Electrophysiology meets fMRI: Neural correlates of the startle reflex assessed by simultaneous EMG–fMRI data acquisition

Abstract

The startle reflex provides a unique tool for the investigation of sensorimotor gating and information processing. Simultaneous EMG-fMRI acquisition (i.e., online stimulation and recording in the MR environment) allows for the quantitative assessment of the neuronal correlates of the startle reflex and its modulations on a single trial level. This serves as the backbone for a startle response informed fMRI analysis, which is fed by data acquired in the same brain at the same time. We here present the first MR study using a single trial approach with simultaneous acquired EMG and fMRI data on the human startle response in 15 healthy young men. It investigates the neural correlates for isolated air puff startle pulses (PA), prepulse-pulse inhibition (PPI), and prepulse facilitation (PPF). We identified a common core network engaged by all three conditions (PA, PPI, and PPF), consisting of bilateral primary and secondary somatosensory cortices, right insula, right thalamus, right temporal pole, middle cingulate cortex, and cerebellum. The cerebellar vermis exhibits distinct activation patterns between the startle modifications. It is differentially activated with the highest amplitude for PPF, a lower activation for PA, and lowest for PPI. The orbital frontal cortex exhibits a differential activation pattern, not for the type of startle response but for the amplitude modification. For pulse alone it is close to zero; for PPI it is activated. This is in contrast to PPF where it shows deactivation. In addition, the thalamus, the cerebellum, and the anterior cingulate cortex add to the modulation of the startle reflex.

Controllability modulates the neural response to predictable but not unpredictable threat in humans

“…A dissociation between the SCR and EMG response was observed in the current study, however prior work suggests that changes in these psychophysiological responses measure distinct aspects of emotional behavior (Anders et al, 2004; Benedek and Kaernbach, 2010; Davis et al, 1993; 2006; Grillon, 2002; Knight et al, 2010; 2011; Lang et al, 1998; Neuner et al, 2010; Piché et al, 2010). Thus, it is not unusual to observe different patterns or even opposite patterns between these psychophysiological measures (Piché et al, 2010; Weike et al, 2005).…”

Alterations of attention and emotional processing following childhood-onset damage to the prefrontal cortex.

“…Particularly, Swerdlow, Geyer, & Braff (2001) have pointed out the participation of the medial prefrontal cortex in PPI regulation. Functional neuroimaging studies suggest the involvement of the human PFC in the prepulse inhibition effect, consistent with previous results in rats (Campbell et al, 2007; Hazlett et al, 1998; Neuner et al, 2010). These findings, along with reported deficits in attention following PFC damage (Stuss & Benson, 1986) and prefrontal activity during the performance of tasks requiring attention (Fuster, 2008), suggest that the PFC is necessary for effective regulation of attention.…”

Simultaneous acquisition of corrugator electromyography and functional magnetic resonance imaging: A new method for objectively measuring affect and neural activity concurrently

“…The few others have used electrodermal activity (Delgado et al, 2008; EDA, measuring sweat gland activation), pupil dilation (Siegle et al, 2003; Johnstone et al, 2007), cardiac activity (Critchley et al, 2005), or startle (Neuner et al, 2010) to infer changes in emotional state. There are several problems with these methods (see Table 1).…”