About 80 children rescued from a Boko Haram camp in Cameroon cannot remember their own names or where they come from, reports the BBC.
The claim was made by aid official Dr Christopher Fomunyoh, a director for the US-based National Democratic Institute (NDI), which works to strengthen democratic institutions in the developing world.
Fomunyoh visited the children in an orphanage where they are being rehabilitated after being rescued from the camp in November.
He told the BBC's Randy Joe Sa'ah in Yaounde that they had spent so long with their captors, who had indoctrinated them with Boko Haram's Islamist ideology, that they had lost track of who they were.
"They've lost touch with their parents," he said. "They've lost touch with people in their villages, they're not able to articulate, to help trace their relationships, they can't even tell you what their names are."
Boko Haram has recently declared itself to be affiliated with Islamic State in Iraq and Syria. It controls parts of Nigeria and has expanded its terror operations into neighbouring countries.
Suspected Boko Haram militants attacked the town of Ngamdu in Nigeria's northeast Borno state yesterday, killing about a dozen people. The town, which has been hit several times by militants, lies on the border of Borno and Yobe states. Borno is the heartland of Boko Haram's six-year insurgency.
A security source said the casualties and wounded were mainly bus and truck drivers. Around six drivers died, he said.
This is the second time in a week that militants have hit towns along this road; two suicide bombers blew themselves up at a checkpoint at Beneshiek on Saturday.
With help from Chad and Niger, Nigeria has recaptured several key towns in the last few weeks and Boko Haram has been largely pushed out of Adamawa and Yobe states. On Monday, Chadian and Nigerian troops freed the towns of Malam Fatouri and Damasak from militant control.
Until recently, the insurgents controlled an area the size of Belgium.
Additional reporting by Reuters.