Uncaging also provided high spatial resolution. On average, each M/T was driven by only ∼2 neighboring MOB sites near the recording electrode (Figures 1E and 1F; mean = 2.2 sites; range 1–4). Recording locations and effective sites were close
but nonoverlapping, suggesting that M/Ts were driven superficially via their apical dendrites within glomeruli rather than by somatic activation at deeper layers (Figure S1). Correspondingly, aligning recording Alectinib in vivo locations to the most effective uncaging site revealed a spatial distribution consistent with M/Ts in one or a few activated glomeruli (Figure S1). Because each scan site could potentially overlap with >1 glomerulus in the irregular OR map, we estimated that each site activated ∼1–3 glomeruli. Locations outside the primary effective glomerulus did not drive M/T firing (Figures 1F and S1), suggesting lateral excitatory interactions between M/Ts in different glomeruli were either absent or less pronounced selleck chemicals llc than in Drosophila ( Olsen et al., 2007 and Shang et al., 2007). However, our data do not exclude subthreshold effects, inhibition, or other types of interglomerular interactions ( Arevian et al., 2008, Dhawale et al., 2010, Fantana et al., 2008 and Olsen and Wilson, 2008). Finally, uncaging activated M/Ts within different glomeruli independently ( Figure S1). Overall, photostimulation provided targeted,
high efficacy manipulation of functionally distinct MOB glomeruli, allowing us to generate highly defined MOB output. To determine how PCx neurons respond to input from individual MOB sensory channels, we recorded extracellular spikes in PCx while independently photoactivating dorsal MOB glomeruli. PCx neurons exhibited resting activity and were responsive L-NAME HCl to sensory input, firing readily to odor stimuli (Figures 2A–2D). However, single-site scanning photostimulation of MOB was ineffective at driving action
potentials in PCx (Figures 2E–2H). No MOB location tested produced reliable firing in any PCx neuron (32 neurons tested with 96 sites; ≥3 trials/site; Figure S2). The lack of uncaging responses was not due to inadequate M/T activation, as uncaging consistently drove vigorous MOB firing >100 Hz (Figure 2G). On average, uncaging produced MOB firing that exceeded that of even the most effective odorants (Figures 2C and 2G), although our relatively small odorant panel may not have maximally activated M/Ts. The lack of photostimulation responses in PCx was thus in striking contrast to odor-evoked activity. Together, these data suggest that the M/Ts within any single glomerulus provide either no input or at most subthreshold input to each PCx neuron. What accounts for the differences in PCx responses to odors and uncaging? Odors typically drive activation of multiple ORs (Malnic et al., 1999), generating distributed glomerular activity patterns in MOB (Rubin and Katz, 1999, Soucy et al., 2009, Uchida et al., 2000 and Wachowiak and Cohen, 2001).