Abstract
Achromatopsia (ACHM) is an inherited autosomal recessive disease lacking cone photoreceptors functions. In this study, we characterize the time-frequency representation of the full-field electroretinogram (ffERG) component oscillatory potentials (OPs), to investigate the connections between photoreceptors and the inner retinal network using ACHM as a model. Time-frequency characterization of OPs was extracted from 52 controls and 41 achromat individuals. The stimulation via ffERG was delivered under dark-adaptation (DA, 3.0 and 10.0 cd·s·m−2) to assess mixed rod-cone responses. The ffERG signal was subsequently analyzed using a continuous complex Morlet transform. Time-frequency maps of both DA conditions show the characterization of OPs, disclosing in both groups two distinct time-frequency windows (~70–100 Hz and >100 Hz) within 50 ms. Our main result indicates a significant cluster (p < 0.05) in both conditions of reduced relative power (dB) in ACHM people compared to controls, mainly at the time-frequency window >100 Hz. These results suggest that the strongly reduced but not absent activity of OPs above 100 Hz is mostly driven by cones and only in small part by rods. Thus, the lack of cone modulation of OPs gives important insights into interactions between photoreceptors and the inner retinal network and can be used as a biomarker for monitoring cone connection to the inner retina.
Highlights
Achromatopsia (ACHM) is a rare autosomal recessive inherited disease with an incidence of 1 in 30,000 [1,2,3]
The purpose of this study is to investigate the characteristics of retinal components elicited by light stimulation after dark adaptation in standard full-field ERG recordings in healthy controls and ACHM individuals using a complex Morlet wavelet transform
DisIcnusaslliotinme-frequency plots, it is possible to observe two main clusters, one occurring itnrerliaaagannrhlsgniTtfeeoohrerr(exa>mmtps1aa.to5ulAs0lodpusHwyorrepzeea)rupii.mnfloIranreetstiqdcepouodrntteeooinvancpcnihoyitdcahu(res5ican0orpc–enitr1nsedee0rdviai0tizirivoHeociuhndtzsh,su)telaahaintfletesfdErpdwaRtrihtfeiGuftesehresrseneeAig[ccn7Coent,n8aHotd,lif3Mmit6onw]ce,utc-ohefusrelioreenrstcqgiictnmuirlagoeleanplcataochotnymeyrdsrspwiaafolrttielenaoxmqdghuMeoiidcegwoanihulrscelmfyerehtfadarawtevonuqmeadruvebaheseienilnogeecsftnhy achromats show normal or near-normal rod-mediated responses when stimulated in dark adaptation, while functional cone signals are absent when stimulated in the light-adapted condition due to lack of functional cone photoreceptors
Summary
Achromatopsia (ACHM) is a rare autosomal recessive inherited disease with an incidence of 1 in 30,000 [1,2,3]. ACHM is due to congenital dysfunction of the cone photoreceptors and biallelic mutations in six different genes (i.e., CNGA3, CNGB3, GNAT2, PDE6H, PDE6C, and ATF6) that are responsible for >90% of the cases [4]. Electrophysiological recordings show that achromats have notably reduced or unmeasurable cone responses following full-field photopic stimulation, and usually near to normal responses of rods in the scotopic assessment [7,8]. Full-field electroretinography (ffERG) is a powerful non-invasive tool that allows for the assessment of retinal function in response to stimuli of different temporal and spectral luminance characteristics. The major light-driven components are represented by a-wave, b-wave, oscillatory potentials (OPs), and flicker responses of the standardized ffERG [11]. Filtering the signal makes it possible to extract the OPs, which are rhythmic fast oscillations identified in high-frequency bands (75–300 Hz), raising between the a-wave and the ascending phase of the b-wave [11]
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