Preattentive information processing in schizophrenia

The Evolution of Psychological and Behavioral Consequences of Self-Isolation During Lockdown: A Longitudinal Study Across United Kingdom and Italy

Introduction

Several countries imposed nationwide or partial lockdowns to limit the spread of COVID-19 and avoid overwhelming hospitals and intensive care units. Lockdown may involve restriction of movement, stay-at-home orders and self-isolation, which may have dramatic consequences on mental health. Recent studies demonstrated that the negative impact of lockdown restrictions depends on a wide range of psychological and socio-demographic factors.

Aims

This longitudinal study aimed to understand how internal factors such as personality and mindfulness traits, and external factors, such as daily habits and house features, affect anxiety, depression and general wellbeing indicators, as well as cognitive functions, during the course of a lockdown.

Methods

To address these questions, 96 participants in Italy and the United Kingdom filled out a survey, once a week for 4 weeks, during the first-wave lockdowns. The survey included questions related to their habits and features of the house, as well as validated questionnaires to measure personality traits, mindful attitude and post-traumatic symptoms. Indicators of wellbeing were the affective state, anxiety, stress and psychopathological indices. We also measured the emotional impact of the pandemic on cognitive ability by using two online behavioral tasks [emotional Stroop task (EST) and visual search].

Results

We found that internal factors influenced participants' wellbeing during the first week of the study, while external factors affected participants in the last weeks. In the first week, internal variables such as openness, conscientiousness and being non-judgmental toward one's own thoughts and emotions were positively associated with wellbeing; instead, neuroticism and the tendency to observe and describe one's own thoughts and emotions had detrimental effects on wellbeing. Toward the end of the study, external variables such as watching television and movies, browsing the internet, walking the dog, and having a balcony showed a protective value, while social networking and engaging in video calls predicted lower values of wellbeing. We did not find any effects of wellbeing on cognitive functioning.

Conclusion

Recognizing specific traits and habits affecting individuals' wellbeing (in both short and long terms) during social isolation is crucial to identify people at risk of developing psychological distress and help refine current guidelines to alleviate the psychological consequences of prolonged lockdowns.

Attentional guidance during visual search among patients with schizophrenia

The current study investigated visual guidance and saccadic selectivity during visual search among patients with schizophrenia (SCZ). Data from a previous study (Elahipanah, A., Christensen, B.K., & Reingold, E.M., 2008. Visual selective attention among persons with schizophrenia: The distractor ratio effect. Schizophr. Res. 105, 61-67.) suggested that visual guidance for the less frequent distractors in a conjunction search display (i.e., the distractor ratio effect) is intact among SCZ patients. The current study investigated the distractor ratio effect among SCZ patients when: 1) search is more demanding, and 2) search involves motion perception. In addition, eye tracking was employed to directly study saccadic selectivity for the different types of distractors. Twenty-eight SCZ patients receiving a single antipsychotic medication and 26 healthy control participants performed two conjunction search tasks: a within-dimension (i.e., colour × colour) search task; and a cross-dimension (i.e., motion × colour) search task. In each task the relative frequency of distractors was manipulated across 5 levels. Despite slower search times, patients' eye movement data indicated unimpaired visual guidance in both tasks. However, in the motion × colour conjunction search task, patients displayed disproportionate difficulty detecting the moving target when the majority of distractors were also moving. Results demonstrate that bottom-up attentional guidance is unimpaired among patients with SCZ; however, patients' impairment in motion discrimination impedes their ability to detect a moving target against noisy backgrounds.

Controlling the spotlight of attention: visual span size and flexibility in schizophrenia

The current study investigated the size and flexible control of visual span among patients with schizophrenia during visual search performance. Visual span is the region of the visual field from which one extracts information during a single eye fixation, and a larger visual span size is linked to more efficient search performance. Therefore, a reduced visual span may explain patients' impaired performance on search tasks. The gaze-contingent moving window paradigm was used to estimate the visual span size of patients and healthy participants while they performed two different search tasks. In addition, changes in visual span size were measured as a function of two manipulations of task difficulty: target-distractor similarity and stimulus familiarity. Patients with schizophrenia searched more slowly across both tasks and conditions. Patients also demonstrated smaller visual span sizes on the easier search condition in each task. Moreover, healthy controls' visual span size increased as target discriminability or distractor familiarity increased. This modulation of visual span size, however, was reduced or not observed among patients. The implications of the present findings, with regard to previously reported visual search deficits, and other functional and structural abnormalities associated with schizophrenia, are discussed.

