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PubMed2005

Nonlinear multivariate analysis of neurophysiological signals.

Multivariate time series analysis is extensively used in neurophysiology with the aim of studying the relationship between simultaneously recorded signals. Recently, advances on information theory and nonlinear dynamical systems theory have allowed the study of various types of synchronization from time series. In this work, we first describe the multivariate linear methods most commonly used in neurophysiology and show that they can be extended to assess the existence of nonlinear interdependence between signals. We then review the concepts of entropy and mutual information followed by a detailed description of nonlinear methods based on the concepts of phase synchronization, generalized synchronization and event synchronization. In all cases, we show how to apply these methods to study different kinds of neurophysiological data. Finally, we illustrate the use of multivariate surrogate data test for the assessment of the strength (strong or weak) and the type (linear or nonlinear) of interdependence between neurophysiological signals.

Action Potentials↗
PubMed1997

Neurophysiological assessment of brain function and maturation: I. A measure of brain adaptation in high risk infants.

Neurophysiologic assessments using EEG/polysomnographic studies permit the clinician to recognize expected patterns of brain maturation in the healthy neonate. By comparison, one can detect encephalopathic behaviors of newborns who are medically at risk. Severe physiologic expressions of encephalopathy are associated with neuropathologic lesions on postmortem examinations, brain lesions documented on neuroimaging studies, and major neurodevelopmental sequelae of survivors. However, such patterns are observed for only a minority of high risk neonates; less severe encephalopathies occur more frequently in neonates without evidence of brain lesions on imaging studies who either recover from medical illness or who manifest no findings of neurological dysfunction. These subtle and persistent brain disorders are obviously more difficult to detect and grade. This is specifically relevant for preterm infants in whom various degrees of encephalopathy may exist, but whose physiologic behaviors must be distinguished form expected behavioral and neurophysiologic patterns of prematurity. Neonates may express brain dysfunction as altered rates of brain maturation, as compared with expected patterns for a given conceptional age. Neurophysiologic expressions of brain dysmaturity, either from prenatal and/or postnatal stresses, may actually occur in a substantially larger segment of the high risk neonatal population than has been anticipated. EEG-sleep studies can serve as a noninvasive neurophysiologic probe of brain organization and maturation to extend clinical observations to assess the severity and persistence of brain dysfunction in a neonate who may be at risk for later neurodevelopmental compromise.

Adaptation, Physiological↗
PubMed2003

Unraveling the barriers to reconceptualization of the problem in chronic pain: the actual and perceived ability of patients and health professionals to understand the neurophysiology.

To identify why reconceptualization of the problem is difficult in chronic pain, this study aimed to evaluate whether (1) health professionals and patients can understand currently accurate information about the neurophysiology of pain and (2) health professionals accurately estimate the ability of patients to understand the neurophysiology of pain. Knowledge tests were completed by 276 patients with chronic pain and 288 professionals either before (untrained) or after (trained) education about the neurophysiology of pain. Professionals estimated typical patient performance on the test. Untrained participants performed poorly (mean +/- standard deviation, 55% +/- 19% and 29% +/- 12% for professionals and patients, respectively), compared to their trained counterparts (78% +/- 21% and 61% +/- 19%, respectively). The estimated patient score (46% +/- 18%) was less than the actual patient score (P <.005). The results suggest that professionals and patients can understand the neurophysiology of pain but professionals underestimate patients' ability to understand. The implications are that (1) a poor knowledge of currently accurate information about pain and (2) the underestimation of patients' ability to understand currently accurate information about pain represent barriers to reconceptualization of the problem in chronic pain within the clinical and lay arenas.

Adult↗
PubMed1998

Descartes' visit to the town library, or how Augustinian is Descartes' neurophysiology?

