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Q Aziz

Publications and source records attributed to Q Aziz.

43 records · Page 3Linked to original sources
PubMed1997

Cranial nerve modulation of human cortical swallowing motor pathways.

Animal data indicate that cortical swallowing pathways can be modulated by cranial nerve afferent stimulation. We therefore studied the effects of human trigeminal and vagal nerve excitation on the corticofugal pathways to the oropharynx and esophagus, using electromagnetic stimulation. Unilateral stimulation of either the trigeminal or vagus nerve evoked two distinct reflex electromyographic responses in the pharynx and esophagus, an early response (latency range 19-30 ms) and a late response (latency range 42-72 ms). In the mylohyoid muscles, however, only a single response was seen (latency range 36-64 ms). Cortical stimulation also evoked electromyographic responses in the mylohyoid muscles, pharynx, and esophagus, with latencies of 8.5 +/- 0.3, 9.3 +/- 0.3, and 10.1 +/- 0.4 ms, respectively. When either trigeminal or vagus nerve stimulation preceded cortical stimulation, the cortically evoked responses were facilitated, with maximal effects at interstimulation intervals of 30-200 ms for pharynx and esophagus (P < 0.02) and at interstimulation intervals of 50-100 ms for mylohyoid muscles (P < 0.05). Our results demonstrate that stimulation of human cranial nerve afferent fibers facilitates cortical swallowing motor pathways.

Adult↗
PubMed1996

The topographic representation of esophageal motor function on the human cerebral cortex.

BACKGROUND & AIMS: Corticofugal pathways to the human esophagus have been recently identified in humans using transcranial magnetic stimulation. The aim of this study was to determine the topographic representation of the esophagus on the cerebral cortex. METHODS: Focal magnetic stimulation of 1-cm areas was performed over both hemispheres in 10 healthy subjects. Esophageal electromyographic responses were recorded 2 cm below the upper esophageal sphincter. The studies were repeated to determine reproducibility in 3 subjects; in 2 subjects, esophageal topography was compared with thenar muscle topography. RESULTS: In all subjects, esophageal electromyographic responses were evoked by stimulation of either the right or left hemisphere. Largest amplitude responses were obtained anterior to those of the thenar muscles, indicating that the esophagus may be represented on either the anterior aspect of the motor cortex or on the premotor cortex. In all subjects, the area of response was asymmetric, being more extensive on the right hemisphere than on the left hemisphere in 8 subjects. In 2 subjects, the area of response on the left hemisphere was more extensive than on the right. Repeat studies showed that this asymmetry was consistent. CONCLUSIONS: Esophageal motor function shows bilateral cortical representation with consistent interhemispheric asymmetry.

Adult↗
PubMed1996

The cortical topography of human swallowing musculature in health and disease.

Because no detailed information exists regarding the topographic representation of swallowing musculature on the human cerebral cortex in health or disease, we used transcranial magnetic stimulation to study the cortical topography of human oral, pharyngeal and esophageal musculature in 20 healthy individuals and the topography of pharyngeal musculature in two stroke patients, one with and one without dysphagia. Our results demonstrate that swallowing musculature is discretely and somatotopically represented on the motor and premotor cortex of both hemispheres but displays interhemispheric asymmetry, independent of handedness. Following stroke, dysphagia appeared to be associated with smaller pharyngeal representation on the intact hemisphere, which increases in size with recovery of swallowing.

Adolescent↗
PubMed1995

Modulation of esophageal responses to magnetic stimulation of the human brain by swallowing and by vagal stimulation.

