Chapter 1. Formaldehyde from Environment.- Chapter 2. Metabolism of Formaldehyde In Vivo.- Chapter 3. Formaldehyde and Catecholamine Neurotransmitters in Cognitive Impairment.- Chapter 4. Formaldehyde Serves as a Key Factor in the (De)methylation for Memory Formation.- Chapter 5. Dehydration, Formaldehyde, and Age-Related Cognitive Impairment.- Chapter 6. The Role of Formaldehyde in Cell Proliferation and Death.- Chapter 7. Gut Microbiota, Formaldehyde Dysmetabolism, and Cognitive Impairment.- Chapter 8. Multi-functional Protein Tau Aggregation and Cytotoxicity.- Chapter 9. Cognitive Ability and Impairment Related to Formaldehyde.- Chapter 10. Amyloid ß Deposition, Tau Phosphorylation, ApoE4 Dysfunction and Formaldehyde.- Chapter 11. Formaldehyde Exposure Leads to Circadian Rhythm, Anxiety, Depression, and Other Neuropsychiatric Disorders.- Chapter 12. Formaldehyde, Neuroinflammation and Cognitive Impairment.- Chapter 13. Formaldehyde in Stroke and Vascular Dementia.- Chapter 14. Formaldehyde in Diabetes and Cognitive Impairment.- Chapter 15. Formaldehyde Affects Lifespan and Stress Resistance in Drosophila.- Chapter 16. Molecular, Cellular, and Animal Experiments in Formaldehyde Study.- Chapter 17. Methods in Determination of Formaldehyde.- Chapter 18. Potential Drug Interventions on Formaldehyde Induced Neuronal Toxicity.