How expectation and attention interact to process pain in the brain

Under predictive coding, how is the precision or confidence of ascending prediction error signals represented in cortical dynamics?

It is encoded by postsynaptic gain, which manifests as cortical gain control or excitation-inhibition balance.

Source: Expectation violation and attention to pain jointly modulate neural gain in somatosensory cortex · DOI · quote verified

How were sensory expectations implicitly established in the study's within-block task design?

They were established using a roving oddball sequence, which featured a higher probability of stimulus repetitions in the same location compared to spatial location changes.

Source: Expectation violation and attention to pain jointly modulate neural gain in somatosensory cortex · DOI · quote verified

In the study's roving oddball sequence, how were "deviant" stimuli defined?

Deviants were defined as the first painful stimuli delivered to an unexpected spatial location, driving a bottom-up shift of attention.

Source: Expectation violation and attention to pain jointly modulate neural gain in somatosensory cortex · DOI · quote verified

In the study's roving oddball sequence, how were "standard" stimuli defined?

Standards were defined as the last painful stimuli of each repeated train from the expected spatial location.

Source: Expectation violation and attention to pain jointly modulate neural gain in somatosensory cortex · DOI · quote verified

How was top-down attention manipulated between blocks?

It was manipulated via verbal cues instructing participants to either attend towards pain or attend away from pain.

Source: Expectation violation and attention to pain jointly modulate neural gain in somatosensory cortex · DOI · quote verified

What task did participants perform when the cue "HAND" was presented?

They paid attention to the painful stimuli on their hands and silently counted how many times the stimulation switched location.

Source: Expectation violation and attention to pain jointly modulate neural gain in somatosensory cortex · DOI · quote verified

What task did participants perform when the cue "CROSS" was presented?

They ignored the painful stimuli and silently counted how many times the central fixation cross changed colors.

Source: Expectation violation and attention to pain jointly modulate neural gain in somatosensory cortex · DOI · quote verified

What was the final sample size analyzed in this study after excluding participants with technical issues or artifacts?

The final sample size was 22 participants.

Source: Expectation violation and attention to pain jointly modulate neural gain in somatosensory cortex · DOI · quote verified

What apparatus was used to deliver painful stimuli to participants?

Two intra-epidermal electrodes connected to two Digitimer DS7A stimulators.

Source: Expectation violation and attention to pain jointly modulate neural gain in somatosensory cortex · DOI · quote verified

What general finding did the study show regarding how expectation violation and attention to pain modulate neural activity?

Both were explained by increased precision-weighting (gain) in superficial pyramidal cells of the somatosensory cortex, with expectation violation also increasing recurrent connectivity with fronto-parietal areas.

Source: Expectation violation and attention to pain jointly modulate neural gain in somatosensory cortex · DOI · quote verified

Which contrast was used in the source-localization analysis to identify the coordinates for left and right primary somatosensory cortex (S1)?

The coordinates were derived by comparing right vs. left and left vs. right stimulation (the laterality main effect).

Source: Expectation violation and attention to pain jointly modulate neural gain in somatosensory cortex · DOI · quote verified

Which contrast was used to establish the bilateral coordinates for the secondary somatosensory cortex (S2)?

They were established by comparing attended vs. unattended pain, regardless of the side of stimulation.

Source: Expectation violation and attention to pain jointly modulate neural gain in somatosensory cortex · DOI · quote verified

Which regions were identified as sources in the expectation violation main effect?

The left inferior frontal gyrus (IFG) and right inferior parietal cortex (IPC).

Source: Expectation violation and attention to pain jointly modulate neural gain in somatosensory cortex · DOI

Within the framework of predictive coding, how are superficial and deep pyramidal cells mapped to predictive signals?

Superficial pyramidal cells signal prediction errors to higher-order regions, whereas deep pyramidal cells signal predictions to lower-order regions.

Source: Expectation violation and attention to pain jointly modulate neural gain in somatosensory cortex · DOI · quote verified

How are all intrinsic self-connections modeled within the canonical microcircuit (CMC) in DCM?

They are modeled as polysynaptically inhibiting their target populations.

Source: Expectation violation and attention to pain jointly modulate neural gain in somatosensory cortex · DOI · quote verified

What computational property of predictive coding is represented by the intrinsic excitability (or gain) of superficial pyramidal cells?

It represents the precision of prediction errors.

Source: Expectation violation and attention to pain jointly modulate neural gain in somatosensory cortex · DOI · quote verified

Describe the structure and hierarchical order of the winning baseline model (M10) identified during structure optimization.

Model M10 comprised all eight sources, with IPC hierarchically above IFG, and featured reciprocal connections between S1 and both fronto-parietal regions and between S2 and IFG.

