Animals can use different sensory signals to localize objects in the environment. Depending on the situation, the brain either integrates information from multiple sensory sources or it chooses the modality conveying the most reliable information to direct behavior. This suggests that somehow, the brain has access to a modality-invariant representation of external space. Accordingly, neural structures encoding signals from more than one sensory modality are best suited for spatial information processing. In primates, the posterior parietal cortex (PPC) is a key structure for spatial representations. One substructure within human and macaque PPC is the ventral intraparietal area (VIP), known to represent visual, vestibular, and tactile signals. In the present study, we show for the first time that macaque area VIP neurons also respond to auditory stimulation. Interestingly, the strength of the responses to the acoustic stimuli greatly depended on the spatial location of the stimuli [i.e., most of the auditory responsive neurons had surprisingly small spatially restricted auditory receptive fields (RFs)].Given this finding, we compared the auditory RF locations with the respective visual RF locations of individual area VIP neurons. In the vast majority of neurons, the auditory and visual RFs largely overlapped. Additionally, neurons with well aligned visual and auditory receptive fields tended to encode multisensory space in a common reference frame. This suggests that area VIP constitutes a part of a neuronal circuit involved in the computation of a modality-invariant representation of external space.

The quaternary structure and functional properties of synaptophysin, a major integral membrane protein of small presynaptic vesicles, were investigated. Cross-linking and sedimentation studies indicate that synaptophysin is a hexameric homo-oligomer, which in electron micrographs exhibits structural features common to channel-forming proteins. On reconstitution into planar lipid bilayers, purified synaptophysin displays voltage-sensitive channel activity with an average conductance of about 150 picosiemens. Because specific channels and fusion pores have been implicated in vesicular uptake and release of secretory compounds, synaptophysin may have a role in these processes.

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This article addresses how a consideration of peripheral auditory processing can help to understand experiments concerning binaural precedence that employ successive binaural transients. It appears that much of the patterning of the behavioral data is amenable to an explanation based on peripheral interactions that result from auditory filtering and the functioning of auditory hair cells in combination with a binaural model based on cross correlation. A noteworthy aspect of this approach is that it does not include inhibitory mechanisms like those commonly invoked to explain binaural precedence.

In a multicenter study more than 300 central European systemic lupus erythematosus (SLE) patients were examined for HLA-B, HLA-DR, and complement C4 phenotypes. For 174 SLE patients MHC haplotypes were determined by family segregation analysis, and for 155 patients C4 gene deletions were determined by TaqI restriction fragment length polymorphism. Two haplotypes, B8-C4AQO-C4B1-DR3 and B7-C4A3-C4B1-DR2, were identified as risk factors for SLE. These findings were confirmed by applying the haplotype frequency difference (HFD) method, which uses nontransmitted haplotypes from the family study as internal controls. Furthermore, only HLA-DR2, but not DR3, B7, or B8, was significantly increased in SLE patients independently of the two risk haplotypes. C4A gene deletions, but not silent C4AQO alleles, were increased in SLE patients and neither C4BQO alleles nor C4B gene deletions were increased. The observed frequencies of homozygosity and heterozygosity for the two haplotypes and the frequencies of homozygotes for C4AQO and C4A deletions did not differ from the expected values, indicating that the risk for SLE is conveyed by single allele effects. In conclusion, there are two MHC-linked susceptibility factors for Caucasian SLE patients carried by the haplotypes B7-DR2 and B8-DR3. The results argue against C4QO alleles being the decisive factors increasing susceptibility to SLE. (J. Clin. Invest. 1992Invest. . 90:1346Invest. -1351