Genome-wide QTL mapping across three tissues highlights several Alzheimer's and Parkinson's disease loci potentially acting via DNA methylation

DNA methylation (DNAm) is an epigenetic mark with essential roles in disease development and predisposition. Here, we created genome-wide maps of methylation quantitative trait loci (meQTL) in three peripheral tissues and used Mendelian randomization (MR) analyses to assess the potential causal relationships between DNAm and risk for two common neurodegenerative disorders, i.e. Alzheimer's disease (AD) and Parkinson's disease (PD). Genome-wide single nucleotide polymorphism (SNP; ~5.5M sites) and DNAm (~850K CpG sites) data were generated from whole blood (n=1,058), buccal (n=1,527) and saliva (n=837) specimens. We identified between 11 and 15 million genome-wide significant (p<10-14) SNP-CpG associations in each tissue. Combining these meQTL GWAS results with recent AD/PD GWAS summary statistics by MR strongly suggests that the previously described associations between PSMC3, PICALM, and TSPAN14 and AD may be founded on differential DNAm in or near these genes. In addition, there is strong, albeit less unequivocal, support for causal links between DNAm at PRDM7 in AD as well as at KANSL1/MAPT in AD and PD. Our study adds valuable insights on AD/PD pathogenesis by combining two high-resolution "omics" domains, and the meQTL data shared along with this publication will allow like-minded analyses in other diseases.

Genome-Wide Association Study of Alzheimer's Disease Brain Imaging Biomarkers and Neuropsychological Phenotypes in the European Medical Information Framework for Alzheimer's Disease Multimodal Biomarker Discovery Dataset

Alzheimer's disease (AD) is the most frequent neurodegenerative disease with an increasing prevalence in industrialized, aging populations. AD susceptibility has an established genetic basis which has been the focus of a large number of genome-wide association studies (GWAS) published over the last decade. Most of these GWAS used dichotomized clinical diagnostic status, i.e., case vs. control classification, as outcome phenotypes, without the use of biomarkers. An alternative and potentially more powerful study design is afforded by using quantitative AD-related phenotypes as GWAS outcome traits, an analysis paradigm that we followed in this work. Specifically, we utilized genotype and phenotype data from n = 931 individuals collected under the auspices of the European Medical Information Framework for Alzheimer's Disease Multimodal Biomarker Discovery (EMIF-AD MBD) study to perform a total of 19 separate GWAS analyses. As outcomes we used five magnetic resonance imaging (MRI) traits and seven cognitive performance traits. For the latter, longitudinal data from at least two timepoints were available in addition to cross-sectional assessments at baseline. Our GWAS analyses revealed several genome-wide significant associations for the neuropsychological performance measures, in particular those assayed longitudinally. Among the most noteworthy signals were associations in or near EHBP1 (EH domain binding protein 1; on chromosome 2p15) and CEP112 (centrosomal protein 112; 17q24.1) with delayed recall as well as SMOC2 (SPARC related modular calcium binding 2; 6p27) with immediate recall in a memory performance test. On the X chromosome, which is often excluded in other GWAS, we identified a genome-wide significant signal near IL1RAPL1 (interleukin 1 receptor accessory protein like 1; Xp21.3). While polygenic score (PGS) analyses showed the expected strong associations with SNPs highlighted in relevant previous GWAS on hippocampal volume and cognitive function, they did not show noteworthy associations with recent AD risk GWAS findings. In summary, our study highlights the power of using quantitative endophenotypes as outcome traits in AD-related GWAS analyses and nominates several new loci not previously implicated in cognitive decline.

Anterior Frontal Cortex and the Effect of Proactive Interference in Paired Associate Learning: A DC Potential Study

This contribution focuses on neurophysiological correlates of the cerebral processes subserving the control of proactive interference. Event-related negative shifts of the scalp-recorded cortical steady potential (negative DC shifts) were measured in 17 right-handed normals during two tasks of paired associate learning. The control condition was a standard word pair learning task in which unrelated word pairs were presented. In the experimental condition, proactive interference was maximized by presenting very similar words and by requiring negative transfer, i.e., by having them reappear, but in different pairings. Proactive interference leads to increased anterior frontal negative DC shifts. Furthermore, centrotemporal negative DC shifts predicted subsequent cued recall performance. In spite of elaborative strategies, an effect of subsequent mnestic performance on the P300 was observed.

