Automated identification of ERP peaks through Dynamic Time Warping: an application to developmental dyslexia.

OBJECTIVE: This article proposes a method to automatically identify and label event-related potential (ERP) components with high accuracy and precision. METHODS: We present a framework, referred to as peak-picking Dynamic Time Warping (ppDTW), where a priori knowledge about the ERPs under investigation is used to define a reference signal. We developed a combination of peak-picking and Dynamic Time Warping (DTW) that makes the temporal intervals for peak-picking adaptive on the basis of the morphology of the data. We tested the procedure on experimental data recorded from a control group and from children diagnosed with developmental dyslexia. RESULTS: We compared our results with the traditional peak-picking. We demonstrated that our method achieves better performance than peak-picking, with an overall precision, recall and F-score of 93%, 86% and 89%, respectively, versus 93%, 80% and 85% achieved by peak-picking. CONCLUSION: We showed that our hybrid method outperforms peak-picking, when dealing with data involving several peaks of interest. SIGNIFICANCE: The proposed method can reliably identify and label ERP components in challenging event-related recordings, thus assisting the clinician in an objective assessment of amplitudes and latencies of peaks of clinical interest.

Spatiotemporal dynamics of single-letter reading: a combined ERP-FMRI study.

This work investigates the neural correlates of single-letter reading by combining event-related potentials (ERPs) and functional magnetic resonance imaging (fMRI), thus exploiting their complementary spatiotemporal resolutions. Three externally-paced reading tasks were administered with an event-related design: passive observation of letters and symbols and active reading aloud of letters. ERP and fMRI data were separately recorded from 8 healthy adults during the same experimental conditions. Due to the presence of artifacts in the EEG signals, two subjects were discarded from further analysis. Independent Component Analysis was applied to ERPs, after dimensionality reduction by Principal Component Analysis: some independent components were clearly related to specific reading functions and the associated current density distributions in the brain were estimated with Low Resolution Electromagnetic Tomography Analysis method (LORETA). The impulse hemodynamic response function was modeled as a linear combination of linear B-spline functions and fMRI statistical analysis was performed by multiple linear regression. fMRI and LORETA maps were superimposed in order to identify the overlapping activations and the activated regions specifically revealed by each modality. The results showed the existence of neuronal networks functionally specific for letter processing and for explicit verbal-motor articulation, including the temporo-parietal and frontal regions. Overlap between fMRI and LORETA results was observed in the inferior temporal-middle occipital gyrus, suggesting that this area has a crucial and multifunctional role for linguistic and reading processes, likely because its spatial location and strong interconnection with the main visual and auditory sensory systems may have favored its specialization in grapheme-phoneme matching.

The Von Restorff effect in ageing and Alzheimer's disease.

The purpose of the study was to evaluate the Von Restorff effect in normal ageing and in Alzheimer's disease (AD). A shortened paradigm was administered to three groups of subjects: young volunteers, elderly volunteers and patients with early-stage AD (MMSE>20). Each subject was presented with 25 lists of 10 words each, the target word appearing in double font size. A free recall phase followed the presentation of each list; after completion of the battery, a size recognition test was administered and subjects were inquired regarding the strategy employed and perception of target words. The total number of recalled words differed significantly among the three groups (young volunteers 144.4+/-38.6, elderly volunteers 86.5+/-17.6, patients 44.2+/-14.6). A significant difference in percentage of recall was found between target and non-target words in young (60.0+/-13.8% vs. 45.7%+/-15.0%, p<0.001) and in elderly (31.2+/-11.4% vs. 20.2+/-6.9%, p<0.001) volunteers, but not in patients (10.7+/-6.9% vs. 11.8+/-7.3%). The present study highlights that the Von Restorff effect can be detected in healthy elderly subjects, and that it is significantly reduced in patients in the early stage of AD. On the basis of the findings of the present study it is not possible to disentangle the contribution of visual-perceptual and encoding impairment, both of them potentially contributing to the observed reduction.

A pilot study of the reading processes combining reading-related potentials (RRPs) and fMRI.

