Population Activity Changes During A Trial-to-trial Adaptation Of Bullfrog Retinal Ganglion Cells

In the visual system, retina is the first stage of visual informationprocessing. Light is received by photoreceptors and is transmitted intoneural electrical signals which are processed by retinal circuits. Retinalganglion cells, the output units of retina, then convey the neural signals tocentral visual system via action potentials. Constrained by physiologicalstructure, limited metabolic energy and so on, retina adopts effectivestrategies to encode the complicated visual scenes. Neurons adaptdynamically to the varied environmental light, adjusting their responsesand sensitivities to light properties such as mean intensity and contrast.On the other hand, neighboring neurons on the retina tend to fireconcertedly, which has also been considered to participate in the encodingof visual information. In the present study, we investigated the populationneuronal activities of bullfrog retinal ganglion cells during a"trial-to-trial" adaptation to repetitive light-ON and-OFF stimulus, basedon the recording via multi-electrode system. The main results incude:(1) Under the repetitive stimulus, thetrial-to-trial adaptation was observed;(2) During such adaptation progress,the strength of correlation activities between neurons was decreased, andshowed positive relationship with the adaptation;(3) The multi-neuronalgrouping patterns, which was analysed by a method based on informationcompressing, were also weakened during the adaptation.(4) Adaptationbehavior was different for ON-and OFF-pathway, with OFF-responsesadapting much stronger.These results indicated that the trial-to-trial adaptation wasaccompanied by the decrease of population neuronal activities, reflectingthe population adaptation and suggesting the modulation of the lateralconnection in the retinal neuronal network. In addition, the differentperformance in ON-and OFF-response suggested that the possiblemechanisms controlling the trial-to-trial adaptation might involve bipolarcells and/or their synapses with other neurons. And the strongeradaptation in the OFF-response might reflect the requirement to avoidmore possible saturation in the OFF-circuit.