Open AccessIs Human Auditory Cortex Organization Compatible With the Monkey Model? Contrary Evidence From Ultra-High-Field Functional and Structural MRI
Author(s) -
Julien Besle,
Olivier Mougin,
Rosa-María Sánchez-Panchuelo,
Cornelis P. Lanting,
Penny Gowland,
Richard Bowtell,
Susan T. Francis,
Katrin Krumbholz
Publication year - 2018
Publication title -
cerebral cortex
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.694
H-Index - 250
eISSN - 1460-2199
pISSN - 1047-3211
DOI - 10.1093/cercor/bhy267
Subject(s) - tonotopy , macaque , auditory cortex , neuroscience , biology , functional magnetic resonance imaging , human brain , cortex (anatomy) , core (optical fiber) , anatomy , physics , optics
It is commonly assumed that the human auditory cortex is organized similarly to that of macaque monkeys, where the primary region, or "core," is elongated parallel to the tonotopic axis (main direction of tonotopic gradients), and subdivided across this axis into up to 3 distinct areas (A1, R, and RT), with separate, mirror-symmetric tonotopic gradients. This assumption, however, has not been tested until now. Here, we used high-resolution ultra-high-field (7 T) magnetic resonance imaging (MRI) to delineate the human core and map tonotopy in 24 individual hemispheres. In each hemisphere, we assessed tonotopic gradients using principled, quantitative analysis methods, and delineated the core using 2 independent (functional and structural) MRI criteria. Our results indicate that, contrary to macaques, the human core is elongated perpendicular rather than parallel to the main tonotopic axis, and that this axis contains no more than 2 mirror-reversed gradients within the core region. Previously suggested homologies between these gradients and areas A1 and R in macaques were not supported. Our findings suggest fundamental differences in auditory cortex organization between humans and macaques.