The Transition from Pain Related Attention to Vigilance

Lenz, Fred

Abstract

When attention to a stimulus is prolonged over minutes to hours it is referred to as vigilance, and when vigilance is abnormally increased it is referred to as hypervigilance ? `the excessive readiness to select and respond to a kind of stimulus'. Vigilance and hypervigilance are related dimensions of pain and are found in idiopathic and `nociceptive' pain syndromes, although our understanding of their neural basis is limited. We propose to adapt a Continuous Performance Task from Human Factors to the study of pain, i.e. CPTpain. In this task, the subject pushes a button to indicate detection of painful target stimuli when they occur in a train of nontarget nonpainful stimuli, and vigilance to pain can be measured by detected nontargets and arousal. We propose to use a CPTpain as we record and analyze local field potentials (LFP) during the week between the implantation and removal of grid electrodes on the brain for the treatment of intractable epilepsy, which is a platform for studies of pain with unrivaled resolution and clarity. We hypothesize a network for vigilance to pain that includes frontal, parietal and cingulate modules based upon imaging studies of vigilance to visual targets. This type of network includes modules and the connections between modules that we will identify (as in the past) by the causal interactions between them, where causal interactions are inferred if past knowledge of activity at a module reduces the prediction error for activity at a second module. Our Preliminary Data shows that detected nontargets and arousal in a CPTpain are associated with increased sensitivity to acute painful stimuli, i.e. vigilance might influence pain. These Data also demonstrate a Parietal EEG Signature for vigilance to pain that is correlated with errors and so suggest parietal involvement in a distributed network for vigilance to pain. Although modules and interactions that have a critical role in vigilance to pain cannot be identified by analysis of LFPs (or fMRI), they can be demonstrated by studies of the effect of lesions on errors and arousal in a CPTpain. Therefore, we propose novel studies of MRI scans and measures of vigilance to pain in patients admitted to The Johns Hopkins Hospital with acute strokes by using software packages for analysis of lesions (LDDMM) with our long term collaborator Dr Hillis, who has used these packages extensively for the study of attention. Finally, our preliminary data demonstrates that parietal structures are spared in patients with insular strokes who develop Central Post Stroke Pain (CPSP), which is consistent with parietal involvement in vigilance as a mechanism of CPSP. The results of these novel proposed studies are expected to frame testable hypotheses for the neuroscience of vigilance to pain, and for anatomically based surgical or stimulation therapies for pain syndromes associated with hypervigilance. The potential of analyses of networks for vigilance to pain is suggested by the impact of network analysis on the neuroscience of vision, and on surgical and stimulation therapies for the treatment of movement and psychiatric disorders.

Public Health Relevance

Attention, vigilance and hypervigilance in humans are related dimensions of pain and components of clinical pain syndromes, but our understanding of their neural basis is limited. We propose a novel study of an experimental protocol for vigilance to define the network for vigilance to pain by measuring of neural activity through electrodes implanted on the brain for the investigation of intractable epilepsy. The modules in this network which have a critical role in vigilance to pain will be determined by behavioral studies of patients with acute strokes, and will be potential targets for surgical or stimulation therapies for pain.