Sub-structure-based category formation for the prioritisation of genotoxicity hazard assessment for pesticide residues (part 2): Triazoles

In dietary risk assessment, residues of pesticidal ingredients or their metabolites need to be evaluated for their genotoxic potential. The European Food Safety Authority recommend a tiered approach focussing assessment and testing on classes of similar chemicals. To characterise similarity and to identify structural alerts associated with genotoxic concern, a set of chemical sub-structures was derived for an example dataset of 66 triazole agrochemicals for which either Ames, chromosomal aberration or micronucleus test results are publicly available. This analysis resulted in a set of ten structural alerts that define the chemical space, in terms of the common parent and metabolic scaffolds, associated with the triazole chemical class. An analysis of the available profiling schemes for DNA and protein reactivity shows the importance of investigating the predictivity of such schemes within a well-defined area of structural space. Structural space alerts, covalent chemistry profiling and physico-chemistry properties were combined to develop chemical categories suitable for chemical prioritisation. The method is a robust and reproducible approach to such read-across predictions, with the potential to reduce unnecessary testing. The key challenge in the approach was identified as being the need for pesticide-class specific metabolism data as the basis for structural space alert development.

Sub-structure-based category formation for the prioritisation of genotoxicity hazard assessment for pesticide residues: Sulphonyl ureas

In dietary risk assessment, residues of pesticidal ingredients or their metabolites need to be evaluated for their genotoxic potential. The European Food Safety Authority recommend a tiered approach focussing assessment and testing on classes of similar chemicals. To characterise similarity and to identify structural alerts associated with genotoxic concern, a set of chemical sub-structures was derived for an example dataset of 74 sulphonyl urea agrochemicals for which either Ames, chromosomal aberration or micronucleus test results are publicly available. This analysis resulted in a set of seven structural alerts that define the chemical space, in terms of the common parent and metabolic scaffolds, associated with the sulphonyl urea chemical class. An analysis of the available profiling schemes for DNA and protein reactivity shows the importance of investigating the predictivity of such schemes within a well-defined area of structural space. Structural space alerts, covalent chemistry profiling and physico-chemistry properties were combined to develop chemical categories suitable for chemical prioritisation. The method is a robust and reproducible approach to such read-across predictions, with the potential to reduce unnecessary testing. The key challenge in the approach was identified as being the need for pesticide-class specific metabolism data as the basis for structural space alert development.

Newborns' neural processing of native vowels reveals directional asymmetries

Prenatal learning of speech rhythm and melody is well documented. Much less is known about the earliest acquisition of segmental speech categories. We tested whether newborn infants perceive native vowels, but not nonspeech sounds, through some existing (proto-)categories, and whether they do so more robustly for some vowels than for others. Sensory event-related potentials (ERP), and mismatch responses (MMR), were obtained from 104 neonates acquiring Czech. The ERPs elicited by vowels were larger than the ERPs to nonspeech sounds, and reflected the differences between the individual vowel categories. The MMRs to changes in vowels but not in nonspeech sounds revealed left-lateralized asymmetrical processing patterns: a change from a focal [a] to a nonfocal [ɛ], and the change from short [ɛ] to long [ɛ:] elicited more negative MMR responses than reverse changes. Contrary to predictions, we did not find evidence of a developmental advantage for vowel length contrasts (supposedly most readily available in utero) over vowel quality contrasts (supposedly less salient in utero). An explanation for these asymmetries in terms of differential degree of prior phonetic warping of speech sounds is proposed. Future studies with newborns with different language backgrounds should test whether the prenatal learning scenario proposed here is plausible.

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Newborns’ processing of native vowels and comparable nonspeech sounds differ.

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Durational and spectral differences in stimuli were more clearly reflected by the ERPs to vowels, compared to tone complexes.

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Directional asymmetries were detected in the mismatch responses to vowel deviants.

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In the left hemisphere, a change in vowels from focal to nonfocal and from short to long resulted in a more negative MMR.

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The findings may be explained by phonetic learning prior to the 3rd day after birth.

Reorganization in the representation of face-race categories from 6 to 9 months of age: Behavioral and computational evidence

Prior research has reported developmental change in how infants represent categories of other-race faces (Developmental Science 19 (2016) 362-371). In particular, Caucasian 6-month-olds were shown to represent African versus Asian face categories, whereas Caucasian 9 month-olds represented different classes of other-race faces in one category, inclusive of African and Asian faces but exclusive of Caucasian faces. The current investigation sought to provide stronger evidence that is convergent with these findings by asking whether infants will generalize looking-time responsiveness from one to another other-race category. In Experiment 1, an experimental group of Caucasian 6-month-olds was familiarized with African (or Asian) faces and then given a novel category preference test with an Asian (or African) face versus a Caucasian face, while a control group of Caucasian 6-month-olds viewed the test faces without prior familiarization. Infants in the experimental group divided attention between the test faces and infants in the control group did not manifest a spontaneous preference. Experiment 2 used the same procedure, but was conducted with Caucasian 9-month-olds. Infants in the experimental group displayed a robust preference for Caucasian faces when considered against the finding that infants in the control group displayed a spontaneous preference for other-race faces. The results offer confirmation that between 6 and 9 months, infants transition to representing own-race versus other-race face categories, with the latter inclusive of multiple other-race face classes with clear perceptual differences. Computational modeling of infant responding suggests that the developmental change is rooted in the statistics of experience with majority versus minority group faces.

