Edinburgh Research Explorer Neural correlates of nesting behavior in zebra finches (Taeniopygia guttata) Citation for published version: Hall, ZJ, Bertin, M, Bailey, IE, Meddle, SL & Healy, SD 2014, 'Neural correlates of nesting behavior in zebra finches (Taeniopygia guttata)' Behavioural Brain Research, vol 264, pp. 26-33. DOI: 10.1016/j.bbr.2014.01.043
Digital Object Identifier (DOI): 10.1016/j.bbr.2014.01.043 Link: Link to publication record in Edinburgh Research Explorer Document Version: Publisher's PDF, also known as Version of record
Published In: Behavioural Brain Research Publisher Rights Statement: This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercialNo Derivative Works License, which permits non-commercial use, distribution, and reproduction in any medium, provided the original author and source are credited.
General rights Copyright for the publications made accessible via the Edinburgh Research Explorer is retained by the author(s) and / or other copyright owners and it is a condition of accessing these publications that users recognise and abide by the legal requirements associated with these rights. Take down policy The University of Edinburgh has made every reasonable effort to ensure that Edinburgh Research Explorer content complies with UK legislation. If you believe that the public display of this file breaches copyright please contact [email protected]
providing details, and we will remove access to the work immediately and investigate your claim.
Download date: 23. Jan. 2018
Behavioural Brain Research 264 (2014) 26–33
Contents lists available at ScienceDirect
Behavioural Brain Research journal homepage: www.elsevier.com/locate/bbr
Neural correlates of nesting behavior in zebra ﬁnches (Taeniopygia guttata)夽 Zachary J. Hall a,∗ , Marion Bertin a , Ida E. Bailey a , Simone L. Meddle b , Susan D. Healy a a b
School of Biology, University of St. Andrews, Harold Mitchell Building, St. Andrews, KY16 9TH Scotland, United Kingdom The Roslin Institute, The Royal (Dick) School of Veterinary Studies, The University of Edinburgh, Easter Bush, EH25 9RG Scotland, United Kingdom
h i g h l i g h t s • • • • •
We compare markers of neural activity to nesting behavior in zebra ﬁnches. We visualized immediate early gene (Fos) expression in nesting and control ﬁnches. Fos production in motor, social, and reward neural circuits correlated with nesting. Fos production correlated with material pick-up in male nesting ﬁnches. Fos production correlated with time spent in the nest in female nesting ﬁnches.
a r t i c l e
i n f o
Article history: Received 20 November 2013 Received in revised form 28 January 2014 Accepted 28 January 2014 Available online 4 February 2014 Keywords: Nesting behavior Nest building C-fos anterior motor pathway Zebra ﬁnch
a b s t r a c t Nest building in birds involves a behavioral sequence (nest material collection and deposition in the nest) that offers a unique model for addressing how the brain sequences motor actions. In this study, we identiﬁed brain regions involved in nesting behavior in male and female zebra ﬁnches (Taeniopygia guttata). We used Fos immunohistochemistry to quantify production of the immediate early gene protein product Fos (a molecular indicator of neuronal activity) in the brain correlated this expression with the variation in nesting behavior. Using this technique, we found that neural circuitry involved in motor sequencing, social behavior, reward and motivation were active during nesting. Within pairs of nesting birds, the number of times a male picked up or deposited nesting material and the amount of time a female spent in the nest explained the variation in Fos expression in the anterior motor pathway, social behavior network, and reward neural circuits. Identiﬁcation of the brain regions that are involved in nesting enables us to begin studying the roles of motor sequencing, context, and reward in construction behavior at the neural level. © 2014 Elsevier B.V. All rights reserved.
1. Introduction Abbreviations: AH, anterior hypothalamus; ASt, anterior striatum; AMV, anterior ventral mesopallium; AN, anterior nidopallium; BSTl, bed nucleus of the stria terminalis, lateral subdivision; BSTmd, bed nucleus of the stria terminalis, dorsomedial subdivision; BSTmv, bed nucleus of the stria terminalis, ventromedial subdivision; dHP, dorsal hippocampus; DLN, dorsolateral nidopallium; GCt, central gray; LAI, lateral intermediate arcopallium; LScv, lateral septum, ventral caudal subdivision; LScvl, lateral septum, lateral ventral caudal subdivision; LSr, lateral septum, rostral subdivision; mHP, medial hippocampus; MS, medial septum; NIML, nidopallium intermedium medialis pars laterale; PBS, phosphate-buffered saline; POM, medial preoptic area; RA, robust nucleus of the arcopallium; TnA, nucleus taeniae; VMH, ventromedial hypothalamus; VTA, ventral tegmental area. 夽 This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial-No Derivative Works License, which permits non-commercial use, distribution, and reproduction in any medium, provided the original author and source are credited. ∗ Corresponding author. Tel.: +44 07794 121503. E-mail addresses: [email protected]
(Z.J. Hall), [email protected]
(I.E. Bailey), [email protected]
(S.L. Meddle), [email protected]
(S.D. Healy). 0166-4328/$ – see front matter © 2014 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.bbr.2014.01.043
Nest building in birds consists of a sequence of motor actions, which in its simplest form involves the collection and deposition of nesting material. For some species nest building can be decomposed into just a few actions while for others the construction of some nests is more elaborate. For example, arctic terns (Sterna paradisaea) nest in unadorned ground scrapes whereas long-tailed tits (Aegithalos caudatus) sequence up to 14 motor actions to construct their domed nest of moss and spider egg cocoons . Superﬁcially at least, nest building appears to involve motor actions and sequencing akin to those used in tool manufacture and use [2–5] but to date there is little information regarding the neural underpinnings of these behaviors in birds. In this study, we sought to investigate the neurobiology of nest building in zebra ﬁnches (Taeniopygia guttata). Zebra ﬁnches readily construct nests in the laboratory [6–8] using an easily-quantiﬁed motor sequence of nest material collection and deposition. While
