The purpose of this study is to learn about possible changes in brain anatomy and in thinking abilities, such as memory skills, in patients with cancer who receive treatment with chemotherapy alone or in combination with total body radiation before undergoing stem cell transplantation.

Inclusion Criteria:

• Diagnosed with acute myeloid leukemia (AML), acute lymphoblastic leukemia (ALL), acute undifferentiated or biphenotypic leukemia, myelodysplastic syndrome (MDS), Hodgkin's lymphoma, (HL) or non-Hodgkin's lymphoma (NHL), and in complete remission at the time of enrollment
• Are scheduled to undergo conditioning treatment with (1) total body radiation (TBI) and chemotherapy or (2) chemotherapy alone prior to receiving a myeloablative allogeneic HSCT
• Between 18 and 70 years of age.
• Are English speaking.
• Have capacity to give consent.

Healthy Control Inclusion Criteria:

• Have no diagnosis of cancer except basal cell carcinoma
• Between 18 and 70 years of age.
• Are English speaking.
• Have capacity to give consent

Exclusion Criteria:

• Patients with signs and/or symptoms of central nervous system disease as determined by their physician or by a brain MRI, either at the time of enrollment or during the study period.
• With disease progression at the time of enrollment or during the study period
• With self-reported Axis I psychiatric disorder (DSM-IV), major affective disorder (untreated), bipolar disorder, schizophrenia
• With a history of a neurological disorder, neurodegenerative disease, or traumatic brain injury with loss of consciousness
• With standard contraindications to MRI examinations

Healthy Control Exclusion Criteria:

• Exposure to chemotherapy or radiation therapy for any medical condition
• With self-reported Axis I psychiatric disorder (DSM-IV), major affective disorder (untreated), bipolar disorder, schizophrenia
• With a history of neurological disorders, neurodegenerative disease, or traumatic brain injury with loss of consciousness
• With standard contraindications to MRI examinations

Subjects will be identified and recruited to participate in the study by Memorial Sloan-Kettering Cancer Center (MSKCC) and Weill Cornell Medical Center (WCMC).