Clinical and biomarker profiling of prodromal Alzheimer's disease in workpackage 5 of the Innovative Medicines Initiative PharmaCog project: a 'European ADNI study'.

BACKGROUND: In the field of Alzheimer's disease (AD), the validation of biomarkers for early AD diagnosis and for use as a surrogate outcome in AD clinical trials is of considerable research interest. OBJECTIVE: To characterize the clinical profile and genetic, neuroimaging and neurophysiological biomarkers of prodromal AD in amnestic mild cognitive impairment (aMCI) patients enrolled in the IMI WP5 PharmaCog (also referred to as the European ADNI study). METHODS: A total of 147 aMCI patients were enrolled in 13 European memory clinics. Patients underwent clinical and neuropsychological evaluation, magnetic resonance imaging (MRI), electroencephalography (EEG) and lumbar puncture to assess the levels of amyloid ß peptide 1-42 (Aß42), tau and p-tau, and blood samples were collected. Genetic (APOE), neuroimaging (3T morphometry and diffusion MRI) and EEG (with resting-state and auditory oddball event-related potential (AO-ERP) paradigm) biomarkers were evaluated. RESULTS: Prodromal AD was found in 55 aMCI patients defined by low Aß42 in the cerebrospinal fluid (Aß positive). Compared to the aMCI group with high Aß42 levels (Aß negative), Aß positive patients showed poorer visual (P = 0.001), spatial recognition (P < 0.0005) and working (P = 0.024) memory, as well as a higher frequency of APOE4 (P < 0.0005), lower hippocampal volume (P = 0.04), reduced thickness of the parietal cortex (P < 0.009) and structural connectivity of the corpus callosum (P < 0.05), higher amplitude of delta rhythms at rest (P = 0.03) and lower amplitude of posterior cingulate sources of AO-ERP (P = 0.03). CONCLUSION: These results suggest that, in aMCI patients, prodromal AD is characterized by a distinctive cognitive profile and genetic, neuroimaging and neurophysiological biomarkers. Longitudinal assessment will help to identify the role of these biomarkers in AD progression.

The detection of neural autoantibodies in patients with antiepileptic-drug-resistant epilepsy predicts response to immunotherapy.

BACKGROUND AND PURPOSE: The detection of antibodies binding neural antigens in patients with epilepsy has led to the definition of 'autoimmune epilepsy'. Patients with neural antibodies not responding to antiepileptic drugs (AEDs) may benefit from immunotherapy. Aim of this study was to evaluate the frequency of autoantibodies specific to neural antigens in patients with epilepsy and their response to immunotherapy. METHODS: Eighty-one patients and 75 age- and sex-matched healthy subjects (HS) were enrolled in the study. Two groups of patients were included: 39 patients with epilepsy and other neurological symptoms and/or autoimmune diseases responsive to AEDs (group 1) and 42 patients with AED-resistant epilepsy (group 2). Patients' serum and cerebrospinal fluid were evaluated for the presence of autoantibodies directed to neural antigens by indirect immunofluorescence on frozen sections of mouse brain, cell-based assays and a radioimmunoassay. Patients with AED-resistant epilepsy and neural autoantibodies were treated with immunotherapy and the main outcome measure was the reduction in seizure frequency. RESULTS: Neural autoantibodies were detected in 22% of patients (18/81), mostly from the AED-resistant epilepsy group (P = 0.003), but not in HS. Indirect immunofluorescence on mouse brain revealed antibodies binding to unclassified antigens in 10 patients. Twelve patients received immunotherapy and nine (75%) achieved >50% reduction in seizure frequency. CONCLUSIONS: A significant proportion of patients with AED-resistant epilepsy harbor neural-specific autoantibodies. The detection of these antibodies, especially of those binding to synaptic antigens, may predict a favorable response to immunotherapy, thus overcoming AED resistance.

Restoring bottom-up communication in brain-heart interplay after trauma-focused psychotherapy in breast cancer patients with post-traumatic stress disorder.

