During social interactions, the brain activity of humans and dogs aligns, especially when there is eye contact or touching, creating a connection between them. This synchronization increases over five days as they become more familiar, suggesting that humans lead interactions and dogs follow. In dogs with a genetic mutation in the Shank3 gene linked to autism spectrum disorder (ASD), this synchronization is impaired, which affects their social skills. However, after a single dose of LSD, the connection was found to be restored, offering new clues to potential treatments and markers for social symptoms.
Communication between humans and dogs has evolved over 30,000 years, starting when dogs were domesticated to help with hunting and protection. Over time, they became part of families, providing emotional support and companionship. Unlike other domesticated animals, such as cats, dogs have developed a unique ability to understand and respond to human emotions and signals, whether through facial expressions, gestures or even tone of voice.
This communication between humans and dogs is quite unique and goes beyond the common relationships between species, which are usually based solely on mutual benefits, such as safety.
While it is clear that dogs have an extraordinary ability to communicate with humans, there is still much to be discovered about the brain mechanisms behind this. Recently, research published in the journal Advanced Science by the Institute of Genetics and Developmental Biology seeks to understand how this synchronization between the brains of humans and dogs occurs during interaction, and which areas of the brain are involved.
Previous studies on neural synchronization have focused primarily on interactions within the same species, such as in humans, mice, and primates.
However, this new research seeks to explore whether this neural coupling also occurs across species, such as between humans and dogs.
In this study, the researchers used a wireless electroencephalogram (EEG), a headgear with electrodes that measures brain activity, in both beagles and humans. This noninvasive EEG was used while the dogs and unfamiliar people engaged in social interactions, divided into three different situations: when they were in separate rooms without interaction, when they were in the same room without interaction, and when there was social interaction, such as mutual gaze and petting.
These interactions, which include eye contact and touching, are essential forms of nonverbal communication for both humans and dogs. The goal was to understand how these forms of interaction affect the brain activity of both and whether there is any synchronization between brain activity during this direct contact.
Interbrain activity coupling during human-dog interactions. A) Schematic of human-dog interactions (mutual gaze and petting): no interaction in separate rooms (left), with (right panel), and without (middle panel) interactions in the same room. B) Schematic of scalp electrode positions in the dog brain (top) and in the human brain (bottom). C) Normalized mean EEG powers recorded simultaneously in frontal regions of dogs and humans on the fifth day of social interactions in three different conditions (no social interaction in separate rooms (top) and in the same room (middle) and with social interactions in the same room (bottom)). D) Heatmap of interbrain activity correlations between dogs and humans interacting socially over five days. E) Interbrain correlation in the frontal and parietal regions of the brain of a dog (red) and a human (blue). F) Interbrain correlation in the frontal (left) and parietal (right) regions of a dog and a human interacting socially over five days. https://doi.org/10.1002/advs.202402493
Researchers have demonstrated for the first time that directed interbrain neural coupling occurs between humans and dogs, particularly in the frontal and parietal regions, both associated with joint attention and socialization. The strength of this synchronization increased with increasing familiarity of the human-dog pairs over 5 days, and tests indicated that the human is the leader while the dog is the follower during human-dog interactions.
The next step would be to test this interaction in people with Autism Spectrum Disorder (ASD). Mutations in the SHANK3 gene are some of the most common genetic causes associated with ASD, a condition that affects about 1% of the world's population. People with autism have persistent difficulties in communication and social interaction, which are related precisely to the frontal and parietal regions of the brain.
In children with severe symptoms of autism, there is less shared brain activity during social interactions with their parents, which could explain part of the difficulties in socialization. Testing this synchronization in autistic people can help to better understand the causes and possible treatments for ASD.
Mutations in the Shank3 gene also occur in dogs, making them an effective model for studying social cognition problems and neuropsychiatric disorders, such as Autism Spectrum Disorder (ASD) in humans. This helps to overcome the limitations of rodent models, whose differences in brain and behavior limit comparison with humans, and also of monkey models, which are expensive and have slow reproduction.
Dogs with mutations in the Shank3 gene showed a loss of brain synchronization with humans, especially in the frontal and parietal areas, which are associated with attention. The researchers tested these dogs for attention problems using a method that measures the theta/beta brain wave ratio (TBR).
A high TBR indicates a poor attention span, while a low TBR indicates a more focused state. Dogs with the Shank3 mutation had a higher TBR, suggesting impaired attention. This finding is similar to that found in children with ASD and ADHD, who also show higher resting TBR compared to typically developing children.
Currently, few effective treatments directly address social difficulties, which are the main symptoms of ASD. However, psychedelics, known for their hallucinogenic effects, are being revisited in modern scientific research, following pioneering studies in the 20th century.
One example is LSD (lysergic acid diethylamide), which in recent studies has shown a potential to increase sociability, empathy, and levels of oxytocin, a neuropeptide linked to social behavior.
To investigate whether LSD has an effect on synchronizing brain activity between humans and dogs, researchers administered specific doses of LSD to dogs with mutations in the Shank3 gene.
After treatment, these dogs showed a significant increase in the correlation of brain activity between themselves and humans, especially in the frontal and parietal lobe areas, which are regions of the brain associated with social interaction and which generally show reduced activity in individuals with ASD.
Furthermore, this increase in brain synchronization was progressive over the five days of observation after treatment, suggesting that LSD may have a lasting effect on improving neural communication in social interactions.
These results indicate that LSD may positively influence the social deficits observed in disorders such as ASD, at least in an animal model such as Shank3 mutant dogs.
READ MORE:
Disrupted Human–Dog Interbrain Neural Coupling in Autism-Associated Shank3 Mutant Dogs
Wei Ren, Shan Yu, Kun Guo, Chunming Lu, Yong Q. Zhang
Advanced Science. 2024. doi.org/10.1002/advs.202402493
Abstract:
Dogs interact with humans effectively and intimately. However, the neural underpinnings for such interspecies social communication are not understood. It is known that interbrain activity coupling, i.e., the synchronization of neural activity between individuals, represents the neural basis of social interactions. Here, previously unknown cross-species interbrain activity coupling in interacting human–dog dyads is reported. By analyzing electroencephalography signals from both dogs and humans, it is found that mutual gaze and petting induce interbrain synchronization in the frontal and parietal regions of the human–dog dyads, respectively. The strength of the synchronization increases with growing familiarity of the human–dog dyad over five days, and the information flow analysis suggests that the human is the leader while the dog is the follower during human–dog interactions. Furthermore, dogs with Shank3 mutations, which represent a promising complementary animal model of autism spectrum disorders (ASD), show a loss of interbrain coupling and reduced attention during human–dog interactions. Such abnormalities are rescued by the psychedelic lysergic acid diethylamide (LSD). The results reveal previously unknown interbrain synchronizations within an interacting human–dog dyad which may underlie the interspecies communication, and suggest a potential of LSD for the amelioration of social impairment in patients with ASD.
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