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Benjamin Libet (1916–2007)
Published in Andrew P. Wickens, Key Thinkers in Neuroscience, 2018
One possible objection to this conclusion is that direct electrical stimulation of the brain is a highly artificial procedure. Hence, a more realistic test of Libet’s hypothesis came when he ran a similar type of experiment, but this time stimulated the medial lemniscus – a large ascending pathway that carries sensation from the skin, joints and muscles to the ventral thalamus, from where it passed to the somatosensory cortex (fortunately for Libet, some of Feinstein’s patients already had electrodes placed in this pathway). Again, the findings showed that touch sensations were never consciously reported from stimulation of the medial lemniscus, unless they were at least 500 msecs in duration. In Libet’s terminology, this was the amount of time needed for neuronal adequacy to produce a conscious sensation. Interestingly, this seemed to contradict the fact that a brief stimulus of just a few milliseconds applied to the skin can often be consciously perceived. But in further studies, Libet showed that even a brief “touch” stimulus of a few milli seconds resulted in the occurrence of evoked potentials in the somatosensory cortex that exceeded the 500 msec threshold.
Anatomy
Published in Stanley A. Gelfand, Hearing, 2017
The lateral lemniscus (LL) is the pathway from the lower nuclei of the auditory pathway just described to the level of the inferior colliculus, and has been described in some detail (e.g., Ferraro and Minckler, 1977a; Brunso-Bechtold et al., 1981; Glendenning et al., 1981; Moore, 1987; Schwartz, 1992; Helfert and Aschoff, 1997; Kelly et al., 2009). Each LL includes neural fibers originating from the cochlear nuclei and superior olivary complexes on both sides, as well as fibers arising from the nuclei of the LL itself. Communication between the lateral lemnisci of the two sides occurs via the commissural fibers of Probst. In mammals, the LL typically includes a ventral nucleus (VNLL), a dorsal nucleus (DNLL), and an intermediate nucleus (INLL). However, while the human brain has a rather well-defined DNLL, its VNLL and the INLL are only sparsely represented.
Non-Synonyms (Similar-Sounding)
Published in Terence R. Anthoney, Neuroanatomy and the Neurologic Exam, 2017
Medial lemniscus* (B&K, p. 275): An ascending brainstem tract, associated functionally with touch sensation mediated by spinal nerves (i.e., exclusive of the pre-auricular head). When used without modifiers, terms such as “lemniscal fibers” or“lemniscal pathway” usually refer to structures associated with the medial lemniscus.
CI in single-sided deafness
Published in Acta Oto-Laryngologica, 2021
Anandhan Dhanasingh, Ingeborg Hochmair
The auditory pathway starts in the cochlea from the inner hair cells of the organ of Corti which send the signal to the spiral ganglion cell bodies (SGCB) through the peripheral neural fibres in response to the acoustic signal. The central axons of the SGCB form the cochlear nerve, and the vestibular nerve joins the cochlear nerve entering the internal auditory meatus (IAM) – commonly called as cochlear-vestibular nerve – which is a clinically relevant location, as any damage to it would normally affect both, auditory and vestibular functions. The nerve in the IAM travels a short distance of around 1cm to reach the surface of the brainstem at the ventral (anterior) cochlear nuclei (CN). Until CN, the neural fibres coming from each ear are kept separated on their own sides. The neural fibres from the ventral CN extend to the dorsal (posterior) CN, and from here most of the fibres cross the midline, travelling up in the contralateral (opposite) lateral lemniscus. At the same time, some fibres travel up in the ipsilateral (same side) lateral lemniscus. From the ventral CN, most of the neural fibres travel up to reach the contralateral superior olivary nuclei, whereas some neural fibres reach the ipsilateral superior olivary nuclei as well (Figure 1).
Intraoperative Neuromonitoring and Lumbar Spinal Instrumentation: Indications and Utility
Published in The Neurodiagnostic Journal, 2021
Ryan C. Hofler, Richard G. Fessler
Most IONM modalities fall into one of three main categories. Somatosensory-evoked potentials (SSEPs) are recorded cortically and subcortically in response to continuous stimulation of select peripheral nerves, such as the tibial and peroneal nerves during lumbar spine surgery, thereby assessing the somatosensory pathways of the posterior column-medial lemniscus. Motor-evoked potentials (MEPs) reflect function of the corticospinal tract elicited by applying intermittent electrical transcranial stimulation with recordings made in the form of compound muscle action potentials from various bilateral upper and lower extremity muscle groups. Electromyography (EMG) can be performed continuously (c-EMG) to assess the function of an individual myotome throughout a procedure or can be triggered (t-EMG) at specific points in a procedure for the purpose of nerve detection and compromise (Biscevic et al. 2020; Fehlings et al. 2010; Lall et al. 2012). In the present discussion, we present several approaches to the instrumentation of the lumbar spine with accompanying uses for multimodal IONM to maximize complication avoidance.
Syringobulbia: A delayed complication following spinal cord injury – case report
Published in The Journal of Spinal Cord Medicine, 2019
Christina Mousele, Miltiadis Georgiopoulos, Constantine Constantoyannis
Regarding the neuroanatomical background of the aforementioned patient’s clinical presentation the following plausible explanations can be provided. The concurrent existence of sensory loss, concerning pain and temperature sensation, of the right upper extremity and hypoesthesia of the right side of the face can be only explained by dysfunction of the left lateral spinothalamic tract (2nd order neuraxons) and the left trigeminal lemniscus. The muscle wasting and weakness, concerning especially the most delicate movements of the right hand, should be attributed to injury of the left corticospinal tract. The dysphagia and the dysphonia should be associated with dysfunction of the vagus (pneumogastric) nerve.