Rene Descartes was early accused of taking his central philosophical proposition from St Augustine. Did he also take his central neurophysiological concept from the same source? This is the question which this paper sets out to answer. It is concluded that the foundational neurophysiology propounded in L'Homme does indeed show strong and interesting resemblences to Augustine's largely Erasistratean version. Descartes, however, working within the new paradigm of seventeenth-century physical science, introduced a new principle: whereas Augustine's neurophysiology is pervaded throughout by a vital factor, the pneuma, Descartes' theory involved only inanimate material forces. It is concluded, further, that in spite of the interesting similarities between Augustinian and Cartesian neurophysiology there is no evidence for any direct plagiarism. It seems more likely that Augustine's influence was filtered through the Galenical physiologists of Descartes' own time and of the preceding century.

Europe↗
PubMedDate not supplied

Neurophysiological methods for the assessment of spasticity: the Hoffmann reflex, the tendon reflex, and the stretch reflex.

PURPOSE: To review the literature concerning neurophysiological methods to assess spasticity with respect to mechanisms and methodology, and to describe the three most commonly used methods: the Hoffmann reflex (H-reflex), the Tendon reflex (T-reflex), and the Stretch Reflex (SR). METHOD: A systematic internet database search was performed to identify neurophysiological measurement methods of spasticity. A systematic exclusion procedure resulted in 185 included references, completed by additional informal search. For this paper, information about the H-, T- and stretch reflexes was extracted from these references. RESULTS: Although the reflexes are basically monosynaptic, there are many supraspinal pathways which modulate the responses in terms of their amplitude and latency. As a consequence the methods are sensitive to a considerable number of experimental conditions and are characterized by a moderate reliability and sensitivity. Correlations with other (i.e. biomechanical, neurophysiological or clinical) spasticity assessment parameters are moderate to poor. Standardised and broadly accepted protocols are still largely lacking preventing an effective exchange of knowledge. CONCLUSIONS: The clinical and experimental use of the three methods is restricted due to moderate reliability and sensitivity. It is recommended to perform combined neurophysiological-biomechanical assessment of spasticity during active, functional movement.

Electromyography↗
PubMed2005

Microelectrode investigations of the visual system at the Department Of Clinical Neurophysiology, Freiburg i.Br.: a historical account of the first 10 years, 1951-1960.

The history of the first ten years of neurophysiological science (1951-1960) at the Department of Clinical Neurophysiology in Freiburg i.Br. (Germany) is described by some of the participants. We describe the concepts of Richard Jung for the development of an experimental neurophysiology, the technical conditions which helped to realize these ideas, and the integration of the newly emerging German neurophysiological science into the international community, through the large number of foreign visitors. A short account is given of the young scientists working at the Freiburg laboratory during this period, their main lines of research, as well as the results of their studies.

Germany↗
PubMed2005

Neurophysiological measures in amyotrophic lateral sclerosis: markers of progression in clinical trials.

In this review we evaluate clinical neurophysiological methods, originally described for use in diagnosis that can be applied to measurement of change during the progress of amyotrophic lateral sclerosis (ALS). Such measurements are potentially important in clinical trials, and also in clinical practice. We have assessed methods for lower and upper motor neuron function, including conventional EMG, nerve conduction and F-wave studies, the derived Neurophysiological Index, motor unit counting methods (MUNE), and transcranial magnetic motor cortex stimulation. We have also addressed the validity of measurements of electromechanical coupling. Methods for measuring muscle strength are beyond the scope of this review. We conclude that MUNE, M-wave amplitude and the Neurophysiological Index are sufficiently reliable, sensitive, and relevant to the clinical problem of ALS, to be used in clinical trials in the disease. Transcranial magnetic stimulation is of limited value, but a combination of the measurements made as part of this technique may also be useful. We conclude that clinical neurophysiological techniques should now be used in measuring change in clinical trials in ALS.

Amyotrophic Lateral Sclerosis↗
PubMed2006

Neurophysiological techniques to assess pain in animals.

