Acoustic pattern recognition and orientation in orthopteran insects: parallel or serial processing?

✍ Scribed by D. Helversen; O. Helversen

• Publisher: Springer
• Year: 1995
• Tongue: English
• Weight: 743 KB
• Volume: 177
• Category: Article
• ISSN: 0340-7594
• DOI: 10.1007/bf00187635

✦ Synopsis

In grasshoppers the acoustic information for pattern recognition and directional analysis is processed via parallel channels and not serially. This can be concluded from the following results established by behavioural experiments: 1. For pattern recognition the inputs from both sides are added internally. This implies that directional information is lost on this channel and must be processed in parallel. 2. The location of a female song can be influenced by introducing short clicks from both sides, forcing the grasshopper to turn to the louder resp. leading side. Also, when given a choice between two patterns of different efficiency, the grasshoppers turned towards the side with the stronger directional cues and not to the side with the more efficient pattern. 3. The parallel processing of acoustic information in grasshoppers corresponds to the evolution of acoustic communication in Acridids, as song evolved only when the ability of hearing and localization was already present. This is in contrast to crickets where the close evolutionary coupling of singing and hearing in the context of mate finding possibly favoured a serial processing of song recognition and localization.

Key words Acoustic information processing 9

Pattern recognition -Localization 9 Grasshoppers 9 Crickets recognition of the species-specific song pattern in the presence of many other acoustic signals, and localization of the sound source enabling the animal to approach phonotactically the singing partner. The neuronal correlate for recognition can be understood as a filter network, activated only by the species-specific song pattern. Orientation is based upon the differential activation of both sides caused by the directional characteristics of the auditory system. This difference in excitation, further enhanced by central neural processing, finally is weighted against each other, resulting in a turning command.

These two processes, recognition and localization, can be organized in two principally different ways, serially or in parallel. In a serial order, recognition and localization are two steps along the same information pathway, which means that the output of the recognition filters modulate the directional information. To preserve the directional information beyond filtering, two recognizers, one on each side, are required.

On the other hand, when processed in parallel, acoustic information needed for recognition and localization is handled independentely and the decisions whether a phonotactic reaction should be made (done by the filter network) and, if so, to which side (done by the localization network) are independent processes. This basic difference is outlined in Fig. .