with REM beta2 (Beta: 0.328; p < 0.05). We demonstrated for the first time in this population that the symptoms of depression and insomnia correlate with increased neurocognitive activity of the CNS during sleep, in particular, with increased NREM gamma and REM beta2 activity. These data support the hypothesis that CNS hyperarousal might contribute to the emergence of both conditions among kidney transplant recipients. Compared to routinely used sleep variables, quantitative analysis of EEG reveals further information about these conditions. The authors have no conflict of interest to declare in relation to this work.

Localization of epileptogenic zones in Lennox–Gastaut syndrome using frequency domain source imaging of intracranial electroencephalography: a preliminary investigation

Although intracranial electroencephalography (iEEG) has been widely used to localize epileptogenic zones in epilepsy, visual inspection of iEEG recordings does not always result in a favorable surgical outcome, especially in secondary generalized epilepsy such as Lennox–Gastaut syndrome (LGS). Various computational iEEG analysis methods have recently been introduced to confirm the visual inspection results. Of these methods, high gamma oscillation in iEEG has attracted interest because a series of studies have reported a close relationship between epileptogenic zones and cortical areas with high gamma oscillation. Meanwhile, frequency domain source imaging of EEG and MEG oscillations has proven to be a useful auxiliary tool for identifying rough locations of epileptogenic zones. To the best of our knowledge, however, frequency domain source imaging of high gamma iEEG oscillations has not been studied. In this study, we investigated whether the iEEG-based frequency domain source imaging of high gamma oscillation (60–100 Hz) would be a useful supplementary tool for identifying epileptogenic zones in patients with secondary generalized epilepsy. The method was applied to three successfully operated on LGS patients, whose iEEG contained some ictal events with distinct high gamma oscillations before seizure onset. The resultant cortical source distributions were compared with surgical resection areas and with high gamma spectral power distributions on the intracranial sensor plane. While the results of the sensor-level analyses contained many spurious activities, the results of frequency domain source imaging coincided better with the surgical resection areas, suggesting that the frequency domain source imaging of iEEG high gamma oscillations might help enhance the accuracy of pre-surgical evaluations of patients with secondary generalized epilepsy.

Comparative EEG-Study of Normal and Autistic Children

The work represents the results of a comparative study of a spectral power as well as averaged coherence in theta and gamma-EEG band in a healthy and autistic boys (the mean age 6 years 1 month). Healthy boys showed a decreasing in theta spectral power as well as in averaged coherence, and increasing in gamma spectral power as well as in averaged coherence during cognitive task. Spectral power of gamma band shows more high scores in autistic boys than in normal ones. Cognitive task situation do not change spectral power of the fast oscillations in autistic children. Spectral power of theta--band shows more low scores in autistic boys than in normal ones. Cognitive task situation do not change spectral power and averaged coherence of theta oscillations in autistic children.

Increased spontaneous gamma power and synchrony in schizophrenia patients having higher minor physical anomalies

The higher frequency of minor physical anomalies (MPAs) in schizophrenia provides morphological evidence for the neurodevelopmental theory. Abnormal gamma oscillations (>30Hz) seen in the electroencephalogram (EEG) in schizophrenia have been hypothesized to result from developmental insults. This study investigated spontaneous gamma oscillations in schizophrenia patients having higher and lower number of MPAs. Forty drug naïve/free schizophrenia patients and 20 matched healthy controls were assessed for MPAs on the Extended Waldrop Scale (EWS). All participants underwent an awake, resting 192-channel EEG recording. Spontaneous gamma spectral power and coherence were estimated in the low- (30–50Hz) and high-gamma (51–70 and 71–100Hz) bands. Significantly higher power was observed in high-MPA than healthy control group in low-gamma band over right frontal, parietal and temporal regions. Spectral power in the high-gamma band (71–100Hz) was also significantly higher in the high-MPA schizophrenia subgroup than in the healthy control group over left frontal, parietal and temporal regions. Additionally, regional intra-hemispheric and inter-hemispheric coherence in the low-gamma band was significantly higher in the high-MPA schizophrenia subgroup than on the healthy control group. This study is the first to provide evidence of increased spontaneous gamma power and synchrony in schizophrenia patients having higher MPAs, supporting the idea that it may represent a distinct subgroup of schizophrenia with a neurodevelopmental basis.

