Hippocampal sclerosis affects fMR-adaptation of lyrics and melodies in songs

Songs constitute a natural combination of lyrics and melodies, but it is unclear whether and how these two song components are integrated during the emergence of a memory trace. Network theories of memory suggest a prominent role of the hippocampus, together with unimodal sensory areas, in the build-up of conjunctive representations. The present study tested the modulatory influence of the hippocampus on neural adaptation to songs in lateral temporal areas. Patients with unilateral hippocampal sclerosis and healthy matched controls were presented with blocks of short songs in which lyrics and/or melodies were varied or repeated in a crossed factorial design. Neural adaptation effects were taken as correlates of incidental emergent memory traces. We hypothesized that hippocampal lesions, particularly in the left hemisphere, would weaken adaptation effects, especially the integration of lyrics and melodies. Results revealed that lateral temporal lobe regions showed weaker adaptation to repeated lyrics as well as a reduced interaction of the adaptation effects for lyrics and melodies in patients with left hippocampal sclerosis. This suggests a deficient build-up of a sensory memory trace for lyrics and a reduced integration of lyrics with melodies, compared to healthy controls. Patients with right hippocampal sclerosis showed a similar profile of results although the effects did not reach significance in this population. We highlight the finding that the integrated representation of lyrics and melodies typically shown in healthy participants is likely tied to the integrity of the left medial temporal lobe. This novel finding provides the first neuroimaging evidence for the role of the hippocampus during repetitive exposure to lyrics and melodies and their integration into a song

Putting the Distributed Practice Effect into Context

Spaced repetition leads to superior final memory relative to massed repetition, a phenomenon known as the distributed practice effect. However, when items are repeated in variable study contexts across learning opportunities (relative to a consistent study context), the advantage of distributed practice over massed practice is typically reduced. In this dissertation, the effect of study context on the distributed practice effect was investigated from a neural perspective (Study 1) and from a developmental perspective (Study 2). In Study 1, event-related potentials (ERPs) were recorded as participants learned stimuli repeated after massed or distributed lags on either a consistent or variable background. After a fixed retention interval, stimuli were presented for a third time and participants recognition memory was tested. Behavioural evidence of a Lag x Study Context interaction was mixed. The ERP data revealed a neural distinction between massed and distributed repetitions during the study phase in terms of the late positivity component (LPC); however, the LPC was not further defined by the study context manipulation. During the test phase, distributed, variably studied repetitions engendered the greatest neural familiarity response compared to all other repetition conditions. In Study 2, younger and older participants learned stimuli repeated after varying lags on either a consistent or variable background. The background scenes were either shared among all to-be-learned items (Experiment 2A) or unique to each to-be-learned item (Experiment 2B). After the study phase, participants free recall memory was tested. Although older adults had greater difficulty identifying whether a repeated items study context had changed throughout the study phase, as hypothesized, they still exhibited similar final recall performance to younger adults during the test phase. Comparing data from the two experiments, the results also revealed that variations to study context might actually enhance the distributed practice effect in certain learning situations. This enhancement effect, which warrants further investigation, might depend on the type of material being learned and/or the variety of contextual information available during study