OBJECTIVES: Apathy has been reported as the most prevalent behavioural symptom experienced in Alzheimer's disease (AD), associated with greater functional decline and caregiver distress. The aim of the current study was to investigate structural correlates of apathy in AD using magnetic resonance imaging (MRI) regional volume and regional cortical thickness measures.METHODS: Semi-structured interviews were conducted with 111 AD patients and their caregivers as part of the European multi-centre study AddNeuroMed. Apathy was measured using the apathy domain of the Neuropsychiatric Inventory (NPI). All AD patients were scanned using a 1.5T MRI scanner and the images analysed using an automated analysis pipeline.RESULTS: We found apathy to be the most prevalent neuropsychiatric symptom occurring in 57% of patients. Apathetic patients had significantly greater cortical thinning in left caudal anterior cingulate cortex (ACC) and left lateral orbitofrontal cortex (OFC), as well as left superior and ventrolateral frontal regions, than those without apathy symptoms.CONCLUSIONS: Apathy is mediated by frontocortical structures but this is specific to the left hemisphere at least for patients in the mild to moderate stages of AD.