Trends in Cognitive Sciences
Volume 17, Issue 9, September 2013, Pages 442-449
Journal home page for Trends in Cognitive Sciences

Opinion
Re-establishing the merits of electrical brain stimulation

https://doi.org/10.1016/j.tics.2013.07.002Get rights and content

Highlights

  • Direct electrical stimulation (DES) is an invaluable method for neuroscience.

  • Claims that DES is a poorly understood, potentially misleading method are unfounded.

  • DES has specific, causally interpretable effects at well-defined anatomical sites.

  • DES also reduces dramatically postoperative deficits in brain-damaged patients.

During the past decades, direct electrical stimulation (DES) has been a key method not only in determining the organization of brain networks mediating movement, language, and cognition but also in establishing many central concepts of modern neuroscience, such as the electrical nature of neural transmission, the localization of brain functions, and the homuncular arrangement of sensorimotor areas. However, recent criticisms have questioned the utility of DES and argued that data collected with this technique may be flawed and unreliable. As with every other neuroscientific method, DES does have limitations. However, existing evidence argues strongly for its validity and usefulness by demonstrating that DES produces highly specific outcomes at well-defined anatomical sites and significantly minimizes postoperative deficits in brain-damaged patients.

Section snippets

Merit of electrical brain stimulation: a long-standing controversy

Approximately 150 years ago Fritsch and Hitzig discovered that direct electrical stimulation (DES) of the cerebral cortex of dogs evokes localized, topographically organized muscle contractions in the contralateral hemibody [1]. This discovery led several researchers to use electrical stimulation to probe the anatomic and functional organization of the brain 2, 3. David Ferrier was perhaps one of the most famous. Using DES in various animal species, he reported that complex, ethologically

DES and the sensorimotor system

In humans, several motor-related cortical areas (designated ‘motor areas’ hereafter) have been shown to evoke movements when electrically stimulated [5], including the primary motor cortex (M1) [16], the primary somatosensory cortex (S1) [17], the premotor cortex (PMC) [6], the supplementary motor area (SMA) [18], and the cingulate cortex (CC) [19]. Interestingly, these areas are widely interconnected with each other and they all have direct efferent projections to the spinal cord 20, 21, 22, 23

DES and cognitive functions

Although most authors agree that DES is a unique tool for identifying causal links between neural processes and specific cognitive functions 29, 43, 52, 53, 54, detractors of this technique assert that the propensity of electrical current to spread in a random, unpredictable manner within brain networks precludes every possibility of causal reasoning 13, 14. This criticism is mainly based on the claim that stimulation outcomes are dramatically variable and heterogeneous. In support of this

DES and clinical mapping

Probably the most direct and convincing evidence that DES has specific, highly reliable effects comes from the successful use of this technique during functional perioperative mapping in human patients with brain tumors. Since the pioneering work of Penfield and Boldrey, DES has proved highly efficient for identifying eloquent regions related to motor and cognitive functions 5, 53, 76, 77, which allows the dramatic reduction in the occurrence of permanent postoperative sequelae in the patients

Concluding remarks

To summarize, it appears that, during the past century, DES has provided a unique body of knowledge about the anatomo-functional organization of the brain 29, 43, 52, 53, 54, 58. However, despite this extremely valuable contribution, the same criticisms keep appearing in the literature to challenge the relevance and reliability of DES results (Box 3). The evidence reviewed in this paper shows that these ritualistic, knee-jerk criticisms are no longer tenable when the actual scientific

Acknowledgments

This work was funded by CNRS, the ‘Cortex’ Labex Program, and the Agence Nationale de la Recherche (ANR-11BSV40271; ANR-12-BSV4-0018-01) to A.S. and M.D.

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