The nonlinearity of pupil diameter fluctuations in an insight task as criteria for detecting children who solve the problem from those who do not.

Insights, characterized by sudden discoveries following unsuccessful problem-solving attempts, are fascinating phenomena. Dynamic systems perspectives argue that insight arises from self-organizing perceptual and motor processes. Entropy and fractal scaling are potential markers for emerging new and effective solutions. This study investigated whether specific features associated with self-organization in dynamical systems can distinguish between individuals who succeed and those who fail in solving insight tasks. To achieve this, we analyzed pupillary diameter fluctuations of children aged 6 to 12 during the 8-coin task, a well-established insight task. The participants were divided into two groups: successful (n = 24) and unsuccessful (n = 43) task completion. Entropy, determinism, recurrence ratio, and the ß scaling exponent were estimated using Recurrence Quantification and Power Spectrum Density analyses. The results indicated that the solver group exhibited more significant uncertainty and lower predictability in pupillary diameter fluctuations before finding the solution. Recurrence Quantification Analysis revealed changes that went unnoticed by mean and standard deviation measures. However, the ß scaling exponent did not differentiate between the two groups. These findings suggest that entropy and determinism in pupillary diameter fluctuations can identify early differences in problem-solving success. Further research is needed to determine the exclusive role of perceptual and motor activity in generating insights and investigate these results' generalizability to other tasks and populations.

Impact of acute psychosocial stress on attentional control in humans. A study of evoked potentials and pupillary response.

Psychosocial stress has increased considerably in our modern lifestyle, affecting global mental health. Deficits in attentional control are cardinal features of stress disorders and pathological anxiety. Studies suggest that changes in the locus coeruleus-norepinephrine system could underlie the effects of stress on top-down attentional control. However, the impact of psychosocial stress on attentional processes and its underlying neural mechanisms are poorly understood. This study aims to investigate the effect of psychosocial stress on attentional processing and brain signatures. Evoked potentials and pupillary activity related to the oddball auditory paradigm were recorded before and after applying the Montreal Imaging Stress Task (MIST). Electrocardiogram (ECG), salivary cortisol, and subjective anxiety/stress levels were measured at different experimental periods. The control group experienced the same physical and cognitive effort but without the psychosocial stress component. The results showed that stressed subjects exhibited decreased P3a and P3b amplitude, pupil phasic response, and correct responses. On the other hand, they displayed an increase in Mismatch Negativity (MMN). N1 amplitude after MIST only decreased in the control group. We found that differences in P3b amplitude between the first and second oddball were significantly correlated with pupillary dilation and salivary cortisol levels. Our results suggest that under social-evaluative threat, basal activity of the coeruleus-norepinephrine system increases, enhancing alertness and decreasing voluntary attentional resources for the cognitive task. These findings contribute to understanding the neurobiological basis of attentional changes in pathologies associated with chronic psychosocial stress.

Non-Miotic Improvement in Binocular Near Vision with a Topical Compound Formula for Presbyopia Correction.

INTRODUCTION: The aim of this case series was to examine the association between unaided binocular visual acuity for near vision and pupil change after the instillation of a special topical formulation for presbyopia treatment. METHODS: This was a case series consisting of consecutive participants with presbyopia aged 40-70 years who were tested for visual acuity and pupil diameter before and 2 h after instillation of a formulation of pilocarpine and phenylephrine drops (FOV Tears) for presbyopia. Participants underwent subjective refraction, photopic and scotopic pupil diameter measurement and unaided monocular and binocular visual acuity testing by logMAR for distance and near vision both pre- and post-instillation of eye drops. RESULTS: The study enrolled 363 subjects (n = 176 women, 48%) with a mean (± standard deviation) age of 50.4 ± 5.8 years. Mean spherical equivalent (SE) changed significantly (- 0.17 Diopters) after instillation of the FOV Tears formulation (p < 0.001). Post-instillation of eye drops, the scotopic pupil diameter decreased by 0.97 ± 0.98 mm, and the near visual acuity by logMAR improved significantly by nearly two lines (p < 0.01). In the linear regression analyses, age (p < 0.001) and SE pre-drop instillation (p < 0.001) were associated with unaided binocular visual acuity. The changes in photopic pupil diameter and the scotopic pupil diameter were not associated with unaided binocular visual acuity. CONCLUSIONS: The use of the pilocarpine and phenylephrine formulation (FOV Tears) improved binocular visual acuity for near vision in presbyopic patients, and the effect was independent of pupil change.

Ophthalmic effects of dexmedetomidine, methadone and dexmedetomidine-methadone in healthy cats and their reversal with atipamezole.

