Lead scientist Dr Hilary Toulmin, from the Centre for the Developing Brain at King's College London, said: "The next stage of our work will be to understand how these findings relate to the learning, concentration and social difficulties - which many of these children experience as they grow older."
Scientists used functional magnetic resonance imaging (fMRI) scans to map the brain connections of 66 infants, 47 of whom were born prematurely before 33 weeks of pregnancy.
Babies born in the "normal" birth window of 37 to 42 weeks gestation were found to have a similar brain structure to adults in key areas known to develop rapidly during the time a premature baby is cared for in a neonatal unit.
But those born early had less connectivity between parts of the thalamus and specific regions of the brain's cortex that support higher mental functions.
At the same time, they had more connectivity between the thalamus and an area of the primary sensory cortex involved in processing signals from the face, lips, jaw tongue and throat.
The stronger "face" connections may reflect early exposure to breast and bottle feeding, say the authors, while reduced connectivity in other areas could lead to problems seen in later childhood.
Professor David Edwards, director of the Centre for the Developing Brain, said: "The ability of modern science to image the connections in the brain would have been inconceivable just a few years ago, but we are now able to observe brain development in babies as they grow, and this is likely to produce remarkable benefits for medicine."
The research, published in the journal Proceedings of the National Academy of Sciences, showed that babies born the most prematurely displayed the greatest abnormalities in brain connectivity.