Z.J. Hall et al. / Behavioural Brain Research 264 (2014) 26–33
the male zebra ﬁnch collects and deposits nest material, the female manipulates material to shape a species-typical dome nest . To identify brain regions involved in nesting behavior, we quantiﬁed the production of the immediate early gene c-fos protein product Fos (a molecular indicator of neuronal activity; e.g. [10,11]) throughout the brain in male and female zebra ﬁnches that did or did not construct a nest. We quantiﬁed Fos immunoreactivity in the anterior motor pathway, which is thought to control motor learning and sequencing  and includes the striatum, the input structure of the basal ganglia. The basal ganglia control motor planning and sequencing in vertebrates  and are activated during trained tool use in macaque monkeys . In this study, we tested the hypothesis that nest building involves motor planning and predicted that Fos immunoreactivity in the anterior motor pathway would correlate with nest-building behavior in male zebra ﬁnches. We also predicted that Fos expression would not differ between nest-building and control birds (birds that were not allowed to build nests) in the posterior motor pathway, a circuit that is involved in the production of motor actions , as both nesting and control birds could move freely. As the social behavior network contains brain regions involved in avian reproductive and parental behavior (e.g. ) we quantiﬁed Fos expression in those regions. Based on the recent demonstration of the involvement of vasotinergic neural circuitry in female zebra ﬁnch nesting behavior  and that nest box possession in starlings increases Fos expression in the social behavior network , we predicted that Fos immunoreactivity speciﬁcally in BSTmd, BSTmv, AH, POM, and VMH would be higher in nesting birds relative to control birds. While Heimovics and Riters  noted that starlings that possessed a nest box also constructed nests they did not quantify nesting behavior and so were unable to test whether nest building was associated with Fos production in the social behavior network. By quantifying nest-building behavior, we could test whether Fos production in these regions during nest building is associated with nest possession or nest building itself. Based on the assumption that nesting is a rewarding behavior we predicted that Fos expression in the dopaminergic reward circuit, which is involved in reward and motivation of motor behavior , would correlate with nesting behavior. We expected to see this correlation speciﬁcally in VTA and GCt, two dopaminergic reward nuclei in which nest box possession in starlings leads to increased Fos immunoreactivity [19,20]. Lastly, as the avian hippocampus is implicated in spatial memory and in synthesizing multimodal cues, we tested whether the hippocampus was involved in initiating nest building after recognizing a reproductive context [21,22].
2. Methods and materials 2.1. Animals Thirty-two adult zebra ﬁnches (Taeniopygia guttata; n = 16 male, n = 16 female) were bred in captivity at the University of St. Andrews, St. Andrews, Scotland, UK and the University of Glasgow, Glasgow, Scotland, UK. All of the males had previously built nests using coconut ﬁber . Prior to experimentation, birds were housed in single sex groups in cages containing 10–20 birds with access to ﬁnch seed mix and water ad libitum but deprived of access to coconut ﬁber. The room was held on 14L:10D light:dark light cycle (lights on 8:00) with temperatures ranging between 19–27 ◦ C and 50–70% humidity. All procedures were performed with ethical permission from the University of St Andrews Animal Welfare and Ethics Committee and from the UK Home Ofﬁce (PPL. 60/3666).
2.2. Treatment group assignment In preparation for the experiment, zebra ﬁnches were caught from group cages and randomly paired (one bird of each sex) in wooden/wire mesh cages (44 × 30 × 39 cm), which were then moved to a separate room (holding only paired ﬁnches) with the same light cycle, temperature, and humidity as the grouphousing room. The cages were ﬁtted with a wooden nesting cup (11 × 13 × 12 cm) and the ﬂoor was covered with wooden bedding chips. The birds had access to ﬁnch seed mix and water ad libitum. Birds were paired for at least one week before they were provided with coconut ﬁber as nesting material. Prior to receiving nesting material, all pairs ﬁlled their nest cup with bedding chips from the cage ﬂoor at least once and some females laid eggs in these nests. All bedding and eggs were removed from nest cups after daily inspection. At least one week after pairing, six pairs of birds were given 7.5 g of coconut ﬁber at 12:00 (4 h after lights on). We inspected cages on the following day at 12:00 to identify pairs that had begun depositing material in the nest cup. To create an experimental cohort, we randomly assigned a pair of ﬁnches that had begun building a ﬁber nest to each behavioral treatment group (nesting or non-nesting control group). To ensure that all of the ﬁnches included in this study were motivated and capable of building nests prior to behavioral observation for both nesting and control groups we selected only pairs of birds that had begun nest building. We removed nests and remaining ﬁber from the cages of both pairs and the nest cup from the cage of the control pair. We also removed the cage bedding chips and lined the cage ﬂoor with black plastic to prevent unwanted nest building with bedding. The two pairs were then moved to an isolation room.
