Introduction

The Human Brain Research Lab’s program focuses on understanding the spatiotemporal dynamics of brain functions that underlie many psychological phenomena involved in auditory and visual perceptions, attention, and memory. We use behavioural, eye-tracking, and electrophysiological (EEG & MEG) measures to study fundamental principles of these systems and how they develop. In collaboration with Dr. Jen Ryan at The Rotman Research Institute, we were the first to use combined eye-tracking and MEG to provided insight into the underlying neural substrates of errors in saccadic control (Herdman and Ryan, 2007). This has become an additional tool used in my laboratory. One arm of the HBR lab is located at the Down Syndrome Research Foundation which houses the only MEG facility in Canada west of Ontario and the other arm is located within the School of Audiology & Speech Science at the University of British Columbia. MEG is a non-invasive, direct measure of neural excitation in the human brain. It compliments many other neuroimaging methods. Importantly, MEG is particularly useful in scanning individuals who would be uncooperative with EEG electrodes being placed on the scalp or who are sensitive to the noisy and confined environments of fMRI scanners.

Auditory Selective Attention

Our work on children’s selective attention has provided  insights into the neural underpinnings of how socioeconomic gradients can alter the developing brain (D’Angiulli, Herdman, Stapells, and Hertzman, 2008). Our results demonstrated that children from low-socioeconomic families recruit a more frontally-mediated system to perform auditory selective attention, whereas children from high-socioeconomic families use more of an auditory-dependent network. Follow-up research showed that selective attention appears to mature from higher-to-lower stages of information processing (Herdman, 2011). This could have potential implications for understanding neural development of children with attention-deficit disorders. For instance, do social disparities influence the neural development of selective attention in children at-risk for an attention-deficit disorder? I’m currently collaborating on the GECKO project (an international NIH-funded project with researchers from University of British Columbia, University of California Berkeley, and Stanford University) to investigate genetic, epigenetic, and neurophysiological markers related to socioeconomic disparities and health vulnerabilities.

Visual Experience

The HBR lab’s basic scientific research investigates the neurodevelopment related to auditory and visual expertise and selective attention. We use reading development as a model of visual expertise and have shown that brain responses to unfamiliar pseudoletters are delayed in a right-hemispheric dominant object processing network (Herdman and Gaspar, in revision) with additional findings of greater gamma-band activity and delayed functional communication within this network for pseudoletter as compare to letters (Herdman, 2011; Herdman, in revision). The delayed event-related responses to pseudoletters than to letters is not apparent in children with dyslexia and results further show that dyslexic children engage networks that are more related to orthographic than phonologic processing; whereas typical readers do the opposite (Herdman, Gaspar, and Hoskyn, in revision). Collectively, we interpreted these results as indicators that experience with letters modifies the visual network by shifting it to be a faster, more holistic processor for letters than for pseudoletters in a similar manner to that shown to be used for processing faces as compared to inverted faces. Dyslexics likely have disruptions in such a network that do not allow for this holistic processor to become enhanced by experience; thus they do not show typical response patterns.

Cognition & Memory
Our work related to cognition and memory is a joint collaboration with Dr. Jen Ryan at the Rotman Research Institute. We published a paper that showed the spatiotemporal dynamics of cross-modal associative information retrieval for famous faces and names (Ryan, et al., 2008). We also published an article in Neuroimage that showed MEG was able to resolve activation in the medial temporal lobe using multiple complementary analytic approaches (Riggs, et al., 2009). We have ongoing projects that are investigating spatial memory consolidation and retrieval. Preliminary results have shown that spatial information encoding and retrieval might rely on the temporal order of objects viewed. This project has substantial impact on our understanding of how the brain codes spatial information, in that spatial information might be in the networks maintaining a temporal order of items viewed in a scene.

Methodology
In addition to our work in perceptual and cognitive areas, we also work as methodologists in electrophysiology and neuroimaging. We acquire and develop neuroimaging tools to help answer research questions from multiple disciplines. We’ve recently added functional connectivity analyses to my arsenal of tools in order to capture the exciting changes in neural dynamics. We are currently developing new functional connectivity measures useful for understanding neural network communication extracted from MEG data. Brain networks have similar properties to those in social networks and such methods used to study social networks are now being applied to neuroimaging data to provide deeper insights into unlocking the neural codes for perception and cognition. We are excited to be working in this area, which is rapidly receiving scientific interest from many researchers around the world.

Summary
In summary, the HBR lab’s research program uses multiple measures and methodologies to investigate perceptual and cognitive phenomena. We are particularly fascinated by how a brain functions and communicates across multiple dimensions (space, time, and frequency) and how such communication is altered by experience as a brain develops its abundant perceptual and cognitive abilities.