Fabrizi, L. | Search bioRxiv

bioRxiv2022

Early life pain experience changes adult functional pain connectivity in the rat somatosensory and the medial prefrontal cortex

Early life pain experience (ELP) alters adult pain behaviour and increases injury induced pain hypersensitivity, but the effect of ELP upon adult functional brain connectivity is not known. We have performed continuous local field potential (LFP) recording in the awake adult male rats to test the effect of ELP upon functional cortical connectivity related to pain behaviour. Somatosensory cortex (S1) and medial prefrontal cortex (mPFC) LFPs evoked by mechanical hindpaw stimulation were recorded simultaneously with pain reflex behaviour for 10 days after adult skin injury. We show that, post adult injury, S1 LFP delta and gamma energy and S1 LFP delta/gamma frequency modulation are significantly increased in ELP rats compared to controls. Adult injury also induces increases in S1-mPFC functional connectivity which is significantly prolonged in ELP rats, lasting 4 days compared to 1 day in controls. Importantly, the increases in LFP energy and connectivity in ELP rats were directly correlated with increased behavioural pain hypersensitivity. Thus, early life pain (ELP) alters adult brain functional connectivity, both within and between cortical areas involved in sensory and affective dimensions of pain. The results reveal altered brain connectivity as a mechanism underlying the effects of early life pain upon adult pain perception. Significance StatementPain and stress in early life has a lasting impact upon pain behaviour and may increase vulnerability to chronic pain in adults. Here we record pain-related cortical activity and simultaneous pain behaviour in awake adult male rats previously exposed to pain in early life. We show that functional connectivity within and between the somatosensory cortex and the medial prefrontal cortex is increased in these rats and that these increases are correlated with their behavioural pain hypersensitivity. The results reveal that early life pain alters adult brain connectivity, which may explain the impact of childhood pain upon adult chronic pain vulnerability.

neuroscience↗

bioRxiv2021

Widespread nociceptive maps in the human neonatal somatosensory cortex

Topographic cortical maps are essential for spatial localisation of sensory stimulation and generation of appropriate task-related motor responses. Somatosensation and nociception are finely mapped and aligned in the adult somatosensory (S1) cortex, but in infancy, when pain behaviour is disorganised and poorly directed, nociceptive maps may be less refined. We compared the topographic pattern of S1 activation following noxious (clinically required heel lance) and innocuous (touch) mechanical stimulation of the same skin region in newborn infants (n=32) using multi-optode functional near-infrared spectroscopy (fNIRS). Signal to noise ratio and overall activation area did not differ with stimulus modality. Within S1 cortex, touch and lance of the heel elicit localised, partially overlapping increases in oxygenated haemoglobin (HbO), but while touch activation was restricted to the heel area, lance activation extended into cortical hand regions. The data reveals a widespread cortical nociceptive map in infant S1, consistent with their poorly directed pain behaviour.

neuroscience↗