A familial factor in the development of colour agnosia

An important aspect of research into the link between genes and behaviour concerns the identification of familial determination. There is evidence for familial factors in selective deficits, such as developmental dyslexia and developmental prosopagnosia. Colour agnosia concerns a selective neuropsychological condition in which colour perception is intact, while the identification and naming of colour is disrupted. We recently demonstrated that this deficit can occur as a developmental deficit. Here, we show that there is a familial factor in the development of colour agnosia by reporting the colour processing abilities of the mother and the daughters of a man with developmental colour agnosia.     

Colour constancy and conscious perception of changes of illuminant

A sudden change in illuminant (e.g., the outcome of turning on a tungsten light in a room illuminated with dim, natural daylight) causes a "global" change in perceived colour which subjects often recognise as a change of illuminant. In spite of this distinct, global change in the perceptual appearance of the scene caused by significant changes in the wavelength composition of the light reflected from different objects under the new illuminant, the perceived colour of the objects remains largely unchanged and this cornerstone property of human vision is often described as instantaneous colour constancy (ICC). ICC mechanisms are often difficult to study. The generation of appropriate stimuli to isolate ICC mechanisms remains a difficult task since the extraction of colour signals is also confounded in the processing of spatial chromatic context that leads to ICC. The extraction of differences in chromaticity that describe spatial changes in the wavelength composition of the light on the retina is a necessary operation that must precede colour constancy computations. A change of illuminant or changes in the spectral reflectance of the elements that make up the scene under a constant illuminant cause spatial changes in chromatic context and are likely to drive colour constancy mechanisms, but not exclusively. The same stimulus changes also cause differences in local luminance contrast and overall light flux changes, stimulus attributes that can activate different areas of the visual cortex. In order to address this problem we carried out a series of dichoptic experiments designed to investigate how the colour signals from the two eyes are combined in dichoptically viewed Mondrians and the extent to which the processing of chromatic context in monocularly driven neurons contributes to ICC. The psychophysical findings show that normal levels of ICC can be achieved in dichoptic experiments, even when the subject remains unaware of any changes of illuminant. Functional MRI (fMRI) experiments using new stimuli that produce stimulation of colour constancy mechanisms only in one condition with little or no difference in the activity generated in colour processing mechanisms in both test and reference conditions were also carried out. The results show that the processing of ICC signals generates strong activation in V1 and the fusiform colour area (V4, V4A). Significant activation was also observed in areas V2 and V3.     

Chromatic edges, surfaces and constancies in cerebral achromatopsia

We tested achromatopsic observer, MS, on a number of tasks to establish the extent to which he can process chromatic contour. Stimuli, specified in terms of cone-contrast, were presented in a three-choice oddity paradigm. First we show that MS is able to discriminate the magnitude of chromatic and luminance contrast, but performance is inferior to that of normal observers. Moreover, MS can discriminate isoluminant borders of different chromatic composition. These abilities are not the result of unintended luminance differences and are abolished when chromatic borders are masked by sharp luminance change. In simple displays, local cone-contrast signals can make a significant contribution to surface colour appearance in normal observers. In more complex displays, the perception of a surface's colour becomes largely independent of the local contrast to its background, via processes presumed to be similar to the edge integration and anchoring stages of Land's Retinex algorithm. We show that in simple displays the percepts of both MS and normal observers are dominated by local chromatic-contrast. But, although the percepts of normal observers change in line with the predictions of retinex theory in more complex displays, those of MS do not, remaining dominated by local contrast signals. We conclude that MS has lost the ability to perform edge integration and that this loss is closely related to his absence of colour experience.     

Colour discrimination and categorisation in Williams syndrome

Individuals with Williams syndrome (WS) present with impaired functioning of the dorsal visual stream relative to the ventral visual stream. As such, little attention has been given to ventral stream functions in WS. We investigated colour processing, a predominantly ventral stream function, for the first time in nineteen individuals with Williams syndrome. Colour discrimination was assessed using the Farnsworth-Munsell 100 hue test. Colour categorisation was assessed using a match-to-sample test and a colour naming task. A visual search task was also included as a measure of sensitivity to the size of perceptual colour difference. Results showed that individuals with WS have reduced colour discrimination relative to typically developing participants matched for chronological age; performance was commensurate with a typically developing group matched for non-verbal ability. In contrast, categorisation was typical in WS, although there was some evidence that sensitivity to the size of perceptual colour differences was reduced in this group.     

A new way to use the Ishihara test

Summary The Ishihara plates are widely used as a test for colour vision. Originally designed for the purpose of detecting congenital red-green colour blindness, the test also has some value in demonstrating acquired colour vision defects. There are, however, several disadvantages in the present arrangement of the plates. A modification of the test, involving the rearrangement of the order of the plates, is presented which, together with a new recording chart, simplifies both the administration and the interpretation of the test.     

