The ability to engage in mathematical thought is central to an individual's ability to thrive modern society. This project will investigate the neural basis of this ability by studying individuals with brain injury due to stroke. The goal is to understand how and where localized brain injury leads to impairments in math skills, thereby revealing the parts of the brain that are crucial for normal function. The work will examine the ability to make judgments about magnitude, a fundamental skill thought to rest upon an innate approximate number system, as well the abilities that rest upon cultural transmission of symbol systems for number (e.g., through classroom instruction). The relationship between these different types of skills, and their neural substrates, remains a point of significant debate. To make progress, stroke survivors will participate in the study. All participants will complete a magnetic resonance imaging (MRI) session to acquire images of their brain, and a set of behavioral tasks probing sensory, motor, language, general cognitive, and mathematical abilities. A series of statistical analyses will combine the brain and behavioral data, in order to identify sites of brain injury that are associated with: (1) specific impairments in approximate number representation and estimation, (2) specific impairments in precise number representation and calculation, and (3) impairments in math ability that are secondary to impairments in language or more general cognitive functions. The work should help to adjudicate between theories of math ability and inform future studies examining math learning and intervention strategies for struggling learners. Importantly, the project will be deeply intertwined with undergraduate education and research mentorship. This will occur by embedding the data collection into an advanced undergraduate laboratory course and summer research internship programs, with graduate students contributing to the instruction. The result will be a multilayered, interdisciplinary, and diverse learning context for experiential science learning that will be of broad educational impact. Additionally, at the conclusion of the project the data (without identifying information) will be placed into an open repository for neuroscience research. No other dataset like this currently exists, and so this will give researchers access to unique and highly valuable dataset that will be suitable for addressing many research questions.
The lesion method involves studying patterns of preserved and impaired abilities in participants with brain damage. By combining information about patterns of behavioral performance and corresponding locations of neural damage, causal inferences can be drawn about the functions supported by particular brain regions and their white matter connections. This project will use the lesion method to investigate the relationship between different aspects of numeracy. The participants in the study will be ~ 160 individuals with left-hemisphere focal brain lesions, and an exploratory group of ~ 40 individuals with right-hemisphere lesions. All participants will complete a neuroimaging session to acquire structural and functional brain volumes, and a battery of behavioral tasks probing sensory, motor, general cognitive, linguistic, and mathematical abilities. Participants with evidence of impaired numeracy, or aphasia without intact numeracy, will be invited to return for a second behavioral-only session. This secondary assessment will involve a battery of tasks that will probe numeracy skills in greater depth, as well as general cognitive abilities relevant for skilled math performance. For the primary analyses, voxelwise lesion symptom mapping (VLSM) analyses will be used to test predictions derived from theoretical models of numeracy. These include the predictions that impairments in number comparison will be associated with damage to the inferior parietal sulcus, impairments in verbal fact retrieval will be associated with damage to the angular gyrus, and impairments in ordinality will be associated with damage to premotor cortex. Secondary analyses will permit more detailed examination of associations and dissociations across our numeracy, language, and cognitive tasks. This will include the use of principal components analysis and other data-driven techniques to discover patterns of impairments across our battery of tasks and test for associated loci of neural damage. Finally, exploratory analyses will probe for hemispheric differences in the representation of number.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
