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Dr. Sangil Lee, Dr. Trishala Parthasarathi, and Baird Term Professor of Psychology Joseph Kable used MRI scans to look at different parts of the brain and measure brain activity while the subjects imagined events.

Credit: Keyu Lu

Baird Term Professor of Psychology Joseph Kable’s research on imagined events was published in the Journal of Neuroscience on June 16.

Sangil Lee and Trishala Parthasarathi — who received their Ph.Ds from Penn in 2020 and 2017, respectively — co-authored the research with Kable. The researchers used MRI scans to look at different parts of the brain and measure brain activity while the subjects imagined events.

“We had this hypothesis, coming from questions like ‘Why do we have imagination at all? Why do we have this ability to transport ourselves to other times and places?’” Kable said. 

Kable said that these questions led the group to think about how different parts of the brain were responsible for different aspects of imagining. Vividness, which is the amount of detail and concreteness of an imagined event, and valence, which is the intensity of positive or negative emotions invoked by the imagined event, became their points of focus, he added.

The research subjects were asked to imagine scenarios that Parthasarathi came up with beforehand while she studied their brain activity using MRI scans. The subjects then rated the vividness and valence of their imaginations of each scenario.

Using MRI scans, the researchers looked primarily at the default mode network, the region of the brain where activity takes place, Kable said.

“I think our study might be the first to do what’s known as a double dissociation, where we manipulate both vividness and valence of the imagination separately and show that they correlate to different areas of the default mode network simultaneously in one study,” Lee said.

The default mode network was found to be active under the MRI scan even when subjects were told not to do anything, Kable said. 

“What people are doing when you ask them to not do anything in particular and [to] close their eyes in the scanner is that they’re remembering the past, or thinking about the things they have to do after the experiment,” Kable explained. 

The researchers found that high vividness of a subject’s imagination activated an area on the hippocampus, whereas high valence activated an area near the prefrontal cortex, Kable said. 

Lee added that a finding from the research that surprised him was the timing at which regions of the brain were activated. Brain activity associated with vividness happened earlier in the imaginations than brain activity associated with valence, he explained.

“I think we have a really good understanding of how the brain processes sensory stimuli that are in the moment through systems like the visual system,” Kable said. “But people spend a lot of their lives not paying attention, and I think we have less of an understanding of how our brains do that. I’m hoping that this is a small step towards our future studies.”