Absence Of Visual Experience Research Articles

Development of cortical orientation selectivity in the absence of visual experience with contour

Visual cortical neurons are selective for the orientation of lines, and the full development of this selectivity requires natural visual experience after eye opening. Here we examined whether this selectivity develops without seeing lines and contours. Juvenile ferrets were reared in a dark room and visually trained by being shown a movie of flickering, sparse spots. We found that despite the lack of contour visual experience, the cortical neurons of these ferrets developed strong orientation selectivity and exhibited simple-cell receptive fields. This finding suggests that overt contour visual experience is unnecessary for the maturation of orientation selectivity and is inconsistent with the computational models that crucially require the visual inputs of lines and contours for the development of orientation selectivity. We propose that a correlation-based model supplemented with a constraint on synaptic strength dynamics is able to account for our experimental result.

Perceptual Organization of Visual Structure Requires a Flexible Learning Mechanism.

Bhatt and Quinn (2011) provide a compelling and comprehensive review of empirical evidence that supports the operation of principles of perceptual organization in young infants. These principles, which are largely synonymous with the Gestalt laws of visual perception, raise a number of important, and as yet unanswered questions. Bhatt and Quinn tackle some of these questions and propose several mechanisms by which infants progress from a few principles of perceptual organization to the full set of principles that operate in adults. The first question is about origins: Are any of the principles of perceptual organization present at birth in the absence of visual experience? Although the Gestalt psychologists assumed that all the principles of perceptual organization were innate, presumably because of evolutionary pressures to ensure their presence in the species, these early 20th century psychologists did not have the methods required to measure the operation of these principles in young infants. Bhatt and Quinn (2011) summarize evidence that by 3–4 months of age there are at least two such principles of perceptual organization in operation: common motion and good continuation. Unfortunately, these data from 3- to 4-month-olds do not confirm a nativist origin because 3–4 months of postnatal visual experience provides an enormous opportunity for the learning of these principles. Demonstrations of

Visual Deprivation Alters the Development of Cortical Multisensory Integration

It has recently been demonstrated that the maturation of normal multisensory circuits in the cortex of the cat takes place over an extended period of postnatal life. Such a finding suggests that the sensory experiences received during this time may play an important role in this developmental process. To test the necessity of sensory experience for normal cortical multisensory development, cats were raised in the absence of visual experience from birth until adulthood, effectively precluding all visual and visual-nonvisual multisensory experiences. As adults, semichronic single-unit recording experiments targeting the anterior ectosylvian sulcus (AES), a well-defined multisensory cortical area in the cat, were initiated and continued at weekly intervals in anesthetized animals. Despite having very little impact on the overall sensory representations in AES, dark-rearing had a substantial impact on the integrative capabilities of multisensory AES neurons. A significant increase was seen in the proportion of multisensory neurons that were modulated by, rather than driven by, a second sensory modality. More important, perhaps, there was a dramatic shift in the percentage of these modulated neurons in which the pairing of weakly effective and spatially and temporally coincident stimuli resulted in response depressions. In normally reared animals such combinations typically give rise to robust response enhancements. These results illustrate the important role sensory experience plays in shaping the development of mature multisensory cortical circuits and suggest that dark-rearing shifts the relative balance of excitation and inhibition in these circuits.

Visual cortex is rescued from the effects of dark rearing by overexpression of BDNF.

Visual deprivation such as dark rearing (DR) prolongs the critical period for ocular dominance plasticity and retards the maturation of gamma-aminobutyric acid (GABA)ergic inhibition in visual cortex. The molecular signals that mediate the effects of DR on the development of visual cortex are not well defined. To test the role of brain-derived neurotrophic factor (BDNF), we examined the effects of DR in transgenic mice in which BDNF expression in visual cortex was uncoupled from visual experience and remained elevated during DR. In dark-reared transgenic mice, visual acuity, receptive field size of visual cortical neurons, critical period for ocular dominance plasticity, and intracortical inhibition were indistinguishable from those observed in light-reared mice. Therefore, BDNF overexpression is sufficient for the development of aspects of visual cortex in the absence of visual experience. These results suggest that reduced BDNF expression contributes to retarded maturation of GABAergic inhibition and delayed development of visual cortex during visual deprivation.

