Controlling brain dynamics: Landscape and transition path for working memory
Fig 2
Landscapes explain the working memory function with multistable attractors.
(A-B) The schematic illustration of the visual working memory task. During the fixation phase, no external stimulus is applied. During the target phase, a cue is given, which is modeled as the population A of V1 receiving external current. Then the stimulus is removed and the target is expected to be maintained in working memory against random fluctuations and distractors encoded by population B at the delay epoch. Once the task has been done, the sustained activity should be shut down by delivering excitatory input to the inhibitory populations in four areas (9/46d, 9/46v, F7, 8B), leading to the clearance of working memory. (C) The stochastic neural activity traces of selected areas for correct and error trials (See Fig C in S1 Text for behaviors of all areas). For correct trial, the target stimulus is maintained at delay epoch against distractor. On the contrary, the distractor induces the transition from the stimulus-selective high activity state to the distractor-selective high state for error trial. (D) The corresponding attractor landscapes during different phases of the working memory task. The green ball represents the system state. Before the stimulus onset, the system stays at the resting state (R) with all the populations at low activity. The stimulus changes the landscape topography from tristability to bistability. And the system state transits from R to the dominated target-related memory state (MA). Even after the withdrawal of stimulus and the landscape topography returns back to tristability, the system state keeps staying at MA. However, the presentation of distractor stimulus changes the landscape again and may or may not induce the transition to distractor-related attractor (MB), corresponding error and correct trials, respectively. (E-F) The dependence of the proportion between correct and error trials on the intensity of distractor input and the diffusion coefficient. (G) The barrier height between saddle point and MA (USA) versus the diffusion coefficient. (H) The proportion between correct and error trials versus USA.