Understanding Variable Motor Responses to Direct Electrical Stimulation of the Human Motor Cortex During Brain Surgery

Abstract

Direct electrical stimulation of the brain is the gold standard technique used to define functional-anatomical relationships during neurosurgical procedures. Areas that respond to stimulation are considered “critical nodes” of circuits that must remain intact for the subject to maintain the ability to perform certain functions, like moving and speaking. Despite its routine use, the neurophysiology underlying downstream motor responses to electrical stimulation of the brain, such as muscle contraction or movement arrest, is poorly understood. Furthermore, varying and sometimes counterintuitive responses can be seen depending on how and where the stimulation is applied, even within the human primary motor cortex. Therefore, here we review relevant neuroanatomy of the human motor system, provide a brief historical perspective on electrical brain stimulation, explore mechanistic variations in stimulation applications, examine neurophysiological properties of different parts of the motor system, and suggest areas of future research that can promote a better understanding of the interaction between electrical stimulation of the brain and its function.

Diffusion tensor imaging, intra-operative neurophysiological monitoring and small craniotomy: Results in a consecutive series of 103 gliomas

“…On the other hand, when the tumor is near the motor area then TC MEP may not be useful and MEP should be performed with a cortical strip while mapping with monopolar and, in case, bipolar stimulation. HF monopolar stimulation demonstrated to be an efficient and reliable tool with equal safety and efficacy when compared to bipolar stimulation techniques ( 66 , 67 ). Furthermore, HF monopolar stimulation showed high reliability even when CST is infiltrated by the tumor ( 68 ).…”

Quantifying Hand Strength and Isometric Pinch Individuation Using a Flexible Pressure Sensor Grid

“…The authors of this manuscript have diverse backgrounds with a common interest in hand therapeutics related to central or peripheral nervous system injury [9,12,[66][67][68][69]. Although many groups have studied hand strength and function, there is no standardized, objective, and repeatable platform to assess isometric pinch individuation that can be shared across specialties and facilities over time [70][71][72][73][74].…”

“…Grasping objects, for example, often begins with visual perception and generation of a motive to reach [6][7][8]. Motor planning in the frontal and parietal cortices is then followed by upper motor neurons in the primary motor cortex (M1) firing to activate their distal counterparts in the spinal cord [9]. This signal is then translated across the neuromuscular junction to the muscles of the hand and the upper extremity in motor units [10,11].…”

Synchronization of kinetic and kinematic hand tasks with electrocorticography and cortical stimulation during awake craniotomies

“…There is a long, rich history of intraoperative neurophysiological experimentation leading to advances in the understanding of neurophysiology and neuroanatomy that continues today [ 1 ]. Specific to hand motor physiology, for example, several groups have recently quantified positive and negative motor responses to stimulation of the precentral gyrus when flexing/extending upper limbs and motor suppression during a knob turning task with stimulation of the precentral gyrus [ 2 , 3 ].…”