Multi-voxel pattern similarity analyses also revealed that anterior hippocampal patterns contained information about context during item recognition, and after a delay, context coding in this region was related to successful retention of context information.
Examples include HM who, after extended sample periods, showed normal levels of forced-choice recognition after a retention delay as long as 1 week (Freed et al., 1987).
The delayed recall and recognition conditions were administered after a delay of about 15 min, during this time other subtests from CMS were administered (for a summary of these findings see Lum, Conti-Ramsden, Page, et al., 2012).
Of particular note was that he displayed completely normal levels of forced-choice recognition memory after a retention delay of 24 h, which was demonstrably sufficient to eliminate ceiling effects (Vann et al., 2008).
Further analysis revealed that the recognition scores after a retention delay of 120 min of the control group were not significantly above chance while those scores of the HPC group were either above chance or at borderline levels, one-sample t-test, controls, D2 t < 1; D1, t < 1: HPC, D2 t(15) = 1.94, p =.036; D1 t(15) = 1.46, p =.08.
These data indicate that systemic activation of the D1 receptor transmission before the encoding tended to impair the recognition of a novel object after a delay of 24 h.
However, these studies have only examined recognition memory following a delay.
DOI: http://dx.doi.org/10.7554/eLife.05025.009 Because recognition accuracy was higher for items tested immediately than after a delay, findings of delay-dependent differences might be confounded by differences in the numbers of recollection and familiarity trials contributing to the analysis.
Participants successfully discriminated between intact and recombined sentences for both immediate, t(26) = 8.22, p < 0.001, and delayed test, t(26) = 8.17, p < 0.001, and again, associative recognition accuracy was higher for sentences tested immediately than after a delay, t(26) = 5.13, p < 0.001.
To assess the degree of incidental encoding for each item during the recognition test, participants were given a surprise post-test outside the scanner after a delay of approximately 5 min (getting out of the scanner).
In the spontaneous object recognition memory task animals are commonly presented with two identical objects and then after a delay period are presented with a third identical object and a novel object.
