Emily D. Grossman, PhD - US grants

Humans are remarkably adept at recognizing the actions of others, even based on movement patterns alone. This ability is most dramatically shown by "point-light biological motion" animations, in which just a few dots are visible, placed at joints or other critical places. It is often easy to recognize which action is being performed, what the actor's emotional state is, and even who the person is. Although we know this information is available, little is known as to how it is perceived. This is particularly interesting because visual motion and form cues are assumed to be processed in parallel and independent streams, yet these two types of information have to be combined for point-light displays to be meaningful. Neuroimaging studies in humans have further linked biological motion perception to a regions of the brain called the superior temporal sulcus, which seems to be involved in many complex processes including social perception. With the support of the National Science Foundation, Dr. Emily Grossman at the University of California Irvine will investigate the perceptual means for the recognition of biological motion, and the brain systems involved. The perception tests will use a novel behavioral technique in which perceivers make yes/no decisions about biological motion animations viewed on a computer screen. The brain work will use functional Magnetic Resonance Imaging (fMRI) to test specific hypotheses of the combination of form and motion cues in biological motion perception. These experiments will also measure the tuning properties of brain regions supporting biological motion perception, something that has already been achieved in monkeys but not yet in humans.

Theories of biological motion draw from a number of scientific domains, including research in visual perception, social perception, action understanding and motor imitation (the "mirror neuron" system). Results from the present project will influence thinking in all of these domains. The work in this proposal also involves hands-on research experience for undergraduate and graduate students, including the design and analysis of neuroimaging studies. Because UC Irvine and Dr. Grossman's laboratory both have a historical record of recruiting an ethnically diverse student population, these projects provide the opportunity to promote science among under-represented minorities. Finally, as part of the pedagogical activities in this CAREER proposal, this project will support the development of a new Neuroimaging Laboratory course in which students are trained in the practical skills necessary for brain imaging data analysis, a skill highly desirable in the upcoming cohort of cognitive neuroscientists.

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Humans are social creatures with extensive neural systems dedicated to the skills required to navigate interactions with others. This includes decoding the actions of others to infer goals and intentions, and planning our own actions that are appropriate for the current context. Brain regions that support these skills are anatomically dispersed in the four lobes of the brain, organized as a network with communication via long-range white matter connections. One key hub of this network is the posterior superior temporal sulcus (pSTS). The work is this proposal will address an important outstanding question: how the long-range connections supporting action understanding are organized, and the nature of the information that is integrated through these connections. This work will combine structural and functional brain imaging to identify anatomical pathways connecting systems supporting action recognition, with particular attention to pathways through the pSTS, and will use computational statistical analyses to characterize the neural information that is carried through those pathways. This problem is of urgent scientific and clinical relevance: Neuroscience increasingly recognizes that brain regions do not function in isolation, but instead reflect the integration of neural signaling from many cortical sources. The work in this proposal seeks to advance brain science by explicitly modeling these sources in a targeted cortical network. The action recognition network holds additional importance to the public, as some neurodevelopmental disorders (such as autism) are linked to atypical development of the pSTS and poor communication within this neural network. Therefore the outcomes from this work may be critical for developing new clinical tools for diagnosis and interventions for these disorders. Implementing the work in this grant will also support the full engagement and promotion of under-represented and first-generation of young scientists training in neuroscientific research.

The problem of how information is communicated and structured within the action recognition network is an important one. Many competing scientific models exist as to the functional specialization of the posterior superior temporal sulcus and connected brain regions within the action recognition network. New empirical data and analytical techniques are required to advance these theoretical models. A key to understanding information structure within the pSTS and the larger action recognition network is to evaluate the sources integrated within the neural signals, which reflect both sensory-driven perceptual analysis of social cues and the top-down goal-directed signals modulate influences. The work in this proposal will combine innovative experimental design with advanced multivariate statistical analyses to extract structure from the rich regional brain activation response, and will decompose the contribution of sensory-driven and top-down signals on neural tuning. At the same time, one must consider where top-down goal-directed signals originate and the structural pathways by which they are transmitted. The work in this proposal is innovative in that it will characterize the network architecture, both structurally and functionally, using a combination of tools rarely implemented despite their clear complementarity.