Abnormal oscillatory brain dynamics in schizophrenia: a sign of deviant communication in neural network?

<p>Abstract</p> <p>Background</p> <p>Slow waves in the delta (0.5–4 Hz) frequency range are indications of normal activity in sleep. In neurological disorders, focal electric and magnetic slow wave activity is generated in the vicinity of structural brain lesions. Initial studies, including our own, suggest that the distribution of the focal concentration of generators of slow waves (dipole density in the delta frequency band) also distinguishes patients with psychiatric disorders such as schizophrenia, affective disorders, and posttraumatic stress disorder.</p> <p>Methods</p> <p>The present study examined the distribution of focal slow wave activity (ASWA: abnormal slow wave activity) in116 healthy subjects, 76 inpatients with schizophrenic or schizoaffective diagnoses and 42 inpatients with affective (ICD-10: F3) or neurotic/reactive (F4) diagnoses using a newly refined measure of dipole density. Based on 5-min resting magnetoencephalogram (MEG), sources of activity in the 1–4 Hz frequency band were determined by equivalent dipole fitting in anatomically defined cortical regions.</p> <p>Results</p> <p>Compared to healthy subjects the schizophrenia sample was characterized by significantly more intense slow wave activity, with maxima in frontal and central areas. In contrast, affective disorder patients exhibited less slow wave generators mainly in frontal and central regions when compared to healthy subjects and schizophrenia patients. In both samples, frontal ASWA were related to affective symptoms.</p> <p>Conclusion</p> <p>In schizophrenic patients, the regions of ASWA correspond to those identified for gray matter loss. This suggests that ASWA might be evaluated as a measure of altered neuronal network architecture and communication, which may mediate psychopathological signs.</p

Measurement of magnetic fields and current source localization in auditory cortical activity of rats by a 12-channel dc-SQUID gradiometer

Introduction Most of the previously reported studies on the auditory brain function of small animals used invasive techniques, such as the insertion or placement of electrodes in the cortex [1]. The invasive measurement is applied to studies on shortterm experiments because maintaining optimum conditions for a long period of time is difficult in small animals. This study focused on the noninvasive measurement and localization of the auditory cortical activation in the rat brain. The weak auditory evoked magnetic fields of up to 1 pT order with a 7.5 mm spatial resolution were measured using a 12-channel highresolution DC-SQUID magnetometer. The distribution of magnetic fields was analyzed, and the source of the auditory activity was localized by iterative minimum norm estimation (MNE) [2,3]. The global average and the histogram of the current sources were calculated statistically. 2 Experimental design Rat brain activities were measured using a 12channel SQUID gradiometer in a magn