Mapping of somato-sensory evoked potentials (SEP): new findings suggesting the role of brain waves as a "temporal analyzer of the stimulus".

For a number of years we have been reporting a relationship between the mid components of the somato-sensory evoked potentials and basic brain waves. Recently we suggested that when the primary spike occurs it elicits a train consisting of beta, alpha, theta and delta single waves, originating at the same point in time and overlapping one with the other. The half periods of each of these waves are equal to the latencies of mid and late SEP components. Thus the latter are in fact the classical brain waves. They are present bilaterally but are of higher amplitude on the parietal region contralateral to the side of the stimulus applied to the median nerve. Presumably at that side the brain wave amplitude is increased by the delayed potentials due to the conduction of some components of the signal travelling in the thin myelinated fibers. Indeed this study revealed the presence of recurrent delayed positive and negative foci in the parietal region contralateral to the side of the stimulus in addition to the late vertex components. Thus brain waves contribute to the temporal analysis of the stimulus.

Contributions to the history of the discovery of brain stem somato-sensory potentials.

The presence of an earlier latency of 12 msec of a somato-sensory evoked potential elicited by the stimulation of the median nerve at the wrist was discovered in 1963 by Liberson and Kim. They suggested its origin in the cervical spine or in the brain stem and possibly the cerebellum. Liberson, Voris and Uematsu recorded directly these potentials from the cervical spine and from the mesencephalon during surgery for pain in 1969 and published some of the findings in 1970. Cracco and Bickford confirmed in 1968 the findings of Liberson and Kim.

Contributions to the history of the discovery of P300.

Discovery of P300 was preceded by a number of EEG findings related to expectancy of a stimulus, starting with a classical paper of Adrian and including the well known publication of Grey Walter. Our own studies published with Ellen in 1960 demonstrated the occurrence of positive waves occurring in the hippocampus at the time of expected but non-existing stimuli.

Reciprocal relationship between the major EEG rhythms and latencies of evoked potential intermediate components. A tentative explanation.

We recently demonstrated that there is a reciprocal relationship between the known brain wave rhythms (delta, 3.3 c/sec, 5 c/sec, theta, alpha, spindle, and beta) on the one hand, and the averaged evoked potential mid component latencies, on the other. In other words, the latter are closely related to the periods of the known brain wave frequencies. In this paper we offer a hypothetical explanation of this puzzling relationship, by assuming the following: 1) Whenever the fastest component of a sensory signal reaches the cortex it depresses EEG except for those waves of different frequencies which at that very instant exhibit a high amplitude peak of a preferential polarity. One half period later, different in real time for each brain wave frequency, high amplitude peaks will emerge from the record with opposite polarity to that which was preferential at the time of the signals' arrival. These segmental peaks are the same as those that express evoked potential components of mid latencies. For the somatosensory evoked potentials the time of occurrence of these peaks are defined by the following expression: (Formula; see text) where N is equal to successive numbers between 1 and 12, as well as to the fractions of 1; 20 msec is the moment of arrival of the fastest signal to the cortex. Some of the latencies correspond to the arrival of the delayed components of the somatosensory signals. Some correspond to the time of arrival of the auditory and visual signals, in an apparent expectation of multi-sensory signals.(ABSTRACT TRUNCATED AT 250 WORDS)

Reinnervation of peripheral nerve grafts by spinal cord fibres tested by transcranial brain stimulation.

A scheme for surgery in patients with avulsed roots is represented by a rat model whose left sciatic nerve was grafted upon the right sciatic nerve, the proximal end of the graft being introduced into the spinal cord white matter. Transcranial stimulation, EMG recording, HRP and histological studies proved that the communication between the brain and the denervated muscles may be reestablished via the motoneurons, through the graft, bypassing the motor roots. Behavioral techniques were developed and will be tested in the future. The possibility of using neurotrophic drugs will be considered.

Obstetric brachial plexus palsy.

This article supplies data related to 11 operated children with obstetric brachial plexus palsy. Discussion of the obstetric background, pathology, pre- and postsurgical testing and of primary and secondary surgical reconstruction also is given. The need for rehabilitation regimen is stressed.