Abstract
The antennal ear of the fruit fly detects acoustic signals in intraspecific communication, such as the courtship song and agonistic sounds. Among the five subgroups of mechanosensory neurons in the fly ear, subgroup-A neurons respond maximally to vibrations over a wide frequency range between 100 and 1,200 Hz. The functional organization of the neural circuit comprised of subgroup-A neurons, however, remains largely unknown. In the present study, we used 11 GAL4 strains that selectively label subgroup-A neurons and explored the diversity of subgroup-A neurons by combining single-cell anatomic analysis and Ca2+ imaging. Our findings indicate that the subgroup-A neurons that project into various combinations of subareas in the brain are more anatomically diverse than previously described. Subgroup-A neurons were also physiologically diverse, and some types were tuned to a narrow frequency range, suggesting that the response of subgroup-A neurons to sounds of a wide frequency range is due to the existence of several types of subgroup-A neurons. Further, we found that an auditory behavioral response to the courtship song of flies was attenuated when most subgroup-A neurons were silenced. Together, these findings characterize the heterogeneous functional organization of subgroup-A neurons, which might facilitate species-specific acoustic signal detection.
Highlights
Acoustic information is important for animal survival and reproduction in many species
We reported that Johnston’s organ (JO)-A neurons respond to acoustic stimuli in a high frequency range (>100 Hz; Kamikouchi et al, 2009; Yorozu et al, 2009; Matsuo et al, 2014)
To reveal whether the JO-A neurons show a preference to the species-specific interpulse interval (IPI), we further investigated the Ca2+ response selectivity of JO-A neurons to antennal vibrations that mimicked artificial pulse songs with various IPIs (Figure 7C)
Summary
Acoustic information is important for animal survival and reproduction in many species. Heterogeneous Auditory Neurons in Flies the increase in Ca2+ in particular subsets of JO-A neurons in response to antennal vibrations of various frequencies and IPIs. we demonstrate that the functions of all JO-A neurons together might be important in sound-induced chaining behavior. Subgroup A, B, and D-JO neurons (JO-A, JO-B, and JO-D neurons, respectively) are strongly activated by antennal vibrations and are referred to as the auditory sensory neurons in fruit flies (Kamikouchi et al., 2009; Yorozu et al, 2009). “types” of JO-A neurons have been identified, each of which is defined by its distinct projection pattern to the five subareas in zone A (Kamikouchi et al, 2006) Whether these anatomically diverse neurons have heterogeneous response properties and functions for auditory behavior, remains unknown. We evaluated the physiologic heterogeneity of these neurons by observing
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