Roughness perception through fingertip contact with a textured surface can involve spatial and temporal cues from skin indentation and vibration respectively. Both types of cue may be affected by contact forces when feeling a surface and we ask whether, on a given trial, discrimination performance relates to contact forces. We examine roughness discrimination performance in a standard psychophysical method (2-interval forced choice, in which the participant identifies which of two spatial textures formed by parallel grooves feels rougher) while continuously measuring the normal and tangential forces applied by the index finger. Fourteen participants discriminated spatial gratings in fine (spatial period of 320-580 micron) and coarse (1520-1920 micron) ranges using static pressing or sliding contact of the index finger. Normal contact force (mean and variability) during pressing or sliding had relatively little impact on accuracy of roughness judgments except when pressing on surfaces in the coarse range. Discrimination was better for sliding than pressing in the fine but not the coarse range. In contrast, tangential force fluctuations during sliding were strongly related to roughness judgment accuracy.

Mimicry by avian brood parasites favours uniformity over variation within a breeding attempt as host defence against parasitism. In a cuckoo-host system from New Caledonia, the arms race resulted in both host (Gerygone flavolateralis) and parasite (Chalcites lucidus) having nestlings of two discrete skin colour phenotypes, bright and dark. In our study sites, host nestlings occurred in monomorphic and polymorphic broods, whereas cuckoo nestlings only occurred in the bright morph. Irrespective of their brood colour, host parents recognised and ejected parasite nestlings but never ejected their own. We investigated whether host parents visually recognised their own nestlings by using colour, luminance and pattern of multiple body regions. We found that the parasite mimicked multiple visual features of both host morphs and that the visual difference between host morphs was larger than the difference between the parasite and the mimicked host morph. Visual discrimination alone may result in higher chances of recognition errors in polymorphic than in monomorphic host broods. Host parents may rely on additional sensorial cues, not only visual, to assess nestling identity. Nestling polymorphism may be a trace of evolutionary past and may only have a marginal role in true-recognition of nestlings in the arms race in New Caledonia.

Effects of type 2 diabetes on achromatic and chromatic contrast sensitivity (CS) are still controversial. In this study, we aimed to investigate CS in patients without diabetic retinopathy (no-DR) and in those with non-proliferative DR (NPDR) and proliferative DR (PDR) using psychophysical methods with transient and sustained achromatic stimuli and color patches. Achromatic CS was measured with the pulsed pedestal (PP) paradigm (7, 12, and 19 cd/m2) and pedestal-△-pedestal (P-△-P) paradigm (11.4, 18, and 28.5 cd/m2). A chromatic discrimination paradigm that assesses protan, deutan, and tritan color vision was adopted. Forty-two patients (no-DR n = 24, NPDR n = 12, PDR = 6; male n = 22, mean age = 58.1 y/o) and 38 controls (male n = 18, mean age = 53.4 y/o) participated. In patients, mean thresholds were higher than in controls and linear trends were significant in most conditions. For the PP paradigm, differences were significant in the PDR and NPDR groups in the 7 and 12 cd/m2 condition. For the P-△-P paradigm, differences were only significant in the PDR group in the 11 cd/m2 condition. Chromatic contrast loss was significant in the PDR group along the protan, deutan and tritan axes. The results suggest independent involvements of achromatic and chromatic CS in diabetic patients.

In humans, aging and neurodegenerative diseases have been found to be associated with impairment in both mathematical abilities and estimation of continuous quantities such as size, weight or distance. Zebrafish (Danio rerio) is rapidly becoming a model for human aging and brain disorders but we currently lack any instrument for rapid assessment of quantity estimation abilities in this species. Here we developed a simple method based on spontaneous preference of zebrafish for using the larger available hole to pass an obstacle. We collected a large amount of data from small groups of zebrafish moving between compartments of their tank and we used these normative data to compare the performance of individually tested fish. Zebrafish significantly discriminated size ratios from 0.60 to 0.91 with their performance decreasing while increasing the size ratio between the smaller and the larger hole presented. On average, individually tested fish showed the same performance, but a large inter-individual variability was observed. Test-retest analyses revealed a good reliability of this test, with 0.60 and 0.75 ratios being the most informative. Experience did not affect individual performance, suggesting the suitability of this test to measure the longitudinal changes and the effects of pharmacological treatments on cognitive abilities.