Attentional capture by colour and motion in cerebral achromatopsia

Cerebral achromatopsia is a rare condition in which damage to the ventromedial occipital area of the cortex results in the loss of colour experience. Nevertheless, cortically colour-blind patients can still use wavelength variation to perceive form and motion. In a series of six experiments we examined whether colour could also direct exogenous attention in an achromatopsic observer. We employed the colour singleton paradigm, the phi motion effect, and the correspondence process to assess attentional modulation. Although colour singletons failed to capture attention, a motion signal, based solely on chromatic information, was able to direct attention in the patient. We then show that the effect is abolished when the chromatic contours of stimuli are masked with simultaneous luminance contrast. We argue that the motion effect is dependent on chromatic contrast mediated via intact colour-opponent mechanisms. The results are taken as further evidence for the processing of wavelength variation in achromatopsia despite the absence of colour experience.     

颈动脉粥样硬化与脑梗死关系的临床研究

目的研究颈动脉粥样硬化与脑梗死的关系。方法对116例经CT、MRI证实的脑梗死患者的颈动脉颅外段进行彩色超声多普勒检查，观察颈动脉壁的病变性质和颈动脉管腔的狭窄率，并与对照组进行比较。结果116例脑梗死患者中有85例（73．28％）颈动脉颅外段存在不同程度的粥样硬化斑，与对照组比较差异有显著性（P〈0.01）；粥样硬化斑块好发于颈总动脉分叉处（BIF），其次为颈总动脉（CCA）；梗死灶同侧颈动脉粥样硬化较对侧严重。结论颈动脉粥样硬化是脑梗死的重要危险因素，防止颈动脉粥样硬化斑块形成对预防脑梗死的发生有非常重要的意义。     

Effects of incidental and intentional feature binding on recognition: a behavioural and PET activation study.

Using Positron Emission Tomography (PET), we investigated cerebral regions associated with the episodic recognition of words alone and words bound to contextual colours. Two modes of colour encoding were tested: incidental and intentional word-to-colour binding. Word-only recognition was associated with brain activation in a lexico-semantic left middle temporal region and in the cerebellum following an incidental colour encoding, and with brain activation in the left posterior middle frontal gyrus, right anterior cingulate and right inferior frontal gyrus following an intentional encoding. Recognition of bound features was associated with activation in left prefrontal and superior parietal regions following an incidental colour encoding, and with preferential right prefrontal cortex activation following an intentional colour encoding. Our results are in line with the hypothesis of a parietal involvement in context processing, and prefrontal areas in monitoring retrieval processes. Our results also support the hypothesis of a 'cortical asymmetry for reflective activity' (CARA).     

Aposematic colouration enhances memory formation in domestic chicks trained in a weak passive avoidance learning paradigm

The one-trial passive avoidance learning task is commonly used in avian research to explore anatomical, cellular and molecular parameters of learning and memory. Many factors are known to influence the effectiveness and/or duration of such learning events. Combinations of novel odours, such as pyrazine, and aposematic colours, such as brig ht yellow or red, have been shown to induce a long-lasting aversion to food crumbs in ‘visual’ predators, including birds such as the domestic chick (1). The aim of this study was to (a) examine whether visual complexity played a role in the generation of an aversive response to a novel visual stimulus and (b) to establish whether the duration of memory of an aversive experience could be modified by altering the visual properties of the stimulus. In the first experiment, naïve domestic chicks were trained on a weakly aversive one-trial passive avoidance bead task, in which chicks were allowed to peck at a bead coated with a 10% solution of the bitter-tasting and odorous substance methylanthranilate (MeA). The chicks were trained with (allowed to peck) one of four differently coloured beads dipped in 10% MeA. Chrome, black, yellow or black-and-yellow striped beads were used. ‘Recall’ of the aversive bead was examined by presenting the (clean) training bead 24 h after training and monitoring avoidance to it compared to a ‘neutral’ white bead. A high proportion (63%) of chicks trained with the black and yellow striped bead avoided it 24 h after training, whereas little or no avoidance was seen in response to chrome, yellow or black beads. In a second experiment naïve domestic chicks were all trained once only with a black and yellow striped bead coated in a 10% MeA solution, but this time, were tested 24 h later, once only, with either a black, a yellow or a black and yellow striped bead. Nearly 60% of chicks tested with a black and yellow striped bead showed avoidance of the bead, whereas only 23% of those tested with a black bead and 14% tested with a yellow bead showed avoidance. These results confirm the importance of complex warning colouration, when paired with a novel olfactory cue and a bitter taste, in avoidance learning. We conclude that the chicks’ response to monochromatic colours (e.g. yellow or black) is not affected by their previous experience with a conspicuously patterned stimulus (yellow and black stripes). Moreover, it suggests a predisposition for chicks to attend to aversive cues associated with ‘naturalistic’ high contrast colour cue combinations such as black and yellow.     

