Neuroanatomical investigation of aggression in pit bulls

Aggression is a complex social behaviour observed in many animal species, including dogs, and remains a major global concern due to its serious implications for public safety and animal welfare. This study focuses on Pit Bull dogs, a breed frequently associated with severe aggression episodes in many countries, making them an appropriate model for investigating the neuroanatomical factors underlying canine aggression. To better understand its underlying mechanisms, this study investigated neuroanatomical and biochemical factors associated with aggression in Pit bulls. 14 dogs were selected for MRI analysis based on their aggression scores obtained through a aggression assesment survey derived from Canine Behavioral Assessment and Research Questionnaire. The dogs underwent MRI scans and blood and urine sampling and were divided into control and aggressive groups. MRI analyses focused on the prefrontal cortex, amygdala, and hippocampus. Biochemical analyses included serum or plasma levels of serotonin, dopamine, vasopressin, adrenaline, noradrenaline, testosterone, cortisol, and adrenocorticotropic hormone, along with urinary concentrations of their metabolites; metanephrine, vanillylmandelic acid, homovanillic acid, and 5-hydroxyindoleacetic acid. Results showed significantly decreased prefrontal cortex volumes and increased amygdala volumes in aggressive dogs compared to controls. Testosterone and dopamine levels were also significantly higher in the aggressive group. These findings suggest that structural alterations in key brain regions, combined with hormonal and neurotransmitter imbalances, may contribute to a maladaptive neurocognitive profile. Reduced top-down control by the prefrontal cortex may fail to inhibit exaggerated threat perception and emotional reactivity mediated by the amygdala, leading to aggressive behaviour in Pit bulls.