Synaptic augmentation in a cortical circuit model reproduces serial dependence in visual working memory

• Published in: PloS one Vol. 12; no. 12; p. e0188927
• Main Authors: Bliss, Daniel P., D’Esposito, Mark
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 15.12.2017; Public Library of Science (PLoS)
• Subjects: Analysis; Augmentation; Behavior; Behavioral plasticity; Bias; Biology and Life Sciences; Cerebral Cortex - cytology; Cerebral Cortex - physiology; Computer and Information Sciences; Computer Simulation; Cortex; Cortex (temporal); Human behavior; Humans; Memory; Memory, Short-Term - physiology; Mixtures; Models, Neurological; Neural circuitry; Neural networks; Neuronal Plasticity - physiology; Neurons; Neurosciences; Occlusion; Physiological aspects; Pyramidal Cells - cytology; Pyramidal Cells - physiology; Receptors, AMPA - physiology; Receptors, GABA-A - physiology; Receptors, N-Methyl-D-Aspartate - physiology; Short term; Short term memory; Studies; Synapses; Synapses - physiology; Synaptic plasticity; Synaptic transmission; Synaptic Transmission - physiology; Temporal lobe; Trends; Visual cortex; Visual Pathways - physiology; Visual task performance; United States
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0188927

Recent work has established that visual working memory is subject to serial dependence: current information in memory blends with that from the recent past as a function of their similarity. This tuned temporal smoothing likely promotes the stability of memory in the face of noise and occlusion. Serial dependence accumulates over several seconds in memory and deteriorates with increased separation between trials. While this phenomenon has been extensively characterized in behavior, its neural mechanism is unknown. In the present study, we investigate the circuit-level origins of serial dependence in a biophysical model of cortex. We explore two distinct kinds of mechanisms: stable persistent activity during the memory delay period and dynamic "activity-silent" synaptic plasticity. We find that networks endowed with both strong reverberation to support persistent activity and dynamic synapses can closely reproduce behavioral serial dependence. Specifically, elevated activity drives synaptic augmentation, which biases activity on the subsequent trial, giving rise to a spatiotemporally tuned shift in the population response. Our hybrid neural model is a theoretical advance beyond abstract mathematical characterizations, offers testable hypotheses for physiological research, and demonstrates the power of biological insights to provide a quantitative explanation of human behavior.