J. Devin McAuley - US grants

Neural mechanisms for assessing the temporal characteristics of events on a hundreds-of-milliseconds to seconds time scale are fundamental to human perception and performance. On this time scale, research supports at least two distinct mechanisms: an interval-based ('stopwatch') mechanism that records, stores and compares durations and a beat-based ('entrainment') mechanism that assesses the relative timing of events with respect to an internally-generated periodicity. One topic that has received relatively little research attention is the issue of individual differences. This project considers the possibility that individuals engage in beat-based and interval-based timing, but do so to different degrees. The general project aim is to identify and characterize factors mediating engagement of beat-based and interval-based timing mechanisms. Three lines of research will combine a novel sequence-timing paradigm that demonstrates robust individual differences, with a mathematical model that indexes the degree to which performance reflects beat-based judgments. Critical to the sequence-timing paradigm are stimulus sequences that yield opposite perceptions about sequence rate ('speeding up' versus 'slowing down') depending on whether individuals engage in beat-based or interval-based timing, respectively. The first line examines stimulus characteristics mediating beat-based timing. The second line assesses flexibility in timing mode, focusing on attention and task factors. The third line addresses developmental and training factors. A key contribution of the proposed modeling work is that it integrates two contrasting theories of timing within a single framework. Using this framework to clarify the degree to which individuals engage in beat-based timing will improve current limited understanding of individual differences in timing behavior and will help better characterize temporal processing deficits linked to neurological disorders. This project also will contribute to and strengthen the research and educational environment at the JP Scott Center for Neuroscience, Mind and Behavior at Bowling Green State University by providing unique opportunities for interdisciplinary training and collaborative research activities for undergraduate and graduate students.

Cognitive neuroscience research seeks to understand the basic brain mechanisms underlying cognitive and behavioral functions. While there are a variety of available research tools, the majority of these techniques are correlational, in that neural activity (or a proxy of neural activity) is measured while human subjects perform a task. Data from these techniques do not allow causal inference, which requires perturbation of the neural system. Transcranial Magnetic Stimulation (TMS) is currently the leading choice for neural perturbation in humans. With Major Research Instrumentation support from the National Science Foundation, Dr. McAuley and colleagues will purchase a TMS system to enhance research and training in cognitive neuroscience at Michigan State University. TMS can be used to produce temporary disruptions in neural activity or to stimulate the cortex in targeted brain regions. Recent developments in this technology allow image-guided TMS delivery, commonly referred to as neuronavigation. This method allows the TMS coil to be precisely positioned over a specified brain structure based on a person's neuroanatomical data obtained using magnetic resonance imaging (MRI) techniques. This capability is important because, although the structure of the brain is roughly similar across people, the exact anatomical location of neural structures can vary considerably. Targets for disruption/stimulation can be identified by selecting and highlighting the desired structure/locations with the brain. Image-guided (neuronavigated) TMS is quickly becoming a widely-used and standard technology in cognitive neuroscience research. The general value of this technology for cognitive neuroscience is that it is a non-invasive tool that can be coupled with functional and structural MRI data to make causal inferences about normal and disordered brain function that are not possible through fMRI/MRI studies alone.

The participating investigators are all active researchers in the cognitive neurosciences. The new instrumentation will transform Michigan State University's capability to conduct cutting-edge cognitive neuroscience studies that help unravel the neural bases of cognitive function in a diverse set of domains, including perception, attention, memory, cognitive control, and decision making. The acquisition will also more broadly contribute to university-wide neuroscience education and training initiatives at the graduate and undergraduate levels. As part of a new and popular undergraduate major in neuroscience, neuronavigated TMS will be included as one of the methods taught in a required core laboratory course that exposes students to a variety of different neuroscience methods. At the graduate level, the new instrumentation will strengthen introductory and advanced neuroimaging courses by providing new education and novel hands-on training and research opportunities. Michigan State University is a also leader in undergraduate research and training opportunities in STEM areas for women and underrepresented minorities, and the training opportunities created by the new instrumentation will interact synergistically with departmental, interdepartmental and university-wide initiatives. Opportunities for summer research experiences for high school students will be created through established contacts with science teachers in area high schools.

Understanding how humans comprehend speech is an unsolved and challenging problem, in part because factors such as different speakers, dialects, and speaking rates introduce a great deal of temporal and spectral variability into the speech signal. The focus of this research is on the influence of temporal context on perception of segments, syllables, and words. Results of the research may offer insights into treatment of disorders that involve disruption of speech rate (e.g., dysarthria, stuttering, Parkinson's disease, and aphasia), inform approaches to improve speech technology applications (e.g., enhanced automatic speech recognition, more natural sounding computer-generated speech), and lead to new discoveries related to brain mechanisms involved in understanding spoken language. The investigators will also involve students in the research, including those from a primarily undergraduate institution collaborating on the project.

