Re-examining ‘established’ neural connections using peristimulus frequencygram

Türker K. S. , Binboğa E., Atış Tekeli E. S.

Society for Neuroscience, Illinois, United States Of America, 17 October 2009

  • Publication Type: Conference Paper / Unpublished
  • City: Illinois
  • Country: United States Of America


Title:Re-examining ‘established’ neural connections using peristimulus frequencygram
Location:South Hall A
Presentation Time:Sunday, Oct 18, 2009, 9:00 AM -10:00 AM
1Ege Univ., 2Biophysics, 3Ctr. for Brain Res., 4Bioengineering, Ege Univ., Izmir, Turkey; 5Ctr. for Brain Res., Izmir, Turkey; 6Dept. of Physical Therapy, Chiangmai Univ., Chiangmai, Thailand; 7Dept. of Prosthetic Dent., Kaunas Univ. of Med., Kaunas, Lithuania
Abstract:Background: Using regularly discharging motoneurons in slices, it has been recently shown that the classical methods for estimating synaptic connections of neurons contain inherent errors. These errors can be minimized by plotting the same data using instantaneous discharges of neurons against the timing of the injected current (representing post stimulus potentials, PSPs). In this study, we aimed to study several reflexes using the new approach and find out whether the previously ‘established’ neural pathways contain errors.
Methods: Once the informed volunteers signed the consent forms, bipolar wire electrodes are inserted into one of the following muscles: tibialis anterior, soleus, masseter and first dorsal interosseous. Subjects contracted their muscles with the aid of audio feedback from the discharges of one selected motor unit from the muscle. While the subject controlled the discharge rate of the unit, sensory afferents around these muscles were either electrically or mechanically activated. Responses of the muscle and its motor units to the stimuli were converted into rectified averaged surface electromyogram (SEMG), peristimulus time histogram (PSTH) and peristimulus frequencygram (PSF).
Results: We found that the initiation of the timing of inhibitory connections can be reliably displayed with the reduction in the spike counts in the PSTH. However, the duration of the inhibitory period needs to be determined using PSF as the end of an inhibition is signified as a reduction in the discharge rate in the PSF which appears as a rebound peak in the PSTH records. Similarly, duration of excitation is also better indicated using the PSF as the falling phase of excitation appears like inhibition in the PSTH (lower number of spikes). The PSF on the other hand indicates that this phase is the continuation of the excitation as the spikes in this period fire at higher discharge rates than the prestimulus discharge rate. Rectified average SEMG gave similar results to PSTH though it was less precise.
Discussion and Conclusions: This study confirms the predictions from the slice work that to indirectly estimate synaptic connections to motoneurons, one needs to use both the classical methods and the PSF in combination.
Türker K S, Powers RK. Black box revisited: a technique for estimating postsynaptic potentials in neurons. Trends Neurosci. 2005; 28(7): 379-386.
Disclosures: K.S. Turker, None; O. Prasartwuth, None; E. Binboga, None; E.S. Atis, None; M.C. Kahya, None; U. Yavuz, None; A. Sendemir-Urkmez, None; P. Ugnius, None.