Deficits In Visual Discrimination Research Articles

Visual discrimination and inhibitory control deficits in mouse models of Down syndrome: A pilot study using rodent touchscreen technology.

Several non-verbal cognitive and behavioral tests have been developed to assess learning deficits in humans with Down syndrome (DS). Here we used rodent touchscreen paradigms in adult male mice to investigate visual discrimination (VD) learning and inhibitory control in the Dp(16)1/Yey (C57BL/6J genetic background), Ts65Dn (mixed B6 X C3H genetic background) and Ts1Cje (C57BL/6J genetic background) mouse models of DS. Dp(16)1/Yey and Ts1Cje models did not exhibit motivation or learning deficits during early pre-training, however, Ts1Cje mice showed a significant learning delay after the introduction of the incorrect stimulus (late pre-training), suggesting prefrontal cortex defects in this model. Dp(16)1/Yey and Ts1Cje mice display learning deficits in VD but these deficits were more pronounced in the Dp(16)1/Yey model. Both models also exhibited compulsive behavior and abnormal cortical inhibitory control during Extinction compared to WT littermates. Finally, Ts65Dn mice outperformed WT littermates in pre-training stages by initiating a significantly higher number of trials due to their hyperactive behavior. Both Ts65Dn and WT littermates showed poor performance during late pre-training and were not tested in VD. These studies demonstrate significant learning deficits and compulsive behavior in the Ts1Cje and Dp(16)1/Yey mouse models of DS. They also demonstrate that the mouse genetic background (C57BL/6J vs. mixed B6 X C3H) and the absence of hyperactive behavior are key determinants of successful learning in touchscreen behavioral testing. These data will be used to select the mouse model that best mimics cognitive deficits in humans with DS and evaluate the effects of future therapeutic interventions.

Neural responses in a fast periodic visual stimulation paradigm reveal domain-general visual discrimination deficits in developmental prosopagnosia

We investigated selective impairments of visual identity discrimination in developmental prosopagnosia (DP), using a fast periodic identity oddball stimulation paradigm with electroencephalography (EEG). In Experiment 1, neural responses to unfamiliar face identity changes were strongly attenuated for individuals with DP as compared to Control participants, to the same extent for upright and inverted faces. This reduction of face identity discrimination responses, which was confirmed in Experiment 2, provides direct evidence for deficits in the visual processing of unfamiliar facial identity in DP. Importantly, Experiment 2 demonstrated that DPs showed attenuated neural responses to identity oddballs not only with face images, but also with non-face images (cars). This result strongly suggests that rapid identity-related visual processing impairments in DP are not restricted to faces, but also affect familiar classes of non-face stimuli. Visual discrimination deficits in DP do not appear to be face-specific. To account for these findings, we propose a new account of DP as a domain-general deficit in rapid visual discrimination.

Cognitive Impairments in Touchscreen-based Visual Discrimination and Reversal Learning in Genetic Absence Epilepsy Rats from Strasbourg

Absence Epilepsy (AE) is associated with recurrent losses of awareness and synchronous bilateral spike-wave discharges (SWDs). While seizures do not generally continue into adulthood, cognitive and behavioral comorbidities persist. One preclinical model used to investigate AE is the Genetic Absence Epilepsy Rats from Strasbourg (GAERS) which consistently have bilateral SWDs and similar behavioral profiles. In this experiment, we characterized discrimination learning and behavioral flexibility in female and male GAERS (n = 7 per sex) and Non-Epileptic Controls (NEC; n = 8 per sex) in a touchscreen-based version of visual discrimination (VD) and reversal learning (RL). We found that, on average, female GAERS required more sessions (12.3) to complete pretraining compared to female and male NEC (8.2 and 7.3, respectively) and male GAERS (9.4). In contrast, there was a sex-specific impairment during VD with male GAERS requiring more sessions on average (12.3) than male and female NEC (both 7.5) and female GAERS (8.3). Additionally, male GAERS completed >30% more selection and correction trials during VD and made >30% more errors.Both female and male GAERS required more sessions on average (9.1 and 10.7, respectively) of RL compared to female and male NEC (6.4 and 6.0 sessions, respectively). Accordingly, GAERS performed ∼30% more selection trials and correction trials compared to NEC, although only male GAERS made significantly more errors (>40%). Deficits in VD and RL were not associated with differences in correct or incorrect response latency, or reward collection latency, suggesting impairments are not due to alterations in locomotor activity or motivation. Together, these data suggest that GAERS have impaired behavioral flexibility and identify some sex-dependent differences. Thus, GAERS may be suitable for assessing the potential benefit of antiepileptic drugs on comorbid behavioral and cognitive deficits.

Visual processing in reading disorders and attention-deficit/hyperactivity disorder and its contribution to basic reading ability.

