Hippocampal and Frontoparietal Mechanisms of Knowledge Acquisition and Inference

University of Texas at Austin

Summary

The goal of this clinical trial is to test if an intervention used to manipulate memory and inference can improve our understanding of how brain development supports these abilities in healthy adolescent and adult volunteers. The main questions it aims to answer are: (1) Do hippocampus and ventromedial prefrontal cortex shift from forming simple memories for singular experiences to more complex memories that link numerous experiences together?; (2) Does an improved ability to retrieve prior memories in parietal cortex during new learning have consequences for how those memories are organized at different ages?; and (3) Does the emerging memory control supported by ventromedial prefrontal cortex development facilitate the formation of optimally-organized memory representations? Adolescent participants (13-18 years) will perform two experimental tasks during functional magnetic resonance imaging (fMRI) scanning at three timepoints (T1-T3), spaced 1.5 years apart. Researchers will compare behavioral and neuroimaging data to a separate group of adults (19-25 years) who will perform the task at a single timepoint (T1). The tasks and comparison groups will allow us to isolate the neural processes that support memory and inference behavior, and how these processes change with age.

Description

Hippocampus (HPC) structure and its connectivity with frontoparietal regions continue to develop through adolescence, a developmental period associated with substantial gains in memory and reasoning. While such structural changes are well documented, we know less about the functions that HPC and frontoparietal development confer, fundamentally limiting our understanding of the mechanisms through which individuals learn and reason about the world at different ages. From very early in life, children can learn simple associations that they directly experience. However, with age, our memories beco…

Interventions

Behavioral

Associative Inference

Objects, faces, and scenes will be arranged into 12 ABC triads presented as overlapping AB and BC pairs. AB pairs will comprise objects; BC pairs will consist of the same B object paired with a face or scene (C). Twelve non-overlapping (NO) pairs will serve as controls. Participants will study overlapping (AB, BC) and NO pairs (4s) across two 5-minute fMRI runs. Each pair will be presented three times within a run. Following learning, participants will complete a self-paced 3-alternative forced choice (AFC) inference task during which they will select the C item that shares a common relationship with an A cue. Foils for inference trials will be C items from other ABC triads, of the same face/scene subcategory. Participants will then complete a final, self-paced 3-AFC memory test of premise associations (AB, BC) and NO pairs. To quantify memory retrieval and how overlapping events are organized, before and after learning, participants will view the A and C items during fMRI scanning.

Behavioral

Probabilistic Inference

Participants will visit a virtual "zoo," which is divided into three zones, each containing the same five monsters, but with different likelihoods of occurrence. Participants learn the underlying likelihood distributions by virtually navigating each zone. On each trial, two monsters appear; participants select the monster that they predict will next appear (6s). After making their choice, the correct monster appears and feedback is provided (2s). Participants tour each zone four times across 9 runs. Following learning, participants are tested on probabilistic inference. Here, participants see a series of monster "photographs" and are asked to infer in which zone they were taken. On each trial, a sequence of individual monster images (3.5s each) will then appear (1-6 monsters) prior to a decision screen, in which participants choose which of the two zones most likely produced the "photos" (4s) and are given feedback (1.5s). Participants will perform nine fMRI runs of the inference task.

Hippocampal and Frontoparietal Mechanisms of Knowledge Acquisition and Inference

Summary

Description

Eligibility

Interventions

Location