Scene complexity: influence on perception, memory, and development in the medial temporal lobe

Abstract

Regions in the medial temporal lobe (MTL) and prefrontal cortex (PFC) are involved in memory formation for scenes in both children and adults. The development in children and adolescents of successful memory encoding for scenes has been associated with increased activation in PFC, but not MTL, regions. However, evidence suggests that a functional subregion of the MTL that supports scene perception, located in the parahippocampal gyrus (PHG), goes through a prolonged maturation process. Here we tested the hypothesis that maturation of scene perception supports the development of memory for complex scenes. Scenes were characterized by their levels of complexity defined by the number of unique object categories depicted in the scene. Recognition memory improved with age, in participants ages 8-24, for high-, but not low-, complexity scenes. High-complexity compared to low-complexity scenes activated a network of regions including the posterior PHG. The difference in activations for high- versus low-complexity scenes increased with age in the right posterior PHG. Finally, activations in right posterior PHG were associated with age-related increases in successful memory formation for high-, but not low-, complexity scenes. These results suggest that functional maturation of the right posterior PHG plays a critical role in the development of enduring long-term recollection for high-complexity scenes.

Keywords: cognitive development; declarative memory; fMRI; parahippocampal gyrus; perception; visual scenes.

Figure 1

Recollection memory for high-complexity, but not low-complexity, scenes improved significantly with age. Examples of original scenes (left) and items in those scenes identified for complexity calculation (right) for (A) high-complexity scene and (B) low-complexity scene. Adjusted recollection rates (R_HIT – R_FA) (filled circles) and adjusted familiarity rates (K_HIT – K_FA) (open circles) for (C) high-complexity scenes and (D) low-complexity scenes plotted against the participants’ age. Recollection for low-complexity scenes and familiarity for high- and low-complexity scenes did not change reliably with age.

Figure 2

Activations associated with successful memory formation for high- and low- complexity scenes in posterior parahippocampal gyrus. (A) Axial brain image depicting right posterior parahippocampal ROI defined by increase in activation with age for high > low complexity scenes. Image corresponds to MNI × coordinate 26. (B, C) Plots of correlations of the individual parameter estimates (PE) in the contrast R > F for high- (B) and low- (C) complexity scenes (black, filled circles). Overlaid in red (open circles) are the individual parameter estimates extracted from contrasts R > F for high- (B) and low- (C) complexity scenes after correcting for the scene's spatial frequency.

Figure 3

MTL activations associated with successful memory formation (R > F) for children, adolescents, and young adults, for high-complexity scenes (top), and low- complexity scenes (bottom), scenes. Activation maps are overlaid on standard T1 image (for display purposes, p < 0.005, uncorrected, T value scale presented on the right). Children, n = 16, 8 male, mean age 10.7, range 8–12 years of age; adolescents, n = 16, 8 male, mean age 15.9, range 13–17 years of age; adults, n = 14, 7 male, mean age 21.3, range 19–24 years of age. This three-group stratification is illustrative, but statistical analyses were conducted with age as a continuum.