Conceitos básicos de percepção de cena / Basic concepts of scene perception

A pesquisa sobre percepção de cenas é um esforço da comunidade científica em superar as dificuldades apresentadas ao estudo de estímulos complexos. As consistentes descobertas provaram a viabilidade do tema e encorajam uma abordagem mais holística e integrada nas investigações em percepção visual. Esse esforço e seus achados são, entretanto, pouco conhecidos pelos leitores em língua portuguesa e, até mesmo, entre alguns especialistas que se interessam pelo tema. O objetivo deste trabalho é fazer uma apresentação do campo, esboçar seu desenvolvimento, identificar suas principais questões e demonstrar sua pertinência e importância. Para isso, uma revisão seletiva de textos foi executada entre os autores que construíram os fundamentos da percepção de cenas. Ao concluir a leitura, espera-se que o leitor constate o papel relevante dos processos mnemônicos e do sujeito que observa no processo de captação visual do ambiente natural.

Scene perception research is a scientific community effort to overcome difficulties presented to the study of complex stimuli. Consistent findings support feasibility of the theme and encourage a more holistic and integrated approach to visual perception research. This effort and its findings are, however, poorly known by readers in Portuguese language, even among experts interested in the subject. The purpose of this paper is to introduce this field of research, outline its development, identify its main issues and demonstrate its relevance and importance. This task was accomplished by a selective review of papers from authors who built the foundations of scene perception. Upon completion of the reading, it is expected that the reader understands the relevant role of mnemonic processes and of the observer in the process of visual capture of natural environments.

The objective visual acuity in normal adult C57BL/6J mice:assessment with sweep visually evoked potential / 眼科新进展

Objective To evaluate the reliability of sweep visual evoked potential (SVEP) for assessing the normal objective visual acuity in adult wild-type C57BL/6J mice.Methods A total of 6 wild C57BL/6J mice of either gender at 32-33 days of age were collected.After the mice were anesthetized,the recording electrode (a 2-mm diameter tungsten electrode) was placed at 3 mm lateral to lambda over the left cortex (contralateral to the stimulated right eyes) and advanced to 400 μm within the cortex,and the needle electrodes which placed in the forehead and tail served as the reference and the ground,accordingly.Left eyes (unstimulated eyes) were covered during the recording.The screen (mean luminance 25 cd · m-2) was placed 20 cm in front of the mice,thereby covering 100° (horizontal) × 82° (vertical) of the visual field.The mice were stimulated by vertically sinusoidal grating,which consisted of 11 spatial frequencies,stimulus contrast was 100％,and time frequency was 1 Hz;the entire sweep took 12 seconds (11 spatial frequencies + 1s pre-adaptation),and the values were averaged until the error bars for the data were stable.The VEP waveforms of visual cortex corresponding to the left and right eyes were recorded separately.At least 3-4 trials consisting of 20 events for different frequencies were averaged.Left and right eye were tested alternately.Then the coordinate system was established by using the spatial frequency logarithm as x-axis and the amplitude of the response obtained by the discrete Fourier analysis as y-axis,the objective visual acuity was obtained by extrapolation to zero amplitude of the linear regression through the 4 effective data points adjacent to noise.Results SVEP showed that the amplitude of N100 wave was maximal at a spatial frequency of 0.05 c · deg-1.With the increase of the stimulus spatial frequency progressively,SVEP decreased in amplitude and increased in latency.The cortical electrical signal could not be distinguished from noise at a spatial frequency of 0.65 c · deg-1.The average acuity of 6 mice was (0.56 ± 0.04) c · deg-1 for right eyes and (0.50 ± 0.04)c · deg-1 for left eyes respectively.There was no significant difference between the two eyes(P＞0.05);The visual evoked potential acuity of 12 eyes was (0.53 ±0.03)c ·deg-1.Conclusion SVEP could be used to estimate the mouse VEP acuity,which was closed to the behavioral visual acuity.However,the VEP acuity was more objective and accurate as well as time-saving.

