Prefrontal-temporal circuitry for episodic encoding and subsequent memory

Humans encounter and form memories for multiple types of experiences that d iffer in content, novelty, and memorability. Critical for understanding mem ory is determining (1) how the brain supports the encoding of events with d iffering content and (2) whether neural regions that are sensitive to novel ty also influence whether stimuli will be subsequently remembered. This eve nt-related functional magnetic resonance imaging (fMRI) study crossed conte nt (picture/word), novelty (novel/repeated), and subsequent memory (remembe red/forgotten) to examine prefrontal and temporal lobe contributions to enc oding. Results revealed three patterns of encoding-related activation in an atomically connected inferior prefrontal and lateral temporal structures th at appeared to vary depending on whether visuospatial/visuoobject, phonolog ical/lexical, or semantic attributes were processed. Event content also mod ulated medial temporal lobe activity; word encoding predominately activated the left hemisphere, whereas picture encoding activated both hemispheres. Critically, in prefrontal and temporal regions that were modulated by novel ty, the magnitude of encoding activation also predicted whether an event wo uld be subsequently remembered. These results suggest that (1) regions that demonstrate a sensitivity to novelty may actively support encoding process es that impact subsequent explicit memory and (2) multiple content-dependen t prefrontal-temporal circuits support event encoding. The similarities bet ween prefrontal and lateral temporal encoding responses raise the possibili ty that prefrontal modulation of posterior cortical representations is cent ral to encoding.