Decoding Concurrent Representations of Pitch and Location in Auditory Working Memory.

Multivariate analyses of hemodynamic signals serve to identify the storage of specific stimulus contents in working memory (WM). Representations of visual stimuli have been demonstrated both in sensory regions and in higher cortical areas. While previous research has typically focused on the WM maintenance of a single content feature, it remains unclear whether two separate features of a single object can be decoded concurrently. Also, much less evidence exists for representations of auditory compared with visual stimulus features. To address these issues, human participants had to memorize both pitch and perceived location of one of two sample sounds. After a delay phase, they were asked to reproduce either pitch or location. At recall, both features showed comparable levels of discriminability. Region of interest (ROI)-based decoding of functional magnetic resonance imaging (fMRI) data during the delay phase revealed feature-selective activity for both pitch and location of a memorized sound in auditory cortex and superior parietal lobule. The latter region showed higher decoding accuracy for location than pitch. In addition, location could be decoded from angular and supramarginal gyrus and both superior and inferior frontal gyrus. The latter region also showed a trend for decoding of pitch. We found no region exclusively coding pitch memory information. In summary, the present study yielded evidence for concurrent representations of pitch and location of a single object both in sensory cortex and in hierarchically higher regions, pointing toward representation formats that enable feature integration within the same anatomic brain regions.

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