Bereitschaftspotential as an indicator of movement preparation in supplementary motor area and motor cortex

Topographical studies in humans of the Bereitschaftspotential (BP, or readiness potential, as averaged from the electroencephalogram) and the Bereitschaftsmagnetfeld (BM, or readiness magnetic field, as averaged from the magnetoencephalogram) revealed a widespread distribution of motor preparation over both hemispheres even before unilateral movement. This indicates the existence of several generators responsible for the BP, including generators in the ipsilateral hemisphere, which is in agreement with measurements of regional cerebral blood flow or regional cerebral energy metabolism. Nevertheless, two principal generators seem to prevail: (1) An early generator, starting its activity 1s or more before the motor act, with its maximum at the vertex. For this and other reasons, early BP generation probably stems from cortical tissue representing or including the supplementary motor area (SMA). (2) A later generator, starting its activity about 0.5s before the onset of movement and biased towards the contralateral hemisphere (contralateral preponderance of negativity, CPN). For unilateral finger movements the CPN succeeds the BP's initial bilateral symmetry in the later preparation period. Thus, this lateralized BP component probably stems from the primary motor area, MI (area 4, hand representation). While regional cerebral blood flow or regional cerebral energy metabolism show that the SMA is active in conjunction with motor acts, these data do not permit the conclusion that SMA activity precedes motor acts. This can only be shown by the Bereitschaftspotential, which proves that SMA activity occurs before the onset of movement and, what is more, before the onset of MI activity. This important order of events (first SMA, then MI activation) has been elucidated by our BP studies. It gives the SMA an important functional role: the initiation of voluntary movement. The recording of movement-related potentials associated with manual hand-tracking and motor learning points to the SMA and frontal cortex having an important role in these functions.

Neuropsychological Outcome 6 Months after Unilateral Carotid Stenting

Percutaneous transluminal angioplasty with stenting (PTAS) has become a treatment option for severe carotid stenosis. The goal of our study was to determine prospectively neurocognitive outcome 6 months after unilateral stent-protected carotid angioplasty. Twenty consecutive patients who underwent stent-protected angioplasty for symptomatic (n=9) or asymptomatic (n=11) high-grade carotid stenosis were investigated and compared to an age and disease matched control group. Patients were administered preprocedurally and 6 months postprocedurally a battery of neuropsychological tests. We used reliable change indices methodology in order to control for practice and statistical effects unrelated to intervention. We found no cognitive change in approximately 90% of patients and cognitive improvement in approximately 10% of patients for concentration and attention variables. We further found no cognitive change in 61% of patients, cognitive improvement in 11% of patients and cognitive deterioration in 28% of patients for psychomotor speed. No cognitive change in 94% of patients and cognitive deterioration in 6% of patients was found for sustained attention; no cognitive change in 80% of patients, cognitive improvement in 15% of patients and cognitive deterioration in 5% of patients was found for verbal fluency; no cognitive change in 100% of patients was found for interference (Stroop test): no cognitive change in 95% of patients, cognitive improvement in 5% of patients was found for interference (c.I. test), respectively. Our study showed that 6 months after PTAS cognitive functioning did not change in most patients significantly. For some patients, however, significant improvement or deterioration in single neurocognitive domains can be expected. The reasons for these changes are unclear but may depend on variable type; magnitude of microemboli production; right vs. left cerebral vasculature, respectively.

Sensory-specific satiety with simple foods in humans: no influence of BMI?

OBJECTIVE

Olfacto-gustatory sensory-specific satiety plays an important role in the termination of food ingestion. A defect in this mechanism, by increasing food intake, could be a factor in development of overweight. The present study was conducted to explore whether sensory-specific satiety in the overweight may be different from that in normal-weight subjects.

SUBJECTS

144 subjects (half men, half women; age range: 17-62 years; BMI range: 17-39 kg m(-2)).

MEASUREMENTS

Olfactory pleasure (OP) and flavor pleasure (FP) were evaluated before and after ingestion of a single chosen food. Six foods from three classes were offered: cucumber and tomato, pineapple and banana, and peanut and pistachio. According to the subjects' preference for one of them, subjects were classified into six groups (24 subjects each with equal sex ratio). The experimental sequence was (1) evaluation of the six foods (OP), (2) ad libitum intake of the preferred food (FP) and (3) second evaluation of the six foods (OP).