Auditory substitution of vision: pattern recognition by the blind

AbstractPattern recognition in a computer environment was investigated in 6 early blind and 6 blindfolded sighted subjects using auditory substitution of vision. Subjects had to scan visual patterns displayed on a PC screen by moving the pen of a graphics tablet, which lead to corresponding displacements of the cursor on the screen. A small screen area centered on the pointer was then translated into sounds according to a visual‐auditory transcription code. Subjects were trained to learn this code during 12 one‐hour sessions. Performance of both groups significantly increased with practice. This indicates that mental representations of visual patterns can be acquired through the auditory channel, even in the absence of visual experience. Moreover, blind subjects performed significantly better than sighted subjects did. This could be interpreted as a result of partial compensation for their loss of vision. Pattern recognition in a computer environment is thus possible using a fairly natural vision‐to‐audition coding scheme. Copyright © 2001 John Wiley & Sons, Ltd.

Self-organization model on receptive field of neuron with asymmetric time window of synaptic modification

The spatial-temporal response properties of some simple neurons in visual pathway arise basically prior to birth. In the absence of visual experience, how do these neurons develop in visual system? Based on Wimbauer network with delay, a four-layer feed-forward network model is proposed, which is characterized by modifying the Hebb learning rule through introducing the asymmetric time window of synaptic modification found recently in neurobiology. The model can not only generate by self-organization more diversified spatial-temporal response characteristics of neuronal receptive field than earlier models but also provide some explanations for the possible mechanism underlying the development of receptive fields of contrast polarity sensitive neurons found in visual system of vertebrate. Thus the proposed model may be more widely applicable than Linsker model and Wimbauer model.

Influence of visual experience deprivation on the postnatal development of the microvascular bed in layer IV of the rat visual cortex

Cerebral vascular density is correlated with metabolic demands, which increase in highly active brain areas. External inputs are an essential requirement in the modeling of the visual cortex. Experience-mediated development is very active during the first postnatal month, when congruous blood supply is needed. We studied the development of visual cortex vascularization in relation to experience, comparing rats raised in darkness with rats reared in normal conditions. Vascular density, vascular area and their ratio vs. neuronal density were calculated. Conventionally stained semi-thin sections were used to measure the vascular area by computer assisted morphometry. Animals from both groups were sampled at 14, 21, and 60 days postnatal (dpn). We found a significantly lower density of vessels and neurons as well as a smaller vascular area in dark-reared adult rats while no differences were founded at the other ages. Our results also show no differences between the ratio of vessels/neuron, and vascular area/neuron, between both groups. The absence of visual experience causes decrease of cortical activity which correlates with lower vessels density and vascular area, without their ratio/neuron being affected.

The curvature of human arm movements in the absence of visual experience.

It has been suggested that the spatial path of the hand is an important controlled feature of normal human arm movements and that the desired path is a straight line through external space. Recent experiments have suggested that distortions in visual perception of external space may lead to errors in its representation and thus influence the curvature of movements. The movements of blind and normal blind-folded subjects were therefore compared in a task requiring point-to-point hand movements in six directions across a horizontal worktop. Movement curvature varied with direction in both groups but was significantly higher for the blind-folded control subjects. Thus, the normals' distorted visual experience of straight lines in some orientations may lead them to make curved movement paths. The perception of curvature was also tested in the two groups in a task in which they traced the curved edge of a ruler. The blind group were slightly better at this task, although the difference was not significant. We conclude that visual experience influences point-to-point hand movements, leading to higher curvature for movements made in the fronto-parallel plane by sighted subjects due to visual distortions. These data therefore support the hypothesis that the spatial path followed by the hand is influenced by sensory inputs and is a controlled feature of human reaching movements. The data argue against the hypothesis that movement curvature is a result of optimising only the dynamics of the limb control.

