The focus of this issue of The ASHA Leader is translational neuroscience. The enterprise of neuroscience is to observe, manipulate, measure, and infer how the brain gets its job done. Translational research is the application of these scientific methods and findings to the improvement of the human condition. Historically, foundational knowledge in the discipline emerged from behavioral, acoustic, and physiologic studies of individuals with and without communication disorders, physiologic and cellular studies of animals, as well as the lesion method, which considers a patient's profile of impaired and preserved abilities with respect to regions of brain damage to draw inferences concerning brain-behavior relationships. Over the past 15 years, an explosion of research has addressed the relationship between neural and cognitive activity, mostly using functional magnetic resonance imaging (fMRI), but also positron emission tomography (PET), single photon emission computed tomography (SPECT), electroencephalography (EEG), and magnetoencephalography (MEG). Unlike the behavioral, cellular or lesion approaches, functional neuroimaging yields information about neural activity in multiple brain regions simultaneously, making it ideal for investigating the neural bases of complex cognitive activities like speech, language, and hearing.
In the feature article, "Neuroimaging and Cochlear Implants: A Look at How the Brain Hears," Emily Tobey and Michael Devous address important advances concerning how the brains of individuals with long-standing auditory deprivation secondary to sensorineural hearing loss learn to process speech after cochlear implantation. They conducted a SPECT study to investigate the effects of audiologic/aural rehabilitation in a group of older individuals with cochlear implants. Of particular significance is their finding that pairing behavioral intervention techniques with the administration of pharmacological agents (e.g., d-amphetamine) can sometimes result in enhanced outcomes. This article on page 6 adds further evidence that experience-related plasticity occurs throughout the lifespan.
On page 10, Hermann Ackermann's feature article, "Glimpses into the Speaking Brain," describes how our understanding of speech production has been derived primarily from perceptual, acoustic, physiologic, psycholinguistic, and lesion methods. These approaches have generated the theoretical infrastructure of the discipline and have helped to identify some of the most critical factors in the design of neuroimaging experiments. Factors such as syllable length and complexity, and rate of speech are critical to consider in designing neuroimaging experiments of spoken language production as they affect both the magnitude and regions of neural activation. Of course, most—if not all—investigations of communicative behaviors contribute to the neuroscience enterprise, since discovery of the neural bases of speech, language, and hearing requires well-specified theories of the underlying cognitive physiologic processes.
As a complex neural model of communication is emerging, another area of translational neuroscience is forging new methods to help persons with impaired speech-motor control. In the article beginning on page 14, "Brain-Computer Interface: Transforming Electrical Activity into Communication," Yael Arbel describes an emerging technology that allows people with impaired motor control to communicate using EEG signals to control external communication devices. This article illustrates the significance of translational neuroscience for people with severe impairments and foreshadows new avenues for alternative communication.
Lyn Turkstra, in "Research Leads to New Intervention Approaches for Pragmatic Communication Disorders," contrasts the roles of domain-specific and domain-general cognitive processes in the article that opens on page 16. Based on data derived primarily from the lesion method, circumscribed neural regions have been associated with domain-specific functions (e.g., Broca's area with language processing). Other cognitive domains, such as attention and working memory, have been hypothesized to have a more distributed neural circuitry. With the advent of neuroimaging, it is becoming clear that most neural regions support multiple functions (i.e., multiple cognitive domains can activate a single circumscribed neural region) and that domain-specific functions, like language, typically activate multiple areas across widespread regions of the brain. Turkstra addresses the blurring of this distinction by contrasting the social cognitive and language problems of adolescents with TBI to those with specific language impairment.
Lasting changes in behavior have long been presumed to reflect alterations in the patterns of brain activity. The term neural plasticity describes changes in neural activity that underlie changes in function at the behavioral level. Neuroimaging studies of experience-dependent plasticity, as well as injury-related plasticity, reveal dramatic changes in the patterns of neural activity as individuals acquire skill or recover function. This topic is addressed in Sally and Bennett Shaywitz's article on "The Neurobiology of Reading and Dyslexia," which begins on page 20. They describe exciting advances in understanding the neurobiological underpinnings of reading and neural changes associated with reading intervention for dyslexia.
Advances in translational neuroscience will continue to improve our ability to diagnose, improve treatment outcomes, and to understand the neural mechanisms supporting the development, use, and rehabilitation of speech, language, and hearing. I hope you enjoy this focused coverage on a topic of increasing importance in communication sciences and disorders.