Hippocampus-dependent emergence of spatial sequence coding in retrosplenial cortex.

Retrosplenial cortex (RSC) is involved in visuospatial integration and spatial learning, and RSC neurons exhibit discrete, place cell-like sequential activity that resembles the population code of space in hippocampus. To investigate the origins and population dynamics of this activity, we combined longitudinal cellular calcium imaging of dysgranular RSC neurons in mice with excitotoxic hippocampal lesions. We tracked the emergence and stability of RSC spatial activity over consecutive imaging sessions. Overall, spatial activity in RSC was experience-dependent, emerging gradually over time, but, as seen in the hippocampus, the spatial code changed dynamically across days. Bilateral but not unilateral hippocampal lesions impeded the development of spatial activity in RSC. Thus, the emergence of spatial activity in RSC, a major recipient of hippocampal information, depends critically on an intact hippocampus; the indirect connections between the dysgranular RSC and the hippocampus further indicate that hippocampus may exert such influences polysynaptically within neocortex

Presepju u s-salib

Ġabra ta’ poeżiji u proża li tinkludi: Poeżija Maltija fi lsien barrani: Il-Vjatku ta’ Dun Karm – April ta’ R. P. – Żwieġ mhux mitmum ta’ Dun Pawl – Lil Marija ta’ Dun Karm – It-tieni safra ta’ Sandabad il-baħri maqlub għall-Malti minn Saydon – Il-presepju u s-salib ta’ Dun Karm.N/

Nofs ta' kelma

Ġabra ta’ poeżiji u proża li tinkludi: Alla kbir bla qies! ta’ R. M. B. – Tantum ergo – Lil kewkba feġġa – Għajjiena le xebagħna ta’ Ros. Briffa – Sliem ta’ Dun Karm – Kewkba ta’ Dun Karm – Nofs ta’ kelma ta’ A. C.N/

Secretory vesicles are preferentially targeted to areas of low molecular SNARE density

Intercellular communication is commonly mediated by the regulated fusion, or exocytosis, of vesicles with the cell surface. SNARE (soluble N-ethymaleimide sensitive factor attachment protein receptor) proteins are the catalytic core of the secretory machinery, driving vesicle and plasma membrane merger. Plasma membrane SNAREs (tSNAREs) are proposed to reside in dense clusters containing many molecules, thus providing a concentrated reservoir to promote membrane fusion. However, biophysical experiments suggest that a small number of SNAREs are sufficient to drive a single fusion event. Here we show, using molecular imaging, that the majority of tSNARE molecules are spatially separated from secretory vesicles. Furthermore, the motilities of the individual tSNAREs are constrained in membrane micro-domains, maintaining a non-random molecular distribution and limiting the maximum number of molecules encountered by secretory vesicles. Together our results provide a new model for the molecular mechanism of regulated exocytosis and demonstrate the exquisite organization of the plasma membrane at the level of individual molecular machines

Ottubru

Ġabra ta’ poeżiji u proża li tinkludi: Lil San Pawl ta’ Dun Karm – Il-Ġid u d-Deni ta’ J. C. – Il-Gass ta’ Dun Karm – Ħolm ir-Ramla tan-Nadur ta’ Kr. Vella Ħaber – Dawl ta’ Tama ta’ Ġużi Chetcuti – Ottubru ta’ R. P.N/