Glutamatergic and GABAergic synaptic currents in ganglion cells from isolated retinae of pigmented rats during postnatal development

This study was aimed at characterizing the earliest phases of synaptogenesis in the mammalian retina. Spontaneous activity of ganglion cells in the isolated superfused retina was used as an indicator for the functionality of synaptic connections. Retinal ganglion neurons (RGNs) were identified by location of their somata in the ganglion cell layer (GCL) and by their ability to generate large (> 500 pA) voltage-activated sodium currents. Spontaneous spiking was found in many RGNs prior to cell perfusion. Between postnatal day (P) 1 and 18, a total of 195 RGNs was tested for light-induced currents, conductance changes in response to exogenous glutamate (Glu) and γ-aminobutyric acid (GABA), and depolarizing or hyperpolarizing synaptic activity. The vast majority of the material was derived from RGNs at day P5. Whole-cell ion currents were always sampled at somatic sites, using either conventional or perforated patch whole-cell recordings. On day P5, 5% of tested RGNs ( n = 73) were already responsive to light stimulation. A higher percentage of cells (23%, n = 187) generated spontaneous depolarizing currents that were regarded as glutamatergic excitatory postsynaptic currents (EPSCs), since (1) they were blocked by Glu antagonists, (2) they conformed to the Na +/Cs + equilibrium potential, (3) and they displayed a time course characteristic of glutamatergic EPSCs. The mean EPSC amplitude was 19.0 pA (S.D. 11.83 pA). Amplitude distributions were fitted by multiple Gaussian equations rendering a quantal size of 6.6 to 9.1 pA at a holding voltage ( V h) of −70 mV (driving force about 70 mV). Spontaneous EPSCs were never observed under condition of Ca 2+-free solutions, but they persisted in the presence of tetrodotoxin. Bath application of quisqualate (500 μM) consistently increased EPSC frequencies. In contrast to the relatively high percentage of RGNs generating spontaneous EPSCs, very few RGNs at P5 (3%, n = 187) displayed inhibitory postsynaptic currents (IPSCs), although by that time all tested RGNs ( n = 14) were responsive to both exogenous Glu and GABA. These results indicate that in the postnatal rat retina development of excitatory synapses precedes the maturation of inhibitory afferents. Excitatory inputs to RGNs were to some extent functional before the animals opened their eyes. Glutamatergic synaptic activity may, thus, play an important role in shaping visual connections in the absence of visual experience.

Effect of neonatal unilateral enucleation on the development of orientation selectivity in the primary visual cortex of normally and dark-reared kittens.

The developmental properties of 573 neurones have been investigated in the primary visual cortex of eight binocularly intact and twelve unilaterally enucleated kittens. It is shown that removal of one eye at birth alters the development of orientation selectivity observed in the presence or absence of visual experience. In 6-week-old deprived kittens, there remain significantly more orientation selective cells in enucleated than in binocularly deprived kittens. These deprivation-resistant cells respond preferentially to horizontal or vertical orientations and are recorded mainly in the cortex contralateral to the remaining eye. In six-week-old kittens with visual experience, the process of tuning maturation appears to be unaffected by unilateral enucleation at birth. However, a larger over-representation of horizontal and vertical orientation preferences is observed in uniocular kittens than in binocularly intact kittens, suggesting that the development of oblique orientation preference depends upon the presence of binocular afferents in the visual pathway.

The postnatal development of visual callosal connections in the absence of visual experience or of the eyes.

