The applicability of web-based solutions in headache epidemiology research.

BACKGROUND: Epidemiological research of headache is vital but resource consuming prerequisite for evidence-based development in the field. Rapid evolution of information technology may provide new opportunities for population-based surveys. The aim of this study was to evaluate the applicability of web-based solutions in epidemiological studies of primary headaches. METHODS: An online survey was conducted among 20-64 year old Estonian citizens, using a previously validated headache questionnaire. The participants were accessed through most popular portals and e-mail domains to get the maximum coverage of Estonian digital community. The resulting one-year headache prevalences were compared to those acquired in parallel from a population-based cross-sectional person-to-person study in Estonia. RESULTS: Five thousand seven hundred eight entries were made by 5347 participants in the online study. Of the participants, 3896 (72.9%) had no headache, 1436 (26.8%) had only one and 15 (0.3%) had more than one type of headache. The study sample demographics were statistically significantly different from Estonian population and the prevalences were adjusted by age, gender, education and habitat. The proportion of headache sufferers was smaller in the online study sample (23.1% vs 41.0% in the population-based parallel person-to-person study). Among the headache sufferers the proportions of different headache diagnoses were similar across the two studies with the exceptions of episodic migraine and episodic tension-type headache. There were less migraine and more tension-type headache sufferers in the online study sample. DISCUSSION: This is the first study addressing applicability of web-based solutions in headache related large epidemiological studies. Online approach presents a much faster means of data collection, larger samples, has mechanisms of avoiding data contamination and distinguishes the proportions of most primary headache disorders among the headache sufferers. However, the present online survey was significantly biased towards the people without headache, leading to underestimation of headache prevalence. This stems from the shortcomings related to method of sampling, access and engagement. CONCLUSION: Online headache epidemiology research could be a resource saving alternative to person-to-person studies, however, further research is needed to overcome the problems related to methods of sampling, access and engagement.

The prevalence of primary headache disorders in the adult population of Estonia.

OBJECTIVE: To estimate the one-year prevalence of primary headaches, most importantly migraine and tension type headache, but also other primary headaches, in Estonia. METHODS: A population-based random sample of 2162 subjects in Tartu City and Tartu County were interviewed by telephone or face to face using a previously validated questionnaire. RESULTS: Of the 2162 contacted participants, 1215 (56%) fully completed the study. Of these, 502 (41.3%) reported headache during the previous year. The prevalences adjusted by weighting by age, gender, education, marital status and habitat were the following: All headaches 41.0%, all migraine 17.7%, all tension-type headache 18.0%, trigeminal autonomic cephalalgias 0.4%, other primary headaches 2.5%, and chronic headaches 2.7%. CONCLUSION: The 1-year prevalences of primary headache disorders in Estonia are comparable to the previous findings in other European countries.

Suicidal Behavior Among People Living with HIV (PLHIV) in Medical Care in Estonia and Factors Associated with Receiving Psychological Treatment.

People living with HIV (PLHIV) have higher rates of suicidal behavior than the general population. This study assessed suicidal behavior (ideation and/or attempts, ever and in the past 12 months) among PLHIV receiving outpatient HIV medical care in Estonia and associations between suicidal behavior and psychological treatment. The cross-sectional study collected data from January to November 2013 using a self-report questionnaire. Eight hundred PLHIV participated, 39 % (n = 306) of whom had been suicidal. Lifetime prevalence was 36 % for suicidal ideation and 20 % for attempts. Younger age, incarceration, having ever abused alcohol and also injected drugs, having lived with HIV for more than 10 years, and being depressed were associated with lifetime suicidal behavior. Suicidal behavior within the past 12 months was reported by 20 % (n = 156) of respondents. Of these, 27 % received psychological treatment (counseling and/or psychotherapy), 20 % had taken antidepressants, and 49 % sedatives. Individuals perceiving a need for treatment were significantly more likely to receive psychological treatment when experiencing suicidal behavior (OR 25.65, 95 % CI 2.92-225.47). In conclusion, suicidal behavior is frequent among PLHIV but psychological treatment is not often received. One of the barriers to treatment is patients' lack of perceived need for help.

