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Neuronal population activity and functional imaging

Lookup NU author(s): Dr Jack Scannell, Professor Malcolm Young


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Human functional brain imaging detects blood flow changes that are thought to reflect the activity of neuronal populations and, thus, the responses of neurons that carry behaviourally relevant information. Since this relationship is poorly understood, we explored the link between the activity of single neurons and their neuronal population. The functional imaging results were in good agreement with levels of population activation predicted from the known effects of sensory stimulation, learning and attention on single cortical neurons. However, the nature of the relationship between population activation and single neuron firing was very surprising. Population activation was strongly influenced by those neurons firing at low rates and so was very sensitive to the baseline or 'spontaneous' firing rate. When neural representations were sparse and neurons were tuned to several stimulus dimensions, population activation was hardly influenced by the few neurons whose firing was most strongly modulated by the task or stimulus. Measures of population activation could miss changes in information processing given simultaneous changes in neurons' baseline firing, response modulation or tuning width. Factors that can modulate baseline firing, such as attention, may have a particularly large influence on population activation. The results have implications for the interpretation of functional imaging signals and for cross-calibration between different methods for measuring neuronal activity.

Publication metadata

Author(s): Scannell JW, Young MP

Publication type: Article

Publication status: Published

Journal: Proceedings of the Royal Society B: Biological Sciences

Year: 1999

Volume: 266

Issue: 1422

Pages: 875-881

Print publication date: 07/05/1999

ISSN (print): 0962-8436

ISSN (electronic):

Publisher: The Royal Society


DOI: 10.1098/rspb.1999.0718

PubMed id: 10380677


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