{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,11]],"date-time":"2026-05-11T01:11:33Z","timestamp":1778461893535,"version":"3.51.4"},"reference-count":42,"publisher":"MDPI AG","issue":"7","license":[{"start":{"date-parts":[[2023,6,23]],"date-time":"2023-06-23T00:00:00Z","timestamp":1687478400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100004359","name":"Swedish Research Council","doi-asserted-by":"publisher","award":["2019-04869"],"award-info":[{"award-number":["2019-04869"]}],"id":[{"id":"10.13039\/501100004359","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["www.mdpi.com"],"crossmark-restriction":true},"short-container-title":["Brain Sciences"],"abstract":"<jats:p>A central part of the domestication syndrome is a reduction in relative brain size. In chickens, it has previously been shown that domesticated birds have smaller relative brain mass, but larger relative mass of cerebellum, compared to their ancestors, the Red Junglefowl. It has been suggested that tameness may drive the domestication syndrome, so we examined the relationship between brain characteristics and tameness in 31 Red Junglefowl from lines divergently selected during ten generations for tameness. Our focus was on the whole brain, cerebellum, and the remainder of the brain. We used the isotropic fractionator technique to estimate the total number of cells in the cerebellum and differentiate between neurons and non-neuronal cells. We stained the cell nuclei with DAPI and performed cell counting using a fluorescence microscope. NeuN immunostaining was used to identify neurons. The absolute and relative masses of the brains and their regions were determined through weighing. Our analysis revealed that birds selected for low fear of humans (LF) had smaller relative brain mass compared to those selected for high fear of humans (HF). Sex had a significant impact only on the absolute size of the cerebellum, not its relative size. These findings support the notion that selection for increased tameness leads to an enlargement of the relative size of cerebellum in chickens consistent with comparisons of domesticated and ancestral chickens. Surprisingly, the HF birds had a higher density of neurons in the cerebellum compared to the LF line, despite having a smaller cerebellum overall. These findings highlight the intricate relationship between brain structure and behavior in the context of domestication.<\/jats:p>","DOI":"10.3390\/brainsci13070988","type":"journal-article","created":{"date-parts":[[2023,6,26]],"date-time":"2023-06-26T05:39:13Z","timestamp":1687757953000},"page":"988","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":8,"title":["Selection for Reduced Fear of Humans Changes Brain and Cerebellum Size in Red Junglefowl in Line with Effects of Chicken Domestication"],"prefix":"10.3390","volume":"13","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-3680-0769","authenticated-orcid":false,"given":"Johanna","family":"Gj\u00f8en","sequence":"first","affiliation":[{"name":"AVIAN Behavioural Physiology and Genomics Group, IFM Biology, Link\u00f6ping University, 58183 Link\u00f6ping, Sweden"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Felipe","family":"Cunha","sequence":"additional","affiliation":[{"name":"AVIAN Behavioural Physiology and Genomics Group, IFM Biology, Link\u00f6ping University, 58183 Link\u00f6ping, Sweden"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Per","family":"Jensen","sequence":"additional","affiliation":[{"name":"AVIAN Behavioural Physiology and Genomics Group, IFM Biology, Link\u00f6ping University, 58183 Link\u00f6ping, Sweden"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2023,6,23]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Jensen, P., and Wright, D. (2022). Behavioral genetics and animal domestication. Genetics and the Behavior of Domestic Animals, Elsevier.","DOI":"10.1016\/B978-0-323-85752-9.00002-0"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1086\/413673","article-title":"Behavioral Aspects of Animal Domestication","volume":"59","author":"Price","year":"1984","journal-title":"Q. Rev. Biol."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"301","DOI":"10.1093\/oxfordjournals.jhered.a109263","article-title":"Destabilizing selection as a factor in domestication","volume":"70","author":"Belyaev","year":"1979","journal-title":"J. Hered."},{"key":"ref_4","doi-asserted-by":"crossref","unstructured":"Price, E.O. (2002). Animal Domestication and Behavior, Cabi.","DOI":"10.1079\/9780851995977.0000"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"1059","DOI":"10.1016\/j.tree.2020.08.009","article-title":"Defining the Domestication Syndrome: Comment on Lord et al. 2020","volume":"35","author":"Wright","year":"2020","journal-title":"Trends Ecol. Evol."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"795","DOI":"10.1534\/genetics.114.165423","article-title":"The \u201cDomestication Syndrome\u201d in Mammals: A Unified Explanation Based on Neural Crest Cell Behavior and Genetics","volume":"197","author":"Wilkins","year":"2014","journal-title":"Genetics"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"115","DOI":"10.1159\/000111458","article-title":"Mosaic Evolution and Adaptive Brain Component Alteration under Domestication Seen on the Background of Evolutionary Theory","volume":"71","author":"Frahm","year":"2008","journal-title":"Brain Behav. Evol."