BACKGROUND & AIMS: Although magnetic stimulation of the human cerebral cortex activates corticoesophageal pathways, it is not known whether these pathways are mediated via brain stem neurons activated during swallowing and by vagal afferents. The aim of this study was to determine the effect of swallowing and vagal stimulation on esophageal electromyographic responses evoked by magnetic stimulation of the human cortex. METHODS: Magnetic stimulation of the cortex was performed in 7 subjects at variable intervals after swallows and at intervals ranging from 10 to 200 milliseconds after vagal stimulation in 5 subjects. RESULTS: Between swallows, cortical stimulation induced both early (10.1 +/- 0.5 milliseconds) and late (52.3 +/- 2.3 milliseconds) esophageal electromyographic responses with amplitudes of 66.9 +/- 23.4 microV and 32.9 +/- 7.4 microV, respectively. During swallowing, both responses were facilitated because their latencies decreased (8.9 +/- 0.5 milliseconds and 47.3 +/- 4.8 milliseconds, respectively), whereas their amplitudes increased (203.1 +/- 54 microV and 79.8 +/- 22.5 microV, respectively). Vagal stimulation facilitated the early cortically evoked response. Its latency decreased from 10.2 +/- 0.2 milliseconds to 8 +/- 0.2 milliseconds, whereas its amplitude increased from 145.1 +/- 44 microV to 230.5 +/- 41.6 microV. CONCLUSIONS: Corticoesophageal pathways activated by magnetic stimulation of the human cortex share the same population of brain stem motor neurons to the upper esophagus that are activated during swallowing and vagal stimulation.

Adult↗
PubMed1995

Topographic mapping of cortical potentials evoked by distension of the human proximal and distal oesophagus.

We describe cortical potentials evoked by balloon distension of the proximal and distal oesophagus in 8 healthy right handed volunteers. Oesophageal stimulation was performed using a pump which rapidly inflated a 2 cm silicone balloon positioned either 3 cm distal to the upper oesophageal sphincter or 5 cm proximal to the lower oesophageal sphincter, at a frequency of 0.2 Hz, using inflation volumes which produced a definite but not painful sensation. Oesophageal evoked cortical potentials were recorded in all subjects with an initial negative and positive component (N1 and P1), followed by a second negative and positive component (N2 and P2) in 6 subjects. The morphology and the scalp topography of the N1 component elicited by proximal and distal oesophageal stimulation suggests activation of the primary somatosensory cortex and/or the insular. There was also evidence for hemispheric dominance for the N1 potential which was independent of handedness. The frontal emphasis of the proximal oesophageal N1 component, in contrast to the central emphasis of the distal oesophageal N1 component, suggests that different neuronal populations were activated by stimulation of the two sites. The frontal emphasis of the ensuing P1 component from both oesophageal sites suggests that it originates in a separate precentral source. The topography of the N2 components obtained by stimulation of either oesophageal site was similar to that of the N1 component, suggesting that they originate in similar areas of the cortex. The P2 component evoked by stimulation of both oesophageal sites was localised at the vertex. The inter- and intra-subject variation in the morphology of the N2 and P2 components suggests that secondary cortical processes related to cognition may be involved in their generation.

Adult↗
PubMed1994

Esophageal myoelectric responses to magnetic stimulation of the human cortex and the extracranial vagus nerve.

We describe the use of magnetic stimulation of the human motor cortex and the extracranial vagus nerve in the neck to study human esophageal electromyographic (EMG) responses. Diffuse cortical stimulation produced both an early and a late EMG response in the proximal esophagus with latencies of 10.9 +/- 0.5 and 43.4 +/- 4.3 ms, respectively. Increasing the stimulation intensity increased the amplitude and duration, but reduced the latency, of the early response (P < 0.01), whereas the late response remained unchanged. The early response, but not the late response, was facilitated when cortical stimulation was performed during valsalva maneuver. Maximal early response amplitudes were obtained by focal stimulation of either hemisphere 4-8 cm lateral to the vertex. Stimulation of the neck over the extracranial vagus nerve at the angle of the jaw also produced an early and a late EMG response in the proximal esophagus with latencies of 4.3 +/- 0.4 and 56.8 +/- 14.5 ms, respectively. Early responses were also recorded in the midesophagus and distal esophagus from either cortical or vagal stimulation, but amplitudes were smaller and rise times were longer, suggesting passive "volume conduction" from the proximal esophagus. Comparison of laryngeal, pharyngeal, and esophageal early EMG responses showed similar amplitudes and rise times, suggesting that the action potentials were generated locally at each site and that true esophageal responses were being detected.

Adult↗