Recurrent Connections between the Pontine Respiratory Group and Ventrolateral Medullary Respiratory Column through Parallel Functional Pathways

Abstract

We have previously identified correlational neuronal assemblies within the medullary raphe nuclei and dorsolateral pons (PRG) as well as evidence for their influences on a ‘core’ network within the ventrolateral medullary respiratory column (VRC) (Nuding et al. 2002 & 2004). To identify extended correlational linkages, multi-electrode arrays were placed concurrently in these three areas in 10 decerebrated, vagotomized, ventilated cats. Up to 118 neurons were recorded simultaneously and evaluated for respiratory modulation and other unit characteristics, yielding a database with 685 single neurons [VRC: 272; PRG: 123; raphe: 290] and cross-correlograms from 20,697 pairs of neurons. The results provide support for PRG-VRC neural interactions proposed in a recent pontine-medullary respiratory network model (Lindsey et al. 2005). Moreover, multiple neuron correlations are consistent with recurrent pathways between the VRC and the PRG that include intervening raphe cells. Evidence has been found for 26 PRG→raphe→VRC and 34 VRC→raphe→PRG ‘serial’ connections. More than half of these ‘A-to-B-to-C trios’ involve a non-respiratory modulated cell (NRM), and 11 include an additional C-to-A inferred recurrent loop connection. These parallel functional pathways and NRM cell involvement must be considered in future models of the respiratory brainstem. Support: NIH grants NS46062 (under the NSF-NIH CRCNP) & NS19814.