How much time does it take to discriminate two sets by their numbers of elements?

The ability to evaluate the number of elements in a set-numerosity-without symbolic representation is a form of primitive perceptual intelligence. A simple binomial model was proposed to explain how observers discriminate the numerical proportion between two sets of elements distinct in color or orientation (Raidvee et al., 2017, Attention Perception & Psychophysics, 79[1], 267-282). The binomial model's only parameter ß is the probability with which each visual element can be noticed and registered by the perceptual system. Here we analyzed the response times (RT) which were ignored in the previous report since there were no instructions concerning response speed. The relationship between the mean RT and the absolute difference |ΔN| between numbers of elements in two sets was described by a linear regression, the slope of which became flatter as the total number of elements N increased. Because the coefficients of regression between the mean RT and |ΔN| were more directly related to the binomial probability ß rather than to the standard deviation of the best fitting cumulative normal distribution, it was regarded as evidence that the binomial model with a single parameter - probability ß - is a viable alternative to the customary Thurstonian-Gaussian model.

How are local orientation signals pooled?

Visual perception is capable of pooling multiple local orientation signals into a single more accurate summary orientation. However, there is still a lack of systematic inquiry into which summary statistics are implemented in that process. Here, the task was to recognize in which direction, clockwise or counter-clockwise, the mean orientation of a set of randomly distributed Gabor patches (N = 1, 2, 4, and 8) was rotated from the implicit vertical. The mean orientation discrimination accuracy did not improve with the increase of the number N of elements in proportion to the square-root-N, as could be expected if noisy internal representations were arithmetically averaged. The Proportion of Informative Elements (PIE), defined as the percentage of elements having an orientation different from the vertical, also affected the discrimination precision, violating the arithmetic averaging rules. The decrease in the orientation discrimination precision with the increase of the PIE would suggest that the orientation pooling could be more adequately described by a quadratic or higher power mean. Thus, we parameterized the averaging process for the power parameter of the generalized mean formula. The results indicate that different pooling rules in different trials may apply, for example, the arithmetic mean in some and the maximal deviation rule in others. It is concluded that pooling of orientation information is a relatively inaccurate process for which different perceptual cues and their combination rules can be used.

Proximity model of perceived numerosity.

The occupancy model (OM) was proposed to explain how the spatial arrangement of dots in sparse random patterns affects their perceived numerosity. The model's central thesis maintained that each dot seemingly fills or occupies its surrounding area within a fixed radius ro and the total area collectively occupied by all the dots determines their apparent number. Because the perceptual system is not adapted for the precise estimation of area, it looks likely that the OM is just a convenient computational algorithm that does not necessarily correspond to the processes that actually take place in the perceptual system. As an alternative, the proximity model (PM) was proposed, which instead relies on a binomial function with the probability ß characterizing the perceptual salience with which each element can be registered by the perceptual system. It was also assumed that the magnitude of ß is proportional to the distance between a dot and its nearest neighbor. A simulation experiment demonstrated that the occupancy area computed according to the OM can almost perfectly be replicated by the mean nearest neighbor distance. It was concluded that proximity between elements is a critical factor in determining their perceived numerosity, but the exact algorithm that is used for the measure of proximities is yet to be established.

A method for detection of inattentional feature blindness.

In ensemble displays, two principal factors determine the precision with which the mean value of some perceptual attribute, such as size and orientation, can be discriminated: inefficiency and representational noise of each element. Inefficiency is mainly caused by biased inference, or by inattentional (feature) blindness (i.e., some elements or their features are not processed). Here, we define inattentional feature blindness as an inability to perceive the value(s) of certain feature(s) of an object while the presence of the object itself may be registered. Separation of the effects of inattentional (feature) blindness and perceptual noise has escaped traditional analytic methods because of their trade-off effects on the slope of the psychometric discrimination function. Here, we propose a method that can separate the effects of inattentional feature blindness from that of the representational noise. The basic idea is to display a set of elements from which only one contains information relevant for solving the task, while all other elements are "dummies" carrying no useful information because they do not differ from the reference. If the single informative element goes unprocessed, the correct answer can only be given by a random guess. The guess rate can be modeled similarly to the lapse rate, traditionally represented by λ. As an illustration, we present evidence that the presence versus lack of inattentional feature blindness in orientation pooling depends on the feature types present in the display.

