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Wayne Tschetter, Gubbi Govindaiah, William Guido, Cristopher Niell; Development of receptive field properties in mouse dLGN is accompanied by changes in excitatory and inhibitory retinal convergence. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):3252.
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© ARVO (1962-2015); The Authors (2016-present)
To determine how receptive fields and their underlying circuits develop in the dorsal lateral geniculate nucleus (dLGN) of the thalamus.
In vivo multichannel extracellular recordings were made in dLGN of wild type and transgenic (beta-3-null) mice, which lack retinogeniculate remodeling. Recordings were performed in awake head fixed animals beginning at eye opening. Diverse visual stimuli were used to map the spatiotemporal structure and response properties of receptive fields across development. To begin to understand the underlying circuitry that accompanies changes in receptive field properties we made in vitro recordings of excitatory and inhibitory synaptic responses by applying electrical stimulation to the optic tract in an acute thalamic slice preparation that preserves retinal afferents and intrinsic inhibitory circuitry within dLGN
We discovered a 3-fold decrease in receptive field size and a corresponding decrease in spot size preference during the first week after eye opening (P14-21). Inhibition was measured as suppression of responses to a full field flash and resulted in a 2-fold increase as receptive fields refined. In addition to canonical receptive fields, we saw a 20% increase in orientation selective responses. In contrast to the significant refinement of spatial receptive field properties, modulation of geniculate neurons by behavioral state was present early, as verified by a significant increase in the proportion of burst firing when an animal was stationary compared to running. The spatiotemporal structure and response properties of RGCs were mature during the retinal afferent refinement window. Between P14 and P21 there was about a 2.5 fold decrease in excitatory convergence (from 5-2 inputs) with little change in peak EPSC amplitude (1nA). By contrast, IPSC exhibited a 2-fold increase (2 to 4 inputs) in convergence with no change in the peak amplitude
1) dLGN receptive fields in mouse mature over the first week after eye opening. This is seen as a decrease in the size of spatial structure and spot size preference as well as an increase in size suppression. 2) Concurrent excitatory and feed-forward inhibitory retinal convergence likely mediate refinement of receptive fields.
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