Learning about pain: The neural substrate of the prediction error for aversive events

Abstract

Associative learning is thought to depend on detecting mismatches between actual and expected experiences. With functional magnetic resonance imaging (FMRI), we studied brain activity during different types of mismatch in a paradigm where contrastingcolored lights signaled the delivery of painful heat, nonpainful warmth, or no stimulation. When painful heat stimulation was unexpected, there was increased FMRI signal intensity in areas of the hippocampus, superior frontal gyrus, cerebellum, and superior parietal gyrus that was not found with mismatch between expectation and delivery of nonpainful warmth stimulation. When painful heat stimulation was unexpectedly omitted, the FMRI signal intensity decreased in the left superior parietal gyrus and increased in the other regions. These contrasting activation patterns correspond to two different mismatch concepts in theories of associative learning (Rescorla-Wagner, temporal difference vs. Pearce-Hall, Mackintosh). Searching for interventions to specifically modulate activation of these brain regions therefore offers an approach to identifying new treatments for chronic pain, which often has a substantial associative learning component.L earning cues of impending pain allows future painful events to be anticipated and avoided (1, 2). Thus, learning associations between pain and predictive cues has fundamental adaptive value. However, such learning also can have adverse effects. It can exacerbate the unpleasantness of pain (3, 4) and can contribute to chronic pain states (5). We previously have identified brain regions activated by cues associated with pain (6). In this paper, we isolate brain regions that play a critical role in learning cue-pain associations.Learning of a cue-outcome association only takes place when there is a mismatch between outcome and the expectations based on perceived cues (7,8). The first goal of the present study, therefore, was to identify brain regions whose activation pattern is consistent with detecting mismatches between the expectation and the delivery of painful stimulation.The related second goal was to study the extent to which this mismatch-related brain activity conforms to predictions derived from theories of Pavlovian conditioning (9-12), which have formalized the relationship between mismatch detection and associative learning. In these models, mismatch is represented as the difference Ϫ V. Applied to associative learning about pain, represents the intensity of the actual pain and V represents the accumulated strength of the cue-pain association (i.e., the expectation of pain based on the cue). Associative learning corresponds to changes in V. When the intensity of a painful stimulus exceeds expectation, V is increased proportionally to the magnitude of the mismatch. The rate of learning decelerates over successive learning trials as V approaches .What happens, however, when the expectation exceeds the actual pain? In this situation, different models of associative learning have distinct predictions. In one theory (9), mismatc...

Cerebellum and emotional behavior

“…Thus, long-term potentiation (LTP) is present in the vermis after fear learning which is strictly related to associative processes, since it is not present following unpaired CS and US presentation. This conclusion is in line with the behavioral studies showing the requirement of the vermis for CS-US association, but not for baseline responses to CS and US , Ploghaus et al 1999, Ploghaus et al 2000and Maschke et al 2002. Synaptic changes were localized to vermal lobules V and VI, an area that receives convergence of acoustic and nociceptive stimuli Stowell 1944 andSaab andWillis 2003) and it is related to the expression of emotional behavior Sebastiani et al 1992).…”

“…2) while a sensory cue that anticipates the painful stimulation leads to activation of posterior cerebellar vermis ( Fig. 2A) (Ploghaus et al 1999 andPloghaus et al 2000). Therefore, nearby but separate regions are engaged during fear experience and associative learning, i.e.…”

“…Neuroimaging reveals a pattern of cerebellar activation in which pain response and learning activate different cerebellar regions (Ploghaus et al 1999 andPloghaus et al 2000). Painful heat activates the anterior cerebellum around the vermis (see Fig.…”

Brain Mapping-Based Model of Δ9-Tetrahydrocannabinol Effects on Connectivity in the Pain Matrix

“…The hippocampus, on the other hand, has been associated with novelty detection during acute painful stimulation (Bingel et al, 2002;Schneider et al, 2001). Hippocampal activity was reduced when attention was directed away from the painful stimulus (Ploghaus et al, 2000), and it was most consistently observed in studies in …”

Attentional changes during implicit learning: Signal validity protects a target stimulus from the attentional blink.

“…For instance, Wills et al (2007) found differences in the event-related potentials evoked by the onset of stimuli which had previously been either uniquely predictive of a surprising outcome or completely redundant to the occurrence of an expected outcome. Using functional magnetic resonance imaging (fMRI), Ploghaus et al (2000;see also O'Doherty, Dayan, Friston, Critchley, & Dolan, 2003;Turner et al 2004) also found neural substrates that appeared to code absolute prediction error, that is, the mismatch between expected outcome and actual outcome regardless of whether that outcome is overpredicted or underpredicted. On the whole, these studies provide evidence of changes in stimulus processing dictated, in some fashion, by the association between CS and US.…”