Distribution of scalp somatosensory potentials evoked by stimulation of the tibial nerve in man

The scalp distribution of the response to stimulation of the tibial nerve at the medial malleolus was systematically analysed. The somatosensory evoked potential (SEP) was recorded with electrodes placed in a transversal line over the ipsilateral and contralateral postcentral gyri and in a sagittal line over the longitudinal brain fissure. The SEPs recorded over the ipsilateral hemisphere and along the sagittal line were similar to the F response (the response over the foot primary somatosensory region). Over the contralateral hemisphere the waveform of the responses changed obviously from point F to the point C (contralateral hand primary somatosensory region). The C response started with N37, P40 had a longer latency, N50 was not present and the subsequent waves were also considerably different. Mathematical simulation of the responses recorded from the electrodes between points F and C has shown that they represent an electrical algebraic summation of the activity over points F and C. Although the F and C responses may be 2 potentials arising from the opposite sides of a single dipole generator which is located in the medial fissure, it is more probable that the somatosensory evoked potential on tibial nerve stimulation reflects the activity of 2 separate generators.     

The electrode,the brain and the mind

Conclusion Finally, the brain does function as an integrated whole in one sense. But there are semi-separable mechanisms within that integration. We must continue to study them. This is the way of progress that was begun for us by Fritsch and Hitzig, and Charcot and Jackson.As scientists, we should reserve judgment as to the ultimate nature of things. Meantime we can only use the language of dualism, and speak thus of the mind and the brain. There is no other medium of analytical discussion. The ancient riddle of how brain and mind do interact is still unsolved. But, we begin to understand the brain, if not the mind. The mind receives messages. It seems to direct brain action in the focussing of attention and in voluntary activity.There is a special mechanism for the mind. It can be activated from a distance by an electrode on the interpretive cortex. The mechanism is sometimes arrested by epileptic discharge in centrally placed gray matter. During this activation, consciousness is not lost. During this arrest, consciousness is lost and since other mechanisms continue without control from the mind's mechanism, the individual becomes an automaton.Fritsch and Hitzig had stumbled upon the truth. The brain does function, as they said, by isolated mechanical means. And we can now perceive the outline of a further truth: The mind is matched by a specific corresponding mechanism in the brain. Human behaviour is determined by interaction of brain and mind.The Fritsch and Hitzig Centennial Lecture, Deutsche Gesellschaft für Neurologie and La Société Neurologique de France, München, October 8, 1970.     

Electrophysiological methods for the identification of thalamic nuclei

Summary To increase the precision of the anatomical localization in stereotaxic neurosurgery, three techniques are now in common use to identify the thalamic nuclei: electrophysiological recording, local stimulation, reversible local blockade. A comparison is made between the results obtained by these three methods.Translated from a paper presented at the Joint Meeting of the German and French Neurological Societies, Munich 1970.     

Expressing qualitative biomedical knowledge exactly using the language LESK

A language (LESK) is described which allows one to make mainly qualitative declarations of the essential terminology and facts in some technical subject. LESK is essentially first order predicate calculus, made to look like natural language. A LESK system, now partially implemented in PROLOG, allows one to enter declarations and assertions, check consistency, and deductively answer predominately generic, universally quantified questions.An extensive example is presented in which LESK is used to describe neurophysiological knowledge about the stretch reflex.     

Quantification of synaptic vesicles in hippocampus of aging rats and initial studies of possible relations to neurophysiology

Synaptic vesicle populations were quantified in Schaffer-commissural synapses which terminate on CA1 pyramidal cell apical dendrites, in aging and young-mature rats. Vesicles were found to be reduced with age, and this effect was most pronounced in the oldest animals (e.g., 28 months) within the aged group. Numerical density of synaptic vesicles in aged rat hippocampus was reduced whether expressed as vesicles per terminal, vesicles per μ² of terminal, or vesicles per μ² of terminal corrected for shrinkage or swelling as assessed by mitochondrial cross-sectional diameters. Counted synaptic terminal areas were not significantly different in the aged animals, although a trend toward reduced terminal size with aging was seen. The latter observation apparently rules out increased terminal swelling in aged rat synapses as a basis for reduced vesicle density. In some rats, neurophysiological studies were concomitantly performed. A significant correlation was found between the amplitude of the monosynaptic population spike after 20 min of 4 Hz stimulation of the Schaffer-commissural fibers and synaptic vesicle populations in terminals of these stimulated pathways. However, because of a low n this result must be viewed as preliminary.     

