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To study the human brain activity correlated with illusory perception, we chose a physically flat plane figure which looks like a convex figure. We studied visual evoked potential (VEP) changes, which reflect perceptual properties of illusory perception. We defined two paradigms, an illusory paradigm (IP) and a control paradigm (CP). Two stimuli, A and B, were randomly presented in the IP, while stimuli C and D were randomly presented in the CP. Stimulus A was the only figure which looked like a convex figure. A three-way analysis of variance was applied to the VEP components in each paradigm, with three factors: figures, electrodes, and sessions. Different configuration patterns between the two paradigms explained different grand mean VEP waveforms between the two paradigms; a greater N1 for the CP, a greater P1 for the IP, and marked attenuation of the N3 and P3 components for the IP. Significant main effects of figures only for the IP were found on P1 and P1N2 amplitude and P2 latency, which are assumed to reflect perceptual properties of stereoscopical illusory perception.

Visual event-related potentials (ERPs) were recorded during an oddball paradigm (OBP) and a simple reaction paradigm (SRP) to investigate the effect of stimulus-onset asynchrony (SOA) on ERPs under constant and random conditions in nine healthy individuals. NA was obtained by subtracting ERPs for SRP from those to the frequent nontarget of OBP. N2 was obtained by subtracting ERPs to the frequent nontarget from those to the rare target of OBP. N1, P2, and P3 latencies during OBP were shorter, and N1 amplitude of OBP, P1, and P2 amplitude of SRP, and NA amplitude were larger under constant conditions than under random conditions. We suggest that visual information processing is faster and more effective under constant conditions than under random conditions. NA potential related to the pattern recognition processing was significantly interfered with under random conditions, whereas N2 potential related to the stimulus classification was less influenced by the rhythm. The visual selective processing activity was influenced by the SOA with the positive shift of the waveform "20% rare target of OBP-100% target of SRP" under random conditions.

We investigated how visual event-related potentials (ERPs) are modulated by visual divided attention using an S1-S2 paradigm. Stimulus S2 consisted of non-target stimuli (Stimulus 1, 2, 3) and a target stimulus (Stimulus 4). The spatial/color factor was compared between S1 and S2: same/same (Stimulus 1); same/different (Stimulus 2); different/same (Stimulus 3); and different/different (Stimulus 4). The P1/N1 (90 approximately 150 ms) showed significantly greater amplitude in Stimulus 3 than in Stimuli 1 and 2. The N2 (230 approximately 290ms) showed significantly greater amplitude in Stimulus 2 than in Stimuli 1 and 3. We assumed that the P1/N1 was related to spatial attention, enhanced by alterations to the spatial factor, and that the N2 was related to color attention, enhanced by alterations to the color factor.

Spinocerebellar ataxia type 2 (SCA2) is associated with an expansion of CAG/polyglutamine-repeat of a gene of unknown function. We performed an immunohistochemical study to identify the immunolocalization of the disease protein ataxin-2 in normal and SCA2 patients. Although normal and expanded ataxin-2 were ubiquitously localized to the cytoplasm of neurons, ubiquitinated intranuclear inclusions were observed selectively in 1-2% of neurons of affected brain regions except the cerebellum. Triple-labeling immunofluorescence revealed that ataxin-2, expanded polyglutamine and ubiquitin were colocalized to these neuronal intranuclear inclusions (NIs), indicating that SCA2 shares morphological characteristics common to other neurological disorders associated with an expansion of CAG/polyglutamine-repeat. Lack of NIs in the cerebellar lesion, however, suggests the discrepancy between formation of NIs and neuronal degeneration in SCA2.