Non-linear correlates of preference in the ventromedial prefrontal cortex during economical decision making

Purpose: Our objective was to examine the influence of implicit brand information on individual buying decisions.

Methods: Two separate cohorts (12 m, 10 f) had to make decisions between pairs of sensory similar consumer goods (m: 20 beer, f: 15 coffee brands) during fMRI (3T). The respective market leader was selected as a target brand (T), the others as diverse brands (D). We alternated blocks with 80% and 20% TD-decisions. Two weeks later individual brand preference was assessed by a questionnaire. Data analysis (SPM, general linear model) consisted of a fixed effects (FX), a random effects (RX), and a linear regression (LR) analysis.

Results: Only when T was a subject's favorite brand (“FCB“, 8 subjects), we found significant activation changes, which were largely congruent for the two genders/product types (FX and RX). Reduced activations were found in areas ascribed to working memory, planning and reasoning-based decision-making (bilaterally in Brodmann areas (BA) 9 and 46), BA 6 and BA 7/19). Cortical activity was increased in areas involved in episodic memory retrieval, self-reflection, integrating current inputs with background knowledge, and integration of emotions into decision-making (BA 7, 9, 40, and ventromedial prefrontal cortex (BA 10)). When T was rated 2nd or less, we did not find significant activation changes. There was no linear relationship between ranking of T and activation changes (LR).

Conclusion: We suggest two distinct decision modes in buying decisions, a more rational and a more emotional one. The latter is solely triggered by the individual's favorite brand, i.e. by implicit brand information.