Colour Doppler imaging as an aid to excision of an arteriovenous malformation

Colour Doppler ultrasound was used to localise an arteriovenous malformation (AVM) and its major feeding vessel intraoperatively. The successful ligation and division of this vessel could be confirmed with confidence on colour Doppler ultrasound. The malformation immediately became less turgid and was completely excised. Colour Doppler ultrasound was a valuable adjunct in the localisation and excision of this AVM and has application to AVM surgery in general.     

Does colour say something about emotions?: Laypersons’ assessments of colour drawings

This study examines the use of colours in estimating psychological states. Sixteen artworks were produced by two different populations: clients with a psychological condition and psychologically healthy people. Their drawings were presented in pairs on screen either chromatically or achromatically. Two hundred and twenty-four subjects were asked to choose a picture which they thought had been produced by a psychologically unhealthy client. The rate of correct answers was higher for the chromatic condition. When artworks were presented achromatically, errors increased. Analysis of colour factors and post-inquiry indicated that the number of colours used, list of colours, and colour connotation might have affected choices. This study confirms that colour can be effective in estimating psychological states. Its implications and limitations are discussed and suggestions made for future study.     

Difference in blood flow volume of the common carotid artery between vascular and non-vascular dementia detected by colour duplex sonography

Using colour duplex sonography, blood flow volume in the common carotid artery was measured in 72 demented patients and 28 normal controls. Thirty-five patients with a Hachmski's ischaemic score of 7 or above and marked ischaemic lesions on CT were assigned to the vascular dementia (VD) group. Thirty three patients with probable Alzheimer's disease according to the NINCDS-ADRDA criteria, 2 patients with Parkinson's disease, 1 patient with spinocerebellar degeneration, and 1 patient with Pick's disease were assigned to the non-vascular dementia (nonVD) group. The sum of blood flow volume in the bilateral common carotid arteries (CCA flow) in the nonVD group and in the VD group was lower than that in the control group. The CCA flow in the VD group was lower than that in the nonVD group. Comparison of patients matched for both age and the Hasegawa's dementia rating scale also revealed lower CCA flow in the VD group than in the nonVD group. Linear discriminant function analysis showed that nearly 90% of the demented patients were correctly diagnosed as having VD or as having nonVD. These results show the usefulness of colour duplex sonography in the differential diagnosis of patients with dementia.     

Covert colour processing in colour agnosia

Patients with colour agnosia can perceive colours and are able to match coloured patches on hue, but are unable to identify or categorise colours. It is a rare condition and there is as yet no agreement on the clinical definition or a generally accepted explanation. In line with observations from object agnosia and prosopagnosia, we hypothesised that (some of) these patients might still be able to process colour information at an implicit level. In this study, we investigated this possibility of implicit access to colour semantics and colour names in a man (MAH) who suffers from developmental colour agnosia. We designed two experimental computer tasks: an associative colour priming task with a lexical decision response and a reversed Stroop task. The results of these experiments suggest that there is indeed automatic processing of colour, although MAH was unable to explicitly use colour information.     

The neural correlate of colour distances revealed with competing synaesthetic and real colours

Synaesthetes claim to perceive illusory colours when reading alphanumeric symbols so that two colours are said to be bound to the same letter or digit (i.e., the colour of the ink, e.g., black, and an additional, synaesthetic, colour). To explore the neural correlates of this phenomenon, we used a Stroop single-letter colour-naming task and found that distances in colour space between the illusory and real colours of a letter target (as computed from either the RGB or CIExyY coordinates of colours) systematically influenced the degree of neuronal activation in colour-processing brain regions. The synaesthetes also activated the same fronto-parietal network during the classic colour-word Stroop task and single-letter tasks. We conclude that the same neural substrate that supports the conscious experience of colour, as triggered by physical wavelength, supports the experience of synaesthetic colours. Thus, two colour attributes (one that is wavelength-dependent and one that is illusory) can be bound to the same stimulus position and simultaneously engage the colour areas in proportion to their similarity in colour space.     

