The study objective is to correlate global cognition and episodic memory performance to resting state fMRI functional connectivity. This is a non-treatment, prospective, natural history data collection study in a cross-sectional cohort of patients with cognitive impairment.

At present, Magnetic Resonance Imaging (MRI) is widely used along with other tests to help diagnose dementia, however diagnosis still remains challenging. There is currently a focus on the usefulness of resting state functionalMRI (RS fMRI) as a way of establishing differences in functional connectivity between healthy subjects and those with various neurodegenerative disorders. Although the potential for RS fMRI to be used as a biomarker for neurological diseases looks promising, further research is needed, especially regarding validation of normal values and seed-based functional connectivity. Further research into this area will help to improve the ability to appropriately classify new subjects and ultimately allow use of RS functional connectivity as a biomarker. This is a nontreatment, prospective, natural history data collection that aims to analyse functional connectivity in a cohort of patients with suspected cognitive impairment. Correlation of global cognition and episodic memory performance to resting state fMRI functional connectivity will be evaluated. Patient population will include patients over the age of 18 with cognitive impairment and age and gender matched controls. Eligible patients will have to complete neuropsychological and clinical assessments and complete an fMRI scan prior to enrolment.Study duration is estimated at 4 years.

Inclusion Criteria:

• Informed consent
• Cognitive impairment
• Age from 18 to 100 years
• On stable medication for 1 month before the screening visit; on or off cholinesterase inhibitors
• Fluency in English and adequate premorbid intellectual functioning

Exclusion Criteria:

• Any contraindication to MRI scanning
• Clinically significant psychiatric disorder (e.g. depression)
• Current clinically significant illness that could confound the results of the study
• History of alcohol or drug dependence or abuse
• Current use of anticonvulsant or narcotic medications.

Patients with suspected cognitive impairment, mild cognitive impairment, autosomal dominant Alzheimer's disease, late onset Alzheimer's disease, Vascular dementia, Parkinson's dementia and age and gender matched controls.