S.07.04 Progesterone and estradiol plasma levels modulate serotonin-1A binding in the human brain

Unusual reactions to auditory stimuli are often observed in autism and may relate to ineffective inhibitory modulation of sensory input (sensory gating). A previous study of P50 sensory gating did not reveal abnormalities in high-functioning school age children [C. Kemner, B. Oranje, M.N. Verbaten, H. van Engeland, Normal P50 gating in children with autism, J. Clin. Psychiatry 63 (2002) 214–217]. Sensory gating deficit may, however, characterize younger children with autism or be a feature of retarded children with autism, reflecting imbalance of neuronal excitation/inhibition in these cohorts. We applied a paired clicks paradigm to study P50 sensory gating, and its relation to IQ and EEG gamma spectral power (as a putative marker of cortical excitability), in young (3–8 years) children with autism (N = 21) and age-matched typically developing children (N = 21). P50 suppression in response to the second click was normal in high-functioning children with autism, but significantly (p < 0.03) reduced in those with mental retardation. P50 gating improved with age in both typically developing children and those with autism. Higher ongoing EEG gamma power corresponded to lower P50 suppression in autism (p < 0.02), but not in control group. The data suggest that ineffective inhibitory control of sensory processing is characteristic for retarded children with autism and may reflect excitation/inhibition imbalance in this clinical group.

Worry, generalized anxiety disorder, and emotion: Evidence from the EEG gamma band

The present study examined EEG gamma (35–70Hz) spectral power distributions during worry inductions in participants suffering from generalized anxiety disorder (GAD) and in control participants without a history of psychiatric illness. As hypothesized, the EEG gamma band was useful for differentiating worry from baseline and relaxation. During worry induction, GAD patients showed higher levels of gamma activity than control participants in posterior electrode sites that have been previously associated with negative emotion. Gamma fluctuations in these electrode sites were correlated with subjective emotional experience ratings lending additional support to interpretations of negative affect. Following 14 weeks of psychotherapy, the GAD group reported less negative affect with worry inductions and the corresponding gamma sites that previously differentiated the clinical from control groups changed for the GAD patients in the direction of control participants. These findings suggest converging evidence that patients suffering from GAD experience more negative emotion during worry and that the EEG gamma band is useful for monitoring fluctuations in pathological worry expected to follow successful treatment.

Sensory gating in young children with autism: Relation to age, IQ, and EEG gamma oscillations

Unusual reactions to auditory stimuli are often observed in autism and may relate to ineffective inhibitory modulation of sensory input (sensory gating). A previous study of P50 sensory gating did not reveal abnormalities in high-functioning school age children [C. Kemner, B. Oranje, M.N. Verbaten, H. van Engeland, Normal P50 gating in children with autism, J. Clin. Psychiatry 63 (2002) 214-217]. Sensory gating deficit may, however, characterize younger children with autism or be a feature of retarded children with autism, reflecting imbalance of neuronal excitation/inhibition in these cohorts. We applied a paired clicks paradigm to study P50 sensory gating, and its relation to IQ and EEG gamma spectral power (as a putative marker of cortical excitability), in young (3-8 years) children with autism (N=21) and age-matched typically developing children (N=21). P50 suppression in response to the second click was normal in high-functioning children with autism, but significantly (p<0.03) reduced in those with mental retardation. P50 gating improved with age in both typically developing children and those with autism. Higher ongoing EEG gamma power corresponded to lower P50 suppression in autism (p<0.02), but not in control group. The data suggest that ineffective inhibitory control of sensory processing is characteristic for retarded children with autism and may reflect excitation/inhibition imbalance in this clinical group.