Scientists from the Weizmann Institute discovered that the brain has a cognitive map that represents not only one's own location but also social locations
On the soccer field, at a toasting event at the office or during a family trip to the park, it is important for us to know where the people who are important to us are. Is a teammate currently in a favorable scoring position? Does the boss approach to shake hands or does the child approach the road? The ability to place the other in space is an essential feature of social animals which enables, among other things, actions such as courtship, hunting, learning by observing the other, and group navigation. In recent decades, brain researchers have discovered different groups of nerve cells that create a sort of cognitive map of our self-position in space. However, the way in which we place the other in space remains a mystery. In a new study published today in the scientific journal Science For the first time, researchers from the Weizmann Institute present a subset of nerve cells in the brains of bats that represents the location in space of other bats. At the same time, I publish today Science A study by a group from the Japanese RIKEN Research Institute also indicates similar findings in rats. The studies show that these nerve cells apparently underlie the spatial-social perception of mammals, including humans.
Bats are flying and extremely sociable mammals that live in colonies with a complex social structure. "Similar to humans, the ability of bats to place others in space is essential for them," says Prof. Nahum Ulanovsky whose laboratory in the Department of Neurobiology specializes in the study of the spatial perception of common fruit bats. Over the years, the laboratory has focused on the connection between navigation and spatial memory and the electrical activity in the area of the brain called the hippocampus, and has studied, among other things, the activity of the place cells in the hippocampus, which are a significant part of the mechanism that has been nicknamed the "GPS of the brain" andcredit his discoveries with the Nobel Prize for Medicine in 2014. However, in recent years, surprising evidence has multiplied that, in addition to spatial functions, the hippocampus is also involved in social functions. These discoveries for the first time outlined a social direction for Prof. Ulanovsky's laboratory.
"The most difficult part of the experiment was to prevent the bats from flying together to the food. For this, you could say that we were required to hold 'auditions' for the roles of 'teacher' and 'student'. The 'trick' we eventually found was to choose 'teachers' who are alpha males - when Alpha flies towards the food, the 'student' respects him and does not compete with him"
To test whether and how "social locations" are represented in the hippocampus of bats, the researchers carefully designed a spatial learning task: the bats were divided into four pairs of "student" and "teacher" and placed in a controlled flight chamber built for them at the Weizmann Institute of Science. In each trial, one "student" first watched the "teacher" randomly fly to one of two food stations and back to the starting point. After a delay of about 13 seconds on average, the "pupil" traced the flight path of the "teacher" and received an appropriate and sweet reward for successfully completing the task. Throughout all the stages of the experiment, the brain activity of the "students" was recorded using the smallest wireless equipment of its kind in the world, specially developed in the laboratory of Prof. Ulanovsky. The wireless electrodes made it possible to measure the activity of about 400 nerve cells in a subregion of the anterior hippocampus without disturbing the bats' natural and free movement. Says Prof. Ulanovski: "The most difficult part of the experiment was to prevent the bats from flying together to the food. Otherwise we would not have been able to separate the brain activity that represents the self-position and that which represents the position of the other. For this purpose, we could say that we were required to conduct 'auditions' for the roles The 'teacher' and the 'student.' Gives him respect and does not compete with him." Dr. David Omer, Dr. Liora Less and research student Shir Maimon from Prof. Ulanovsky's group also participated in the study.
>> A teacher, a student and two food stands: an illustration of the spatial learning task
The findings confirm the existence of a cognitive map that represents not only self-location but also social locations. Naturally, as the student bats moved through space, the location cells represented their locations. However, the researchers discovered for the first time that when the students remained in their place and observed the movement of the teachers, the activity of about 18% of the neurons in the hippocampus was recorded. To make sure that the electrical activity does indeed represent the absolute position of the other bat - and not, for example, the head movements of the observing bat - the researchers used a motion sensor that helped make sure that the head did not move or almost did not move. The scientists also discovered that about 50% of these neurons had mixed selectivity - that is, they functioned alternately as location cells and social location cells, while the others were selective for social location only.
And maybe every bone would activate the nerve cells in the same way? Prof. Ulanovsky explains: "In two follow-up experiments, we recorded the brain activity in response to football- and cube-like objects that moved in space in a similar manner to the 'teachers'. In the first experiment, the 'students' were asked to trace the movement of the football, while in the second experiment the bats were not rewarded, so Trace the movement of the cube. In the experiments we found that the objects were also represented in the hippocampus That is, while the representation of the two objects was similar, the representation of the living bat differed from both. In addition, we examined the functional anatomy within the hippocampus, and discovered that the form in which the responses to the bat and the objects are distributed is different."
>> The bats during the experiment in the darkened room. The teacher (marked in blue) shows the way to the student (in red)
These findings open the door to many follow-up questions - how will the social location cells react in multi-participant situations? How will the reaction in the brain of the bats change depending on the species and the degree of familiarity with the other animal? Moreover, these findings indicate new directions for the study of the hippocampus. Says Prof. Ulanovski: "Only in recent years is the fact that the hippocampus is apparently involved not only in physical navigation but also in more complicated cognitive functions - such as the ability to navigate within a social space or move towards abstract social goals."
One response