Perception or preference? Mediation of gene effects in the colour choices of naive quail chicks (C. coturnix japonica)

The purpose of this study was to examine gene effects in the peripheral and central neural mediation of colour preferences in artificially selected Japanese quail chicks (Coturnix coturnix japonica). Behavioural data indicated preferences of blue over red and red over blue in the respectively selected genetic lines, and general preferences for white in both lines. Preferences were influenced by luminance variations of testing stimuli. Choices between segmented stimuli that combined blue, red, and white, in various patterns of systematically varied hues and luminances, indicated perceptual discrimination of colours in each line. Preference values combined within stimuli summated additively in choice responses, suggesting no genetic association between colour preference and colour perception. Electrophysiological data indicated systematic differences between waveshapes of averaged evoked potentials according to hues of eliciting stimuli. These data also counterindicated the involvement of colour perception in the genetic variations of colour preference. However, no significant differences between waveshapes were found in relation to genetic variations in preferences.     

Effect of colour of drugs: systematic review of perceived effect of drugs and of their effectiveness.

OBJECTIVE: To assess the impact of the colour of a drug''s formulation on its perceived effect and its effectiveness and to examine whether antidepressant drugs available in the Netherlands are different in colour from hypnotic, sedative, and anxiolytic drugs. DESIGN: Systematic review of 12 published studies. Six studies examined the perceived action of different coloured drugs and six the influence of the colour of a drug on its effectiveness. The colours of samples of 49 drugs affecting the central nervous system were assessed using a colour atlas. MAIN OUTCOME MEASURES: Perceived stimulant action versus perceived depressant action of colour of drugs; the trials that assessed the effect of drugs in different colours were done in patients with different diseases and had different outcome measures. RESULTS: The studies on perceived action of coloured drugs showed that red, yellow, and orange are associated with a stimulant effect, while blue and green are related to a tranquillising effect. The trials that assessed the impact of the colour of drugs on their effectiveness showed inconsistent differences between colours. The quality of the methods of these trials was variable. Hypnotic, sedative, and anxiolytic drugs were more likely than antidepressants to be green, blue, or purple. CONCLUSIONS: Colours affect the perceived action of a drug and seem to influence the effectiveness of a drug. Moreover, a relation exists between the colouring of drugs that affect the central nervous system and the indications for which they are used. Research contributing to a better understanding of the effect of the colour of drugs is warranted.     

Colour and brightness coding in the central nervous system: theoretical aspects and visual evoked potentials to homogeneous red and green stimuli

We designed visual evoked potentials experiments to study the differential aspects of colour and brightness coding in man. The substitution of equally bright red and green stimuli for a background yellow was investigated and compared with different luminance increments and decrements of red and green. A dominant N87 component was found for a colour change from yellow to brighter red colours, which was less pronounced for green and absent for yellow luminance changes. It is also absent for pure red luminance increments and green luminance changes, but reappears with red luminance decrements or red-offset. The data are discussed within the framework of a new concept of how the visual system fuses red-green information and black-white border information. Retinal X-cells can transmit colour and high spatial frequency achromatic information simultaneously by encoding only the presence of edges (a.c.) for the black-white stimuli and the presence of both edges (a.c.) and uniform areas of colour (d.c.) for red-green stimuli. Phylogenetically this kind of information transmission enables colour vision to be implemented in a retina such as the cat's by adding only a second class of cones. Barlow's economy principle will be violated for colour in the periphery, but restored early in the striate cortex where there is an early decoding of the combined chromatic and achromatic information by the concentric double opponent cells. The N87 behaviour correlates with the proposed discharge of peripheral X-type cells, but not with the discharge of cortical double opponent concentric or simple cells, which no longer respond to homogeneous colour stimuli. It is suggested that N87 may be generated by geniculate afferents in the dendritic arborization of cortical cells, reflecting the behaviour of peripheral units, and thus the violation of the economy principle, rather than the next step in cortical processing. The early cortical restoration of the economy principle is supported by the absence of any further dissociated behaviour for colour and brightness in later components.     

