Formation of the Looming-evoked Innate Defensive Response during Postnatal Development in Mice / 神经科学通报·英文版

Environmental threats often trigger innate defensive responses in mammals. However, the gradual development of functional properties of these responses during the postnatal development stage remains unclear. Here, we report that looming stimulation in mice evoked flight behavior commencing at P14-16 and had fully developed by P20-24. The visual-evoked innate defensive response was not significantly altered by sensory deprivation at an early postnatal stage. Furthermore, the percentages of wide-field and horizontal cells in the superior colliculus were notably elevated at P20-24. Our findings define a developmental time window for the formation of the visual innate defense response during the early postnatal period and provide important insight into the underlying mechanism.

Response of cells in the superior colliculus during performance of a spatial attention task in the macaque

Previous studies have reported that superficial layer cells in the superior colliculus (SC) give an enhanced response to a stimulus when it is the target for an eye movement. However, in a peripheral detection paradigm, no such enhancement was found when a stimulus was attended, in the absence of an eye movement. Inasmuch as behavioral studies have found attention deficits in the absence of eye movements following SC lesions or deactivation, we investigated this issue in a paradigm that is very sensitive to effects of attention. In a matching-to-sample paradigm, a sample stimulus was presented at one location followed by a brief test stimulus at that (relevant) location and a distracter at another (irrelevant) location. While maintaining fixation, the monkey indicated whether the sample and the test stimulus matched, ignoring the distracter. The relevant and irrelevant locations were switched from trial to trial. SC cells in the superficial layers tended to give enhanced responses when the attended test stimulus was inside the receptive field compared to when the (pysically identical) distracter was inside the field. We found that responses to attended targets in the receptive field were larger than to physically identical, but ignored, distracter stimuli. These effects were found only in an "automatic" attentional cueing paradigm, in which a peripheral stimulus explicity cued the animal as to the relevant location in the receptive field. No attentional effects were found in a "central"or "cognitive"cueing paradigm, in which the monkey had to learn the relevant location in a given block of trials. The larger responses to attended targets in the automatic cueing paradigm appeared to be due to a sustained elevation of cells'baseline activity when attention was directed to the receptive field, as well as a transient enhancement of the target response. Thus, responses of SC cells appear to be modulated by directed attention, even in absence of eye movements, probably reflecting the properties of cortical cells projecting to the SC.

Patters of nitric oxide synthase expression in the developing superior colliculus

Nitric oxide (NO) is synthesized in cells of both the central and peripheral nervous system and has been implicated in several forms of synaptic plasticity. The enzyme that produces NO, nitric oxide synthase (NOS), can be visualized in the brain by the reduced nicotinamide adenine dinucleotide phosphate diaphorase histochemistry technique (NADPH-d). We have used NADPH-d activity to detect the presence of NOS-positive cells in the developing rat superior colliculus. Our results showed that NOS is present in cells and neuropil in the developing and adult rat superior colliculus. The first NOS-positive cells appeared at postnatal day 7 and were weakly stained. The number and intensity of the NOS-positive cells increased progressively during the following days reaching a maximum at postnatal day 15. By the end of the third postnatal week, both the number and intensity of stained cells showed an adult-like pattern. The NOS-positive cells showed a Golgi-like mosphology and we have found that all cell types present in the superior colliculus express the enzyme. The expression of NOS by tectal cells parallels the functional development of the retino-collicular and cortico-tectal projections and suggest that nitric oxide synthase-positive cells might be involved in this process. In this review we highlighted some of the recent descriptions of the expression of NOS in the mammalian visual system with emphasis in the superior colliculus and correlate these findings with several developmental events taking place in this structure.