Whether visual processing deficits are common in reading disorders (RD), and related to reading ability in general, has been debated for decades. The type of visual processing affected also is debated, although visual discrimination and short-term memory (STM) may be more commonly related to reading ability. Reading disorders are frequently comorbid with ADHD, and children with ADHD often have subclinical reading problems. Hence, children with ADHD were used as a comparison group in this study. ADHD and RD may be dissociated in terms of visual processing. Whereas RD may be associated with deficits in visual discrimination and STM for order, ADHD is associated with deficits in visual-spatial processing. Thus, we hypothesized that children with RD would perform worse than controls and children with ADHD only on a measure of visual discrimination and a measure of visual STM that requires memory for order. We expected all groups would perform comparably on the measure of visual STM that does not require sequential processing. We found children with RD or ADHD were commensurate to controls on measures of visual discrimination and visual STM that do not require sequential processing. In contrast, both RD groups (RD, RD/ADHD) performed worse than controls on the measure of visual STM that requires memory for order, and children with comorbid RD/ADHD performed worse than those with ADHD. In addition, of the three visual measures, only sequential visual STM predicted reading ability. Hence, our findings suggest there is a deficit in visual sequential STM that is specific to RD and is related to basic reading ability. The source of this deficit is worthy of further research, but it may include both reduced memory for order and poorer verbal mediation.

Clarifying the role of pattern separation in schizophrenia: The role of recognition and visual discrimination deficits

Patients with schizophrenia show marked memory deficits which have a negative impact on their functioning and life quality. Recent models suggest that such deficits might be attributable to defective pattern separation (PS), a hippocampal-based computation involved in the differentiation of overlapping stimuli and their mnemonic representations. One previous study on the topic concluded in favour of pattern separation impairments in the illness. However, this study did not clarify whether more elementary recognition and/or visual discrimination deficits could explain observed group differences. To address this limitation we investigated pattern separation in 22 schizophrenic patients and 24 healthy controls with the use of a task requiring individuals to classify stimuli as repetitions, novel or similar compared to a previous familiarisation phase. In addition, we employed a visual discrimination task involving perceptual similarity judgments on the same images. Results revealed impaired performance in the patient group; both on baseline measure of pattern separation as well as an index of pattern separation rigidity. However, further analyses demonstrated that such differences could be fully explained by recognition and visual discrimination deficits. Our findings suggest that pattern separation in schizophrenia is predicated on earlier recognition and visual discrimination problems. Furthermore, we demonstrate that future studies on pattern separation should include appropriate measures of recognition and visual discrimination performance for the correct interpretation of their findings.

Can complex visual discrimination deficits in amnesia be attributed to the medial temporal lobe? An investigation into the effects of medial temporal lobe damage on brain connectivity

It has been suggested that complex visual discrimination deficits in patients with medial temporal lobe (MTL) damage may be explained by damage or dysfunction beyond the MTL. We examined the resting functional networks and white matter connectivity of two amnesic patients who have consistently demonstrated discrimination impairments for complex object and/or spatial stimuli across a number of studies. Although exploratory analyses revealed some significant differences in comparison with neurologically healthy controls (more specifically in the patient with a larger MTL lesion), there were no obvious findings involving posterior occipital or posterior temporal regions, which can account entirely for their discrimination deficits. These findings converge with previous work to support the suggestion that the MTL does not subserve long-term declarative memory exclusively. © 2012 Wiley Periodicals, Inc.

An approach to evaluate the ability of rats to discriminate different levels of illumination in the plus maze test: Effects of scopolamine

Previous research has shown that the visual system is important for rats to establish the arm preference in the elevated plus maze (EPM), an animal model of anxiety. This study aims at evaluating whether a gradient of illumination between the enclosed arms of the maze (E/E ΔLux) could be a reliable approach to detect drugs-induced harmful effect on visual discrimination of rats. Four EPM configurations with different E/E ΔLux (8, 41 and 85 lx) were used to demonstrate that as E/E ΔLux increases, rats avoid to explore the light enclosed arm, which characterizes the animal ability to discriminate the most illuminated area within the protected environment of the maze. The establishment of either 41 or 85 E/E ΔLux failed to alter the traditional spatial–temporal variables in the EPM. In addition, systemic treatment with midazolam (MDZ; 1.0 mg kg −1, a classical anxiolytic) induced anxiolysis in rats tested in 41 and 85 E/E ΔLux EPM, with no change in the visual discrimination, when evaluated by the level of light enclosed arm exploration. Systemic treatment with scopolamine (SCP; 1.0, 2.0 and 8.0 mg kg −1), a drug endowed with harmful properties upon the visual system, did not change either the open arm avoidance or the visual discrimination at the low doses, but induced increased light enclosed arm (visual discrimination deficit) and open arm exploration (anxiolytic like effect) at a higher dose. We propose that the incorporation of an E/E ΔLux in the EPM may reinforce the predict validity of the test since it enables to evaluate whether a visual discrimination deficit can be confounded with an anxiolytic-like effect, thus establishing a false positive detection.