Colour categorization by domestic chicks

Spectral stimuli form a physical continuum, which humans divide into discrete non-overlapping regions or categories that are designated by colour names. Little is known about whether non-verbal animals form categories on stimulus continua, but work in psychology and artificial intelligence provides models for stimulus generalization and categorization. We compare predictions of such models to the way poultry chicks (Gallus gallus) generalize to novel stimuli following appetitive training to either one or two colours. If the two training colours are (to human eyes) red and greenish-yellow or green and blue, chicks prefer intermediates, i.e. orange rather than red or yellow and turquoise rather than green or blue. The level of preference for intermediate colours implies that the chicks interpolate between the training stimuli. However, they do not extrapolate beyond the limits set by the training stimuli, at least for red and yellow training colours. Similarly, chicks trained to red and blue generalize to purple, but they do not generalize across grey after training to the complementary colours yellow and blue. These results are consistent with a modified version of a Bayesian model of generalization from multiple examples that was proposed by Shepard and show similarities to human colour categorization.     

Physiological colour changes in Odonata eyes. A comparison between eye and epidermal chromatophore pigment migrations

Pigment migration in the eyes of Austrolestes annulosus and Ischnura heterosticta cause pronounced colour changes which superficially resemble those of Odonata epidermal chromatophores. In both species, the migratory pigment is confined to the distal pigment cells of dorsal ommatidia. When the pigment is concentrated around the base of the crystalline cones, a dense layer of Tyndall blue bodies produce bright ‘blue phase’ colours. Distal migration of the pigment disrupts the Tyndall effect and produces ‘dark phase’ (grey-brown) colours. As in chromatophores, eye pigments consist of a mixture of xanthommatin and dihydroxanthommatin together with an additional pigment, possibly ommin A, not found in chromatophores.As with chromatophores, eye pigments respond to change in temperature only, change in light intensity having no effect. The change from blue to dark phase (at 8°C) occurs at the same rate as in chromatophores, whereas the reverse change (at 20°C) is significantly slower. Equilibrium colours at constant temperature are variable but significantly different from those of chromatophores at 12°C and above. There is no diurnal variation in responsiveness as is found in chromatophores.Isolated dark phase eyes or undamaged pieces of eye are able to change to blue phase after temperature increase. Isolated blue phase eyes show little response to temperature decrease, isolated undamaged pieces show no response. A temperature difference between the eyes of the same intact insect may result in minor colour differences. Ablation of the optic tract or of tissue posterior to the optic tract prevents normal colour change from blue to dark phase. The above results indicate that eye pigment cells are structurally similar to Odonata chromatophores and are under similar environmental and physiological control.     

Learning and discrimination of coloured papers in the walking blowfly,Lucilia cuprina

Summary A new training and testing paradigm for walking sheep blowflies, Lucilia cuprina, is described. A fly is trained by presenting it with a droplet of sugar solution on a patch of coloured paper. After having consumed the sugar droplet, the fly starts a systematic search. While searching, it is confronted with an array of colour marks consisting of four colours displayed on the test cardboard (Fig. 1). Colours used for training and test include blue, green, yellow, orange, red, white and black.Before training, naive flies are tested for their spontaneous colour preferences on the test array. Yellow is visited most frequently, green least frequently (Table 2). Spontaneous colour preferences do not simply depend on subjective brightness (Table 1).The flies trained to one of the colours prefer this colour significantly (Figs. 5 and 9–11). This behaviour reflects true learning rather than sensitisation (Figs. 6–7). The blue and yellow marks are learned easily and discriminated well (Figs. 5, 9, 11). White is also discriminated well, although the response frequencies are lower than to blue and yellow (Fig. 11). Green is discriminated from blue but weakly from yellow and orange (Figs. 5, 9, 10). Red is a stimulus as weak as black (Figs. 8, 9). These features of colour discrimination reflect the spectral loci of colours in the colour triangle (Fig. 14).The coloured papers seem to be discriminated mainly by the hue of colours (Fig. 12), but brightness may also be used to discriminate colour stimuli (Fig. 13).     

