Their sensitivity to high carrier TFs is also consistent with results from cat area 18 which we describe in the next section and human psychophysical studies (D’Antona and Shevell, 2009 and Stockman and Plummer, 1998). We also found no significant relationship between

the peak grating TFs (measured using drifting gratings at the peak grating SF) and peak carrier TFs of Y cells. The grating and carrier TF tuning curves of a Y cell along with a population scatter plot of the peak grating TFs and peak carrier TFs are shown in Figures S5C and S5D. If Y cells initiate a pathway that carries a demodulated representation of the visual scene, then there must be downstream cortical processing of this Luminespib solubility dmso nonlinear representation. To explore this, we recorded from area 18 which receives direct input from LGN Y cells (Humphrey et al., 1985 and Stone and Dreher, 1973). Many area 18 neurons respond to interference patterns (Zhou Veliparib and Baker, 1996), but it is debated whether these responses reflect the processing of subcortical Y cell input or cortical area 17 input (Demb et al., 2001b, Mareschal and Baker, 1998a and Rosenberg et al., 2010). We address this question further by examining the selectivity of area 18 neurons for carrier TF and asking whether the tuning properties are better explained

by input from Y cells or area 17. Consistent with our Y cell measurements and data from Levetiracetam a previous study that measured carrier TF tuning in a small sample of area 18 neurons (Zhou and Baker, 1996), we found that area 18 carrier TF tuning curves were diverse in shape and often broadly tuned (Figure 6). The tuning curves were also well-described

by gamma functions (average r = 0.94 ± 0.04 SD, n = 17). Using these fits to estimate tuning properties (Table 1), we found that area 18 carrier TF tuning curves were similar to those of LGN Y cells. The distributions of Y cell peak carrier TFs and area 18 peak carrier TFs were not significantly different (Kolmogorov-Smirnov test, p = 0.40; Figure 7A). The Y cell right half-heights were significantly greater than the area 18 right half-heights (two-sample t test, p = 0.01), but the two distributions were highly overlapping (Figure 7B). The population of area 18 neurons, like the Y cell population, represented the entire range of tested carrier TFs. Area 18 carrier TF tuning curves measured with the carrier drifting in opposite directions were also similar in shape (average r = 0.90 ± 0.10 SD, n = 17) and carrier direction selectivity was low (average DTI = 0.14 ± 0.10 SD, n = 17). The distributions of Y cell carrier DTI values and area 18 carrier DTI values were not significantly different (Kolmogorov-Smirnov test, p = 0.25).