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If a mental image is a rerepresentation of a perception, then properties such as luminance or brightness should also be conjured up in the image. We monitored pupil diameters with an infrared eye tracker while participants first saw and then generated mental images of shapes that varied in luminance or complexity, while looking at an empty gray background. Participants also imagined familiar scenarios (e.g., a \"sunny sky\" or a \"dark room\") while looking at the same neutral screen. In all experiments, participants' eye pupils dilated or constricted, respectively, in response to dark and bright imagined objects and scenarios. Shape complexity increased mental effort and pupillary sizes independently of shapes' luminance. Because the participants were unable to voluntarily constrict their eyes' pupils, the observed pupillary adjustments to imaginary light present a strong case for accounts of mental imagery as a process based on brain states similar to those that arise during perception.

A relative afferent pupillary defect (RAPD) is a characteristic clinical sign of optic neuritis (ON). Here, we systematically evaluated ultrasound pupillometry (UP) for the detection of an RAPD in patients with ON, including a comparison with infrared video pupillometry (IVP), the gold standard for objective pupillometry. We enrolled 40 patients with acute (n = 9) or past (n = 31) ON (ON+), 31 patients with multiple sclerosis (MS) without prior ON, and 50 healthy controls (HC) in a cross-sectional observational study. Examinations comprised the swinging flashlight test, B-mode UP, IVP, autorefraction to assess the best-corrected visual acuity, optical coherence tomography to determine peripapillary retinal nerve fiber layer thickness, and the 51-item National Eye Institute-Visual Function Questionnaire to determine the vision-related quality of life. While UP and IVP measurements of pupil diameter (PD) at rest correlated in ON+ eyes (n = 52, r = 0.56, 95% CI: 0.35; 0.72) and in HC eyes (n = 100, r = 0.60, 95% CI: 0.47; 0.72), PD at rest was smaller in UP than in IVP measurements (difference, mean (SD) ON+ eyes: 0.44 (0.87) mm, HC eyes: 0.69 (0.80) mm). RAPD assessment by UP sharply discriminated acute ON eyes (n = 9) and HC eyes (n = 100, AUC = 1, 95%CI: 1; 1). UP detected an RAPD in 5/31 (16%) patients with MS without prior ON who had not exhibited an RAPD during the swinging flashlight test. In ON+ eyes (n = 52), UP showed stronger correlations with visual acuity (r = 0.66, 95% CI: 0.50; 0.78) and vision-related quality of life (r = 0.47, 95% CI: 0.24; 0.66) than IVP (r = 0.52, 95% CI: 0.36; 0.67 and r = 0.27, 95% CI: 0.03; 0.51). B-mode UP allows for objective detection and quantification of an RAPD with performance characteristics similar to IVP. RAPD assessment by UP may detect subclinical optic nerve damage in patients with MS. We propose a standardized protocol for RAPD detection by UP that can be used in routine clinical evaluation of patients with ON or other optic neuropathies.

Adaptive gain theory proposes that the dynamic shifts between exploration and exploitation control states are modulated by the locus coeruleus-norepinephrine system and reflected in tonic and phasic pupil diameter. This study tested predictions of this theory in the context of a societally important visual search task: the review and interpretation of digital whole slide images of breast biopsies by physicians (pathologists). As these medical images are searched, pathologists encounter difficult visual features and intermittently zoom in to examine features of interest. We propose that tonic and phasic pupil diameter changes during image review may correspond to perceived difficulty and dynamic shifts between exploration and exploitation control states. To examine this possibility, we monitored visual search behavior and tonic and phasic pupil diameter while pathologists (N = 89) interpreted 14 digital images of breast biopsy tissue (1,246 total images reviewed). After viewing the images, pathologists provided a diagnosis and rated the level of difficulty of the image. Analyses of tonic pupil diameter examined whether pupil dilation was associated with pathologists' difficulty ratings, diagnostic accuracy, and experience level. To examine phasic pupil diameter, we parsed continuous visual search data into discrete zoom-in and zoom-out events, including shifts from low to high magnification (e.g., 1× to 10×) and the reverse. Analyses examined whether zoom-in and zoom-out events were associated with phasic pupil diameter change. Results demonstrated that tonic pupil diameter was associated with image difficulty ratings and zoom level, and phasic pupil diameter showed constriction upon zoom-in events, and dilation immediately preceding a zoom-out event. Results are interpreted in the context of adaptive gain theory, information gain theory, and the monitoring and assessment of physicians' diagnostic interpretive processes.