What can eye movements tell us about Symbol Digit substitution by patients with schizophrenia?

Substitution tests are sensitive to cognitive impairment and reliably discriminate patients with schizophrenia from healthy individuals better than most other neuropsychological instruments. However, due to their multifaceted nature, substitution test scores cannot pinpoint the specific cognitive deficits that lead to poor performance. The current study investigated eye movements during performance on a substitution test in order to better understand what aspect of substitution test performance underlies schizophrenia-related impairment. Twenty-five patients with schizophrenia and 25 healthy individuals performed a computerized version of the Symbol Digit Modalities Test while their eye movements were monitored. As expected, patients achieved lower overall performance scores. Moreover, analysis of participants' eye movements revealed that patients spent more time searching for the target symbol every time they visited the key area. Patients also made more visits to the key area for each response that they made. Regression analysis suggested that patients' impaired performance on substitution tasks is primarily related to a less efficient visual search and, secondarily, to impaired memory.

Impaired top-down control of visual search in schizophrenia

This study examined top-down and bottom-up control of attention in a group of 24 patients with schizophrenia and 16 healthy volunteers. Participants completed a visual search task in which they reported whether a target oval contained a gap. The target was accompanied by 5, 11, or 17 distractors. On some trials, the target was identified by a highly salient feature that was shared by only 2 distractors, causing this feature to "pop out" from the display. This feature provided strong bottom-up information that could be used to direct attention to the target. On other trials, half of the distractors contained this feature making these distractors no more salient than the other distractors requiring greater use of top-down control to restrict processing to items containing this feature. Patient visual search efficiency closely approximated control performance in the first trial type. In contrast, patients demonstrated significant slowing of search in the second trial type, which required top-down control. These results suggest that schizophrenia does not impair the ability to implement the selection of a target when attention can be guided by bottom-up information, but it does impair the ability to use top-down control mechanisms to guide attention. These results extend prior studies that have focused on aspects of executive control in complex tasks and suggest that a similar underlying deficit may also impact the performance of perceptual systems.

Clear distinction between preattentive and attentive process in schizophrenia by visual search performance

Visual information-processing deficits were investigated in patients with schizophrenia using visual search tasks. Subjects comprised 20 patients with schizophrenia and 20 normal subjects. Visual search tasks were modified from those used previously to reveal more distinct differences between feature and conjunction search tasks. The presentation area of items in the present study was more than double the area used in our previous study [Mori, S., Tanaka, G., Ayaka, Y., Michitsuji, S., Niwa, H., Uemura, M., Ohta, Y., 1996. Preattentive and focal attentional processes in schizophrenia: a visual search study. Schizophrenia Research 22, 69-76], and items were distributed over the area randomly in each trial to produce a certain range of locational jitter for each item across trials that prevented a matrix-like presentation of items at fixed positions [Mori, S., Tanaka, G., Ayaka, Y., Michitsuji, S., Niwa, H., Uemura, M., Ohta, Y., 1996. Preattentive and focal attentional processes in schizophrenia: a visual search study. Schizophrenia Research 22, 69-76]. The target was a red square, and distractors were red circles in the feature search task and red circles and green squares in the conjunction search task. Slopes and intercepts of a linear function relating reaction times to set size were computed. In the feature search task, slopes for both groups were almost zero. In the conjunction search task, significant differences in slopes were seen between the two groups irrespective of target presence or absence. Moreover, the slopes were approximately twice as steep during target absence as during target presence. These results indicate more definitively than the results of our previous study [Mori, S., Tanaka, G., Ayaka, Y., Michitsuji, S., Niwa, H., Uemura, M., Ohta, Y., 1996. Preattentive and focal attentional processes in schizophrenia: a visual search study. Schizophrenia Research 22, 69-76] that patients with schizophrenia have deficits in focal attentional processing, although their preattentive processing functions at a normal level.

