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A 52-year-old woman with musical hallucinations was examined using brain single photon emission computed tomography (SPECT) with 99mTc-ECD. Changes in regional cerebral blood flow (rCBF) after carbamazepine treatment were assessed using a three-dimensional stereotaxic ROI template. Following treatment, rCBF was decreased in the subcortical structures and increased in the global cortical regions. From our findings, we propose that rCBF values in subcortical structures represent abnormalities similar to those reported in previous reports or other psychiatric disorders, while those in cortical regions suggest background brain dysfunctions that result in generation of musical hallucinations.

Magnetoencephalography (MEG) was used to image brain activity associated with delusions in episodic interictal psychosis of epilepsy. Two female patients aged 65 and 68 with temporal lobe epilepsy were studied during and after a delusional state. Topographic images of the excess kurtosis (g2), the statistical index of spikelike activity, were obtained from unaveraged MEG recordings using an analysis called "synthetic aperture magnetometry" (SAM). For both patients, MEG waveforms and excess kurtosis images revealed spiky activity in the right inferior parietal region during the delusional state. A second MEG measurement after delusions were resolved with antipsychotic therapy revealed no excess kurtosis in the right parietal area. Likewise, the sharp waves on MEG recordings disappeared as well. Our results suggest association of the right inferior parietal cortex, including the supramarginal gyrus, with the delusional state of episodic interictal psychosis of epilepsy.

Parallel distributed processing neuroimaging in the Stroop color word interference task in five healthy subjects was studied. The total reaction time was set at 650 ms with a time window of 200 ms in steps of 50 ms. Spatially filtered magnetoencephalography analysis, as used in synthetic aperture magnetometry, was used. Neural activation began in the left posterior parietal-occipital area (150-250 ms post-stimulus), followed by the right prefrontal polar area (250-350 ms), the left dorsolateral prefrontal cortex (250-400 ms), and the mid- to lower- primary motor area (350-400 ms). Successive and temporally overlapping activation of various cortical regions were successfully estimated within a short 200 ms time interval, contrary to previous positron emission tomography and fMRI studies., (Copyright 2002 Elsevier Science Ireland Ltd.)

In a search for the physiological correlates of mental activity, localized EEG desynchronization induced by mental arithmetic was assessed by the entropy of the EEG power spectrum (irregularity index II). The topographic mapping of II can show a localized cortical activation. Directional EEG patterns during mental arithmetic were further examined with a directed mutual information measure (information flow). These two information measures were compared between resting and mental arithmetic conditions in 10 right-handed subjects as well as one left-handed subject. II significantly increased during mental arithmetic in the left temporo-centro-parietal region in right-handed subjects, thus exhibiting its activation. Significant changes in information flow during mental arithmetic were found in the directions mostly from the temporo-centro-parietal region to other areas and within the frontal region in right-handed subjects: information flow from the left temporal and the mid-frontal areas increased and information flow mostly from the left hemisphere decreased. One left-handed subject showed greater II in right post-temporal area. These findings suggest that the left temporo-centro-parietal activation is specific to calculation processing, and the frontal information flow is related to the active performance of mental arithmetic.

Source determination of alpha activity was studied using the relative power contribution analysis (RPCA) method which allows determination of the relative contributions of different areas to the power of a certain area at different frequencies. In 20 normal subjects, EEGs were recorded from F3, F4, C3, C4, P3, P4, O1 and O2, each referenced to a linked ear. An 8-dimensional autoregressive model was fitted to the EEGs of 10.24 sec. Based on the model, RPCA was performed. For each area, alpha activity was divided into two parts: one originating in its own area (endogenous) and another in the other areas (exogenous). Endogenous alpha activity increased as the area was more posterior. In the anterior regions (frontal and central), endogenous alpha power (power of endogenous alpha activity) was small, while exogenous alpha power was large. In the posterior regions (parietal and occipital), the amount of endogenous alpha power did not differ markedly from that of exogenous alpha power. The posterior regions, which generate more endogenous alpha activity, can be considered to play a dominant role in alpha generating mechanisms. In some subjects, alpha generators with a different frequency from that of the occipital areas were observed.