Many brain functions that are involved in the control of behaviour are mainly studied in animals that do not behave because they are anesthetized or restrained. This is due to the lack of adequate recording techniques for the collection of electrophysiological data in freely behaving animals and the lack of powerful algorithms to analyze these data.

One of the important models in the study of the neural control and development of higher cognitive functions is the auditory/vocal system of songbirds. The song of male songbirds is a complex learned behavior that is controlled by a network of anatomically well-defined brain areas, the so-called vocal control network. The aim of the research is to relate neuronal events in the Higher Vocal Center (HVC, one of these brain areas) with overt behaviors of the freely behaving zebra finch (Taeniopygia guttata) under changing hormonal conditions.

In order to perform this analysis, we develop a miniaturized radiotelemetry system in combination with chronically implanted electrodes and backed-up by spike sorting software already available in our department. A first prototype of the miniature radio transmitter has already been developed (Figure 1). We show preliminary data collected with this system during singing in the vocal control nucleus HVC.

For the behavioural studies, animals are housed in male-male or male-female pairs in a small shielded enclosure (1x1x1 m). Their songs and body posture during singing are recorded on DAT recorders using acoustic switches. This allows detecting artifacts in the electrophysiological recordings. Further, with the videotapes we are able to analyze the circumstances of singing, e.g. in a sexual or aggressive context and to separate electrophysiological events related to auditory input to the vocal areas from activity related to vocal production. For the sound analysis we use commercially available software (SIGNAL, Engineering Design, USA). The Observer Video-Pro (Noldus Information Technology) has been chosen as the tool for video analysis.

Figure 1. Prototype of the miniaturized transmitter. A. Songbird with transmitter. B. The transmitter itself. C. Recording (2) of electrical activity during singing.

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