Meet Our Doctors

Dr. Ramya Rangamannar earned her bachelor’s degree from Barnard College at Columbia University and her master's and doctorate degrees in Clinical Psychology from the University of Hartford. She completed her pre-doctoral clinical internship at the University of Florida and post-doctoral fellowship in pediatric neuropsychology at the Children’s Hospital Colorado.

Over the last decade, Dr. Ramya has gained clinical expertise in a multitude of settings (i.e., medical, psychiatric, private practice) with children from early toddlerhood through early adulthood. Despite specialization in pediatrics, Dr. Ramya has also worked with younger and older adult populations in her training. She prides herself on understanding the "whole child" in the context of their home/family, school, and social realms and in providing families with tangible resources and recommendations in supporting their child’s development and success.

Dr. Dorothy Nguyen-Daniels earned her doctoral degree with a concentration in neuropsychology from the Illinois School of Professional Psychology. She completed her pre-doctoral internship at Truman Memorial Veterans’ Hospital in Missouri and her two-year postdoctoral fellowship in neuropsychology at the University of Kansas School of Medicine-Wichita. In addition, she obtained a master’s degree in gerontological counseling from Adler University in Illinois.

Dr. Nguyen-Daniels provides comprehensive outpatient evaluations of adults and older adults presenting with various neurological conditions, including dementia, mild cognitive impairment, concussion/traumatic brain injury, neurodegenerative disease, stroke, cerebrovascular disease, epilepsy, movement disorders, autoimmune disorders, and complex medical/psychiatric conditions. She also has experience conducting pre-surgical evaluations (e.g., epilepsy, DBS) and inpatient consultations. In her clinical work, Dr. Nguyen-Daniels strives to use a thorough, compassionate, and culturally-sensitive approach that enables patients to understand better their strengths, areas of growth, and helpful resources to function and feel their best.

Dr. Molly Sullan earned her doctorate degree in clinical psychology, with a specialization in neuropsychology, from the University of Florida. She completed her pre-doctoral internship and her two-year neuropsychology fellowship at the VA San Diego Healthcare System/University of California, San Diego.

Dr. Sullan’s research has focused on understanding the relationship between post-traumatic sleep difficulties and cognitive, psychological, and physiological recovery for patients with a history of acquired brain injury (e.g., traumatic brain injury and stroke). Clinically, she has experience in the assessment of a broad spectrum of neurological disorders both in inpatient and outpatient settings, including brain tumors, epilepsy and movement disorders (e.g., Parkinson’s disease), memory disorders and dementia, stroke and cerebrovascular disease, traumatic brain injury, demyelinating lesions, autoimmune disorders, complex psychiatric concerns, substance use disorders, and neurodevelopmental considerations.

Dr. Sullan is an affiliate faculty member at Horizon, which means that she does not currently see patients clinically. She works in research and remains involved with the HNS didactic series related to the HNS training program.

Dr. Alexis Sliva earned her bachelor’s degree in psychology from University of Wisconsin - River Falls and her master’s and doctorate degrees in school psychology from the University of Denver. She completed her pre-doctoral internship and post-doctoral fellowship in clinical psychology at a private practice in Las Vegas, Nevada, with an emphasis on forensic psychology.

Dr. Sliva’s early training focused on supporting students and families from the school environment. Her clinical training has focused on intervention, evaluation, and assessment across community resource center and private practice settings. While she specialized in childhood to early adulthood, she also worked with adult populations. She has experience in the assessment of mood disorders, anxiety, PTSD, psychosis, ADHD, and learning disabilities. In addition, her forensic experience consisted of completing Court ordered evaluations (e.g., child custody, risk, and certification). She is passionate about working with families to establish diagnostic clarity and subsequent resources. She is excited to broaden her clinical experience by completing a lifespan residency in clinical neuropsychology at HNS.

