Fig. 2.
Neurons are tuned to referent directions of shifts of the spatial frame of reference in which they function. A: a neuron receives afferent influences from the position (x, y) of the hand in the environment. The same change in the membrane potential can result from different changes in the threshold positions of the hand, comprising a single threshold line. The neuron can be active or silent at positions above or below this line, respectively. B: a central change in the membrane potential results in a shift in the threshold line. The referent (threshold) hand position is shifted to a certain point on this line (vector Δh; p is the initial hand position). Only the component of this vector orthogonal to the threshold line (Δh⊥) affects the membrane potential and activity of this neuron. Δh‖, component of vector Δh along the initial (parallel) threshold line; hm, orthogonal projection of vector Δh where subscript m refers to the length of Δh. C: in the case when the neuron is active at position p, only the orthogonal component of shifts in the spatial thresholds affects the activity of the neuron.