Effects of Wulst and ectostriatum lesions on repeated acquisition of spatial discrimination in pigeons

The avian telencephalon has two visual areas, (1) a ‘Wulst’ that consists of hyperstriatum accessorium, hyperstriatum intercalatus superior and hyperstriatum dorsale, and (2) the ectostriatum. Deficits in visual discrimination have been observed after ectostratal lesions but not after Wulst lesions. In the present experiments, the cognitive functions of the Wulst in pigeons were examined. Pigeons were trained on repeated acquisition of a three key discrimination. Every time the subjects reached the criterion of discrimination, they were trained on different discriminations in which one of two previously incorrect keys became the correct key. The Wulst lesions disrupted the acquisition of discrimination, while the ectostriatal lesions did not.

The role of neural mechanisms of attention in solving the binding problem.

We thank L. Chelazzi, V. Ferrera, P. Fries, S. Kastner, and A. Rossi for helpful comments on the manuscript.

Glutamate affects the development of the thalamofugal visual projection of the chick

Examination of the thalamofugal visual projections of the chick following treatment of the hyperstriatal regions with glutamate was undertaken to investigate whether structural change underlies slowed learning known to follow such treatment. On the second day after hatching from eggs exposed to light, chicks were injected bilaterally with 5 μl of 100 mM glutamate or physiological saline. On post-hatching day 8, retrograde fluorescence labelling of the thalamofugal projections with True Blue and FluoroGold led to the labelling of thalamic cells which project to the visual hyperstriatum. The number of contralateral and ipsilateral projections relative to each dye injection site was determined. Glutamate prevented the development of the structural asymmetry which is present in control chicks. The resultant symmetry of the thalamofugal projections in glutamate-treated chicks may cause deficits in visual discrimination.

Eye-closure procedure and the visual deficit after unilateral ablation of the occipital lobe in the rabbit.

In the rabbit, unilateral ablation of the occipital lobe leads to a severe impairment of striated pattern discrimination with the eye contralateral to the lesion. In the present report it is studied whether the acute reduction of the overall visual field, due to closure of the eye contralateral to the intact hemisphere shortly before each testing session, leads to results which underestimate the animal's capability to discriminate striated patterns via the ipsilateral fibres. The experiment described in the present report suggests that this is not the case and that there is a genuine visual discrimination deficit after unilateral ablation of the visual cortex.

Gender differences in visual discrimination by rats in response to malnutrition of varying durations

Visual discrimination of hooded rats was tested at 3 months of age by a Lashley procedure. Three groups of rats were used: those with histories of protein deprivation for up to 20 generations, those with protein deprivation for a single generation, and well-nourished controls. Growth retardation was present to a similar degree in both genders of the 2 malnourished groups. Deficits in visual discrimination were observed in female animals with intergenerational malnutrition, but not in females with single-generation malnutrition. Males with intergenerational and single-generation malnutrition showed equal deficits in visual discrimination. These findings demonstrate that the performance of female rats is impaired only after prolonged exposure to malnutrition, whereas males are vulnerable after shorter periods.

Visual discrimination deficits of reading-disabled children: sex artifact?

Several theorists have suggested that deficits in visual discrimination play an etiological role in the development of reading deficits in children who are diagnosed as learning-disabled. Supporting this theory, a number of studies have shown that disabled readers make more errors on visual discrimination tasks than do good readers. The present study, however, suggests that those findings may have been due to a sex-difference artifact. Thirty-six 8- and 9-year-old good readers and reading-disabled children of both sexes responded to 40 matching items under untimed conditions. Males made more errors than females, but overall, reading-disabled children made no more errors than good readers. These findings, along with a reanalysis of previous studies, suggest that because reading disabilities are more common in males, evidence construed as supporting a visual discrimination hypothesis may have been an artifact of a sex difference in studies in which sex was not controlled.

Varying Deficits in Visual Discrimination Performance Associated with Different Forms of Malnutrition in Rats

Visual discrimination at 3 months of age was examined by the Lashley jumping stand test to rats malnourished by one of the following techniques: intergenerational malnutrition over 14 to 18 generations; protein deficiency from birth on; rearing in large litters, and rotation among lactating and non-lactating females. All four treatments caused stunting during the litter period, but only the first two were associated with reduced weights at the time of testing. Deficits in visual discrimination were most severe in males and females with intergenerational malnutrition. Both large-litter rearing and protein deficiency for one generation impaired visual discrimination in males only, whereas rotation between lactating and non-lactating females did not reduce visual discrimination in either gender. It is possible that extranutritional factors associated with each type of malnutrition may serve either to enhance or diminish the impact of malnutrition on the nervous system.

