Cerebellar responsiveness to stimulation of the lingual spindle afferent fibers in the hypoglossal nerve of the rhesus monkey

Sensory cortical tongue representation in man

Extensive data on cortical tongue representation were analyzed in 100 patients who underwent craniotomy and cortical mapping by electrical stimulation for surgical treatment of epilepsy. As noted in the literature, the tongue is extensively represented within the central nervous system with a highly organized sensorimotor system and the data from this study corroborate a large cortical representation of the human tongue over the postcentral gyrus. The tongue was found to have a clear somatotopic organization over the postcentral area and to be represented bilaterally to a significant degree. Furthermore, the tongue appears to have an asymmetrical sensory cortical representation, as cerebral dominance for speech is more extensively represented on the dominant hemisphere. Cortical tongue mapping has proved extremely useful in determining the point of junction of the central and Sylvian sulci, a crucial landmark during surgical cortical resections.

Linguistic Universals: Implications of a Neurological Reappraisal of Jakobson's Phonological Hierarchy

An ongoing research project designed to test Jakobson's claim of a universal rank order among the elements of phonological systems is described and illustrated. The strategy is that of close analysis, on surface, feature and neuromuscular levels successively, of phonetically deviant L2 performance data. While the first two analytical stages tend to corroborate the existence of widely valid cross-language constraints, the third yields evidence for an explanatory hypothesis in terms of the properties of participant neuromuscular mechanisms. It is argued that this ‘physiological hypothesis’ is superior to rival ‘nativist’ postulates in placing Jakobson's hierarchy on a firm ontological footing.

Tonic stretch reflexes in lip, tongue and jaw muscles

Despite considerable speculation it remains unclear as to whether stretch reflexes perform a functional role in speech articulator muscles. Recent research, however, has shown that long loop stretch reflex mechanisms are brought into play during voluntary contraction of limb muscles and a functional role in oscillatory damping has been suggested. It was decided, therefore, to use a method and a technique of analysis similar to that used in limb muscles to search for tonic stretch reflex (TSR) responses in lip, tongue and jaw muscles during sustained voluntary contraction. The term 'action TSR' is used to differentiate stretch reflex responses measured from voluntary activity from those measured at rest. Simultaneous electromyogram (EMG) recordings were taken from the lip, tongue and jaw musculature in normal, stutterer and cerebral spastic subjects. Subjects were instructed to hold the appropriate articulator in a fixed position while the experiment applied an irregular, continuously changing, stretching force. The stretch and EMG signals were analyzed using a cross correlation and spectral analysis technique. This provided a sensitive means of detecting any EMG fluctuations which covaried with applied stretch and might therefore be classified as reflex. No suggestion of such action TSR responses could be found in lip or tongue muscles of any of the subjects tested, including the cerebral spastic subjects with dysarthric speech. It is therefore concluded that action TSR mechanisms are not operative in control of lip and tongue muscles in man. Furthermore, dysarthric speech in cerebral spasticity cannot be attributed to exaggerated tone of lip and tongue muscles resulting from hypersensitivity of TSR mechanisms. In contrast, clear action TSR responses were demonstrable in jaw closing muscles while in jaw opening muscles, small amplitude responses were detected but were not substantial in comparison with background activity. Since the action TSR is present in jaw and limb muscles, but absent in lip and tongue muscles, the suggestion of a functional role of this reflex in damping mechanical oscillations associated with inertial loads is further supported.