Identifying Cerebral Hemodynamic Patterns in Mood Disorders and Mild Cognitive Impairment: A Functional Near-Infrared Spectroscopy (fNIRS) Study

Inclusion Criteria General Inclusion Criteria (across all diagnostic groups): * 18 years and older * Ability to provide written informed consent * Adequate cognitive and language abilities to understand and complete study tasks, including clinical assessments and fNIRS procedures * Confirmed clinical diagnosis of major depressive disorder, bipolar disorder, or mild cognitive impairment (MCI) * Stable psychiatric or cognitive condition, without acute episodes requiring immediate intervention Specific Inclusion Criteria (for diagnostic groups): * Healthy control o No past or current psychiatric or cognitive disorder * Major depressive disorder (MDD): * Diagnosis of major depressive disorder, confirmed through clinical evaluation. * No history of bipolar disorder or psychotic symptoms. * Bipolar disorder: o Diagnosis of bipolar disorder I or II, confirmed through clinical evaluation. * Mild Cognitive Impairment (MCI): * Pre-existing clinical diagnosis of mild cognitive impairment, supported by neuropsychological testing and/or MRI, PET scan data. * No history of major psychiatric disorders, such as major depression, bipolar disorder or schizophrenia. Exclusion Criteria General Exclusion Criteria (across all diagnostic groups): * Active primary psychotic or substance use disorders (except nicotine dependence) within the past year * Any severe or unstable medical condition that could interfere with participation or data collection * Any active neurological condition (including seizure disorder, traumatic brain injury, stroke) that could affect cognitive functioning or brain imaging results * Inability to comply with study procedures, including cognitive testing, fNIRS assessment, or other assessments required by the protocol * Pregnant women will be excluded due to potential physiological changes that could affect study outcomes Specific Exclusion Criteria (for diagnostic groups): * Healthy control o Any past or current psychiatric or cognitive disorder * Major depressive disorder (MDD): * Diagnosis of bipolar disorder or schizophrenia. * Brain stimulation therapy within the past 3 months. * Bipolar disorder: o Diagnosis of schizophrenia or schizoaffective disorder. * Mild Cognitive Impairment (MCI): * Diagnosis of dementia. * Significant cognitive impairment preventing understanding or completion of study tasks.