Waveforms
All three regions showed a stimulation-locked response
Animal-averaged waveforms at 2×, 10× and 20× MT are in Figure 3 and the waveforms of every animal in Figure S4.
IASP 2026 World Congress on Pain · Bangkok · Poster 105 (abstract 10418) · Thursday 29 October 2026
Temporal and Spectral Signatures of Graded Nociceptive Stimulation Across S1, PFC, and ACC in a Large-Animal Intracranial Model
We recorded S1, PFC and ACC simultaneously in 18 anaesthetised pigs while stimulating the ulnar nerve at 2, 10 and 20 times motor threshold. Graded stimulation increased phase-locked (evoked) power in all three regions, and corrected time–frequency maps localised early total-power differences in S1 and ACC.
Study
Research questions
- Does cortical power increase with stimulation intensity in S1, PFC and ACC?
- Is the increase phase-locked or non-phase-locked?
- When and at which frequencies does it occur?
Methods
Eighteen female Danish Landrace pigs were anaesthetised with propofol and fentanyl. Micro-ECoG arrays were placed on S1 and PFC, and a depth array was introduced towards the ACC (17 animals after quality control). The right ulnar nerve was stimulated with biphasic pulses at 2×, 10× and 20× motor threshold (MT) in ascending order, with stimulus onsets jittered by ±250 ms (154 sequences). Power at 35–120 Hz over 0–400 ms was compared between intensities with mixed models (animal random effects, Holm correction), and 20–200 Hz time–frequency maps with TFCE.
How each animal's power changed
One dot per animal: its change between the two intensities, averaged over its stimulation sequences, with a line joining the same animal across total, evoked and induced power. Squares are the mixed-model estimates with 95% confidence intervals, filled where Holm-adjusted P < 0.05. Hover over or click an animal to see its own waveforms; ratios above 3 are drawn as triangles at the top.
Findings
Power components
Evoked power was higher at 10× and 20× than at 2× MT in all three regions
At 20× MT, evoked power was 1.25 times the 2× MT value in S1 and PFC and 1.75 times in ACC; all six 10× and 20× vs 2× contrasts had Holm P ≤ 0.005. Evoked power was also higher at 20× than at 10× MT in PFC and ACC. No total- or induced-power contrast survived correction (Figure 4).
Time–frequency maps
Corrected total-power differences appeared within ~160 ms in S1 and ACC
Four of the nine maps survived correction: 10× and 20× vs 2× MT in S1 and ACC. Differences were largest at 20–30 Hz, 85–105 ms after stimulation; at 20× vs 2× MT the ACC cluster extended to ~160 Hz. No map survived in PFC or for 20× vs 10× MT (Figure 5).
Conclusions
Separating the response components revealed effects a broad power average did not
Cortical measures of nociception should state their response component and recording site. Recorded under general anaesthesia, these responses capture cortical nociceptive processing. Electrical nerve stimulation bypasses peripheral receptors, so responses to natural noxious stimuli may differ, and all animals were female.