The number of neurons in specific amygdala regions is associated with boldness in mink: a study in animal personality

Abstract

Conspecifics vary consistently in their behavioural responses towards environment stimuli such as exposure to novel objects; ethologists often refer to this variability as animal personality. The neurological mechanisms underlying animal personality traits remain largely unknown, but linking the individual variation in emotional expression to brain structural and neurochemical factors is attracting renewed interest. While considerable research has focused on hormonal and neurotransmitter effects on behavioural responses, less is known about how individual variation in the number of specific neuron populations contributes to individual variation in behaviour. The basolateral amygdala (BLA) and the central nuclei of the amygdala (CeA) mediate emotional processing by regulating behavioural responses of animals in a potentially threatening situation. As such, these structures are good candidates for evaluating the relationship between neuronal populations and behavioural traits. We now show that individual American mink (Neovison vison) reacting more boldly towards novelty have more neurons in the BLA than do their more timid conspecifics, suggesting that a developmental pattern of the number of amygdala neurons can influence behavioural traits of an adult animal. Furthermore, post hoc correlations revealed that individuals performing with higher arousal, as reflected by their frequency of startle behaviour, have more CeA neurons. Our results support a direct link between the number of neurons in amygdala regions and aspects of animal personality.

Paternal exposure to a common herbicide alters the behavior and serotonergic system of zebrafish offspring

“…Exposure to endocrine and neuroendocrine disrupting chemicals (EDCs) are reported to induce a variety of aberrant behaviors (see reviews: [1,2]), particularly when individuals are exposed early in life [3][4][5][6][7][8]. EDCs interfere with the molecular mechanisms that underpin behavior, such as gene expression, hormone levels, neurotransmitter levels, and the molecular machinery that mediates between these inputs [9][10][11][12][13][14][15] predominantly implicated in the disruption of typical reproductive behaviors (i.e. courtship and parental behavior; [2,3,16]), but non-reproductive behaviors, such as anxiety, aggression and risk-taking behavior also appear to be strongly affected [4,[17][18][19][20][21][22][22][23][24][25]).…”

A comparison of cell density and serotonergic innervation of the amygdala among four macaque species

“…In dogs, neuron density of the basolateral amygdala is positively associated with aggressive behavior (Jacobs, Van Den Broeck, & Simoens, 2006). In American minks ( Neovison vison ), individuals that more boldly explored novel environments possessed significantly greater neuron densities in the basolateral amygdala relative to their more reserved conspecifics (Wiese et al, 2018). Additionally, neuron density is significantly lower in the lateral nucleus of individuals diagnosed with autism spectrum disorder (ASD) compared to healthy controls (Schumann & Amaral, 2006; Wegiel et al, 2014).…”

Environmentally Realistic Waterborne Atrazine Exposure Affects Behavior in Poecilia latipinna

“…Some of the more commonly identified EDCs found in nature include organochlorines, organophosphates, polychlorinated biphenyls (PCBs), phthalates, phytoestrogens, among other synthetic hormone mimics or blockers released into soil and water from industrial effluents, pesticide use, plastics, and sewage [1,2]. Given their potential to affect molecular and physiological processes [3][4][5][6][7][8][9], EDC exposure may induce a variety of maladaptive behavioral changes that compromise the health and integrity of natural populations even at very low, non-lethal, environmentally realistic concentrations [10][11][12][13]. Identification and monitoring of these changes may serve as an excellent indicator of toxin-induced environmental effects on wildlife that may often be observed long before physiological changes can be identified, e.g., [14][15][16][17].…”