Topological Reorganization of Odor Representations in the Olfactory Bulb
(A) Left: expression of the MC marker, HuC:YC, in the glomerular/MC layer. Center: changes in rhod-2 fluorescence evoked by odor stimulation (Tyr, 10 μM) in the same view. Right: overlay (thresholded). Arrowheads depict two responsive MC somata; asterisk depicts glomerular neuropil.
(B) B1: Time-averaged raw Ca2+ signals from INs evoked by two applications of His (10 μM) and one application of Lys (10 μM). Between the first and second response to His, 17 other stimuli (His or Lys) were presented (unpublished data). r, correlation coefficient. B2: Activity maps in successive time windows after temporal deconvolution of Ca2+ signals (same trials as in B1). Each dot represents the position of one IN; colors represent the magnitude of the TDCa signal (color scale from −6 to 36; arbitrary units). Maps were low-pass spatially filtered to mimic the appearance of raw data. The position of each IN (n = 192 INs) is shown in the gray map (lower right). r, correlation coefficient.
(C) Top left: spatial pattern of time-averaged Ca2+ signals evoked by odor stimulation (food extract) in the granule cell layer. Top right: locations of all somata in the field of view (n = 45). Action potentials from neuron 1 were recorded simultaneously in the loose-patch configuration. Bottom left: reconstruction of firing-rate changes from Ca2+ signals by temporal deconvolution, exemplified by response of neuron 1. Bottom right: reconstruction of firing-rate changes from somatic Ca2+ signals of four neurons. Action potentials and firing-rate function measured by electrophysiology are overlaid for neuron 1. Bar indicates odor presentation.
(D) Temporally deconvolved Ca2+ signals of 205 MCs (blue) and 1,612 INs (green) in the same OB during odor stimulation (bar; Ala, 10 μM). Order of neurons is arbitrary. MC and IN responses are scaled differently.
(E) Estimated mean population firing rates as a function of time. Dashed lines show spontaneous firing rates determined by electrophysiological recordings.