V1 BOLD fluctuations are influenced by global stimulus properties – A high-resolution fMRI study

Poster No:

W468 

Submission Type:

Abstract Submission 

Authors:

Shahin Nasr1,2, David Kleinfeld3,4, Jonathan Polimeni2,1

Institutions:

1Harvard Medical School, Boston, MA, 2A. A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, 3Department of Physics, UC San Diego, La Jolla, CA, 4Section of Neurobiology, UC San Diego, La Jolla, CA

E-Poster

Introduction:

Neurons within the primary visual area (V1) generally have small receptive fields and respond to local stimulus features (Hubel and Wiesel, 1968, Tootell et al., 1998). But single-cell studies have shown that global stimulus properties, e.g. objecthood, that rely on information from regions outside neurons receptive field, can influence the magnitude of the V1 response and the level of synchronization between V1 neurons (Gray et al., 1989, Lamme and Spekreijse, 1998). In humans, attention to local compared to global configuration (GC) decreases cross-hemispheres synchronization of gamma-band EEG in higher-level cortical areas (Rose et al., 2005). However, due to poor spatial resolution of EEG, it is not clear if this effect extends to lower-level areas such as V1. To test if GC influences the level of correlation between spontaneous activity across distant V1 sub-regions, we used high-resolution fMRI to examine synchronization across a large region of human cortex.

Methods:

Two separate groups of 11 human subjects (6 females), aged 23–31 and 20–42 y.o., participated in Experiments 1 and 2 respectively. Written informed consent was obtained prior to the experiments.
In Exp. 1, 4 static unfilled ellipses were presented for ~270 s. Across runs, focal points on two opposite sides of the horizontal/vertical meridians were contained either within the same ellipse (Fig. 1A) or in different ellipses (Fig. 1B). In Exp. 2, subjects viewed similar shapes but here, either the focal points (Fig. 1C–D) or the full ellipses (Fig. 1E–F) were filled with random-noise patterns that updated every 0.14 s. These patterns added local discontinuities, independent from the GC. The sequence of runs was counterbalanced across subjects.
FMRI was measured using standard 2D-EPI (1.2 mm iso, TR=3 s, R=4) in a 3T TimTrio Siemens scanner with the vendor-supplied 32ch coil array. For each subject, the portion of V1 that represented the area around focal points (r<2°), was localized retinotopically (Fig. 2A–D). The level of correlation between the fMRI fluctuations measured within these regions of interest (ROIs) was calculated using a Pearson test of correlation.
Supporting Image: Fig_1.jpg
 

Results:

We hypothesized that the elliptical shapes define an "object" boundary and tested whether the location of these boundaries influences correlation between the fMRI fluctuations measured within distant ROIs.
Results of Exp. 1 showed that cross-hemispheres correlation was stronger when ROIs represented focal points within the same rather than different objects (Fig. 2E–F). An application of 3-way repeated measures ANOVA, i.e., focal-points-grouping (FPG) (same vs. different objects), ROI-side (cross- vs. within-hemispheres) and cortical depth (deep vs. superficial)) to the level of correlation between adjacent ROIs yielded a significant effect of FPG × ROI-side (p<0.01) along with a higher correlation within superficial compare to deep cortex (p=0.04). This result is likely due to the stronger BOLD response in superficial depths (Polimeni et al., 2010).
Results of Exp. 2 ruled out the possibility that the findings of Exp. 1 is due to local discontinuity caused by object boundaries rather than the GC. Application of a 4-way repeated measures ANOVA (ellipse-type (fully vs. partially filled), FPG, ROI-side and cortical depth) did not show any significant effect of ellipse-type (p=0.33). Rather, it showed a significant FPG × ROI-side (p=0.03), mostly confined superficial depths, as reflect on the significant FPG × cortical level interaction (p<0.01). Thus, in both experiments, GC affected cross-hemispheres correlations measured within superficial depths.
Supporting Image: Fig_2.jpg
 

Conclusions:

Global configuration, even when controlled by fine features such as thin boundaries, can systematically influence the correlation between spontaneous fMRI measured within distant V1 sub-regions. These results suggest that more information is likely embedded in evoked fMRI response when temporal dynamics is also taken into consideration (Polimeni and Wald, 2018).

Imaging Methods:

BOLD fMRI 1

Modeling and Analysis Methods:

Task-Independent and Resting-State Analysis

Perception and Attention:

Perception: Visual 2

Keywords:

Cortex
Cortical Layers
FUNCTIONAL MRI
NORMAL HUMAN
Vision
Other - Stimulus Global Configuration, Spontaneous FMRI Activity, Primary Visual Cortex, Synchronization

1|2Indicates the priority used for review

My abstract is being submitted as a Software Demonstration.

No

Please indicate below if your study was a "resting state" or "task-activation” study.

Resting state
Task-activation

Healthy subjects only or patients (note that patient studies may also involve healthy subjects):

Healthy subjects

Are you Internal Review Board (IRB) certified? Please note: Failure to have IRB, if applicable will lead to automatic rejection of abstract.

Yes

Was any human subjects research approved by the relevant Institutional Review Board or ethics panel? NOTE: Any human subjects studies without IRB approval will be automatically rejected.

Yes

Was any animal research approved by the relevant IACUC or other animal research panel? NOTE: Any animal studies without IACUC approval will be automatically rejected.

Not applicable

Please indicate which methods were used in your research:

Functional MRI

For human MRI, what field strength scanner do you use?

3.0T

Which processing packages did you use for your study?

Free Surfer

Provide references using author date format

Gray CM, König P, Engel AK, Singer W (1989) Oscillatory responses in cat visual cortex exhibit inter-columnar synchronization which reflects global stimulus properties. Nature 338:334.
Hinds OP, Rajendran N, Polimeni JR, Augustinack JC, Wiggins G, Wald LL, Diana Rosas H, Potthast A, Schwartz EL, Fischl B (2008) Accurate prediction of V1 location from cortical folds in a surface coordinate system. Neuroimage 39:1585-1599.
Hubel DH, Wiesel TN (1968) Receptive fields and functional architecture of monkey striate cortex. The Journal of physiology 195:215-243.
Lamme VA, Spekreijse H (1998) Neuronal synchrony does not represent texture segregation. Nature 396:362.
Polimeni JR, Fischl B, Greve DN, Wald LL (2010) Laminar analysis of 7T BOLD using an imposed spatial activation pattern in human V1. Neuroimage 52:1334-1346.
Polimeni JR, Wald LL (2018) Magnetic Resonance Imaging technology—bridging the gap between noninvasive human imaging and optical microscopy. Current opinion in neurobiology 50:250-260.
Rose M, Sommer T, Büchel C (2005) Integration of local features to a global percept by neural coupling. Cerebral Cortex 16:1522-1528.
Tootell RB, Hadjikhani NK, Vanduffel W, Liu AK, Mendola JD, Sereno MI, Dale AM (1998) Functional analysis of primary visual cortex (V1) in humans. Proceedings of the National Academy of Sciences 95:811-817.