Such fibers rise from the airway and input the NTS [ 30, 31].
However our data would suggest that a significant population of trigeminal neurons may relay airway afferent input to thalamic loci, likely via well described trigeminothalamic tracts [ 37].
These data support our assertion that the medial thalamus is also involved in encoding airway sensory input, although it seems likely that this relates to affective processing relating to anxiety, fear and arousal involving the limbic brain as opposed to sensory perception or discrimination per se [ 37, 38, 43].
We have begun to assess the anatomy of the ascending circuitry that arises from the airways and provides input to the cortex using a novel viral neural tracing system.
For the individual characteristics input, the airway morphometry selected was the human Yeh/Schum symmetric lung model (Yeh and Schum 1980).
It calculates deposition and clearance of particles ranging from ultrafine (0.001 μm) to coarse (100 μm) in the respiratory tract, based on user-provided input on airway morphometry, clearance rates, particle properties (density, diameter, and size distribution), and exposure scenario (aerosol concentration, activity breathing pattern, and exposure duration).
Data were fit into the constant phase model in order to fractionate total respiratory input impedance into airways resistance (R N), tissue damping coefficient (G) and tissue elastance coefficient (H) [ 15, 27].
For variations to the inputs for individual characteristics (Table 3), the choice of airway morphometry using the the human stochastic lung model resulted in a lower retention compared with the symmetric lung model.
While NMDA and AMPA/Kainate receptor contribute to the excitatory inputs and in the activity-dependent plastic changes of NTS during airway hyperreactivity [ 58, 59].
In addition to higher brain descending pathways that regulate the motor act of coughing, it is now well established that higher order sensory pathways receive inputs from the airways and play an important role in generating cognitive sensory responses to airways irritation [ 12- 14].