In the Zone argues that challenge is an essential element of true learning, without which there can be no progress. It brings together supportive materials to encourage teachers to reflect on their present practice, take sensible risks with their teaching, and understand the importance of enjoyment and engagement for both teachers and pupils.At a time when test and examination results still dominate the educational landscape, there is a need to focus on, and support teachers with, the real meaning and purpose of learning. In the Zone concerns itself with important aspects of learning that are not always prominent in government policy and legislation. In particular, it argues that challenge is an essential element of true learning, without which there can be no progress. It brings together supportive materials aimed at encouraging teachers to reflect on their present practice, take sensible risks with their teaching, and understand the importance of enjoyment and engagement for both teachers and pupils. Importantly, the book is fully up to date with the new Ofsted Education Inspection Framework and current thinking around positive pupil mental health.\"In the Zone is a concise and accessible book focused on children's learning and how, as a teacher, we can maximise this, both at school and beyond...It is hard to strike the right balance and the author helps with this by offering questions or tasks at the end of each chapter providing structured reflection and prompts to relate the content to personal practice and experience. Furthermore the author's use of a wide range of research, opinions and visual aids alongside real life examples was thought provoking. Therefore the book is ideal as a point of reference if you want to try something new or want to be reminded of personal key motivators for becoming a teacher.\" Isabelle Gulliver, University of Buckingham  

The rapid pupillary constriction to an abrupt light stimulus is signaled through an oligosynaptic neural pathway that dominates over other supranuclear influences on pupillary movement. A pupillometric recording of the pupil light reflex shows the steep change in pupil size from baseline to maximal constriction. However, when the pupil is recorded in darkness in the phase after light stimulation or in response to non-light stimuli like a sudden noise or cognitive activity, pupil size changes are small and slow. In such cases, pre-processing of pupil recordings to reduce the noise due to intrusion of various artifactual and non-evoked pupillary movements is particularly important but may be time-consuming. To address the paucity of automated tools for pupil light reflex analysis in pupillometry, we aimed to develop a software for automated, user-guided pupillometric data analysis. We identified two types of commonly observed artifacts on pupil recordings. We designed a software, called PupilMetrics, which imports and displays raw pupil data, detects and removes these two types of artifacts, and quantifies outcome measures like pupil size, response time, maximal contraction amplitude and PIPR. The right pupil of 29 healthy adults was recorded using a Neurolight pupillometer (IDMed, Marseilles) in response to 9 different light stimuli. Data analysis of the total 261 pupil responses were performed manually or automatically using PupilMetrics. High correlation was observed between PupilMetrics and manual analysis outcome measures across all stimuli (average R 2  = 0.9891 and p  < 0.0001) with a near 1-to-1 correspondence (Beta = 0.9940). PupilMetrics reduced the total analysis time from 30 h to under 1 h. PupilMetrics offers a time-efficient alternative to manual processing and delivers comparable results. Such software can facilitate standardization of pupillometry for clinical and research uses.

To increase computational flexibility, the processing of sensory inputs changes with behavioural context. In the visual system, active behavioural states characterized by motor activity and pupil dilation 1 , 2 enhance sensory responses, but typically leave the preferred stimuli of neurons unchanged 2 – 9 . Here we find that behavioural state also modulates stimulus selectivity in the mouse visual cortex in the context of coloured natural scenes. Using population imaging in behaving mice, pharmacology and deep neural network modelling, we identified a rapid shift in colour selectivity towards ultraviolet stimuli during an active behavioural state. This was exclusively caused by state-dependent pupil dilation, which resulted in a dynamic switch from rod to cone photoreceptors, thereby extending their role beyond night and day vision. The change in tuning facilitated the decoding of ethological stimuli, such as aerial predators against the twilight sky 10 . For decades, studies in neuroscience and cognitive science have used pupil dilation as an indirect measure of brain state. Our data suggest that, in addition, state-dependent pupil dilation itself tunes visual representations to behavioural demands by differentially recruiting rods and cones on fast timescales. Computational modelling and functional imaging of awake, active mice show that behaviour directly changes neuronal tuning in the visual cortex through pupil dilation.

