Parallel processing in auditory pattern recognition and directional analysis by the grasshopperChorthippus biguttulus L. (Acrididae)

Summary

In behavioral experiments on females of the acridid grasshopper speciesChorthippus biguttulus the relationships between pattern recognition and directional hearing were examined.

• 1. The grasshoppers displayed no capacity for direction-specific pattern recognition. That is, when two effective sound patterns were presented from different directions, superimposed in time so as to form an ineffective pattern, neither signal elicited a singing response no matter how different the directions were (Fig. 1).

• 2. The behavior of unilaterally deafened grasshoppers was used to study the attenuation of contralaterally incident sound (and to obtain a directional characteristic). With pulsed noise signals (bandwidth 3–40 kHz), the threshold curve for contralateral presentation was shifted by ca. 8 dB as compared with ipsilateral presentation (Figs. 2 and 3).

• 3. The grasshoppers responded to two ineffective patterns superimposed to form an effective pattern, even when each tympanal organ was receiving only one of the ineffective patterns (Figs. 5 and 7). Therefore the pattern of excitation that corresponds to an effective sound pattern could only be produced in neurons above the receptor level, presumably in the metathoracic ganglion. Evidently the input functions of the two tympanal organs are added (or processed in a manner equivalent to addition), before they enter the process of pattern-recognition.