We performed additional analyses to check for possible biases imposed by thresholding (>6× standard deviation of the baseline): First, we computed input across a 3 × 3 grid around the soma (Figures S6D–S6F). Second, we generated a mask by averaging the responses across cells within a group. The mask was defined by significant responses (>5× standard deviation). The mask was then used to compute input from the original maps (Figures S6G–S6I). Third, we also computed the mean pixel value over the entire map without thresholding (data not shown). These three analysis methods yielded consistent results. Since the time between stimulus and the beginning of the baseline period for the next trial was
fairly short (300 ms), we corrected for bleedthrough across trials (baseline drift). Because the grid size buy MK-1775 for stimulation was always larger than the dendritic
arbors of the recorded cells (for example, Figure 3B), we estimated the baseline drift from the traces far outside the cell’s dendritic arbor (these traces were “blanks” that could not have contained true responses; they thus represent pure baseline drift). We then subtracted the baseline selleck chemical drift from the mean value of all other traces. Paired comparisons used the nonparametric Wilcoxon signed-rank test (Figure 6 and Figure 7, S6, S7, and S9). This work was funded by the Howard Hughes Medical Institute. new We thank Gordon Shepherd for advice and extensive discussions; Asaf Keller for advice on electrical microstimulation in vM1; Tim O’Connor for programming; Brenda Shields, Amy Hu, Alma Arnold, and Kevin McGowan for technical support; Takashi Sato and Haining Zhong for help with experiments and analysis; Stefanie Kaech Petrie for help with the blind retrograde beads counting; and Diego Gutnisky and Zengcai Guo for comments on the manuscript. “
“The olfactory bulb is the first processing center of information about odorants. In mammals, the olfactory system is the
only sensory system in which peripheral information is sent directly to the cortex, bypassing the sensory thalamus. Therefore, it has been proposed that the bulb combines the function of peripheral sensory system and the thalamus (Kay and Sherman, 2007). Consistent with this proposal, several studies have demonstrated that activity in the olfactory bulb reflects not only sensory information but also the animal’s internal state (Adrian, 1950 and Rinberg et al., 2006) and task-dependent variables (Doucette and Restrepo, 2008, Fuentes et al., 2008 and Kay and Laurent, 1999). The relative simplicity of the anatomy of the olfactory bulb and the combination of both sensory- and state-dependent activity in a single network make it an attractive model for the study of principles of sensory information processing. The surface of the olfactory bulb is covered by ≈≈ 2000 glomeruli.