2.3. Isolation of nesting behavior Once in the isolation room, the control and experimental pairs were visually but not acoustically isolated from each other by a wooden barrier. On the next morning, 1 h after lights on, we gave the nesting pair 12 g of coconut ﬁber and monitored them throughout the day for evidence of nest building. If the nesting pair began constructing a nest within the day they received nesting material, we scheduled the behavioral observation period for the next morning. If the nesting pair failed to construct a nest on the ﬁrst day we provided the material, we replaced the 12 g of coconut ﬁber the next morning and monitored the nesting male for the remainder of the day. If a nesting male failed to deposit any material in the nest cup within two days of material provision, the nest cup and material were removed and a new nest cup and 12 g of coconut ﬁber were given to the control pair, reversing the treatment assignment of each pair in the cohort. Reversal of treatment conditions occurred twice and in one case, neither male constructed a nest while in the isolation room. These birds were removed from the study and replaced by a subsequent cohort. We removed unused nest material when the lights came on the morning after a nesting pair began nest building in the isolation room. Both pairs were left for 30 min before we began ﬁlming. After 30 min, we gave the nesting pair 9 g of coconut ﬁber so that the male could resume nest building and we ﬁlmed each pair using either a JVC Everio ACVHD (Model no. GZ-HD300AU) or Sony Handycam AVCHD (Model no. HDR-CX115E) camcorder. Nest-building males did not typically resume construction immediately so we observed the birds from outside the isolation room via a window until we observed the nesting male make three consecutive trips with material from the cage ﬂoor to the nest. We recorded the time at which the male began to build.
Z.J. Hall et al. / Behavioural Brain Research 264 (2014) 26–33
2.4. Behavior coding We encoded the birds’ behavior using Noldus Observer (TrackSys Ltd., Nottingham, UK) behavioral analysis software. We measured the occurrence of ﬁve behaviors that were performed by all of the birds: hopping (a jump between perches, the cage ﬂoor, and/or the nesting cup), feeding (pecks into the ground or cagemounted feeder), drinking (pecks into the cage-mounted water dispenser), preening (each preen of the chest, wing, or tail feathers by the beak), and scratching (bird lifts leg and scratches head feathers with foot). In females, we also recorded allopreening (each time the female preened her partner male with her beak). In males, we assessed singing behavior in two ways: song bouts (number of song bouts separated by at least 3 s) and time spent singing (number of seconds a bird spent singing). We measured two behaviors unique to the nesting males: pick up (male picked up coconut ﬁber from the ﬂoor of the cage using his beak) and put down (male released coconut ﬁber into the nest cup). In both nesting males and females, we counted the number of nest visits (bird entered the nest cup) and nest time (number of seconds the bird spent in nest cup).
2.5. Tissue collection After 90 min following the initiation of nest building, an experimenter entered the room to conﬁrm visually that material on the ﬂoor of the cage had been added to the nest. Once conﬁrmed, both pairs of control and experimental birds were terminally anaesthetized (0.2 ml Pentobarbitone sodium i.p.; Dolethal, Vétoquinol) and brains were rapidly dissected from the skull. Brains were ﬁxed via submersion in 4% paraformaldehyde in PBS (0.1 M, pH 7.4) for six days and cryoprotected in 20% sucrose in PBS for 48 h. The brains were then embedded in quail egg yolk, which was subsequently ﬁxed with 4% paraformaldehyde over six days. The embedded brains were sectioned coronally (section thickness = 30 m) using a freezing microtome and sections were collected in three, alternating series (intersection interval = 90 m) into 0.1 M PBS. We repeated all of these procedures until we had observed behavior of, and collected brains from, eight nesting pairs and eight control zebra ﬁnch pairs.