Recent studies show that training the approximate number system (ANS) holds promise for improving symbolic math abilities. Extending this line of research, the present study aims to shed light on incentive motivation of numerosity discrimination and the underlying mechanisms. Thirty-two young adults performed a novel incentivized dot comparison task, that we developed, to discern the larger of two numerosities. An EZ-diffusion model was applied to decompose motivational effects on component processes of perceptual decision-making. Furthermore, phasic pupil dilation served as an indicator of the involvement of the salience network. The results of improved accuracy and a higher information accumulation rate under the reward condition suggest that incentive motivation boosts the precision of the ANS. These novel findings extend earlier evidence on reward-related enhancements of perceptual discrimination to the domain of numerosity perception. In light of the Adaptive Gain Theory, we interpret the results in terms of two processes of gain modulation driven by the locus coeruleus-norepinephrine system. Specifically, the reward-induced increase in pupil dilation may reflect incentive modulation of (i) salience attention during reward anticipation towards incentivized stimuli to upregulate stimulus processing that results in a larger drift rate; and (ii) response caution that leads to an increased decision threshold.

Perception is modulated by ongoing brain oscillations. Psychophysical studies show a voluntary action can synchronize oscillations, producing rhythmical fluctuations of visual contrast sensitivity. We used signal detection to examine whether voluntary action could also synchronize oscillations in decision criterion, and whether that was due to the oscillations of perceptual bias or of motor bias. Trials started with a voluntary button-press. After variable time lags, a grating at threshold contrast was presented briefly and participants discriminated its orientation (45° or -45°) with a mouse-click. Two groups of participants completed the experiment with opposite mappings between grating orientations and response buttons. We calculated sensitivity and criterion in the 800 ms period following the button press. To test for oscillations, we fitted first-order Fourier series to these time series. Alpha oscillations occurred in both sensitivity and criterion at different frequencies: ~8 Hz (sensitivity) and ~10 Hz (criterion). Sensitivity oscillations had the same phase for both stimulus-response mappings. Criterion oscillations, however, showed a strong anti-phase relationship when the two groups were compared, suggesting a motor bias rather than perceptual bias. Our findings suggest two roles for alpha oscillations: in sensitivity, reflecting rhythmic attentional inhibition, and in criterion, indicating dynamic motor-related anticipation or preparation.

Translational recognition memory research makes frequent use of the Novel Object Recognition (NOR) paradigm in which animals are simultaneously presented with one new and one old object. The preferential exploration of the new as compared to the old object produces a metric, the Discrimination Ratio (DR), assumed to represent recognition memory sensitivity. Human recognition memory studies typically assess performance using signal detection theory derived measures; sensitivity (d') and bias (c). How DR relates to d' and c and whether they measure the same underlying cognitive mechanism is, however, unknown. We investigated the correspondence between DR (eye-tracking-determined), d' and c in a sample of 37 humans. We used dwell times during a visual paired comparison task (analogous to the NOR) to determine DR, and a separate single item recognition task to derive estimates of response sensitivity and bias. DR was found to be significantly positively correlated to sensitivity but not bias. Our findings confirm that DR corresponds to d', the primary measure of recognition memory sensitivity in humans, and appears not to reflect bias. These findings are the first of their kind to suggest that animal researchers should be confident in interpreting the DR as an analogue of recognition memory sensitivity.

Phonetic discrimination learning is an active perceptual process that operates under the influence of cognitive control mechanisms by increasing the sensitivity of the auditory system to the trained stimulus attributes. It is assumed that the auditory cortex and the brainstem interact in order to refine how sounds are transcribed into neural codes. Here, we evaluated whether these two computational entities are prone to short-term functional changes, whether there is a chronological difference in malleability, and whether short-term training suffices to alter reciprocal interactions. We performed repeated cortical (i.e., mismatch negativity responses, MMN) and subcortical (i.e., frequency-following response, FFR) EEG measurements in two groups of participants who underwent one hour of phonetic discrimination training or were passively exposed to the same stimulus material. The training group showed a distinctive brainstem energy reduction in the trained frequency-range (i.e., first formant), whereas the passive group did not show any response modulation. Notably, brainstem signal change correlated with the behavioral improvement during training, this result indicating a close relationship between behavior and underlying brainstem physiology. Since we did not reveal group differences in MMN responses, results point to specific short-term brainstem changes that precede functional alterations in the auditory cortex.

