Motor speech disorders
Motor speech disorders are a class of speech disorder that disturb the body's natural ability to speak. These disturbances vary in their etiology based on the integrity and integration of cognitive, neuromuscular, and musculoskeletal activities. Speaking is an act dependent on thought and timed execution of airflow and oral motor / oral placement of the lips, tongue, and jaw that can be disrupted by weakness in oral musculature (dysarthria) or an inability to execute the motor movements needed for specific speech sound production (apraxia of speech or developmental verbal dyspraxia). Such deficits can be related to pathology of the nervous system (central and /or peripheral systems involved in motor planning) that affect the timing of respiration, phonation, prosody, and articulation in isolation or in conjunction.
Dysarthria is the reduced ability to motor plan volitional movements needed for speech production as the result of weakness/paresis and/or paralysis of the musculature of the oral mechanism needed for respiration, phonation, resonance, articulation, and or prosody.
Apraxia is an acquired inability to motor plan volitional movement for speech production in the absence of muscular weakness.
Developmental verbal dyspraxia
Developmental verbal dyspraxia is a developmental inability to motor plan volitional movement for the production of speech in the absense of muscular weakness. Research has suggested links to the FOXP2 gene.