Spatio-temporal Receptive Field Properties Of Cells In The Rat Lateral Geniculate Neurons

ObjectiveTo study the development of spatio-temporal frequency tuning in rats lateral geniculate nucleus (LGN) in various ages and compare the physiological properties and LFP of cells with results from the non-deprived layers and deprived layers of the LGN in rats.Methods1. Twenty Wistar rats were collected and divided into14-16day group,20-22day group,27-30day group,60day group according to the different ages after open eyes and5rats for each group. Extracellular single neuron recording was carried out to study the spatio-temporal receptive field properties of LGN by sinusoidal gratings visual stimuli. The dynamic change of spatio-temporal receptive field properties of neurons with development of Wistar rats was evaluated.2. Extracellular single neuron recording was carried out to evaluate the physiological properties and LFP of cells with sinusoidal gratings visual stimuli between the non-deprived layers and deprived layers of the LGN in rats monocularly deprived from birth for up to3weeks.Results1.The differences between band-pass and low-pass distribution of temporal frequency or spatial frequency of rat LGN were not statistically significant(χ2＝0.68,0.47,P>0.05). The optimal temporal frequency of receptive field in rat LGN went up its maximum value until60-day old in Wistar rats. The mean optimal temporal frequency of neurons in the four different age groups were (2.5±1.3),(2.6±1.2),(2.6±1.1),(3.6±1.1) cycles/s respectively with the significant difference among the4groups(F=4.53, P<0.05), and that in14-16day group,20-22day group,27-30day group was significantly lower than60days group (q=1.2、1.2、1.3, P<0.05). No significant differences were seen among14-16day group,20-22day group,27-30day group (P>0.05). The optimal spatial frequency values in the four groups were0.03、0.03、0.035、0.04cycles/deg respectively without comparable difference (F=0.34, P>0.05), spatial frequency resolution were (0.26±0.15)、(0.26±0.15)、(0.28±0.13)、(0.29±0.14) cycles/deg, respectively without comparable difference (F=0.50, P>0.05). The temperal and spatial bandwidth values in various age groups were not statistically significant among the four groups(F=0.22, P>0.05; F=1.23, P>0.05). The directional indexes remained stable between age groups, as an analysis of variance revealed no significant difference (χ2＝0.26, P>0.05).Contrast thresholds decreased with age to reach a mean value of (19.4±17.5)%at adulthood, a variation which is significant (F=3.2, P<0.05). In fact, contrast thresholds were significantly lower between14-16day group and20-22day group and adults, as well as between27-30day group and adults(g=11.98、8.30、7.90, P<0.05).2. The number of modulated and unmodulated neurons showed no significant difference between deprived and nondeprived groups (χ2=0.00, P>0.05). The optimal temporal frequency of receptive field in rat LGN were (2.5±1.3) cycles/s and (2.5±1.4) cycles/s in nondeprived group and deprived group respectively with no significant difference (0.013, P>0.05).The LFP gamma power in nondeprived group and deprived group were (10.48±5.01) V＾2*e-009and (11.44±4.72) V＾2*e-009respectively with significant difference (t=2.93, P<0.05).The optimal spatial frequency of receptive field in both groups was0.03(medium),the spatial resolution frequency were (0.27±0.13) cycles/deg and (0.26±0.14) cycles/deg in nondeprived group and deprived group respectively with no significant difference (χ2=0.34,t=1.23, P>0.05).The LFP gamma power in nondeprived group and deprived group were (16.73±7.34) V＾2*e-009and (7.27±3.0) V＾2*e-009respectively with a significant difference (T=8.5, P<0.05)。Conclusions1. Some functions, such as spatial frequency, orientation and directional tuning of spatio-temporal properties of rats LGN receptive field, are already mature two days (P16) after eye opening whereas others, including temporal frequency tuning and contrast thresholds, continued to improve and attained maturity, which may be related to its functional visual pathway.2.The Spatio-temporal properties of cells in the deprived layers of the LGN in rats were not affected by deprivation. However, The power of the local field potential (LFP) deprived layers showed obviously more decreased than in nondeprived layers. Deprivation may cause a profound defect on the physiological properties of LGN in the rat.