Read the following sentence: “Donald Trump and Kamala Harris entered the bar, she sat at a table.” We all know immediately that it was Kamala who came to the table, not Donald. Pronouns like “she” help us understand language, but pronouns can have multiple meanings. Depending on the context, we understand who the pronoun refers to. But how are we so good at this, and how does our brain link pronouns to their nouns?
To answer this question, an international team of neuroscientists, neurosurgeons and neurologists joined forces. Doris Dijksterhuis and Matthew Self, from Pieter Roelfsema’s group, together with their colleagues, analyzed the brain activity of patients with epilepsy. As part of their treatment, these patients had electrodes implanted deep in the hippocampus, an area of the brain involved in learning and memory. The research team took advantage of this and conducted additional tests on them.
“We can measure the activity of individual brain cells in the hippocampus while the patient performs a task,” says Matthew Self. In the hippocampus there are cells that respond to a specific person, the so-called “conceptual cells.” A well-known example is the “Jennifer Aniston cell,” which is activated when you see a photo of Jennifer Aniston, hear her name, or read the words “Jennifer Aniston.” We wonder if these cells are also activated when only one pronoun is read, such as “he” or “she.” Are these cells capable of linking the pronoun to the right person?
shrek cell
Doris Dijksterhuis: “To test this, we first showed patients many photos until we found a cell that responded to a particular image. For example, we found a cell that responded to a ‘Shrek’ image but not to other images. call to this cell a ‘Shrek conceptual cell’ when patients then read a sentence such as: “Shrek and Fiona were having dinner.” The ‘Shrek’ cell did indeed respond to the word “Shrek”, but also to the pronoun ‘He’. This is interesting because that pronoun can mean something completely different in another sentence. For example, in the sentence “Donald Trump and Kamala Harris were having dinner,” the same pronoun, “He,” refers to Donald. Trump and therefore the Shrek cell will not react. “Individual cells in the hippocampus track who the pronoun refers to in a dynamic and flexible way.”
Me: “We had participants answer a question at the end of sentences about who performed the action. We could predict whether patients would give the correct answer based on the activity of individual conceptual cells. To make it a little more challenging, we also added some leading questions, with two people of the same gender: “Jennifer Aniston and Kamala Harris walked into a bar. She sat at the table.” The patient had to decide for himself who performed the action. We observed that patients tended to choose the person who evoked the most activity in the hippocampus at the beginning of the sentence. This could be based on fluctuations “randomizations in trial-by-trial activity or an internal preference for one of the two characters in the sentence.”
The bigger picture
Dijksterhuis: “The hippocampus is important for learning and memory, but it is still unclear how the hippocampus is involved in the interaction between memory and language. How do we remember what we have read? When you think about something you have read, we have different concepts that together create the story. Pronouns help us understand who did what in the story and the hippocampal cells encode these actions in our memory. Ultimately, we want to know how a complete memory is formed and represented in the brain. “
“It is of great value that this group of patients has given their permission to participate in our research. Only very rarely can we measure the activity of individual brain cells in people who read and it is impossible to study these processes in animals. If we have the opportunity “We try to make the most of it.”
Fountain: Science