期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 104, 期 51, 页码 20546-20551出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.0709515104
关键词
awake; behavior; calibrated fMRI; glucose; glutamate
资金
- NIDCD NIH HHS [R01 DC003710, R01 DC-003710] Funding Source: Medline
- NIMH NIH HHS [R01 MH-067528, R01 MH067528] Funding Source: Medline
- NINDS NIH HHS [R01 NS049307, P30 NS-52519, P30 NS052519] Funding Source: Medline
Energetics of resting and evoked fMRI signals were related to localized ensemble firing rates (nu) measured by electrophysiology in rats. Two different unstimulated, or baseline, states were established by anesthesia. Halothane and a-chloralose established baseline states of high and low energy, respectively, in which forepaw stimulation excited the contralateral primary somatosensory cortex (S1). With alpha-chloralose, forepaw stimulation induced strong and reproducible fMRI activations in the contralateral S1, where the ensemble firing was dominated by slow signaling neurons (SSN; nu range of 1-13 Hz). Under halothane, weaker and less reproducible fMRI activations were observed in the contralateral S1 and elsewhere in the cortex, but ensemble activity in S1 was dominated by rapid signaling neurons (RSN; nu range of 13-40 Hz). For both baseline states, the RSN activity (i.e., higher frequencies, including the gamma band) did not vary upon stimulation, whereas the SSN activity (i.e., a band and lower frequencies) did change. In the high energy baseline state, a large majority of total oxidative energy [cerebral metabolic rate of oxygen consumption (CMRO2)] was devoted to RSN activity, whereas in the low energy baseline state, it was roughly divided between SSN and RSN activities. We hypothesize that in the high energy baseline state, the evoked changes in fMRI activation in areas beyond S1 are supported by rich intracortical interactions represented by RSN. We discuss implications for interpreting fMRI data where stimulus-specific Delta CMRO2 is generally small compared with baseline CMRO2.
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