The bidirectional nature of information flow in the network allows interconnected sensory neurons to modify and fine-tune each other’s receptive properties. For example, over most of its receptive field, the FLP neurons respond only to high-threshold
mechanical stimuli through its cell-autonomous MEC-10 harsh touch receptors. However, the electrical connectivity between FLP, OLQ, and CEP nose touch mechanoreceptors allows the threshold for touch sensitivity in FLP to be reduced when the CEP and OLQ neurons are active, facilitating responses to gentle nose touch. Thus, extrinsic network activity defines a gentle touch-sensitive region within the larger receptive field of FLP, which otherwise responds only to harsh touch. In this way,
coordinated activity within the nose touch network is able to partially transform the FLPs from harsh touch to gentle touch sensors. Similarly, OLQ responses to nose touch are dependent on both the Galunisertib mouse cell-autonomous activity of the OSM-9 TRPV channel as well selleck products as network inputs through RIH. Thus, lateral coupling between head mechanoreceptors allows sensory integration to occur at the most peripheral layer of the nose touch circuit, that of the sensory neurons themselves. Hub-and-spoke electrical networks present certain problems for information processing by the nervous system. In particular, how can stimuli such as nose touch and harsh touch, which appear to activate most if not all neurons in the circuit, be distinguished? Differences in neuronal dynamics may play an important role; harsh head touch for example appears to evoke longer-lasting responses in OLQ and FLP than nose touch. The magnitudes of responses in different neurons also vary; harsh head touch responses are larger than nose touch responses in FLP but of similar size in OLQ. It will be interesting to explore how these factors influence the behavioral responses to these different stimuli. The responses of whatever sensory neurons are often considered to reflect the intrinsic properties of a cell and its sensory transduction pathways. However, the importance of interactions between sensory neurons in modifying these properties
is becoming increasingly clear. In mammals, chemosensory neurons in taste buds are connected by both electrical and chemical synapses as well as by paracrine signaling (Huang et al., 2009 and Dando and Roper, 2009). Likewise, extensive gap junction coupling has been shown to occur between many cell types in the retina, including rod and cone photoreceptors (Nelson, 1977). In at least some cases, the functions of these connections parallel those in the C. elegans nose touch circuit. For example, gap junctions between low-threshold rods and higher-threshold cones can facilitate responses in cone cells in low ambient light ( Schneeweis and Schnapf, 1995), just as electrical connectivity in the nose touch circuit can facilitate gentle touch responses in the FLP nociceptors.