Characterization of the networks formed between neurons and glioblastoma cells enables targeting of these networks with the potential to improve treatment, according to new research. Researchers used retrograde tracing with modified rabies virus to visualize neuron–tumour networks in patient-derived glioblastoma spheroid cultures, which revealed widespread connections. Surprisingly, the connections were strengthened by radiotherapy alone, which potentially explains the therapeutic resistance of glioblastoma, but were decreased by radiotherapy in combination with inhibition of neural activity. Furthermore, development of the modified rabies virus retrograde tracing approach enabled selective ablation of tumour-connected neurons, which led to a reduction in tumour cells.