Strategies designed to increase adult hippocampal neurogenesis (AHN) may have therapeutic potential for reversing memory impairments. H3 receptor antagonists/inverse agonists also may be useful for treating cognitive deficits. However, it remains unclear whether these ligands have effects on AHN. The present study aimed to investigate the effects of a 28-day treatment with S 38093, a novel brain-penetrant antagonist/inverse agonist of H3 receptors, on AHN (proliferation, maturation and survival) in 3-month-old and in aged 16-month-old mice. In addition, the effects of S 38093 treatment on 7-month-old APPSWE Tg2576 transgenic mice, a model of Alzheimer's disease, were also assessed. In all tested models, chronic treatment with S 38093 stimulated all steps of AHN. In aged animals, S 38093 induced a reversal of age-dependent effects on hippocampal brain-derived neurotrophic factor (BDNF) BDNF-IX, BDNF-IV and BDNF-I transcripts and increased vascular endothelial growth factor (VEGF) expression. Finally, the effects of chronic administration of S 38093 were assessed on a neurogenesis-dependent "context discrimination (CS) test" in aged mice. While ageing altered mouse CS, chronic S 38093 treatment significantly improved CS. Taken together, these results provide evidence that chronic S 38093 treatment increases adult hippocampal neurogenesis and may provide an innovative strategy to improve age-associated cognitive deficits.

The early detection of cognitive impairment or dementia is in the focus of current research as the amount of cognitively impaired individuals will rise intensely in the next decades due to aging population worldwide. Currently available diagnostic tools to detect mild cognitive impairment (MCI) or dementia are time-consuming, invasive or expensive and not suitable for wide application as required by the high number of people at risk. Thus, a fast, simple and sensitive test is urgently needed to enable an accurate detection of people with cognitive dysfunction and dementia in the earlier stages to initiate specific diagnostic and therapeutic interventions. We examined digital Clock Drawing Test (dCDT) kinematics for their clinical utility in differentiating patients with amnestic MCI (aMCI) or mild Alzheimer's dementia (mAD) from healthy controls (HCs) and compared it with the diagnostic value of the Consortium to Establish a Registry for Alzheimer's Disease (CERAD) neuropsychological battery total score. Data of 381 participants (138 patients with aMCI, 106 patients with mAD and 137 HCs) was analyzed in the present study. All participants performed the clock drawing test (CDT) on a tablet computer and underwent the CERAD test battery and depression screening. CERAD total scores were calculated by subtest summation, excluding MMSE scores. All tablet variables (i.e. time in air, time on surface, total time, velocity, pressure, pressure/velocity relation, strokes per minute, time not painting, pen-up stroke length, pen-up/pen-down relation, and CDT score) during dCDT performance were entered in a forward stepwise logistic regression model to assess, which parameters best discriminated between aMCI or mAD and HC. Receiver operating characteristics (ROC) curves were constructed to visualize the specificity in relation to the sensitivity of dCDT variables against CERAD total scores in categorizing the diagnostic groups. dCDT variables provided a slightly better diagnostic accuracy of 81.5% for discrimination of aMCI from HCs than using CERAD total score (accuracy 77.5%). In aMCI patients with normal CDT scores, both dCDT (accuracy 78.0%) and CERAD total scores (accuracy 76.0%) were equally accurate in discriminating against HCs. Finally, in differentiating patients with mAD from healthy individuals, accuracy of both dCDT (93.0%) and CERAD total scores (92.3%) was excellent. Our findings suggest that dCDT is a suitable screening tool to identify early cognitive dysfunction. Its performance is comparable with the time-consuming established psychometric measure (CERAD test battery).

Past research on the effects of associative aversive learning on discrimination acuity has shown mixed results, including increases, decreases, and no changes in discrimination ability. An animal study found that the type of learning experience determined the direction and extent of learning-induced changes. The current preregistered web-based study aimed to translate these findings to humans. Experiment 1 (N = 245) compared changes in stimulus discrimination between simple learning (only one oriented grating cue), coarse differential conditioning (physically distinct cues), and fine differential conditioning (physically similar cues) as well as to their three respective control groups. The discrimination task consisted of a two-alternative-forced-choice task with oriented grating stimuli. During learning, a specific orientation was paired with unpleasant pictures. Our analysis using generative modeling demonstrated weak to moderate evidence that aversive learning did not alter discrimination acuity in any of the groups. In a follow-up experiment (N = 121), we replicated these findings despite successful learning trajectories in all three groups and a more detailed assessment of discrimination acuity. Contrary to prior assumptions, our findings indicate that aversive learning does not enhance perceptual discrimination, and the presence of additional safety cues does not appear to moderate this effect.

