Direct electrical stimulation evidence for a dorsal motor area with control of the larynx

Laryngeal motor control is crucial in a variety of fundamental behaviors, including swallowing and breathing, and in humans, spoken language and vocalization. Proximate control of the laryngeal muscles during speech production is known to be supported by ventral laryngeal motor cortex (vLMC) [1]. More controversially, a human-unique and recently evolved dorsal laryngeal motor cortex area (dLMC) with direct (mono-synaptic) control of laryngeal muscles through the nucleus retroambiguus has been proposed [2,3]. This dorsal laryngeal motor control area is the focus of the current investigation. Patient AJ presented at the age of 27 with a tumor in the right frontal lobe undercutting the superior and middle frontal gyri (Fig. 1a). AJ had no discernible cognitive, sensory or motor impairments prior to surgery (Supplemental Online Materials). Because of the proximity of the lesion to motor cortex, and because preoperative fMRI suggested involvement of right frontal regions in speech production, the surgery for removal of the tumor was carried out using an asleep-awake-asleep procedure for language and motor mapping [4]. The rare clinical opportunity to explore direct electrical stimulation mapping of dLMC in the right hemisphere of a left-language-dominant individual allowed us to assess the specific role of dLMC in speech production. During the awake portion of his surgery, AJ completed 70 trials of a picture naming task in which he read a short preamble (‘This is a...) and then named a target picture (e.g., ...CAT.”). 7 of the 70 trials were excluded from analyses because of interruptions unrelated to stimulation (e.g. patient talking to clinicians). Of the remaining 63 trials, 33 were paired with DES to the cortical surface and 30 were without stimulation. Of the 33 trials paired with stimulation, 12 were characterized by disruptions to the patient’s speech production. Of the 30 trials not paired with stimulation, three trials were marked by observable errors; there was a significant effect of stimulation on the likelihood of error (12/33 vs 3/30; c2 1⁄4 4.7;