Study Group

Twenty-seven elderly participants, who were 55 years of age or older and able to communicate with the experimenters, were recruited. The following exclusion criteria were applied: (1) a history of major physical or psychiatric disorders, including epilepsy, major depression, schizophrenia, or neurovascular diseases, (2) a history of brain injury or brain surgery, and (3) the inability to undergo an MRI due to physical or psychological contraindications. The participants were recruited via advertisements at local community centers and at the Taipei Veterans General Hospital. The study was approved by the Institutional Review Board of the National Yang Ming University and the Taipei Veterans General Hospital, Taiwan. Written informed consent was provided by all participants before the start of the experiment. One participant was excluded due to a failure of imaging acquisition, and one participant was excluded due to severe deterioration in masticatory performance (see Results), and therefore, 25 participants were included (Table ​(Table11).

Demographic, behavioral, and clinical profiles of the study group.

CASI, the Cognitive Abilities Screening Instrument; GDS, the Geriatric Depression Scale-short form (GDS); MPI, Masticatory Performance Index; N, number of participants.

^aData conform to a normal distribution, based on Ryan Joiner test.