RESULTS

Food intake was limited by sensory-specific satiety (that is, a decline in FP for the ingested food) in overweight subjects just as it was in the leanest. There was no significant correlation between BMI and hedonic parameters (OP and FP) or intakes (quantity and volume). Pre-ingestive OP and FP correlated with the ingested food's weight (OP: r=0.468; FP: r=0.415; P<0.01), volume (OP: r=0.428; FP: r=0.407; P<0.01) and intake duration (OP: r=0.184; FP: r=0.343; P<0.05). The decline in OP, but not in FP, correlated with ingested weight (r=0.271, P<0.01) and volume (r=0.263, P<0.01) but not with duration.

CONCLUSION

After intake of a single food, olfacto-gustatory sensory-specific satiety correlated with the ingested food's weight and volume and with the duration of ingestion, but not with bodyweight. This suggests that overweight and lean subjects have similar hedonic control of food intake with simple foods.

EEG evidence of gender differences in a motor related CNV study

In the present study gender differences related to the contingent negative variation (CNV) were investigated. A series of two acoustic stimuli was presented to participants across a wide age range. The first stimulus was consistent throughout the experiment whereas the second one was either a high frequency or a low frequency tone. One of them had to be answered by a button press (go condition) the other did not require any response (nogo condition). Between the first and the second tone there was a time period of two seconds in which the CNV appeared as a slow negative potential shift. Within this episode data were analysed with respect to gender differences. Statistical analysis revealed topographical differences between men and women in go conditions for both left and right index finger movements. Differences were found over frontal regions where women showed higher brain activity than men and over temporo-parietal regions where men produced higher brain activity than women. In order to explain the fact that only in "go" conditions significant gender differences occurred we introduce the phenomenon of implicit learning. Due to implicit learning assumed predictions related to S2 might have occurred from time to time. This is so, because a 50% chance for one of two different stimuli to occur leads to reasonable assumed predictions after two or more stimuli of a kind occurring in a series. The present data now provide evidence that if such assumed prediction or expectancy is directed towards an upcoming demand to act then brain activity is subject to gender differences. Further studies providing controlled sequences of "go" conditions versus "nogo" conditions have to be done to prove this idea true.

Ambient odors of orange and lavender reduce anxiety and improve mood in a dental office

The goal of this study was to investigate the impact of the essential oils of orange and lavender on anxiety, mood, alertness and calmness in dental patients. Two hundred patients between the ages of 18 and 77 years (half women, half men) were assigned to one of four independent groups. While waiting for dental procedures patients were either stimulated with ambient odor of orange or ambient odor of lavender. These conditions were compared to a music condition and a control condition (no odor, no music). Anxiety, mood, alertness and calmness were assessed while patients waited for dental treatment. Statistical analyses revealed that compared to control condition both ambient odors of orange and lavender reduced anxiety and improved mood in patients waiting for dental treatment. These findings support the previous opinion that odors are capable of altering emotional states and may indicate that the use of odors is helpful in reducing anxiety in dental patients.

Magnetoencephalographic correlates of different levels in subjective recognition memory

In our current study we employed whole-head magnetoencephalography (MEG) to identify neurophysiological correlates (event-related fields, ERFs) of different phenomenologies in human recognition memory. Words which had previously been semantically processed were presented along with previously unstudied words. Via button presses, participants provided subjective indices of three forms of memory: confident recognition, familiarity-based recognition, and misclassification of previously presented items as new (no recognition, misses). Behavioral results revealed a clear distinction between confident recognition (shortest reaction times) and familiarity-based recognition and misses, respectively, and physiological data pointed to bilateral anterior and left anterior/central regions in which magnetic field patterns were directly related to word recognition from approximately 300 ms to 500 ms after word onset. In the context of the prevalent dual process controversy on the roles of familiarity and recollection in recognition memory, we first highlight that two operationalizations of recollection need to be differentiated: We argue that a strategic search for a particular contextual feature stands in clear contrast to the fast and incidental availability of some contextual feature and derive experimental and behavioral indicators for either form of recollection. These indicators are used to select from manifold cognitive neuroscientific work on recognition memory in order to further discuss the neurocognitive characteristics of incidental recollection in contrast to other forms of episodic memory.

