Modular Organization of Frequency Integration in Primary Auditory Cortex

Abstract

Two fundamental aspects of frequency analysis shape the functional organization of primary auditory cortex. For one, the decomposition of complex sounds into different frequency components is reflected in the tonotopic organization of auditory cortical fields. Second, recent findings suggest that this decomposition is carried out in parallel for a wide range of frequency resolutions by neurons with frequency receptive fields of different sizes (bandwidths). A systematic representation of the range of frequency resolution and, equivalently, spectral integration shapes the functional organization of the iso-frequency domain. Distinct subregions, or "modules," along the iso-frequency domain can be demonstrated with various measures of spectral integration, including pure-tone tuning curves, noise masking, and electrical cochlear stimulation. This modularity in the representation of spectral integration is expressed by intrinsic cortical connections. This organization has implications for our understanding of psychophysical spectral integration measures such as the critical band and general cortical coding strategies.

Spectral integration plasticity in cat auditory cortex induced by perceptual training

“…In cats and New World monkeys, sharpness of tuning, or local frequency specificity, to puretones represents an important functional organization principle reflected in a modular or patchy cortical organization associated with specific horizontal connections (Recanzone et al, 1999;Cheung et al, 2001;Schreiner et al, 2000;Read et al, 2001). The spatial organization of tuning to broad-band ripple spectra should be related to sharpness of tuning assessed with pure-tones since both reflect aspects of spectral filtering (Calhoun and Schreiner, 1998;Wang and Shamma, 1995).…”

Functional Subregions in Primary Auditory Cortex Defined by Thalamocortical Terminal Arbors: An Electrophysiological and Anterograde Labeling Study

“…Other functional maps in AI include binaural interaction bands (Imig and Adrian, 1977;Middlebrooks et al, 1980), threshold/intensity (Tunturi, 1950;Schreiner et al, 1992), and sharpness of tuning (Schreiner and Mendelson, 1990). Interestingly, these maps are patchy or discontinuous in their distribution relative to the frequency map Brugge and Imig, 1978;Middlebrooks et al, 1980;Reale and Imig, 1980;Redies et al, 1989;Schreiner, 1991Schreiner, , 1992Schreiner et al, 1992Schreiner et al, , 2000Mendelson et al, 1993Mendelson et al, , 1997Fitzpatrick et al, 1998).…”

Representation of Sounds in Auditory Cortex of Awake Rats (Dissertation)

“…The universally agreed upon property of primary auditory cortex is its tonotopical organization, which replicates decomposition of sounds into separate frequency components at the cochlea (Merzenich et al, , 1975Nicholls et al, 2001;Schreiner, 1995;Schreiner et al, 2000), and is preserved at the subcortical processing stations as well. Because tonotopy is such a robust feature, many studies have tried to relate responsiveness to various features to tonotopical organization.…”

“…Among features which have been mapped relative to isofrequency columns are response latency (Mendelson et al, 1997), intensity threshold (Phillips et al, 1994;Sutter and Schreiner, 1995), operating range (Heil et al, 1992a(Heil et al, , 1994, frequency modulation rate (Heil et al, 1992b;Mendelson et al, 1993), binaural response type (Imig and Adrián, 1977), sharpness of frequency tuning (Heil et al, 1992b;Schreiner and Mendelson, 1990), etc. ; see also (Ehret, 1997;Read et al, 2002;Schreiner et al, 2000) and references therein for more details. Overall, the overlap of various parameter mappings parallel and orthogonal to the tonotopic axis is usually described as the modular organization of auditory cortex (Schreiner et al, 2000), lacking the elegance and effectiveness of visual cortex organization.…”

“…; see also (Ehret, 1997;Read et al, 2002;Schreiner et al, 2000) and references therein for more details. Overall, the overlap of various parameter mappings parallel and orthogonal to the tonotopic axis is usually described as the modular organization of auditory cortex (Schreiner et al, 2000), lacking the elegance and effectiveness of visual cortex organization.…”