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Objective: The aim of this study was to establish normative data for the Rey Auditory Verbal Learning Test, a test assessing verbal episodic memory, in the older French-Quebec population. Method: A total of 432 French-speaking participants aged between 55 and 93 years old, from the Province of Quebec (Canada), were included in the study. Using multiple regression analyses, normative data were developed for five variable of interest, namely scores on trial 1, sum of trials 1 to 5, interference list B, immediate recall of list A, and delayed recall of list A. Results: Results showed that age, education, and sex were associated with performance on all variables. Equations to calculate the expected score for a participant based on sex, age, and education level as well as the Z score were developed. Conclusion: This study provides clinicians with normative data that take into account the participants' sociodemographic characteristics, thus giving a more accurate interpretation of the results. [ABSTRACT FROM AUTHOR]

This research investigated the contribution of the dorsolateral prefrontal cortex (DLPFC) in the attentional resources in episodic encoding for both verbal and non-verbal material. Paired-pulse transcranial magnetic stimulations (TMS) were used to interfere transiently with either the left or right DLPFC during encoding under full attention (FA) or under divided attention (DA) in a recognition paradigm using words and random shapes. Participants recognized fewer items after TMS over the left DLPFC than over the right DLPFC during FA encoding. However, TMS over the left DLPFC did not impair performance when compared to sham condition. Conversely, participants produced fewer items after TMS over the right DLPFC in DA encoding compared to sham condition, but not compared to TMS over the left DLPFC. These effects were found for both words and random shapes. These results suggest that the right DLPFC play an important role in successful encoding with a concomitant task regardless of the type of material. [ABSTRACT FROM AUTHOR]

Abstract: Neuroimaging studies report that encoding and retrieval processes of episodic memory constantly activate the left and right prefrontal cortex, even in the simplest memory tasks. Conversely, individuals with frontal lesions displayed impaired memory performance mainly in the most complex memory tasks. This discrepancy regarding the involvement of dorsolateral prefrontal cortex (DLPFC) may be explained by methodological divergences. Our goal was to study the critical role of the DLPFC in episodic encoding and retrieval processes according to the nature of the material (verbal or non-verbal) by using transcranial magnetic stimulation (TMS). Eighteen healthy adults performed a recognition task with words or random shapes. Paired-pulse TMS was applied (3-ms inter-pulse interval, at 90% of motor threshold) for inducing transient and safe interferences over the left or right DLPFCs during encoding or retrieval. Data analysis showed a reduced discrimination rate following TMS over the left DLPFC during encoding, as compared to a sham condition. Both hit and discrimination rates were also reduced after TMS over the right DLPFC, compared to TMS over left DLPFC, during retrieval. There was no difference between verbal and non-verbal material. Our results showed that the left and the right DLPFC play a critical role respectively in episodic encoding and retrieval processes for both verbal and non-verbal materials. Our findings are discussed in light of the findings obtained from other complementary approaches. [Copyright &y& Elsevier]

Primary objective: The goal of the present study was to assess the impact of mild traumatic brain injury (MTBI) on episodic memory performance in relation to attentional and executive control processes in young adults. Research design/methods: A verbal memory paradigm manipulating attentional load (full attention or divided attention) and semantic congruency between pairs of category-target words during encoding was administrated to 13 individuals with MTBI and 12 normal control participants. Environmental supports during retrieval (free recall, cued recall and recognition modes) were also manipulated. Main outcomes and results: Results show that recall performances of individuals with MTBI were similar to those of controls when words were encoded under full attention. In contrast, individuals with MTBI performed worse than control participants when encoding under divided attention, whatever the semantic link between pairs of words. Conclusions: By using a sensitive test, one was able to objectively measure subtle impairments in memory performance, suggesting a diminished availability of attentional resources after MTBI. Young adults' learning of verbal material under divided attention might be compromised by the reduction of cognitive resources following MTBI. These findings are also discussed in light of different factors that can influence cognitive performance. [ABSTRACT FROM AUTHOR]

