No abstract

Repeated encounters with the same event typically lead to decreased activation in the medial temporal lobe (MTL) and dopaminergic midbrain, a phenomenon known as repetition suppression. In contrast, encountering an event that overlaps with prior experience leads to increased response in the same regions. Such increased responding is thought to reflect an associative novelty signal that promotes memory updating to resolve differences between current events and stored memories. Here, we married these ideas to test whether event overlap significantly modulates MTL and midbrain responses—even when events are repeated and expected—to promote memory updating through integration. While undergoing high-resolution functional MRI, participants were repeatedly presented with objects pairs, some of which overlapped with other, intervening pairs and some of which contained elements unique from other pairs. MTL and midbrain regions showed widespread repetition suppression for non-overlapping pairs containing unique elements; however, the degree of repetition suppression was altered for overlapping pairs. Entorhinal cortex, perirhinal cortex (PRc), midbrain, and PRc—midbrain connectivity showed repetition-related increases across overlapping pairs. Notably, increased PRc activation for overlapping pairs tracked individual differences in the ability to reason about the relationships among pairs—our behavioral measure of memory integration. Within hippocampus, activation increases across overlapping pairs were unique to CA1, consistent with its hypothesized comparator function. These findings demonstrate that event overlap engages MTL and midbrain functions traditionally implicated in novelty processing, even when overlapping events themselves are repeated. Our findings further suggest that the MTL—midbrain response to event overlap may promote integration of new content into existing memories, leading to the formation of relational memory networks that span experiences. Moreover, the results inform theories about the division of labor within MTL, demonstrating that the role of PRc in episodic encoding extends beyond familiarity processing and item-level recognition.

Objective: To study the impact of brachial plexus MR neurography (MRN) in the diagnostic thinking and therapeutic management of patients with suspected plexopathy. Methods: MRN examinations of adult brachial plexuses over a period of 18 months were reviewed. Relevant data collection included-patient demographics, clinical history, pre-imaging diagnostic impression, pre-imaging treatment plan, post-imaging diagnosis, post-imaging treatment plan, surgical notes and electrodiagnostic (ED) results. Impact of imaging on the pre-imaging clinical diagnosis and therapeutic management were classified as no change, mild change or substantial change.

No abstract