Prolonged mesolimbic dopamine concentration changes have been detected during spatial navigation, but little is known about the conditions that engender this signaling profile or how it develops with learning. To address this, we monitored dopamine concentration changes in the nucleus accumbens core of rats throughout acquisition and performance of an instrumental action sequence task. Prolonged dopamine concentration changes were detected that ramped up as rats executed each action sequence and declined after earned reward collection. With learning, dopamine concentration began to rise increasingly earlier in the execution of the sequence and ultimately backpropagated away from stereotyped sequence actions, becoming only transiently elevated by the most distal and unexpected reward predictor. Action sequence-related dopamine signaling was reactivated in well-trained rats if they became disengaged in the task and in response to an unexpected change in the value, but not identity of the earned reward. Throughout training and test, dopamine signaling correlated with sequence performance. These results suggest that action sequences can engender a prolonged mode of dopamine signaling in the nucleus accumbens core and that such signaling relates to elements of the motivation underlying sequence execution and is dynamic with learning, overtraining and violations in reward expectation.

Action preparation can facilitate performance in tasks of visual perception, for instance by speeding up responses to action-relevant stimulus features. However, it is unknown whether this facilitation reflects an influence on early perceptual processing, or instead post-perceptual processes. In three experiments, a combination of psychophysics and electroencephalography was used to investigate whether visual features are influenced by action preparation at the perceptual level. Participants were cued to prepare oriented reach-to-grasp actions before discriminating target stimuli oriented in the same direction as the prepared grasping action (congruent) or not (incongruent). As expected, stimuli were discriminated faster if their orientation was congruent, compared to incongruent, with the prepared action. However, action-congruency had no influence on perceptual sensitivity, regardless of cue-target interval and discrimination difficulty. The reaction time effect was not accompanied by modulations of early visual-evoked potentials. Instead, beta-band (13-30 Hz) synchronization over sensorimotor brain regions was influenced by action preparation, indicative of improved response preparation. Together, the results suggest that action preparation may not modulate early visual processing of orientation, but likely influences higher order response or decision related processing. While early effects of action on spatial perception are well documented, separate mechanisms appear to govern non-spatial feature selection.

Clozapine-N-oxide (CNO) has long been the ligand of choice for selectively activating Designer Receptors Exclusively Activated by Designer Drugs (DREADDs). However, recent studies have challenged the long-held assertion that CNO is otherwise pharmacologically inert. The present study aimed to 1) determine whether CNO is reverse-metabolized to its parent compound clozapine in mice (as has recently been reported in rats), and 2) determine whether CNO exerts clozapine-like interoceptive stimulus effects in rats and/or mice. Following administration of 10.0 mg/kg CNO, pharmacokinetic analyses replicated recent reports of back-conversion to clozapine in rats and revealed that this phenomenon also occurs in mice. In rats and mice trained to discriminate 1.25 mg/kg clozapine from vehicle, CNO (1.0-20.0 mg/kg) produced partial substitution for the clozapine stimulus on average, with full substitution being detected in some individual animals of both species at doses frequently used to activate DREADDs. The present demonstration that CNO is converted to clozapine and exerts clozapine-like behavioral effects in both mice and rats further emphasizes the need for appropriate control groups in studies employing DREADDs, and highlights the utility of the drug discrimination procedure as a tool with which to screen the off-target effects of novel DREADD agonists.

Insufficient sleep is a global public health problem resulting in catastrophic accidents, increased mortality, and hundreds of billions of dollars in lost productivity. Yet the effect of sleep deprivation (SD) on decision making and performance is often underestimated by fatigued individuals and is only beginning to be understood by scientists. The deleterious impact of SD is frequently attributed to lapses in vigilant attention, but this account fails to explain many SD-related problems, such as loss of situational awareness and perseveration. Using a laboratory study protocol, we show that SD individuals can maintain information in the focus of attention and anticipate likely correct responses, but their use of such a top-down attentional strategy is less effective at preventing errors caused by competing responses. Moreover, when the task environment requires flexibility, performance under SD suffers dramatically. The impairment in flexible shifting of attentional control we observed is distinct from lapses in vigilant attention, as corroborated by the specificity of the influence of a genetic biomarker, the dopaminergic polymorphism DRD2 C957T. Reduced effectiveness of top-down attentional control under SD, especially when conditions require flexibility, helps to explain maladaptive performance that is not readily explained by lapses in vigilant attention.