Background Elevated intracranial pressure (ICP) is frequent after traumatic brain injury (TBI) and may cause abnormal pupillary reactivity, which in turn is associated with a worse prognosis. Using automated infrared pupillometry, we examined the relationship between the Neurological Pupil index (NPi) and invasive ICP in patients with severe TBI. Methods This was an observational cohort of consecutive subjects with severe TBI (Glasgow Coma Scale [GCS] < 9 with abnormal lesions on head CT) who underwent parenchymal ICP monitoring and repeated NPi assessment with the NPi-200® pupillometer. We examined NPi trends over time (four consecutive measurements over intervals of 6 h) prior to sustained elevated ICP > 20 mmHg. We further analyzed the relationship of cumulative abnormal NPi burden (%NPi values < 3 during total ICP monitoring time) with intracranial hypertension (ICHT)—categorized as refractory (ICHT-r; requiring surgical decompression) vs. non-refractory (ICHT-nr; responsive to medical therapy)—and with the 6-month Glasgow Outcome Score (GOS). Results A total of 54 patients were studied (mean age 54 ± 21 years, 74% with focal injuries on CT), of whom 32 (59%) had ICHT. Among subjects with ICHT, episodes of sustained elevated ICP ( n  = 43, 172 matched ICP-NPi samples; baseline ICP [T − 6 h ] 14 ± 5 mmHg vs. ICPmax [T 0 h ] 30 ± 9 mmHg) were associated with a concomitant decrease of the NPi (baseline 4.2 ± 0.5 vs. 2.8 ± 1.6, p  < 0.0001 ANOVA for repeated measures). Abnormal NPi values were more frequent in patients with ICHT-r ( n  = 17; 38 [3–96]% of monitored time vs. 1 [0–9]% in patients with ICHT-nr [ n  = 15] and 0.5 [0–10]% in those without ICHT [ n  = 22]; p  = 0.007) and were associated with an unfavorable 6-month outcome (15 [1–80]% in GOS 1–3 vs. 0 [0–7]% in GOS 4–5 patients; p  = 0.002). Conclusions In a selected cohort of severe TBI patients with abnormal head CT lesions and predominantly focal cerebral injury, elevated ICP episodes correlated with a concomitant decrease of NPi. Sustained abnormal NPi was in turn associated with a more complicated ICP course and worse outcome.

Violation of expectation (VOE) paradigms are key to understanding infants’ early knowledge. In VOE paradigms, infants are presented sequences of events either according with or violating regularities of their physical or social environment. Infants’ violated expectations may result in a surprise response, such as longer looking times or specific neural correlates. There is an increasing interest in utilizing infants’ pupil dilation as an index of their surprise. However, to date, no study has systematically examined infants’ pupillary response across different VOE paradigms. In this preregistered study, we measured 9- to 10-month-olds’ pupil dilation ( N = 21) in response to a common VOE paradigm across four knowledge domains (action, cohesion, number, solidity). In a pre-registered analysis, infants’ pupillary response did not differ between expected and unexpected outcomes in any of these domains. We compared the effect of different analyses parameter choices in a specification curve analysis which revealed that very few choices would have led to significant results. The results demonstrate that across analytical decisions regarding data preprocessing and analysis we do not find evidence for the hypothesized effect. A subsequent permutation test revealed that our original data slightly diverges from randomly shuffled data. We can therefore not unambiguously reject the null hypothesis. We discuss these findings theoretically and methodologically and highlight the need for combining multiple measures to better understand the methods we apply to examine infants’ knowledge about their environment.

Changes in pupil diameter can reflect high-level cognitive signals that depend on central neuromodulatory mechanisms. However, brain mechanisms that adjust pupil size are also exquisitely sensitive to changes in luminance and other events that would be considered a nuisance in cognitive experiments recording pupil size. We implemented a simple auditory experiment involving no changes in visual stimulation. Using finite impulse-response fitting we found pupil responses triggered by different types of events. Among these are pupil responses to auditory events and associated surprise: cognitive effects. However, these cognitive responses were overshadowed by pupil responses associated with blinks and eye movements, both inevitable nuisance factors that lead to changes in effective luminance. Of note, these latter pupil responses were not recording artifacts caused by blinks and eye movements, but endogenous pupil responses that occurred in the wake of these events. Furthermore, we identified slow (tonic) changes in pupil size that differentially influenced faster (phasic) pupil responses. Fitting all pupil responses using gamma functions, we provide accurate characterisations of cognitive and non-cognitive response shapes, and quantify each response's dependence on tonic pupil size. These results allow us to create a set of recommendations for pupil size analysis in cognitive neuroscience, which we have implemented in freely available software.