The neuroimaging signal is a linear sum of neurally distinct stimulus- and task-related components

• Published in: Nature neuroscience Vol. 15; no. 9; pp. 1298 - 1306
• Main Authors: Cardoso, Mariana M B, Sirotin, Yevgeniy B, Lima, Bruss, Glushenkova, Elena, Das, Aniruddha
• Format: Journal Article
• Language: English
• Published: New York Nature Publishing Group US 01.09.2012; Nature Publishing Group
• Subjects: 631/1647/245; 631/378/1697; 631/378/2591/2595; Algorithms; Animal Genetics and Genomics; Animals; Behavioral Sciences; Biological Techniques; Biomedical and Life Sciences; Biomedicine; Cerebrovascular Circulation - physiology; Conditioning, Operant; Cues; Darkness; Electrodes; Electrodes, Implanted; Electrophysiological Phenomena; Evoked Potentials - physiology; Fixation, Ocular - physiology; Hemodynamics; Image Processing, Computer-Assisted; Linear Models; Macaca mulatta; Macaques; Magnetic resonance imaging; Medical imaging; Nervous System Physiological Phenomena; Neurobiology; Neuroimaging; Neuroimaging - methods; Neurophysiology; Neurosciences; Photic Stimulation; Physiological aspects; Visual cortex; Visual Cortex - physiology; United States; New York; United States > US; Portugal
• ISSN: 1097-6256; 1546-1726
• DOI: 10.1038/nn.3170

Using simultaneous electrophysiological and optical imaging, this study finds that it is the linear summation of stimulus-independent trial-related and stimulus-dependent components that yield the signal seen in neuroimaging studies. However, the trial-related component, which does not correlate with neural spiking or LFPs, can account for over half of the neuroimaging signal, suggesting that it is crucial to take this component into account when interpreting neuroimaging studies. Neuroimaging (for example, functional magnetic resonance imaging) signals are taken as a uniform proxy for local neural activity. By simultaneously recording electrode and neuroimaging (intrinsic optical imaging) signals in alert, task-engaged macaque visual cortex, we recently observed a large anticipatory trial-related neuroimaging signal that was poorly related to local spiking or field potentials. We used these same techniques to study the interactions of this trial-related signal with stimulus-evoked responses over the full range of stimulus intensities, including total darkness. We found that the two signals could be separated, and added linearly over this full range. The stimulus-evoked component was related linearly to local spiking and, consequently, could be used to obtain precise and reliable estimates of local neural activity. The trial-related signal likely has a distinct neural mechanism, however, and failure to account for it properly could lead to substantial errors when estimating local neural spiking from the neuroimaging signal.