The authors have used scanning gate microscopy combined with numerical simulations to analyze local carrier and current modulation effects in InAs semiconductor nanowires grown by metal-organic chemical vapor deposition. Measurements of current flow in the nanowire as a function of probe tip position, at both high and low drain bias, reveal that carrier and current modulation is strongest when the probe tip is near the source and drain nanowire contacts, and decreases at greater tip-contact distances. The measured transconductance is approximately 80% greater near the source contact for high drain bias condition and 120% greater near the drain contact for low drain bias condition, respectively, than at the center of the nanowire. Numerical simulations for different tip positions relative to the metal contact confirm that carrier modulation should be stronger when the tip is closer to the source or drain contact than at the center of the wire, consistent with the experimental measurements.