Biology subjects

Ojala, K. E.

Publications and source records attributed to Ojala, K. E..

3 recordsLinked to original sources

bioRxiv2023

Conditioned pain modulation of pressure pain is associated with reduced activation in the parietal operculum and posterior insula

Conditioned pain modulation (CPM) is the phenomenon of pain inhibiting further pain. CPM is impaired in patients suffering from various chronic pain conditions and may resemble a pro-nociceptive profile. A possible neural mechanism for CPM is descending control from cortical regions via brainstem that modulates neural activity at the level of the dorsal horn of the spinal cord where noxious input first arrives. We studied the involvement of the descending pain modulatory pathway by simultaneous functional imaging of the brain, brainstem, rostral medulla, and cervical spinal cord during CPM with pressure cuff algometry in 42 healthy human participants. Subjective CPM as measured by decreased pain ratings developed over the experiment with application of repeated short test stimuli for long conditioning pain compared with non-painful conditioning. Test stimuli paired with painful conditioning were associated with decreased BOLD fMRI activity in the parietal operculum (secondary somatosensory cortex) and posterior insula, as well as increased responses in bilateral primary somatosensory cortices. Subjective CPM reflected in pain ratings was associated with decreased test stimulus responses in somatosensory and pain-responsive brain regions such as the anterior and posterior insula and the parietal operculum. Conditioning pain and test pain were associated with increased neural activity in stimulus-ipsilateral spinal cord dorsal horn at segment C6 and C4, respectively. No evidence for neural correlates of CPM or associations with subjective CPM was observed in the spinal cord. Functional connectivity between the brain and spinal cord was altered during both conditioning and test pain but did not depend on conditioning intensity. Taken together, we observed neural activity associated with both negative (CPM) and positive modulation of pain in different somatosensory and pain-associated brain regions, and an association of these and other neural responses with subjective CPM. While we found that painful stimuli altered the connectivity along the descending pain modulatory pathway, we did not find evidence for a modulation by conditioning intensity nor neural correlates of CPM in the spinal cord.

neuroscience↗

bioRxiv2021

Transcranial theta-burst stimulation of primary sensory cortex attenuates somatosensory threat memory in humans

Sensory cortices are required for learning to discriminate complex stimuli that predict threat from those that predict safety in rodents. Yet, sensory cortices may not be needed to learn threat associations to simple stimuli. It is unknown whether these findings apply in humans. Here, we investigated the role of primary sensory cortex in discriminative threat conditioning with simple and complex somatosensory conditioned stimuli (CS) in healthy humans. Immediately before conditioning, participants received continuous theta-burst transcranial magnetic stimulation (cTBS) to primary somatosensory cortex either in the CS-contralateral or CS-ipsilateral hemisphere. After overnight consolidation, threat memory was attenuated in the contralateral compared to the ipsilateral group, as indicated by reduced startle eye-blink potentiation. There was no evidence for a difference between simple and complex stimuli, or that CS identification or conditioning was affected, suggesting a stronger effect of cTBS on consolidation than on initial stimulus processing. We propose that non-invasive stimulation of sensory cortex may provide a new avenue for interfering with threat memories in humans.

neuroscience↗

bioRxiv2017

Dopaminergic drug effects on probability weighting during risky decision-making

Dopamine has been associated with risky decision-making, as well as with pathological gambling, a behavioural addiction characterized by excessive risk-taking behaviour. However, the specific mechanisms through which dopamine might act to foster risk-taking and pathological gambling remain elusive. Here we test the hypothesis that this might be achieved, in part, via modulation of subjective probability weighing during decision-making. Healthy controls (n = 21) and pathological gamblers (n = 16) played a decision-making task involving choices between sure monetary options and risky gambles both in the gain and loss domains. Each participant played the task twice, either under placebo or the dopamine D2/D3 receptor antagonist sulpiride, in a double-blind, counter-balanced, design. A prospect theory modelling approach was used to estimate subjective probability weighting and sensitivity to monetary outcomes. Consistent with prospect theory, we found that participants presented a distortion in the subjective weighting of probabilities, i.e. they overweighted low probabilities and underweighted moderate to high probabilities, both in the gain and loss domains. Compared with placebo, sulpiride attenuated this distortion in the gain domain. Across drugs, the groups did not differ in their probability weighting, although in the placebo condition, gamblers consistently underweighted losing probabilities. Overall, our results reveal that dopamine D2/D3 receptor antagonism modulates the subjective weighting of probabilities in the gain domain, in the direction of more objective, economically rational decision-making.\n\nSignificance statementDopamine has been implicated in risky decision-making and gambling addiction, but the exact mechanisms underlying this influence remain partly elusive. Here we tested the hypothesis that dopamine modulates subjective probability weighting, by examining the effect of a dopaminergic drug on risk-taking behaviour, both in healthy individuals and pathological gamblers. We found that selectively blocking dopamine D2/D3 receptors diminished the typically observed distortion of winning probabilities, characterized by an overweighting of low probabilities and underweighting of high probabilities. This made participants more linear in their subjective estimation of probabilities, and thus more rational in their decision-making behaviour. Healthy participants and pathological gamblers did not differ in their risk-taking behaviour, except in the placebo condition in which gamblers consistently underweighted losing probabilities.

neuroscience↗