Conjectures of Braverman-Kazhdan, L. Lafforgue, Ngô and Sakellaridis imply that all affine spherical varieties admit generalized Poisson summation formula. In this dissertation we establish a generalized Poisson summation formula for certain spaces of test functions on the zero locus of a quadratic form. The functions are built from the Whittaker coefficients of automorphic representations on $\mathrm{GL}_n$. We also give an expression of the local factors where all the data are unramified.