Comparing Quantitative EEG and Low Resolution Electromagnetic Tomography Imaging between Deficit Syndrome and Non-Deficit Syndrome of Schizophrenia / 수면정신생리

OBJECTIVES: Deficit schizophrenia (DS) constitutes a disease separate from non-deficit schizophrenia (NDS). The aim of the current study was to compare the quantitative EEG and low resolution electromagnetic tomography (LORETA) imaging between DS and NDS. METHODS: This study was performed by 32 channels EEG for 42 schizophrenia patients who we categorized into DS and NDS using proxy instrument deficit syndrome (PDS). We performed the absolute power spectral analyses for delta, theta, alpha, low beta and high beta activities. We compared power spectrum between two groups using Independent t-test. Partial correlation test was performed with clinical parameters. Standardized LORETA (sLORETA) was used for comparison of cortical activity, and statistical nonparametric mapping (SnPM) was applied for the statistical analysis. RESULTS: DS showed significantly increased delta and theta absolute power in fontal and parietal region compared with NDS (p<0.05). Power spectrum showed significant correlation with 'anergia' and 'hostility/suspiciousness' subscale of brief psychiatric rating scale (BPRS)(p<0.05). sLORETA found out the source region (anterior cingulate cortex/limbic part) that delta activity was significantly increased in DS (p=0.042). CONCLUSIONS: DS showed different cortical activity compared with NDS. Our results may suggest QEEG and LORETA could be the marker in differentiating between DS and NDS.

Low-Resolution Electromagnetic Tomography (LORETA) Source Imaging Compared with Structural Brain Imaging in Patients having Organic Brain Lesion / 신경정신의학

OBJECTIVES: Patients with organic brain lesion can produce unique slow waves (delta and theta) in the EEG. Basic assumption of this study was that the low resolution electro magnetic tomography (LORETA), an inverse source localization program, can provide functional images representing increased slow wave activity in these patients compared to normal subjects. METHODS: The current study was performed by 18 channels digital EEG for 10 patients whose organic deficit have been visually confirmed by CT or MRI. The source images of slow wave (1-7 Hz) frequency were produced by LORETA-key program. RESULTS: We found that in eight out of ten subjects, LORETA successfully found out the source regions which were very closely matched to their original brain lesions. However in two subjects whose organic brain lesions were too small (<1 cm) and located out of gray matter, we failed to find any increased slow wave activity compared with normal control. CONCLUSION: We can conclude that LORETA could be a useful method to provide functional imaging in patients with gray matter deficits in their brain. Its usefulness and limitations were discussed.

Dipole Source Localization and Low Resolution Electromagnetic Tomography(LORETA) of Interictal Spikes in Mesial and Lateral Temporal Lobe Epilepsy / 대한간질학회지

PURPOSE: To investigate the usefulness of dipole source localization (DSL) and low resolution electromagnetic tomography (LORETA) in localizing epileptic focus, we performed DSL and LORETA of interictal spikes in patients with mesial and lateral temporal lobe epilepsy (TLE). METHOD: We analyzed representative interictal spikes in 17 patients with TLE (9:mesial TLE; 8:lateral TLE). We used ASA3 (Advanced Neuro Technology, Netherlands) for DSL, voltage topography (VT) and LORETA of interictal spikes. RESULT: Most interictal spikes for analysis have their maximum amplitudes at electrode F7, 8 or T7, 8 except one patient with lateral TLE (P7). In mesial TLE, VT showed a maximum negative electrical field in ipsilateral fronto-temporal region. DSL showed dipole sources in ipsilateral anterior mesial temporal lobe (33.3%, 3/9), temporal pole (44.5%, 4/9), orbitofrontal (11.1%, 1/9) and anterior inferior frontal (11.1%, 1/9) regions. LORETA showed maximum current density in ipsilateral fronto-temporal or anterior-mid temporal areas with lateral temporal maximum. In lateral TLE, dipole sources were in ipsilateral temporal pole (62.5%, 5/8), thalamus (12.5%, 1/8) and in posterosuperior temporal area (2/8, 25%). VT of spikes at F7 or F8 showed similar results as those of mesial TLE while that of spikes at T7, T8 and P7 had a tendency of electrical fields more extending to the mid- and posterior temporal regions. LORETA showed more diffuse current distribution in whole temporal lobe (anterior to posterior) with lateral temporal maximum. CONCLUSION: The patterns of DSL and LORETA were somewhat helpful to differentiate mesial from lateral TLE. LORETA usually showed more diffuse activity beyond the epileptic focus.

The P300 Source Localization in the Patients with Obsessive-Compulsive Disorder using the LORETA Imaging and SPM

OBJECTIVES: We investigated the characteristics of P300 generators in obsessive-compulsive disorder(OCD) patients by using voxel-based statistical parametric mapping of current density images. METHODS: P300 generators, produced by a rare target tone of 1500Hz under a frequent non-target tone of 1,000Hz, were measured in 15 right-handed OCD patients and 15 controls. Low Resolution Electromagnetic Tomography(LORETA), using a realistic head model of the boundary element method based on individual MRI, was applied to the 128-channel EEG. Statistical parametric mapping(SPM) was applied for the statistical analysis. RESULTS: We found that both groups had the mean current density of P300 in the parietal, temporal and prefrontal lobe. There was a trend for decreased current density in the prefrontal area in OCD patients. The statistical comparison showed current density increase in the supraparietal area, a statistically significant longer P300 latency and a trend for reduced P300 amplitude in OCD patients. CONCLUSION: It suggests that P300 source of both groups exists in multiple brain regions at the same time. And both groups had no statistically significant differences in the current density of P300 except for increased current density in the supraparietal area in OCD patients. But, considering the statistically significant longer P300 latency, a trend for reduced P300 amplitude and relative mean current density reduction in the prefrontal area in OCD patients, this study suggests that the frontal lobe may have a reduced normal inhibitory process in OCD patients.

Comparative Study between Visusal Analysis and Low Resolution Electromagnetic Tomography (LORETA) Method in the Localization of Epileptiform Discharges

BACKGROUND: LORETA (Low Resolution Electromagnetic Tomography) produces a three-dimensional current density mapping from digitized EEG (electroencephalography) data. A comparison between visual waveform analysis of scalp EEG and LORETA method may be helpful for the exact localization of epileptiform discharges. METHODS: Digital EEG data from 20 subjects showing epileptiform discharges that were localized in the left or right frontotemporal regions (F7, F8) were studied. Those EEG waves were recorded using international 10~20 system. Phase reversals in bipolar montage were converted to referential montage and waveforms were analyzed visually. Those spike waves were converted into three-dimensional potential density mapping by LORETA method and maximum negative potential density region was determined. RESULTS: The same localization in the frontotemporal region (F7, F8) between two methods was noted in 16 subjects (80.0%). The discordant localization by LORETA method was noted in 4 subjects (20.0%). In different localiza-tion subjects, their locations were frontopolar region (Fp1, Fp 2) in 2 subjects, lateral temporal region (T7, T8) in 1 and posterior temporal region (P7, P8) in 1 subject, respectively. CONCLUSIONS: Even though the localization of epileptiform discharges by visual waveform analysis is a traditional method, electrical potential density mapping by LORETA can be a useful adjunctive localization method. If detailed localization is needed, LORETA method should increase accuracy.