When anthropogenic noise occurs simultaneously with an acoustic signal or cue, it can be difficult for an animal to interpret the information encoded within vocalizations. However, limited research has focused on how anthropogenic noise affects the identification of acoustic communication signals. In songbirds, research has also shown that black-capped chickadees (Poecile atricapillus) will shift the pitch and change the frequency at which they sing in the presence of anthropogenic, and experimental noise. Black-capped chickadees produce several vocalizations; their fee-bee song is used for mate attraction and territorial defence, and contains information about dominance hierarchy and native geographic location. Previously, we demonstrated that black-capped chickadees can discriminate between individual female chickadees via their fee-bee songs. Here we used an operant discrimination go/no-go paradigm to discern whether the ability to discriminate between individual female chickadees by their song would be impacted by differing levels of anthropogenic noise. Following discrimination training, two levels of anthropogenic noise (low: 40 dB SPL; high: 75 dB SPL) were played with stimuli to determine how anthropogenic noise would impact discrimination. Results showed that even with low-level noise (40 dB SPL) performance decreased and high-level (75 dB SPL) noise was increasingly detrimental to discrimination. We learned that perception of fee-bee songs does change in the presence of anthropogenic noise such that birds take significantly longer to learn to discriminate between females, but birds were able to generalize responding after learning the discrimination. These results add to the growing literature underscoring the impact of human-made noise on avian wildlife, specifically the impact on perception of auditory signals.

The human visual system has specialised mechanisms for encoding mirror-symmetry and for detecting symmetric motion-directions for objects that loom or recede from the observers. The contribution of motion to mirror-symmetry perception has never been investigated. Here we examine symmetry detection thresholds for stationary (static and dynamic flicker) and symmetrically moving patterns (inwards, outwards, random directions) with and without positional symmetry. We also measured motion detection and direction-discrimination thresholds for horizontal (left, right) and symmetrically moving patterns with and without positional symmetry. We found that symmetry detection thresholds were (a) significantly higher for static patterns, but there was no difference between the dynamic flicker and symmetrical motion conditions, and (b) higher than motion detection and direction-discrimination thresholds for horizontal or symmetrical motion, with or without positional symmetry. In addition, symmetrical motion was as easy to detect or discriminate as horizontal motion. We conclude that whilst symmetrical motion per se does not contribute to symmetry perception, limiting the lifetime of pattern elements does improve performance by increasing the number of element-locations as elements move from one location to the next. This may be explained by a temporal integration process in which weak, noisy symmetry signals are combined to produce a stronger signal.

How we perceive a visual stimulus can be influenced by its surrounding context. For example, the presence of a reference skews the perception of a similar feature in a stimulus, a phenomenon called reference repulsion. Ongoing research so far remains inconclusive regarding the stage of visual information processing where such repulsion occurs. We examined the influence of a reference on late visual processing. We measured the repulsion effect caused by an orientation reference presented after an orientation ensemble stimulus. The participants' reported orientations were significantly biased away from the post-stimulus reference, displaying typical characteristics of reference repulsion. Moreover, explicit discrimination choices between the reference and the stimulus influenced the magnitudes of repulsion effects, which can be explained by an encoding-decoding model that differentiates the re-weighting of sensory representations in implicit and explicit processes. These results support the notion that reference repulsion may arise at a late decision-related stage of visual processing, where different sensory decoding strategies are employed depending on the specific task.

The purpose of this study is to explore Dvl3 variants and their interaction with negative life events on MDD susceptibility in a Chinese Han population. Additionally, we also attempted to identify whether there is an association between Dvl3 variants and pro-inflammatory cytokines. A total of 1102 participants, consisting of 550 patients with MDD and 552 healthy subjects, were recruited for genotyping by TaqMan allelic discrimination assay. Pro-inflammatory cytokine mRNA levels in peripheral blood were measured by QPCR. After the assessment of negative life events by the Life Events Scale, the Dvl3 gene-environment interaction (G × E) and risk factors were evaluated using generalized multifactor dimensionality reduction method (GMDR) and logistic regression analysis, respectively. This study is the first to reveal the interaction between Dvl3 allelic variations and negative life events as well as pro-inflammatory cytokines on MDD susceptibility in a Chinese Han population.

A major task of episodic memory is to create unique, distinguishable representations of highly overlapping perceptual inputs. Several studies on this basic function have shown that it is based on the intact functioning of certain subregions of the hippocampus and is among the most sensitive behavioral indicators of mild cognitive impairment (MCI) and dementia. Here we assessed pupil dilation associated with performance in a widely used recognition paradigm that aims to uncover the intactness of fine-graded mnemonic discrimination. A sample of healthy undergraduate students was used. First, we showed that the correct discrimination between highly similar lure items and target items elicit larger pupil response than correct target identification. Second, we found that mnemonic discrimination is associated with larger pupil response in general as compared to target identification, regardless of whether the response was correct or not. These results suggest the pupil changes differentiate mnemonic discrimination and memory identification processes in recognition performance.