Development of Korean Social Affective Visual Stimuli / 수면정신생리

OBJECTIVES: The current study aims to develop Korean Social Affective Visual Stimuli (K-SAVS) to arouse social affect. METHODS: K-SAVS is composed of pictures of social situations among East Asians. Each picture contains a negative, positive, or neutral affect. Positive and negative stimuli were presented to one group of subjects. Negative and neutral stimuli were presented to another group of subjects. All subjects were required to fill out Affective Valence and Arousal Manikin. RESULTS: In the initial test, 18 positive affective stimuli pictures (1 set) and 36 negative affective stimuli pictures (2 sets) were chosen from 95 stimuli pictures. Positive affective stimuli pictures showed higher valence (p < 0.001) and lower arousal (p < 0.001) than negative affective stimuli pictures. In the confirmatory test, 18 neutral stimuli pictures (1 set) were additionally selected out of the total of 79 pictures of neutral stimuli pictures and the pictures used in the former experiment. Neutral stimuli pictures showed higher valence (p < 0.001) and lower arousal (p < 0.001) than negative affective stimuli pictures. CONCLUSION: K-SAVS can be a valid and useful tool for inducing specific social affects of Koreans.

Time-varying source analysis of auditory-visual stimuli evoked event-related potentials / 国际生物医学工程杂志

Objective Dipole source analysis was employed to investigate the transient changes in brain mechanisms at earlier latencies.Methods Fourteen healthy volunteers were recruited in this research and evoked event-related potentials (ERPs) of unimodal and bimodal visual auditory stimuli were recorded by 64-electrodes electroencephalograph (EEG) recording system.All these earlier phases of the stimuli were divided into several subphases by specific time window for source analysis.Results The results showed that ERPs sources were mainly generated from visual and audio cortex,and there were changes in the location and strength of the dipole sources in each sub-phase.Conclusions The result of this study implies a serial processing of sensory information in human cortices in early phase of visual and auditory stimuli.

Development of the Alcohol-Related Visual Stimuli Inducing Alcohol Craving / 신경정신의학

OBJECTIVES: Craving is the subjectively experienced motivational states inducing ongoing drug use in addicts. It also proceeds or precipitates relapse episode in drug addicts. Alcohol craving may be triggered by exposure to an object, environment, or emotion that a person has come to associate with alcohol consumption. Such stimuli are called alcohol-related cues. Among alcohol-related cues, alcohol-related visual stimuli are simple and reliable methods in inducing alcohol craving. The object of this study is to develop alcohol-related visual stimuli which induce alcohol craving reliably and to investigate the characteristics of alcohol-related visual stimuli in alcoholics. METHODS: First, the authors developed 27 alcohol and drinking color photos as candidate stimuli. Then, 3 photos which induce alcohol craving most were chosen as alcohol-related visual stimuli respectively by alcoholics, alcoholism high risk group and normal control group. The authors compared characteristics, situation and complexity of selected alcohol-related visual stimuli among three groups. RESULTS: 1) 'A glass of Soju', 'Drinking together' and 'A glass of beer, a bottle of beer and a sidedish' were chosen as alcohol-related visual stimuli which induce most craving in alcoholics, alcoholism high risk group and normal control group respectively. 2) Alcohol photo(stationary object) induced craving most in alcoholics in contrast with drinking photo(situation) in social drinkers. Alcoholics clung to alcohol per se, not to atmosphere or situation of drinking, and alcoholism high risk group felt craving by the expectation of drinking situation. Normal control group showed no consistent finding in choosing alcohol-related visual stimuli. CONCLUSION: With these results, the author suggests classical conditioning as psychopathological model of alcohol craving with alcoholics. In contrast with alcoholics, alcohol craving of alcoholism high risk group may be related to alcohol specific memory or positive expectancies about alcohol use. These finding may support different neurobiological mechanisms of alcohol craving between alcoholics and social drinkers.

Effects of Number and Method of Visual Stimuli on Simple Reaction Time / 대한산업의학회지

In. order to evaluate the effects of number and method of visual stimuli on simple reaction time and determine the proper number of trials, simple reaction time of the computerized test of NTOS (Neurobehavioral Test for Occupational Screening) was carried out on 240 medical students. The prominent difference was found between male and female on simple reaction time. Regarding the effect of number based on the parameters of measures and the purpose of test itself, 64 trials was considered as proper number. The mean reaction time was different according to the methods of visual stimuli, such as color and size(p<0.05). The larger and more intence visual stimuli were, the faster sim-ple reaction time was. In respect to sex, that difference was similar. But, there was no difference depending upon whether the each result of each trial was showed on the monitor. The subjects, however, showed much interest when the result showed. Further studies, including the various variables on visual stimuli, are required to compare among various studies.