fMRI Cortical Correlates of Spontaneous Eye Blinks in the Nonhuman Primate

Abstract

Eyeblinks are defined as a rapid closing and opening of the eyelid. Three types of blinks are defined: spontaneous, reflexive, and voluntary. Here, we focus on the cortical correlates of spontaneous blinks, using functional magnetic resonance imaging (fMRI) in the nonhuman primate. Our observations reveal an ensemble of cortical regions processing the somatosensory, proprioceptive, peripheral visual, and possibly nociceptive consequences of blinks. These observations indicate that spontaneous blinks have consequences on the brain beyond the visual cortex, possibly contaminating fMRI protocols that generate in the participants heterogeneous blink behaviors. This is especially the case when these protocols induce (nonunusual) eye fatigue and corneal dryness due to demanding fixation requirements, as is the case here. Importantly, no blink related activations were observed in the prefrontal and parietal blinks motor command areas nor in the prefrontal, parietal, and medial temporal blink suppression areas. This indicates that the absence of activation in these areas is not a signature of the absence of blink contamination in the data. While these observations increase our understanding of the neural bases of spontaneous blinks, they also strongly call for new criteria to identify whether fMRI recordings are contaminated by a heterogeneous blink behavior or not.

Time to wake up: Studying neurovascular coupling and brain-wide circuit function in the un-anesthetized animal

“…Any awake animal (or human) will engage in small spontaneous behaviors in the scanner, and these spontaneous behaviors could affect hemodynamic signals. Several behaviors known to cause or correlate with measurable changes in hemodynamic signals and functional connectivity include eye state (closed, open or fixating) (Patriat et al 2013; Chang et al, 2016), blink rate (Guipponi et al, 2014), and variations in respiration (Birn et al, 2009). In rodents, behaviors like whisking and sniffing (Moore et al, 2013) are analogous to eye movements in humans and primates (Kleinfeld et al, 2006; Crapse and Sommer, 2008; Ahissar and Assa, 2016), and these behaviors would be expected to have similar impacts on functional connectivity.…”

“…Going forward, monitoring of the relevant behavior(s) (Fig. 8 and (Guipponi et al, 2014; Chang et al, 2016; McGinley et al, 2015; O’Connor et al, 2010; Yang et al, 2016)) in animals is likely to play an important role in animal fMRI experiments, just as it has in human experiments (Richlan et al, 2014; Wang et al, 2016). The development of new techniques for analyzing behavioral data in other paradigms have undergone enormous advances in recent years (Gomez-Marin et al 2014), and it is likely that some of these approaches can be applied to the studies of more subtle behaviors.…”

Title: Time to wake up: Studying neurovascular coupling and brain-wide circuit function in the un-anesthetized animal

“…Any awake animal (or human) will engage in small spontaneous behaviors in the scanner, and these spontaneous behaviors could affect hemodynamic signals. Several behaviors known to cause or correlate with measurable changes in hemodynamic signals and functional connectivity include eye state (closed, open or fixating) (Patriat et al 2013;Chang et al, 2016), blink rate (Guipponi et al, 2014), and variations in respiration (Birn et al, 2009). In rodents, behaviors like whisking and sniffing are analogous to eye movements in humans and primates (Kleinfeld et al, 2006;Crapse and Sommer, 2008;Ahissar and Assa, 2016), and these behaviors would be expected to have similar impacts on functional connectivity.…”

“…These behavioral effects can be regressed out, as is currently done with physiological noise (Birn 2012;Murphy et al, 2013). Going forward, monitoring of the relevant behavior(s) (Figure 8 and (Guipponi et al, 2014;Chang et al, 2016;McGinley et al, 2015;O'Connor et al, 2010;Yang et al, 2016)) in animals is likely to play an important role in animal fMRI experiments, just as it has in human experiments (Richlan et al, 2014;Wang et al, 2016). The development of new techniques for analyzing behavioral data in other paradigms have undergone enormous advances in recent years (Gomez-Marin et al 2014), and it is likely that some of these approaches can be applied to the studies of more subtle behaviors.…”

Mapping (and modeling) physiological movements during EEG–fMRI recordings: The added value of the video acquired simultaneously

“…As concern blinking, there is a very wide literature regarding both humans and animal models (Chung et al, 2006;Guipponi et al, 2014;Hupé et al, 2012;van Koningsbruggen et al, 2012;Yoon et al, 2005). Eye-blinks are defined as a rapid closing and opening of the eyelid and three types of blinks are known: spontaneous, reflexive, and voluntary.…”