Basu has reportedly acknowledged former prime minister H D Deve Gowda who went to visit him in AMRI hospital.
"A doctor tried to wake him up. He lifted his hand. He did not open his eyes," Deve Gowda said.
AMRI hospital medical superintendent Debasish Sharma told in a news agency report that the Basu's health was improving.
"He is slightly better. He was put on full ventilation Thursday night as a precautionary measure, but the support has again been reduced to partial since morning. This is a good indicator," Sharma said.
Sharma added that the Basu's urine output, blood pressure and oxygen content in blood have also improved.
The veteran leader was put on ventilator support following acute breathing problem on Jan 6.
The former West Bengal chief minister was hospitalized with pneumonia on Jan 1.