SUMMARY Long-term storage of episodic memories is hypothesized to result from the off-line transfer of information from the hippocampus to neocortex, allowing a hippocampal-independent cortical representation to emerge. However, off-line hippocampal-cortical interactions have not been demonstrated to be linked with long-term memory. Here, using functional magnetic resonance imaging, we examined if hippocampal-cortical BOLD correlations during rest following an associative encoding task are related to later associative memory performance. Our data show enhanced functional connectivity between the hippocampus and a portion of the lateral occipital complex (LO) during rest following a task with high subsequent memory compared to pre-task baseline resting connectivity. This effect is not seen during rest following a task with poor subsequent memory. Furthermore, the magnitude of hippocampal-LO correlations during post-task rest predicts individual differences in later associative memory. These results demonstrate, for the first time, the importance of post-experience resting brain correlations for memory for recent experiences.

The transformation of new experiences into lasting memories is thought to be mediated by postencoding reactivation or the reexpression of activity patterns that characterize prior encoding experiences during subsequent offline periods. Although hippocampal reactivation has been well-described in the rodent, evidence for postencoding persistence of hippocampal encoding patterns has yet to be described in humans. Using functional MRI, we examined the persistence of multivoxel hippocampal encoding patterns into postencoding rest periods. To characterize activity patterns, we computed the pairwise multivoxel correlation structure (MVCS) across hippocampal voxels during two distinct encoding tasks as well as during pre-and postencoding rest periods. We found that the hippocampal MVCS for each encoding task was more similar to the MVCS during immediate postencoding rest periods compared with a preencoding, baseline rest period. Additionally, using a principal component decomposition approach, we found that the strongest encoding patterns showed evidence of preferential persistence into immediate postencoding rest periods. Finally, the extent to which the strongest encoding patterns showed evidence of preferential persistence into immediate postencoding rest significantly correlated with later memory for stimuli seen during encoding. Taken together, these results provide strong evidence for hippocampal reactivation in humans, which was measured by the persistence of hippocampal encoding patterns into immediate postencoding rest periods, and importantly, provide a possible link between this persistence and memory consolidation.hippocampus | multivoxel pattern analysis | resting state O ur ability to remember a unique episode for days, months, and even years in the future is an impressive biological feat. Converging evidence across multiple species indicates that the hippocampus is essential for the initial formation of an episodic memory trace (1, 2). In addition to memory acquisition, the hippocampus is also thought to play a pivotal role in the postencoding stabilization of memories by restructuring how information is represented across hippocampal-neocortical networks (2-4). Specifically, hippocampal replay or the subsequent reactivation of patterns of hippocampal activity that characterize a prior experience (5-8) is hypothesized to contribute to memory consolidation (3,6,9).In line with these predictions, previous work in rodents has shown that multivariate patterns of hippocampal activity are reactivated during sleep (10-12) and awake periods (13-16). Critical for theories of consolidation, the extent of hippocampal reactivation in rodents has recently been related to spatial memory improvements (17), whereas interference with putative reactivation events leads to impairments in learning (18)(19)(20). Prior work in humans using functional MRI (fMRI) has shown that resting connectivity between the hippocampus and encoding-related cortical areas can be modulated by an associative encoding experience (21,22) and that...

Recent human fMRI studies provide evidence for spontaneous memory-related reactivation and hippocampal interactions during awake post-encoding time periods.

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Both emotion and visual processing deficits are documented in schizophrenia, and preferential magnocellular visual pathway dysfunction has been reported in several studies. This study examined the contribution to emotion-processing deficits of magnocellular and parvocellular visual pathway function, based on stimulus properties and shape of contrast response functions. Experiment 1 examined the relationship between contrast sensitivity to magnocellular- and parvocellular-biased stimuli and emotion recognition using the Penn Emotion Recognition (ER-40) and Emotion Differentiation (EMODIFF) tests. Experiment 2 altered the contrast levels of the faces themselves to determine whether emotion detection curves would show a pattern characteristic of magnocellular neurons and whether patients would show a deficit in performance related to early sensory processing stages. Results for experiment 1 showed that patients had impaired emotion processing and a preferential magnocellular deficit on the contrast sensitivity task. Greater deficits in ER-40 and EMODIFF performance correlated with impaired contrast sensitivity to the magnocellular-biased condition, which remained significant for the EMODIFF task even when nonspecific correlations due to group were considered in a step-wise regression. Experiment 2 showed contrast response functions indicative of magnocellular processing for both groups, with patients showing impaired performance. Impaired emotion identification on this task was also correlated with magnocellular-biased visual sensory processing dysfunction. These results provide evidence for a contribution of impaired early-stage visual processing in emotion recognition deficits in schizophrenia and suggest that a bottom-up approach to remediation may be effective.