2.6. Fos immunohistochemistry We rinsed sections three times in 0.1 M PBS before being incubated in 0.5% H2 O2 in 0.1 M PBS for 30 min at room temperature to reduce endogenous peroxidase activity. Following another three 0.1 M PBS rinses, we incubated sections in 10% Normal Goat Serum (Vector Laboratories) in 0.3% Triton X-100 (Sigma) in 0.1 M PBS (PBS-T) for 60 min at room temperature. We then removed sections from the blocking serum into the primary Fos antibody (rabbit-antiFos antibody diluted 1:1000 in PBS-T, Santa Cruz Biotechnology K-25) and incubated for 21 h at room temperature. This antibody has previously been validated for use in the zebra ﬁnch (see Ref. ). The following day, we rinsed sections three times in 0.1% PBS-T and incubated in biotinylated goat anti-rabbit secondary antibody (diluted 1:250 in 0.3% PBS-T; Vector Laboratories) for 1 h at room temperature. After three rinses in 0.1% PBS-T, we incubated sections at room temperature in ABC Elite avidinbiotin horseradish-peroxidase complex (Vector Laboratories) for 1 h. Following three rinses in 0.1% PBS-T we visualized the antibodyavidin-biotin complexes with 0.04% diaminobenzidene solution (Sigma Fast DAB) for 90 s and then rinsed 4 times with 0.1 M PBS. We then serially mounted tissue sections on to Polysine microscope slides (VWR), serially dehydrated through alcohol (50–100%),
cleared in xylene, and cover-slipped with DePeX (VWR). We found no immunoreactivity when we omitted the primary antibody. 2.7. Quantiﬁcation of Fos immunoreactivity In males, we quantiﬁed the number of nuclei expressing Fos in HVC and RA in the song-control system. We also quantiﬁed Fos immunoreactivity in LAI and DLN of the posterior motor pathway and AMV, AN, and ASt of the anterior motor pathway as identiﬁed in Feenders et al. . In the social behavior network, we quantiﬁed Fos immunoreactivity in brain regions previously reported to increase immediate early gene expression with nest box possession in starlings: BSTmd, BSTmv, AH, POM, and VMH [17,20]. We also quantiﬁed Fos immunoreactivity in the social behavior network in two other divisions of the bed nucleus of the stria terminalis (BSTmv, BSTl), four divisions of the septum (LScv, LScvl, LSr, MS), and TnA as identiﬁed by Goodson  and Heimovics and Riters . Because BSTmd and BSTmv have been found to both increase Fos immunoreactivity with nest box possession but are differentially inﬂuenced by breeding condition , we opted to sample these subdivisions separately, unlike a recent study testing for a role of vasotinergic neuron populations in BSTm in nesting . We quantiﬁed Fos immunoreactivity in two regions of the hippocampus (dHP and mHP). In the dopaminergic reward/motivation circuit, we quantiﬁed Fos immunoreactivity in VTA and GCt. We located areas of interest in brains using full section architecture and regional anatomy with reference to brain atlases of the canary  and zebra ﬁnch . At each area of interest, we inspected adjacent coronal sections to locate the midpoint of the region in the rostrocaudal axis (Fig. 1). We took images of each region in both hemispheres and across 3 consecutive coronal sections centered on the rostrocaudal midpoint of the region (intersection interval = 90 m). Regions larger in the rostrocaudal plane (ASt, dHP, and mHP) were quantiﬁed across 5 evenly-spaced coronal sections centered on the rostrocaudal midpoint of the region with an intersection interval of 270 m. Images were taken using a Nikon Coolpix E4500 digital camera mounted on a Leitz Diaplan microscope using a 40× objective lens and Leitz Wetzlar 307148.001 light source. During quantiﬁcation, each image was opened in ImageJ software (version 1.45, NIH, Bethesda, MD, USA) and desaturated. To isolate Fos nuclei from background staining, we used the auto levels function in ImageJ, which saturates a lack of Fos immunoreactivity as white and saturates Fos immunoreactivity as black. Before applying the function to each image, we subtracted 40 units from the auto levels adjustment value. An experimenter blind to bird treatment conﬁrmed that this subtraction reliably highlighted darkly-stained Fos nuclei from background staining in a set of randomly selected images from multiple birds and brain regions. In the anterior motor pathway regions (ASt, AN, and AMV), only 30 units were subtracted from the auto levels value as the same experimenter (blind to bird treatment) found that neuropil staining was notably lighter and better excluded using this modiﬁed levels manipulation. After applying this function, the number of highlighted Fos immunoreactive nuclei were counted using the analyze particles function in ImageJ. Nuclei were counted if they had a minimum area of 400 pixels2 . This value was selected by an experimenter blind to bird treatment by measuring the area of the smallest Fos immunoreactive nuclei identiﬁed in multiple, randomly-selected regions across birds and brain regions. The number of Fos immunoreactive nuclei in each hemisphere and section were summed to yield a single value for each brain region in each bird. Total Fos immunoreactive nuclei counts for each brain region were used in statistical analysis except for HVC as lateralization in activation in the right hemisphere has been previously reported during short-distance communication with a sexual partner in zebra ﬁnches . In
Z.J. Hall et al. / Behavioural Brain Research 264 (2014) 26–33
beak mH P
MD MV A MV AN
and treatment on two levels (nesting and control). For the Fos data, we looked speciﬁcally for treatment and treatment x sex interaction effects that reﬂected neural activity associated with nesting. To investigate whether nesting behaviors explain individual variation in Fos production, we entered all recorded behaviors in nesting birds as independent predictors of Fos immunoreactive nuclei quantiﬁed in each brain region using multiple linear regression. We ran regression models separately for males and females using a stepwise reduction procedure excluding interactions between types of behavior. In the song control nuclei (HVC and RA), we entered singing behavior (song bouts and time spent singing) as predictors of Fos immunoreactive nuclei counts in all males (nesting and control) ﬁrstly to test for song-brain correlations as previously reported  and secondly to test for a relationship between Fos immunoreactivity and the variation in the birds’ behavior.
LSr LScv MeS LScvl BSTl BSTmd BSTmv POM AH VMH
Regressional models in which nesting behavior signiﬁcantly explained variation in Fos production in a brain region are summarized in Table 1. 3.1. Behavioral analyses
RA LAI A
Fig. 1. Brain regions quantiﬁed for Fos immunoreactivity in the zebra ﬁnch brain. Drawing of three transverse brain sections (1–3) and their locations along the sagittal plane (top diagram) depicting all regions quantiﬁed bilaterally for Fos immunoreactivity in this study. Black squares on the left hemisphere represent sampling squares taken at 40× objective magniﬁcation and brain region acronyms are located in the relative position of the sampling square in the right hemisphere.
