Plastic phase-locking and magnetic mismatch response to auditory deviants in temporal lobe epilepsy.
The magnetic equivalent (MMNm) of mismatch negativity may reflect auditory discrimination and sensory memory. To study whether temporal lobe epilepsy (TLE) affects automatic central auditory-change processing, we recorded magnetoencephalographic (MEG) responses to standard and duration-deviant sounds in 12 TLE patients and 12 age-matched controls, and repeated MEG measurement in 8 patients 6-30 months following epilepsy surgery and in 6 controls 3-8 months after their first measurement. We compared the MMNm between patients and controls, and also evaluated intertrial phase coherences as indexed by phase-locking factors (PLF) using wavelet-based analyses. We observed longer MMNm latencies for patients than for controls. Dipole modeling and minimum-current estimates together showed bi-frontotemporal sources for MMNm. The phase locking across trials was dominant at the 4- to 14-Hz band, and the main difference in PLF between deviant- and standard-evoked responses occurred in the time frame of 150-250 ms after stimulus onset. Notably, in the 5 patients who became seizure free after removal of right temporal epileptic focus, the phase-locking phenomena resulting from deviant stimuli were enhanced, and even more distributed in the frontotemporal regions. We conclude that mesial TLE might affect auditory-change detection, and a successful surgery causes a possible plastic change in phase locking of deviant-evoked signals.
Lin
Yung-Yang
YY
Institute of Physiology, School of Medicine, National Yang-Ming University, Taipei, Taiwan. yylin@vghtpe.gov.tw
Hsiao
Fu-Jung
FJ
Shih
Yang-Hsin
YH
Yiu
Chun-Hing
CH
Yen
Der-Jen
DJ
Kwan
Sheong-Yeong
SY
Wong
Tai-Tong
TT
Wu
Zin-An
ZA
Ho
Low-Tone
LT
D000161:Acoustic Stimulation / Q000379:methods*; D000293:Adolescent; D001303:Auditory Cortex / Q000503:physiopathology*; D001307:Auditory Perception; D004833:Epilepsy, Temporal Lobe / Q000503:physiopathology*; D005072:Evoked Potentials, Auditory; D005260:Female; D006801:Humans; D015225:Magnetoencephalography; D008297:Male; D008568:Memory; D009473:Neuronal Plasticity; D046709:Pattern Recognition, Physiological