Our study investigates the facial recognition of patients with Alzheimer's disease and whether there is impairment in the neural pathway of holistic processing of facial recognition through a composite facial task.

Difficulty of facial recognition is one of the presentations of Alzheimer's disease. Previous studies focused on the recognition of facial expression, famous faces or familial faces. Another study showed a reduced face inversion effect. However, whether holistic processing of facial recognition is impaired is less investigated.

We recruited 11 patients with mild Alzheimer's disease (Clinical dementia rating 0.5~1) and 18 age, sex and education-matched control. We retrieved faces from Taiwan corpora of Chinese emotions and relevant psychophysiological data and removed hair and facial hair with digital technique. We made composite faces with neutral facial expression and asked participants to decide if the upper half of two simultaneously presented faces were the same (Composite facial task). The same tests were done with upside down alignment faces. A cognitive battery was performed. We compared the correct rate of both groups and correlated it with other cognitive tests.

Patients with mild Alzheimer's disease (AD) had lower correct rate than normal control (NC) in both faces with normal alignment (AD v.s. NC : 0.63 v.s. 0.72, p<0.01) and upside down (AD v.s. NC : 0.61 v.s. 0.70, p<0.01). The correct rate of faces recognition with normal alignment is correlated with scores of Mini-Mental State Examination (MMSE)(0.335, p<0.05) and Picture Completion Task (PCT)(0.352, p<0.05). The correct rate of faces recognition with upside down alignment is not correlated with scores of all other cognition tests.

Our study showed that patients with mild Alzheimer's disease had impaired holistic processing of facial recognition. Also, the neural pathway of facial recognition may be different in different face alignment.