Changing tune in auditory cortex

Abstract

Investigating the organization of tone representation in the rodent auditory cortex at high resolution, two new studies in this issue find that the arrangement of relative frequency responsiveness is not preserved at a fine-scale cortical level.

Figure 1

Tonotopy and network architecture in primary auditory cortex (A1). (a) Schematic of the classical tonotopic map. There is a smooth increase in the preferred frequency (best frequency, indicated by color) of neurons along the rostrocaudal axis. (b) Tonotopic organization of A1 was derived from two-photon imaging,. Tonotopy is present on a large scale overall, but is not maintained on a local scale. Neurons with widely varying best frequencies are often located next to each other, giving rise to a fractured map. Many neurons (open circles) show no clear best frequency or are unresponsive to simple acoustic stimuli. (c) Similarly tuned neurons in A1 form functional subnetworks that are defined by their similar frequency-tuning characteristics. Thick lines connecting similarly tuned neurons indicate substantial coactivation, possibly reflecting common thalamic inputs and/or selective interconnections. (d) Fragmentation of clustered input maps into fractured output maps as revealed by imaging with high- and low-affinity calcium indicators.