Neurophysiological techniques are widely applied to animals, both in the search as a monitor for adequacy of anaesthesia, and studies to assess the efficacy of analgesic agents. Laboratory animals have been extensively used in models to investigate pain in man. However a substantial number of studies have also used neurophysiological techniques to increase knowledge of pain in specific animal species, with the aim of improving animal welfare. This review provides an overview of neurophysiological techniques involving the brain that have been used in the assessment of pain in animals. An explanation of the methodology of EEG recording, with particular emphasis on veterinary studies, is given. Neurophysiological models developed to assess pain in different species are described, and their relevance to advancements in animal welfare or best clinical practice indicated.

Animal Welfare↗
PubMed1999

[Clinical neurophysiology and functional neuroimaging at the Société Française de Neurologie (1948-1998)].

The historical role of the French Neurology in the development of anatomo-clinical method is likely to explain why the first communications on electrophysiology were presented in Paris with some delay, as compared with other european societies where the neurophysiological tradition had been more lively. Though clinical neurophysiology, by essence, addresses the pathophysiology of neurological disorders, it has sometimes missed this target at its very beginning, when it aimed at providing data supposed to have some aetiological specificity, causing distrust among neurologists used to accept aetiological diagnosis only when based on post-mortem anatomical evidence. Thanks to the discovery of computerized tomography this time has been over for 25 years, and no one would question anymore the role of clinical neurophysiology and neuroimaging in Neurology, the former giving access to the timing of sensori-motor and cognitive pocesses and the latter to the localization of brain functions. This article reviews the neurophysiological literature published in the Revue Neurologique from 1948 to 1998.

Diagnostic Imaging↗
PubMed2000

Neuropsychological and neurophysiological evaluation after anterior communicating artery (ACoA) aneurysm surgery.

BACKGROUND: We evaluated high cerebral functions 6 months after surgery for bleeding ACoA aneurysms comparing neurophysiological and neuropsycological tests. METHODS: Twelve patients were chosen among a series of cases operated on in the first 48 hours after ACoA aneurysm bleeding. All of them were in Hunt-Hess grade I or II. We excluded patients over 65 years, or with intracranial haematomas, intraventricular haemorrhage, hydrocephalus, or with multiple or giant aneurysms. All of them underwent neurophysiological evaluation with recording and mapping of long latency (P300) auditory and visual event-related potentials (ERPs) and a neuropsychological assessment for memory, intelligence, frontal lobe functions and language. RESULTS: Neuropsychological assessment: All patients were severely damaged on phonemic fluency. In a first group (group A: 3 cases) tests were all in a normal range. In a second (group B: 3 cases) the tests showed severe impairment on learning and long term memory. In a third (group C: 6 cases) tests showed memory and "frontal lobe" deficits. Neurophysiological assessment: The whole group of patients showed significant delay in ERPs recordings compared to controls. ERPs of patients in group A and B showed no significant differences from controls, while being significantly delayed in 5 patients out of 6 of group C. CONCLUSIONS: All patients had difficulties in the phonemic task in which a notable cognitive effort is necessary, while intelligence, short term memory, attention and language were within normal limits. Patients in group C showed severe frontal lobe type cognitive impairment. Those ones in groups A and B did not present cognitive derangements (A) or only memory and learning impairment (B). ERPs may be an objective parameter in the follow-up of cases with cognitive impairment, even if neurophysiological tests cannot be replaced.

Event-Related Potentials, P300↗
PubMedDate not supplied

The complementary role of different neurophysiological methods to demonstrate organicity in male with premature ejaculation and erectile dysfunction.

Erectile dysfunction and premature ejaculation are the most common male sexual disorders. Generally, it is considered that erectile dysfunction is related to organic factors whilst premature ejaculation is related to psychological factors. A detailed history along with physical examination such as using penile doppler, penile tumesans and ultrasonography are insufficient for differential diagnosis in 15-20% of cases. Therefore the role of neurophysiological techniques are important. In this study urological and biochemical investigations were used in conjunction with other neurophysiological methods. According to our results, using a neurophysiological test study on its own was ineffective. As a conclusion our study has shown that neurophysiological methods are important differential diagnosis of revealing suspicious organicity--generally believed to be due to psychological factors- in male sexual disorders.

