Model-based fMRI reveals co-existing specific and generalized concept representations

Abstract

There has been a long-standing debate about whether categories are represented by individual category members (exemplars) or by the central tendency abstracted from individual members (prototypes). Across neuroimaging studies, there has been neural evidence for either exemplar representations or prototype representations, but not both. In the present study, we asked whether it is possible for individuals to form multiple types of category representations within a single task. We designed a categorization task to promote both exemplar and prototype representations, and we tracked their formation across learning. We found evidence for coexisting prototype and exemplar representations in brain in regions that aligned with previous studies: prototypes in ventromedial prefrontal cortex and anterior hippocampus and exemplars in inferior frontal gyrus and lateral parietal cortex. These findings show that, under the right circumstances, individuals may form representations at multiple levels of specificity, potentially facilitating a broad range of future memory-based decisions.

Generalization and the hippocampus: More than one story?

“…Using more coherent categories, our recent model-based fMRI study showed better fit of the prototype compared to the exemplar model in both brain and behavior. Importantly, we found prototype-consistent signals in the anterior hippocampus, in addition to ventromedial prefrontal cortex (VMPFC) (Bowman & Zeithamova, 2018), and replicated these findings in a separate study (Bowman, Iwashita, & Zeithamova, 2020). The evidence of prototype representation in the hippocampus indicates that it may store abstract concept representation derived across exemplars.…”

Learning of Concepts: A Review of Relevant Advances Since 2010 and Its Inspirations for Teaching

“…Scientists even observed prototype tendencies on two young jackdaws [11]. The most intriguing is a 6 / 28 preprint from 2020, which found that prototype and exemplar processing coexisted during the training phase of the task, but unexpectedly disappeared during the task testing phase, resulting in only a prototype bias -even the researchers were surprised by this result [12]. They provided several guesses, one of which was likely a transformation from exemplar representation to prototype representation during the training process.…”

Learning of Concepts: A Review of Relevant Advances Since 2010 and Its Inspirations for Teaching

“…Scientists even observed prototype tendencies in two young jackdaws [11] . The most intriguing is a preprint from 2020, which found that prototype and exemplar processing coexisted during the training phase of the task, but unexpectedly disappeared during the task testing phase, resulting in only a prototype bias, and even the researchers were surprised by this result [12] . They provided several guesses, one of which was likely a transformation from exemplar representation to prototype representation during the training process.…”