of the brain implied that the "hate circuit" involves the putamen and the insula. It has been theorized that the "putamen plays a role in the perception of contempt and disgust, and may be part of the motor system that's mobilized to take action." It was also found that the amount of activity in the hate circuit correlates with the amount of hate a person declares, which could have legal implications concerning malicious crimes. Role in transgender individuals The putamen was found to have significantly larger amounts of grey matter in male to female transgender individuals compared to the putamen of a typical cisgender man. This possibly suggests that a fundamental difference in brain composition may exist between trans women and cisgender men. Pathology Parkinson's disease After discovering the function of the putamen, it has become apparent to neurologists that the putamen and other parts of the basal ganglia play an important role in Parkinson's disease and other diseases that involve the degeneration of neurons. Parkinson's disease is the slow and steady loss of dopaminergic neurons in substantia nigra pars compacta. In Parkinson's disease the putamen plays a key role because its inputs and outputs are interconnected to the substantia nigra and the globus pallidus. In Parkinson's disease the activity in direct pathways to interior globus pallidus decreases and activity in indirect pathways to external globus pallidus increases. It has also been noted that Parkinson's patients have a difficult time with motor planning. Other diseases and disorders The following diseases and disorders are linked with the putamen: Cognitive decline in Alzheimer's disease Huntington's disease Wilson's disease Dementia with Lewy bodies Corticobasal degeneration Tourette syndrome Schizophrenia Depression Attention deficit hyperactivity disorder Chorea Obsessive-Compulsive Disorder Kernicterus Other anxiety disorders In other animals The putamen in humans is relatively similar in structure and function to other animals. Therefore, many studies on the putamen have been done on animals (monkeys, rats, cats, etc.), as well as humans. However, inter-species variation are indeed observed in mammals, and have been documented for white matter putaminal connectivity. Variation is primarily related to structural connectivity patterns, while somatotopic organization principles are retained. Primate research since the 1980s through to the present has established that cortical regions relation to higher-order cognition primarily send afferent neurons to the rostal-most portion of the putamen, while the remainder of this structure in primates primarily serves sensori-motor functions and is densely interconnected with