BACKGROUND: The psychological impact of breast cancer (BC) is substantial, with a significant number of patients (up to 32 %) experiencing post-traumatic stress disorder (PTSD). Exploring the emotional aspects of PTSD through the functional brain-heart interplay (BHI) offers valuable insights into the condition. BHI examines the functional interactions between cortical and sympathovagal dynamics. This study aims to investigate changes in functional directional BHI after trauma-focused (TF) psychotherapy, specifically Eye Movement Desensitization and Reprocessing (EMDR), in comparison to treatment as usual (TAU) among BC patients with PTSD. To our knowledge, this study represents the first examination of such changes. METHODS: We enrolled thirty BC patients who met the criteria for a PTSD diagnosis, with fourteen receiving EMDR and fifteen receiving TAU over a two- to three-month period. We analyzed changes in the emotional response during a script-driven imagery setting. Quantification of the functional interplay between EEG and sympathovagal dynamics was achieved using the synthetic data generation model (SDG) on electroencephalographic (EEG) and heartbeat series. Our focus was on the difference in the BHI index extracted at baseline and post-treatment. RESULTS: We found statistically significant higher coupling in the heart-to-brain direction in patients treated with EMDR compared to controls. This suggests that the flow of information from the autonomic nervous system to the central nervous system is restored following EMDR-induced recovery from PTSD. Furthermore, we observed a significant correlation between improvements in PTSD symptoms and an increase in functional BHI after EMDR treatment. CONCLUSIONS: TF psychotherapy, particularly EMDR, appears to facilitate the restoration of the bottom-up flow of interoceptive information, which is dysfunctional in patients with PTSD. The application of BHI analysis to the study of PTSD not only aids in identifying biomarkers of the disorder but also enhances our understanding of the changes brought about by TF treatments.

Functional and molecular evidence of myelin- and neuroprotection by thyroid hormone administration in experimental allergic encephalomyelitis.

AIMS: Recent data in mouse and rat demyelination models indicate that administration of thyroid hormone (TH) has a positive effect on the demyelination/remyelination balance. As axonal pathology has been recognized as an early neuropathological event in multiple sclerosis, and remyelination is considered a pre-eminent neuroprotective strategy, in this study we investigated whether TH administration improves nerve impulse propagation and protects axons. METHODS: We followed up the somatosensory evoked potentials (SEPs) in triiodothyronine (T3)-treated and untreated experimental allergic encephalomyelitis (EAE) Dark-Agouti female rats during the electrical stimulation of the tail nerve. T3 treatment started on the 10th day post immunization (DPI) and a pulse administration was continued until the end of the study (33 DPI). SEPs were recorded at baseline (8 DPI) and the day after each hormone/ vehicle administration. RESULTS: T3 treatment was associated with better outcome of clinical and neurophysiological parameters. SEPs latencies of the two groups behaved differently, being briefer and closer to control values (=faster impulse propagation) in T3-treated animals. The effect was evident on 24 DPI. In the same groups of animals, we also investigated axonal proteins, showing that T3 administration normalizes neurofilament immunoreactivity in the fasciculus gracilis and tau hyperphosphorylation in the lumbar spinal cord of EAE animals. No sign of plasma hyperthyroidism was found; moreover, the dysregulation of TH nuclear receptor expression observed in the spinal cord of EAE animals was corrected by T3 treatment. CONCLUSIONS: T3 supplementation results in myelin sheath protection, nerve conduction preservation and axon protection in this animal model of multiple sclerosis.

Spontaneous and TMS-related EEG changes as new biomarkers to measure anti-epileptic drug effects.

Robust biomarkers for anti-epileptic drugs (AEDs) activity in the human brain are essential to increase the probability of successful drug development. The frequency analysis of electroencephalographic (EEG) activity, either spontaneous or evoked by transcranial magnetic stimulation (TMS-EEG) can provide cortical readouts for AEDs. However, a systematic evaluation of the effect of AEDs on spontaneous oscillations and TMS-related spectral perturbation (TRSP) has not yet been provided. We studied the effects of Lamotrigine, Levetiracetam, and of a novel potassium channel opener (XEN1101) in two groups of healthy volunteers. Levetiracetam suppressed TRSP theta, alpha and beta power, whereas Lamotrigine decreased delta and theta but increased the alpha power. Finally, XEN1101 decreased TRSP delta, theta, alpha and beta power. Resting-state EEG showed a decrease of theta band power after Lamotrigine intake. Levetiracetam increased theta, beta and gamma power, while XEN1101 produced an increase of delta, theta, beta and gamma power. Spontaneous and TMS-related cortical oscillations represent a powerful tool to characterize the effect of AEDs on in vivo brain activity. Spectral fingerprints of specific AEDs should be further investigated to provide robust and objective biomarkers of biological effect in human clinical trials.

Stump nerve signals during transcranial magnetic motor cortex stimulation recorded in an amputee via longitudinal intrafascicular electrodes.

