We study 4-dimensional homology cobordisms without 3-handles, showing that they interact nicely with Thurston geometries, character varieties, and instanton Heegaard Floer homologies. Using these, we derive obstructions to such cobordisms. As one example of these obstructions, generalize other recent results on the behavior knot under ribbon concordances. Finally, provide topological applicatio...

The afferent synapse between the inner hair cell (IHC) and the auditory nerve fiber provides an electrophysiologically accessible site for recording the postsynaptic activity of a single ribbon synapse. Ribbon synapses of sensory cells release neurotransmitter continuously, the rate of which is modulated in response to graded changes in IHC membrane potential. Ribbon synapses have been shown to...

A model of the ribbon synapse was developed to replicate both pre- and postsynaptic functions of this glutamatergic juncture. The presynaptic portion of the model is rich in anatomical and physiological detail and includes multiple release sites for each ribbon based on anatomical studies of presynaptic terminals, presynaptic voltage at the terminal, the activation of voltage-gated calcium chan...

Noise exposure at low levels or low doses can damage hair cell afferent ribbon synapses without causing permanent threshold shifts. In contrast to reports in the mouse cochleae, initial damage to ribbon synapses in the cochleae of guinea pigs is largely repairable. In the present study, we further investigated the repair process in ribbon synapses in guinea pigs after similar noise exposure. In...

Ribbon synapses continuously transmit graded membrane potential changes into changes of synaptic vesicle exocytosis and rely on intense synaptic membrane trafficking. The synaptic ribbon is considered central to this process. In the present study we asked whether tonically active ribbon synapses are associated with the generation of certain lipids, specifically the highly active signaling phosp...

We consider two operations on an edge of an embedded graph (or equivalently a ribbon graph): giving a half-twist to the edge, and taking the partial dual with respect to the edge. These two operations give rise to an action of S3 |E(G)|, the ribbon group, on G. The action of the ribbon group on embedded graphs extends the concepts of duality, partial duality, and Petrie duality. We show that th...

Synaptic ribbons are presynaptic protein structures found at many synapses that convey graded, "analog" sensory signals in the visual, auditory, and vestibular pathways. Ribbons, typically anchored to the presynaptic membrane and surrounded by tethered synaptic vesicles, are thought to regulate or facilitate vesicle delivery to the presynaptic membrane. No direct evidence exists, however, to in...

The goal of this study was to evaluate the mechanisms underlying Vernier acuity, over a range of spatial scales using narrow-band Vernier stimuli and oblique masking. Specifically, the test stimuli consisted of a pair of vertical ribbons of horizontal cosine grating with a vertical Vernier offset between the ribbons. These stimuli have two important advantages for studying Vernier acuity: (1) t...