Dr. Jed Meltzer is a cognitive neuroscientist specializing in language, with research interests both in the basic science of language processing from a neurobiological perspective, and in applications to the diagnosis and treatment of acquired neurological disorders such as stroke and dementia.
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Much of the lab’s work has dealt with neural oscillations measured with electroencephalography (EEG) and magnetoencephalography (MEG). These tools offer the ability to track the engagement of various brain networks at high temporal resolution, allowing us to assess the contributions of multiple neural pathways to the processes of language comprehension and production. Furthermore, the electrophysiological signals measured by these technologies are rich in information to address advanced questions beyond “where and when” information is processed in the brain. Specific areas of research interest include:
1) Interhemispheric interactions for language and motor functions. The human brain is functionally asymmetrical, with the left hemisphere playing a dominant role in language and also hand movement, and the right hemisphere exhibiting specialization for spatial processing. However, interaction between the two hemispheres is an essential part of everday functioning, and seems to play an increasingly important role in compensating for functional declines occurring in neurological disease, and also in the normal process of aging. Interhemispheric interaction has been characterized as either cooperative or competitive, and understanding how both kinds of interactions can happen simultaneously is essential to harnessing the therapeutic potential of modulating them. Our laboratory conducts behavioural and neuroimaging (MEG, fMRI) studies of tasks involving interhemispheric transfer of information.
2) Quantifying and modulating dysfunctional neural activity. Although structural brain damage (i.e. death of neurons) is a key feature of both stroke and dementia, many of the behavioural deficits in these disorders may be attributable to subtler forms of damage and dysfunction that are potentially reversible. In recent work, our laboratory has pioneered analyses of resting-state MEG dynamics to localize and quantify dysfunctional activity in brain areas that are affected by disease but still structurally intact. Ongoing work tests whether such dysfunction may be reversible using approaches such as brain stimulation and drugs, resulting in therapeutic improvements. Current brain stimulation experiments involve transcranial magnetic stimulation (TMS) and high-definition transcranial direct current stimulation (HD-TDCS) of areas implicated in language and motor deficits.
3) Harnessing technological advances in language assessment and rehabilitation. Advances in computational linguistics are proving invaluable in both basic and cognitive neuroscience. The use of software to select stimuli for language experiments on quantitative criteria is now commonplace, but many other transformations are underway. For the assessment and treatment of dementia and stroke, our studies used automated analysis of naturalistic language samples to identify patterns of language change associated with normal aging and neurological impariment. These measures, along with the brain imaging measures discussed above, offer the potential to evaluate novel interventions more sensitively, to test whether a given intervention is having a desirable effect in a given individual, early in the intervention process. Additional work concerns the use of advanced technological tools as therapeutic aids in neurorehabilitation, including adult-oriented computer training software incorporating spaced repetition, and speech therapy delivered remotely through telerehabilitation software.