Abstract
Decisions differ in difficulty and rely on perceptual information that varies in richness (complexity); aging affects cognitive function including decision-making, and yet, the interaction between difficulty and perceptual complexity have rarely been addressed in aging. Using a parametric fMRI modulation analysis and psychophysics, we address how task difficulty affects decision-making when controlling for the complexity of the perceptual context in which decisions are made. Perceptual complexity was varied in a factorial design while participants made perceptual judgments on the spatial frequency of two patches that either shared the same orientation (simple condition) or were orthogonal in orientation (complex condition). Psychophysical thresholds were measured for each participant in each condition and served to set individualized levels of difficulty during scanning. Findings indicate that discriminability interacts with complexity, to influence decisional difficulty. Modulation as a function of difficulty is maintained with age, as indicated by coupling between increased activation in fronto-parietal regions and suppression in the lateral hubs, however, age has a specific effect in the ventral anterior cingulate cortex (ACC), driven by performance at near-threshold (difficult) levels for the simpler stimulus combination condition, but not the more complex one. Taken together, our findings suggest that the context of difficulty, or what is perceived as important, changes with age, and that decisions that would seem neutral to younger participants, may carry more emphasis with age.
Highlights
As we age, changes arise in visual perception (e.g., Sekuler and Sekuler, 2000; Owsley, 2011) and in cognitive function across domains (e.g., Buckner, 2004; Craik and Bialystok, 2006)
The only significant interaction was between age and similarity level (F1,18 = 11.5, p = 0.04), driven by slower response times in older participants when perceptual decisions were made at discrimination threshold levels (75% correct responses; Table 1)
This work shows that discriminability interacts with complexity, to influence decisional difficulty, and that age has a specific effect at near-threshold levels for simpler stimulus combinations in the ventral anterior cingulate cortex (ACC)
Summary
Changes arise in visual perception (e.g., Sekuler and Sekuler, 2000; Owsley, 2011) and in cognitive function across domains (e.g., Buckner, 2004; Craik and Bialystok, 2006). We make countless decisions of varying difficulty that rely on perceptual information, and yet, there has been little focus on the interaction between lower-level visual content and higher-level decision-making in aging. This fMRI study investigates how general task demand and complexity of visual content modulate perceptual decision making in aging. Decisional Difficulty Changes With Age. Tasks of executive control and decision-making involve prefrontal cortex (Rajah et al, 2008) along with fronto-striatal interactions when task demands increase (Rogers et al, 2000; Monchi et al, 2001, 2006). Tasks of executive function such as decision-making, generally rely on one type of difficulty, but task demands can arise from various sources and can be manipulated by visual perceptual content
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