Real color captures attention and overrides spatial cues in grapheme-color synesthetes but not in controls

Grapheme-color synesthetes perceive color when reading letters or digits. We investigated oscillatory brain signals of synesthetes vs. controls using magnetoencephalography. Brain oscillations specifically in the alpha band (∼10 Hz) have two interesting features: alpha has been linked to inhibitory processes and can act as a marker for attention. The possible role of reduced inhibition as an underlying cause of synesthesia, as well as the precise role of attention in synesthesia is widely discussed.     

iPad colour vision apps for dyschromatopsia screening

Optic neuritis (ON) is a common and important cause of vision loss or vision disturbances in the community, particularly amongst the young, and it is often associated with a persistent dyschromatopsia. Traditionally screening for dyschromatopsia has been carried out using pseudo-isochromatic Ishihara plates. These colour plates were originally developed for testing of colour blindness, and indeed have only more recently been applied to ON. As the Ishihara plate books used for testing are expensive, unwieldy, and are not commonly available in many clinics or wards, many neurologists and ophthalmologists have taken to using untested and unstudied downloadable software packages on portable electronic devices for testing. This study compared the efficacy of printed and iPad (Apple, Cupertino, CA, USA) versions of the Ishihara plates in screening for dyschromatopsia in patients who were suspected of having ON. The main finding was that dyschromatopsia testing using a commercially available application on an iPad was comparable to using the current pragmatic clinical benchmark, the pseudo-isochromatic plates of Ishihara. These findings provide support for the increasingly common practice of screening for dyschromatopsia using the iPad.     

Colour discrimination among patients with schizophrenia in Lebanon

Abstract

Background: Abnormalities and contrast sensitivity have already been studied in schizophrenia. However, the relationship between symptom severity in schizophrenia and colour vision sensitivity has not been studied systematically.

Aim: Our objective was to evaluate colour discrimination in patients with schizophrenia compared to controls and examine if this colour discrimination is correlated with schizophrenia symptoms’ severity.

Methods: This case–control study, performed between January and April 2017, included 50 schizophrenic patients and 50 healthy controls matched for age and sex. The Positive and Negative Symptoms Scale (PANSS) was used to determine the schizophrenia symptoms’ severity. Colour discrimination was evaluated using the total error score (TES) generated using the Farnsworth D-15 test. The higher the TES, the more severe colourblindness.

Results: A significantly higher mean TES was found in schizophrenics (30.32) compared to healthy patients (13.07) (p?<?0.001). Colour blindness was correlated to the severity of schizophrenic symptoms only in the subgroup of patients with severe schizophrenia.

Conclusion: Colour vision defect is a common feature in schizophrenia, and may be more significant when related to psychotic symptoms.

• KEY POINTS

• A significantly higher mean TES was found in schizophrenics compared to healthy patients.

• Colour blindness was correlated to the severity of schizophrenic symptoms only in the subgroup of patients with severe schizophrenia.

• Colour vision defect is a common feature in schizophrenia, and may be more significant when related to psychotic symptoms.

     

脑桥静脉对颅内压增高的调节反应

目的 研究正常和过度换气时脑桥静脉对颅内压增高的血流动力学改变。方法 选择７头丹麦白约克猪通过向枕大池灌注人工脑脊液,逐步增加颅内压,从基础值（大约１．３ｋＰａ）到２．７ｋＰａ和４．０ｋＰａ,用彩色超声多谱勒测量正常和过度换气状态下,颅内压增高对于脑桥静脉的血流速度、直径和脉冲指数的影响。结果 随着颅内压增高,脑桥静脉的血流速度减慢,直径和脉冲指数增加,而颅内压增高对中心静脉压、动脉ＣＯ２分压、平     

Context-dependent prey avoidance in chicks persists following complete telencephalectomy

Young naïve domestic chicks readily attack green insects and avoid insects painted red but show no discrimination of the same colours when applied to fruit-like objects, a discrimination that has been depicted as context-dependent preference. To study the neural representation of such preference we performed bilateral telencephalectomy on 1-day-old domestic chicks and tested them on an unlearned prey discrimination paradigm. Here we show that following complete decerebration, young domestic chicks preferentially peck at red fruit versus red insects and tend to choose green insects over green fruit indistinguishably from unoperated chicks. The present study provides the first direct evidence that sophisticated context-dependent, unlearned colour preference is processed by subtelencephalic areas of an amniote species.     

Blindsight following visual cortex deafferentation disappears with purple and red stimuli: A case study

We employed a redundant signal effect (RSE) paradigm to ascertain the role of the superior colliculus (SC) in blindsight. The RSE consists of the speeding of reaction time (RT) to double versus single stimuli. One patient with a unilateral lesion of the optic radiation and consequent hemianopia showed a RSE with pairs of visual stimuli presented across the vertical meridian despite seeing only stimuli in the intact hemifield. However, when, instead of achromatic stimuli we used short or long wavelength stimuli the implicit RSE disappeared. This result raises the possibility that implicit chromatic processing in the affected hemifield might have a different neural substrate following deafferentation with respect to lesion of the primary visual cortex.