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Visually guided perceptual decisions involve the sequential activation of a hierarchy of cortical areas. It has been hypothesized that a brief time window of activity in each area is sufficient to enable the decision but direct measurements of this time window are lacking. To address this question, we develop a visual discrimination task in mice that depends on visual cortex and in which we precisely control the time window of visual cortical activity as the animal performs the task at different levels of difficulty. We show that threshold duration of activity in visual cortex enabling perceptual discrimination is between 40 and 80 milliseconds. During this time window the vast majority of neurons discriminating the stimulus fire one or no spikes and less than 16% fire more than two. This result establishes that the firing of the first visually evoked spikes in visual cortex is sufficient to enable a perceptual decision.

Fear generalization is a prominent feature of anxiety disorders and post-traumatic stress disorder (PTSD). It is defined as enhanced fear responding to a stimulus that bears similarities, but is not identical to a threatening stimulus. Pattern separation, a hippocampal-dependent process, is critical for stimulus discrimination; it transforms similar experiences or events into non-overlapping representations. This study is the first in humans to investigate the extent to which fear generalization relies on behavioral pattern separation abilities. Participants (N = 46) completed a behavioral task taxing pattern separation, and a neuroimaging fear conditioning and generalization paradigm. Results show an association between lower behavioral pattern separation performance and increased generalization in shock expectancy scores, but not in fear ratings. Furthermore, lower behavioral pattern separation was associated with diminished recruitment of the subcallosal cortex during presentation of generalization stimuli. This region showed functional connectivity with the orbitofrontal cortex and ventromedial prefrontal cortex. Together, the data provide novel experimental evidence that pattern separation is related to generalization of threat expectancies, and reduced fear inhibition processes in frontal regions. Deficient pattern separation may be critical in overgeneralization and therefore may contribute to the pathophysiology of anxiety disorders and PTSD.

INTRODUCTION Complex perceptual discrimination is supported by tau‐vulnerable regions of the medial temporal lobe (MTL); notably the perirhinal cortex. This research tests whether there is a gene‐dose effect of apolipoprotein E (APOE) e4 on perceptual discrimination in mid‐life. METHODS Three hundred and thirteen adults (45–65 years; grouped by APOE e4 gene‐dose (142 APOE33, 135 APOE34, 36 APOE44)) completed a Greebles “odd‐one‐out” task. RESULTS APOE44 carriers were significantly less accurate in their perceptual judgments than APOE33 and APOE34 individuals. There was a significant Age x APOE e4 gene‐dose interaction in response speed, with the slope of age‐related slowing increasing stepwise with the number of e4 alleles carried. Estimates suggest high‐risk individuals are quicker than the APOE33 control group until age 54, but slower thereafter. DISCUSSION Perceptual disadvantages specific to APOE44 individuals suggest this high‐risk group show compromised MTL function by mid‐life, potentially through accelerated tau‐aggregation. Task performance in APOE34 carriers is relatively preserved in mid‐life. Highlights APOE44 carriers show impaired perceptual discrimination in mid‐age. APOE34 carriers show preserved perceptual discrimination in mid‐age. Age‐related slowing of perceptual judgments increases with APOE e4 gene‐dose. Perceptual discrimination tasks may be a valuable early marker of AD risk.

Selective stopping is demanded in situations where responses must be suppressed to certain signals, but not others. To explore this type of inhibition, the standard stop-signal task has been modified to include a selective implementation of response inhibition by introducing a new stimulus that participants should ignore. However, a stimulus-selective stop-signal task can be performed following different strategies. Some participants fulfill the selective implementation of the stopping process after discriminating the stop and ignore signals, but some others stop the ongoing response whenever any new stimulus appears. The factors that influence this strategy choice are being explored, where both task and participant variables are under consideration. This study aimed to investigate whether the difficulty in discriminating between stop and ignore signals influences strategy adoption. Additionally, we examined whether participants modify their strategy in a flexible manner throughout the task in alternating easy and hard discrimination condition blocks. In the easy discrimination condition, the stop and the ignore signals differed both in color and shape, whereas in the hard discrimination condition, they only differed in shape. Our results from 64 participants revealed that manipulating the difficulty of signal discrimination strongly influenced strategy choice. Also, we found that participants can adapt their strategy according to task demands. They preferentially adopted a selective stopping strategy when discrimination was easy, whereas they changed to a nonselective stopping strategy under the hard discrimination condition. Overall, results from the current study suggest that signal discrimination difficulty influences the adoption of strategies in selective stopping.

