Ageing and visual spatiotemporal processing

The Temporal Window of Visual Processing in Aging

Purpose

Aging affects a variety of visual functions. In this study, we aim to quantitatively investigate the temporal characteristics of visual processing in aging.

Methods

Twelve younger (24.1 ± 1.6 years) and 12 older observers (58.4 ± 3.6 years) participated in the study. All participants had normal or corrected-to-normal vision. The contrast thresholds of the participants were measured using an orientation discrimination task with white external noise masks. The target-mask stimulus onset asynchronies were 16.7 ms, 33.4 ms, 50.0 ms, 83.4 ms, and ∞ (no external noise masks) in separate conditions. The signal stimulus was carefully chosen such that it was equally visible for the younger and older participants. An elaborated perceptual template model (ePTM) was fit to the data of each participant.

Results

Without masks, there was no difference in contrast thresholds between the younger and older groups (P = 0.707). With masks, contrast thresholds in the older group elevated more than those in the younger group, and the pattern of threshold elevation differed in the two groups. The ePTM fitted the data well, with the older observers having lower template gains than the younger observers (P = 3.58 × 10-6). A further analysis of the weight parameters of the temporal window revealed that the older observers had a flatter temporal window than the younger observers (P = 0.025).

Conclusions

Age-related temporal processing deficits were found in older observers with normal contrast sensitivity to the signal stimuli. The deficits were accounted for by the inferior temporal processing window of the visual system in aging.

Menstrual cycle irregularity and menopause status influence cognition in women with schizophrenia

Cognitive impairments are a core feature of schizophrenia and contribute significantly to functional complications. Current pharmacological treatments do not ameliorate cognitive dysfunction and the aetiology of cognitive impairments are poorly understood. Hormones of the hypothalamic-pituitary-gonadal (HPG) axis that regulate reproductive function have multiple effects on the development, maintenance and function of the brain and have been suggested to also influence cognition. The aim of the current study was to investigate how HPG axis hormones effect cognition, specifically exploring the influence of menopause status and menstrual cycle irregularity on cognitive performance in women with schizophrenia. The data for the present study represents pooled baseline data from three clinical trials. Two hundred and forty female participants with a diagnosis of schizophrenia or schizoaffective disorder were included in the analysis. Cognition was assessed using the Repeatable Battery for the Assessment of Neuropsychological Status. Hormone assays for serum sex steroids and pituitary hormones (including estradiol, progesterone, luteinising hormone and follicle-stimulating hormone) were conducted and women were classified as postmenopausal; perimenopausal; premenopausal/reproductive, further classified into regular and irregular menstrual cycles. To model a comparison of cognitive performance for i) perimenopausal; ii) post-menopausal women and iii) reproductive aged women with irregular cycles to reproductive aged women with regular cycles a semiparametric regression model (generalised additive mode) was fitted. The results revealed that in females with schizophrenia, menstrual cycle irregularity predicted significantly poorer cognitive performance in the areas of psychomotor speed, verbal fluency and verbal memory. Perimenopause was not associated with cognitive changes and the post-menopausal period was associated with poorer visuospatial performance. This study provides evidence to associate reproductive hormones with cognitive dysfunction in schizophrenia.

Temporal aspects of natural scene categorisation in healthy ageing

The visual system has an extraordinary capability to extract categorical information from complex scenes. Age-related deficits in visual temporal processing have been found with both low-level and high-level stimuli. However, it is unknown to which extent those deficits extend to the processing of complex scenes. Here, we investigated the temporal characteristics of natural scene categorisation in healthy ageing. Using a backward masking paradigm, we asked young-old (aged 59-70), old-old (aged 70+) and younger adults (18-31years) to perform a go/no-go task, in which they had to respond to images of animals whilst ignoring images of landscapes. Both age groups were overall faster and more accurate in responding to the target images as the stimulus onset asynchrony (SOA) between target image and mask increased. Older adults, especially those in the old-old group, were significantly less accurate than younger adults for short SOAs but performed equally well at long SOAs. However, we found no age-difference in reaction times. Our findings suggest that the temporal processing of complex scenes is impaired in healthy older adults independently of reduced motor abilities. They also indicate that such deficits in natural scene categorisation become more evident with increasing age. Our findings might have important implications for the wellbeing of older adults and road safety in general.

Spatial and temporal aspects of visual backward masking in children and young adolescents

The development of visual functions is very diverse. Some visual functions mature within the first year of life, whereas maturation for other functions extends into adolescence. The reasons for these developmental differences are largely unknown. Here, we investigated spatiotemporal processing in children (7–9 years, n = 15), young adolescents (11–13 years, n = 26), and adults (18–33 years, n = 24) using the shine-through visual backward-masking paradigm. We found that children had significantly longer vernier durations than either young adolescents or adults. However, children’s spatial and temporal processing of complex masks was very similar to that of young adolescents and adults. We suggest that spatiotemporal processing related to visual backward masking is already fully developed at age 7, whereas the attentional processes related to target enhancement only mature in young adolescence.