11/9/2023 0 Comments Eloquent brain regions10 They performed these studies at the home of Fritsch because the University of Berlin would not permit such experimentation on animals. 7 His experiments were highly publicized and became Mary Shelley’s main inspiration in the creation of her 1818 novel, Frankenstein: “Perhaps, a corpse would be reanimated galvanism had given token of such things.” 8 It was Luigi Rolando who first used galvanic current to stimulate the cerebral cortex of living animals in 1809, 9 but it was Fritz and Hitzig in 1870 who systematically built a body of mapping research by applying electricity to the exposed cerebral cortex of dogs without anesthesia and are credited with the first demonstration of the function of the motor strip. Giovanni Aldini (1756–1826), nephew of Luigi Galvani, used Alessandro Volta’s bimetallic pile (a primitive battery) to apply electric current to “reanimate” dismembered bodies of animals and humans. The interest and fascination with direct cortical electrical stimulation parallel the earliest awareness of the electrical nature of neural transmission. Everything which is complex is unusable.” This dichotomy is commonly referred to as Bonini’s paradox, 5 and best interpreted by the French poet Paul Valéry 6: “Everything simple is false. In light of this important observation, we discuss not only the theoretical characteristics of each method but also the importance of its practical utility. With regard to functional brain mapping, it is best to remember that there is a dichotomy between the accuracy of a map and its usability. Attention will also be paid to current innovations in electrical stimulation techniques and novel methodologies that may complement or replace ESM in the future. This article attempts to review the historical origins, current applications, and apparent limitations of ESM. Novel noninvasive techniques exemplified by transcranial magnetic stimulation (TMS) and passive techniques utilizing electrocorticographic spectral analysis of broadband gamma frequencies are both supplementing, and in some cases supplanting, ESM as the clinical mapping method of choice. Important potential successors to ESM have arisen to challenge conventional mapping strategies that have been somewhat invariant for decades. Cortico-cortical evoked potentials represent this most modern innovation of electrical stimulation to express networks beyond local excitatory and inhibitory influences. More recently, attention has also been placed on its summation effects at distant sites. Up to the present, most studies have focused on the discrete effects of stimulation on the stimulated nodes. Thus, it is a nonphysiological and a “lesional” method. Finally and curiously, despite its common clinical usage internationally over the past century, the technique is not standardized.įundamentally, ESM uses electrical stimuli to inhibit or excite function. This limitation considerably reduces the list of cognitive tasks that can be performed. The evocation of afterdischarges (AD) and seizures often limits the length of stimulation trains or entirely cancels the utility of the method. In the operating theater, time constraints are even more severe compared to the EMU, and there are the anesthetic challenges of awake craniotomies. It is typically applied late in the course after seizure collections and restoration of antiepileptic drugs, typically on the eve of a patient’s epilepsy surgery. In the semi-chronic setting of the EMU, it is time-consuming and commonly requires hours and sometimes days. 2– 4 Perhaps no other method for delineating brain function possesses both its practical applicability and its proven causality.ĭespite its long history and undeniable practical utility, ESM also has clear and broadly acknowledged shortcomings whether performed in an epilepsy monitoring unit (EMU) with dedicated implanted subdural or depth electrodes or intraoperatively in either the anesthetized or awake state. Abundant small and retrospective studies (i.e., level IV evidence) have documented that ESM-guided neurosurgical resective strategies eliminate or minimize sensorimotor and linguistic postoperative deficits. Practical application of conventional ESM methods produces specific and reliable outcomes at defined sites. Despite the development of modern tools such as functional magnetic resonance imaging (fMRI) and diffusion tractography (DT), ESM has survived as a dominant method for delineating cortical function in both clinical and research domains. Historically, the evolution of ESM defined the electrical nature of neural transmission and pioneered the localization of brain function. 58) 1Īcross three centuries, electrical stimulation mapping (ESM) has remained a pivotal method in medicine and systems neuroscience. Alfred Korzybski ( Science and Sanity, p.
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