Researchers at the Stanford University in the US used a method to turn skin cells from people with "Timothy syndrome" -- who often display autistic behaviours -- into brain cells.
They found abnormal activities in these cells which were, however, corrected partially using an experimental drug.
This means, the researchers said, the findings present a useful target for scientists looking to examine what goes wrong in the developing brain of a child with autism, the BBC reported.
Compared with the millions of people worldwide thought to show characteristics of autism, Timothy syndrome is very rare and it affects an estimated 20 people across the globe.
For the study, published in the journal Nature Medicine, the researchers used a newly-developed technique to generate brain cells called neurons from only a sample of the patient's skin. This allowed them to examine their development in the laboratory, and even use them to test out possible treatments.
They found obvious differences between neurons grown from Timothy syndrome patients, and those from healthy "controls".
The healthy neurons developed into different subtypes, ready for work in different regions of the brain, while it was very different in the Timothy syndrome samples -- more were equipped to work in the upper part of the cerebral cortex, and fewer in the lower part.
This meant there were fewer neurons equipped to work in a part of the brain called the corpus callosum, which helps the left and right "hemispheres" of the brain communicate.
These differences echoed those already observed in mice specially bred with the Timothy syndrome genetic fault.
In addition, the neurons were making too much of a particular body chemical linked to the manufacture of dopamine and norepinephrine, which play a significant role in sensory processing and social behaviour.
Dr Ricardo Dolmetsch, who led the study, said that the abnormalities found tallied with other evidence that autism was due in part to poor communication between different parts of the brain.
The team managed to reduce significantly the number of these malfunctioning neurons by adding a drug they developed.
This, they said, meant it might be possible one day to treat this defect in a real patient, although the drug used was not currently suitable for children due to side-effects.
The National Autistic Society in UK, however, gave a cautious welcome to findings, and warned that they did not necessarily offer insights into every form of autism.
Researcher Georgina Gomez said: "Timothy syndrome is only one form of autism and so these findings only give a very limited picture of what might cause the condition.
"More work would need to be done to substantiate this particular piece of research."