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The integration of direct bottom-up inputs with contextual information is a canonical motif in neocortical circuits. In area V1, neurons may reduce their firing rates when the (classical) receptive field input can be predicted by the spatial context. We previously hypothesized that gamma-synchronization (30-80Hz) provides a complementary signal to rates, encoding whether stimuli are predicted from spatial context by preferentially synchronizing neuronal populations receiving predictable inputs. Here we investigated how rates and synchrony are modulated by predictive context. Large uniform surfaces, which have high spatial predictability, strongly suppressed firing yet induced prominent gamma-synchronization, but only when they were colored. Yet, chromatic mismatches between center and surround, breaking predictability, strongly reduced gamma-synchronization while increasing firing rates. Differences between colors, including strong gamma-responses to red, arose because of stimulus adaptation to a full-screen background, with a prominent difference in adaptation between M- and L-cone signaling pathways. Thus, synchrony signals whether RF inputs are predicted from spatial context and may encode relationships across space, while firing rates increase when stimuli are unpredicted from the context.

We previously isolated a pollen-specific gene encoding a pollen tube wall-associated glycoprotein with a globular domain and an extensin domain from maize (mPex1). To evaluate which protein domains might be important for function, we isolated a second monocot gene (mPex2) and a dicot gene (tPex). Each gene encodes a signal sequence, an N-terminal globular domain comprised of a variable region, a leucine-rich repeat (LRR) with an adjacent cysteine-rich region, a transition region and an extensin-like C-terminal domain. The LRRs of the maize and tomato Pex proteins are highly conserved. Although the extensin domains in the maize and tomato proteins vary in length and in amino acid sequence, they are likely to be structurally conserved. Additional putative Pex gene sequences were identified by either GenBank search (Arabidopsis) or PCR (sorghum and potato); all encode conserved LRRs. The presence of a conserved LRR in the known and potential Pex proteins strongly suggests that this motif is involved in the binding of a specific ligand during pollen tube growth. Gene expression studies using RNA and protein blotting as well as promoter-reporter gene fusions in transient and stable transformation indicate that the tomato Pex gene is pollen-specific.

Secondary transmission remains a significant concern among HIV-infected youth. Little is known, however, about how partner-specific sexual risk behaviors for the secondary transmission of HIV may differ between the 2 largest subgroups of HIV-positive youth, women-who-have-sex-with-men (WSM) and men-who-have-sex-with-men (MSM), METHODS: During 2003-2004, a convenience sample of HIV-infected youth, 13 to 24 years of age, were recruited from 15 Adolescent Medicine Trials Network clinical sites. Approximately 10 to 15 youth were recruited at each site. Participants completed an ACASI survey including questions about sex partners in the past year. Cross-sectional data analyses, including bivariate and multivariable regressions, using generalized estimating equations, were conducted during 2008 to compare recent partner-specific sexual risk behaviors between WSM and MSM.Of 409 participants, 91% (371) were included in this analysis, including 176 WSM and 195 MSM. Ninety-two percent (163 WSM, 177 MSM) provided information on characteristics of their sexual partners. There were significant differences between the 2 groups in recent partner-specific sexual risk behaviors including: lower rates of condom use at last sex among WSM (61% WSM vs. 78% MSM; P = 0.0011); a larger proportion of the sex partners of MSM reported as concurrent (56% MSM vs. 36% WSM; P = 0.0001); and greater use of hard drugs at last sex by MSM and/or their partner (18% MSM vs. 4% WSM; P = 0.0008). When measuring risk as a composite measure of sexual risk behaviors known to be associated with HIV transmission, both groups had high rates of risky behaviors, 74.7% among young MSM compared to 68.1% of WSM.These data suggest that recent partner-specific sexual risk behaviors for HIV transmission are high among young infected MSM and WSM. These findings suggest the need to offer interventions to reduce the secondary transmission of HIV to all HIV-positive youth in care. However, differences in risk behaviors between young MSM and WSM supports population-specific interventions.