The early negative potential evoked by stimulation of the tibial nerve in man

The scalp response to stimulation of the tibial nerve at the level of the medial malleolus was systematically analysed. It was recorded 2 cm posterior to the vertex and at the sites corresponding to cortical representation of the hand. The existence of an early negative wave with a peak latency of 37.2 ± 2.29 ms and amplitude of ?0.69 ± 0.40 μV was established (being half the amplitude of the first positive wave (P40) over the vertex). This wave was named N37 in respect of the peak latency and polarity. N37 was the first event recorded after stimulation of the tibial nerve at this level as the onset latency was 32.2 ± 1.75 ms and that of P40 over the vertex 33.8 ± 2.28 ms. It was recorded with the highest amplitude over the hand primary somatosensory area after stimulation of the opposite foot.N37 evoked by stimulation of the tibial nerve at the ankle and N20 evoked by stimulation of the arm nerve are both the primary negativities of the evoked potential. However, N37 is not recorded with maximum amplitude over the leg primary somatosensory area and it is rounded and longer lasting than N20. In spite of these differences the two initial negative electrical phenomena are not necessarily generated by different functional structures. The possible generators of N37 are discussed.     

Adaptation-induced alteration of the relation between response amplitude and contrast in cat striate cortical neurones

The activity of neurones in cat striate cortex in response to laterally moving sinusoidal gratings has been examined. The effect of prolonged visual stimulation with a high contrast moving grating stimulus of optimal orientation and spatial frequency was investigated in terms of the changes wrought in the relationship between response amplitude and stimulus contrast. The adaptation which resulted was characterized by an elevation of contrast threshold by about 0.4 log units and a reduction in the steepness of the relation between response and contrast by about 0.36 log units. Both simple and complex cells exhibited this behaviour. The similarity of these values to the size of contrast threshold elevations demonstrated psychophysically suggests a possible physiological basis for the perceptual phenomenon.     

Differential role of granule cells in the specification of synapses between climbing fibers and cerebellar Purkinje cells in the rat

The effect of X-irradiation of the cerebellum during postnatal development on the establishment of olivo-cerebellar connections was investigated in the rat. Treatment with 950 R during the first week led to a persistance in the adult of multiple innervation of Purkinje cells (PC) by climbing fibers (CF). On the contrary, the same dose given during the second week was uneffective to prevent the establishment of the one-to-one relationship between CF and PC. These findings suggest that the regression of the multiple innervation mainly depends on early formed granule cells.     

Lack of correlation between spontaneous fasciculations and double discharges of voluntarily activated motor units.

We have studied the possible correlation between spontaneous fasciculations and double discharges or voluntarily activated motor units in myelopathies and other proximal neuropathies. Though both these phenomena are common in these diseases, they seem to have no correlation in individual muscles. It is concluded that spontaneous fasciculations and doubling of voluntarily activated motor unit potentials have different sites of origin or different mechanism. For example, if doubling reflects a disturbance of firing in the axon hillock, spontaneous fasciculations may originate in a more peripheral part of the motor axon.     

Cortical unit responses to chemical stimulation of the oral cavity in the rat

The gustatory sensitivity of individual cortical neurons in the rat was examined using a wide range of chemical stimuli. Several subsets of cortical taste cells were identified based on similarities in their response profiles. Although adjacent cortical neurons can differ in their responsiveness to individual tastants, some overlap in taste sensitivities is usually observed.     

A micro-electrode study of peripheral neuropathy in man. Part 2. Responses to conditioning stimuli.

