Sex differences in 50 kHz call subtypes emitted during tickling-induced playful behaviour in rats.

‘Tickling’ induces positive affective states in laboratory rats as evidenced by the production of 50-kHz ultrasonic vocalisations (USVs), although this has mostly been investigated in males. Juvenile rats emit distinctive 50-kHz USV subtypes. Frequency-modulated (FM) 50-kHz USVs are thought to be associated with positive affect and flat 50-kHz USVs with social communication. FM and flat USVs are produced by both sexes during tickling, but it is unclear whether these calls are produced in relation to particular play-related behaviours, and whether USV subtypes are used in a sexually dimorphic manner during tickling. We tested the hypotheses that FM USVs are associated with tickle-induced play behaviours in a sex-specific way, and that flat USVs are associated with non-play activities. Rats were allocated to one of two treatment groups: tickling (tickled, n = 16/sex) or no hand contact (control, n = 16/sex). Play behaviours (hopping, darting and hand approaches) and FM and flat USVs emitted during the testing session were quantified for each rat, with the frequency of FM and flat USVs made in anticipation of, and during, each behaviour analysed. In females, play behaviours were associated with more flat USVs than in males (before and during; p < 0.001), irrespective of treatment. FM USVs were paired with hopping and darting (before and during; p < 0.001), and in anticipation of hand approaches (p < 0.001) in both tickled females and males compared to controls (both sexes) suggesting that FM USVs are linked with play behaviour. The higher call rate of flat USVs paired with play behaviour in females suggests that there may be sex differences in the role of flat USVs during play. This result is evidence of sex differences in tickle-induced behaviours and has implications for our understanding of the function of different USVs in juvenile female and male rats

Neural circuits underlying nest building in male zebra finches

SDH thanks SICB for financial support and the work described here was conducted with the support of EASTBIO DTP from the Biotechnology and Biological Sciences Research Council (BBSRC, to SE), the School of Biology and NSERC (to ZJH), MARIE CURIE (Ares(2016)5869884 to EI), and BBSRC Roslin Institute strategic grant funding (BB/P013759/1, to SLM). EN was supported by the Erasmus Plus student exchange program to SLM.Nest building consists of a series of motor actions, which are concomitant with activity in regions of the anterior motor pathway, the social behaviour network and the reward circuity in nest building adult male zebra finches (Taeniopygia guttata). It is not clear, however, whether this activity is due to nest building, collection and/or manipulation of nest material. To identify which areas of the brain are specifically involved, we used immunohistochemistry to quantify the immediate early gene c-fos in male zebra finches that were nest building (Building), birds given a nestbox but could interact only with tied down nest material (Fixed), and birds that were not given a nestbox or nest material (Control). We investigated the following brain regions: the anterior motor pathway (anterior ventral mesopallium (AMV), anterior nidopallium (AN), anterior striatium (ASt)), areas of the social behaviour network (bed nucleus of the stria terminalis, dorsomedial sub division (BSTmd), lateral septum (LS)), the dopaminergic reward circuitry (ventral tegmental area (VTA)) and the cerebellum. We found that there was greater Fos-ir expression in the BSTmd, LS and AMV with increased material deposition; in LS, AMV ASt and folia VI with increased material carrying; in LS, AMV and ASt with increased nest material tucking; and in LS and all folia (except folium VIII) with increased tugging at tied down material. These data confirm a functional role for areas of the anterior motor pathway, social behaviour network and the cerebellum in nest material collection and manipulation by birdsPostprintPeer reviewe