Contribution
Cortical and Brainstem Responses to High- and Low-Level features of Musical Melodies and their Relation to Reverse Hierarchy Theory
* Presenting author
Abstract:
Reverse Hierarchy Theory (RHT) posits that sensory input is hierarchically organized, with low-level features (e.g., timbre) processed in subcortical structures and high-level features (e.g., melodic contours) in the cortex. RHT suggests that only high-level features are immediately conscious, while conscious access to low-level features requires top-down processing, potentially involving increased activity in the inferior colliculus (IC).To test these hypotheses, participants took part in three different measurements. In the first condition, subjects watched a silent movie with no task while listening to melodies (passive listening). The second ask (active listening) required the subject to indicate whether the melodies differ from each other or not (high-level task). The third task (active listening) involved minor timbre differences in those melodies (low-level task) which had to be recognised by the listener. We hypothesized that focusing on low-level features would enhance the amplitude of frequency following responses (FFRs) from the IC. While robust FFRs were recorded, no significant amplitude differences were found across conditions. We also employed magnetoencephalography (MEG) and source analysis to assess auditory cortex representations and information flow from core to belt and parabelt regions, in line with RHT.