#olifaction

‘Psychopaths’ Have An Impaired Sense of Smell

Psychopathy is a broad term that covers a severe personality disorder characterized by callousness, manipulation, sensation-seeking and antisocial behaviors, traits which may also be found in otherwise healthy and functional people. Studies have shown that people with psychopathic traits have impaired functioning in the front part of the brain – the area largely responsible for functions such as planning, impulse control and acting in accordance with social norms. In addition, a dysfunction in these areas in the front part of the brain is linked to an impaired sense of smell.

Mahmut and Stevenson looked at whether a poor sense of smell was linked to higher levels of psychopathic tendencies, among 79 non-criminal adults living in the community. First they assessed the participants’ olfactory ability as well as the sensitivity of their olfactory system. They also measured subjects’ levels of psychopathy, looking at four measures: manipulation; callousness; erratic lifestyles; and criminal tendencies. They also noted how much or how little they emphasized with other people’s feelings.

Anxious people have a heightened sense of smell when it comes to sniffing out a threat, according to a new study by Elizabeth Krusemark and Wen Li from the University of Wisconsin-Madison in the US. Their work¹ is published online in Springer's journal Chemosensory Perception. The study is part of a special issue² of this journal on neuroimaging the chemical senses.

In animals, the sense of smell is an essential tool to detect, locate and identify predators in the surrounding environment. In fact, the olfactory-mediated defense system is so prominent in animals, that the mere presence of predator odors can evoke potent fear and anxiety responses.

Smells also evoke powerful emotional responses in humans. Krusemark and Li hypothesized that in humans, detection of a particular bad smell may signal danger of a noxious airborne substance, or a decaying object that carries disease.

The researchers exposed 14 young adult participants to three types of odors: neutral pure odor, neutral odor mixture, and negative odor mixture. They asked them to detect the presence or absence of an odor in an MRI scanner. During scanning, the researchers also measured the skin's ability to conduct electricity (a measure of arousal level) and monitored the subjects' breathing patterns. Once the odor detection task was over, and the subjects were still in the scanner, they were asked to rate their current level of anxiety. The authors then analyzed the brain images obtained.

They found that as anxiety levels rose, so did the subjects' ability to discriminate negative odors accurately - suggesting a 'remarkable' olfactory acuity to threat in anxious subjects. The skin conductance results showed that anxiety also heightened emotional arousal to smell-induced threats.

The authors uncovered amplified communication between the sensory and emotional areas of the brain in response to negative odors, particularly in anxiety. This increased connectivity could be responsible for the heightened arousal to threats.