Activity patterns within the genioglossus during suckling in domestic dogs and pigs: interspecific and intraspecific plasticity.

Suckling is universal among terrestrial mammals, but it is not clear whether mechanisms of suckling are the same in mammals of differing morphology or feeding ecology. An evaluation of the literature on tongue movements during suckling suggests that pigs and dogs may use the tongue differently, with humans being intermediate. Electromyographic (EMG) recordings of the middle and posterior portions of genioglossus of pigs and dogs were compared in order to (1) see whether neuromotor patterns for tongue movement during suckling can be recognized and (2) identify interspecific differences in neuromotor patterns if present. A single pattern of coordination was found in dogs, but results from pigs indicated plasticity, both within and between individuals. The literature on humans indicates that, as in pigs, suckling patterns may vary. In addition to the difference in variability, pigs and dogs differed in EMG burst duration and cycle length. The performance of suckling in pigs, dogs and humans, respectively, resembled the tongue movements used in drinking in each species. The greater plasticity of suckling behavior in pigs (and possibly humans) may be related to an ability to acquire milk under a variety of environmental conditions or to a generally variable feeding process characteristic of omnivorous mammals.