Between 80-50 min prior to sacriﬁce, control birds hopped (F1,26 = 22.623, p < 0.001), fed (F1,26 = 9.617, p = 0.005), drank (F1,26 = 7.296, p = 0.012) and preened (F1,26 = 6.049, p = 0.021) more than did nesting birds. Males scratched more often than did females (F1,26 = 20.362, p < 0.001). Control females tended to allopreen more than did nesting females (t13 = 1.991, p = 0.087). Nesting and control males did not signiﬁcantly differ in the time they spent singing (p > 0.05). In nesting pairs, males visited the nest cup more often than did females (t12 = 6.128, p < 0.001) but did not spend more time in the nest cup (p > 0.05). Time spent singing was positively correlated with Fos immunoreactivity in the right (ˇ = 0.692, t = 3.457, p = 0.004) but not in the left hemisphere (p > 0.05) in all males. Neither the number of song bouts nor time spent singing signiﬁcantly explained variation in Fos expression in RA (all p > 0.05). 3.2. The motor pathways
HVC, we analyzed Fos immunoreactivity in the left and right hemispheres separately. 2.8. Statistical analysis During the behavioral analysis, one pair of nesting ﬁnches was identiﬁed as an outlier as the male picked up only small amounts of nest material (<2 SD below the mean for the rest of nesting males) and the female was never observed interacting with the nesting material within the nest cup. As a result we excluded this pair from further statistical analysis. All statistical analyses were performed using PASW software (version 19.00, SPSS Inc., Chicago, IL, USA). We quantiﬁed ﬁnch behavior 80–50 min prior to sacriﬁce. The delay between quantiﬁed behavior and sacriﬁce provided sufﬁcient time for the accumulation of Fos protein following neural activation associated with nesting . All behavior and Fos data were normally distributed (p > 0.05; Shapiro–Wilk). We compared behavior and Fos immunoreactivity counts as dependent variables using GLMs and the independent variables included sex on two levels (male and female)
The number of times males picked up pieces of nesting material (Fig. 2; ˇ = 0.808; t = 3.070; p = 0.028) was positively correlated with variation in Fos immunoreactivity in ASt. The number of times the males picked up material (Fig. 2; ˇ = 0.801; t = 6.451; p = 0.003) and time spent singing (ˇ = 0.459; t = 3.696; p = 0.021) were both positively correlated with the variation in Fos immunoreactivity in AN. The number of times the males picked up material (Fig. 2; ˇ = 0.807; t = 3.061; p = 0.028) was positively correlated with variation in Fos immunoreactivity in AMV. Variation in nesting behaviors did not explain the variation in either of the areas we quantiﬁed from the posterior motor pathway, LAI or DLN (p > 0.05). In nesting females, neither the number of visits to the nest nor the time spent in the nest signiﬁcantly explained the variation in Fos immunoreactivity in either the anterior or posterior motor pathway (p > 0.05). We also found no signiﬁcant difference in Fos immunoreactivity between nesting and control birds in either the anterior or posterior motor pathway (p > 0.05).
Z.J. Hall et al. / Behavioural Brain Research 264 (2014) 26–33
Table 1 Nesting behavior correlates of Fos production in brain regions of adult zebra ﬁnches. Correlates were calculated using stepwise linear regression to identify behaviors performed by adult nesting zebra ﬁnches 50–80 min before sacriﬁce that predicted Fos production in sampled brain regions. When regression models included more than one behavior predicting Fos production in a single brain region, each behavior in the model is listed in the order of predictive power. Nesting behaviors are represented in bold. Brain Region Motor pathways Anterior striatum Anterior nidopallium Anterior nidopallium Anterior ventral mesopallium Social behavior network Anterior hypothalamus Bed nucleus of the stria terminalis, ventromedial subdivision Bed nucleus of the stria terminalis, ventromedial subdivision Medial septum Dopaminergic reward circuit Ventral tegmental area
ASt AN AN AMV
Male Male Male Male
Pick up Pick up Time spent singing Pick up
0.808 0.801 0.459 0.807
3.070 6.451 3.696 3.061
0.028 0.003 0.021 0.028
AH BSTmv BSTmv MS
Female Female Female Male
Time in nest Time in nest Preening Put down
−0.771 1.043 0.595 −0.795
−2.711 5.399 3.079 −2.928
0.042 0.006 0.037 0.033
3.3. The social behavior network The more pieces of material the males deposited in the nest cup the less Fos immunoreactivity we observed in MS (Fig. 3; ˇ = −0.795; t = −2.928; p = 0.033). Fos immunoreactivity was higher in LScv and lower in VMH the more time nesting males spent singing (LScv: ˇ = 0.928; t = 5.555; p = 0.003; VMH: ˇ = −0.792; t = −2.899; p = 0.034). Fos immunoreactivity in LSr was lower the more times nesting males hopped (Fig. 3; ˇ = −0.778; t = −2.771; p = 0.039) while neither picking up nor depositing nest material signiﬁcantly explained variation in Fos immunoreactivity in any of the other social behavior network regions that we quantiﬁed (p > 0.05).