Perception of means, sums, and areas.

In this age of data visualization, it is important to understand our perception of the symbols that are used. For example, does the perceived size of a disc correspond most closely to its area, diameter, circumference, or some other measure? When multiple items are present, this becomes a question of ensemble perception. Here, we compare observers' performance across three different tasks: judgments of (i) the mean diameter, (ii) the total diameter, or (iii) the total area of (N = 1, 2, 3, or 7) test circles compared with a single reference circle. We draw a parallel between Anne Treisman's feature integration theory and Daniel Kahneman's cognitive systems, comparing the preattentive stage to System 1, and the focused attention stage to System 2. In accordance with Kahneman's prediction, average size (diameter) of the geometric figures can be judged with considerable accuracy, but the total diameter of the same figures cannot. Like the total length, the cumulative area covered by circles was also judged considerably less accurately than the mean diameter. Differences in efficiency between these three tasks illustrate powerful constraints upon visual processing: The visual system is well adapted for the perception of the mean size while there are no analogous mechanisms for the accurate perception of the total length or cumulative area. Thus, in visualizing data, using bubble charts proportional to area may be misleading as our visual system seems better adapted to perceive disc size by the radius rather than the area.

Discrimination of numerical proportions: A comparison of binomial and Gaussian models.

Observers discriminated the numerical proportion of two sets of elements (N = 9, 13, 33, and 65) that differed either by color or orientation. According to the standard Thurstonian approach, the accuracy of proportion discrimination is determined by irreducible noise in the nervous system that stochastically transforms the number of presented visual elements onto a continuum of psychological states representing numerosity. As an alternative to this customary approach, we propose a Thurstonian-binomial model, which assumes discrete perceptual states, each of which is associated with a certain visual element. It is shown that the probability ß with which each visual element can be noticed and registered by the perceptual system can explain data of numerical proportion discrimination at least as well as the continuous Thurstonian-Gaussian model, and better, if the greater parsimony of the Thurstonian-binomial model is taken into account using AIC model selection. We conclude that Gaussian and binomial models represent two different fundamental principles-internal noise vs. using only a fraction of available information-which are both plausible descriptions of visual perception.

3D Cinema and Headache: The First Evidential Relation and Analysis of Involved Factors.

BACKGROUND: A possible link between 3D movies and headache (HA) has never been a target of specific and systematic investigations. The aim of this study was to investigate the relationship between 3D cinema and HA and to evaluate possible risk factors of developing HA during or after watching a 3D movie. METHODS: This was a prospective, non-randomized, observational study. Six thousand specifically designed questionnaires were distributed to consecutive cinema visitors. Relative HA risks for 2D- vs. 3D-movie visitors and the effects of background variables were analyzed. RESULTS: The questionnaire was filled and returned by 1293 persons. The mean age of responders was 33.0 ± 11.3 years. Individuals who viewed 3D movies reported HA during or after the movie 1.61 times more often than 2D-movie viewers (11.1% in 3D vs. 7.2% in 2D movies, p = 0.017). The risk was higher in women: 2.65 times for 2D (p = 0.019) and 1.85 times for 3D movies (p = 0.06), and decreased with age by 4.6% with each year for 2D (p = 0.0035) and by 3.2% for 3D movies (p = 0.0098). Among 3D-movie visitors, those with previous HAs were 4.17 times more prone to get a cinema-induced HA (p = 0.02). The risk was the highest for persons with migraine (OR = 3.37, p = 0.001). CONCLUSION: For the first time, it was evidentially shown that 3D movies can provoke HA. Persons at risk are mostly younger women and/or migraineurs. Based on our results, for those belonging to the aforementioned risk groups, it can be mainly recommended to choose passive 3D technology and to view movies from the farthest possible distance.

Obligatory averaging in mean size perception.

