Smoking prevalence in patients who are diagnosed with schizophrenia (SCZ) is higher than in the general population. Chronic tobacco use in SCZ patients may reduce the side effects of antipsychotic drugs, thus serving as a self-medication for such side effects. Understanding the ways in which chronic tobacco use influences visual sensitivity has clinical implications, which may serve as a tool for non-invasively diagnosing early-stage visual processing deficits. The present study evaluated the effects of chronic tobacco use on visual sensitivity in SCZ patients. Our purpose was to provide new directions for future research, mainly psychophysical and electrophysiological studies. In the present study, 40 smoker controls (SC), 20 SCZ tobacco users, and 20 SCZ tobacco nonusers were recruited from the Psychosocial Care Center. Visual sensitivity was compared between both SCZ groups and the SC group. Patients with SCZ who were chronic tobacco users presented lower visual sensitivity for chromatic (p < 0.001) and achromatic (p < 0.001) stimuli compared with the other groups. Our findings highlight the need to evaluate possible addictive behavior in patients with SCZ, which may contribute to public policies that seek to improve the quality of life of SCZ patients and their families.

This article aims to demonstrate the utilities of Matlab (MATrix LABoratory) and eye-tracker for research in psychophysics and basic processes. We fi rst introduce its origin, functioning, and advantages over other programs, and then we review different applications of Matlab in psychophysical tests involving eye-trackers. As an example, we present the development of a psychophysical test involving eye-tracker and Matlab, showing its ability to communicate and interact with other devices and programming languages. Finally, we emphasize the advantages and diffi culties of working with Matlab.Keywords: Psychophysics, Matlab, Eye-tracker, technological innovation. Matlab e Rastreamento Ocular: Aplicações em Psicofísica e Processos Psicológicos Básicos ResumoEsse artigo teve como objetivo demonstrar a funcionalidade e capacidade do Matlab (MATrix LABoratory) e rastreamento de movimentos oculares (eye-tracker) para pesquisas em psicofísica e processos básicos. Para isso é apresentado primeiramente os fundamentos da criação e funcionamento do Matlab e suas vantagens sobre outros softwares. Em seguida são apresentadas diferentes aplicações do Matlab em testes psicofísicos com rastreadores de movimentos oculares (eyetracker). Também é apresentada a criação de um teste psicofísico em Matlab para um eyetracker e sua capacidade de se

Although some studies have reported perceptual changes in psychosis, no definitive conclusions have been drawn about visual disturbances that are related to bipolar disorder (BPD). The purpose of the present study was to evaluate colour vision in BPD patients. Data were recorded from 24 participants: healthy control group (n = 12) and type 1 BPD group (n = 12). The participants were 20–45 years old and they were free from neurological disorders and identifiable ocular disease and had normal or corrected-to-normal visual acuity. Colour discrimination was evaluated using the Lanthony D-15d, Trivector and Ellipse tests, using a psychophysical forced-choice method. The relationship of visual measures to mood state and cognitive function was also investigated. The results showed that BPD patients had higher colour discrimination thresholds in the D15d (p < 0.001), Trivector (p < 0.001) and Ellipse (p < 0.01) tests compared with healthy controls. Linear regression analysis showed that mood state was related to colour discrimination. BPD individuals were not impaired in cognitive tasks. The present study provided new evidence of potential links between type 1 BPD and visual processing impairments. This research suggests a new direction for studies and the need for research in this field of study.

Estudos envolvendo portadores de esquizofrenia têm mostrado alterações severas da percepção e cognição. A maioria dos diagnósticos, entretanto, é baseada na avaliação de processos cognitivos. Nossos estudos investigaram a percepção alterada de forma e tamanho em pacientes com esquizofrenia e com depressão maior utilizando 24 pinturas de Salvador Dalí. Conduzimos dois estudos comparando grupos experimental e controle e observamos, em ambos os casos, que os portadores de esquizofrenia perceberam figuras 1,5 e 3,0 vezes maior do que os respectivos grupos controle. Em outro estudo com pacientes com depressão maior não foram observadas alterações na percepção de tamanho comparado ao grupo controle. Concluímos que este efeito de percepção de forma e tamanho alterados pode servir como marcador no diagnóstico precoce da presença de sintomas positivos na esquizofrenia. Sugerimos que estas pinturas de Salvador Dalí sejam utilizadas como ferramenta para avaliar alterações na percepção de formas e tamanhos em pacientes portadores de esquizofrenia e, assim, prevenir o agravamento dos sintomas cognitivos.