Counts of callosal neurons retrogradely labeled by horseradish peroxidase (visualized using multiple substrates) were obtained in areas 17 and 18 of five kittens reared with their eyelids bilaterally sutured and of three kittens which had undergone bilateral enucleation on postnatal days 1--4. These counts were compared with those obtained in normal adult cats. The normal adult distribution of the callosal neurons results from the gradual postnatal reduction of a more widespread juvenile population. Binocular visual deprivation by lid suturing dramatically decreases the final number of callosal neurons and narrows their region of distribution (callosal zone) in areas 17 and 18. A less severe reduction in the final number of callosal neurons is caused by bilateral enucleation, which also increases the width of the callosal zone compared to that of normal cats. Thus, visual experience is necessary for the normal stabilization of juvenile callosal connections. However, since some callosal neurons form connections in the absence of vision, other influences capable of stabilizing juvenile callosal neurons also exist. These influences are probably antagonized by destabilizing influences or inhibited, when the eyes are intact.

The development of ocular dominance columns in normal and visually deprived monkeys.

AbstractThe main purpose of this study was to examine the normal postnatal development of ocular dominance columns in the striate cortex of the macaque monkey and to determine how this developmental process is influenced by monocular lid‐suture. The physiological pattern of ocular dominance was studied in long, tangential electrode penetrations. For anatomical demonstration of the distribution of afferents we relied principally on the transneuronal transport of [3H]proline injected into one eye, and to a lesser extent on the Liesegang silver method. The effects of deprivation on cell size in the lateral geniculate nucleus (LGN) were also studied. Twenty‐six monkeys, divided into 5 groups (A–E), were used. The process of normal columnar development was examined in four monkeys aged from 1 to 6 weeks. At one week, there was both an anatomical and a physiological mixing of left‐ and right‐eye inputs to layer IVC, but the basic columnar pattern was evident, and some small regions were already monccular. At three weeks the columnar pattern resembled that seen in the adult, except for a suggestion that the borders between columns were not so sharply demarcated. By six weeks an adult degree of columnar segregation was established. A series of ten monkeys had monocular suture performed at successively later ages, ranging from 2 days to adult, and they were allowed to survive for a long period. It was found that deprivation begun at any age from birth to about 6 weeks had approximately the same effect: the afferents for the open eye formed greatly expanded columns in layer IVC, and the columns for the closed eye were shrunken and fragmented. In the layers above and below IVC the open eye dominated almost completely. At 10 weeks, closure had only a mild effect on columnar size in layer IVC. With closures at 7–14 months there was no change in the size of columns in layer IVC, but when stained with the Liesegang silver method the deprived‐eye columns were paler than those for the open eye, suggesting a lower density of fibers. These late deprivations still caused a shift of ocular dominance in the upper cortical layers but not such an extreme change as with earlier closures. Lid suture in an adult had no detectable anatomical or physiological effects. Even monocular enucleation, in an adult, failed to induce sprouting of the geniculocortical afferents for the remaining eye. In order to investigate the rate at which monocular deprivation produces its effects, six monkeys were examined after short periods of deprivation in infancy. Eye‐closure from birth to 3 weeks was sufficient to produce the full anatomical and physiological effects. A nine‐day closure at 3 weeks, followed by reopening of the eye, also produced the full effects. A two‐week period of deprivation begun at five weeks of age, however, caused relatively mild columnar expansion in layer IVC, suggesting that late closures may require more time to produce anatomical changes than early closures. The effects of reopening the deprived eye and closing the experienced eye (reverse suture) were studied in three monkeys. The initial lid sutures were performed in the first few days of life. With reverse suture a t 3 weeks the relative sizes of the two sets of columns were reversed. This anatomical reversal was, however, limited to the afferents from the parvocellular laminae of the LGN; the magnocellular afferents remained in the pattern induced by the early deprivation. The layers outside of IVC were strongly dominated by the initially deprived eye. Reverse suture at 6 weeks allowed an anatomical recovery of the parvocellular afferents to a normal columnar size, but not a complete reversal. Again, the magnocellular afferents for the initially deprived eye were not induced t o enlarge their territory. Reverse suture at 1 year of age did not lead to any recovery. One monkey was reared in complete darkness from 3 days of age until 7 weeks of age. This animal, studied autoradiographically, showed a normal columnar pattern in layer IVC. We draw four conclusions from these experiments. (i) Ocular dominance columns are only partially formed a t birth but develop rapidly in the first few weeks of postnatal life. The process of segregation of the left‐ and right‐eye afferents‐in layer IV occurs in the presence or absence of visual experience. (ii) This developmental process may be redirected by early monocular deprivation, causing the segregation of the two sets of afferents into columns of unequal width, (iii) A rearrangement of the afferents can be induced for a short period after their segregation is complete. This is true of both normal and deprived animals. (iv) The eye preference of neurons in the upper and lower layers may be changed even after plasticity in layer‐IVC is no longer detectable.