Neurocognitive correlates of incidental verbal memory encoding: a magnetoencephalographic (MEG) study

In our current study, we applied whole head magnetoencephalography (MEG) in a subsequent memory paradigm. Magnetic fields were recorded while 20 healthy subjects (10 females, 10 males) incidentally encoded words during semantic and structural verbal processing tasks. Physiological data were then sorted according to the performance in subsequent memory tests and according to levels of processing, respectively, and analyzed for gender effects. Behavioral results show a clear advantage of semantic processing over structural processing with respect to retrieval success for both females and males. Despite alikeness of behavioral data, MEG results show considerable differences between males and females concerning both subsequent memory effects and levels of processing effects. For male subjects, we identified more distinct magnetic fields in anterior regions for subsequently remembered than for subsequently forgotten words (latency range from 300-650 ms after word onset) and for semantic processing than for structural processing, respectively. For female subjects, corresponding magnetic field differences pointed to posterior regions (subsequent memory effects from 450 ms to 750 ms after word onset). No qualitative differences were observed between subsequent memory effects during semantic processing compared to subsequent memory effects during structural processing. We try to reconcile results from male data with previous findings concerning subsequent memory effects by proposing the concept of width of processing, which holds that incidental memory formation is mediated by frontal activity on a physiological level and brought forward on a cognitive level by enhanced associating imposed by the task demands of semantic processing. Female data cannot be fully incorporated in this framework, but all the more prompt further gender-specific analyses of subsequent memory effects.

Depth of word processing in Alzheimer patients and normal controls: a magnetoencephalographic (MEG) study

Effects related to depth of verbal information processing were investigated in probable Alzheimer's disease patients (AD) and age matched controls. During word encoding sessions 10 patients and 10 controls had either to decide whether the letter "s" appeared in visually presented words (alphabetical decision, shallow encoding), or whether the meaning of each presented word was animate or inanimate (lexical decision, deep encoding). These encoding sessions were followed by test sessions during which all previously encoded words were presented again together with the same number of new words. The task was then to discriminate between repeated and new words. Magnetic field changes related to brain activity were recorded with a whole cortex MEG.5 probable AD patients showed recognition performances above chance level related to both depths of information processing. Those patients and 5 age matched controls were then further analysed. Recognition performance was poorer in probable AD patients compared to controls for both levels of processing. However, in both groups deep encoding led to a higher recognition performance than shallow encoding. We therefore conclude that the performance reduction in the patient group was independent of depth of processing. Reaction times related to false alarms differed between patients and controls after deep encoding which perhaps could already be used for supporting an early diagnosis. The analysis of the physiological data revealed significant differences between correctly recognised repetitions and correctly classified new words (old/new-effect) in the control group which were missing in the patient group after deep encoding. The lack of such an effect in the patient group is interpreted as being due to the respective neuropathology related to probable AD. The present results demonstrate that magnetic field recordings represent a useful tool to physiologically distinguish between probable AD and age matched controls.

Magnetoencephalographic—Features related to mild cognitive impairment

We recorded changes of brain activity from 10 MCI patients and 10 controls related to shallow (nonsemantic) and deep (semantic) word encoding using a whole-head MEG. During the following recognition tasks, all participants had to recognize the previously encoded words, which were presented again together with new words. In both groups recognition performance significantly varied as a function of depth of processing. No significant differences were found between the groups. Reaction times related to correctly classified new words (correct rejections) and incorrectly classified repetitions (misses) of MCI patients showed a strong tendency toward prolongation compared to controls, although no statistically significant differences occurred. Strikingly, in patients the neurophysiological data associated with nonsemantic and semantic word encoding differed significantly between 250 and 450 ms after stimulus onset mainly over left frontal and left temporal sensors. They showed higher electrophysiological activation during shallow encoding as compared to deep encoding. No such significant differences were found in controls. The present results might reflect a dysfunction with respect to shallow encoding of visually presented verbal information. It is interpreted that additional neural activation is needed to compensate for neurodegeneration. This finding is suggested to be an additional tool for MCI diagnosis.

Preserved memory traces within diencephalic amnesia

A male patient with bilateral thalamic lesions (medio-ventral nuclei) was investigated. Despite explicit memory impairments his lexical ability was normal. We recorded magnetic field changes (magnetoencephalography, MEG) during the performance of an animate/inanimate discrimination task in which some words where repeated after long delays. Normally, repeated items are classified significantly faster than their first presentations which is accomplished by an unconscious process called priming. The patient did not show any behavioural evidence of priming but the physiological data indicated preservation of this robust form of memory. Brain activation associated with repetitions was attenuated at early stages. The activity difference was posteriorly distributed which is consistent with previous reports about repetition priming. The present study indicated that the bilateral thalamic lesions of our patient disconnected the information processing stream between the primed information and the behavioural response.

