Memory Traces of Pain in Human Cortex

Abstract

Distinct brain regions process sensory discriminative and affective components of pain; however, the role of these areas in pain memory is unknown. This event-related study investigated the short-term memory for sensory features of cutaneous heat pain using a delayeddiscrimination paradigm and functional magnetic resonance imaging. During memory trials, subjects discriminated the location and intensity of two painful stimuli presented sequentially to the right hand. Control trials comprised the same sequence of stimuli and motor responses but required no delayed discrimination. Stimulus-evoked activity for memory and control trials was generally indistinguishable within the network of regions normally responsive to experimental pain [i.e., the primary somatosensory cortex/posterior parietal cortex (SI/PPC), secondary somatosensory cortex (SII), and anterior insular cortex (aIC)]; these data confirm the painful nature of the stimuli and the similar levels of attention and stimulus encoding engaged during the two randomly presented trial types. Memoryspecific activity, assessed by contrasting the interstimulus interval in memory and control trials, was observed in SI/PPC and aIC but not in SII. We propose that SI/PPC plays a role in the short-term retention of spatial and intensity aspects of noxious stimuli and that aIC activation during memory trials is consistent with the integration of sensory and cognitive (attention, awareness, salience, and memory) components of pain perception. The absence of memory-specific anterior cingulate cortex activation, generally associated with pain unpleasantness, suggests that remembering affective aspects of the stimuli was not required during performance of the sensory delayeddiscrimination task.

Extended cortical activations during evaluating successive pain stimuli

“…This region represents the primary somatosensory area (S1) reflecting the somatic localization of the sensory experience, and its localization corresponds to the reported cortical representation of the CO 2 trigeminal stimulus (Bensafi et al, 2008). Exclusive identification of the anterior insular and the post-central cortical areas as regions related to comparing a pain stimulus with a preceding one agrees with findings associating short-term retention of spatial and intensity aspects of noxious stimuli (Albanese et al, 2007).…”

“…As reported in a previous study (Albanese et al, 2007), subjects described the noxious stimuli as painful but tolerable. The subjects of the comparing group correctly rated stimulus 1 > stimulus 2, 1 < 2 or 1 ¼ 2 in 46 AE 1.6% of the stimulus pairs [95% confidence interval (CI) 42.6-49.3%, one-sample t-test against the chance of 33.3%: P < 0.001].…”

“…Still, at an interval of 10 s, the variable design is not substantially more effective than the fixed design (Figure 1 in (Dale, 1999)) and a major improvement becomes evident at intervals <4 s, which were excluded in the present experiment to avoid habituation and adaptation to the pain stimuli (Hummel et al, 1994). Furthermore, it should be noted that parts of the presented results are similar to results observed with a comparable design where the technical limitation of a fixed interstimulus interval did not apply (Albanese et al, 2007).…”

“…It is known that the subjective experience of pain is processed by distinct brain regions (Coghill et al, 1999). However, brain representation specifically related to pain comparison tasks was only rarely addressed (Albanese et al, 2007).…”

Does It Look Painful or Disgusting? Ask Your Parietal and Cingulate Cortex

“…As mentioned in Introduction, however, our volunteers faced a very different task from that investigated by Singer et al (2004Singer et al ( , 2006; for instance, direct visual information on damaging stimuli was absent in the Singer et al paradigm. There is recent evidence that top-down representations (e.g., related to intensity coding) of painful experiences do not necessarily involve the activation of parietal areas (Kong et al, 2006), unless specific sensory features (e.g., spatial location) are recalled (Albanese et al, 2007). However, the parietal cortex is consistently activated during actual acute pain perception (Porro, 2003), as well as during pain anticipation (Sawamoto et al, 2000;Porro et al, 2002;Berns et al, 2006).…”