Activation of mossy and climbing fiber pathways to the cerebellar cortex by stimulation of the fornix in the rat

Summary The fornix of the rat was electrically stimulated with bipolar concentric electrodes to determine the properties of single unit responses in Purkinje cells of the cerebellar cortex. Both climbing (CF) and mossy fiber (MF) pathways were activated by fornix stimulation. MF responses were indicated by single or double spike responses appearing at latencies of 5–10 ms. The MF spike responses, as quantified by histogram analysis, were further identified by appearance of graded responses with increasing stimulus strength and by following at frequencies up to and greater than 20/s. CF responses were identified by characteristic complex all-or-none burst responses with latencies usually between 10 and 20 ms and with following frequencies at no faster than 10/s. Experiments which involved movement of the stimulating electrode and production of lesions around it established that the activated fiber system was within the dorsal fornix and not in adjacent areas. The results indicate that hippocampal and other limbic areas can influence the cerebellar cortex by direct mossy and climbing fiber pathways, as has been demonstrated for other afferents. It is further suggested that motor patterns linked to hippocampal activity may be regulated by this system.This work was supported by N.S.F. Grant No. 77-01174 awarded to Dr. Donald J. Woodward, and an award from the Biological Humanics Foundation     

Quantification of the Tr?mner signs: a sensitive marker for cervical spondylotic myelopathy

The Trömner sign is commonly used as a clinical neurological examination for upper motor neuron lesions above the fifth or sixth cervical segments of the spinal cord. This study aims to assess and quantify the Trömner signs utilizing electrophysiological test, and correlate to the severity of cord compression in cervical spondylotic myelopathy (CSM). We enlisted 46 CSM patients, and 30 healthy persons as controls. Manual Trömner and Hoffmann signs were tested in all subjects. By using a self-designed instrument, we performed electrophysiological assessments for the Trömner signs in patients and controls. Parameters of conduction latencies and amplitude of muscle action potentials were measured and compared with the cord compression ratios in CSM patients. The results showed a greater diagnostic sensitivity for the quantified Trömner signs in comparison to those of manual Trömner signs and Hoffmann signs. We found a positive correlation between the amplitude of muscle action potentials obtained in the Trömner signs and the cord compression ratios in the patients with CSM. In conclusion, the Trömner signs can be measured by electrophysiological assessments. We demonstrate a new quantification method for an established neurological sign. Not only is Trömner sign a highly sensitive test in clinical neurological examination, the electrophysiological assessment of this sign can also serve as an objective marker for evaluation of the severity of cervical cord compression.     

Distinct cognitive neurophysiologic profiles for lamotrigine and topiramate

PURPOSE: To contrast the effects of lamotrigine (LTG) and topiramate (TPM) on cognitive task-related and resting-state EEG and evoked potential (EP) measures. METHODS: We used a double-blind, randomized, crossover design. Healthy adults (N = 29) had two 8-week periods of dose escalation, 4 weeks of drug maintenance (300 mg daily), and 4 weeks of washout. EEG was recorded during working memory (WM) tasks and resting conditions at baseline, at the end of each maintenance phase, and after final washout. RESULTS. LTG did not affect overt performance on the tasks, although it reduced EEG power in both resting and WM task conditions, most prominently in the 6- to 12-Hz frequency range, and attenuated P300 evoked-potential amplitude equally in both WM task loads. TPM slowed responses and increased errors. It also increased EEG power below 6 Hz in all conditions, and reduced the amplitude of a slow wave observed in a difficult version of the WM task. CONCLUSIONS: The drugs produced both task-independent and task-related alterations in neurophysiologic measures. The EEG and EP changes produced by TPM are consistent with an impairment of WM, as evidenced by overt performance deficits on the behavioral tasks. By contrast, the reduction in synchronous cortical activity produced by LTG was not accompanied by cognitive impairment. It is unknown whether such effects would also be observed at lower doses, such as those that often are used in monotherapy for newly diagnosed patients.     

Pain neurophysiology education for the management of individuals with chronic low back pain: systematic review and meta-analysis

Pain neurophysiology education (PNE) is a form of education for patients with chronic low back pain (CLBP). The purpose of this systematic review was to investigate the evidence for PNE in the management of pateints with CLBP. A literature search of MEDLINE, CINAHL and AMED was performed from 1996(01)–2010(09). RCT appraisal and synthesis was assessed using the Cochrane Back Review Group (CBRG) guidelines. The main outcome measures were pain, physical-function, psychological-function, and social-function. Two moderate quality RCTs (n = 122) were included in the final review. According to the CBRG criteria there was very low quality evidence that PNE is beneficial for pain, physical-function, psychological-function, and social-function. Meta-analysis found PNE produced statistically significant but clinically small improvements in short-term pain of 5 mm (0, 10.0 mm) [mean difference (95%CI)] on the 100 mm VAS. This review was limited by the small number of studies (n = 2) that met the inclusion criteria and by the fact that both studies were produced by the same group that published the PNE manual. These factors contributed to the relatively low grading of the evidence. There is a need for more studies investigating PNE by different research groups to support early promising findings. Until then firm clinical recommendations cannot be made.