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Identification of degenerate neuronal systems based on intersubject variability
Uta Noppeney1, Will D Penny, Cathy J Price
1Wellcome Department of Imaging Neuroscience, University College London, 12 Queen Square, WC1 N3BG London, UK. uta.noppeney@tuebingen.mpg.de
Neuroimage
|November 23, 2005
Summary
Brain imaging reveals that cognitive tasks may engage distinct, overlapping neural systems. Researchers used Gaussian Mixture Modeling to identify two separate activation patterns in subjects performing a semantic decision task, challenging the assumption of a single common system.
Area of Science:
- Neuroscience
- Cognitive Neuroscience
- Brain Imaging
Background:
- Group studies often assume a single neural system underlies cognitive tasks, treating individual differences as noise.
- Intersubject variability may reflect engagement of different, yet functionally equivalent (degenerate), neuronal systems.
- This degeneracy could lead to multimodal distributions in brain activation patterns.
Purpose of the Study:
- To investigate whether intersubject variability in brain activation during a cognitive task arises from distinct degenerate neuronal systems.
- To explore the utility of Gaussian Mixture Modeling (GMM) and Bayesian model comparison for identifying such distinct systems.
Main Methods:
- Employed a crossmodal priming paradigm involving semantic decisions on auditory (environmental sounds, spoken names) and visual (pictures, written names) stimuli.
- Utilized functional Magnetic Resonance Imaging (fMRI) to measure brain activation.
- Applied Gaussian Mixture Modeling and Bayesian model comparison to analyze unexplained residuals in brain activation data.
Main Results:
- All subjects showed consistent activation in bilateral superior temporal gyri, left fusiform gyrus, and inferior frontal sulcus.
- Bayesian model comparison strongly favored a two-component Gaussian Mixture Model over a single-component model.
- Two distinct activation patterns emerged: one group showed additional activation in superior temporal sulci, right superior frontal, and central sulcus; the other group exhibited increased activation in striate cortex and right inferior parietal cortex.
Conclusions:
- The findings provide strong evidence for at least two overlapping degenerate neuronal systems supporting semantic decisions on auditory-visual compound stimuli.
- This challenges the traditional view of a single, uniform neural system for cognitive tasks and highlights the importance of considering intersubject variability.
- Degenerate neural systems offer a potential explanation for flexible and robust cognitive function.