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Abstract

The majority of functional brain imaging studies rely on task induced hemodynamic responses to infer the underlying changes in neuronal activity. Characterizing the relationship between hemodynamic responses and locally measured neuronal activity is crucial for correct interpretation of functional MRI data. Most previous studies on this relationship have used anesthetized preparations with possible confounding effects of anesthesia. This study is aimed at characterizing the local neuronal correlates of Blood Oxygenation Level Dependent response to short presentation of visual stimuli in alert fixating monkey visual area V1.
Monkeys were trained to stay still throughout trials lasting 20 s, within which they fixated for 6 s and were presented with a stimulus for 4 s. Gradient Echo and Spin Echo functional MRI was performed using a 7 T vertical bore magnet and a surface RF coil positioned around a recording chamber (2 segments, TE 19 and 40 ms for Gradient Echo and Spin Echo respectively, resolution 1×1×2 mm, acquisition time 1 s / volume). Interleaved between functional MRI scans, electrophysiological signals were recorded using identical paradigms. The BOLD signal was sampled from a region of interest (6×6×2 mm) around the electrode in V1. Data will be shown on the coupling of different bands of the neuronal signal to the BOLD response, and on the relationship between the locally measured visual evoked response and BOLD response.