Increased levels of the pro-inflammatory prostaglandin PGE2 in CSF from ALS patients

Levels of the potent pro-inflammatory prostaglandin E(2) (PGE(2)) are elevated in postmortem spinal cords from patients with ALS, and inhibition of a key PGE(2)-synthesizing enzyme, cylcooxygenase-2, is neuroprotective in an in vitro model of ALS. The authors report that 82% of the patients with ALS studied had 2 to 10 times higher PGE(2) levels in CSF compared with normal control subjects. That affected areas of the CNS are inflamed in ALS supports this. CSF PGE(2) measurement may be useful in monitoring treatment for ALS.

The preparation and execution of self-initiated and externally-triggered movement: a study of event-related fMRI

Studies of functional brain imaging in humans and single cell recordings in monkeys have generally shown preferential involvement of the medially located supplementary motor area (SMA) in self-initiated movement and the lateral premotor cortex in externally cued movement. Studies of event-related cortical potentials recorded during movement preparation, however, generally show increased cortical activity prior to self-initiated movements but little activity at early stages prior to movements that are externally cued at unpredictable times. In this study, the spatial location and relative timing of activation for self-initiated and externally triggered movements were examined using rapid event-related functional MRI. Twelve healthy right-handed subjects were imaged while performing a brief finger sequence movement (three rapid alternating button presses: index-middle-index finger) made either in response to an unpredictably timed auditory cue (between 8 to 24 s after the previous movement) or at self-paced irregular intervals. Both movement conditions involved similar strong activation of medial motor areas including the pre-SMA, SMA proper, and rostral cingulate cortex, as well as activation within contralateral primary motor, superior parietal, and insula cortex. Activation within the basal ganglia was found for self-initiated movements only, while externally triggered movements involved additional bilateral activation of primary auditory cortex. Although the level of SMA and cingulate cortex activation did not differ significantly between movement conditions, the timing of the hemodynamic response within the pre-SMA was significantly earlier for self-initiated compared with externally triggered movements. This clearly reflects involvement of the pre-SMA in early processes associated with the preparation for voluntary movement.

Dissociation of supplementary motor area and primary motor cortex in human subjects when comparing index and little finger movements with functional magnetic resonance imaging

This study provides the first investigation of supplementary motor area (SMA) and primary motor cortex (MI) activation with similar movements differing only in subjective difficulty of motor control. Brain activation with simple tapping of the right index finger (well trained during daily life and easy to perform) was compared with tapping of the little finger (less trained and difficult to perform) using functional magnetic resonance imaging at 3 Tesla. Due to optimised movement standardisation, extrinsic influences on activation levels such as movement complexity, amplitude and frequency were minimised. Fifth finger tapping significantly increased the number of activated SMA voxels by 450% whereas MI activation showed no significant difference between fingers. We conclude that with similar movements the degree of subjective difficulty specifically modifies SMA but not MI activation.

Amantadine in Parkinson's disease: lymphocyte subsets and IL-2 secreting T cell precursor frequencies

The antiviral drug amantadine, that is effective in idiopathic Parkinson's disease (PD), may affect the composition and function of peripheral blood lymphocytes. In an explorative study, we therefore compared lymphocyte subpopulations and IL-2 secreting T cell precursors frequencies (HTLp-frequencies) in 15 PD patients without amantadine and six patients on long-term treatment. Five patients were investigated before and three months after the start of treatment. Group comparisons for long-term amantadine treatment showed no differences in subpopulations of B-, T-, and NK cells, and HTLp-frequencies. However, three months after initiation of treatment we noted in all five patients an increase of CD3+CD4+ and decrease of CD3+CD8+ cells, associated with an increase of the CD3+CD4+/CD3+CD8+ ratio. These changes had no effect on the HTLp-frequencies. Thus, at least for a short period of time, amantadine improves the T cell mediated immune system in PD patients.

