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: However , the learning and memory performance was assessed using passive avoidance paradigm , and for spatial cognition evaluation , Y - maze task was used .
### Output Text:
However , the learning and memory performance was assessed using passive avoidance paradigm , and for spatial cognition evaluation , Y - maze task was used . 