TABLE 2.

Evaluation of cortical alterations in CBP patients using EEG and MEG techniques.

Author, year	Scan type	Patients	Controls	Stimulation	Main findings
					(patients compared with controls)
Diers et al., 2007	EEG	14 CLBP	13 Healthy controls	Electrical stimuli	•Larger N80 component after stimulation •No significant group difference in the N150 component •Smaller P260 component after stimulation •Positive correlation between N80/N150 amplitudes and perceptual sensitization •Increased perceptual sensitization and increased processing of the sensory-discriminative aspect (N80 component) of pain in patients
Flor et al., 2004	EEG	16 CBP, 16 THA	16 Healthy controls	Electrical stimuli	•Significantly lower pain threshold and pain tolerance in CBP patients compared with THA patients and healthy controls •Reduced habituation in CBP patients •No significant differences in amplitudes of N150, P260, P300, and N500 among three groups •Lower stimulation intensity in CBP patients
Flor et al., 1997a	EEG and MEG	10 CBP	Nine healthy controls	Standard intracutaneous electrical stimuli to the left back and index finger with a non-painful and a painful intensity	•Enhanced power of the evoked early magnetic field (< 100 ms) in LBP patients than healthy controls following painful back stimulation •Medial shift in the maximum activity elicited in the S1 in LBP patients
Flor et al., 1997b	EEG	12 CBP	12 Healthy controls	Pain- and body-related verbal materials	•No more recognition of patients in the pain-related words •Enhanced N100 and N200 of the left hemisphere to pain-related words, when compared to neutral words •A positive shift to all words extending into the 800 ms range •No distinct P300 in CBP patients •Enhanced levels of skin conductance to the pain-related words
Tamburin et al., 2014	EEG	12 CLBP	12 Healthy controls	IGT	•Lower scores of cognitive measures (MCST) in CLBP patients influenced by pain intensity and duration •Worse performance and the absence of a learning process during the behavioral IGT test with no effect of pain features in CLBP patients •Poor performance in the MCST and the IGT in CLBP patients •The FRN amplitude in wins was higher than in losses in controls, while the opposite happened in CLBP patients •The P300 amplitude was higher in wins than in losses in controls, while there was no difference in CLBP patients
Wiech et al., 2000	EEG	10 CBP	Nine healthy controls	Electrical stimulation	•Somatotopic organization of the S1 •Correlation between the amount of reorganization and pain rating

EEG, electroencephalography; MEG, magnetoencephalography electromyographic activity; ms, millisecond; CBP, chronic back pain; CLBP, chronic low back pain; THA, tension headache; MCST, modified card sorting test; IGT, Iowa gambling task; ERPs, event-related potentials.