Abstract
The influence of dietary choline availability on cognition is currently being suggested by animal and human studies which have focused mainly on the early developmental stages. The aim of this review is to systematically search through the available rodent (rats and mice) research published during the last two decades that has assessed the effect of dietary choline interventions on cognition and related attentional and emotional processes for the entire life span. The review has been conducted according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement guidelines covering peer-reviewed studies included in PubMed and Scopus databases. After excluding duplicates and applying the inclusion/exclusion criteria we have reviewed a total of 44 articles published in 25 journals with the contribution of 146 authors. The results are analyzed based on the timing and duration of the dietary intervention and the behavioral tests applied, amongst other variables. Overall, the available results provide compelling support for the relevance of dietary choline in cognition. The beneficial effects of choline supplementation is more evident in recognition rather than in spatial memory tasks when assessing nonpathological samples whilst these effects extend to other relational memory tasks in neuropathological models. However, the limited number of studies that have evaluated other cognitive functions suggest a wider range of potential effects. More research is needed to draw conclusions about the critical variables and the nature of the impact on specific cognitive processes. The results are discussed on the terms of the theoretical framework underlying the relationship between the brain systems and cognition.
Highlights
The interest for improving cognitive functions by dietary supplementation has increased over the last decades
A general overview of the results reported by the rodent studies reviewed confirms a beneficial effect of choline supplementation which is more evident in those tasks requiring long-term relational memory and those conditions associated with immature or impaired cognitive functions
Except in one case, no effect of choline supplementation on the standard Morris water-maze task has been reported in nonpathological conditions (Table 2), whilst enhanced performance in recognition memory tasks was obtained in studies performed by different laboratories with different retention intervals (Table 3)
Summary
The interest for improving cognitive functions by dietary supplementation has increased over the last decades. The evaluation of human studies is hindered by the difficulty of controlling a number of social, educational and economic factors. It is difficult because a wide variety of both supplemented diets with various combinations of ingredients and behavioral indexes are used [1]. Cognition is a poorly defined term which includes a variety of functions such as attention, learning and memory. Each of these functions can be dissociated in components depending on particular brain networks with different developmental courses. It has been pointed out that this makes it difficult to draw conclusions based on comparisons between different studies [2], and it is necessary to define the processes assessed by a particular behavioral test taking into account the underlying theoretical framework [3]
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