Bilateral subthalamic nucleus stimulation does not improve prolonged P300 latencies in Parkinson's disease

Bilateral deep brain stimulation is an effective treatment for most motor signs of Parkinson's disease (PD), but the effects on cognitive functions are less clear. We therefore examined the effects of bilateral deep brain stimulation on central information processing, using the event-related auditory P300 potential as an electrophysiological index of mental chronometry. Eight PD patients with bilateral stimulators within the subthalamic nuclei (STN) and eight age-matched controls participated. Patients were examined after overnight withdrawal of antiparkinson medication, both "on" and "off" stimulation (in random sequence). The P300 and reaction times were recorded using an auditory oddball paradigm. P300 latencies were prolonged in PD patients off stimulation (440 +/- 45 ms) compared to controls (397 +/- 16 ms; P < 0.05). STN stimulation significantly reduced clinical disease severity (as indexed by the Unified Parkinson's Disease Rating Scale) and markedly improved reaction times, but did not improve the prolonged P300 latencies in PD patients (429 +/- 36 ms). These results confirm that P300 latencies are prolonged in PD. Significantly, bilateral STN stimulation did not improve this electrophysiological measure of cognitive impairment, even though motor disability was markedly reduced. This suggests that some dopa-responsive features are resistant to STN stimulation, possibly due to involvement of dopaminergic deficits outside the nigrostriatal pathway, which are not influenced by outflow from the STN.

Neuromagnetic activity in alpha and beta bands reflect learning-induced increases in coordinative stability

OBJECTIVE

To investigate how learning induced increases in stability on a syncopation task are manifest in the dynamics of cortical activity.

METHOD

Magnetoencephalography was recorded from 143 sensors (CTF Systems, Inc). A pre-training procedure determined the critical frequency (F(c)) for each subject (n=4). Subjects either syncopated or synchronized to a metronome that increased in frequency from 1.2 to 3.0 Hz in 0.2 Hz steps. The F(c) was the point at which subjects spontaneously switched from syncopation to synchronization. Subjects then underwent 100 training trials (with feedback) at F(c). Following the learning phase the pre-training procedure was repeated.

RESULTS

An increase in the F(c) occurred indicating that practice improved the stability of syncopation. The transition delay was also observed in the phase of the time-averaged signal in sensors over the contralateral sensorimotor area and in power analysis in the 8-12 Hz and 18-24 Hz frequency bands. Initially, reduced power was observed bilaterally during syncopation compared to synchronization. Following training, these differences were reduced or eliminated.

CONCLUSION

Pre-training power differences can be explained by the greater difficulty of the syncopation task. The reduction in power differences following training suggests that at the cortical level, syncopation became more similar to synchronization possibly reflecting a decrease in task and/or attention demands.

Idiothetic orientation and path integration in unilateral hippocampal atrophy and sclerosis

We determined the effects of hippocampal lesions on idiothetic spatial orientation by exposing 14 patients with unilateral hippocampal atrophy and/or sclerosis (HAS) and 10 normal controls to random rotational displacements (+/-30 degrees -180 degrees ) in darkness and examined their ability to rotate themselves back to the initial position. In comparison to controls, the patients responses were distinctly hypometric (p<0.005). Patients with right hippocampal lesions showed a trend towards higher come back errors p = 0.08). Normal controls could maintain their accuracy over five consecutive trials. Patients, beginning with less accuracy, showed significant improvement after each trial (p<0.001). The findings suggest that unilateral HAS impair the immediate recall of idiothetic spatial information, but does not affect long-term spatial learning.

Cortical responses to object-motion and visually-induced self-motion perception

We investigated the spatiotemporal cortical dynamics during the perception of object-motion and visually-induced self-motion perception in six normal subjects, using a 143-channel neuromagnetometer. Object-motion specific tasks evoked early transient activity over the right temporooccipital cortex, while self-motion perception, or vection, additionally was followed by sustained bilateral activity in the temporoparietal area. The specific signal distributions suggest to represent the different perceptual modes of object-motion and self-motion sensation.

Physiological evidence of gender differences in word recognition: a magnetoencephalographic (MEG) study

Magnetic field recordings were made in order to describe brain processes during a word recognition experiment. We investigated 26 healthy young subjects (14 females) and focused on gender differences related to recognition performance and brain activity. From about 200 ms to 350 ms after word onset the event-related field (ERF) patterns differed significantly between women and men, although the mean recognition performances did not. Differences were due to different strengths of activation as well as due to the involvement of different neural structures as underlined with statistical analysis. We interpret that our physiological findings demonstrate that different mental strategies are used for correct word recognition in the brains of women and men as assessed with magnetoencephalography (MEG). Our data might be linked to previous findings about the hemispheric asymmetry in male subjects (left lateralized) compared to women in whom both hemispheres seem to be equally involved in word processing.