Do central and peripheral motor pathways associated with an amputated limb retain at least some functions over periods of years? This problem could be addressed by evaluating the response patterns of nerve signals from peripheral motor fibers during transcranial magnetic stimulation (TMS) of corticospinal tracts. The aim of this study was to record for the first time TMS-related responses from the nerves of a left arm stump of an amputee via intrafascicular longitudinal flexible multi-electrodes (tfLIFE4) implanted for a prosthetic hand control. After tfLIFE4 implant in the stump median and ulnar nerves, TMS impulses of increasing intensity were delivered to the contralateral motor cortex while tfLIFE4 recordings were carried out. Combining TMS of increasing intensity and tfLIFE4 electrodes recordings, motor nerve activity possibly related to the missing limb motor control and selectively triggered by brain stimulation without significant electromyographic contamination was identified. These findings are entirely original and indicate that tfLIFE4 signals are clearly driven from M1 stimulation, therefore witnessing the presence in the stump nerves of viable motor signals from the CNS possibly useful for artificial prosthesis control.

Free and Cued Selective Reminding Test: an Italian normative study.

The presence of episodic memory impairment is required for the diagnosis of Alzheimer's dementia by all current diagnostic criteria. The new research criteria proposed by Dubois et al. (Lancet Neurol 6:734-746, 2007) require that the impairment should not improve significantly with cueing, recognition testing nor after the control of effective encoding. This is considered to be the core deficit of "prodromal Alzheimer's disease". The Free and Cued Selective Reminding Test (FCSRT) is a memory test that allows in assessing these specific features of memory impairment. Here, we report normative data for an Italian version of the FCSRT. The test is based on the 12 pictorial stimuli, 6 belonging to the living domain, and 6 to the non-living domain. Six scores were derived from the performance of 227 healthy Italian adults, with age, sex and education homogenously distributed across subgroups: immediate free recall (IFR), immediate total recall (ITR), delayed-free recall (DFR), delayed total recall (DTR), Index of Sensitivity of Cueing (ISC), number of intrusions. In multiple regression analyses, age emerged as an influencing factor for both IFR and DFR, with older people obtaining lower scores. Education and gender appear to influence only IFR, with better performance by more educated subjects and females. Adjusted scores were used to determine inferential cutoff scores and to compute equivalent scores.

Cortical plasticity after hand prostheses use: Is the hypothesis of deafferented cortex "invasion" always true?

OBJECTIVE: To study motor cortex plasticity after a period of training with a new prototype of bidirectional hand prosthesis in three left trans-radial amputees, correlating these changes with the modification of Phantom Limb Pain (PLP) in the same period. METHODS: Each subject underwent a brain motor mapping with Transcranial Magnetic Stimulation (TMS) and PLP evaluation with questionnaires during a six-month training with a prototype of bidirectional hand prosthesis. RESULTS: The baseline motor maps showed in all three amputees a smaller area of muscles representation of the amputated side compared to the intact limb. After training, there was a partial reversal of the baseline asymmetry. The two subjects affected by PLP experienced a statistically significant reduction of pain. CONCLUSIONS: Two apparently opposite findings, the invasion of the "deafferented" cortex by neighbouring areas and the "persistence" of neural structures after amputation, could vary according to different target used for measurement. Our results do not support a correlation between PLP and motor cortical changes. SIGNIFICANCE: The selection of the target and of the task is essential for studies investigating motor brain plasticity. This study boosts against a direct and unique role of motor cortical changes on PLP genesis.

Early diagnosis of Alzheimer's disease: the role of biomarkers including advanced EEG signal analysis. Report from the IFCN-sponsored panel of experts.

Alzheimer's disease (AD) is the most common neurodegenerative disease among the elderly with a progressive decline in cognitive function significantly affecting quality of life. Both the prevalence and emotional and financial burdens of AD on patients, their families, and society are predicted to grow significantly in the near future, due to a prolongation of the lifespan. Several lines of evidence suggest that modifications of risk-enhancing life styles and initiation of pharmacological and non-pharmacological treatments in the early stage of disease, although not able to modify its course, helps to maintain personal autonomy in daily activities and significantly reduces the total costs of disease management. Moreover, many clinical trials with potentially disease-modifying drugs are devoted to prodromal stages of AD. Thus, the identification of markers of conversion from prodromal form to clinically AD may be crucial for developing strategies of early interventions. The current available markers, including volumetric magnetic resonance imaging (MRI), positron emission tomography (PET), and cerebral spinal fluid (CSF) analysis are expensive, poorly available in community health facilities, and relatively invasive. Taking into account its low cost, widespread availability and non-invasiveness, electroencephalography (EEG) would represent a candidate for tracking the prodromal phases of cognitive decline in routine clinical settings eventually in combination with other markers. In this scenario, the present paper provides an overview of epidemiology, genetic risk factors, neuropsychological, fluid and neuroimaging biomarkers in AD and describes the potential role of EEG in AD investigation, trying in particular to point out whether advanced analysis of EEG rhythms exploring brain function has sufficient specificity/sensitivity/accuracy for the early diagnosis of AD.