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"105704","DOI":"10.1016\/j.isci.2022.105704","article-title":"baz1b loss-of-function in zebrafish produces phenotypic alterations consistent with the domestication syndrome","volume":"26","author":"Anagianni","year":"2023","journal-title":"iScience"},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"197","DOI":"10.1016\/j.crvi.2010.12.012","article-title":"Chicken domestication: From archeology to genomics","volume":"334","author":"Rognon","year":"2011","journal-title":"Comptes Rendus Biol."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"e2121978119","DOI":"10.1073\/pnas.2121978119","article-title":"The biocultural origins and dispersal of domestic chickens","volume":"119","author":"Peters","year":"2022","journal-title":"Proc. Natl. Acad. Sci. USA"},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"34031","DOI":"10.1038\/srep34031","article-title":"The domesticated brain: Genetics of brain mass and brain structure in an avian species","volume":"6","author":"Henriksen","year":"2016","journal-title":"Sci. Rep."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"250","DOI":"10.1016\/j.beproc.2010.12.010","article-title":"Domestication effects on behavioural synchronization and individual distances in chickens (Gallus gallus)","volume":"86","author":"Eklund","year":"2011","journal-title":"Behav. Process."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"753","DOI":"10.1046\/j.1439-0310.2001.00703.x","article-title":"Effects of resource allocation on behavioural strategies: A comparison of red junglefowl (Gallus gallus) and two domesticated breeds of poultry","volume":"107","author":"Jensen","year":"2001","journal-title":"Ethology"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"645","DOI":"10.1016\/j.conb.2006.08.016","article-title":"Learning to predict the future: The cerebellum adapts feedforward movement control","volume":"16","author":"Bastian","year":"2006","journal-title":"Curr. Opin. Neurobiol."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"552","DOI":"10.1007\/s12311-016-0815-8","article-title":"Consensus Paper: Cerebellum and Emotion","volume":"16","author":"Adamaszek","year":"2017","journal-title":"Cerebellum"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"151","DOI":"10.1007\/s12311-013-0511-x","article-title":"Consensus Paper: The Cerebellum\u2019s Role in Movement and Cognition","volume":"13","author":"Koziol","year":"2014","journal-title":"Cerebellum"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"1157","DOI":"10.1126\/science.1093535","article-title":"Empathy for Pain Involves the Affective but not Sensory Components of Pain","volume":"303","author":"Singer","year":"2004","journal-title":"Science"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"833","DOI":"10.1007\/s12311-020-01155-1","article-title":"Consensus Paper: Cerebellum and Social Cognition","volume":"19","author":"Manto","year":"2020","journal-title":"Cerebellum"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"1175","DOI":"10.1016\/0031-9384(90)90369-F","article-title":"Role of the cerebellum in an avoidance conditioning task in the rat","volume":"47","author":"Dahhaoui","year":"1990","journal-title":"Physiol. Behav."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"20200790","DOI":"10.1098\/rsbl.2020.0790","article-title":"Cerebellum size is related to fear memory and domestication of chickens","volume":"17","author":"Katajamaa","year":"2021","journal-title":"Biol. Lett."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"325","DOI":"10.1016\/0165-0173(90)90006-A","article-title":"The cerebellum and learning processes in animals","volume":"15","author":"Lalonde","year":"1990","journal-title":"Brain Res. Rev."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"168","DOI":"10.1080\/14734220701332486","article-title":"The cerebellum: Comparative and animal studies","volume":"6","author":"Sultan","year":"2008","journal-title":"Cerebellum"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"244","DOI":"10.1111\/dgd.12362","article-title":"Avian brains: Insights from development, behaviors and evolution","volume":"59","author":"Nomura","year":"2017","journal-title":"Dev. Growth Differ."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"307","DOI":"10.1016\/S1364-6613(98)01210-8","article-title":"The anatomy of the cerebellum","volume":"2","author":"Voogd","year":"1998","journal-title":"Trends Cogn. Sci."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"227","DOI":"10.1016\/j.applanim.2017.09.006","article-title":"Is evolution of domestication driven by tameness? A selective review with focus on chickens","volume":"205","author":"Agnvall","year":"2018","journal-title":"Appl. Anim. Behav. Sci."