Finger Somatotopy in Human Motor Cortex

Although qualitative reports about somatotopic representation of fingers in the human motor cortex exist, up to now no study could provide clear statistical evidence. The goal of the present study was to reinvestigate finger motor somatotopy by means of a thorough investigation of standardized movements of the index and little finger of the right hand. Using high resolution fMRI at 3 Tesla, blood oxygenation level-dependent (BOLD) responses in a group of 26 subjects were repeatedly measured to achieve reliable statistical results. The center of mass of all activated voxels within the primary motor cortex was calculated for each finger and each run. Results of all runs were averaged to yield an individual index and little finger representation for each subject. The mean center of mass localizations for all subjects were then submitted to a paired t test. Results show a highly significant though small scale somatotopy of fingerspecific activation patterns in the order indicated by Penfields motor homunculus. In addition, considerable overlap of finger specific BOLD responses was found. Comparing various methods of analysis, the mean center of mass distance for the two fingers was 2--3 mm with overlapping voxels included and 4--5 mm with overlapping voxels excluded. Our data may be best understood in the context of the work of Schieber (1999) who recently described overlapping somatotopic gradients in lesion studies with humans.

False recognition depends on depth of prior word processing: a magnetoencephalographic (MEG) study

Brain activity was measured with a whole head magnetoencephalograph (MEG) during the test phases of word recognition experiments. Healthy young subjects had to discriminate between previously presented and new words. During prior study phases two different levels of word processing were provided according to two different kinds of instructions (shallow and deep encoding). Event-related fields (ERFs) associated with falsely recognized words (false alarms) were found to depend on the depth of processing during the prior study phase. False alarms elicited higher brain activity (as reflected by dipole strength) in case of prior deep encoding as compared to shallow encoding between 300 and 500 ms after stimulus onset at temporal brain areas. Between 500 and 700 ms we found evidence for differences in the involvement of neural structures related to both conditions of false alarms. Furthermore, the number of false alarms was found to depend on depth of processing. Shallow encoding led to a higher number of false alarms than deep encoding. All data are discussed as strong support for the ideas that a certain level of word processing is performed by a distinct set of neural systems and that the same neural systems which encode information are reactivated during the retrieval.

Left temporal and temporoparietal brain activity depends on depth of word encoding: a magnetoencephalographic study in healthy young subjects

Using a 143-channel whole-head magnetoencephalograph (MEG) we recorded the temporal changes of brain activity from 26 healthy young subjects (14 females) related to shallow perceptual and deep semantic word encoding. During subsequent recognition tests, the subjects had to recognize the previously encoded words which were interspersed with new words. The resulting mean memory performances across all subjects clearly mirrored the different levels of encoding. The grand averaged event-related fields (ERFs) associated with perceptual and semantic word encoding differed significantly between 200 and 550 ms after stimulus onset mainly over left superior temporal and left superior parietal sensors. Semantic encoding elicited higher brain activity than perceptual encoding. Source localization procedures revealed that neural populations of the left temporal and temporoparietal brain areas showed different activity strengths across the whole group of subjects depending on depth of word encoding. We suggest that the higher brain activity associated with deep encoding as compared to shallow encoding was due to the involvement of more neural systems during the processing of visually presented words. Deep encoding required more energy than shallow encoding but for all that led to a better memory performance.

Electrophysiological, neuropsychological and clinical findings in multiple sclerosis patients receiving interferon beta-1b: a 1-year follow-up

We assessed serial event-related potentials (ERPs) as well as neuropsychological and clinical test findings in a group of multiple sclerosis (MS) patients (n = 14) treated with interferon beta-1b (INF-beta-1b) compared to normal controls (n = 14). All investigations were done within 1 week before INF-beta-1b therapy was started and 12 months later. An auditory oddball paradigm was employed. No significant differences in the N100, P200, N200 or P300 latencies between patients and control group were found, but 3 out of 14 MS patients developed abnormal P300 latencies (more than 2 standard errors from the mean) after 1 year of INF-beta-1b therapy. This was not reflected by the respective neurological impairment as assessed by the Expanded Disability Status Scale score. ERPs might be a useful tool in clinical studies in order to evaluate drug effects on cognition, but for a final statement, the analysis of ERPs in a larger group of patients is required.