Genioglossus and Intrinsic Electromyographic Activities in Impeded and Unimpeded Protrusion Tasks

Abstract

Eight muscles invest the human tongue: four extrinsic muscles have external origins and insert into the tongue body and four intrinsic muscles originate and terminate within the tongue. Previously, we noted minimal activation of the genioglossus tongue muscle during impeded protrusion tasks (i.e., having subjects push the tongue against a force transducer), suggesting that other muscles play a role in the production of tongue force. Accordingly, we sought to characterize genioglossus tongue muscle activities during impeded and unimpeded protrusion tasks (i.e., having subjects slowly and smoothly move the tongue out of their mouth). Electromyographic (EMG) and single motor-unit potentials of the extrinsic genioglossus muscle were recorded with tungsten microelectrodes and EMG activities of intrinsic tongue muscles were recorded with hook-wire electrodes inserted into the anterior tongue body. Tongue position was detected by an isotonic transducer coupled to the tongue tip. Protrusive force was detected by a force transducer attached to a rigid bar. Genioglossus and intrinsic tongue muscles were simultaneously active in both impeded and unimpeded protrusion tasks. Genioglossus whole muscle EMG and single motor-unit activities changed faithfully as a function of tongue position, with increased discharge associated with protrusion and decreased discharge associated with retraction back to the rest position. In contrast, during the impeded protrusion task drive the genioglossus muscle remained constant as protrusion force increased. Conversely, intrinsic tongue muscle activities appropriately followed changes in both tongue position and force. Importantly, we observed significantly higher levels of intrinsic muscle activity in the impeded protrusion task. These observations suggest that protrusion of the human tongue requires activation of the genioglossus and intrinsic protrudor muscles, with the former more important for establishing anterior-posterior tongue location and the latter playing a greater role in the generation of protrusive force. A biomechanical model of these actions is provided and discussed.

A comprehensive assessment of genioglossus electromyographic activity in healthy adults

“…We recorded multiunit EMG activity in the GG using two electrode types (see below). In the anterior region, EMG activities were recorded via bipolar intramuscular hook-wire electrodes (50 m; California Finewire, Grover Beach, CA) inserted via the mouth, as described previously (Sauerland and Harper 1976;Williams et al 2000;Pittman and Bailey 2009;Richardson and Bailey 2010). Each hook wire was bared of ϳ2-3 mm insulation at the tip, threaded through a 30-gauge needle (0.3 ϫ 13 mm; Becton-Dickinson, Franklin Lakes, NJ), and inserted bilaterally, immediately posterior to the lingual sulcus at points equidistant from the lingual frenulum to a depth ϳ12 mm from the mucosal surface (Sauerland and Harper 1976;Eastwood et al 2003).…”

Tongue interface based on surface EMG signals of suprahyoid muscles

“…The EMG activity of the lingual muscles has been studied using tungsten microelectrodes and hook-wire electrodes [31] and surface electrodes [32] placed within the oral cavity. However, intra-oral electrodes are unsuitable for the practical control of assistive devices.…”

Métodos quantitativos para avaliação da força de língua

“…Eletrodos de superfície apresentam algumas vantagens em relação aos intramusculares, pois os primeiros são mais fáceis de utilizar e apresentam maior aceitação por parte dos pacientes. Entretanto, para medir a atividade eletromiográfica da musculatura intrínseca da língua, são necessários eletrodos intramusculares 37 .…”