In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: This study demonstrates that the deficient sensorimotor M1 plasticity in 16 patients with LIDs could be reinstated by a single session of real inhibitory cerebellar stimulation but not sham stimulation .
### Output Text:
This study demonstrates that the deficient sensorimotor M1 plasticity in 16 patients with LIDs could be reinstated by a single session of real inhibitory cerebellar stimulation but not sham stimulation . 