Beyond recording methods, studies of human theta activity also differ in their analysis schemes. During encoding, studies commonly compare patterns of spectral power between items that were subsequently remembered vs. not-remembered (the “subsequent memory effect,” or SME). During retrieval, studies compare activity surrounding the presentation of a cue or, in free recall, they compare correct recalls to time periods where no recall occurs. Such memory-success analyses may obscure neural dynamics that differentially support different kinds of successful memory encoding or retrieval. Therefore, the second-most common approach is to assess the correlation between neural activity and a specific measure of associative memory formation. For example, one study [13] contrasted activity relating to the accuracy of spatial recalls, while another study [14] contrasted activity relating to the recall of spatially-proximate vs. spatially-distant information. By only analyzing successful memory events but grouping activity by a measure of associative memory performance, these studies provide a more specific assay of memory-related neural activity.
