The pLPFC activity is unlikely to encode absolute motion coherence levels, as the difference in coherence activity between the accuracy and speed conditions was not even discernable in the brain region (i.e., MT+) most sensitive to the type of motion coherence display used in the present experiment.
In a blocked-trial design, we contrasted brain activity obtained while participants made a motion discrimination response to a dynamic dot display containing 60% motion coherence with brain activity acquired while subjects passively viewed a static version of the dot display.
This task involved detecting and judging the direction of motion coherence in a dynamic random-dot display while emphasizing either the speed or accuracy of the decision.
In the motion coherence condition, the trial was identical except that the static display was substituted by a dynamic display in which 60% of the 100 dots moved in a coherent direction, either leftward or rightward, with the remaining 40% of dots moving in random directions.
As detailed in Table 3 and displayed in Fig. 1A, and consistent with the motion coherence threshold results, EL, the left ventral patient, performed normally in all conditions, while the performance of SM, the right ventral patient, was out of the normal range for the slower (5.4°/s) and the fastest (27.27°/s) speeds, but not the medium speed (10.8°/s).
The perception of motion in basic, non-form tasks (motion coherence and motion detection) and complex structure-from-motion, for a wide range of motion speeds, all centrally displayed, was assessed in five patients with a circumscribed lesion to either the right or left ventral visual pathway.
The baseline trials were included to assess baseline activity in the absence of any motion coherence, while the 2%/s trials served to ensure that subjects were attending to motion coherence of the display from trial onset.
It is important to emphasize that we kept the experimental paradigm as close as possible to that of the motion coherence threshold paradigm, including the timing and duration of the trials, the size, colours and luminance of the circular display, the number, size and colour of dots in the display, and the lifetime of the dots (for the dots in the signal and the noise dots).
Perception of visual motion coherence by rats and mice.
We devised a multi-element orientation task where orientation coherence sensitivity could be measured in a comparable way to motion coherence.
