This study will advance the understanding of the cellular mechanisms underlying hyperactive reflexes and loss of motor control in chronic SCI. Though not proposed as treatment agents at this stage, the pharmacological PIC antagonists and NMDA antagonist used in this study are intended as tools to understand the mechanisms of hyperexcitability. Therapeutically, the ability to manipulate neuronal excitability (e.g. to increase specificity in volitional strength or decrease hyper-reflexia) may lead to more effective treatments. Riluzole and isradipine provide artificial, yet specific, control of PICs. Memantine also provides a degree of control of synaptic NMDA-mediated post-synaptic currents. Understanding the cellular mechanisms of SCI impairments and their modulation may identify novel approaches to control spinal neuron excitability and provide appropriate tailoring of pharmacological treatments specific to the attributes of an individual's spasticity and impairments.