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Episodic memory is critical to daily life functioning. This type of declarative memory declines with age and is the earliest cognitive function to be compromised in Alzheimer's disease (AD). Subjective memory complaints are commonly reported by older adults and have been considered a risk factor for developing AD. The possibilities for prevention of memory disorders in older adults have increased substantially in recent years. Previous studies have shown that anodal transcranial Direct Current Stimulation (tDCS) applied over the left lateral prefrontal cortex (PFC) after a contextual reminder strengthened existing verbal episodic memories, conceivably through reconsolidation, in elderly people. In this study, we hypothesized that anodal tDCS applied over the left lateral PFC after a contextual reminder would improve delayed memory retrieval relative to placebo (sham) stimulation in elderly individuals with SMC. Twenty-two subjects learned a list of words. Twenty-four hour later, tDCS (anodal or placebo) was applied over the left lateral PFC after a contextual reminder. Memory retrieval was tested 48h and 30 days later. These findings showed that anodal tDCS over the left lateral PFC strengthened existing episodic memories, a behavioral effect documented by improved recognition up to 30 days, relative to placebo stimulation. This study suggests that tDCS after a contextual reminder can induce long-lasting beneficial effects by facilitating the consolidation processes and opens up the possibility to design specific non-invasive interventions aimed at preventing memory decline in this at-risk population.

Background: The accurate choice of the site of non-invasive brain stimulation (NIBS) is an important factor in trial design. Objective: Based on the observation that Alzheimer's disease (AD) and behavioral frontotemporal dementia (bvFTD) affect specific large-scale networks, i.e., the default mode network (DMN) and the salience network (SN), respectively, we aimed to identify population-average coordinates of these networks that could be used as potential targets in NIBS trials aiming to modulate these circuits. Methods: A systematic literature search of resting-state functional MRI studies reporting DMN and SN stereotactic coordinates was performed according to PRISMA guidelines. Coordinate-based meta-analyses were conducted to identify consistent nodes of the DMN and SN using GingerALE BrainMap software and the activation likelihood estimation method. Results: DMN coordinates mapped primarily to mesial areas (posterior cingulate cortex/precuneus [Brodmann Area-BA 23/31] and medial prefrontal cortex [BA 9/10/32]). More superficial areas mapped to the bilateral parietal (angular gyrus [BA 39]), temporal (middle gyrus [BA 21]) and dorsolateral prefrontal (superior gyrus [BA 8]) cortex. SN coordinates mapped primarily to mesial and deep frontal areas (anterior insula, anterior cingulate cortex [BA 24/32]), but more superficial areas mapped to the bilateral parietal (supramarginal gyrus [BA 40]) and the right dorsolateral prefrontal (middle gyrus [BA 9/10]) cortex. Conclusions: NIBS should target the bilateral angular, the middle temporal cortex, or superior frontal gyri in AD for DMN modulation, and the right middle frontal or supramarginal gyri in bvFTD for SN modulation.

Emotional deficits are part of the non-motor features of Parkinson's disease but few attention has been paid to specific aspects such as subjective emotional experience and autonomic responses. This study aimed to investigate the mechanisms of emotional recognition in Parkinson's Disease (PD) using the following levels: explicit evaluation of emotions (Self-Assessment Manikin) and implicit reactivity (Skin Conductance Response; electromyographic measure of facial feedback of the zygomaticus and corrugator muscles). 20 PD Patients and 34 healthy controls were required to observe and evaluate affective pictures during physiological parameters recording. In PD, the appraisal process on both valence and arousal features of emotional cues were preserved, but we found significant impairment in autonomic responses. Specifically, in comparison to healthy controls, PD patients revealed lower Skin Conductance Response values to negative and high arousing emotional stimuli. In addition, the electromyographic measures showed defective responses exclusively limited to negative and high arousing emotional category: PD did not show increasing of corrugator activity in response to negative emotions as happened in heathy controls. PD subjects inadequately respond to the emotional categories which were considered more salient: they had preserved appraisal process, but impaired automatic ability to distinguish between different emotional contexts.

The present research explored the cortical correlates of emotional memories in response to words and pictures. Subjects’ performance (Accuracy Index, AI; response times, RTs; RTs/AI) was considered when a repetitive Transcranial Magnetic Stimulation (rTMS) was applied on the left dorsolateral prefrontal cortex (LDLPFC). Specifically, the role of LDLPFC was tested by performing a memory task, in which old (previously encoded targets) and new (previously not encoded distractors) emotional pictures/words had to be recognized. Valence (positive vs. negative) and arousing power (high vs. low) of stimuli were also modulated. Moreover, subjective evaluation of emotional stimuli in terms of valence/arousal was explored. We found significant performance improving (higher AI, reduced RTs, improved general performance) in response to rTMS. This “better recognition effect” was only related to specific emotional features, that is positive high arousal pictures or words. Moreover no significant differences were found between stimulus categories. A direct relationship was also observed between subjective evaluation of emotional cues and memory performance when rTMS was applied to LDLPFC. Supported by valence and approach model of emotions, we supposed that a left lateralized prefrontal system may induce a better recognition of positive high arousal words, and that evaluation of emotional cue is related to prefrontal activation, affecting the recognition memories of emotions.

The latency of visually guided saccades executed after a cueing condition was adopted as a more ecological index to explore how spatial attention, usually assessed by manual responses, operates in the visual field. Subjects executed saccades aimed towards one of 4 possible positions, equally distributed around a central fixation cross. Before the onset of the saccadic target, a visual cue was briefly presented at the same or at a different spatial location. The visual cue was non-predictive of the target position. Two experimental sessions were carried out, differing for the onset asynchrony between cue and target. A time-dependent coupling between the task-irrelevant location of the cue and the direction of a following overt shift of attention emerged. Clinical applications of the adopted experimental setting to neurological and psychiatric patients with motor impairments are discussed.