Low-Intensity Repetitive Transcranial Magnetic Stimulation Improves Abnormal Visual Cortical Circuit Topography and Upregulates BDNF in Mice (The Journal of Neuroscience 2014, 34(32):10780 –10792)

報告日期: 2015/11/13
報告時間: 3:10/4:00
報告學生: 經士弘
講評老師: 許桂森
附件下載: 下載[1519-1443054947-1.pdf] 

Low-intensity repetitive transcranial magnetic stimulation improves abnormal visual cortical circuit topography and upregulates BDNF in mice

J. Neurosci., 2014, 34(32):10780 –10792.

Student: Ching, Shi-Hong (經士弘)

Commentator: Hsu, Kuei-Sen (許桂森老師)

Repetitive transcranial magnetic stimulation (rTMS) uses trains of magnetic pulses to induce electric currents in the brain that modulate cortical activity1 and can produce persistent excitability and behavioral modifications2. Although these changes are generally attributed to induce neuronal spiking within the stimulated region3, perifocal areas also received stimulation, albeit at lower intensities, below the neuron firing threshold4. However, the functional importance of this perifocal subthreshold stimulation is unclear. In this study, the authors examined low-intensity rTMS (LI-rTMS)-induced changes on the mouse visual system with an afferent geniculocortical [dorsal LGN (dLGN) to primary visual cortex (V1)] and the efferent corticotectal (V1 to superior colliculus) projections in both normal (wild-type) and abnormal ephrin- A2A5-/- adult mice5. They found that in the afferent geniculocortical projection, LI-rTMS decreased the abnormally high dispersion of retrogradely labeled neurons in the dLGN of ephrin-A2A5-/- mice, indicating geniculocortical map refinement. In the corticotectal efferents, LI-rTMS improved topography of the most abnormal TZs in ephrin-A2A5-/- mice without altering topographically normal TZs. They also investigated the possible molecular mechanism for LI-rTMS-induced structural plasticity and found that BDNF was upregulated after a single stimulation for all groups, but only sustained in the superior colliculus of ephrin-A2A5-/- mice. These results show that LI-rTMS upregulates BDNF, promoting a plastic environment conducive to beneficial reorganization of abnormal cortical circuits, information that has important implications for clinical rTMS.

References

  1. Pascual-Leone A (2006) Disrupting the brain to guide plasticity and improve behavior. Prog Brain Res 157:315–329.
  2. Maeda F et al., (2000) Modulation of corticospinal excitability by repetitive transcranial magnetic stimulation. Clin Neurophysiol 111:800–805.