Emotional Context Shapes the Serial Position Curve.

Emotional contexts affect memory processes. However, the impact of contextual priming as a function of the emotional valence on the recall of neutral information is not fully understood. The aim of the present study was to evaluate how a conditioning of emotional context during encoding may influence the subsequent memory of otherwise neutral materials in a well-established phenomenon as the serial position effect. Participants performed a free recall task for neutral words in three conditions: (i) word list alone; (ii) word list coupled with positive or neutral images; and (iii) word list coupled with negative or neutral images. Images were presented before each word stimulus. In three different experiments, the emotional context during the word list presentation was manipulated separately for primacy and recency clusters, and for the middle words ('middlecy'). Emotional context affects free recall of neutral stimuli, changing the serial position curve effect across conditions. Namely, emotional images presented in the primacy and recency clusters worsen accuracy, whereas their occurrence in the 'middlecy' cluster reduces the oblivion. The present findings show that the typical pattern related to the serial position curve for neutral information can be shaped by the conditioning of emotional context. Findings have implications in medical-legal contexts in the case of the recollection of events with high emotional content.

Non-invasive brain stimulation of the aging brain: State of the art and future perspectives.

Favored by increased life expectancy and reduced birth rate, worldwide demography is rapidly shifting to older ages. The golden age of aging is not only an achievement but also a big challenge because of the load of the elderly on social and medical health care systems. Moreover, the impact of age-related decline of attention, memory, reasoning and executive functions on self-sufficiency emphasizes the need of interventions to maintain cognitive abilities at a useful degree in old age. Recently, neuroscientific research explored the chance to apply Non-Invasive Brain Stimulation (NiBS) techniques (as transcranial electrical and magnetic stimulation) to healthy aging population to preserve or enhance physiologically-declining cognitive functions. The present review will update and address the current state of the art on NiBS in healthy aging. Feasibility of NiBS techniques will be discussed in light of recent neuroimaging (either structural or functional) and neurophysiological models proposed to explain neural substrates of the physiologically aging brain. Further, the chance to design multidisciplinary interventions to maximize the efficacy of NiBS techniques will be introduced as a necessary future direction.

Individual factors enhance poor health-related quality of life outcome in multiple sclerosis patients. Significance of predictive determinants.

BACKGROUND: Individual factors in multiple sclerosis (MS) patients may modify the reliability of health-related quality of life (HRQOL) assessment. Knowledge of these effects may enable physicians to identify patients at risk for poor perceived health. OBJECTIVE: To investigate what individual factors may interact with MS symptoms and their severity to modify the reliability of HRQOL assessment; to explore the predictive values of the significant variables identified. METHODS: HRQOL was assessed in 57 patients by the 36-Item Short Form Health Survey (SF-36). The Physical Component Summary and Mental Component Summary were dichotomized and applied as dependent variables for logistic regression analysis. The Functional Independence Measure (FIM), Expanded Disability Status Scale (EDSS), Fatigue Severity Scale (FSS), Cognitive Behavioral Assessment (CBA) and specific individual factors were tested as independent variables. Two-way contingency tables were used to calculate the predictive values. RESULTS: Unemployment, smoking, and night waking were the most significant individual factors. Introversion, physical pain and difficulty falling asleep were also significant. EDSS-total ≥2, EDSS-pyramidal ≥2, FIM ≤123, FSS ≥5, depressive manifestations and bowel/bladder dysfunction were significant MS-related determinants. Sensitivity and specificity differed widely for each variable. CONCLUSIONS: Individual factors have relevance in HRQOL assessment. Their identification may help physicians construct the patient's risk profile. Sensitivity and specificity add weight to the significance of variables.

Role of the dorsal premotor cortex in rhythmic auditory-motor entrainment: a perturbational approach by rTMS.

Synchronization of body movements to an external beat is a universal human ability, which has also been recently documented in nonhuman species. The neural substrates of this rhythmic motor entrainment are still under investigation. Correlational neuroimaging data suggest an involvement of the dorsal premotor cortex (dPMC) and the supplementary motor area (SMA). In 14 healthy volunteers, we more specifically investigated the neural network underlying this phenomenon using a causal approach by an established 1-Hz repetitive transcranial magnetic stimulation (rTMS) protocol, which produces a focal suppression of cortical excitability outlasting the stimulation period. Synchronization accuracy between rhythmic cues and right index finger tapping, as measured by the mean time lag (asynchrony) between motor and auditory events, was significantly affected when the right dPMC function was transiently perturbed by "off-line" focal rTMS, whereas the reproduction of the rhythmic sequence per se (inter-tap-interval) was spared. This approach affected metrical rhythms of different complexity, but not non-metrical or isochronous sequences. Conversely, no change in auditory-motor synchronization was observed with rTMS of the SMA, of the left dPMC or over a control site (midline occipital area). Our data strongly support the view that the right dPMC is crucial for rhythmic auditory-motor synchronization in humans.

The effect of music on corticospinal excitability is related to the perceived emotion: a transcranial magnetic stimulation study.

Transcranial magnetic stimulation (TMS) and neuroimaging studies suggest a functional link between the emotion-related brain areas and the motor system. It is not well understood, however, whether the motor cortex activity is modulated by specific emotions experienced during music listening. In 23 healthy volunteers, we recorded the motor evoked potentials (MEP) following TMS to investigate the corticospinal excitability while subjects listened to music pieces evoking different emotions (happiness, sadness, fear, and displeasure), an emotionally neutral piece, and a control stimulus (musical scale). Quality and intensity of emotions were previously rated in an additional group of 30 healthy subjects. Fear-related music significantly increased the MEP size compared to the neutral piece and the control stimulus. This effect was not seen with music inducing other emotional experiences and was not related to changes in autonomic variables (respiration rate, heart rate). Current data indicate that also in a musical context, the excitability of the corticomotoneuronal system is related to the emotion expressed by the listened piece.

