Ultimately this imbalance between inhibitory and excitatory activities leads to the manifestation of typical clinical symptoms that include resting tremor, rigidity, postural instability, and slowed movement.
Now, as you may know, the binding of glutamate to the NMDA receptor results in an influx of extracellular calcium, which controls membrane excitability and synaptic transmission.
Some researchers suspect that this deficiency takes the breaks off glutamates excitery activity thus stimulating things like repetitive behavior documents money and then his colleagues produced evidence supporting this idea.