A role for the 'magnocellular advantage' in visual impairments in neurodevelopmental and psychiatric disorders

Evidence exists implicating abnormal visual information processing and visually driven attention in a number of neurodevelopmental and psychiatric disorders, suggesting that research into such disorders may benefit from a better understanding of more recent advances in visual system processing. A new integrated model of visual processing based on primate single cell and human electrophysiology may provide a framework, to understand how the visual system is involved, by implicating the magnocellular pathway's role in driving attentional mechanisms in higher-order cortical regions, what we term the 'magnocellular advantage'. Evidence is also presented demonstrating visual processing occurs considerably faster than previously assumed, and emphasising the importance of top-down feedback signals into primary visual cortex, as well as considering the possibility of lateral connections from dorsal to ventral visual areas. Such organisation is argued to be important for future research highlighting visual aspects of impairment in disorders as diverse as schizophrenia and autism.

Perceptual Organization in Schizophrenia Spectrum Disorders: Empirical Research and Theoretical Implications

The research into perceptual organization in schizophrenia spectrum disorders has found evidence for and against a perceptual organization deficit and has interpreted the data from within several different theoretical frameworks. A synthesis of this evidence, however, reveals that this body of work has produced reliable evidence for deficits in schizophrenia, as well as for the clinical, stimulus, and task parameters associated with normal and abnormal performance. Recent models of cognition have also advanced understanding of the underlying pathophysiological processes of perceptual organization dysfunction in schizophrenia spectrum disorders. These suggest that deficits in perceptual organization may be one manifestation of a wider disturbance in the integration of contextually related information across space and time.

Auditory temporal processing in schizophrenia: high level rather than low level deficits?

INTRODUCTION

Patients with schizophrenia demonstrate a wide range of information processing deficits. Most recent studies argue in favour of high level deficits, including attention and context processing, whereas fewer studies have demonstrated deficits at earlier stages of processing, such as perceptual discrimination and organisation. This is the first study to investigate both high and low level processing, within a single paradigm, in the case of auditory temporal processing in schizophrenia.

METHODS

Patients with schizophrenia were compared to controls on a series of tasks involving three auditory temporal processes varying from low to higher level: (1) segregation of a complex sequence into component auditory streams; (2) detection of local temporal irregularities within a stream; (3) attentional focusing on one stream by the use of a cue preceding the complex sequence.

RESULTS

The lowest level of processing examined here--stream segregation--appeared to function equally well in patients as in controls. However, the higher level processes--irregularity detection and attentional focus--functioned in both groups, but less efficiently in patients with schizophrenia.

CONCLUSIONS

Results demonstrate abnormal auditory temporal processing in schizophrenia. Abnormal performances only in Processes 2 and 3 support and hypothesis of higher level rather than lower level processing deficits in schizophrenia.

Pre-attentive cognitive processing in epilepsy. A pilot study on the impact of epilepsy type and anti-epileptic treatment

Patients suffering from epilepsy often complain of deficits in attentive cognition affecting, for instance, concentration, reaction time, memory and psychomotor speed. We were interested in the impact of epilepsy and its treatment on pre-attentive cognitive functions and enrolled 107 subjects (50 male, 57 female; mean age 26 years): 50 patients with partial epilepsy, 15 with primary generalised epilepsy and 42 healthy controls. We used a new computer-adapted neuropsychological test (called textest), measuring the pre-attentive visual processing speed. The subjects had to discriminate 5 different stimuli presented on a computer screen. As a primary result, we calculated the time the subject needed to detect 50% of the demonstrated stimuli correctly (t-50 time). We also applied the d2 test. For the textest results, no significant group differences between the different patient and healthy groups could be revealed, except for a significantly increased t-50 time in patients with polytherapy compared with the control group. Compared with healthy controls, significantly worse d2 test results were found in patients with epilepsy in general, a duration of disease >1 year, anti-epileptic drug therapy in general and in patients receiving polytherapy in particular (all p < 0.001). Our data suggest that polytherapy, but not monotherapy or the subtype of epilepsy, might have a slowing impact on pre-attentive cognitive processing.

