Date of Degree
H. Philip Zeigler
Adcy1; barrel cortex; mouse behavior; Prxxl1; trigeminal; vibrissal
A striking feature of the vibrissal representation in rodents is the presence; at brainstem (barrellettes), thalamic (barrelloids) and cortical levels (barrels) of a somatotopically organized pattern of neurons which is isomorphic, both morphologically and physiologically, to the pattern of vibrissae on the snout. The vibrissal system is required for several classes of behavior, including feeding and active vibrissal sensing, but the functional role of the patterning in these behaviors is unknown. We used two mutant animals lacking patterning in two areas of the vibrissal neuraxis to examine the functional role of patterning. We examined feeding behavior using a knockout of Prxxl, which abolishes somatotopic barrellette patterning in the lemniscal brainstem nucleus. Null animals were significantly smaller than littermates by postnatal day 5, but reached developmental landmarks at appropriate times, and survived to adulthood on liquid diet. A careful analysis of infant and adult ingestive behavior revealed subtle impairments in suckling, increases in time spent feeding and the duration of feeding bouts, feeding during inappropriate times of day, and difficulties in the mechanics of feeding. During liquid diet feeding, null mice displayed abnormal behaviors including extensive use of the paws to move food into the mouth, submerging the snout in the diet, changes in licking, and also had difficulty consuming solid chow pellets. We suggest that barrellette patterning is necessary for normal ingestive behavior. To examine the role of patterning in active sensing, we used the BRL mouse, an Adenylyl Cyclase 1 mutant in which TCAs enter the cortex but do not cluster into barrels. Prior studies lesioning or chemically silencing barrel cortex suggests that vibrissal active sensing tasks such as texture discrimination are barrel-cortex dependent. However, these studies confound the functional role of the somatotopic barrel patterning with the function of barrel cortex cell activity. Use of the BRL mouse allowed us to dissociate these two. We found that BRL mice are impaired in a texture discrimination task relative to wildtype mice, suggesting a functional role for cortical barrel patterning. We discuss the role of patterning versus topographical organization of afferents.
Bakalar, Dana, "Molecular-Genetic and Behavioral Analysis of the Functionality of Patterning in the Trigeminal Neuraxis" (2015). CUNY Academic Works.