OBJECTIVES: The aims of this study were to evaluate and compare the effects that dexmedetomidine and methadone, either alone or in combination, have on the ocular variables of healthy adult cats when administered intramuscularly, as well as their reversal with atipamezole. METHODS: A randomized crossover blinded study of 10 healthy cats was used to assess the effect of 0.2 mg/kg methadone (MET), 7.5 µg/kg dexmedetomidine (D7), 10 µg/kg dexmedetomidine (D10), 7.5 µg/kg dexmedetomidine and 0.2 mg/kg methadone (DM7) and 10 µg/kg dexmedetomidine and 0.2 mg/kg methadone (DM10) on intraocular pressure (IOP), tear production and pupil diameter (PD). The animals were evaluated for 30 mins. Afterwards, atipamezole was administered and ocular variables were evaluated for 30 mins. RESULTS: D10, DM7 and DM10 significantly decreased mean IOP but MET or D7 did not. Tear production decreased significantly in all treatments, corresponding to 18%, 59%, 63%, 86% and 98% in MET, D7, D10, DM7 and DM10, respectively. PD increased in all treatments, but MET showed the highest PD. Thirty minutes after atipamezole (RT30), IOP returned to baseline with no difference between groups, and there was a significant increase in tear production, but the means were still different from baseline. CONCLUSIONS AND RELEVANCE: Dexmedetomidine decreases IOP and tear production but increases PD in healthy cats. Atipamezole can partly reverse those alterations. Low-dose dexmedetomidine (7.5 µg/kg) promotes sedation without changing the IOP. All protocols significantly decrease tear production, and Schirmer tear test after sedation is not representative of non-sedated values. Methadone induces quick onset mydriasis without changing the IOP.

Relationship between facial attractiveness and pupil diameter in young adults / Relação entre a atratividade facial e diâmetro pupilar em adultos jovens / Relación entre atratividad facial y diámetro de la pupila en adultos jóvenes

The objective of this study was to investigate whether there is a relationship between pupil diameter and facial attractiveness. Participated in the study 60 young adults (30 men and 30 women) between 18 and 26 years of age (M=20.65, SD=2.20). Ten different unfamiliar neutral faces (five men and five women) were used as stimuli. The pupil diameter of each face was manipulated with pupil diameters of 2, 3, 4, 5 and 6mm (10 faces x5 pupil diameters=50 stimuli). A two-step study was carried out with the same sample and the same sets of faces, seeking to understand the difference of responses between subjects of both sexes. In phase I, result indicated a significant difference in relation to the pupil diameter factor for both the men (ꭓ²=21.93, p<.05) and the women (ꭓ²=44.73, p<.05). In phase II, the results indicated significant differences in relation to the pupil size [F(1, 234)=19.06, p<0.05]. The post-hoc Tukey HSD test showed that both the men and the women differently judged the faces with a pupil diameter of 2mm in relation to the faces with pupil diameters of 3, 4, 5 and 6mm (p<.05). Also, a significant difference between the diameter of 5mm in relation to the diameter of 3mm (p<.05). In general, the results indicate that the pupil diameter is a structural component of the human face that plays an important role in the process of judging facial attractiveness.

O objetivo deste estudo foi investigar a relação entre o diâmetro da pupila e a atratividade facial. Participaram da pesquisa 60 jovens com idade entre 18 e 26 anos. Foram utilizadas dez faces de adultos jovens, manipulou-se o diâmetro de cada pupila com variações de 2, 3, 4, 5 e 6mm. Realizou-se um estudo em duas etapas: na fase I, o resultado indicou diferença significativa para o fator de diâmetro pupilar tanto para homens quanto para mulheres (p<0,05). Na fase II, os resultados indicaram diferenças significativas em relação ao tamanho da pupila (p<0,05). O teste post-hoc Tukey mostrou que tanto os homens quanto as mulheres avaliaram diferentemente as faces com diâmetro pupilar de 2mm (p<0,05). Em geral, os resultados indicam que o diâmetro da pupila é um componente da face humana que desempenha um importante função no processo de julgamento da atratividade facial.

El objetivo de este estudio fue investigar si existe una relación entre el diámetro pupilar y el atractivo facial. Participaron en la estudio 60 adultos jóvenes (30 hombres y 30 mujeres) entre 18 y 26 años de edad (M=20.65, DE=2.20). Se utilizaron como estímulos diez rostros neutrales desconocidos diferentes (cinco hombres y cinco mujeres). El diámetro de la pupila de cada cara se manipuló con diámetros de pupila de 2, 3, 4, 5 y 6mm (10 caras x5 diámetros de pupila=50 estímulos). Se realizó un estudio en dos etapas con la misma muestra y los mismos conjuntos de caras buscando entender la diferencia de respuestas entre sujetos de ambos sexos. En la fase I, el resultado indicó una diferencia significativa en relación al factor de diámetro de la pupila tanto para los hombres (ꭓ²=21.93, p <0.05) como para las mujeres (ꭓ²=44.73, p<0.05). En la fase II, los resultados indicaron diferencias significativas en relación al tamaño de la pupila [F(1, 234)=19,06, p<0,05]. La prueba post-hoc de Tukey HSD mostró que tanto los hombres como las mujeres evaluaron de manera diferente las caras con un diámetro pupilar de 2mm con respecto a las caras con diámetros pupilares de 3, 4, 5 y 6mm (p<0,05). Se observó una diferencia significativa entre el diámetro de 5mm en relación al diámetro de 3mm (p<0,05). En general, los resultados indican que el diámetro de la pupila es un componente estructural de la cara humana que desempeña una importante función en el proceso de juicio del atractivo facial.