Pattern discrimination by the honeybee (Apis mellifera ) is colour blind for radial / tangential cues

Bees were trained to discriminate between two patterns, one of which was associated with a reward, in a Y-choice apparatus with the targets presented vertically at a distance at an angular subtense of 50°. Previous work with this apparatus has found discrimination between two patterns of coloured gratings or radial sectors that are fixed in different orientations during the training. When there was contrast to the blue receptors alone, gratings of period 6° were resolved, and 4° when there was contrast to the green receptors. In the present work, bees discriminate between a pattern containing tangentially arranged edges and one containing radially arranged edges, both with no average edge orientation. The targets were rotated every 5 min to make the locations of areas useless as cues. The edges remained consistently radial or tangential and were therefore the only cues. Tests with patterns of selected colours and various levels of grey show that for each colour there is a level of grey at which discrimination fails. Discrimination is therefore colour-blind. The same patterns were made with combinations of coloured papers that give no contrast to the green receptors or alternatively to the blue receptors. The bees discriminate only if the edges between colours present a contrast to the green receptors. The system that discriminates generalized radial and tangential cues is therefore colour blind because the inputs are restricted to the green receptors, not because receptor outputs are added together. The same result was obtained with a very coarse pattern of period 20°. Accepted: 10 January 1999     

ERPs to words--effect of gender and site of recording electrode

Event-related potentials (ERPs) to word stimuli were registered in 20 twenty-one-year-old students (7 males and 13 females) of the Faculty of Medicine of Palacky University. In an ideal case in the first 800 ms after the onset of stimulus ERP consists of three clear positive and four negative waves. The amplitude of some waves of ERPs shows a high degree of inter-individual variability. It was also revealed that the latency and amplitude of some ERPs waves to word stimuli depends on the gender and on the site of the registration electrode on the scalp of the subject. Latencies of components LP2 and LN4 in all electrodes are shorter in females than in males, component LN2 behaves reversely--its latency is shorter in males. On the other hand, the amplitude of dependent variables BP2, BN2 and PV1 is in most electrodes higher in females than in males--except for the amplitude of components BP4 and BN1.     

Passive perception of auditory stimuli in healthy and mild mentally retarded adolescents from Northern Russia

Event-related potentials (ERPs) during passive perception of auditory stimuli were studied using the oddball paradigm in healthy and mild mentally retarded adolescents. The study involved 25 subjects aged 11–15 (13.1 ± 1.4) years from Northern Russia, including Arctic regions. The peak latency of the difference wave for deviant and standard stimuli in frontal central derivation was 129 ± 21 ms in the healthy children, and the mean amplitude was–2.6 ± 1.3 μV. In the mentally retarded group, a negative peak of the difference wave was observed only in 9 out of 13 adolescents, its latency was more than in the healthy adolescents (156 ± 29 ms), and the mean amplitude was–2.1 ± 1.4 μV. Differences in perception of deviant and standard stimuli were observed in the healthy adolescents, in particular, along the central line. In the adolescents with mental disorders, there was no significant difference in the fronto-central and central derivations. A discriminant analysis of the amplitudes of ERP components observed in the fronto-central derivations in response to deviant stimuli and the difference in amplitude between ERPs evoked in the fronto-central derivation by standard and deviant stimuli differentiated the adolescents with and without mental disorders. Based on the findings, ERP components in the oddball paradigm were assumed to provide potential markers of disorders in mental development.     

Responses of the blister beetle Hycleus apicicornis to visual stimuli

Insect attraction to host plants may be partly mediated by visual stimuli. In the present study, the responses of adult Hycleus apicicornis (Guér.) (Coleoptera: Meloidae) to plant models of different colours, different combinations of two colours, or three hues of blue of different shapes are compared. Single‐colour models comprised the colours sky blue, bright green, yellow, red, white and black. Sky blue (reflecting light in the 440–500 nm region) is the most attractive, followed by white, which reflects light over a broader range (400–700 nm). On landing on sky blue targets, beetles exhibit feeding behaviour immediately. When different hues of blue (of different shapes) are compared, sky blue is preferred over turquoise, followed by dark blue, indicating that H. apicicornis is more attracted to lighter hues of blue than to darker ones. No significant differences are found between the three shapes (circle, square and triangle) tested, suggesting that reflectance associated with colour could be a more important visual cue than shape for host location by H. apicicornis. The preference of H. apicicornis for sky blue can be exploited in designing an attractive trap for its management.     

