Figure 3: Development of chronotopy.
From: Auditory cortex of newborn bats is prewired for echolocation
(a) DRAs recorded in a 3-day-old PP. Top scheme: positions of penetrations in relation to adult FM–FM area. The penetrations are numbered from 1 to 8 and corresponding DRAs are shown below with the penetration number (in white) given at bottom left. The maximum number of spikes is given at bottom right (in orange). DRAs are arranged in a rostral cluster of units responding to short delays and a caudal region with units tuned to long delays. DRA tuning width increases at longer delays. For unit 7, responses at a call level of 50 dB SPL (7b) are not delay-specific, the unit responds to echo levels of about 65–80 dB SPL. Increasing the call level to 70 dB SPL (7a) induces inhibition for up to about 5 ms echo delay, followed by delayed facilitation, which together produces a well-defined DRA. (b) Position of units with different CD (colour coded) in CP of different age. The data are pooled from 5 bats (day 0, day 7), 6 bats (day 14), 4 bats (day 21), 3 bats (day 28) and 13 bats (adult). The arrows indicate optimal direction of chronotopy towards short CDs; the P-values give the correlation probability.