Determining one’s confidence in a decision is a vital part of decision-making. Traditionally, psychological experiments have assessed a person’s confidence by eliciting confidence judgments. The notion that such judgments can be elicited without impacting the accuracy of the decision has recently been challenged by several studies which have shown reactivity effects—either an increase or decrease in decision accuracy when confidence judgments are elicited. Evidence for the direction of reactivity effects has, however, been decidedly mixed. Here, we report three studies designed to specifically make reactivity effects more prominent by eliciting confidence judgment contemporaneously with perceptual decisions. We show that confidence judgments elicited contemporaneously produce an impairment in decision accuracy, this suggests that confidence judgments may rely on a partially distinct set of cues/evidence than the primary perceptual decision and, additionally, challenges the continued use of confidence ratings as an unobtrusive measure of metacognition.

In this paper, I defend a new theory of the nature and individuation of perceptual capacities. I argue that we need a theory of perceptual capacities to explain modal facts about what sorts of perceptual phenomenal states one can be in. I defend my view by arguing for three adequacy constraints on a theory of perceptual capacities: perceptual capacities must be individuated at least partly in terms of their place in a hierarchy of capacities, where these capacities include the senses themselves; an adequate account of perceptual capacities must be sensitive to empirical considerations; and an adequate account should accommodate the nature of the capacity to perceive. I arrive at these constraints by considering how Schellenberg’s view fails, before defending and developing my alternative in line with the constraints. I defend a view on which there are few, coarse-grained perceptual capacities which can fulfil complex explanatory roles because they are evaluatively gradable on many axes. Finally, on my view, perceptual capacities bear a particularly close relation to the sensory modalities themselves.

Somatic sensation comprises four main modalities, each relaying tactile, thermal, painful, or pruritic (itch) information to the central nervous system. These input channels can be further classified as subserving a sensory function of spatial and temporal localization, discrimination, and provision of essential information for controlling and guiding exploratory tactile behaviours, and an affective function that is widely recognized as providing the afferent neural input driving the subjective experience of pain, but not so widely recognized as also providing the subjective experience of affiliative or emotional somatic pleasure of touch. The discriminative properties of tactile sensation are mediated by a class of fast-conducting myelinated peripheral nerve fibres - A-beta fibres - whereas the rewarding, emotional properties of touch are hypothesized to be mediated by a class of unmyelinated peripheral nerve fibres - CT afferents (C tactile) - that have biophysical, electrophysiological, neurobiological, and anatomical properties that drive the temporally delayed emotional somatic system. CT afferents have not been found in the glabrous skin of the hand in spite of numerous electrophysiological explorations of this area. Hence, it seems reasonable to conclude that they are lacking in the glabrous skin. A full understanding of the behavioural and affective consequences of the differential innervation of CT afferents awaits a fuller understanding of their function. La sensation somatique comprend quatre grandes modalités, chacune relayant de l'information tactile, thermique ou pruritique (démangeaison) au système nerveux central. Ces voies d'entrée peuvent être encore classifiées comme servant une fonction sensorielle de localisation spatiale et temporelle, la discrimination et la provision de renseignements essentiels pour contrôler et guider les comportements tactiles exploratoires, ainsi que comme une fonction qui est largement reconnue comme fournissant l'intrant neuronal afférent qui dirige l'expérience subjective de la douleur, mais qui est aussi moins connue comme fournissant l'expérience subjective du plaisir somatique affiliatif ou émotionnel du toucher. Les propriétés discriminatives de la sensation tactile sont médiées par une classe de fibres nerveuses périphériques conductrices myélinisées (fibres A bêta), alors que les propriétés émotionnelles réconfortantes du toucher sont, hypothétiquement, médiées par une classe de fibres nerveuses périphériques amyéliniques (fibres afférentes C tactiles) qui possèdent des propriétés biophysiques, électrophysiologiques, neurobiologiques et anatomiques qui dirigent le système somatique émotionnel temporairement retardé. Malgré de nombreuses explorations électrophysiologiques, aucune fibre afférente C tactile n'a été trouvée sur la peau glabre de la main. Il semble donc raisonnable de conclure qu'elles sont absentes de la peau glabre. La compréhension complète des conséquences comportementales et affectives de l'innervation différentielle des fibres afférentes C tactiles dépend d'une plus grande compréhension de leur fonction.

