Commentary: Top-down and bottom-up modulation of pain-induced oscillations

Commentary: Top-down and bottom-up modulation of pain-induced oscillations. Attention represents one of the main mechanisms of modulation of pain (Wiech et al., 2008). It is a complex function which collects cognitive processes responsible for orienting to, and maintaining brain resources on, the most salient and relevant information for the ongoing behavioral demands (Knudsen, 2007). Whether attention can be captured by and oriented to sensory events depends on several variables, e.g., stimulus features, task demands, and volition (Baluch and Itti, 2011). Bottom-up capture of attention is often conceived as an unintentional and automatic process ruled by the competition between stimulus features, whereas top-down selection concerns an intentional process pertaining to intrinsic motivational and task-related aspects ruled by the subject (Buschman and Miller, 2007). Stimuli interpreted as painful are able to capture individual's attention in a bottom-up fashion if e.g., other stimuli or unrelated plans do not compete with its processing in working memory (Legrain et al., 2012). In a recent issue of Frontiers in Human Neuroscience, Hauck et al. (2015) used electroencephalography (EEG) to investigate the oscillatory neuronal modulation exerted by both top-down and bottom-up attention during nociceptive painful stimulation. To disentangle how the two attentional processes influence neuronal synchronization and desynchronization, the authors manipulated both nociceptive stimulus intensity (i.e., high vs. low; bottom-up orientation) and spatial attention to the stimuli (i.e., attended vs. unattended; top-down control). The authors already investigated the effect of spatial attention on cortical oscillatory activity elicited by electrical painful stimuli (Hauck et al., 2007) by recording magnetoencephalography (MEG) during an oddball paradigm whereby participants were asked to count the rare stimuli on one finger while ignoring the more frequent stimuli on the other finger. The authors concluded that increased attentional capture by salient rare stimuli was reflected by MEG-induced oscillatory high frequency activity (gamma band) localized in the sensory-motor areas. Hauck et al. (2015) expand on their previous methodology by varying location and intensity of laser painful stimuli. Here the participant had to attend and evaluate only stimuli delivered to one finger while ignoring those delivered to the other finger. At variance with their previous work, they delivered equiprobable stimuli on the ring and index finger, thus avoiding a bottom-up confounding effect associated with variable probability of occurrence of the stimuli. They investigated attentional effects on the entire spectral activity and found that power (i.e., magnitude) of gamma oscillations increased (maximal at 270 ms post-stimulus) while …