Implications of metal exposure and liver function in Parkinsonian patients resident in the vicinities of ferroalloy plants.

Valcamonica is an Italian valley where ferro-manganese industries have been active for a century and where an increased prevalence of parkinsonism was observed. A group of 93 patients (65 from Valcamonica, 28 from the reference area of Brescia city) and 76 controls (52 from Valcamonica, 24 from Brescia) were screened for serum Cu, Zn, Fe, Mn in blood (MnB) and urine (MnU), transferrin, peroxides, alanine (ALT) and aspartate (AST) transaminases and direct bilirubin. Test results were compared among groups according to the residential area and related to the disease severity. Valcamonica patients had a serum-increase of Cu, as well as of AST/ALT ratio, and a serum-decrease of Zn and Fe compared with other subgroups of cases and controls. Cases and controls from Valcamonica had higher MnB and MnU levels compared to cases and controls from Brescia. After controlling for the duration of illness, the Unified Parkinson's Disease Rating Scale III domain correlated with serum Cu and AST/ALT ratio. Our results suggest the possibility that, in this area, a lifetime exposure to neurotoxicants and to Mn in particular, when accompanied to a subclinical liver dysfunction, may pose an increased risk for neurodegenerative disorders via metal metabolism (Cu, Zn, Fe) abnormalities.

Characterization of multi-channel intraneural stimulation in transradial amputees.

Although peripheral nerve stimulation using intraneural electrodes has been shown to be an effective and reliable solution to restore sensory feedback after hand loss, there have been no reports on the characterization of multi-channel stimulation. A deeper understanding of how the simultaneous stimulation of multiple electrode channels affects the evoked sensations should help in improving the definition of encoding strategies for bidirectional prostheses. We characterized the sensations evoked by simultaneous stimulation of median and ulnar nerves (multi-channel configuration) in four transradial amputees who had been implanted with four TIMEs (Transverse Intrafascicular Multichannel Electrodes). The results were compared with the characterization of single-channel stimulation. The sensations were characterized in terms of location, extent, type, and intensity. Combining two or more single-channel configurations caused a linear combination of the sensation locations and types perceived with such single-channel stimulations. Interestingly, this was also true when two active sites from the same nerve were stimulated. When stimulating in multi-channel configuration, the charge needed from each electrode channel to evoke a sensation was significantly lower than the one needed in single-channel configuration (sensory facilitation). This result was also supported by electroencephalography (EEG) recordings during nerve stimulation. Somatosensory potentials evoked by multi-channel stimulation confirmed that sensations in the amputated hand were perceived by the subjects and that a perceptual sensory facilitation occurred. Our results should help the future development of more efficient bidirectional prostheses by providing guidelines for the development of more complex stimulation approaches to effectively restore multiple sensations at the same time.

Microbes and Alzheimer' disease: lessons from H. pylori and GUT microbiota.

OBJECTIVE: the role of microbes and chronic inflammation in the pathogenesis of Alzheimer' disease (AD) has been postulated by many authors. On the other hand, several studies have reported the main role of H. pylori infection and/or GUT microbiota alteration in promoting chronic inflammation, thus possibly influencing both occurrence and evolution of AD. In this article, we analyze the most important and recent studies performed on this field both on humans and animals and provide possible pathogenic explanations. RESULTS: all main and most recent animal, human, epidemiological and in-silico studies, showed a role of H. pylori and/or dysbiosis in AD, mostly through the promotion of systemic chronic inflammation and/or by triggering molecular mimicry mechanisms. In particular, H. pylori infection seems to be related to a poorer cognitive performance. CONCLUSIONS: Indeed, bacteria have been shown to affect neurodegeneration by promoting inflammation, inducing molecular mimicry mechanisms and accumulation of Aß into the brain. These findings open the way for H. pylori eradicating trials and/or GUT microbiota remodulating strategies. Therefore, further studies are now needed in order to test whether antibiotics, pre and/or probiotics may exert a beneficial effect in the prevention of AD.

