Age‐associated changes in the equine flash visual evoked potential
Fonte: Lena Ström, Måns Michanek, Björn Ekesten
Electrode positions used for flash visual evoked potentials (FVEP) recordings. Red—active electrode at Pz-45; green— ground electrode; black—reference electrode
Objective:To investigate age‐associated changes of flash visual evoked poten-tials (FVEPs) in sedated horses.Animal studied:Twenty‐eight clinically healthy Standardbred Warmblooded trot-ters, aged 36 hours to 28 years.Procedures:Light‐adapted FVEPs and FERGs were recorded (An‐vision RETI-port, Roland‐consult, Germany) in response to flash stimuli. Sedation wasobtained using alpha‐2‐agonists intravenously. Akinesia of the eyelids wasinduced and pupils were dilated.Results:Reproducible FVEPs and FERGs were readily recorded from all foalsand horses. The FVEP waveform included up to four positive components (P1‐P5) and two negative components (N1 and N2) and FVEP waveform morphologywas similar across all age groups. Some differences in peak times and amplitudesassociated with increasing age were observed. FVEP amplitudes recorded fromnewborn foals were well above the amplitudes observed in normal adult horsesand FVEP peak times were somewhat shorter. In adult horses, a significantincrease in P4 peak time and a gradual decrease in amplitudes, mainly for N2P4,were seen across the life‐span.Conclusions:The overall equine FVEP waveform was similar across the normallife‐span of the horse in our cross‐sectional study. We found that the visual sys-tem of the foal seems to be well developed already at birth. Furthermore, ourresults showed a decrease in amplitudes and increase in some peak times withincreasing age. We recommend that age‐matched controls should be used whenevaluating foals and young horses in clinical practice, whereas horses over theage of three years can be compared to other adult horses.