A theory of working memory without consciousness or sustained activity
Darinka Trübutschek, Sébastien Marti, Andrés Ojeda, Jean-Rémi King, Yuanyuan Mi, Misha Tsodyks, Stanislas Dehaene
bioRxiv Preprint Server December 14, 2016 preprint DOI: 10.1101/093815 via bioRxiv
Summary
Working memory and conscious perception are often thought to rely on the same brain mechanisms, but recent evidence suggests non-conscious working memory exists. Using visual masking and magnetoencephalography in a spatial delayed-response task, participants reported the location of a subjectively unseen target above chance after a long delay. Conscious perception and conscious working memory showed sustained alpha/beta desynchronization over frontal cortex and decodable target location in posterior sensors. During non-conscious working memory, these signals vanished, contradicting models equating working memory with sustained neural firing. The findings support 'activity-silent' working memory, where slowly decaying synaptic changes allow cell assemblies to go dormant during the delay yet be retrieved above chance after seconds.
Study at a glance
| Characteristics | Experimental study |
|---|---|
| Keywords | Subconscious recall Non-conscious memory Unaware retention Subconscious memory Unconscious |
| Citations | 47 |
| Key finding | Non-conscious working memory is possible and relies on activity-silent mechanisms rather than sustained neural firing. |
Abstract
Working memory and conscious perception are thought to share similar brain mechanisms, yet recent reports of non-conscious working memory challenge this view. Combining visual masking with magnetoencephalography, we demonstrate the reality of non-conscious working memory and dissect its neural mechanisms. In a spatial delayed-response task, participants reported the location of a subjectively unseen target above chance-level after a long delay. Conscious perception and conscious working memory were characterized by similar signatures: a sustained desynchronization in the alpha/beta band over frontal cortex, and a decodable representation of target location in posterior sensors. During non-conscious working memory, such activity vanished. Our findings contradict models that identify working memory with sustained neural firing, but are compatible with recent proposals of ‘activity-silent’ working memory. We present a theoretical framework and simulations showing how slowly decaying synaptic changes allow cell assemblies to go dormant during the delay, yet be retrieved above chance-level after several seconds.