[Cardio-oncology : a specialty for the future]. / Cardio-oncologie : une discipline en devenir.

Cardio-oncology is a specialty that has rapidly progressed during the last decade. Modern cancer therapies have shown a significant positive impact on the survival of cancer patients. Alongside the progress in oncological treatments came a wide array of cardiac toxicities. The development of cardiotoxicity can lead to unfortunate outcomes. Ensuring the optimal oncological treatment while protecting the heart and vascular system constitute the main objectives of the cardio-oncology unit. Its purpose is to prevent, treat and provide adequate follow-up of patients subject to cardiotoxic drugs.

La cardio-oncologie est une discipline qui a connu un très grand essor ces dernières années. Le développement rapide des nouveaux traitements oncologiques a eu comme effet l'amélioration de la survie des patients mais également leur exposition à une toxicité sur le système cardiovasculaire (cardiotoxicité). Le développement d'une cardiotoxicité a un impact négatif sur la survie de ces patients. Le but de la cardio-oncologie est d'assurer un traitement oncologique optimal tout en protégeant les patients des effets cardiotoxiques. Sa stratégie est de prévenir, identifier et traiter la cardiotoxicité.

Searching for variegated elements.

Visual search performance was investigated for variegated elements that differed from each other either in space-average chromaticity (identical chromatic contrast; Experiment 1) or in the chromatic contrast of the variegation (identical space-average chromaticity; Experiment 2). Specifically, search performance was measured as a function of noise contrast articulated either along the same color direction or orthogonally from the signal (target) variegation. Target-to-distractor difference thresholds were estimated in a two-alternative forced-choice task with briefly presented displays. First, when the signal and noise variegations were articulated along the same direction in color space, elements that differed from each other in space-average chromaticity were less susceptible to noise compared to elements that differed in the contrast of the variegation. Second, orthogonal noise had little effect on threshold supporting independence between the mechanisms mediating these searches. Third, the effect of the noise was similar across the different chromatic directions as well as between observers (but still differed for the two types of variegation) when differences in sensitivity between the various color directions and between observers were taken into account. This last statement only holds because the color space was normalized for each participant.

Induction from a below-threshold chromatic pattern.

Patterned backgrounds can induce large shifts in color appearance, even with patterns of only 10% S-cone contrast (S. K. Shevell & P. Monnier, 2005). The present study tested whether a background pattern could induce color shifts even at a below-threshold contrast. In the first experiment, S-cone contrast threshold for discriminating a pattern from a homogenous background was measured by a 2AFC procedure. Next, a test ring was inserted within the patterned background. With the test ring present, six of eight observers reliably distinguished trials with a patterned background from trials with a homogeneous field, even though the S-cone contrast in the pattern was too low to be discriminated from a homogeneous background. This suggested that a below-threshold S-cone pattern shifted the color appearance of the test ring; that is, the appearance of the test was used to discriminate whether the background was patterned or homogeneous. This was corroborated by asymmetric color matches, which revealed a color shift caused by subthreshold S-cone contrast within the patterned background.

Standard definitions of chromatic induction fail to describe induction with S-cone patterned backgrounds.

Inducing patterns that selectively stimulate the S cones can induce large shifts in color appearance. For example, a "peach" test-ring presented within contiguous purple and non-contiguous lime inducing rings appears pink while the physically identical peach test-ring appears orange when presented within contiguous lime and non-contiguous purple inducing rings (Fig. 1c). These shifts have been accounted for by a neural substrate which predicts that chromatic assimilation and simultaneous contrast can operate synergistically to produce large shifts with these patterns [Monnier, P., & Shevell, S. K. (2004). Chromatic induction from S-cone patterns. Vision Research, 44, 849-856]. Here, induction was measured for test-rings that stimulated the S cones either more or less than did the inducing rings. According to standard definitions of induction, color shifts for test s-chromaticities either lower or higher than both inducing chromaticities should be attenuated compared to test-rings of intermediate S-cone stimulation. On the other hand, a previously proposed model of induction predicted independence of the color shifts with test-ring s-chromaticity. Consistent with standard definitions of induction, a reduction in the magnitude of the color shifts for test-ring chromaticities either lower or higher in S-cone excitation than the inducing chromaticities was observed. Additional measurements with patterns that have been shown to isolate assimilation and simultaneous contrast were conducted. For these patterns, expectations based on standard definitions of induction suggested that the magnitude of the color shifts should be monotonic with the S-cone stimulation of the test-ring, and the direction of the color shift should reverse for test-ring chromaticities either lower or higher than both inducing chromaticities compared to test-rings of intermediate chromaticity. In contrast, the previously proposed model of induction based on a receptive-field with S-cone spatial antagonism predicted the color shifts should be independent of the test-ring chromaticity (Monnier & Shevell, 2004). Color shifts were generally independent of the level of the test-ring chromaticity, supporting the S-cone antagonistic model of induction.

Detection of multidimensional targets in visual search.

