Incidental sounds of locomotion in animal cognition

The highly synchronized formations that characterize schooling in fish and the flight of certain bird groups have frequently been explained as reducing energy expenditure. I present an alternative, or complimentary, hypothesis that synchronization of group movements may improve hearing perception. Although incidental sounds produced as a by-product of locomotion (ISOL) will be an almost constant presence to most animals, the impact on perception and cognition has been little discussed. A consequence of ISOL may be masking of critical sound signals in the surroundings. Birds in flight may generate significant noise; some produce wing beats that are readily heard on the ground at some distance from the source. Synchronization of group movements might reduce auditory masking through periods of relative silence and facilitate auditory grouping processes. Respiratory locomotor coupling and intermittent flight may be other means of reducing masking and improving hearing perception. A distinct border between ISOL and communicative signals is difficult to delineate. ISOL seems to be used by schooling fish as an aid to staying in formation and avoiding collisions. Bird and bat flocks may use ISOL in an analogous way. ISOL and interaction with animal perception, cognition, and synchronized behavior provide an interesting area for future study

Low-frequency pitch perception in children with cochlear implants in comparison to normal hearing peers

The aim of the present study was to investigate the application of two new pitch perception tests in children with cochlear implants (CI) and to compare CI outcomes to normal hearing (NH) children, as well as investigating the effect of chronological age on performance. The tests were believed to be linked to the availability of Temporal Fine Structure (TFS) cues. 20 profoundly deaf children with CI (5-17 years) and 31 NH peers participated in the study. Harmonic Intonation (HI) and Disharmonic Intonation (DI) tests were used to measure low-frequency pitch perception. HI/DI outcomes were found poorer in children with CI. CI and NH groups showed a statistically significant difference (p < 0.001). HI scores were better than those of DI test (p < 0.001). Chronological age had a significant effect on DI performance in NH group (p < 0.05); children under the age of 8.5 years showed larger inter-subject-variability; however, the majority of NH children showed outcomes that were considered normal at adult-level. For the DI test, bimodal listeners had better performance than when listening with CI alone. HI/DI tests were applicable as clinical tools in the pediatric population. The majority of CI users showed abnormal outcomes on both tests confirming poor TFS processing in the hearing-impaired population. Findings indicated that the DI test provided more differential low-frequency pitch perception outcomes in that it reflected phase locking and TFS processing capacities of the ear, whereas HI test provided information of its place coding capacity as well

Regulator-dependent mechanisms of C3b processing by factor I allow differentiation of immune responses

The complement system labels microbes and host debris for clearance. Degradation of surface-bound C3b is pivotal to direct immune responses and protect host cells. How the serine protease factor I (FI), assisted by regulators, cleaves either two or three distant peptide bonds in the CUB domain of C3b remains unclear. We present a crystal structure of C3b in complex with FI and regulator factor H (FH; domains 1-4 with 19-20). FI binds C3b-FH between FH domains 2 and 3 and a reoriented C3b C-terminal domain and docks onto the first scissile bond, while stabilizing its catalytic domain for proteolytic activity. One cleavage in C3b does not affect its overall structure, whereas two cleavages unfold CUB and dislodge the thioester-containing domain (TED), affecting binding of regulators and thereby determining the number of cleavages. These data explain how FI generates late-stage opsonins iC3b or C3dg in a context-dependent manner, to react to foreign, danger or healthy self signals