V1 opponency

The strength of V1 motion direction opponency is determined by several parameters in the <v1> object. These are described below.

  opponent_w       1.0       # [0.0] Weight of opponent signal (1.0 = full opp.)
  opponent_min_tf  0.1 (Hz)  # [0.0] Opponency 'w' is zero for TF < this value
  opponent_rect    1         # [0] 1-half-wave rectify after opponency; 0-do not

The opponent weight parameter, opponent_w, specifies the weight, w, of the opponent signal and ranges from 0 (none) to 1 (full). Zero is the default value if no value is given. For full opponency, the signal in a direction channel, say direction 0 (rightward), is modified by subtracting w times the signal in the 180 deg opposite channel (leftward).

The opponent minimum TF parameter, opponent_min_tf, sets the minimum TF value for which opponency will be applied. For STF channels with TF less than this value, the opponent weight will be set to zero, but any rectification will still occur (but might have no effect given that the energy signal is non-negative).

The opponent rectification parameter, opponent_rect, specifies whether the signal is half-wave rectified following the opponent subtraction.