Dynamic changes in neural representations underlie the repetition effect on false memory

Effects of transcranial direct current stimulation combined with retrieval practice on semantic memory in patients with schizophrenia

BACKGROUND

The semantic processing deficit stands as a central feature of cognitive abnormalities in schizophrenia. Both transcranial direct current stimulation (tDCS) and retrieval practice have been demonstrated as external techniques capable of ameliorating the semantic processing deficit in individuals with schizophrenia. The inquiry examines whether the combined effect of tDCS and retrieval practice, following tDCS intervention targeting the left dorsolateral prefrontal cortex (L-DLPFC) in patients with schizophrenia, contributes to the preservation of semantic memory in these individuals.

METHODS

We recruited 52 patients diagnosed with schizophrenia from hospitals. After five consecutive days of tDCS intervention (2 mA × 20 mins, twice per day), we administered a word list memorization task comparing retrieval practice and restudy strategies. Subsequently, we observed their immediate and delayed memory performance through tests.

RESULTS

The semantic memory performance of the anodal group significantly surpassed that of the sham group. There was a significant interaction between stimulation type and learning strategy; regardless of the stimulation modality employed, retrieval practice outperformed restudy strategy. Notably, the semantic memory performance under retrieval practice conditions in the anodal group was significantly superior. ARC clustering scores fully mediate stimulus type and retrieval practice recall rates.

CONCLUSIONS

Continuous periodic tDCS has the potential to enhance the efficacy of retrieval practice strategy, particularly in aiding patients with schizophrenia to improve the maintenance of semantic memory and refine memory organization.

TRIAL REGISTRATION

The present trial has been registered in the American Registry of Clinical Trials Center (ID: NCT06538259|| http://clinicaltrials.gov/ ) (Retrospectively Registered Date: 08/03/2024).

Intrinsic functional connectivity in medial temporal lobe networks is associated with susceptibility to misinformation

Memory is notoriously fallible and susceptible to misinformation. Yet little is known about the underlying cognitive and neural mechanisms that render individuals vulnerable to this type of false memory. The current experiments take an individual differences approach to examine whether susceptibility to misinformation reflects stable underlying factors related to memory retrieval. In Study 1, we report for the first time the existence of substantial individual variability in susceptibility to misinformation in the context of repeated memory retrieval, when the misinformation effect is most pronounced. This variability was not related to an individual's tendency to adopt an episodic retrieval style during remembering (trait mnemonics). In Study 2, we next examined whether susceptibility to misinformation is related to intrinsic functional connectivity in medial temporal lobe (MTL) networks known to coordinate memory reactivation during event retrieval. Stronger resting-state functional connectivity between the MTL and cortical areas associated with visual memory reactivation (occipital cortex) was associated with better protection from misinformation. Together, these results reveal that while memory distortion is a universal property of our reconstructive memory system, susceptibility to misinformation varies at the individual level and may depend on one's ability to reactivate visual details during memory retrieval.