Optimal integration of intraneural somatosensory feedback with visual information: a single-case study.

Providing somatosensory feedback to amputees is a long-standing objective in prosthesis research. Recently, implantable neural interfaces have yielded promising results in this direction. There is now considerable evidence that the nervous system integrates redundant signals optimally, weighting each signal according to its reliability. One question of interest is whether artificial sensory feedback is combined with other sensory information in a natural manner. In this single-case study, we show that an amputee with a bidirectional prosthesis integrated artificial somatosensory feedback and blurred visual information in a statistically optimal fashion when estimating the size of a hand-held object. The patient controlled the opening and closing of the prosthetic hand through surface electromyography, and received intraneural stimulation proportional to the object's size in the ulnar nerve when closing the robotic hand on the object. The intraneural stimulation elicited a vibration sensation in the phantom hand that substituted the missing haptic feedback. This result indicates that sensory substitution based on intraneural feedback can be integrated with visual feedback and make way for a promising method to investigate multimodal integration processes.

Methods for analysis of brain connectivity: An IFCN-sponsored review.

The goal of this paper is to examine existing methods to study the "Human Brain Connectome" with a specific focus on the neurophysiological ones. In recent years, a new approach has been developed to evaluate the anatomical and functional organization of the human brain: the aim of this promising multimodality effort is to identify and classify neuronal networks with a number of neurobiologically meaningful and easily computable measures to create its connectome. By defining anatomical and functional connections of brain regions on the same map through an integrated approach, comprising both modern neurophysiological and neuroimaging (i.e. flow/metabolic) brain-mapping techniques, network analysis becomes a powerful tool for exploring structural-functional connectivity mechanisms and for revealing etiological relationships that link connectivity abnormalities to neuropsychiatric disorders. Following a recent IFCN-endorsed meeting, a panel of international experts was selected to produce this current state-of-art document, which covers the available knowledge on anatomical and functional connectivity, including the most commonly used structural and functional MRI, EEG, MEG and non-invasive brain stimulation techniques and measures of local and global brain connectivity.

Sensorimotor integration in focal task-specific hand dystonia: a magnetoencephalographic assessment.

To obtain a direct sensorimotor integration assessment in primary hand cortical areas (M1) of patients suffering from focal task-specific hand dystonia, magnetoencephalographic (MEG) and opponens pollicis electromyographic (EMG) activities were acquired during a motor task expressly chosen not to induce dystonic movements in our patients, to disentangle abnormalities indicating a possible substrate on which dystonia develops. A simple isometric contraction was performed either alone or in combination with median nerve stimulation, i.e. when a non-physiological sensory inflow was overlapping with the physiological feedback. As control condition, median nerve stimulation was also performed at rest. The task was performed bilaterally both in eight patients and in 16 healthy volunteers. In comparison with results in controls we found that in dystonic patients: i) MEG-EMG coherence was higher; ii) it reduced much less during galvanic stimulation in the hemisphere contralateral to the dystonic arm, simultaneously with iii) stronger inhibition of the sensory areas responsiveness due to movement; iv) the cortical component including contributions from sensory inhibitory and motor structures was reduced and v) much more inhibited during movement. It is documented that a simultaneous cortico-muscular coherence increase occurs in presence of a reduced M1 responsiveness to the inflow from the sensory regions. This could indicate an unbalance of the fronto-parietal functional impact on M1, with a weakening of the parietal components. Concurrently, signs of a less differentiated sensory hand representation--possibly due to impaired inhibitory mechanisms efficiency--and signs of a reduced repertoire of voluntary motor control strategies were found.

Increased cerebral vasomotor reactivity in migraine with aura: an autoregulation disorder? A transcranial Doppler and near-infrared spectroscopy study.