Aim of this work is to describe temporally and spatially the activation of the cerebral areas involved in reading processes by combining fMRI and reading-related potentials (RRPs). RRPs and fMR images were recorded in separate studies during a specifically designed experimental procedure. The protocol consisted of three visual tasks of increasing complexity. In the first two tasks subjects were asked to passively watch at letters and symbols respectively without making any effort in reading or articulating silently them. In the third task subjects were asked to read aloud letters appearing on a screen at a rate of 0.5 Hz. 7 young healthy subjects participated in the experiment. The analysis of RRPs highlighted the following results. During non-alphabetic symbols presentation the amplitude of the potentials was lower in comparison to presentation of letters. Reading aloud generated RRPs of greater amplitude than implicit reading. The analysis of fMRI scans revealed that the visual presentation of both letters and symbols produced similar activation of primary visual areas. Besides these areas, reading aloud activated the motor and pre-motor cortices and the left anterior temporal lobe. The combined analysis of RRPs and fMRI characterizes both temporally and spatially the development of reading processes.

[Multiple sclerosis and acute disseminated encephalomyelitis in children: a difficult diagnostic differentiation. Report of a young boy with early onset of the disease]. / Sclerosi multipla ed encefalomielite acuta disseminata: una diagnosi differenziale difficile. In merito ad un caso clinico con esordio molto precoce.

We report the case of an eight year old boy who developed suddenly acute left-sided hemiparesis syndrome. Brain magnetic resonance imaging (MRI) showed multiple white matter lesions. Therefore we considered in the differential diagnosis multiple sclerosis (MS) and acute disseminated encephalomyelitis (ADEM). The patient received intravenous immunoglobulin (IVIG), 1 g/kg/d over 2 days with complete regression of clinical symptoms. No relapses occurred within six months, although brain magnetic resonance imaging studies found new white matter lesions, suggesting multiple sclerosis with very early onset.

Analysis of single trial movement-related brain macropotential.

A parametric method of identification of movement-related brain macropotentials on a single trial basis through an ARX (autoregressive with exogenous inputs) algorithm is presented. The basic estimation of the information contained in the single trial is taken from an average carried out on a sufficient number of trials, while the noise sources, EEG and EOG are characterized as exogenous inputs in the model. The simulations as well as the experimental results confirm the capability of the model to drastically improve the signal/noise ratio in each single trial and to satisfactorily identify the contributions of signal and noise in the overall recording. This way, using the same algorithm, a particularly efficient reduction of ocular artifacts is also achieved. The movement-related brain macropotentials recorded in three subjects show a high degree of variability from trial and this effect seems to be related to programming processes and evaluation of errors.

Development of gestalt-reading processes in children: assessment using the Boder test.

According to Boder, there are two processes involved in reading: visual-gestalt and analytic-phonetic. The gestalt process is activated for known words, forming part of the child's "sight vocabulary", and it enables him/her to recognize words even when they are exposed for a very short time. The analytic-phonetic process involves the auditory channel when the words are not part of the "sight vocabulary" and require a spelling process. At first, neither the English version nor the Italian adaptation of the Boder test included a control of word exposition time (ET) and reading time (RT). Both parameters are necessary for a check of the gestalt and phonetic processes. The aim of this paper was the assessment of minimum ET for the words belonging to the "sight vocabulary" and of RT for a word read through a gestalt process. Seventy-five primary schoolchildren from the first to the fifth class were presented with 100 meaningful words (MF) and 100 meaningless (ML) words, using ETs ranging from 150 to 650 ms. The results showed that, at the age of 7 years, the gestalt process was completely developed. Of MF words, 95% were correctly read and it did not change significantly with longer ETs. The RT for MF words did not change with different ETs and remained stable after the age of 7 years. Finally, the RT for ML words was always longer than the RT for MF words, and the difference was significant in 8-, 9- and 10-year-old children.

Movement-related brain macropotentials of persons with Down syndrome during skilled performance.

Motor performances and movement-related brain macropotentials of nine 23-year-old males with Down syndrome whose mean MA was 10.2 years were compared to those of two control groups whose members were matched to the experimental subjects on CA or MA. A self-paced, voluntary, goal-directed task, which consisted of calculating a time interval of 40 to 60 msec by pressing two buttons, was employed. Subjects with Down syndrome had great difficulty in organizing and timing a correct temporal sequence of ballistic movements. They were much slower, less accurate, and achieved a smaller number of target performances. These behavioral patterns were associated with movement-related brain macropotentials altered in amplitude and latency. The potentials related to programming movements and processing reafferent sensory information were absent, and those involved in the evaluation of the outcome of the performance were reduced.

Developmental course of brain-stem auditory evoked potentials in the first days of full term infants.

