Frequency preference and attention effects across cortical depths in the human primary auditory cortex
Significance To the best of our knowledge, our data provide the first imaging evidence compatible with columnar processing of sound frequency in the human auditory cortex. Our study depicts the human auditory cortex with unprecedented spatial detail and demonstrates the feasibility of acquiring submillimeter functional images outside visual/motor cortices, setting the stage for a wide range of research possibilities. Our results elucidate the role of cortical layers in bottom up and top down processing of sounds, and suggest that ongoing behavioral goals shape population based sound representations especially in superficial layers of A1 columns. These results may inform and improve computational models of auditory cortical processing and may be relevant for understanding neurological conditions that do not yet have an imaging "biomarker" (e.g. tinnitus) Columnar arrangements of neurons with similar preference have been suggested as the fundamental processing units of the cerebral cortex. Within these columnar arrangements, feed forward information enters at middle cortical layers whereas feedback information arrives at superficial and deep layers. This interplay of feed forward and feedback processing is at the core of perception and behavior. Here we provide in vivo evidence consistent with a columnar organization of the processing of sound frequency in the human auditory cortex. We measure submillimeter functional responses to sound frequency sweeps at high magnetic fields (7 tesla) and show that frequency preference is stable through cortical depth in primary auditory cortex. Furthermore, we demonstrate that in this highly columnar cortex task demands sharpen the frequency tuning in superficial cortical layers more than in middle or deep layers. These findings are pivotal to understanding mechanisms of neural information processing and flow during the active perception of sounds.
Proceedings of the National Academy of Sciences