Fos immunoreactivity in AH decreased with increasing amount of time nesting females spent in the nest (Fig. 3; ˇ = −0.771; t = −2.711; p = 0.042). Fos immunoreactivity in BSTmv, however, was higher the more time these females spent in the nest (Fig. 3; ˇ = 1.043; t = 5.399; p = 0.006) and the more time they spent preening (ˇ = 0.595; t = 3.079; p = 0.037). Fos immunoreactivity in VMH was higher the less time the nesting females spent preening (ˇ = −0.861; t = −3.790; p = 0.013). Neither the number of times these females visited the nest nor the time these females spent in the nest signiﬁcantly explained variation in Fos immunoreactivity in any other social behavior network regions quantiﬁed (p > 0.05).
Fig. 2. Correlations between nest-building behaviors and Fos immunoreactivity in the anterior motor pathway in zebra ﬁnches. Lines represent signiﬁcant correlations between the picking up of nesting material and the number of Fos immunoreactive nuclei quantiﬁed in regions within the anterior motor pathway (p < 0.05) in adult male zebra ﬁnches. Correlations were derived from stepwise linear regressions. Within each graph, the regression coefﬁcient and p value of the model are presented in the top left corner. Micrographs of sampling squares taken in tissue stained to label neurons producing Fos in ASt in the right hemisphere of a male ﬁnch who picked up the most and a male ﬁnch who picked up the least amount of material while constructing a nest (bottom right). Scale bar represents 50 m. ASt = anterior striatum; AN = anterior nidopallium; AMV = anterior ventral mesopallium.
Z.J. Hall et al. / Behavioural Brain Research 264 (2014) 26–33
Fig. 3. Correlations between nesting behaviors and Fos immunoreactivity in the social behavior network. Lines represent signiﬁcant correlations between nesting behaviors (the depositing of nesting material in males and the time spent in the nest cup in females) and the number of Fos immunoreactive nuclei in bed nucleus of the stria terminalis, medioventral division (p < 0.05). Correlations were derived from stepwise linear regressions. Within each graph, the regression coefﬁcient for the behavior and model p value are presented. Micrographs of sampling squares taken in tissue stained to label neurons producing Fos in BSTmv in the right hemisphere of a female ﬁnch who spent the most time in her nest and a female ﬁnch who spent the least amount of time in her nest (bottom left). Scale bar represents 50 m.
Fos immunoreactivity in BSTmd (F1,23 = 4.720, p = 0.040) and POM (F1,25 = 8.095, p = 0.009) was signiﬁcantly greater in nesting birds relative to control birds. There was no signiﬁcant difference in Fos immunoreactivity between nesting and control birds in any other region sampled (p > 0.05).
3.4. The dopaminergic reward system Fos immunoreactivity in VTA increased with the number of times the nesting males picked up pieces of nest material (Fig. 4; ˇ = 0.789; t = 2.870; p = 0.035). Conversely, variation in nesting behavior did not signiﬁcantly explain variation in Fos immunoreactivity in GCt (p > 0.05). Neither the number of times the nest was visited nor the time spent in the nest by the nesting females signiﬁcantly explained variation in Fos immunoreactivity in VTA or GCt (p > 0.05). Fos immunoreactivity in VTA and GCt did not differ between nesting and control birds (p > 0.05). 3.5. Hippocampus Nesting behavior and Fos immunoreactivity in dHP and mHP were not correlated (p > 0.05). We also found no signiﬁcant differences in Fos immunoreactivity in dHP and mHP between nesting and control birds (p > 0.05). 4. Discussion Using immediate early gene immunohistochemistry, we have identiﬁed regions of the songbird brain that produce Fos during nest building. This Fos production presumably is reﬂecting neural activation  within the anterior motor pathway, social behavior network, and dopaminergic reward system as Fos immunoreactivity was positively correlated with the number of times nest material was picked up by nest-building males or with the time spent in the nest cup by nesting females. This is the ﬁrst demonstration of neural correlates of nest-building behavior in the anterior motor pathway and dopaminergic reward circuit. 4.1. Motor pathways
Fig. 4. Correlations between nest-building behaviors and Fos immunoreactivity in the dopaminergic reward system. Lines represent signiﬁcant correlations between the picking up of nesting material and the number of Fos immunoreactive nuclei quantiﬁed in the ventral tegmental area (p < 0.05) in adult male zebra ﬁnches. Correlations were derived from stepwise linear regressions. Within the graph, the regression coefﬁcient for the behavior and model p value are presented. Micrographs of sampling squares taken in tissue stained to label neurons producing Fos in the ventral tegmental area in the right hemisphere of a male ﬁnch who picked up the most and a male ﬁnch who picked up the least amount of nesting material while constructing a nest (right). Scale bar represents 50 m.
