Interaction between central pattern generators for breathing and swallowing in the cat.

Abstract

SUMMARY1. We examined the interaction between central pattern generators for respiration and deglutition in decerebrate, vagotomized, paralysed and ventilated cats (n = 10), by recording activity from the following nerves: hypoglossal, phrenic, thyroarytenoid and triangularis sterni. Fictive breathing was spontaneous with carbon dioxide above the apnoeic threshold (end-tidal Pco2, 32 + 4 mmHg) and fictive swallowing was induced by stimulating the internal branch of the left superior laryngeal nerve (SLN) continuously (0-2 ms pulse duration, 10 Hz).2. In all ten animals, SLN stimulation evoked short bursts of thyroarytenoid and hypoglossal nerve activity indicative of fictive swallowing. In two of ten animals, respiration was inhibited completely during deglutition. In the other eight animals, fictive breathing and swallowing occurred simultaneously.3. With SLN stimulation below threshold for eliciting swallowing, the respiratory rhythm decreased, the duration of inspiration did not change but the duration of expiration, especially stage II, increased. Integrated nerve activities indicated that the rate of rise and peak of phrenic nerve activity decreased, stage I expiratory activity of the thyroarytenoid and especially that of the hypoglossal nerve increased and stage II expiratory activity of the triangularis sterni nerve was suppressed completely. However, if inspired carbon dioxide was increased, i.e. hypercapnic ventilation, stage II expiratory activity remained partially during continuous SLN stimulation.4. Fictive-swallowing bursts occurred only at respiratory phase transitions. At the minimal stimulus intensity that evoked repetitive swallowing bursts, the pattern of interaction between breathing and swallowing central pattern generators was consistent for each animal (n = 7) but was different across animals. In four animals, fictive swallows occurred at the phase transition between stage II expiration and inspiration, at the transition between inspiration and stage I expiration in one animal; and in two other animals, at the transition between stage I and II of expiration.

Respiratory phase resetting and airflow changes induced by swallowing in humans.

“…At present there is insufficient evidence to make a clear choice between these possibilities, or to suggest that both are involved. However, corticofugal inputs are not required because swallowing in decerebrate animals is associated with normal alterations in respiratory timing (Miller & Sherrington, 1916;Hukuhara & Okada, 1956;Sumi, 1963;Altschuler, Davies & Pack, 1987;Dick et al 1993). Airflow changes during deglutition Deglutition was associated with a characteristic sequence of oronasal airflow changes: (1) rapid decrease in airflow;…”

“…The neural signal that links the initiation of swallowing with alterations in respiratory rhythm has not been characterized. Two broad explanations are that: (1) activation of the deglutitive pattern generator within the brainstem in turn causes alteration in rhythm-generating respiratory neurones (Dick, Oku, Romaniuk & Cherniack, 1993); or (2) pathways that facilitate the deglutitive neural generator, such as SLN, corticofugal fibres, and relay sites such as the NTS, cause parallel alterations in respiratory rhythm-generating neurones, without direct influences of the deglutitive generator. At present there is insufficient evidence to make a clear choice between these possibilities, or to suggest that both are involved.…”

Intrinsically Motivated Learning of Real-World Sensorimotor Skills with Developmental Constraints

“…Examples of innate sensori primitives include visual movement detection and tracking systems (Bronson, 1974), basic human facial expression perception (Johnson, 2001;Meltzoff and Moore, 1977), or special auditory filters tuned for speech processing in humans (Sekuler and Blake, 1994). Examples of motor primitives include central pattern generators such as for leg oscillations (Cazalets et al, 1995), synergies for reaching with the hand (d 'Avella et al, 2006), closing the fingers in a coordinated manner such as used in grasping (Weiss and Flanders, 2004), or of course skills such as breathing or swallowing (Dick et al, 1993). Of course, the existence of these primitives does not avoid the fundamental need for learning, even for the most basic skills: those primitives are typically parameterized, and thus can typically be seen as parameterized dynamical systems which semantics (affordances in particular), parameter values to be set and combination for achieving given tasks have to be learnt.…”

Swallow and breathing coordination following suprahyoid muscle injury.

“…The expiratory phase is known to predominate during swallowing in both intact and decerebrate feline models (Dick et al, 1993;Doty & Bosma, 1956). …”

“…With normal adults, the E-E pattern dominates during a swallow (Martin-Harris et al, 2005;Martin-Harris, Brodsky, Price, Michel, & Walters, 2003), meaning air flows out of the system before and after a swallow. Studies with anaesthetized (Doty & Bosma, 1956) or decerebrated (Dick, Oku, Romaniuk, & Cherniack, 1993) cats have reported that the E-E phase predominates during swallowing.…”