Search performance for targets defined along multiple dimensions was investigated with an accuracy visual search task. Initially, threshold was measured for targets that differed from homogeneous distractors along a single dimension (e.g., a reddish target among achromatic distractors, or a right-tilted target among vertically oriented distractors). Threshold was then measured for a multidimensional target (a redundant target) that differed from homogeneous distractors along two dimensions (e.g., a reddish AND right-tilted target among achromatic, vertically oriented distractors). Search performance for multidimensional target combinations of chromaticity and luminance, chromaticity and orientation, and chromaticity and spatial frequency was tested. Measurements were evaluated within several summation models, allowing for a test of the mechanisms mediating the detection of multidimensional targets in search. Measurements were generally consistent with probability summation suggesting the particular combinations of stimulus dimensions tested were coded along independent, noisy, neural mechanisms.

Color shifts induced by S-cone patterns are mediated by a neural representation driven by multiple cone types.

This study investigated chromatic induction from inhomogeneous background patterns. Previous work showed that a background pattern detected by only S cones induced strong color shifts in a nearby test area (Monnier & Shevell, 2003). In that work, the S-cone patterns were composed with constant L- and M-cone stimulation over the entire background; in terms of L and M cones, therefore, the background was uniform. S-cone stimulation was varied over space to produce S-cone-isolated background patterns. These S-cone patterns, however, established spatial structure (the pattern) at both the receptoral level (S-cone stimulation) and the postreceptoral level (S/(L+M)). Here, these two levels of pattern representation were unconfounded to determine whether color shifts induced by S-cone patterns were due to spatial structure within an S-cone-specific neural pathway versus a pathway that combines responses from S cones and other cone types (e.g. S/(L+M)). The results showed that the induced color shifts were mediated by signals within a pathway that combines responses from multiple cone types. These results are consistent with a +s/-s spatially antagonistic neural receptive field, which is found in some neurons in V1 and V2.

Color shifts from S-cone patterned backgrounds: contrast sensitivity and spatial frequency selectivity.

Patterned backgrounds that selectively stimulate the S-cones cause conspicuous color shifts. These shifts are accounted for by an S-cone antagonistic (+S/-S) center-surround receptive field [Monnier, P., & Shevell, S. K. (2004). Chromatic induction from S-cone patterns. Vision Research, 44, 849-856]. The present study tested two additional implications of the S-cone receptive field for color shifts: (1) proportionality of the shifts with respect to S-cone contrast within the inducing pattern and (2) bandpass selectivity of the shifts with respect to the spatial frequency of the inducing pattern. Measurements showed that the magnitude of the color shift was linear with S-cone contrast and that the largest color shift was observed with inducing patterns at an intermediate spatial frequency. These results further support an S-cone spatially antagonistic receptive field as the neural substrate mediating the large color shifts from S-cone patterns.

Influence of motion on chromatic detection.

Intense scrutiny has been focused on whether chromatic stimuli contribute to motion perception. The present study considers a related but different question: how does motion affect chromatic detection? Detection thresholds were measured for a disk that underwent a brief (13.3 ms) chromatic change in the L/(L+M) chromatic direction. The disk's presentation sequence and speed (0-16 deg/s) were manipulated. In the coherent presentation sequence, the disk moved smoothly along a circular path centered on the fixation point. In the random presentation sequence, the disk appeared randomly at positions along the circular path. In both types of sequences, the disk underwent a brief chromatic change midway through the temporal presentation sequence. Threshold was elevated in the coherent condition compared to the random condition, and threshold decreased with an increase in speed. The threshold elevation observed in the coherent presentation sequence can be accounted for by temporal integration. The decrease in threshold with an increase in speed can be accounted for by spatial integration. The results, therefore, can be explained by spatiotemporal integration, without invoking a neural mechanism specialized for motion.

Chromatic induction from S-cone patterns.

Chromatic induction from patterned backgrounds depends on the spatial as well as the chromatic aspects of the background light. Color appearance with patterned and uniform backgrounds was compared using chromaticities distinguished by only the S cones; all backgrounds were equivalent to equal-energy white in terms of L-cone and M-cone stimulation. The measurements showed larger shifts in color appearance with a patterned chromatic background than with a uniform background at any chromaticity within the pattern. The measurements also showed that inducing light within different spatial regions could cause opposite shifts in color appearance: inducing light near a test field shifted appearance toward the inducing chromaticity (assimilation), while the same light some distance from the test shifted appearance away from the inducing chromaticity (simultaneous contrast). The shifts in color appearance were accounted for by a neural receptive field with S-cone spatial antagonism.

Large shifts in color appearance from patterned chromatic backgrounds.

The perceived color of a light varies with the background on which it is seen. In the present study, patterned backgrounds composed of two different chromaticities caused larger shifts in perceived color than did a uniform background at either chromaticity within the pattern. Cortical receptive-field organization, but not optical factors or known retinal neurons, can account for the color shifts from patterned backgrounds.