Dr. Melissa Estrada earned her bachelor’s degree in psychology with a minor in Spanish from Arizona State University. She obtained her Master’s degree and doctoral degree from the University of Northern Colorado. She completed her pre-doctoral internship at a K-8 school in Arizona. 

While Dr. Estrada’s early training focused on advocating for students and families in the school setting, her training included providing therapy and neuropsychology assessment services in a pediatric hospital setting. She has experience in the assessment of ADHD, learning and intellectual disabilities, emotional disabilities, and developmental delays. Clinically, she has experience in the assessment of brain tumors, congenital heart disease, leukemia and other blood cancers. 

Because of her background in the school setting, Dr. Estrada is able to provide resources and recommendations that are feasible for the school setting. Additionally, Dr. Estrada is fluent in Spanish and has pursued various opportunities that have allowed her to grow as a bilingual neuropsychologist. She is excited to pursue a lifespan neuropsychology residency at Horizon Neuropsychology Services!

Nicole Liedike earned her bachelor’s degree in psychology from Wilmington University and her master’s and doctorate degrees in clinical psychology from The Chicago School of Professional Psychology. She completed her pre-doctoral internship in clinical psychology at a private practice in Colorado Springs, CO that primarily focused on neurodevelopmental, psychological, and neuropsychological assessments with populations ranging from 18 months of age in older adulthood.

Nicole’s training experience prior to her graduate career was in acute psychiatric hospitalization care working with adolescents, adults, older adults, and dual diagnosis populations. During her graduate career, she has worked with preschool-aged children in a school setting, and with adults and older adults in private psychological practice and outpatient medical settings providing therapeutic support and conducting psychological and neuropsychological evaluations. Her future career goal is to become a board-certified neuropsychologist focusing on assessment for traumatic brain injury and neurodegeneration populations. With her passion for neuropsychological assessment, Nicole is enthusiastic about completing her lifespan residency in clinical neuropsychology at Horizon Neuropsychological Services.

Madison recently earned her bachelor's degree from Colorado State University in behavioral and cognitive neuroscience and has previous experience shadowing the pediatric neurosurgeons and PAs at Wolfson Children's Hospital in Jacksonville, Florida.

Madison is a very friendly individual who has worked with kids over the course of her teen years and is excited to interact with youth of all ages as they visit the Horizon office. She hopes she can be another friendly face that welcomes patients into the office and, in one way or another, bring comfort to families as they come in and get the help they deserve.

Payson earned her Bachelor’s degree from Santa Clara University, studying Psychology, Public Health, and Biology. Payson worked as a psychology research assistant for two research labs throughout college. She also has clinical experience as a Behavioral Health Technician working with adults at a residential treatment program in the Bay Area. Payson hopes to one day pursue a PsyD to become a practicing clinical neuropsychologist.

Penny earned her Bachelor’s in Social Work with a Concentration in Human Services from the State University of New York at New Paltz. In addition, she holds a Bachelor of Science in Nutrition and an Associate’s Degree in Liberal Arts.

Penny has worked with children and families in various settings as a case aide, family group conference facilitator, and office manager. Penny's professional expertise as an administrative support and direct care provider, positive energy, and warm smile are invaluable to the Horizon Neuro team and the families we serve.

Savannah earned her bachelor's degree from Colorado State University in health and exercise science with a concentration in sports medicine. She has clinical experience as a Behavioral Technician working with kids on the spectrum.

During her time as a clinician, Savannah has discovered her more profound passion for medicine and is pursuing a future as a Physician Assistant (PA). She hopes to work in the emergency room, where her passion for helping others will impact various patients.

Matt Mullens specializes in software development and system architecture. He is responsible for various technical projects at Horizon Neuro and is applying his experience in a variety of industries across a wide range of technologies to help Horizon Neuro operate more efficiently. He has a deep passion for machine learning and data science and how that applies to the healthcare space. Matt is looking forward to helping Horizon Neuro deliver the best care possible to patients and their families.