Adult↗
PubMed2004

Needs analysis for tele-neurophysiology in the Irish North-Western Health Board.

No clinical neurophysiology (CN) service is currently provided by the North-Western Health Board (NWHB) region in Ireland. Digital technology associated with CN is compatible with tele-neurophysiology service development and may increase the efficiency of patient care in remote areas. This study was conducted to assess the need for CN in the NWHB with a view to implementing a tele-neurophysiology service for the region. A retrospective audit of investigations performed at six CN departments in Dublin compared patient groups from regions with (Eastern Regional Health Authority--ERHA) and without (NWHB) local CN departments. 4954 records were audited. CN activity was lower than internationally expected (ERHA group 52% of expected, NWHB group 23% of expected). The 2 groups differ in the specialty of referring clinician (p < 0.0001). NWHB patients are more likely to be referred by clinicians outside their region (p < 0.0001) and wait longer for appointment (p < 0.0001). While there is an unmet demand for CN services in Ireland generally, the population of the NWHB is further disadvantaged. Tele-neurophysiology has the potential to provide fairer access to CN services across the country. The data from this study provide a baseline against which the outcome of investment in CN can be monitored and evaluated.

Chi-Square Distribution↗
PubMed1993

The neurophysiological basis of learning: attention and memory implications for SCI nurses.

Understanding the neurophysiological basis of learning enables nurses working with individuals with spinal cord injury to astutely assess potential for learning. This is particularly relevant when head injury or drug effects influence neurological systems relevant to learning. The neuroanatomical and neurophysiological bases of learning are related to attention, memory, concept formation/abstraction, reasoning, and executive systems. Attention and memory are discussed as they relate to learning in this article. This information is incorporated into an expanded assessment (Ciminaro, Calhoun, & Adams, 1977; Gazzaniga 1979; Lezak, 1983: Mesulam, 1985). More in-depth nursing assessment related to cognitive systems necessary for learning enables nurses to identify intact and impaired cognitive systems and to quantify deficits. Astute assessment is fundamental to planning effective teaching and learning strategies for spinal cord injured persons especially when learning deficits exist, e.g., in head injured persons who have sustained a spinal cord injury. Implications for client and family education derive from an understanding of the normal neurophysiological basis of learning and normal and abnormal assessment findings. Learning is dependent on several cognitive systems--attention systems, memory systems, concept formation/abstraction and reasoning systems, and the "executive" system. Attention and memory systems are discussed in this article, the remainder will be discussed in the next issue. The neuroanatomy and neurophysiology, clinical findings associated with normal and abnormal function, and nursing implications for the nurse working with individuals with spinal cord injury will be explored.

Attention↗
PubMed1993

A data interchange standard for clinical neurophysiology.

A Standard Specification for Transferring Digital Neurophysiological Data Between Independent Computer Systems (Designation E 1467-92) has been developed. The specification defines a common representation of all of the data associated with a complete clinical study, including digitized neurophysiological waveforms, textual annotations and interpretive reports. Patterned after existing, related healthcare data interchange standards, it will facilitate data interchange between neurophysiological instruments, computer systems within the neurophysiology laboratory, other information systems in the hospital, and outside healthcare facilities or research laboratories.

Computer Communication Networks↗
PubMed1975

Early neurophysiological assessment after insult to the central nervous system.