The visual response from the compound eye of Oncopeltus fasciatus: Effects of temperature and sensory adaptation

The effects of temperature (10–30°C) on response latency and amplitude were determined in the dark- and light-adapted compound eye of the milkweed bug, Oncopeltus fasciatus. Response amplitude was an inverse function of temperature under dark-adapted conditions, but was nearly independent of temperature when superimposed on a background field. Response amplitude to a test stimulus (S₂) was maximum at 15–20°C when presented 10 sec after an adapting stimulus (S₁). The optimum temperature (10°C or less) for maximum response amplitude from dark-adapted eyes was far below the temperature at which the animals were grown (19–25°C) and lower than previously reported for insect compound eyes. These results are discussed in terms of the adaptive implications for diurnal, terrestrial ectotherms.Response latency from dark-adapted eyes was an inverse exponential function of temperature with an apparent activation energy of 13·6 kcal mole⁻¹. No change in activation energy could be attributed to light adaptation.Reductions of S₂ response latency and amplitude, during the adaptation régimes employed in this study, were different functions of temperature. Adapting stimuli, which were equally effective at reducing S₂ latency, had different effects on S₂ response amplitude. Recovery of S₂ response latency and amplitude were not related at either 20 or 10°C. Therefore, changes in S₂ response latency as a function of adaptation appeared independent of changes in S₂ response amplitude.     

Temporal acuity of honeybee vision: behavioural studies using flickering stimuli

ABSTRACT. Temporal resolution of freely-flying bees was measured by training bees, Apis mellifera (Linn.), to discriminate between a steady light and a flickering light. Two kinds of experiments were conducted: those using a homochromatic flicker, in which the intensity of the flickering light varied periodically with time; and ones using a heterochromatic flicker, in which the colour of the flickering light varied periodically. In either case, the time-averaged properties (intensity and colour) of the flickering light matched those of the steady light, and the bees' ability to discriminate between the two stimuli was measured for various flicker frequencies. The results indicate that bees perform poorly in the homochromatic flicker experiments, regardless of the colour of the light (u.v., blue or green), but well in those with heterochromatic flicker. Heterochromatic flicker experiments using various pairwise combinations of the colours U.V., blue and green (corresponding to the three known spectral receptor-types in the bee's retina) reveal that temporal resolution is much better when blue is one of the component colours, than when it is not. The simplest interpretation of the results is in terms of colour channels possessing different response speeds. Heterochromatic flicker promises to be a useful tool in investigating the temporal properties of colour vision in bees.     

Median and tibial nerve somatosensory evoked potentials: middle-latency components from the vicinity of the secondary somatosensory cortex in humans

The topography of the middle-latency N110 after radial nerve stimulation suggested a generator in SII. To support this hypothesis, we have tried to identify a homologous component in the tibial nerve SEP (somatosensory evoked potential). Evoked potentials following tibial nerve stimulation (motor+sensory threshold) were recorded with 29 electrodes (bandpass 0.5–500 Hz, sampling rate 1000 Hz). For comparison, the median nerve was stimulated at the wrist. Components were identified as peaks in the global field power (GFP). Map series were generated around GFP peaks and amplitudes were measured from electrodes near map maxima. With median nerve stimulation, we recorded a negativity with a maximum in temporal electrode positions and 106±12 ms peak latency (mean±SD), comparable to the N110 following radial nerve stimulation. After tibial nerve stimulation the latency of a component with the same topography was 131±11 ms (N130). Both N110 and N130 were present ipsi- as well as contralaterally. Amplitudes were significantly higher on the contralateral than the ipsilateral scalp for both median (3.1±2.4 μV vs. 1.7±1.6 μV) and tibial nerve (1.9±1.2 μV vs. 0.6+1 μV). The topography of the N130 can be explained by a generator in the vicinity of SII. The latency difference between median and tibial nerve stimulation is related to the longer conduction distance (cf. N20 and P40). The smaller ipsilateral N130 is consistent with the bilateral body representation in SII.     

