Relationship between saccadic eye movements and cortical activity as measured by fMRI: quantitative and qualitative aspects

Abstract

We investigated the quantitative relationship between saccadic activity (as reflected in frequency of occurrence and amplitude of saccades) and blood oxygenation level dependent (BOLD) changes in the cerebral cortex using functional magnetic resonance imaging (fMRI). Furthermore, we investigated quantitative changes in cortical activity associated with qualitative changes in the saccade task for comparable levels of saccadic activity. All experiments required the simultaneous acquisition of eye movement and fMRI data. For this purpose we used a new high-resolution limbus-tracking technique for recording eye movements in the magnetic resonance tomograph. In the first two experimental series we varied both frequency and amplitude of saccade stimuli (target jumps). In the third series we varied task difficulty; subjects performed either pro-saccades or anti-saccades. The brain volume investigated comprised the frontal and supplementary eye fields, parietal as well as striate cortex, and the motion sensitive area of the parieto-occipital cortex. All these regions showed saccade-related BOLD responses. The responses in these regions were highly correlated with saccade frequency, indicating that repeated processing of saccades is integrated over time in the BOLD response. In contrast, there was no comparable BOLD change with variation of saccade amplitude. This finding speaks for a topological rather than activity-dependent coding of saccade amplitudes in most cortical regions. In the experiments comparing pro- vs anti-saccades we found higher BOLD activation in the "anti" task than in the "pro" task. A comparison of saccade parameters revealed that saccade frequency and cumulative amplitude were comparable between the two tasks, whereas reaction times were longer in the "anti" task than the pro task. The latter finding is taken to indicate a more demanding cortical processing in the "anti" task than the "pro" task, which could explain the observed difference in BOLD activation. We hold that a quantitative analysis of saccade parameters (especially saccade frequency and latency) is important for the interpretation of the BOLD changes observed with visual stimuli in fMRI.

From inefficient to pop-out visual search in one week

“…Functional MRI was conducted with a 3-Tesla Siemens scanner (Allegra) using a whole-brain, echo-planer T2*-weighted imaging sequence. We identified regions of interest (ROIs) via separate functional localizer scans on each participant for early visual cortex with retinotopic mapping, 10 lateral occipital cortex 11 , intraparietal sulcus (IPS) 12 and the frontal/supplementary eye fields 13 . Image data were co-registered to high-resolution T1-weighted structural scans and analysis performed on the cortical surface with FreeSurfer 8,9 .…”

Current Trends of fMRI in Vision Science: A Review

“…It was suggested in a study looking at functional interactions between pro-and antisaccades that the presupplementary motor area (pre-SMA) coordinates with the FEF to maintain a controlled, preparatory set for task appropriate oculomotor execution . Saccade frequency and amplitude was varied (Kimmig et al, 2001) and high correlation between frequency and BOLD signal was found along with higher BOLD activation in antisaccades over prosaccades. Merriam et al (2001) found that comparison of visually guided saccades with fixation revealed activation in all three cortical eye fields: SEF, FEF, and PEF.…”

“…As a result of the increase in general fMRI studies, there has also been an increase of studies investigating many aspects of the vision science. These studies include normal eye movements such as optokinetic nystagmus (OKN) (Bense et al, 2006a;Bucher et al, 1997;Dieterich et al, 1998;2003;Kashou et al, 2006;Kashou, 2008;Kashou et al, 2010;Konen et al, 2005;Petit & Haxby, 1999;Schraa-Tam et al, 2008), saccades (Berman et al, 1999;Bodis-Wollner et al, 1997;Connolly et al, 2005;Cornelissen et al, 2002;Darby et al, 1996;Ettinger et al, 2008;Haller et al, 2008;Hayakawa et al, 2002;Kimmig et al, 2001;Konen et al, 2004;Luna et al, 1998;Merriam et al, 2001;Miller et al, 2005;Mort et al, 2003;Müri et al, 1996;Petit et al, 1997;Rosano et al, 2002), smooth pursuit (Barton et al, 1996;Berman et al, 1999;Freitag et al, 1998;Ohlendorf et al, 2010;Petit et al, 1997;Petit & Haxby, 1999;Rosano et al, 2002;Tanabe et al, 2002), and gaze (Andersson et al, 2007;Deutschländer et al, 2005). There have also been studies that look at varying aspects of visual perception such as: effect of age …”

Mechanisms underlying memory enhancement in humans

“…First, we performed a behavioral pre-fMRI experiment (Exp 4) similar to Exp 1 but with presentation duration of 250ms (frame-cue and picture presented simultaneously). Exp 4 simply ensured that robust memory enhancement for Go vs. NoGo stimuli is observed at this shorter presentation time, employed so as to minimize saccades, which not only lead to spurious BOLD effects (Kimmig et al, 2001) but also represent another type of action that increases LC activity in non-human primates (Kalwani et al, 2014). The results of Exp 4 once more replicated the main finding from Exp 1-3 (better memory for Go vs. NoGo items ( 21 = 2.26; p = 0.03; Figure 15A).…”