Miniature, engineered reconstructions of the developing brain were found to have patterns of neural activity that resemble those recorded in very young brains, researchers reported Thursday.

The findings are the most comprehensive analysis to date of the functional characteristics of these tiny lab-grown human brain models, according to neuroscientists, raising hopes that the technology could be harnessed to study normal brain development and to find new therapies for brain disorders. The work raises ethical concerns about eventually re-creating brain functions, like pain perception and consciousness, in the lab, some researchers and ethicists said.

Researchers in Japan reported neural activity in similar models in a study earlier this year, but they didn’t compare it to activity recorded from human brains.

For the study, researchers grew mini brain-like reconstructions for up to 10 months in special containers lined with sensors that recorded the activity of neurons, or brain cells, weekly. The older the brain-like blobs were, the more complex their spontaneous neural activity patterns were, mimicking what happens in real developing brains, according to the study, which was published in the journal Cell Stem Cell.