title: Turning Symbolic: The Representation of Motion Direction in Working Memory.
abstract: What happens to the representation of a moving stimulus when it is no longer present and its motion direction has to be maintained in working memory (WM)? Is the initial, sensorial representation maintained during the delay period or is there another representation, at a higher level of abstraction? It is also feasible that multiple representations may co-exist in WM, manifesting different facets of sensory and more abstract features. To that end, we investigated the mnemonic representation of motion direction in a series of three psychophysical experiments, using a delayed motion-discrimination task (relative clockwise∖counter-clockwise judgment). First, we show that a change in the dots' contrast polarity does not hamper performance. Next, we demonstrate that performance is unaffected by relocation of the Test stimulus in either retinotopic or spatiotopic coordinate frames. Finally, we show that an arrow-shaped cue presented during the delay interval between the Sample and Test stimulus, strongly biases performance toward the direction of the arrow, although the cue itself is non-informative (it has no predictive value of the correct answer). These results indicate that the representation of motion direction in WM could be independent of the physical features of the stimulus (polarity or position) and has non-sensorial abstract qualities. It is plausible that an abstract mnemonic trace might be activated alongside a more basic, analog representation of the stimulus. We speculate that the specific sensitivity of the mnemonic representation to the arrow-shaped symbol may stem from the long term learned association between direction and the hour in the clock.
authors.affiliation: Department of Neurobiology, Alexander Silberman Institute of Life Sciences, Hebrew University of JerusalemJerusalem, Israel; Department of Psychology, Hebrew University of JerusalemJerusalem, Israel; Institut National de la Santé et de la Recherche Médicale U1127, Centre National de la Recherche Scientifique UMR 7225, UMR S 1127, Évaluation Physiologique chez les Sujets Sains et Atteints de Troubles Cognitifs (PICNIC Lab), Institut du Cerveau et de la Moelle Épinière, Sorbonne Universités, Université Pierre et Marie Curie-Paris 06Paris, France.
authors.forename: Tal
authors.initials: T
authors.lastname: Seidel Malkinson
authors.affiliation: Department of Psychology, Hebrew University of Jerusalem Jerusalem, Israel.
authors.forename: Yoni
authors.initials: Y
authors.lastname: Pertzov
authors.affiliation: Department of Neurobiology, Alexander Silberman Institute of Life Sciences, Hebrew University of JerusalemJerusalem, Israel; The Edmond and Lily Safra Center for Brain Sciences, Hebrew University of JerusalemJerusalem, Israel.
authors.forename: Ehud
authors.initials: E
authors.lastname: Zohary
keywords: motion; representation; visual working memory; working memory