Study type: Medical/biological study (experimental study)

Effects of the static and ELF magnetic fields on the neuronal population activity in Morimus funereus (Coleoptera, Cerambycidae) antennal lobe revealed by wavelet analysis. med./bio.

Published in: Comp Biochem Physiol A Mol Integr Physiol 2015; 181: 27-35

Aim of study (acc. to author)

To investigate the effect of a static magnetic field and of extremely low frequency magnetic fields on the neuronal population activity in the antennal lobe (part of the insect brain which receives the input from the olfactory sensory neurons on the antenna) of beetles.

Background/further details

The species Morimus funereus is classified as "vulnerable" by the International Union for Conservation of Nature and Natural Resources (IUCN). Hence, it is important to understand how different ecological factors such as magnetic fields could affect the nervous system of this beetle.
An additional goal of this study was to test whether the wavelet transformation is suitable to measure the potential exposure induced effects on the neuronal population activity of insects.
Three experiments were conducted: 1.) exposure to a static magnetic field (n=7), 2.) exposure to a sine wave 50 Hz magnetic field (n=12) and 3.) exposure to a square wave 50 Hz magnetic field (n=10). In the first experiment, a 5 minutes baseline was recorded before the exposure period, followed by a 5 minutes recording during exposure and a 5 minutes after-exposure recording. The experiments 2 and 3 consisted of 3 exposure sessions with exposure durations of 5, 10, and 15 minutes. Recordings were performed 5 minutes before the first exposure (baseline) as well as immediately after the first exposure period (5 min) and 35 min later. Immediately after the "35 minutes later recording" started the next exposure period (10 min) and 35 min later the next recording. Subsequently, a 15 min exposure period started, which was 35 min later followed by the last recording.

Endpoint

Exposure

Exposure Parameters
Exposure 1:
Exposure duration: continuous for 5 minutes
Exposure 2: 50 Hz
Exposure duration: continuous for 5, 10, and 15 minutes
Exposure 3: 50 Hz
Exposure duration: continuous for 5, 10, and 15 minutes

Exposure 1

Main characteristics
Frequency
Type
Exposure duration continuous for 5 minutes
Exposure setup
Exposure source
Setup magnetic field was produced by an electromagnet, powered by a DC voltage source of 12 V; magnet was placed at a distance of 2 cm from the left antenna
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 2 mT mean measured - at head surface

Exposure 2

Main characteristics
Frequency 50 Hz
Type
Waveform
Exposure duration continuous for 5, 10, and 15 minutes
Additional info sine wave
Exposure setup
Exposure source
Distance between exposed object and exposure source 1 cm
Setup magnetic field was generated by a Teflon coil (length 70 mm, diameter 30 mm) which was coiled by enameled copper wire; a soft iron core (diameter of 8 mm) was placed in the middle of the cylinder, so it represents a single unit; magnet was connected to the power amplifier and the frequency generator, which enabled generation of different waveforms; sine wave and square wave current (0.3 A, 12 V, 50 Hz) flows through the magnet inducing MF of 19 mT on the top of the core; an oscilloscope was used to check the waveform accuracy; magnet was placed 1 cm from the left antenna of the beetle
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 2 mT mean measured - at head surface

Exposure 3

Main characteristics
Frequency 50 Hz
Type
Waveform
  • rectangular
Exposure duration continuous for 5, 10, and 15 minutes
Additional info square wave
Additional info rise time of the square was about 2.2 ms, the root mean of the amplitude of the square signal was 630 mV, width of impulses was 5 ms, and period was 20 ms
Exposure setup
Exposure source
  • same setup as in E2
Distance between exposed object and exposure source 1 cm
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 2 mT mean measured - at head surface

Exposed system:

Methods Endpoint/measurement parameters/methodology

Investigated system:
Investigated organ system:
Time of investigation:
  • before exposure
  • during exposure
  • after exposure

Main outcome of study (acc. to author)

No significant influence of the static magnetic field on the neuronal population activity in the antennal lobe was observed.
Exposure to extremely low frequency magnetic fields induced significant changes in the slow (1-2 Hz, 4-8 Hz) and in the fast (64-128 Hz) frequency bands of the local field potentials from the antennal lobe compared to the corresponding baseline: In the second experiment (sine wave), the relative wavelet energy in the range of 1-2 Hz was significantly decreased after the repeated and prolonged exposures, while it was increased in the 4-8 Hz frequency band immediately after the first exposure as well as after repeated exposures. In the third experiment (square wave), the relative wavelet energy of the 4-8 Hz frequency band was significantly increased immediately after the first exposure as well as after repeated exposures. In the 1-2 Hz range, the relative wavelet energy was significantly decreased only after repeated exposures and in the 64-128 Hz range it was significantly decreased immediately after the first exposure and after repeated exposures.
The authors conclude that extremely low frequency magnetic fields could affect the neuronal population activity in the antennal lobe of Morimus funereus and that wavelet transformation presents a valuable tool for measuring these changes.

Study character:

Study funded by

Related articles