The number of times a male ﬁnch picked up nest material explained variation in Fos production throughout the anterior, but not posterior, motor pathway. Given the involvement of the anterior motor pathway in motor learning and sequencing , activation of the anterior motor pathway, and ASt in particular, during nest building suggests that nest-building behavior may involve similar motor control as has been ascribed to tool use behavior (which activates the basal ganglia in primates: ). Fos production in the anterior motor pathway was, however, speciﬁcally related
Z.J. Hall et al. / Behavioural Brain Research 264 (2014) 26–33
to initiation of the sequence of nest-building behavior (picking up material) but not to the ﬁnal step in the behavioral sequence that we were able to quantify (depositing material in the nest). This suggests that the AN in the zebra ﬁnch brain (as identiﬁed by ) is functionally similar to NIML in the pigeon brain (as identiﬁed by Ref. ), which plays a role in initiating learned motor sequences. Conversely, the number of visits the females partnered to nestbuilding males made to the nest and time they spent in the nest cup were unrelated to Fos immunoreactivity in the anterior motor pathway. This sex difference suggests that, during nest building, the anterior motor pathway is speciﬁcally involved in the collection of nest material and not construction within the nest cup, in which both male and female zebra ﬁnches participate . Our measures of nesting in female ﬁnches, however, were restricted to nest visitation and the time they spend in the nest may not reﬂect the degree to which they carry out any construction behavior within the nest cup. Collection of construction behavior data within the nest by both birds is required to speciﬁcally address (a) whether the anterior motor pathway might be involved in female nesting behavior and (b) whether it is involved in motor sequencing in males. 4.2. Social behavior network There was signiﬁcantly more Fos immunoreactivity in POM and BSTmd of nesting ﬁnches compared to control birds. In conjunction with previous reports of increased Fos production in POM and BSTmd during nest box possession in adult male starlings , our failure to ﬁnd correlations between Fos immunoreactivity in POM and BSTmd and nest building suggest that this activity is associated with nest possession. Although we did not ﬁnd a group difference in Fos immunoreactivity in BSTmv, Fos production increased the longer the females spent in the nest. Elevation of Fos production in BSTmv following nest box possession has been attributed to concurrent changes in agonistic behavior associated with territorial defense of the nest . Our results in female ﬁnches, however, suggest that such changes may be associated with occupation of the nest, a behavior that is only possible after a nest site has been obtained. Similar to Heimovics and Riters , we found that immediate early gene expression was higher in both BSTmd and BSTmv the more nesting behaviors the birds performed but those expression patterns differed. The differences in expression patterns dependent on the subdivisions of BSTm that are sampled may explain why there appeared to be no relationship in nesting birds between Fos production across the whole of BSTm and activation of vasotinergic neurons in BSTm . 4.3. Dopaminergic reward system Fos immunoreactivity in VTA increased the more pieces of material the male ﬁnches picked up. As with the increase in Fos expression we observed in the BSTmd, the data suggest that Fos expression in VTA might be associated with nest building itself rather than with of other behavioral changes that occur after a nest site is obtained that are unrelated to nest building . In addition to a potential role in reward during nest building, VTA may also inﬂuence activity in the anterior motor pathway during nest building. In vertebrates, VTA contains dopaminergic projection neurons. Studies in mammals have demonstrated that these neurons innervate the striatum and provide necessary dopamine to support basal ganglia functions including motor learning and sequencing [30,31]. This possibility of a role of the VTA on inﬂuencing activity of the anterior motor pathway is supported by our observation that Fos immunoreactivity was higher in both VTA and ASt the more nest material the males collected. Further
examination of the relationship between Fos immunoreactivity in dopaminergic neuron populations in VTA and nest building is required to test this prediction. 4.4. Hippocampus The absence of a correlation between variation in Fos expression in dHP and mHP and nesting behavior in male or female ﬁnches suggests that the hippocampus does not play a substantial role in nest building, at least in zebra ﬁnches. 4.5. Singing and HVC Finally, we conﬁrmed that Fos immunoreactivity is higher in the HVC as males spent more time singing. Furthermore, the time a male spent singing explained the variation in Fos expression better than did the number of song bouts [28,32]. 5. Conclusion Nest building in zebra ﬁnches involves the motor sequence of material collection and deposition by the male while the female visits the nest to receive material and shape the nest. Here we identiﬁed neural regions that varied in activity, as indicated by expression of the immediate early gene c-fos protein product Fos (the anterior motor pathway, social behavior network, and dopaminergic reward system), concomitantly with variation in nest building in male zebra ﬁnches and nesting in their mates. These are the ﬁrst detailed data to show the neural underpinnings of construction behavior in birds (see also Ref. ) and are, therefore, a major step in determining the role that motor planning and sequencing, context recognition, and reward and motivation may play in those behaviors. Acknowledgements This work was supported by the BBSRC (BB/I019502/1 to SDH & SLM) and NSERC (grant number PGSD3-409582-2011 to ZJH) and Roslin Institute Strategic Grant funding from the BBSRC (SLM). We would also like to thank Dr. Scott MacDougall-Shackleton and an anonymous reviewer for helpful comments on an earlier version of the manuscript. References  Thorpe WH. Learning and Instinct in Animals. London, UK: Methuen; 1956.  Hansell M. Bird Nests and Construction Behaviour. Cambridge, UK: Cambridge University Press; 2000.  Walsh PT, Hansell M, Borello WD, Healy SD. Repeatability of nest morphology in African weaver birds. Biol Lett 2010;6:149–51.  Walsh PT, Hansell M, Borello W, Healy SD. Individuality in nest building: do Southern Masked weaver (Ploceus velatus) males vary in their nest-building behavior? Behav Process 2011;88:1–6.  Walsh PT, Hansell M, Borello W, Healy SD. Are elaborate bird nests built using simple rules? Avian Biol Res 2013;6:157–62.  Muth F, Healy SD. The role of adult experience in nest building in the zebra ﬁnch, Taeniopygia guttata. Anim Behav 2011;82:185–9.  Muth F, Healy SD. Zebra ﬁnches build nests that do not resemble their natal nest. Avian Biol Res 2012;5:218–26.  Muth F, Healy SD. Colour preferences in nest-building zebra ﬁnches. Behav Process 2013;99:106–11.  Zann RA. The Zebra Finch: A Synthesis of Field and Laboratory Studies. Oxford, UK: Oxford University Press; 1996.  Meddle SL, Follett BK. Photoperiodically driven changes in Fos expression within the basal tuberal hypothalamus and median eminence of Japanese quail. J Neurosci 1997;17:8909–18.  Clayton DF. The genomic action potential. Neurobiol Learn Mem 2000;74:185–216.  Feenders G, Liedvogel M, Rivas M, Zapka M, Horita H, Hara E, Wada K, Mouritsen H, Jarvis ED. Molecular mapping of movement-associated areas in the avian brain: a motor theory for vocal learning origin. PLoS One 2008;3:e1768.