Intraretinal neurotrophic activity prevents the degeneration of ganglion cells in retinal explants

The degeneration of ganglion cells was studied in neural retina explanted from the eyes of newborn rats. The ganglion cells were detected by the presence of retrogradely transported horseradish peroxidase injected into the superior colliculus. The time course of cell death among the axotomized ganglion cells in the explants was similar to that found in vivo after axotomy in neonatal rats. The effect of culture media conditioned with retinal cells from either newborn rats or chick embryos was tested on the survival of ganglion cells in the explants. Both conditioned media increased 2- to 3-fold the survival of rat retinal ganglion cells after 2 days in culture. The data show that soluble trophic factors released by retinae of distinct species can influence the survival of ganglion cells within their histotypic microenvironment

Accessory optic-pretectal interactions in the pigeon

This electrophysiological study analyzes the influence of the nucleus of the basal optic root (nBOR) of the avian accessory optic sustem on units within the lentiform nucleus (LM), which is the avian equivalent of the pretectal nucleus of the optic trat. A prominent depression of the spontaneous firing rat of neurons within the LM occurred following electrical stimulation of the ipsilateral nBOR. A close correlation was also found between the directional selectivity of LM units and the apparent displacements generated by rotations of the head around the horizontal semicircular canal axis. This is consistent with a possible rolo of the LM in the coordinate transformation from visual imputs to a vestibular referense system

Interactive effects of deafferentation and target removal on cell death in the parabigeminal nucleus of developing rats

This study was designed to test the effects of simultaneous deafferentation and target removal on cell death in the parabigeminal nucleus. Bilateral lesions of the superior colliculus were made in newborn rats and neuron death was evaluated in the dorsal (PBd), middle (PBm) and ventral PBv) division of the nucleous. When the results of the bilateral lesions were compared with the effects of unilateral lesions reported in a previous study simultaneous deafferentation and tarfet removal were found to produce an increase in the rate of cell death greater than, and with a time course differing from that, predicted by the sun of the separate effects of removal of afferents or targets. These data suggest that the trophic effects of afferents and targets interact during the period of naturally occurring cell death

Development of abnormal lamination and binocular segregation of retinal afferents onto the rat superior colliculus

Unilateral optic tract lesions made in newborn rats abnormal retinotectal pathways on the opposite side. The present in investigation was designed to study the development of the abnormal retinal projections in the superior colliculus using antomical tracing methods. The aberrant uncrossed retinotectal pathway develops within the first postnatal week. In spite of this, the retration of the crossed projection, wich indicates binocular segregation, is of late onset. This indicates that the induced segregation of retinal imputs is not dependent on regressive events such as ganglion cell death and terminal field retraction. These data and the results of lid-suture experiments are consistent with a role for spontaneous retinal activity in the regulation of the plasticity of retinal projections to the rat superior colliculus

Survival of retinal ganglion cells in vitro: the effect of conditioned medium from retinal cell aggregates

The time course of degeneration of retinal ganglion cells was studied in vitro. We used the retinae of newborn hooded rats retrogredely labeled with horseradish peroxidase injected bilaterally into the conditined medium either from aggregates or from explants of retinal cells on the survival of the ganglion cells. Both conditioned media approximately doubled the survival of ganglion cells after 48-72 h in culture. Our data are consistent with the hypotesis that retinal cells produce soluble trophic factors that influence ganglion cell survival

The projection of GABAergic neurons of the medial terminal accessory optic nucleus to the pretectum in the rat

Large numbers of neurons were retrogradely labeled in both the dorsal and ventral medial terminal nucleous (MTN) after fluoro-gold injections into the rat pretectal nucleus of the optic tract/dorsal terminal nucleus (NOT/DTN). Fluorescence immunocytochemistry for GABA in the same brains revealed GABA-positive neurons distributed mainly in the dorsal MTN. Approximately half of all the GABAergic neurons in the MTN were double-labeled. Therefore, GABAergic neurons comprise a significant component of the MTN-NOT-DTN projection which most likely inhibits the pretectal pathway mediating horizontal optokinetic nystagmus

Evidence of an extended representation of the visual field in the superior colliculus of the rabbit (Oryctolagus cuniculus).

Electrophysiological mapping using multiple-unit criteria was employed to study the representation of the visual field in the superior colliculus of the rabbit. It was found that the contralateral superior colliculus of the rabbit has an extended representation beyond the representation of the zero vertical meridian or the line of decussation in the geniculostriate system. The amount of extended representation in the contralateral superior colliculus is coextensive with the extent of visual field represented ipsilaterally in areas 17 and 18 of the visual cortex. In agreement with previous findings, the representation of the visual field on the superior colliculus is extremely distorted. Finally, no evidence of an ipsilateral input can be produced.