People's sensitivity to content vs. formal properties of visual stimuli: Evidence from category construction

When people are asked to classify visual stimuli, they are often insensitive to formal properties, such as their 3D coherence or symmetry. We investigated whether this pattern of formal insensitivity would also be found using more familiar stimuli and properties: paintings that differ in their artistic style and words printed in two different typefaces. The experiments used the category formation paradigm in which subjects freely sort items into groups that seem most natural to them. They could sort each stimulus set up to three times. Only about half of the subjects in Experiment 1 ever sorted the paintings by artistic style, and only 12% did so on their first sort. Only 36% ever sorted by typeface, with many of the subjects stopping after two sorts and saying that no further categories were possible. Experiment 2 repeated the test of typeface using actual words cut out of newspapers and advertisements. Half the words were printed in boldface and half not. These items lacked any strong semantic connections, yet only 30% of subjects ever sorted the items into the bold and non-bold words. The results suggest that many people are not sensitive to the formal properties of stimuli that also have semantic content. Spontaneously noticing those differences may require a particular task with explicit instructions or experience in that domain (e.g., copyeditors or art students).

Can Listeners Hear Who Is Singing? The Role of Listener Experience in Singer Discrimination Across Pitch

OBJECTIVE/HYPOTHESIS

Previous research has shown that listeners are unable to identify who is singing across pitch when the voices are unfamiliar to them. Implementing a very short training period, however, greatly improves this ability, but only when the voices being compared are of different voice category. The objective of this study was to determine whether experienced listeners with highly developed knowledge of voice categories can more easily discriminate between singers across pitch.

METHODS/DESIGN

This study used an ABX paradigm where listeners heard two different singers singing "ah" at the same pitch. Listeners identified which of the two singers produced a third "ah" at a different pitch. Stimuli were recorded from two baritones, two tenors, two mezzo-sopranos, and two sopranos across a 1.5 octave range. Data were collected from 42 inexperienced listeners and 27 experienced listeners.

RESULTS

Experienced listeners were better at singer discrimination across pitch than were inexperienced listeners for all conditions except same-category comparisons at the interval of the third. Experienced listeners were better at singer discrimination across pitch than were slightly trained listeners for all conditions except same-category female singers at all pitch intervals.

CONCLUSIONS

The ability to discriminate singers across pitch is the greatest for experienced listeners, followed by slightly trained inexperienced listeners, followed by inexperienced listeners.

Can Listeners Hear Who Is Singing? The Development of Voice Category Perception

OBJECTIVE AND HYPOTHESIS

This study sought to investigate if a small amount of training in identification of voices elicits the development of prototypical vocal categories.

STUDY DESIGN

This study used a between-group design.

METHODS

This study used an ABX paradigm where listeners heard two different singers singing "ah" at the same pitch. Listeners identified which of the two singers was the producer of a third "ah" at a different pitch. Stimuli were recorded from two baritones, two tenors, two mezzo-sopranos, and two sopranos across a 1.5-octave range. Participants were randomly assigned to two groups, one group that received a training session using voices that were different from those in the experimental session, but of the same voice category, and one group that received no training.

RESULTS

Training listeners with voices that are different from those of singers presented in the experiment did not significantly improve the ability to discriminate individual voices of the same voice category, but did significantly improve that ability to discriminate individual voices when the voices being compared were of different voice categories.

CONCLUSIONS

Small amounts of purposeful exposure to human voices appear to result in the beginnings of listener voice category formation, providing listeners with prototypical categories that can aid them in discrimination of novel voices of those same categories.

Investigation of the Verhaar scheme for predicting acute aquatic toxicity: improving predictions obtained from Toxtree ver. 2.6

Assessment of the potential of compounds to cause harm to the aquatic environment is an integral part of the REACH legislation. To reduce the number of vertebrate and invertebrate animals required for this analysis alternative approaches have been promoted. Category formation and read-across have been applied widely to predict toxicity. A key approach to grouping for environmental toxicity is the Verhaar scheme which uses rules to classify compounds into one of four mechanistic categories. These categories provide a mechanistic basis for grouping and any further predictive modelling. A computational implementation of the Verhaar scheme is available in Toxtree v2.6. The work presented herein demonstrates how modifications to the implementation of Verhaar between version 1.5 and 2.6 of Toxtree have improved performance by reducing the number of incorrectly classified compounds. However, for the datasets used in this analysis, version 2.6 classifies more compounds as outside of the domain of the model. Further amendments to the classification rules have been implemented here using a post-processing filter encoded as a KNIME workflow. This results in fewer compounds being classified as outside of the model domain, further improving the predictivity of the scheme. The utility of the modification described herein is demonstrated through building quality, mechanism-specific Quantitative Structure Activity Relationship (QSAR) models for the compounds within specific mechanistic categories.