Neurophysiological Coding of Traits and States in the Perception of Pain

Abstract

Perception is not a simple reflection of sensory information but varies within and between individuals. This applies particularly to the perception of pain, which, in the brain, is associated with neuronal responses at different frequencies. Here, we show how these different neuronal responses subserve interindividual and intraindividual variations in the perception of identical painful stimuli. A time-frequency analysis of single trial electroencephalographic data indicates that pain-related responses in the theta frequency range but not at higher gamma frequencies code for interindividual variations in the perception of pain. In contrast, both pain-related theta and gamma responses provide different and complementary information on intraindividual variations in the pain experience. We conclude that theta responses reflect rather constant physiological and psychological traits of the individual, whereas gamma responses relate to short-term modulations of the individual's state. These findings reveal how neuronal responses at different frequencies differentially contribute to the translation of sensory information into a subjective percept.

Theta Signal as the Neural Signature of Social Exclusion

“…A recent study in mice has shown that theta waves are present in the ACC during fear learning (Jeon et al 2010). These signals are also involved in pain physical perception (Liu et al 2010;Schulz et al 2011) and in empathy for pain in humans (Mu et al 2008).…”

“…We predicted that exclusion periods would trigger low cerebral waves, that is, waves located in the theta band frequency. Theta signals, compared with more cognitive cerebral waves such as gamma or beta (Buzsaki 2002), are known to be associated with emotional feelings and primitive sensations (Knyazev 2007), physical pain (Liu et al 2010;Schulz et al 2011), and empathy for pain (Jeon et al 2010). The observation that theta oscillations play an important role in human emotional processing has been widely documented by electroencephalography studies during the last decade.…”

Gamma-Band Oscillations in the Primary Somatosensory Cortex—A Direct and Obligatory Correlate of Subjective Pain Intensity

“…In previous studies, laser-induced gamma-band oscillations have been observed at a latency of ϳ200 ms after stimulus onset, within a frequency range of 50 to 100 Hz (Gross et al, 2007;Tiemann et al, 2010). A 200 ms Hanning window is appropriate for identifying these responses, as (1) it provides a sufficiently high frequency resolution of 5 Hz, (2) it is adequate to avoid contamination of the estimates of poststimulus EEG responses by prestimulus activity, (3) it is in line with the duration of GBOs described by Gross et al (2007) and Schulz et al (2011b).…”

“…Recently, using electroencephalography and magnetoencephalography (MEG), it has been reported that also nociceptive stimuli elicit gamma-band oscillations (GBOs) within the human primary somatosensory cortex (SI; Gross et al, 2007;Hauck et al, 2007). Because the magnitude of these GBOs correlates with the subjective pain intensity, it has been suggested that they reflect cortical activity related directly to the perception of pain (Gross et al, 2007;Schulz et al, 2011b). …”

“…For these reasons, a crucial question must be addressed: are laser-induced GBOs truly and directly related to the intensity of pain perception (Gross et al, 2007;Schulz et al, 2011b)? Or, such as the other EEG responses to nociceptive stimuli, is their magnitude largely determined by stimulus saliency ?…”