The Study of Human-Animal Interactions The CAIRC Scholarship Program Summary of the Past Researches
Summary of the Past Scholarship Research
From "Letter from CAIRC" July 2004
Research Theme:" Neural Correlates of Perception and Affect Underlying Human-Animal Relationships: Research Using Functional Magnetic Resonance Imaging "
Takashi Hanakawa
Instructor, Human Brain Research Center, Kyoto University Graduate School of Medicine
Why is it that people pour such affection on their pets? What is the mechanism of feeling affection? The answers to these questions remain to be answered. Hanakawa, who researches brain function at the Kyoto University Graduate School of Medicine, set his sights on the structure of the neural mechanism within the brain that carries out the face recognition function, which is one factor in generating feelings of affection.

“Advances in research using functional magnetic resonance imaging, or fMRI, have helped reveal that brain activity associated with various complex emotions is physically located in the brain,” noted Hanakawa. “Extensive research, for instance, has discovered brain activity associated with human face recognition located in a part of the fusiform gyrus on the lower surface of the posterior cephalic fold. The first point of this research project was to find out whether the system within a dog owner’s brain that accomplishes face recognition of the pet has aspects in common with the human face recognition system. I also wanted to find out whether we would be able to distinguish among the brain activities associated with recognition of the faces of closely familiar people, passing acquaintances, and complete strangers. The goal was to clarify these two points using fMRI.”

The procedure consisted of placing 11 subjects in a high-resolution cranial MRI apparatus and showing them eight successive types of photographs. They were asked to indicate whether the image was familiar or unfamiliar to them as the changes in oxygen metabolism and cerebral blood flow associated with local brain activity were measured. The eight types of photo images were: 1) faces of examinees’ family members, 2) faces the examinees ware asked to remember just before the exam, 3) faces of strangers, 4) faces of examinees’ dogs, 5) faces of dogs the examinees were asked to remember just before the exam, 6) faces of unfamiliar dogs, 7) images hidden by a mosaic pattern the examinees were asked to remember just before the exam, and 8) unfamiliar images hidden by a mosaic pattern. Hanakawa prefaced his explanation of the results with the caveat that they could only be considered preliminary, since not enough examinees were tested for the findings to be conclusive.

“Activity associated with recognition of both human and canine faces was observed in part of the fusiform gyrus (Brodmann area 37), with no clear differences in location for human and canine faces,” he noted. “We therefore believe that a common neural base is used in both functions. We also picked up common reactions in the anterior orbital surface of the prefrontal cortex and amygdaloid complex to photos of both familiar human and familiar dog faces. In the future, I would like to continue research into the potential relationships between activity in these areas and the emotions of love and affection.”

Hanakawa believes that further comprehensive research is necessary. He notes that in order to further pinpoint the brain structures that give rise to the emotions of love and affection, it will be necessary to increase the amount of experimental data available, while also conducting parallel studies into autonomic nerve reflexes and subjective emotions.