Biased feedback in spatial recall yields a violation of delta rule learning

Abstract

This study investigates whether inductive processes influencing spatial memory performance generalize to supervised learning scenarios with differential feedback. After providing a location memory response in a spatial recall task, participants received visual feedback showing the target location. In critical blocks, feedback was systematically biased either 4 degrees toward the vertical axis (toward condition) or 4 degrees farther away from the vertical axis (away condition). Results showed that the weaker teaching signal (i.e., a smaller difference between the remembered location and the feedback location) produced a stronger experience-dependent change over blocks in the away condition than in the toward condition. This violates delta rule learning. Subsequent simulations of the dynamic field theory of spatial cognition provide a theoretically unified account of these results.

Figure 1

(A) Target distribution (left panel) and apparatus (right panel) used for the spaceship task. The black disc at the origin of the target distribution corresponds to the yellow reference disc used in the experiment. Targets were projected onto the table from beneath. Lights were dimmed during the experiment and the table appeared black. (B) Time line of the experimental procedure. (C) Sample target location (30°) along with feedback biased either 4° towards the vertical axis (Towards condition) or 4° away from the vertical axis (Away condition). (D) Mean error calculation method demonstrated here using the response distribution for the ±30° target in the Away condition in Block 2 (all subjects) as an example.

Figure 2

(A) Location memory performance. Positive errors indicate drift away from the vertical axis. Negative errors indicate drift towards the vertical axis. Block 1 performance is averaged across the Towards and Away conditions. The gray region reflects the change in memory performance from Block 1 to the average of Blocks 2 and 3 for those in the Away condition. The textured region reflects memory performance change from Block 1 to the average in Blocks 2 and 3 for those in the Towards condition. (B) Memory performance difference scores (collapsed across targets) for the Towards and Away conditions. Positive difference scores indicate an increase in drift away from the vertical axis over blocks. Negative difference scores indicate a decrease in drift away from the vertical. Error bars represent standard errors.

Figure 3

Simulation of the Dynamic Field Theory. Panel (A) represents the perceptual field, panel (B) the shared inhibitory field, panel (C) the spatial working memory (SWM) field, and panel (D) the long-term memory field. Green arrows indicate excitatory connections between fields. Red arrows indicate inhibitory connections. In each layer, spatial location (°) is represented along the X axis, time along the Y axis, and activation along the Z axis. The trial begins at the front of the figure and moves towards the back. See text for additional details.

Figure 4

Memory performance difference scores (collapsed across targets) for the Towards and Away conditions from simulations of the DFT. Positive difference scores indicate an increase in drift away from the vertical axis over blocks. Negative difference scores indicate a decrease in drift away from the vertical. Error bars represent standard errors.

Figure 5

Comparison of long-term memory activation at the end of Block 1 (dashed line) and end of Block 3 (solid line) for the (A) Away and (B) Towards feedback conditions. Asterisks indicate target locations presented during simulation trials.