Andrew Dimitrijevic

Research Synopsis

Research Divisions: Brain Research and Integrated Neurophysiology

Research Interests: Research is directed towards neurophysiology of hearing difficulties in people who have cochlear implants using electroencephalography (EEG). Current projects include: speech and music perception, neural plasticity associated with hearing loss and restoration, working memory and measures of cognitive load, the use of mobile EEG imaging technology to monitor real-world brain function.

Keywords: Speech perception, Cochlear Implant, Electroencephalography (EEG), Brain Oscillations, Mobile Brain Imaging.

Detailed Description: High density EEG is used to map out brain regions underlying listening disorders. One focus is on EEG signatures of the “cocktail party” where a listener needs to focus attention on a single talker amongst many competing voices. These studies have shown that brain oscillations, in particular the alpha band, is highly correlated to attention and self-perceived “listening effort”. We also examine brain processes associated with music perception and how different instruments are encoded separately when listening an entire music piece consisting of multiple instruments. A big focus of the lab is mobile EEG imaging. This field of study goes outside the lab and into the real-world. These studies aim to characterize brain responses while a listener follows a conversation in a natural setting. Other areas of research include: cross-modal neuroplasticity associated with hearing loss and recovery with a cochlear implant and the effects of hearing loss on working memory.

Collaborators: Drs. Darren Kadis and Karen Gordon

METHODS USED

Procedures: EEG, Electrophysiology, in-vivo electrophysiology, in-vivo recording of local field potentials, micro and macrostimulation of periphera nerves and central brain structures, stereotaxic brain surgery

EQUIPMENT USED

EEG systems (Neuroscan, BrainProducts, mBrainTrain Smarting Mobile), Matlab: EEGLAB, FieldTrip. Brain Electrical Source Analysis (BESA). Pupil Labs Eye Tracker.

Recent Publications

Han JH, Dimitrijevic A. Acoustic Change Responses to Amplitude Modulation in Cochlear Implant users: Relationships to Speech Perception Frontiers in Neuroscience 2020

Dimitrijevic A, Smith ML, Kadis DS, Moore DR. Neural indices of listening effort in noisy environments. Scientific Reports. 2019.

Dimitrijevic A, Smith ML, Kadis DS, Moore DR. Cortical Alpha Oscillations Predict Speech Intelligibility. Frontiers in human neuroscience. 2017; 11:88.

Dimitrijevic A, Alsamri J, John MS, Purcell D, George S, Zeng FG. Human Envelope Following Responses to Amplitude Modulation: Effects of Aging and Modulation Depth. Ear and hearing. 2016; 37(5):e322-35.

Han JH, Zhang F, Kadis DS, Houston LM, Samy RN, Smith ML, Dimitrijevic A. Auditory cortical activity to different voice onset times in cochlear implant users. Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology. 2016; 127(2):1603-1617.

Han JH, Dimitrijevic A. Acoustic change responses to amplitude modulation: a method to quantify cortical temporal processing and hemispheric asymmetry. Frontiers in Neuroscience. 2015; 9:38.

Appointments

Primary: Medicine, Otolaryngology, Head and Neck Surgery
Cross-Appointed to Psychology
Cross-Appointed to Physiology
Research Director of the Cochlear Implant Program at Sunnybrook Health Sciences Centre

Graduate Students

Student Name: Priyanka Prince
Area of Research: MSc Candidate
Student Name: Bowen Xiu
Area of Research: MSc Candidate