Cerebral insult is a generic term which includes many causes of altered cerebral function. Neurophysiological investigations, closely integrated with clinical and metabolic studies, should begin at an early stage after any such insult (namely in the first few hours) to provide information on the type, severity and evolution of latered brain function. The present contribution is based on prospective studies on 200 children with closed head injuries and 500 children who had been resuscitated following cardiocirculatory or respiratory arrest. In addition to electroencephalography, other neurophysiological investigations may be carried out whenever necessary including electroretinography, evoked potential studies and polyelectromyography at the patient's bedside, whether or not in the intensive care situation. The rapid evolution of metabolic events and of both clinical and neurophysiological features characterizes the acute initial phase, in marked contrast to the more static features of long term sequelae to a cerebral insult. Experience over the past 25 yr has shown that no rule is applicable to every case because of the diversity of individual circumstances. However, a well planned early neurophysiological assessment after insult to the central nervous system has given reliable prognostic criteria for the subsequent management of each patient and for the evaluation of any complications during the first few weeks of treatment.

Brain↗
PubMed2002

Neurophysiologic parameters and symptoms in chronic renal failure.

We studied: (1) the sensitivity of various neurophysiologic parameters in the diagnosis of uremic polyneuropathy, (2) the relationship between subjective symptoms and neurophysiologic parameters, and (3) the effect of a single hemodialysis on the neurophysiologic parameters in 21 patients undergoing hemodialysis. The following parameters were studied: sensory and motor nerve conduction, including F-wave parameters; vibration detection thresholds; and thermal thresholds. The clinical findings and subjective symptoms were studied using a standardized questionnaire. The most sensitive parameters in the diagnosis of uremic neuropathy were F-wave parameters from lower limbs, vibration detection thresholds from the feet, and the sural nerve sensory action potential amplitude. The nerves from the upper extremities on the side of the fistula should not be used in the diagnosis of uremic polyneuropathy due to numerous mild local nerve lesions. The positive neuropathic symptoms correlated with quantitative vibratory detection thresholds and sensory nerve conduction studies, especially the amplitude of the sensory nerve action potential in the sural nerve. We found no significant change in any of the neurophysiologic parameters following a single hemodialysis session.

Chronic Disease↗
PubMed1989

Neural mechanisms of swallowing: neurophysiological and neurochemical studies on brain stem neurons in the solitary tract region.

Neurophysiological studies of the nuclei of the tractus solitarius (NTS) and adjacent regions have provided a partial understanding of the integrative brainstem network underlying swallowing and related functions such as respiration. The NTS is also richly endowed with an abundance of neuropeptides and other neuroactive substances, but only limited information is available on their influences on neurons involved specifically in swallowing. Since dysfunction of these neurophysiological and neurochemical regulatory mechanisms in the NTS region may be important in pathophysiological conditions such as dysphagia, increased awareness of and focus on these mechanisms are warranted. This paper outlines recent neurophysiological and neurochemical data that provide information on the afferent inputs and neurophysiological properties of neurons in NTS and adjacent caudal brainstem regions implicated in swallowing, respiration, and respiratory-related reflexes.

Angiotensin II↗
PubMed2006

[Neurophysiological and neuroimaging studies for restless legs syndrome and periodic leg movement disorder].

The restless legs syndrome (RLS) is a clinical diagnosis based on the four essential criteria defined by the International Restless Legs Syndrome Study Group (IRLSSG). An idiopathic form can be separated from a symptomatic form. Neurophysiological studies have investigated the pathophysiology of the idiopathic RLS or have been used to exclude a symptomatic cause, in particular polyneuropathy. So far cortical excitability changes, corticomotor, somatosensory and auditory pathways, spinal cord excitability, B-wave rhythm and cycling alternating pattern, as well as reflex mechanisms have been investigated by electroencephalography, evoked potentials, Bereitschaftspotentials, nerve conduction and thermal threshold measurements, electromyography, transcranial Doppler sonography, measurements of the spinal flexor reflex as well as neuroimaging techniques. The etiology of the RLS cannot be revealed by these methods, neurophysiological studies in RLS are, however, useful for a better understanding of the pathophysiology and for exclusion of a polyneuropathy or other symptomatic causes. In addition to neurophysiological investigations, small fiber neuropathy, which seems to be a more common finding in RLS patients than expected to date, may need biopsy for confirmation. This review will focus on investigations of the different systems involved with diverse neurophysiological methods.

Brain↗