Figure 8.

Hypothesized positions of auditory cortical regions coincide with probabilistic maps of koniocortical areas in humans. A, Previous neuroimaging research placed the orientation of core auditory fields along HG, with high frequencies represented medially (red “H”) and low frequencies represented laterally (blue “L”). B, Our current data confirm an orientation of core regions oblique to HG, with high and low frequencies alternating from posterior to anterior. In this scheme, our functional definition of core regions overlaps with the koniocortical/primary region Te1.0, as defined from underlying cytoarchitecture (Morosan et al. 2001; Rademacher et al., 2002), which is shown in yellow according to the Wake Forest University PickAtlas (Maldjian et al., 2003). Medial, nonprimary region Te1.1 is shown in green, the lateral region Te1.2 in orange, and Te3.0 in red. C, A map of frequency-gradient direction is shown, derived from a map of frequency preference independent of stimulus bandwidth (i.e., including responses to PT, N-BPN, and B-BPN together). White lines indicate the position of gradient reversals as in Figures 2 and 6. The hypothesized locations of the putative core, belt, and parabelt regions are marked by solid black lines, along with hypothesized subregions homologous to those identified in nonhuman primates. D, A group tonotopic map is displayed, which matches gradient map displayed in C. Data from all stimulus frequencies and bandwidths were used to create this map. Reversals that appear to delineate subregions in C remain in D. All panels display a group-average cortical surface (right hemisphere), and white dashed lines mark major sulci and gyri. Auditory subfield names are taken from the nonhuman primate literature for convenience and follow these abbreviations: R, rostral; C, caudal; M, medial; A, anterior; L, lateral belt; P, parabelt; T, temporal; p, pole. Note that “M” refers to “medial belt” when occurring as the second letter of a two-letter abbreviation (e.g., CM, caudomedial belt).