Austrian doctors say the eldest daughter of Elisabeth Fritzl, the woman imprisoned for 24 years by her father, is showing signs of recovery.
Kerstin, 19, is still on life support, but doctors are now considering whether to bring her out of an induced coma.
Her illness and admission to hospital led to the discovery of the cellar where the family was held.
Elisabeth and her five other children are continuing to receive round the clock care at another clinic.
Dr Albert Reiter, from Amstetten hospital, said that the amount of sedation medication Kerstin was receiving had been slowly reduced and that for the first time her medical team was considering whether to begin the process of bringing her out of the coma.
However he could not say how long this would take.
Josef Fritzl fathered seven children with his daughter Elisabeth - one of whom died when very young, three of whom were kept imprisoned in his cellar, and three others who went on to live with Mr Fritzl as his adopted or fostered children.
Mr Fritzl's alleged crimes came to light when Kerstin became seriously ill in April.
She was allowed out of the cellar and admitted to hospital in Amstetten.
Police then issued an appeal to Elisabeth Fritzl to contact them about her daughter, and later picked up Mr Fritzl and Elisabeth near the hospital.
Dr Berthold Kepplinger, director of the psychiatric clinic where Elisabeth and her five other children are being treated, said the family was being given advice on making plans for the future.
He said teachers had begun giving the children lessons and that they were spending time reading books and playing computer games and table football.
Over recent weeks, the clinic has been besieged by paparazzi photographers. Dr Kepplinger appealed to the media to leave the family alone and said they needed privacy to recuperate.
Mr Fritzl is being held in police custody and has not yet been formally charged. He has said he was driven by an addiction that "got out of control".