Migraine with aura (MA) is associated with changes in cerebral blood flow (CBF), whereas the role of cerebral autoregulation is uncertain. This study aimed to evaluate basal CBF, cerebral blood volume (CBV) and vasomotor reactivity (VMR) in MA patients. Twenty-one controls and 16 MA patients (eight with side predominance) underwent simultaneous examination of flow velocity in the middle cerebral arteries by transcranial Doppler (TCD) and of near-infrared spectroscopy (NIRS) parameters [oxygen haemoglobin saturation: oxygen%, and total haemoglobin content (THC)] at rest and after hypercapnia. Cerebral VMR, THC and oxygen% increases were significantly greater on the predominant compared with the non-predominant migraine side, with both sides of patients without side predominance and with controls. These findings suggest altered autoregulation in MA patients, possibly secondary to impaired cerebrovascular autonomic control. Simultaneous TCD and NIRS investigation could represent a non-invasive approach to evaluate cerebral haemodynamics at the cortical and subcortical level.

Age dependence of primary motor cortex plasticity induced by paired associative stimulation.

OBJECTIVE: The increase of elderly population prompted growing research for the understanding of cerebral phenomena sustaining learning abilities, with inclusion of long-term potentiation (LTP)-like plasticity phenomena. Aim of the present study was to characterize LTP-like plasticity dependence on age and gender. METHODS: A LTP-like primary motor cortex plasticity inducing a potentiation of the motor evoked potential (MEP) to focal transcranial magnetic stimulation as a consequence of a paired associative stimulation (PAS) was induced in a 50 healthy subject cohort, equally distributed for gender and age groups (25 young subjects, mean age+/-SD=29.8+/-4.5 years; elderly 61.1+/-4.1 years). RESULTS: Resting motor thresholds' excitability level increased in the elderly group, the basal MEP did not depend on gender or age. The PAS-induced primary motor cortex (M1) plastic excitability modulation was similar in young females and males, while it decreased with age in females only. CONCLUSIONS: A reduction of the PAS-induced M1 plasticity in females after menopause was documented, possibly due to an impairment of intracortical excitatory network activity. SIGNIFICANCE: A LTP-like plasticity dependence on age was found in female only, suggesting caution in interpreting behavioural studies on learning abilities in dependence on age.

Recommendations for the clinical use of somatosensory-evoked potentials.

The International Federation of Clinical Neurophysiology (IFCN) is in the process of updating its Recommendations for clinical practice published in 1999. These new recommendations dedicated to somatosensory-evoked potentials (SEPs) update the methodological aspects and general clinical applications of standard SEPs, and introduce new sections dedicated to the anatomical-functional organization of the somatosensory system and to special clinical applications, such as intraoperative monitoring, recordings in the intensive care unit, pain-related evoked potentials, and trigeminal and pudendal SEPs. Standard SEPs have gained an established role in the health system, and the special clinical applications we describe here are drawing increasing interest. However, to prove clinically useful each of them requires a dedicated knowledge, both technical and pathophysiological. In this article we give technical advice, report normative values, and discuss clinical applications.

The contribution of TMS to frontotemporal dementia variants.

OBJECTIVE: Frontotemporal lobar degeneration (FTLD) includes different heterogeneous conditions mainly characterized by personality changes and cognitive deficits in language and executive functions; movement disorders have also been associated with FTLD. The present study aimed to measure the primary motor cortex (M1) inhibitory and facilitatory functions in patients affected by FTLD. MATERIALS AND METHODS: The study included 17 FTLD patients, 8 age-matched healthy controls and 8 Alzheimer's disease (AD) patients. Transcranial magnetic stimulation (TMS) was used to study intracortical inhibition (ICI) and facilitation (ICF) by using a double-pulse paradigm. RESULTS: FTLD patients were comparable with controls and AD patients for ICI and ICF. Corticobasal degeneration (CBD) patients presented significant reduced inhibition at ISI3; moreover two out of seven CBD patients had only ipsilateral responses. DISCUSSION: The present study reveals a selective impairment of M1 ICI inhibitory response in CBD, which may help in distinguishing among the FTLD clinical spectrum.

Prefrontal [correction of Prefontal] cortex in long-term memory: an "interference" approach using magnetic stimulation.

Neuroimaging has consistently shown engagement of the prefrontal cortex during episodic memory tasks, but the functional relevance of this metabolic/hemodynamic activation in memory processing is still to be determined. We used repetitive transcranial magnetic stimulation (rTMS) to transiently interfere with either left or right prefrontal brain activity during the encoding or retrieval of pictures showing complex scenes. We found that the right dorsolateral prefrontal cortex (DLPFC) was crucial for the retrieval of the encoded pictorial information, whereas the left DLPFC was involved in encoding operations. This 'interference' approach allowed us to establish whether a cortical area activated by a memory task actually contributes to behavioral performance.