The number of colors discernible by normal trichromats has been estimated for the idealized object-color solid. How well these estimates apply to natural scenes is an open question, as it is unknown how much their colors approach the theoretical limits. The aim of this work was to estimate the number of discernible colors based on a database of hyperspectral images of 50 natural scenes. The color volume of each scene was computed in the CIELAB color space and was analyzed using the CIEDE2000 color-difference formula. It was found that the color volume of the set of natural scenes was about 30% of the theoretical maximum for the full object-color solid, and it corresponded to a number of about 2.3 million discernible colors. Moreover, when the lightness dimension was ignored, only about 26,000 (1%) could be perceived as different colors. These results suggest that natural stimuli may be more constrained than expected from the analysis of the theoretical limits.

Persistent postsurgical pain (PPSP) is a major clinical problem with significant individual, social, and healthcare costs. The aim of this study was to examine the role of demographic, clinical, and psychological risk factors in the development of PPSP after hysterectomy due to benign disorders. In a prospective study, a consecutive sample of 186 women was assessed 24 hours before surgery (T1), 48 hours after surgery (T2), and 4 months after surgery (T3). Regression analyses were performed to identify predictors of PPSP. Four months after hysterectomy, 93 (50%) participants reported experiencing pain (numerical rating scale >0). Age, pain due to other causes, and type of hysterectomy emerged as significant predictive factors. Baseline presurgical psychological predictors identified were anxiety, emotional illness representation of the condition leading to surgery, and pain catastrophizing. Among the identified psychological predictors, emotional illness representation emerged as the strongest. Acute postsurgical pain frequency and postsurgical anxiety also revealed a predictive role in PPSP development. These results increase the knowledge on PPSP predictors and point healthcare professionals toward specific intervention targets such as anxiety (presurgical and postsurgical), pain catastrophizing, emotional illness representations, and acute pain control after surgery.Perspective: This study found that presurgical anxiety, emotional illness representations, and pain catastrophizing are risk factors for PPSP 4 months after hysterectomy, over and above age and clinical variables. These findings improve knowledge on PPSP and highlight potential intervention targets for healthcare professionals.

This article reveals the significant influence of psychological factors on the prediction of acute pain and anxiety 48 hours after primary total hip and knee arthroplasty. These results could prove useful for the design of interventions aimed at postsurgical pain and anxiety management.