Effects of environmental colour on growth of Nile tilapia, Oreochromis niloticus (Linnaeus, 1758), maintained individually or in groups

Examined was the influence of different colours of light on the growth of adult Nile tilapia (Oreochromis niloticus) held either individually (initial size 12.8 ± 1.1 cm; 62.9 ± 15.6 g) or in groups (initial size 7.8 ± 0.8 cm; 17.2 ± 6.4 g). Various colours (blue 434.5 nm, violet 430.0 nm, red 609.7 nm, green 525.2 nm and yellow 545.2 nm) did not affect weight gain of fish held individually (initial to final weights: blue 62.5 ± 18.4 to 72.9 ± 16.0 g, violet 63.5 ± 17.8 to 78.0 ± 19.1 g, green 62.1 ± 13.0 to 72.9 ± 15.7 g, and yellow 60.4 ± 20.4 to 71.0 ± 21.1 g); red seemed to restrict growth (initial to final weights: 65.8 ± 13.3 to 71.8 ± 10.8 g). Final weight differences were observed among individuals in groups maintained under blue, violet, red and green light (smaller and larger fish: blue 13.2 ± 5.0 and 18.9 ± 7.0 g, violet 17.3 ± 5.2 and 23.8 ± 4.7 g, red 14.7 ± 3.3 and 23.9 ± 4.7 g, and green 19.4 ± 7.8 and 28.6 ± 8.1 g); however, under the yellow light there were no differences in final weights (smaller fish 19.1 ± 4.8 g; larger fish 26.2 ± 5.2 g). Under the red light, heterogeneity in growth was observed earlier than with the other colours. It is therefore suggested that the red colour might have some harmful effects on Nile tilapia growth, limiting weight gain when fish are individually maintained, and with weight differences increasing when fish are held in groups. On the other hand, the yellow light seems to be positive for Nile tilapia, as it appears not to affect individually‐held fish, but reduces variation in growth of group‐maintained fish, promoting growth homogeneity.     

Single-trial latency variability does not contribute to fast habituation of the long-latency averaged auditory evoked potential in the albino rat

Fas habituation (FH) is defined as a general reduction in long-latency, vertex-recorded, averaged auditory evoked potential (AEP) amplitude that occurs in response to the second of a pair of acoustic stimuli. Our laboratory has been studying FH in a variety of human populations with different paradigms and has interpreted it to be a measure of neural attentional mechanism(s) and/or resource allocation related to the processing of cognitive information. We have also reported an analogous phenomenon in the rat. In the present investigation, we examined the relationship between FH (viz., averaged AEP component amplitude decrement) and the single-trial latency variability of the AEP peaks comprising that component. Specifically, AEPs were obtained to 60 paired-tone stimuli from unanesthetized and restrained albino rats previously implanted with chronic skull electrodes. Using a template-matching algorithm similar to that used by Michalewski et al. (Electroenceph. clin. Neurophysiol., 1986, 65:59–71), the latency variability for each animal was computed for the N1 and P2 peaks of the single-trial AEPs that were used to compose the averaged wave form. Findings indicated that (a) there was no difference in single-trial latency variability for these peaks either within or across tones, and (b) there was no relationship between single-trial latency variability for either the N1 or the P2 peaks and the overall peak-to-peak amplitude (N1-P2) of the averaged wave form in response to the second tone. Thus, FH of the N1-P2 (i.e. Peak 2) amplitude in the rat is not due to an increase in latency variability across tones.     

Visual evoked potentials elicited by a moving unidimensional noise pattern

(1) Motion onset and offset visual evoked potentials (VEPs) were recorded in normal human subjects using a unidimensional noise pattern moving at 1, 8 and 64°/s. The maximum N1-P1 amplitude of the motion onset response was obtained when using a fine noise pattern (maximum energy at 5.2 cpd) moving at 8°/s. (2) At a velocity of 8°/s, the motion onset response (fine pattern, 0.70 contrast) showed a morphology similar to the pattern disappearance response. Both at a lower (1°/s) and a higher velocity (64°/s) the N1-P1 amplitude of the motion onset complex was significantly reduced. The latency of the motion onset response (8°/s) and the pattern disappearance complex were significantly different. (3) The effect of lowering the spatial content of the noise pattern on the amplitude of the motion onset response was different for the 3 velocities tested: the largest effect was at the lower velocity of 1°/s; there was no similar effect on the pattern disappearance response. (4) With decreasing contrast, the N1-P1 amplitude of the motion onset response at 8°/s decreased, but this reduction in amplitude was much less than that of the disappearance response. The contrast dependency of the motion onset complex was identical for binocular and monocular recordings. (5) Increasing the motion duration or the duration of the interstimulus interval did not alter the general morphology of the motion response.     