Illusory conjunctions and perceptual grouping in a visual search task in schizophrenia

This report describes part of a series of experiments, conducted within the framework of feature integration theory, to determine whether patients with schizophrenia show deficits in preattentive processing. Thirty subjects with a DSM-III-R diagnosis of schizophrenia and 30 age-, gender-, and education-matched normal control subjects completed two computerized experimental tasks, a visual search task assessing the frequency of illusory conjunctions (i.e. false perceptions) under conditions of divided attention (Experiment 3) and a task which examined the effects of perceptual grouping on illusory conjunctions (Experiment 4). We also assessed current symptomatology and its relationship to task performance. Contrary to our hypotheses, schizophrenia subjects did not show higher rates of illusory conjunctions, and the influence of perceptual grouping on the frequency of illusory conjunctions was similar for schizophrenia and control subjects. Nonetheless, specific predictions from feature integration theory about the impact of different target types (Experiment 3) and perceptual groups (Experiment 4) on the likelihood of forming an illusory conjunction were strongly supported, thereby confirming the integrity of the experimental procedures. Overall, these studies revealed no firm evidence that schizophrenia is associated with a preattentive abnormality in visual search using stimuli that differ on the basis of physical characteristics.

Preattentive visual search and perceptual grouping in schizophrenia

To help determine whether patients with schizophrenia show deficits in the stimulus-based aspects of preattentive processing, we undertook a series of experiments within the framework of feature integration theory. Thirty subjects with a DSM-III-R diagnosis of schizophrenia and 30 age-, gender-, and education-matched normal control subjects completed two computerized experimental tasks, a visual search task assessing parallel and serial information processing (Experiment 1) and a task which examined the effects of perceptual grouping on visual search strategies (Experiment 2). We also assessed current symptomatology and its relationship to task performance. While the schizophrenia subjects had longer reaction times in Experiment 1, their overall pattern of performance across both experimental tasks was similar to that of the control subjects, and generally unrelated to current symptomatology. Predictions from feature integration theory about the impact of varying display size (Experiment 1) and number of perceptual groups (Experiment 2) on the detection of feature and conjunction targets were strongly supported. This study revealed no firm evidence that schizophrenia is associated with a preattentive abnormality in visual search using stimuli that differ on the basis of physical characteristics. While subject and task characteristics may partially account for differences between this and previous studies, it is more likely that preattentive processing abnormalities in schizophrenia may occur only under conditions involving selected 'top-down' factors such as context and meaning.

Preattentive and focal attentional processes in schizophrenia: a visual search study

Using a visual search task, the present study investigated preattentive and focal attentional processes in schizophrenic patients. The performance of 15 schizophrenic patients and 20 normal subjects was compared in three search tasks: feature search, 2-D feature search, and conjunction search. The target item was a red 'X' in all search tasks, and the distractor items were red 'O' in the feature search, green 'O' in the 2-D feature search, and red 'O' and green 'X' in the conjunction search. Set size total number of items presented in the display was 4, 16, or 25. Reaction times (RTs) for the subject's correct detection of target presence and absence were measured, and slopes of linear function relating RT to set size were computed. In the feature and the 2-D feature search, the schizophrenic subjects showed nearly zero slopes as did the normal subjects, indicating that in the preattentive process the schizophrenic patients functioned at a normal level. In the conjunction search, the schizophrenic subjects showed steeper slopes than the normal subjects for target absence (but not for target presence), suggesting that there was a deficit in the focal attentional process. Those results are consistent with the view of Callaway and Naghdi (1982) that a deficit in schizophrenic patients is mainly confined to the attentional process (cf., Lieb et al., 1994).

Preattentive information processing as measured by backward masking and texton detection tasks in adolescents at high genetic risk for schizophrenia

Schizophrenic patients have consistently been reported to show deficits in preattentive information processing as demonstrated by impairments in visual backward masking and texton detection tasks. Texton detection refers to Julesz's texton theory, which defines a certain limited number of texton elements (e.g., one 'L' among many '+') that can be detected readily and simultaneously without attentional effort irrespective of the size of the rest of the visual field. The present study investigated whether deficits of preattentive information processing are more prevalent in a group of adolescents of high genetic risk for schizophrenia compared to matched control subjects. Although differences in the performance in visual backward masking tasks could not be detected with our experimental approach, preattentive texton detection was to a certain extent disturbed in subjects at risk. Moreover, subjects at risk did not show the advantage of the right hemisphere in processing texton elements which was found in the control group. This may point to a subtle dysfunction of the right hemisphere in the risk group. It is concluded from the present study that deficits in preattentive texton detection may represent an indicator for a schizophrenic disposition. However, further studies including other high risk groups, schizophrenics in remission and individuals with a schizotypal personality disorder are needed to confirm this hypothesis.