Prepulse inhibition vs cognitive modulation of the hand-blink reflex

Abstract

The excitability of brainstem circuitries mediating defensive blinking in response to abrupt sensory inputs is continuously modulated by cortical areas, e.g., the hand-blink reflex (HBR), elicited by intense electrical median nerve stimulation, is enhanced when the stimulated hand is close to the face, with the behavioural purpose to optimize self-protection from increased threat. Here we investigated whether such cortically mediated HBR facilitation can be influenced by prepulse inhibition (PPI), which is known to occur entirely at the subcortical level. Twenty healthy volunteers underwent HBR recordings in five experimental conditions. In conditions 1 and 2, the stimulated hand was held either near (1) or far (2) from the face, respectively. In conditions 3 and 4, stimulation of the hand near the face was preceded by a peri-liminal prepulse to the index finger of the contralateral hand held either near (3) or far from the face (4). In condition 5, participants self-triggered the stimulus eliciting the HBR. We observed a reproducible HBR in 14 out of 20 participants and measured onset latency and area of the HBR in orbicularis oculi muscles bilaterally. HBR area decreased and latency increased in condition 2 relative to condition 1; HBR area decreased and latency increased markedly in condition 3, and somewhat less in condition 4, relative to conditions 1 and 2; self-stimulation (condition 5) also suppressed HBRs, but less than prepulses. These findings indicate that PPI of the HBR is more robust than the cognitive modulation exerted by top-down cortical projections. Possibly, an attentional shift to a prepulse may serve to reduce blinking in response to perturbation when it is convenient, in a given situation, not to interrupt ongoing visual processing.

Machine learning for exploring neurophysiological functionality in multiple sclerosis based on trigeminal and hand blink reflexes

“…Different accuracy in classification could represent a different localization of lesions in our group of patients. Functional-anatomical differences in sensorimotor circuits that underlie TBR and HBR have been proposed: the former including the pontine reticular formation, the latter involving the mesencephalic reticular formation 4 , 49 , 50 . Furthermore, it has been proposed that distinct mechanisms underlie the two different spatial responses of HBR.…”

On the recovery of disorders of consciousness under intrathecal baclofen administration for severe spasticity—An observational study

“…Serial investigation of PPI would be of greatest interest. Furthermore, the hand‐blink reflex, a defensive reflex mediated by brainstem circuits, which is modulated by cognitive influences (Versace et al., 2021), would be a suitable tool to track changes in consciousness induced at the brainstem level.…”

Conscious agency vs. pre‐conscious sensory filtering: Disparate suppression of trigeminal blink reflex by self‐stimulation and by prepulses

“…Volitional activity, sensory inputs, and motivational and emotional factors may all influence reflexes (Sechenov, 1863) by gaining access to polysensory integrative brainstem centers, where they may modify the excitability of reflex pathways. Examples include the depression by self‐stimulation of cutaneous flexor reflex responses (Young, 1973), stretch reflexes (Rothwell et al, 1986), cutaneous reflexes evoked during human walking (Baken et al, 2006), auditory startle reactions (Kawachi et al, 2014), trigeminal BR (Versace et al, 2020), and hand blink reflex (Versace et al, 2021).…”

“…BR excitability modulation already during the preparation phase reflects a tonic tuning of the magnitude of protective blinking according to situational needs. Previous studies evidenced that the excitability of brainstem circuitries mediating defensive blinking in response to abrupt sensory inputs is continuously modulated by cortical areas according to threat evaluation (Bufacchi & Iannetti, 2018;Versace et al, 2020Versace et al, , 2021.…”

“…PPI was demonstrated not only for the trigeminal BR but also for auditory BR (Valls‐Solé et al, 1999), masseteric inhibitory reflex (Gomez‐Wong & Valls‐Solé, 1996), auditory startle reaction (Blumenthal & Gescheider, 1987; Muller et al, 2003; Swerdlow et al, 1999), somatosensory startle responses (Kumru et al, 2009), kinematic startle responses (Castellote et al, 2017), and the so‐called “hand‐blink reflex” (Versace et al, 2021).…”