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"349","DOI":"10.1002\/bies.200800070","article-title":"Animal evolution during domestication: The domesticated fox as a model","volume":"31","author":"Trut","year":"2009","journal-title":"Bioessays"},{"key":"ref_27","doi-asserted-by":"crossref","unstructured":"Gj\u00f8en, J., and Jensen, P. (2021). Selection for Reduced Fear of Humans Changes Intra-Specific Social Behavior in Red Jungle-fowl\u2014Implications for Chicken Domestication. Genes, 13.","DOI":"10.3390\/genes13010043"},{"key":"ref_28","doi-asserted-by":"crossref","unstructured":"Agnvall, B., J\u00f6ngren, M., Strandberg, E., and Jensen, P. (2012). Heritability and Genetic Correlations of Fear-Related Behaviour in Red Junglefowl\u2013Possible Implications for Early Domestication. PLoS ONE, 7.","DOI":"10.1371\/journal.pone.0035162"},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"2518","DOI":"10.1523\/JNEUROSCI.4526-04.2005","article-title":"Isotropic Fractionator: A Simple, Rapid Method for the Quantification of Total Cell and Neuron Numbers in the Brain","volume":"25","author":"Lent","year":"2005","journal-title":"J. Neurosci."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"201","DOI":"10.1242\/dev.116.1.201","article-title":"NeuN, a neuronal specific nuclear protein in vertebrates","volume":"116","author":"Mullen","year":"1992","journal-title":"Development"},{"key":"ref_31","first-page":"124","article-title":"Proportional Cerebellum Size Predicts Fear Habituation in Chickens","volume":"13","author":"Cunha","year":"2022","journal-title":"Front. Physiol."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"1588","DOI":"10.1002\/cne.25298","article-title":"High associative neuron numbers could drive cognitive performance in corvid species","volume":"530","author":"Neves","year":"2022","journal-title":"J. Comp. Neurol."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"360","DOI":"10.2307\/1366199","article-title":"A Field Study of the Red Jungle Fowl in North-Central India","volume":"69","author":"Collias","year":"1967","journal-title":"Condor"},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"553","DOI":"10.1016\/j.tics.2023.03.008","article-title":"The evolutionary neuroscience of domestication","volume":"27","author":"Hecht","year":"2023","journal-title":"Trends Cogn. Sci."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"20150509","DOI":"10.1098\/rsbl.2015.0509","article-title":"Is domestication driven by reduced fear of humans? Boldness, metabolism and serotonin levels in divergently selected red junglefowl (Gallus gallus)","volume":"11","author":"Agnvall","year":"2015","journal-title":"Biol. Lett."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"211002","DOI":"10.1098\/rsos.211002","article-title":"The cerebellar anatomy of red junglefowl and white leghorn chickens: Insights into the effects of domesti-cation on the cerebellum","volume":"8","author":"Racicot","year":"2021","journal-title":"R. Soc. Open Sci."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"2429","DOI":"10.1097\/00001756-199707280-00004","article-title":"Fear decrease in transgenic mice over-expressing bcl-2 in neurons","volume":"8","author":"Dubreuil","year":"1997","journal-title":"Neuroreport"},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"25","DOI":"10.1086\/285785","article-title":"Refining the Motor Training Hypothesis for the Evolution of Play","volume":"146","author":"Byers","year":"1995","journal-title":"Am. Nat."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"216","DOI":"10.1101\/lm.119806","article-title":"Different mechanisms of fear extinction dependent on length of time since fear ac-quisition","volume":"13","author":"Myers","year":"2006","journal-title":"Learn Mem."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"1176668","DOI":"10.3389\/fnsys.2023.1176668","article-title":"Cerebellar control of fear learning via the cerebellar nuclei\u2013Multiple pathways, multiple mechanisms?","volume":"17","author":"Sala","year":"2023","journal-title":"Front. Syst. Neurosci."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"1508","DOI":"10.1038\/s41467-023-36943-w","article-title":"The cerebellum regulates fear extinction through thalamo-prefrontal cortex interactions in male mice","volume":"14","author":"Frontera","year":"2023","journal-title":"Nat. Commun."},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"219","DOI":"10.1016\/S0149-7634(01)00010-0","article-title":"Animal models of anxiety and depression: How are females different?","volume":"25","author":"Palanza","year":"2001","journal-title":"Neurosci. Biobehav. Rev."}],"updated-by":[{"DOI":"10.3390\/brainsci13101465","type":"correction","label":"Correction","source":"publisher","updated":{"date-parts":[[2023,6,23]],"date-time":"2023-06-23T00:00:00Z","timestamp":1687478400000}}],"container-title":["Brain Sciences"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2076-3425\/13\/7\/988\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,8,3]],"date-time":"2025-08-03T14:38:47Z","timestamp":1754231927000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2076-3425\/13\/7\/988"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2023,6,23]]},"references-count":42,"journal-issue":{"issue":"7","published-online":{"date-parts":[[2023,7]]}},"alternative-id":["brainsci13070988"],"URL":"https:\/\/doi.org\/10.3390\/brainsci13070988","relation":{"correction":[{"id-type":"doi","id":"10.3390\/brainsci13101465","asserted-by":"object"}]},"ISSN":["2076-3425"],"issn-type":[{"value":"2076-3425","type":"electronic"}],"subject":[],"published":{"date-parts":[[2023,6,23]]}}}