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Electromagnetic Fields in Biological Systems
(50 Hz, 500 μT, for a single session of 15 hours and total of 60 hours, i.e., 15 h/day for
4 days) induced enhanced STP and LTP in hippocampal slices and increased seizure
susceptibility in neocortical slices. The authors concluded that although ELF-EMF
exposure exerts significant effects on synaptic activity, the overall changes may strongly
depend on the synaptic structure and neuronal network of the affected region together
with the specific spatial parameters and constancy of ELF-EMF.
Walker et al. (2007) tested the effect of PEMF (2 Hz; 0.03, 0.3 and 3 mT; 1, 10, and
100 μV/cm; 4 h/day for 5 days) on nerve crush injury in a rat model. However, no difference was found in recovery of the toe-spread function between any PEMF treatments
compared with the sham exposure.
Yang et al. (2010) investigated the neuroprotective effects of repetitive or rapid-rate
transcranial magnetic stimulation (rTMS; 0.5 Hz, 250 V/m) on 6-hydroxydopamine
(6-OHDA)-induced rats with Parkinson’s disease (PD) (see also Section 3.5.1). Rapidrate transcranial magnetic stimulation was given to rats with PD induced by 6-OHDA
daily for 4 weeks to examine its protective effects. Rotational test showed that rTMS
significantly attenuated apomorphine-induced turns in rats with PD. Tissue processing showed that rTMS alleviated 6-OHDA-induced loss of dopaminergic neurons in rat
substantia nigra. Furthermore, rTMS decreased the levels of cyclooxygenase-2 (COX-2)
and tumor necrosis factor (TNF)-α in rat substantia nigra and prevented the fall of
dopamine in the striatum of rats with PD.
Smith, Jackson, and Rorden (2009) investigated whether rTMS (28 Hz) could disrupt
frontal eye fields (FEFs) while participants of the study performed an auditory localization task. Participants were stimulated for 176 milliseconds at 28 Hz (five pulses), and
stimulation began 32 milliseconds before the onset of the central cue. In each trial a
visual cue directed a participant’s attention to the probable laterality of an auditory target, and the participant had to decide whether the subsequent target sound came from
an upper or a lower speaker. In the absence of TMS, individuals could respond faster
to targets that occurred on the cued side (valid trials) than when the target appeared
contralaterally to the cued side (invalid side). The presence of TMS interfered with this
effect, such that the costs associated with ipsilateral invalidly cued targets were substantially reduced. These results suggest that the eye-movement system is needed for normal
auditory attention.
Hamidi, Tononi, and Postle (2008) conducted a functional neuroimaging study for
investigating which specific regions of the frontal and the posterior parietal cortices contribute to the retention of information in spatial working memory using rTMS (10 Hz, produced motor-evoked potential [MEP] ≥50 μV). They assessed the necessity for short-term
retention of spatial information of brain areas identified by previous functional imaging studies: dorsolateral prefrontal cortex (DLPFC), FEFs, superior parietal lobule (SPL),
and intraparietal sulcus (IPS). The administration of rTMS spanned the 3-second delay
period of a spatial delayed-recognition task. The postcentral gyrus (PCG) was included
to control any regionally nonspecific effects of rTMS. The only regionally specific effect
was a significant decrease in reaction time when rTMS was applied to SPL. Additionally,
rTMS lowered accuracy to a greater extent when applied to the left hemisphere than to
the right and was more disruptive when applied contralaterally versus ipsilaterally to the
Electromagnetic Fields in Biological Systems
(50 Hz, 500 μT, for a single session of 15 hours and total of 60 hours, i.e., 15 h/day for
4 days) induced enhanced STP and LTP in hippocampal slices and increased seizure
susceptibility in neocortical slices. The authors concluded that although ELF-EMF
exposure exerts significant effects on synaptic activity, the overall changes may strongly
depend on the synaptic structure and neuronal network of the affected region together
with the specific spatial parameters and constancy of ELF-EMF.
Walker et al. (2007) tested the effect of PEMF (2 Hz; 0.03, 0.3 and 3 mT; 1, 10, and
100 μV/cm; 4 h/day for 5 days) on nerve crush injury in a rat model. However, no difference was found in recovery of the toe-spread function between any PEMF treatments
compared with the sham exposure.
Yang et al. (2010) investigated the neuroprotective effects of repetitive or rapid-rate
transcranial magnetic stimulation (rTMS; 0.5 Hz, 250 V/m) on 6-hydroxydopamine
(6-OHDA)-induced rats with Parkinson’s disease (PD) (see also Section 3.5.1). Rapidrate transcranial magnetic stimulation was given to rats with PD induced by 6-OHDA
daily for 4 weeks to examine its protective effects. Rotational test showed that rTMS
significantly attenuated apomorphine-induced turns in rats with PD. Tissue processing showed that rTMS alleviated 6-OHDA-induced loss of dopaminergic neurons in rat
substantia nigra. Furthermore, rTMS decreased the levels of cyclooxygenase-2 (COX-2)
and tumor necrosis factor (TNF)-α in rat substantia nigra and prevented the fall of
dopamine in the striatum of rats with PD.
Smith, Jackson, and Rorden (2009) investigated whether rTMS (28 Hz) could disrupt
frontal eye fields (FEFs) while participants of the study performed an auditory localization task. Participants were stimulated for 176 milliseconds at 28 Hz (five pulses), and
stimulation began 32 milliseconds before the onset of the central cue. In each trial a
visual cue directed a participant’s attention to the probable laterality of an auditory target, and the participant had to decide whether the subsequent target sound came from
an upper or a lower speaker. In the absence of TMS, individuals could respond faster
to targets that occurred on the cued side (valid trials) than when the target appeared
contralaterally to the cued side (invalid side). The presence of TMS interfered with this
effect, such that the costs associated with ipsilateral invalidly cued targets were substantially reduced. These results suggest that the eye-movement system is needed for normal
auditory attention.
Hamidi, Tononi, and Postle (2008) conducted a functional neuroimaging study for
investigating which specific regions of the frontal and the posterior parietal cortices contribute to the retention of information in spatial working memory using rTMS (10 Hz, produced motor-evoked potential [MEP] ≥50 μV). They assessed the necessity for short-term
retention of spatial information of brain areas identified by previous functional imaging studies: dorsolateral prefrontal cortex (DLPFC), FEFs, superior parietal lobule (SPL),
and intraparietal sulcus (IPS). The administration of rTMS spanned the 3-second delay
period of a spatial delayed-recognition task. The postcentral gyrus (PCG) was included
to control any regionally nonspecific effects of rTMS. The only regionally specific effect
was a significant decrease in reaction time when rTMS was applied to SPL. Additionally,
rTMS lowered accuracy to a greater extent when applied to the left hemisphere than to
the right and was more disruptive when applied contralaterally versus ipsilaterally to the