Modifications of brain-stem acoustic evoked potentials (BAEPs) in the first 5 days of life of normal full-term infants are reported. BAEPs were recorded using rarefaction clicks at 70, 60, 40, 20 dB HL. Multiple linear regression analysis was performed to evaluate chronological and gestational age differences for all positive and negative peaks, interpeak latencies, amplitudes and amplitude ratios. The percentage of newborn infants with auditory threshold of 20 dB HL increased with the number of days. At all intensities the latency of PIII and PV decreased significantly between the 2nd and 3rd day, while the latency of PI decreased significantly between the 3rd and the 4th day; PIII and PV latencies decreased also between the 4th and the 5th day. The longer the period of gestation the longer was the PI latency recorded between the 2nd and 5th day after birth. The anatomical and physiological changes developing shortly after birth are probably responsible for the above findings. These changes most probably appear firstly in the cochlear and trapezoid nuclei and later on in the organ of Corti.

A critical review of physiological and clinical aspects of movement related brain macropotentials in humans.

The methodological, developmental and clinical aspects of movement related brain macropotentials (MRBMs) are reviewed. The physiological differences between unskilled and skilled movements are described and the importance of interactive paradigms in studying movement organization from childhood to adulthood is emphasized. The developmental characteristics of the MRBMs in 119 normal males using a skilled motor perceptual task are presented together with a few clinical applications. This test has been performed by children with learning disabilities, boys with Down syndrome, subjects with chronic schizophrenia and patients with Parkinson syndrome. The results of the MRBMs are discussed for their relevance for our understanding of the cognitive processes and for their therapeutic implications.

Brain activity associated with skilled finger movements: multichannel magnetic recordings.

We recorded with a 24-channel SQUID magnetometer cerebral activity preceding and following self-paced voluntary 'skilled' movements in four healthy adults. The subject pressed buttons successively with the right index and middle fingers aiming at a time difference of 40-60 ms; on-line feedback on performance was given after each movement. Slow magnetic readiness fields (RFs) preceded the movements by 0.5 s and culminated about 20 ms after the electromyogram (EMG) onset. Movement-evoked fields, MEFs, opposite in polarity to RFs, were observed 90-120 ms after the EMG onset. They were followed by an additional 'skilled-performance field', SPF, 400-500 ms after the EMG onset. The source locations of RF, MEF, and SPF were within 2 cm from sources of the somatosensory evoked responses, which were situated in the posterior wall of the Rolandic fissure; the sources of MEF were closest to the midline. Neural generators of these deflections and of the corresponding electric potentials are discussed.

Goal or near miss! Movement potential differences between adults and children in skilled performance.

In this study, the performances and the movement-related brain macropotentials of a group of adults and 10-year-old children were analyzed to test whether and how they were correlated to the success or failure in the performance. Bereitschaftspotential (BP), motor cortex potential (MCP) and skilled performance positivity (SPP) related to preparation, execution and evaluation of performance respectively showed a significant relationship to the performance outcome. The BP area in the left precentral decreased significantly with increasing performance time. The amplitude of the MCP was maximum during target performances and decreased with increasing range of error of performance. There was a difference in trend between adults and children in the SPP latency. During target performances, SPP latency in Pz was maximum in children and minimum in adults. In children, the SPP amplitude was greater in frontal and precentral areas during target performance and decreased with increasing inaccuracy of performance. This trend was not evident in adults. The results seem to indicate that the SPP latency does not seem to depend on the performance time but on the evaluation of information conveyed by the stimulus. How this evaluation takes place seems to be different in children and adults; this evaluation process is also reflected in the SPP amplitude of children during target performances. For the adults who have already developed formal thinking, the probability that any outcome is possible exists and so the significant relationship between SPP amplitude and performance is not seen.

Motor-perceptual function in children with developmental reading disorders: neuropsychophysiological analysis.

The aim of this paper is to compare the motor performances and the movement-related macropotentials of 8 male children aged 10 years with developmental reading disorders with those of 9 nondisabled male children of the same age. The task employed consisted of initiating the sweep of an oscilloscope with a self-paced movement and terminating it within 50 +/- 10 msec. The children with reading disorders were slower, less accurate, and achieved a smaller number of target performances. Their brain macropotentials associated with motor programming, processing of sensory information, and evaluation of the results were altered in amplitude and latency. In the children with reading disorders, the systems involved in planning strategies and processing of sensory information are inadequate and those involved in the correction of errors are less efficient. Therefore, reading disorders could express defective integration and dysfunction of numerous processes occurring at different levels and times.

