PT  - JOURNAL ARTICLE
AU  - Knops, André
AU  - Piazza, Manuela
AU  - Sengupta, Rakesh
AU  - Eger, Evelyn
AU  - Melcher, David
TI  - A Shared, Flexible Neural Map Architecture Reflects Capacity Limits in Both Visual Short-Term Memory and Enumeration
AID  - 10.1523/JNEUROSCI.2758-13.2014
DP  - 2014 Jul 23
TA  - The Journal of Neuroscience
PG  - 9857--9866
VI  - 34
IP  - 30
4099  - http://www.jneurosci.org/content/34/30/9857.short
4100  - http://www.jneurosci.org/content/34/30/9857.full
SO  - J. Neurosci.2014 Jul 23; 34
AB  - Human cognition is characterized by severe capacity limits: we can accurately track, enumerate, or hold in mind only a small number of items at a time. It remains debated whether capacity limitations across tasks are determined by a common system. Here we measure brain activation of adult subjects performing either a visual short-term memory (vSTM) task consisting of holding in mind precise information about the orientation and position of a variable number of items, or an enumeration task consisting of assessing the number of items in those sets. We show that task-specific capacity limits (three to four items in enumeration and two to three in vSTM) are neurally reflected in the activity of the posterior parietal cortex (PPC): an identical set of voxels in this region, commonly activated during the two tasks, changed its overall response profile reflecting task-specific capacity limitations. These results, replicated in a second experiment, were further supported by multivariate pattern analysis in which we could decode the number of items presented over a larger range during enumeration than during vSTM. Finally, we simulated our results with a computational model of PPC using a saliency map architecture in which the level of mutual inhibition between nodes gives rise to capacity limitations and reflects the task-dependent precision with which objects need to be encoded (high precision for vSTM, lower precision for enumeration). Together, our work supports the existence of a common, flexible system underlying capacity limits across tasks in PPC that may take the form of a saliency map.