Individuals show astonishing variability in their face recognition abilities, and the causes and consequences of this heterogeneity are unclear. Special expertise with faces, for example in portraitists, is associated with advantages on face processing tasks, especially those involving perceptual abilities. Do face processing skills improve through practice, or does drawing skill reflect pre-existing individual differences? If the latter, then the association between face processing skills and production of faithful portraits should also exist in people without practice in drawing. Two exploratory studies and one follow-up confirmatory study provide support for this hypothesis. Drawing ability of novices was predicted by their performance on face recognition tasks involving perceptual discrimination and visual short-term memory, but not by those that rely more heavily on long-term memory or memory for non-face objects. By examining non-experts, we show that expertise with faces might build upon pre-existing individual differences in face processing skills.

The Global Neuronal Workspace (GNW) hypothesis states that the visual percept is available to conscious awareness only if recurrent long-distance interactions among distributed brain regions activate neural circuitry extending from the posterior areas to prefrontal regions above a certain excitation threshold. To directly test this hypothesis, we trained 14 human participants to increase blood oxygenation level-dependent (BOLD) signals with real-time functional magnetic resonance imaging (rtfMRI)-based neurofeedback simultaneously in four specific regions of the occipital, temporal, insular and prefrontal parts of the brain. Specifically, we hypothesized that the up-regulation of the mean BOLD activity in the posterior–frontal brain regions lowers the perceptual threshold for visual stimuli, while down-regulation raises the threshold. Our results showed that participants could perform up-regulation (Wilcoxon test, session 1: p = 0.022; session 4: p = 0.041) of the posterior–frontal brain activity, but not down-regulation. Furthermore, the up-regulation training led to a significant reduction in the visual perceptual threshold, but no substantial change in perceptual threshold was observed after the down-regulation training. These findings show that the up-regulation of the posterior–frontal regions improves the perceptual discrimination of the stimuli. However, further questions as to whether the posterior–frontal regions can be down-regulated at all, and whether down-regulation raises the perceptual threshold, remain unanswered.

In a recent report, Winkel, Keuken, van Maanen, Wagenmakers & Forstmann ( Psychonomics Bulletin and Review 21 (3): 777–784, 2014 ) show that during a random-dot motion discrimination task, early differences in motion evidence can influence reaction times (RTs) and error rates in human subjects. They use this as an argument in favor of the drift-diffusion model and against the urgency-gating model. However, their implementation of the urgency-gating model is incomplete, as it lacks the low-pass filter that is necessary to deal with noisy input such as the motion signal used in their experimental task. Furthermore, by focusing analyses solely on comparison of mean RTs they overestimate how long early information influences individual trials. Here, we show that if the urgency-gating model is correctly implemented, including a low-pass filter with a 250 ms time constant, it can successfully reproduce the results of the Winkel et al. experiment.