The 4-dimensional spherical color space in the monkey]

Discrimination of colours by macaque rhesus was studied by the method of elaboration of differentiation inhibition of instrumental conditioned responses to colour stimuli. Matrix of probabilities of instrumental reactions to presentation of colour stimuli, the columns of which corresponded to the colours applied, and the lines--to series of experiments with definite reinforced colour--was processed by the method of factor analysis. Four factors describing the used colours in four-dimensional Euclidean space were singled out. Spatial structure of the seven used colours satisfies the equation of four-dimensional sphere. Two first factors are interpreted as colour-opponent red-green and yellow-blue and the third and fourth ones as achromatic light and dark neuronal channels. Perceptive space of colour stimuli based on the data of instrumental behaviour of the monkey corresponds to analogous results obtained by the method of multidimensional scaling of subjective evaluations of super-threshold colour differences for the man.     

Scalp-recorded oscillatory potentials evoked by transient pattern-reversal visual stimulation in man

Replicable oscillatory potentials, time-locked to pattern stimuli (9.0° central; counterphase reversal at 2.13 Hz) were dissociated from conventional, broad-band VEPs recorded in healthy volunteers at occipital scalp locations by high-pass digital filtering at 17.0–20.0 Hz. Nine consecutive wavelets were identified with a 56.4 ± 8.4 msec mean latency of the first replicable wavelet and mean peak-to-peak amplitude varying between 0.9 and 2.0 μV. The first 2 wavelets had significantly shorter latencies than wave N70 of unfiltered VEP, whereas the last 2 wavelets had longer latencies than N145. Latency and amplitude values varied as a function of contrast and spatial frequency of the stimulus, with shorter latencies and larger amplitudes at 60–90% contrast level and tuning of amplitude at 5.0 c/deg. All wavelets were correlated with wave P100 of unfiltered VEP, while a correlation with N70 of VEP was observed only for those wavelets with latencies in the range of wave P100. Two patients with documented brain lesions involving the visual system are described as examples of oscillatory responses occurring irrespective of filter bandpass and instead of the expected conventional VEP when the generation of these is interfered with by brain pathology. A substantial cortical contribution to the origin of the oscillatory response is conceivable. It is suggested that the oscillatory response to pattern-reversal stimulation reflects events in the visual system that are parallel to, and partly independent of, the conventional VEP, with potential application in research or for clinical purposes.     

Plant scents modify innate colour preference in foraging swallowtail butterflies

Flower-visiting insects exhibit innate preferences for particular colours. A previous study demonstrated that naive Papilio xuthus females prefer yellow and red, whereas males are more attracted to blue. Here, we demonstrate that the innate colour preference can be modified by olfactory stimuli in a sexually dimorphic manner. Naive P. xuthus were presented with four coloured discs: blue, green, yellow and red. The innate colour preference (i.e. the colour first landed on) of the majority of individuals was blue. When scent from essential oils of either orange flower or lily was introduced to the room, females’ tendency to select the red disc increased. Scents of lavender and flowering potted Hibiscus rosa-sinensis, however, were less effective. Interestingly, the odour of the non-flowering larval host plant, Citrus unshiu, shifted the preference to green in females. In males, however, all plant scents were less effective than in females, such that blue was always the most favoured colour. These observations indicate that interactions between visual and olfactory cues play a more prominent role in females.     

Visual ecology of aphids—a critical review on the role of colours in host finding

We review the rich literature on behavioural responses of aphids (Hemiptera: Aphididae) to stimuli of different colours. Only in one species there are adequate physiological data on spectral sensitivity to explain behaviour crisply in mechanistic terms. Because of the great interest in aphid responses to coloured targets from an evolutionary, ecological and applied perspective, there is a substantial need to expand these studies to more species of aphids, and to quantify spectral properties of stimuli rigorously. We show that aphid responses to colours, at least for some species, are likely based on a specific colour opponency mechanism, with positive input from the green domain of the spectrum and negative input from the blue and/or UV region. We further demonstrate that the usual yellow preference of aphids encountered in field experiments is not a true colour preference but involves additional brightness effects. We discuss the implications for agriculture and sensory ecology, with special respect to the recent debate on autumn leaf colouration. We illustrate that recent evolutionary theories concerning aphid–tree interactions imply far-reaching assumptions on aphid responses to colours that are not likely to hold. Finally we also discuss the implications for developing and optimising strategies of aphid control and monitoring.