Source: Expectation violation and attention to pain jointly modulate neural gain in somatosensory cortex · DOI · quote verified

Which regions showed top-down attentional modulation of intrinsic connectivity in the winning dynamic causal model?

Bilateral S1, S2, and IFG showed intrinsic connectivity modulation by attention.

Source: Expectation violation and attention to pain jointly modulate neural gain in somatosensory cortex · DOI · quote verified

In the winning model, which areas had their intrinsic connectivity modulated by expectation violation?

Contralateral S1 and bilateral S2.

Source: Expectation violation and attention to pain jointly modulate neural gain in somatosensory cortex · DOI · quote verified

What neural mechanism explains the attention-driven increase in the gain of superficial pyramidal cells in bilateral S1 and S2?

A significant decrease in self-inhibition, representing disinhibition or increased gain.

Source: Expectation violation and attention to pain jointly modulate neural gain in somatosensory cortex · DOI · quote verified

How does expectation violation modulate the gain of superficial pyramidal cells in the primary somatosensory cortex?

It increases gain in contralateral S1 by significantly decreasing self-inhibition.

Source: Expectation violation and attention to pain jointly modulate neural gain in somatosensory cortex · DOI · quote verified

What lateralized difference in forward effective connectivity was observed in the somatosensory hierarchy?

Effective connectivity from S1 to S2 to IFG to IPC was increased in the left hemisphere, but decreased in the right hemisphere.

Source: Expectation violation and attention to pain jointly modulate neural gain in somatosensory cortex · DOI · quote verified

What out-of-sample prediction effect size was obtained using leave-one-out cross-validation of the DCM parameters?

The subset of parameters successfully predicted pain modulation ratings with a correlation of r = .55.

Source: Expectation violation and attention to pain jointly modulate neural gain in somatosensory cortex · DOI · quote verified

What behavioral effect of top-down attention on pain rating was found in the study?

Participants rated pain as significantly less intense when it was unattended compared to when it was attended.

Source: Expectation violation and attention to pain jointly modulate neural gain in somatosensory cortex · DOI · quote verified

Which source regions were linked with the main effect of laterality in early-mid latency windows?

Contralateral primary (S1) and secondary (S2) somatosensory cortices.

Source: Expectation violation and attention to pain jointly modulate neural gain in somatosensory cortex · DOI · quote verified

Which primary source regions were associated with the main effect of attention?

Bilateral S2 (specifically, left S2 and right S2).

Source: Expectation violation and attention to pain jointly modulate neural gain in somatosensory cortex · DOI · quote verified

What cortical sources were associated with the expectation violation main effect?

Bilateral S1 and S2, right IPC, and left IFG.

Source: Expectation violation and attention to pain jointly modulate neural gain in somatosensory cortex · DOI · quote verified

Which source regions were linked to the interaction of attention and expectation violation?

Left IPC and right IFG.

Source: Expectation violation and attention to pain jointly modulate neural gain in somatosensory cortex · DOI · quote verified

What source region was associated with the laterality by expectation violation interaction?

Left S2.

Source: Expectation violation and attention to pain jointly modulate neural gain in somatosensory cortex · DOI · quote verified

How do changes in forward vs. backward connectivity differ in response to expectation violation?

Forward connectivity changes are location-independent, whereas backward connectivity changes are lateralized and specifically depend on the unexpected location.

Source: Expectation violation and attention to pain jointly modulate neural gain in somatosensory cortex · DOI · quote verified

Which specific connectivity parameters predicted individual subjective ratings of pain modulation by attention?

The degree of self-inhibition in left S1 and right S2 under attention.

Source: Expectation violation and attention to pain jointly modulate neural gain in somatosensory cortex · DOI · quote verified

What anatomical pathway is hypothesized to mediate the hierarchical connection between somatosensory and fronto-parietal regions?

The third branch of the superior longitudinal fasciculus.

Source: Expectation violation and attention to pain jointly modulate neural gain in somatosensory cortex · DOI · quote verified

How are ascending and descending extrinsic connections modeled in terms of excitation and inhibition?

Ascending connections are excitatory, while descending connections are inhibitory (mediated by inhibitory interneurons).

Source: Expectation violation and attention to pain jointly modulate neural gain in somatosensory cortex · DOI · quote verified

What previous evidence supports the idea that S1 and S2 signals encode Bayesian surprise?

An EEG study showing that tactile mismatch signals originating in S1 and S2 encode an information-theoretic index reflecting the amount of prediction error.

Source: Expectation violation and attention to pain jointly modulate neural gain in somatosensory cortex · DOI · quote verified

What is a major design limitation of this study noted by the authors?

The lack of a behavioral measure of expectation violation, which prevented direct assessment of expectation effects on pain perception.

Source: Expectation violation and attention to pain jointly modulate neural gain in somatosensory cortex · DOI · quote verified