The acute and chronic administrations of piracetam affect the movement-related brain macropotentials.

Neurophysiological and neurochemical studies have demonstrated that piracetam improves learning and memory both in animals and humans. In recent years it has been shown that when a subject is engaged in a motor perceptual task, some psychomotor functions are correlated with a consistent pattern of brain electrical activity. Given the relationship between the movement-related brain macropotentials (MRBMs) and the cognitive processes associated with them, we considered the MRBMs particularly suitable for the neurophysiological assessment of the efficacy of piracetam in man. The aim of this study was to test the acute and chronic effect of piracetam administration on the MRBMs in normal children during the performance of a motor perceptual task. The design was a triple-blind study, during which the subjects took either placebo or piracetam in random sequence, with a washout period of 3 weeks. The dose was 170 mg/kg for the acute treatment and 140 mg/kg/day for chronic treatment. No side-effects were reported by the children during or after acute or chronic treatment with piracetam. There was no statistically significant difference between placebo or piracetam treatment with regard to 'performance', which was already optimal at baseline, and to electromyographic activity. On the contrary, the MRBMs were significantly modified by treatment. In particular the Bereitschaftspotential was present as a positive shift during acute treatment with piracetam and increased after chronic treatment. Skilled performance positivity (SPP) amplitudes were significantly increased and SPP latency reduced by chronic treatment with piracetam. piracetam appears to act on the catecholaminergic and cholinergic systems via an increase of the inhibitory hyperpolarizing processes.

The skilled performance positivity after learning a skilled task.

The effect of an intensive training period and that of a time-distributed training on skilled performance positivity (SPP) have been studied. SPP is a potential associated with knowledge and evaluation of the results of a goal-directed bimanual self-paced task requiring particular ability. Nine subjects with average intelligence but with some difficulties in the motor-perceptive sphere were studied. The task consisted of initiating the sweep of an oscilloscope with a self-paced movement and terminating it within 50 msec +/- 10 msec. The subjects had to repeat this task several times at various time intervals. The electrical activity was recorded from Fpz, Fz, Cz, Pz, P4, P3 and the right/left precentral areas. For each performance, performance time, performance shift taken as the accuracy index, as well as the percentage of target performances were evaluated. Motor performances improved with both distributed and intensive practice. Only distributed practice had a significant effect on SPP latency and amplitude. SPP latency decreased in all brain areas, whereas amplitude increased in the prefrontal, frontal and left precentral areas. These results seem to suggest that the performance evaluation processes take place more quickly and efficiently through distributed practice.

Pathophysiology of the immune system in elderly subjects with or without diabetes and variations after recombinant interleukin-2.

This study reports two groups of elderly diabetic patients and normal subjects, with or without hypercholesterolemia and hypertriglyceridemia, who presented a decrease of the T lymphocyte-mediated function, proliferative capacity, phagocytosis, cytotoxicity and surface markers. This fall was more evident in hypercholesterolemic and hypertriglyceridemic subjects. The humoral responses and other parameters studied did not reveal significant variations. The authors also observed that recombinant interleukin-2 (rIL-2) stimulation determined a satisfactory response in healthy and diabetic subjects, while it did not normalize values in patients with altered lipid balance.

Sex and ear differences of brain-stem acoustic evoked potentials in a sample of normal full-term newborns. Normative study.

The present paper reports a normative study of the BAEPs recorded from 80 normal full-term newborns by using a rarefaction click at 70, 60, 40, 20 dB HL. Positive, negative peaks and the relative amplitudes were measured. Means, standard deviations and 95% and 99% confidence limits were calculated for each component, for positive and negative IPLs and amplitude ratios. A normality test distribution showed that each component had normal distribution except for wave PIII at 70 dB and at 60 dB HL because of its index of kurtosis and for IPLs PII-PIII and NII-NIII at 70 and 60 dB HL. MLRA was performed and significant statistical differences were found for sex, ears and intensities. Females had the latencies of waves PIII, PIV, PV, NII and NIV shorter than males. The BAEPs obtained from the left ear had shorter latencies for positive and negative peaks. Latencies, amplitude and morphology of the BAEPs vary with variations of the intensity. The IPLs PII-PV, PIII-PV and PIV-PV were not affected by changes of intensity.