Abstract: Neuroimaging and neuropsychological data indicate that the frontal regions are implicated in semantic organizational strategies in verbal learning. Whereas these approaches tend to adopt a localizationist view, we used event-related potentials (ERPs) to investigate the dynamic neural mechanisms involved in these strategies. We recorded ERPs using a 128-channel system in 12 young adults (23.75±3.02 years) during 3 encoding conditions that manipulated the levels of semantic organization demands. In the Unrelated condition, the words to encode did not share any semantic attributes. For both Spontaneous and Guided conditions, the words in each list were drawn from four semantic categories. In the Spontaneous condition, participants were not informed about the semantic relationship between items. In contrast, in the Guided condition, participants were instructed to improve their subsequent recall by mentally regrouping related items with the aid of category labels. Results indicated that the P200 amplitude increased with the greater organizational demand of semantic strategies. In contrast, the late positive component (LPC) amplitude was larger in both encoding conditions with semantic related words regardless of their instructions as compared to the Unrelated condition. Finally, there was greater right frontal sustained activity in the Spontaneous condition than in the Unrelated condition. Thus, our data indicate that the P200 is sensitive to attentional processes that increase with the organizational semantic demand. The LPC indexes associative processes voluntarily involved in linking related items together. Finally, the right frontal region appears to play an important role in the self-initiation of semantic organizational strategies. [Copyright &y& Elsevier]

In the past 10 years, functional neuroimaging studies have elucidated the role of the prefrontal cortex in memory encoding and retrieval. However, it is still unclear whether these activations reflect item- or task-related activities. In the present study, Event-Related Potentials (ERPs) were used to distinguish item-related activity from task-related activity in both encoding and retrieval processes. This activity was assessed with both verbal and non-verbal material. A recognition paradigm with words or random shapes was administered to 12 young participants. Memory elicited ERPs were compared to those evoked by control tasks that used similar material. The distribution of the N400 was found to be larger on left frontal than right frontal areas for verbal material, however, this was the case in the control and memory conditions as well. This finding likely reflects the sensitivity of this component to processing verbal material. The LPC amplitude was greater in the non-verbal encoding than the non-verbal control condition, whereas in retrieval it was larger than the control condition for both verbal and non-verbal material. Thus, item-related activity is determined by an interaction between properties of the material and the task instructions. Task-related activity was found for non-verbal material: compared to the control condition, the memory condition of non-verbal material elicited bilateral and right frontal activity in encoding and retrieval processes. No task-related effect was reported with the verbal material. Material differences in eliciting task-related effects are discussed in terms of their relation to elaborative and effortful processes. [Copyright &y& Elsevier]

• Aging and TBI induce a synergic effect on the LPC and P200 ERPs components. • Older adults with TBI presented with a negative left frontal negativity. • TBI in older adults could exacerbated decline of executive attention. Episodic memory and attention impairments are frequently observed following a traumatic brain injury (TBI). Older adults are more affected than young adults after a TBI, partly because of the age-related neural and memory changes. Neural mechanisms underlying episodic memory deficits in older adults with chronic TBI remain to be investigated. The current study aimed to investigate the impact of TBI in older adults on the neural mechanisms of episodic encoding. Event-related potentials were recorded while 13 participants with mild-to-severe TBI and 14 matched controls were performing an episodic memory task in which the level of organizational strategy was manipulated through three encoding conditions. Participants were explicitly instructed to memorize words without any semantic relationship (Unrelated condition), words semantically related without any given strategies (Spontaneous condition) and words semantically related with provided category labels and organizational strategy (Guided condition). Behavioral performances indicated that older individuals with a TBI were impaired compared to matched controls whatever the condition. The electrophysiological findings showed a reduction of the P200 and LPC components amplitude in the TBI group relative to control group. Moreover, control participants without any neurological history showed a right frontal sustained activity only in the Spontaneous condition, whereas a right frontal asymmetry was observed in participants with chronic TBI whatever the encoding conditions. This was mainly the result of negative left frontal activity. These findings evidence neural dysfunctions underlying attentional and associative processes involved in memory strategies after a TBI sustained at an older age that are consistent with executive functions impairments. [ABSTRACT FROM AUTHOR]

Abstract: Transcranial magnetic stimulation (TMS) is a neurophysiological tool that can transiently influence brain excitability and improve cognitive performance. Facilitation effects induced by low frequency repetitive TMS on memory functions have been shown in a few studies in young and healthy participants and in older individuals with memory complaints . However, regions specifically involved in encoding and retrieval were not always systematically targeted. We thus aimed to facilitate episodic memory with online TMS systematically applied over the left or right dorsolateral prefrontal cortex (DLPFC) while participants were performing a recognition task. We applied online paired-pulse TMS (ppTMS) (15ms inter-stimulus interval) either during encoding or retrieving of verbal or non-verbal material. Participants were 11 right-handed young individuals (21.33±2.27 years old). Repeated measures ANOVA showed shorter reaction time when ppTMS are applied over the left DLPFC during encoding as compared to right homologous stimulation or to Sham condition. In contrast, ppTMS over the right DLPFC during retrieval was associated with shorter reaction times compared to left homologous stimulation. Overall, our data support for the first time that online ppTMS over the DLPFCs is capable of hastening memory processes in young and healthy individuals. [ABSTRACT FROM AUTHOR]