Visual discrimination following partial telencephalic ablations in nurse sharks (Ginglymostoma cirratum).

An instrumental conditioning task was used to examine the role of the nurse shark telencephalon in black-white (BW) and horizontal-vertical stripes (HV) discrimination performance. In the first experiment, subjects initially received either bilateral anterior telencephalic control lesions or bilateral posterior telencephalic lesions aimed at destroying the central telencephalic nuclei (CN), which are known to receive direct input from the thalamic visual area. Postoperatively, the sharks were trained first on BW and then on HV. Those with anterior lesions learned both tasks as rapidly as unoperated subjects. Those with posterior lesions exhibited visual discrimination deficits related to the amount of damage to the CN and its connecting pathways. Severe damage resulted in an inability to learn either task but caused no impairments in motivation or general learning ability. In the second experiment, the sharks were first trained on BW and HV and then operated. Suction ablations were used to remove various portions of the CN. Sharks with 10% or less damage to the CN retained the preoperatively acquired discriminations almost perfectly. Those with 11-50% damage had to be retrained on both tasks. Almost total removal of the CN produced behavioral indications of blindness along with an inability to perform above the chance level on BW despite excellent retention of both discriminations over a 28-day period before surgery. It appears, however, that such sharks can still detect light. These results implicate the central telencephalic nuclei in the control of visually guided behavior in sharks.

Visual activation of neurons in inferotemporal cortex depends on striate cortex and forebrain commissures.

Neurons in inferotemporal cortex respond only to visual stimuli and a majority have receptive fields that extend well into both visual half-fields. After bilateral removal of striate cortex, no inferotemporal neurons responded to visual stimuli. After unilateral removal of striate cortex, inferotemporal neurons in both hemispheres responded only to stimuli in the hemifield contralateral to the intact striate cortex. After section of the corpus callosum and anterior commissure, inferotemporal neurons in both hemispheres responded only to stimuli in the hemifield contralateral to the recording site. These results indicate that inferotemporal cortex visual information from striate cortex and that the pathway from striate cortex to the contralateral inferotemporal cortex includes the forebrain commissures. This same striate-temporal pathway is also necessary for normal discrimination learning. We suggest that the converging input onto single inferotemporal neurons from widely separated retinal areas may provide a mechanism for stimulus equivalence over different parts of the visual field, and it may be the absence of such a mechanism that contributes to the visual discrimination deficit that follows inferotemporal lesions.

Discriminative aspects of visual hemi-inattention.

Deficits in visual discrimination were examined in 30 combat soldiers with head wounds, 20 of whom had unilateral lesions (10 right and 10 left) of the posterior cerebral hemispheres and 10 of whom had frontal lobe wounds, left, right or bilateral. Seven of the patients with posterior lesions, but none with frontal lesions, showed visual spatial disorientation as demonstrated by a shift in the peak of the stimulus generalization gradient of an experimentally conditioned sensory discrimination. The peak shift occurred to the side opposite the cerebral lesion in all cases, and the deficit did not occur when the task was presented as a match to sample.

The Klüver-Bucy syndrome produced by partial isolation of the temporal lobe

Longitudinally running fibers were transected in the posterior part of the temporal lobe in three monkeys; in three others, the white matter connecting the temporal lobe medially was cut. These animals and three controls were examined for many of the symptoms associated with complete bilateral temporal lobe removal. The experimental animals in both groups displayed severe and lasting visual discrimination deficits. Orality, hypoemotionality, and perseverative behavior were also observed.

Visual discrimination deficits associated with posterior inferotemporal lesions in the monkey

Monkeys with bilateral inferotemporal lesions extending from the midtemporal region to the inferior occipital sulcus show a severe visual discrimination deficit which is not associated with a general visual learning impairment. The deficit is seen most severely when two-dimensional patterns are discriminated. Reducing the physical size of patterns and masking them with irrelevant stimuli intensifies the severity of the deficit. However, under certain discrimination paradigms, an impairment is seen when small differences in uni-dimensional stimuli, such as intensity of light, are to be perceived. The nature of this perceptual defect, its distinction from the defects associated with striate cortex lesions and the anatomical status of the critical lesion are discussed.

Tectal and cortical function in vision

Lesions in the visual cortex and tectum of tree shrews resulted in deficits in visual discrimination which were peculiar to the type of lesion made. Animals with cortical lesions appeared normal in their response to moving objects, in the detection of visual cliffs, and in the equivalence of simple stimuli but were impaired on more complicated equivalence tests. This deficit was interpreted as a defect in the intramodality attention. Tectal lesions resulted in inattention to objects (i.e., intermodality attention) while bilateral complete ablations impaired pattern vision. Thus, one type of visual attention and possibly identification are tectal functions, while the cortex operates upon the received information to inhibit incorrect responses which are available or attend to correct ones. An analogy to similar functions in the auditory system was made.