Z.J. Hall et al. / Behavioural Brain Research 264 (2014) 26–33  Kuenzel W, Medina L, Csillag A, Perkel D, Reiner A. The avian subpallium: new insights into structural and functional subdivisions occupying the lateral subpallial wall and their embryological origins. Brain Res 2011;1424: 67–101.  Obayashi S, Suhara T, Kawabe K, Okauchi T, Maeda J, Akine Y, Onoe H, Iriki A. Functional brain mapping of monkey tool use. NeuroImage 2001;14:853–61.  Goodson JL. The vertebrate social behavior network: evolutionary themes and variations. Horm Behav 2005;48:11–22.  Klatt JD, Goodson JL. Sex-speciﬁc activity and function of hypothalamic nonapeptide neurons during nest-building in zebra ﬁnches. Horm Behav 2013;64, http://dx.doi.org/10.1016/j.yhbeh.2013.10.001, pii: S0018-506X(13)00188-8.  Heimovics SA, Riters LV. Breeding-context-dependent relationships between song and cFOS labeling within social behavior brain regions in male European starlings (Sturnus vulgaris). Horm Behav 2006;50:726–35.  Sager TN, Kirchhoff J, Mørk A, Van Beek J, Thirstrup K, Didriksen M, Lauridsen JB. Nest building performance following MPTP toxicity in mice. Behav Brain Res 2010;208:444–9.  Heimovics SA, Riters LV. Immediate early gene activity in song control nuclei and brain areas regulating motivation relates positively to singing behavior during, but not outside of, a breeding context. J Neurobiol 2005;65:207–24.  Heimovics SA, Riters LV. ZENK labeling within social behavior brain regions reveals breeding context-dependent patterns of neural activity associated with song in male European starlings (Sturnus vulgaris). Behav Brain Res 2007;176:333–43.  Sherry DF, Hoshooley JS. The seasonal hippocampus of food-storing birds. Behav Process 2009;80:334–8.  Székely AD, Krebs JR. Efferent connectivity of the hippocampal formation of the zebra ﬁnch (Taenopygia guttata): an anterograde pathway tracing study using Phaseolus vulgaris leucoagglutinin. J Comp Neurol 1996;368: 198–214.
 Nordeen EJ, Holtzman DA, Nordeen KW. Increased Fos expression among midbrain dopaminergic cell groups during birdsong tutoring. Eur J Neurosci 2009;30:662–70.  Stokes TM, Leonard CM, Nottebohm F. The telencephalon, diencephalon, and mesencephalon of the canary, Serinus canaria, in stereotaxic coordinates. J Comp Neurol 1974;156:337–74.  Nixdorf-Bergweiler B, Bischof H. A Stereotaxic Atlas of the Brain of the Zebra Finch, Taeniopygia guttata, with special emphasis on Telencephalic Visual and Song System Nuclei in Transverse. Bethesda, MD: National Library of Medicine (US); 2007. p. NCBI:c2007.  George I, Hara E, Hessler NA. Behavioral and neural lateralization of vision in courtship singing of the zebra ﬁnch. J Neurobiol 2006:1164–73.  Morgan JI, Curran T. Stimulus-transcription coupling in the nervous system: involvement of the inducible proto-oncogenes fos and jun. Annu Rev Neurosci 1991;14:421–51.  Kimpo RR, Doupe AJ. FOS is induced by singing in distinct neuronal populations in a motor network. Neuron 1997;18:315–25.  Helduser S, Cheng S, Güntürkün O. Identiﬁcation of two forebrain structures that mediate execution of memorized sequences in the pigeon. J Neurophysiol 2013;109:958–68.  Joel D, Weiner I. The connections of the dopaminergic system with the striatum in rats and primates: an analysis with respect to the functional and compartmental organization of the striatum. Neuroscience 2000;96:451–74.  Hikosaka O, Bromberg-Martin E, Hong S, Matsumoto M. New insights on the subcortical representation of reward. Curr Opin Neurobiol 2008;18: 203–8.  Jarvis ED, Scharff C, Grossman MR, Ramos JA, Nottebohm F. For whom the bird sings: context-dependent gene expression. Neuron 1998;21:775–88.  Hall ZJ, Street SE, Healy SD. The evolution of cerebellum structure correlates with nest complexity. Biol Lett 2013;9:20130687.