The investigators will test different accounts of temporal phenomena in the perception of speech. They propose two interacting cognitive mechanisms controlling phenomena at lexical and phonetic levels, each driven by a different neural timing mechanism. The hypothesis is that effects of lexical rate primarily stem from top-down, speech-specific temporal expectancies, while phonetic rate effects originate in bottom-up, transient rhythmic expectations that are not specific to speech. This hypothesis will be assessed using psychoacoustic studies, non-invasive measures of brain activity, and theoretical modeling in order to identify the processing characteristics revealed by neural representations of temporal properties of speech.

DESCRIPTION (provided by applicant): The overarching goal of the proposed research is to identify the underlying causes of speech understanding problems in older adults. Older listeners, with or without significant hearing loss, often have much greater difficulty understanding speech in the presence of competing sounds than do younger listeners (CHABA, 1988; Dubno et al., 1984; Duquesnoy, 1983). For hearing-impaired listeners, differences in degree of hearing loss (or audibility) account for a large portion of the variance in listeners' ability to understand speech in the presence of competing sounds, but other factors (e.g., cognitive or central auditory factors) play an important role for both hearing-impaired and normal-hearing listeners (see Houtgast & Festin, 2008; Akeroyd, 2008; Humes, 2007; Humes & Dubno, 2010; Humes, Kidd, & Lentz, 2013). One promising hypothesis, which has received relatively little attention to date, is that effective speech understanding in the presence of competing sounds depends strongly on the ability to follow the temporal structure of an utterance and to accurately anticipate the timing of speech events through a process of attentional entrainment. According to the entrainment hypothesis (see Large & Jones, 1999; McAuley et al., 2006) the ability to attentionally track the temporal patterns of speech helps listeners to perceptually isolate and resolve the details of a single talker's speech by enhancing attention to speech events that correspond to a talker's temporal pattern. Moreover, accurate extrapolation of temporal patterns through inaudible or partially audible portions of an utterance is proposed to facilitate the integration of intermittent glimpses of speech by incorporating them in a common temporal framework. This general hypothesis will be investigated through a series of experiments that test the predictions of entrainment theory in a speech context, in combination with a new test battery that assesses individual differences in entrainment ability. A sample of 1000 young and older listeners with and without hearing loss will be tested, using shaped amplification to ensure audibility for hearing- impaired listeners. The project will employ a combination of behavioral and neurophysiological measures to determine how entrainment ability is related to speech understanding, while controlling for individual differences in basic auditory capabilities and cognitive abilities previously shown to be important for speech perception.

Music and language are both modes of human communication that convey meaning. Although there are many studies of how language acquires meaning, little is known about how music becomes meaningful. One hypothesis is that music acquires meaning in part because listeners impose narrative significance to musical events, translating abstract musical sequences into a story line as the notes unfold (a process known as narrative listening). A series of parallel experiments will be conducted that vary both the structural features of musical excerpts and the cultural background of the listener in order to disentangle questions about the role of nature and experience in the formation of musical meaning. Learning more about the mechanisms that underpin musical meaning fundamentally adds to our understanding of human communication and artistic expression, with the broader potential to lead to improved intercultural exchange. The work will also contribute new methodologies to probe the musical experiences of lay listeners across cultures, who often lack the musical vocabulary to describe their perceptions. By bridging science and the humanities, the project will provide STEM-based research training to students in the humanities and, in turn, expose students in the sciences to questions in the humanities that would benefit from development of novel scientific methodologies. The project's reach will be expanded by the development and dissemination of a new app for collecting crowd-sourced data via cell phone. Embedded GPS technology will allow the researchers to map patterns and variations in narrative listening across geography and cultures.

This project takes a theory-driven and cross-cultural approach to investigate the core factors that shape narrative listening to music. The investigators will obtain a normative set of cross-cultural data on narrative listening for a large sample of Western and Chinese musical excerpts from both American listeners with little exposure to Chinese music and from Chinese listeners will little exposure to Western music. If narrative listening arises from a fundamental tendency to make abstract stimuli concrete, then listeners will tend to ascribe agency to points in the music that violate their expectations in order to make sense of what they hear. If narrative listening arises from enculturation, people should be more likely to perceive narratives in music from their own culture than from a different culture. Within a culture, people should be more likely to perceive narratives for high topical-association music than for low topical-association music. Lastly, the investigators will examine the relationship between narrative listening and other well-studied aspects of music perception, providing novel insights about established phenomena and opening up new avenues of investigation.