The perception of ensemble characteristics is often regarded as an antidote to an established bottleneck in focused attention and working memory, both of which appear to be limited in capacity to a few objects only. In order to test the associative law of summation, observers were asked to estimate the mean size of four circles relative to a reference circle. When there was no time to scrutinize each individual circle, observers discriminated the mean size difference identically, irrespective of whether the same summary size increment or decrement was added to or subtracted from the size of only one, two, or all four circles. Since observers judged the size of individual circles, the position of which was indicated after they were displayed, considerably less accurately than the mean size of the four circles, it is very unlikely that explicit knowledge of the size of the individual elements is the basis of mean size judgments. The sizes of individual elements were pooled together in an obligatory manner before size information had reached awareness. The processing of size information seems to be largely constrained to only one measure at a time, with a preference for mean size rather than the individual measures from which it is assembled.

Visual evoked potentials to change in coloration of a moving bar.

In our previous study we found that it takes less time to detect coloration change in a moving object compared to coloration change in a stationary one (Kreegipuu etal., 2006). Here, we replicated the experiment, but in addition to reaction times (RTs) we measured visual evoked potentials (VEPs), to see whether this effect of motion is revealed at the cortical level of information processing. We asked our subjects to detect changes in coloration of stationary (0(°)/s) and moving bars (4.4 and 17.6(°)/s). Psychophysical results replicate the findings from the previous study showing decreased RTs to coloration changes with increase of velocity of the color changing stimulus. The effect of velocity on VEPs was opposite to the one found on RTs. Except for component N1, the amplitudes of VEPs elicited by the coloration change of faster moving objects were reduced than those elicited by the coloration change of slower moving or stationary objects. The only significant effect of velocity on latency of peaks was found for P2 in frontal region. The results are discussed in the light of change-to-change interval and the two methods reflecting different processing mechanisms.

An almost general theory of mean size perception.

A general explanation for the observer's ability to judge the mean size of simple geometrical figures, such as circles, was advanced. Results indicated that, contrary to what would be predicted by statistical averaging, the precision of mean size perception decreases with the number of judged elements. Since mean size discrimination was insensitive to how total size differences were distributed among individual elements, this suggests that the observer has a limited cognitive access to the size of individual elements pooled together in a compulsory manner before size information reaches awareness. Confirming the associative law of addition means, observers are indeed sensitive to the mean, not the sizes of individual elements. All existing data can be explained by an almost general theory, namely, the Noise and Selection (N&S) Theory, formulated in exact quantitative terms, implementing two familiar psychophysical principles: the size of an element cannot be measured with absolute accuracy and only a limited number of elements can be taken into account in the computation of the average size. It was concluded that the computation of ensemble characteristics is not necessarily a tool for surpassing the capacity limitations of perceptual processing.

Unattended and attended visual change detection of motion as indexed by event-related potentials and its behavioral correlates.

Visual mismatch negativity (vMMN) is a negative-going component amongst cognitive event-related potentials. It reflects an automatic change-detection process that occurs when an infrequent stimulus is presented that is incongruent with the representation of a frequent (standard) event. In our research we use visual motion (more specifically motion direction changes) to study vMMN. Since movement in the visual field is quite irresistible to our brain, the question in hand is, if the detection of motion direction changes is dependent on attention directed to the stimulus. We present a new continuous whole-display stimulus configuration, where the attention capturing primary task of motion onset detection is in the central part of the visual display and visual oddball sequence on the background. The visual oddball paradigm consisted of 85% standard and 15% deviant events, motion direction change being the deviant. We show that even though the unattended visual oddball sequence does not affect the performance in the demanding behavioral primary task, the differences appearing in that sequence are noticed by our brain and reflected in two distinguishable vMMN components in occipital and parietal scalp locations. When attention is directed toward the visual oddball sequence, we only see different processing of standards and deviants in later time-windows and task-related activity in frontal scalp location. Our results are obtained under strict attention manipulation conditions.

Unintentionality of affective attention across visual processing stages.

