The numerical abilities of anurans and their neural correlates: insights from neuroethological studies of acoustic communication

Acoustic communication is important in the reproductive behaviour of anurans. The acoustic repertoire of most species consists of several call types, but some anurans gradually increase the complexity of their calls during aggressive interactions between males and when approached by females. In these interactions, males may closely match the number of calls or notes in a sequence that a neighbour produces, thereby revealing their numerical abilities. Anurans are also able to discern the number of sequential properly timed pulses (notes). The temporal intervals between successive pulses provide information about species identity and call type. A neural correlate of this numerical ability is evident in the responses of ‘interval-counting’ neurons, which show ‘tuning’ for intermediate to fast pulse rates and respond only after at least a threshold number of pulses have occurred with the correct timing. A single interpulse interval that is two to three times the optimal value can reset this interval-counting ...