The aim of the present study was to measure contrast sensitivity curves for angular frequencies in the range between 2 and 96 cycles/360º in older human adult volunteers and to compare these measurements with the more usual contrast sensitivity functions for sine-wave gratings. All subjects were free of identifiable ocular disease and had normal acuity. We measured the contrast thresholds for young adults (N = 6; age range, 20-26 years) and older adults (N = 6; age range, 60-67 years) using the psychophysical forced-choice method. In this paradigm the volunteers had to choose the stimulus containing a test frequency at low contrast (e.g., either a sine-wave grating or an angular frequency stimulus), or another neutral stimulus at mean luminance (without any contrast). Older adults presented a loss in contrast sensitivity at high and medium angular frequencies compared to the young adults (i.e., from 8 to 96 cycles/360º). Contrary to expectation, contrast sensitivity at low angular frequencies, i.e., 2 and 4 cycles/ 360º, was better for the older group than for the younger group. On the other hand, contrast sensitivity for sine-wave gratings at 3 and 4 cpd was higher for young adults as expected. These results suggest agerelated changes in the contrast sensitivity function for angular frequencies.

The objective of the present study was to determine contrast sensitivity curves of concentric circular patterns with radial frequencies of 0.25, 0.5, 1.0, 2.0, and 4.0 cycles per degree in young and older adult volunteers. These parameters were also compared with sensitivity contrasts for sine-wave gratings. All participants had normal acuity vision and were free of identifiable ocular illness. Contrast sensitivity was measured in 6 young adults aged 19 to 23 years and 6 older adults aged 60 to 69 years using the psychophysical forced-choice method. In this paradigm the volunteers had to decide which of two stimuli contained the above radial frequencies at low contrast levels. The other neutral stimulus was gray with homogeneous luminance. We detected a decline in contrast sensitivity for older adults at all radial frequencies compared to young adults. Also, contrast sensitivity for sine-wave gratings at all measured frequencies was better, as predicted, for all young adults. Maximum sensitivities in the radial frequency contrast sensitivity function and contrast sensitivity function occurred at 0.25 and 0.5 cycles per degree, respectively, for both young and older adults. These results suggest age-related changes in the contrast sensitivity function for concentric symmetrical stimuli.

ResumoO objetivo deste trabalho foi caracterizar e comparar curvas de resposta do sistema visual humano para filtros de freqüências angulares de 1 e 4 ciclos/360º em coordenadas polares. Mensuramos 15 curvas para cada filtro com o paradigma de somação de resposta de supralimiar e com a participação de 5 voluntários adultos. Os resultados demonstraram somações máximas de limiar de contraste na freqüência de teste dos filtros angulares (1 e 4 ciclos/360 o ) circundadas por inibições nas freqüências vizinhas às freqüências de teste de cada filtro. Estes resultados são consistentes com a existência de canais ou filtros angulares de banda estreita operando no sistema visual humano através do processo de somação ou inibição em faixa de freqüências específicas. Palavras-chave: Processamento visual da forma; freqüência angular; filtro de banda-estreita; paradigma de somação de supralimiar. AbstractThe aim of this work was to characterize and to compare the response curves of the human visual system for angular filters of 1 and 4 cycles/ 360 o defined in polar coordinates. We measured 15 curves for each filter with 5 adult volunteers using a supra-threshold summation method with a forced-choice paradigm. The results showed maximum summation effects at test frequencies for angular (1 and 4 cycles/360º) filters surrounded on both sides by strong inhibition. These results were in agreement with the existence of channels or narrow-band angular filters operating in the human visual system either through summation or inhibition of specific frequency ranges.

Changes in visual function beyond high-contrast acuity are known to take place during normal aging. We determined whether sensitivity to linear sine-wave gratings and to an elementary stimulus preferentially processed in extrastriate areas could be distinctively affected by aging. We measured spatial contrast sensitivity twice for concentric polar (Bessel) and vertical linear gratings of 0.6, 2.5, 5, and 20 cycles per degree (cpd) in two age groups (20-30 and 60-70 years). All participants were free of identifiable ocular disease and had normal or corrected-to-normal visual acuity. Participants were more sensitive to Cartesian than to polar gratings in all frequencies tested, and the younger adult group was more sensitive to all stimuli tested. Significant differences between sensitivities of the two groups were found for linear (only 20 cpd; P<0.01) and polar gratings (all frequencies tested; P<0.01). The young adult group was significantly more sensitive to linear than to circular gratings in the 20 cpd frequency. The older adult group was significantly more sensitive to linear than to circular gratings in all spatial frequencies, except in the 20 cpd frequency. The results suggest that sensitivity to the two kinds of stimuli is affected differently by aging. We suggest that neural changes in the aging brain are important determinants of this difference and discuss the results according to current models of human aging.