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: These results suggest that alterations in cerebellar sensory processing function , occurring secondary to abnormal basal ganglia signals reaching it , may be an important element contributing to the maladaptive sensorimotor plasticity of M1 and the emergence of abnormal involuntary movements .
### Output Text:
These results suggest that alterations in cerebellar sensory processing function , occurring secondary to abnormal basal ganglia signals reaching it , may be an important element contributing to the maladaptive sensorimotor plasticity of M1 and the emergence of abnormal involuntary movements . 