title: Causal evidence for a privileged working memory state in early visual cortex.
abstract: Emerging evidence suggests that items held in working memory (WM) might not all be in the same representational state. One item might be privileged over others, making it more accessible and thereby recalled with greater precision. Here, using transcranial magnetic stimulation (TMS), we provide causal evidence in human participants that items in WM are differentially susceptible to disruptive TMS, depending on their state, determined either by task relevance or serial position. Across two experiments, we applied TMS to area MT+ during the WM retention of two motion directions. In Experiment 1, we used an "incidental cue" to bring one of the two targets into a privileged state. In Experiment 2, we presented the targets sequentially so that the last item was in a privileged state by virtue of recency. In both experiments, recall precision of motion direction was differentially affected by TMS, depending on the state of the memory target at the time of disruption. Privileged items were recalled with less precision, whereas nonprivileged items were recalled with higher precision. Thus, only the privileged item was susceptible to disruptive TMS over MT+. By contrast, precision of the nonprivileged item improved either directly because of facilitation by TMS or indirectly through reduced interference from the privileged item. Our results provide a unique line of evidence, as revealed by TMS over a posterior sensory brain region, for at least two different states of item representation in WM.
authors.affiliation: Department of Experimental Psychology, University of Oxford, Oxford, OX1 3UD, United Kingdom, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, OX3 9DU, United Kingdom, Institute of Cognitive Neuroscience, University College London, London, WC1N 3AR, United Kingdom, and School of Psychology and Clinical Language Sciences, University of Reading, RG6 7BE, United Kingdom.
authors.forename: Nahid
authors.initials: N
authors.lastname: Zokaei
authors.forename: Sanjay
authors.initials: S
authors.lastname: Manohar
authors.forename: Masud
authors.initials: M
authors.lastname: Husain
authors.forename: Eva
authors.initials: E
authors.lastname: Feredoes
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D008297:Male; D008570:Memory, Short-Term / Q000502:physiology*; D010775:Photic Stimulation / Q000379:methods*; D011597:Psychomotor Performance / Q000502:physiology*; D050781:Transcranial Magnetic Stimulation / Q000379:methods*; D014793:Visual Cortex / Q000502:physiology*; D055815:Young Adult