Multi-item working memory capacity: What is the role of the stimulation protocol?

Abstract

The dynamics of the stimulation protocol become relevant when investigating multi-item working memory (WM). In this work, we explore what is the effect of the stimulation protocol in the encoding and maintenance of multiple items in WM. To this end, we consider a biophysically-realistic attractor model of visual working memory endowed with synaptic facilitation. We show that such a mechanism plays a key role when sequential stimulation protocols are considered. On one hand, synaptic facilitation boosts WM capacity. On the other hand, it allows us to account for the experimentally reported recency effect (i.e. in sequential stimulation protocols, those items presented in the final positions of a sequence are more likely to be retained in WM). In this context, the time constant of the synaptic facilitation process has been found to play an important role in modulating such effects with large values leading to larger capacity limits. However, too large values lead to neuronal dynamics which are not compatible with the recency effect, thus constraining the range of values that the time constant may take.