Development of orientation selectivity in the primary visual cortex of normally and dark reared kittens. II. Models.

The development of orientation selectivity in the primary visual cortex is described by first-order kinetics between three functional compartments chained in a catenary mode. A first model is presented, in which two unidirectional kinetics with constant exchange coefficients, symmetrical in their effects, function in an alternating mode depending on the presence or absence of visual experience. The failure of this model to simulate the modifications induced by a delayed visual experience, when the exchange coefficients are identified to fit normal and dark rearing, supports the hypothesis that the maturation process consequent to interaction with visual environment is dependent on the date at which it is allowed to take place. A second model is then proposed, in which exchange coefficients are piecewise linear functions of time. In order to correctly predict the functional effects of restricted visual experience following prior dark rearing, it is assumed that visuomotor experience during the critical period permits the expression of a non-linear "modifiability gradient" which may have been masked up to this point by the absence of vision or eye movements.

Effect of visual experience on gene expression during the development of stimulus specificity in cat brain

The eyelids of newborn kittens were bilaterally sutured in an experiment to test the effect of patterned visual experience on genetic transcription. A comparison was made of total RNA complexity between brain RNAs from kittens with sutured eyelids and those of their unsutured littermates. The complexity of visual cortex RNA from normally sighted animals was greater than that of lid-sutured animals. In contrast, RNAs from total nonvisual cortices of sutured and unsutured kittens contained indistinguishable RNA sequence complexities, as did RNAs from subcortical structures. Thus, the normal maturation of visual cortex which is dependent on visual experience appears to involve a greater amount of genetic expression than occurs in the absence of visual experience.

On tactual perception of physiognomic properties.

The present study was designed to ascertain whether physiognomic properties, the expressive qualities of percepts, are perceived in the tactual modality even in the absence of visual experience. Flat and solid figures expressing, respectively, Pride, Fear, Sadness, Anger, Peace, Hope, and Forever, as well as flat adaptations of Köhler's Maluma and Takete nonsense figures, were presented for tactual perception, using a matching technique, to 3 groups of children, one of totally and congenitally blind Ss, and two of sighted. The sighted Ss were also tested visually. Positive results were obtained for 4 of the flat ( Pride, Sadness, Anger and Maluma) figures and 3 of the solid ( Pride, Sadness, Anger), supporting the two hypotheses, i.e., (a) that tactual perception of physiognomic properties takes place and (b) that totally and congenitally blind Ss are able to perceive them despite their lack of visual experience. Further support came from a successful replication of these positive findings with another group of totally and congenitally blind Ss. Other findings were that, though there is no demonstrable superiority of either blind or sighted Ss in tactual perception of physiognomic properties, for the sighted, visual perception of such properties is superior to tactual.

RECEPTIVE FIELDS OF CELLS IN STRIATE CORTEX OF VERY YOUNG, VISUALLY INEXPERIENCED KITTENS.

RECEPTIVE FIELDS OF CELLS IN STRIATE CORTEX OF VERY YOUNG, VISUALLY INEXPERIENCED KITTENS.