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Activity is thought to guide the patterning of synaptic connections in the developing nervous system. Specifically, differences in the activity of converging inputs are thought to cause the elimination of [...]

The development of orderly connections in the mammalian visual system depends on action potentials in the optic nerve fibers, even before the retina receives visual input. In particular, it has [...]

Researches are increasingly focusing on the development and activity of the mammalian sensory nervous system. Recent studies are directed toward understanding the impact of improving the electrical activity of cortical cells on the development of the mammalian somatosensory cortex. Study results propose that neuronal activity regulates the cortical area corresponding to a specific sensory system during development.

Choline acetyltransferase (ChAT) expressing retinal amacrine cells are present across vertebrates. These interneurons play important roles in the development of retinal projections to the brain and in motion detection, specifically in generating direction‐selective responses to moving stimuli. ChAT amacrine cells typically comprise two spatially segregated populations that form circuits in the 'ON' or 'OFF' synaptic layers of the inner retina. This stereotypic arrangement is also found across the adult human retina, with the notable exception that ChAT expression is evident in the ON but not OFF layer of the fovea, a region specialized for high‐acuity vision. We thus investigated whether the human fovea exhibits a developmental path for ON and OFF ChAT cells that is retinal location‐specific. Our analysis shows that at each retinal location, human ON and OFF ChAT cells differentiate, form their separate synaptic layers, and establish non‐random mosaics at about the same time. However, unlike in the adult fovea, ChAT immunostaining is initially robust in both ON and OFF populations, up until at least mid‐gestation. ChAT expression in the OFF layer in the fovea is therefore significantly reduced after mid‐gestation. OFF ChAT cells in the human fovea and in the retinal periphery thus follow distinct maturational paths. Human cholinergic (ChAT) amacrine cells are first observed in the fovea at early‐gestation around fetal week (Fwk) 10, and become evident across the retina with age. Characteristic ON and OFF populations of ChAT cells with processes stratifying in separate bands in the synaptic neuropil emerge in the fovea by Fwk 11, and are present as late as mid‐gestation (Fwk 20). Previous work, however, demonstrate very few, if any, OFF ChAT‐immunoreactive cells in the adult human fovea (Rodieck & Marshak,). Thus, mechanisms must act to regulate ChAT expression differentially in the ON and OFF populations as the retina matures beyond mid‐gestation. [ABSTRACT FROM AUTHOR]

Amacrine cells in the human retina can distinguish between myopic and hyperopic defocus. Myopic defocus causes increased expression of the ZENK gene, whereas hyperopic defocus inhibits ZENK expression.

Development of orientation selectivity in the visual cortex is determined by the patterns of neural activity. Stimulation of the optic nerve can activate cortical neurons as demonstrated in an experiment conducted by Weliky and Katz. Artificial synchronization of stimuli during the development stages of the visual cortex can disorient the naturally occurring patterns of neural activity resulting in a reduced specificity of orientation and direction of responses.

Key issues concerning ganglion cell type-specific loss and synaptic changes in animal models of experimental glaucoma remain highly debated. Importantly, changes in the structure and function of various RGC types that occur early, within 14 d after acute, transient intraocular pressure elevation, have not been previously assessed. Using biolistic transfection of individual RGCs and multielectrode array recordings to measure light responses in mice, we examined the effects of laser-induced ocular hypertension on the structure and function of a subset of RGCs. Among the--like RGCs studied,-OFF-transient RGCs exhibited higher rates of cell death, with corresponding reductions in dendritic area, dendritic complexity, and synapse density. Functionally, OFF-transient RGCs displayed decreases in spontaneous activity and receptive field size. In contrast, neither-OFF-sustained nor-ON-sustained RGCs displayed decreases in light responses, although they did exhibit a decrease in excitatory postsynaptic sites, suggesting that synapse loss may be one of the earliest signs of degeneration. Interestingly, presynaptic ribbon density decreased to a greater degree in the OFF sublamina of the inner plexiform layer, corroborating the hypothesis that RGCs with dendrites stratifying in the OFF sublamina may be damaged early. Indeed, OFF arbors of ON-OFF RGCs lose complexity more rapidly than ON arbors. Our results reveal type-specific differences in RGC responses to injury with a selective vulnerability of -OFF-transient RGCs, and furthermore, an increased susceptibility of synapses in the OFF sublamina. The selective vulnerability of specific RGC types offers new avenues for the design of more sensitive functional tests and targeted neuroprotection. [ABSTRACT FROM AUTHOR]

Focuses on a study which described how the neurotransmission-evoked calcium release from intracellular stores stabilizes dendrites during the period of synapse formation. Use of a ballistic labelling method to load cells with neurotransmission-evoked calcium indicator dyes; Impact of local activity on dendritic organization.