Linear spatio-temporal convergence in vestibular neurons of the primate nucleus fastigii

Vestibular responses in the primate fastigial nucleus (FN) do often not follow the simple cosine tuning observed in primary vestibular afferents. The present report demonstrates that these more complex patterns can mostly be attributed to simple linear summation of spatially and temporally diverse cosine-tuned input signals (linear spatio-temporal convergence, STC). Analyses following from this elementary finding, however, reveal frequency-dependent properties in many FN neurons, which are difficult to reconcile with existing concepts of possible functions of STC in central vestibular areas. The demonstration that STC linearity holds for FN responses is thus of both theoretical and practical relevance, allowing shortening of future experimental protocols and facilitating comparison of the observed spatio-temporal response dynamics with those at other stages of vestibular signal processing.