Analysis of time and space invariance of BOLD responses in the rat visual system

Christopher J. Bailey, Basavaraju G. Sanganahalli, Peter Herman, Hal Blumenfeld, Albert Gjedde, Fahmeed Hyder

Research output: Contribution to journalArticlepeer-review


Neuroimaging studies of functional magnetic resonance imaging (fMRI) and electrophysiology provide the linkage between neural activity and the blood oxygenation level-dependent (BOLD) response. Here, BOLD responses to light flashes were imaged at 11.7T and compared with neural recordings from superior colliculus (SC) and primary visual cortex (V1) in rat brain-regions with different basal blood flow and energy demand. Our goal was to assess neurovascular coupling in V1 and SC as reflected by temporal/spatial variances of impulse response functions (IRFs) and assess, if any, implications for general linear modeling (GLM) of BOLD responses. Light flashes induced high magnitude neural/BOLD responses reproducibly from both regions. However, neural/BOLD responses from SC and V1 were markedly different. SC signals followed the boxcar shape of the stimulation paradigm at all flash rates, whereas V1 signals were characterized by onset/offset transients that exhibited different flash rate dependencies. We find that IRFSC is generally time-invariant across wider flash rate range compared with IRFV1, whereas IRFSC and IRFV1 are both space invariant. These results illustrate the importance of measured neural signals for interpretation of fMRI by showing that GLM of BOLD responses may lead to misinterpretation of neural activity in some cases.

Original languageEnglish (US)
Pages (from-to)210-222
Number of pages13
JournalCerebral Cortex
Issue number1
StatePublished - Jan 2013
Externally publishedYes


  • calibrated fMRI
  • local field potential
  • multiunit activity
  • neuroenergetics
  • neurometabolic coupling
  • transfer function

ASJC Scopus subject areas

  • Cognitive Neuroscience
  • Cellular and Molecular Neuroscience


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