we create parallel synaptic paths, and even entirely new brain cells, that can jump our trains of thought onto new, innovative tracks. 

这是二个并列分句的宾语都带有相同的定语从句，因而简化为一个句子。

we create parallel synaptic paths that can jump our trains of thought onto new, innovative tracks，and we create even entirely new brain cells that can jump our trains of thought onto new, innovative tracks. 

所以，that从句为限制性定语从句，既修饰paths，也修饰brain cells。