TMS interference with primacy and recency mechanisms reveals bimodal episodic encoding in the human brain.

A classic finding of the psychology of memory is the "serial position effect." Immediate free recall of a word list is more efficient for items presented early (primacy effect) or late (recency effect), with respect to those in the middle. In an event-related, randomized block design, we interfered with the encoding of unrelated words lists with brief trains of repetitive TMS (rTMS), applied coincidently with the acoustic presentation of each word to the left dorsolateral pFC, the left intraparietal lobe, and a control site (vertex). Interference of rTMS with encoding produced a clear-cut double dissociation on accuracy during immediate free recall. The primacy effect was selectively worsened by rTMS of the dorsolateral pFC, whereas recency was selectively worsened by rTMS of the intraparietal lobe. These results are in agreement with the double dissociation between short-term and long-term memory observed in neuropsychological patients and provide direct evidence of distinct cortical mechanisms of encoding in the human brain.

Cortico-Cortical Connectivity between Right Parietal and Bilateral Primary Motor Cortices during Imagined and Observed Actions: A Combined TMS/tDCS Study.

Previous transcranial magnetic stimulation (TMS) studies showed functional connections between the parietal cortex (PC) and the primary motor cortex (M1) during tasks of different reaching-to-grasp movements. Here, we tested whether the same network is involved in cognitive processes such as imagined or observed actions. Single pulse TMS of the right and left M1 during rest and during a motor imagery and an action observation task (i.e., an index-thumb pinch grip in both cases) was used to measure corticospinal excitability changes before and after conditioning of the right PC by 10 min of cathodal, anodal, or sham transcranial direct current stimulation (tDCS). Corticospinal excitability was indexed by the size of motor-evoked potentials (MEPs) from the contralateral first dorsal interosseous (FDI; target) and abductor digiti minimi muscle (control) muscles. Results showed selective ipsilateral effects on the M1 excitability, exclusively for motor imagery processes: anodal tDCS enhanced the MEPs' size from the FDI muscle, whereas cathodal tDCS decreased it. Only cathodal tDCS impacted corticospinal facilitation induced by action observation. Sham stimulation was always uneffective. These results suggest that motor imagery, differently from action observation, is sustained by a strictly ipsilateral parieto-motor cortex circuits. Results might have implication for neuromodulatory rehabilitative purposes.

Temporal dynamics of memory trace formation in the human prefrontal cortex.

Event-related repetitive transcranial magnetic stimulation (rTMS) can dynamically interfere with the memory encoding of complex visual scenes. Here, we investigated the critical time elapsing from stimulus presentation to the formation of an effective memory trace by delivering rTMS (900 ms at 20 Hz) during the encoding of visual scenes at different poststimulus delays (from 100 to 500 ms) in 28 healthy volunteers. The stimulation delay showed a robust inverse correlation with the correct retrieval of encoded images. In particular, rTMS stimulation delivered with a delay of 500 ms and lasting for 400 ms after stimulus offset resulted in a huge drop in retrieval accuracy. Such a timing suggests that rTMS affects the formation of long-term memory through interference with postperceptual executive processes, rather than with perceptual analysis of the stimuli. The effect was specific for stimulation of the left dorsolateral prefrontal cortex (DLPFC), whereas rTMS applied to the right DLPFC, vertex (active control site), as well as sham stimulation (placebo) did not affect accuracy. These results confirm the crucial role of the left DLPFC in encoding and provide novel information about the critical timing of its engagement in the formation, consolidation, and maintenance of the memory trace.

Event-related rTMS at encoding affects differently deep and shallow memory traces.

The "level of processing" effect is a classical finding of the experimental psychology of memory. Actually, the depth of information processing at encoding predicts the accuracy of the subsequent episodic memory performance. When the incoming stimuli are analyzed in terms of their meaning (semantic, or deep, encoding), the memory performance is superior with respect to the case in which the same stimuli are analyzed in terms of their perceptual features (shallow encoding). As suggested by previous neuroimaging studies and by some preliminary findings with transcranial magnetic stimulation (TMS), the left prefrontal cortex may play a role in semantic processing requiring the allocation of working memory resources. However, it still remains unclear whether deep and shallow encoding share or not the same cortical networks, as well as how these networks contribute to the "level of processing" effect. To investigate the brain areas casually involved in this phenomenon, we applied event-related repetitive TMS (rTMS) during deep (semantic) and shallow (perceptual) encoding of words. Retrieval was subsequently tested without rTMS interference. RTMS applied to the left dorsolateral prefrontal cortex (DLPFC) abolished the beneficial effect of deep encoding on memory performance, both in terms of accuracy (decrease) and reaction times (increase). Neither accuracy nor reaction times were instead affected by rTMS to the right DLPFC or to an additional control site excluded by the memory process (vertex). The fact that online measures of semantic processing at encoding were unaffected suggests that the detrimental effect on memory performance for semantically encoded items took place in the subsequent consolidation phase. These results highlight the specific causal role of the left DLPFC among the wide left-lateralized cortical network engaged by long-term memory, suggesting that it probably represents a crucial node responsible for the improved memory performance induced by semantic processing.