Abstract Speed of Processing is a cognitive measure represents a fundamental limiting step in the performance of routine cognitive tasks. Because this measure is so sensitive to cognitive decline caused by age, brain injury or disease, it is often examined as a benchmark for diagnosis of cognitive health, but also as a target of cognitive remediation and enhancement. Measure of Speed of Processing is often with tasks such as the Digit-Symbol Substitution Test (DSST) derived from the Wechsler Intelligence Scales which is widely employed due to its ease of use and sensitivity, however the DSST like most behavioral tasks has been reported to have a learning effect. In this study we sought to study changes in neural efficiency associated with learning during adaptation to a variant of the DSST, the Symbol-Digit Substitution Test (SDST), by imaging the dorsolateral prefrontal cortex (dlPFC) with functional near Infrared Spectroscopy (fNIRS). Additionally, we explored how task expertise might be affected by short trains of different Transcranial Magnetic Stimulation (TMS) methods including Sham, Single Pulse, High Frequency, and Theta Burst Stimulation (TBS). Preliminary results suggest that neural efficiency measures are sensitive to learning by practice, and that neurostimulation such as High Frequency and TBS-based TMS may further increase efficiency.