Figure 12.
Schematic illustrating our working hypothesis regarding the relationship between the processing of semicircular canal signals between the afferents, the NU and the VN. Semicircular canal afferents carry head-referenced angular velocity (ω), but the NU encodes only the earth-horizontal component (ωEH). Thus, because of Purkinje cell inhibition, NU-target neurons in the VN should carry the earth-vertical component (ωEV = ω − ωEH). Importantly, because the NU canal-driven responses are temporally integrated, VN responses are predicted to encode earth-vertical canal signals with a longer time constant than canal afferents. This is because, assuming for simplicity an ideal integration, ωEV = ω − ω/s = ω (s − 1)/s, where s is the complex frequency. Indeed, many VN neurons exhibit longer time constants, attributed to velocity storage influence (Reisine and Raphan, 1992). We have proposed that this framework underlies the rationale and functional relevance of what has been previously known as velocity storage (Green and Angelaki, 2003).