Understanding the contributions of visual stimuli to contextual fear conditioning: a proof-of-concept study using LCD screens

Abstract

The precise contribution of visual information to contextual fear-learning and discrimination has remained elusive. To better understand this contribution, we coupled the context pre-exposure facilitation effect (CPFE) fear conditioning paradigm with presentations of distinct visual scenes displayed on 4 LCD screens surrounding a conditioning chamber. Adult male Long-Evans rats received non-reinforced context pre-exposure on Day 1, an immediate 1.5 mA foot shock on Day 2, and a non-reinforced context test on Day 3. Rats were pre-exposed to either digital Context (dCtx) A, dCtx B, a distinct Context C, or no context on Day 1. Context A and B were identical except for the visual image displayed on the LCD monitors. Immediate shock and retention testing occurred in dCtx A. Rats pre-exposed dCtx A showed the CPFE with significantly higher levels of freezing compared to learning controls. Rats pre-exposed to Context B failed to show the CPFE, with freezing that did not differ significantly from any group. The results suggest that 1) visual information contributes to contextual fear learning in rats and that 2) visual components of the context can be parametrically controlled via LCD screens. Our approach offers a simple modification to contextual fear conditioning whereby the visual features of a context can be precisely controlled to better understand how rodents discriminate and generalize fear across environments.