Affective attention involves bottom-up perceptual selection that prioritizes motivationally significant stimuli. To clarify the extent to which this process is automatic, we investigated the dependence of affective attention on the intention to process emotional meaning. Affective attention was manipulated by presenting affective images with variable arousal and intentionality by requiring participants to make affective and non-affective evaluations. Polytomous rather than binary decisions were required from the participants in order to elicit relatively deep emotional processing. The temporal dynamics of prioritized processing were assessed using early posterior negativity (EPN, 175-300 ms) as well as P3-like (P3, 300-500 ms) and slow wave (SW, 500-1500 ms) portions of the late positive potential. All analyzed components were differentially sensitive to stimulus categories suggesting that they indeed reflect distinct stages of motivational significance encoding. The intention to perceive emotional meaning had no effect on EPN, an additive effect on P3, and an interactive effect on SW. We concluded that affective attention went from completely unintentional during the EPN to partially unintentional during P3 and SW where top-down signals, respectively, complemented and modulated bottom-up differences in stimulus prioritization. The findings were interpreted in light of two-stage models of visual perception by associating the EPN with large-capacity initial relevance detection and the P3 as well as SW with capacity-limited consolidation and elaboration of affective stimuli.

A new approach for assessment of mental architecture: repeated tagging.

A new approach to the study of a relatively neglected property of mental architecture-whether and when the already-processed elements are separated from the to-be-processed elements-is proposed. The process of numerical proportion discrimination between two sets of elements defined either by color or by orientation can be described as sampling with or without replacement (characterized by binomial or hypergeometric probability distributions respectively) depending on the possibility to tag an element once or repeatedly. All empirical psychometric functions were approximated by a theoretical model showing that the ability to keep track of the already tagged elements is not an inflexible part of the mental architecture but rather an individually variable strategy which also depends on conspicuity of perceptual attributes. Strong evidence is provided that in a considerable number of trials, observers tagged the same element repeatedly which can only be done serially at two separate time moments.

Visibility versus accountability in pooling local motion signals into global motion direction.

The human observer is surprisingly inaccurate in discriminating proportions between two spatially overlapping sets of randomly distributed elements moving in opposite directions. It was shown that observers took into account an equivalent of 74 % of all moving elements when the task was to estimate their relative number, but only an equivalent of 21 % of the same elements when the task was to discriminate between opposite directions. It was concluded that, in the motion direction discrimination task, a large proportion of the signal from all of the elements was inaccessible to the observers, whereas the majority of the signal was accessible in a numerosity task. This type of perceptual limitation belongs to the attentional blindness category, where a strong sensory signal cannot be noticed when processing is diverted by parallel events. In addition, we found no evidence for the common-fate principle, as the ability to discriminate numerical proportions remained the same, irrespective of whether all estimated elements were moving coherently in one direction or unpredictably in opposite directions.

Pooling elementary motion signals into perception of global motion direction.

Six observers were asked to indicate in which of two opposite directions, to the right or to the left, an entire display appeared to move, based on the proportion of right vs leftward motion elements, each of which was distinctly visible. The performance of each observer was described by Thurstone's discriminative processes and Bernoulli trial models which described empirical psychometric functions equally well. Although formally it was impossible to discriminate between these two models, treating observer as a counting device which measures a randomly selected subsample of all available motion elements had certain advantages. According to the Bernoulli trial model decisions about the global motion direction in a range of 12-800 elements were based on taking into account about 4±2 random moving dot elements. This small number is not due to cancellation of the opposite motion vectors since the motion direction recognition performance did not improve after the compared motion directions were made orthogonal. This may indicate that the motion pooling mechanism studied in our experiment is strongly limited in capacity.

Reaction time to motion onset and magnitude estimation of velocity in the presence of background motion.

Reaction times (RT) to motion onset of a target grating moving at 0.4, 0.6, 0.8, 1.0 or 1.6 °/s and magnitude estimation of the same velocities were studied in the presence of the surrounding background motion which was either in the same or opposite direction. Surprisingly, we found no relative motion effect: if the background motion, irrespective of its direction, affected the target, then it delayed the RTs and decreased velocity ratings. The background motion was effective on RTs to motion onset only when the target was relatively small and immediately surrounded by a moving background. Increases in RTs were mostly explained by an apparent slowdown of the target stimulus velocity which was caused by the interference from the moving background. The background motion also affected velocity ratings by decreasing them without systematic effect of the background motion direction.