Sentence:  The yawning gap in neuroscientists' understanding of their topic is in the intermediate scale of the brain's anatomy. Science has a passable knowledge of how individual nerve cells, known as neurons, work. It also knows which visible lobes and <WSD>ganglia</WSD> of the brain do what. But how the neurons are organised in these lobes and <WSD>ganglia</WSD> remains obscure. 
Meaning of the word marked with <WSD> tags:  Any of certain masses of gray matter in the brain, as the basal ganglia.