Fig. 5. Biophysically Inspired Architecture Allows for Flexible Encoding of Time.

a Diagram of the model architecture. Core neural architectures (CNAs, visualized here as columns) located in the PFC are selective to certain sensory stimuli (indicated here by color atop the column) via fixed excitatory inputs (conditioned stimulus, CS). Ventral tegmental area dopamine (VTA, DA) neurons receive fixed input from naturally positive valence stimuli, such as food or water reward (unconditioned stimulus, US). DA neuron firing releases dopamine, which acts as a learning signal for both PFC and VTA. Solid lines indicate fixed connections, while dotted lines indicate learned connections. b, c Schematic representation of data adapted from Liu et al. ⁵¹. b Timers learn to characteristically decay at the time of cue-predicted reward. c Messengers learn to have a firing peak at the time of cue-predicted reward. Definitions: prefrontal cortex (PFC), ventral tegmental area (VTA).