Surface, needle and micro-electrode recordings were obtained from sensory nerves of patients with various types of peripheral neuropathy. Changes in amplitude and conduction velocity of nerve action potentials were measured after a single conditioning stimulus and after tetanic stimulation for 2 min. In patients with hereditary forms of axonal degeneration (AD), recovery processes of nerve fibres of all conduction velocities were normal; in acquired forms of AD fibres with conduction velocity less than 30 m/sec had greater and more prolonged post-tetanic depression than control nerves of similar conduction velocity. Where neuropathy was associated with segmental demyelination (SD), fibres of all conduction velocities had prolonged recovery processes after both single and tetanic stimulation. The changes were especially marked at higher skin temperature, and were greater than the changes seen in nerves with acquired forms of AD. Finally, 2 sural nerves were studied during the process of Wallerian degeneration after a biopsy had been obtained proximally, and recovery processes did not change during the period of degeneration. Perceptual abnormalities were similar in AD and SD. It is suggested that changes in recovery processes of nerve fibres with segmental demyelination or regeneration after injury contribute to the perceptual abnormalities which occur in clinically encountered peripheral neuropathies.     

A neurophysiological model for anomalous correspondence based on mechanisms of sensory fusion

Normal retinal correspondence is not stable. The arguments for the plasticity of correspondence in normal binocular vision have been given in two previous papers (Nelson, 1975, 1977). In this paper, both laboratory research and the clinical strabismus literature are reviewed to show similarities between normal and abnormal binocular vision. In particular, it is argued that sensory fusion (Panum's areas) and anomalous retinal correspondence (AC) obey similar principles, and so a sensory fusional model of AC may be developed.Recent advances in the neurophysiology of binocular vision are reviewed, but current laboratory knowledge cannot account for many phenomena known clinically unless certain postulates are made. Two hypothesized intracortical interactions among binocular disparity detectors, termed disparity domain inhibition and spatial domain facilitation, play key roles in extending the neurophysiology of binocular vision to an account of both normally - and clinically - observed plasticities of correspondence.The fusional model of retinal correspondence developed here from postulated domain interactions contrasts with the older concept of fixed corresponding points, an approach which has failed to provide a unified foundation for the treatment of normal and abnormal binocular vision.     

The brain commission of the international association of academies: the first international society of neurosciences

International associations of scientists, set up to organize cooperative scientific investigations in an international scope and to lay down global binding standards of research, are of great and still growing importance for the advancement of science. This was also recognized at the beginning of the 20th century by the community of researchers in basic and clinical neurological sciences, who created their first international organization following the trend initiated by scholars in astronomy and geophysics. Thus, the so-called "Brain Commission" of the International Association of Academies was founded in 1903 and was active until the outbreak of the First World War. The Brain Commission had no successor for nearly half a century, until the "International Brain Research Organization" (IBRO) was founded in 1961. Although the Brain Commission could exert an impact on neurosciences only for one decade, this international scientific association inspired and promoted the foundation of a series of Brain Research Institutes, which in part still exist in Europe, and long-lasting innovations in the neurosciences.     

Triple stimulation technique findings in vascular Parkinsonism and Parkinson’s disease

ObjectiveOne of the predominant clinical features that differentiates vascular Parkinsonism (VP) from Parkinson’s disease (PD) is the pyramidal sign. The triple stimulation technique (TST) is one of the most sensitive methods for comparing upper motor neuron involvement in patients with VP and PD. This study aimed to evaluate the usefulness of the TST as a diagnostic tool for VP.MethodsThirteen VP patients, 18 PD patients and 10 age-matched healthy controls were enrolled in this study. We obtained basic participant demographic information and transcranial magnetic stimulation (TMS) parameters, including the TST amplitude ratio, from all participants. We compared the TMS parameters among the VP, PD and control groups.ResultsThe TST amplitude ratio was significantly lower in the VP group than in the PD and control groups (71.59 ± 11.86 vs. 96.42 ± 5.11 and 97.70 ± 3.82, respectively; p < 0.01). The TST amplitude ratio was positively correlated with scores obtained on the United Parkinson’s Disease Rating Scale-III, which reflects motor function.ConclusionsThe TST is an effective and easy technique that offers improved diagnostic sensitivity in patients with VP by assessing upper motor neuron involvement. The TST may also represent a useful monitoring tool for evaluating disease progression.SignificanceThis study is the first to assess pyramidal involvement in patients with VP using the collision technique.