The influence of intracortical inhibition on the response adaptation of visual cortical neurons remains in debate.To clarify this issue,in the present study the influence of surround suppression evoked through the local inhibitory interneurons on the adaptation effects of neurons in the primary visual cortex(V1) were observed.Moreover,the adaptations of V1 neurons to both the high-contrast visual stimuli presented in the classical receptive field(CRF) and to the costimulation presented in the CRF and the surrounding nonclassical receptive field(nCRF) were compared.The intensities of surround suppression were modulated with different sized grating stimuli.The results showed that the response adaptation of V1 neurons decreased significantly with the increase of surround suppression and this adaptation decrease was due to the reduction of the initial response of V1 neurons to visual stimuli.However,the plateau response during adaptation showed no significant changes.These findings indicate that the adaptation effects of V1 neurons may not be directly affected by surround suppression,but may be dynamically regulated by a negative feedback network and be finely adjusted by its initial spiking response to stimulus.This adaptive regulation is not only energy efficient for the central nervous system,but also beneficially acts to maintain the homeostasis of neuronal response to long-presenting visual signals.
氯胺酮(ketamine)和乌拉坦(urethane)对神经细胞活动的影响大小和机制尚存在争议。c-fos是刺激依赖表达的立早基因(immediate early genes),其表达量可反应神经细胞活动的强弱。该研究通过免疫组织化学方法比较观察乌拉坦和盐酸氯胺酮急性麻醉对猫初级视皮层细胞中刺激依赖的c-fos蛋白表达的影响。结果显示,氯胺酮组和乌拉坦组初级视皮层各层神经元密度与对照组无显著差异;乌拉坦组视皮层c-fos蛋白免疫阳性细胞密度和免疫反应强度与对照组无显著差异;而盐酸氯胺酮组视皮层细胞中c-fos蛋白免疫阳性细胞密度及免疫反应强度均显著降低。即氯胺酮对视皮层细胞反应的抑制作用较强,而乌拉坦的抑制作用不显著。
The mean firing rate of visual cortical neurons is reduced after prolonged visual stimulation, but the underlying process by which this occurs as well as the biological significance of this phenomenon remains unknown. Computational neuroscience studies indicate that high-frequency bursts in stimulus-driven responses can be transmitted across synapses more reliably than isolated spikes, and thus may carry accurate stimulus-related information. Our research examined whether or not adaptation affects the burst firing property of visual cortical neurons by examining changes in the burst firing changes of V1 neurons during adaptation to the preferred visual stimulus. The results show that adaptation to prolonged visual stimulation significantly decreased burst frequency (bursts/s) and burst length (spikes/burst), but increased burst duration and the interspike interval within bursts. These results suggest that the adaptation of V1 neurons to visual stimulation may result in a decrease of feedforward response gain but an increase of functional activities from lateral and/or feedback connections, which could lead to a reduction in the effectiveness of adapted neurons in transmitting information to its driven neurons.
Rui-Long LIUKe WANGJian-Jun MENGTian-Miao HUAZhen LIANGMin-Min XI
