Reduced Speed Of Information Processing Research Articles

Mental fatigue and chronic fatigue syndrome in clinical practice

Fatigue is an extremely disabling symptom both in healthy people and in various diseases. Physical fatigue is characterized by limitations in physical functioning, while mental/cognitive fatigue involves difficulties in concentrating and performing cognitive tasks. Mental and physical fatigue exist in both pathological and physiological fatigue. Fatigue is primarily an adaptive physiological process. It is a signal to have a rest and helps conserve energy to prevent injury, which can be useful after intense work, or when the body’s defenses need to be redistributed, for example, during infectious disease. It is important to distinguish between fatigue or tiredness and chronic fatigue syndrome in clinical practice. Chronic fatigue syndrome has multisystem manifestations and affects millions of people globally. Although the exact aetiology of chronic fatigue syndrome is uncertain, the studies point to neurological, immunological, autonomic and energy disorders. The main sings of chronic fatigue syndrome are debilitating fatigue that is worsened by activity, poor exercise tolerance, unrefreshing sleep and cognitive impairment. Reduced information processing speed is the most common cognitive impairment in chronic fatigue syndrome. Other manifestations include decreased reaction time, working memory, and attention. These symptoms must persist for at least 3–6 months for a diagnosis to be made. As there are no specific tests for chronic fatigue syndrome, a diagnosis can be established on the basis of a medical history and physical examination.Although there are no standards-based methods specific to chronic fatigue syndrome, clinicians can reduce the severity of symptoms using pharmacological and non-pharmacological treatment approaches that have proved their efficacy in clinical practice. In particular, nootropics are widely used in asthenic conditions and chronic fatigue syndrome. Fonturacetam is a nootropic drug that directly activates brain integration activities, promotes memory consolidation, and improves concentration and mental activity.

Impact of depression on the perception of fatigue and information processing speed in a cohort of multiple sclerosis patients

BackgroundInformation processing speed is commonly impaired in people with multiple sclerosis (PwMS). However, depression and fatigue can affect the cognitive profile of patients: fatigue has a negative impact from the disease’s earliest stage and a reduced information processing speed is often associated with higher levels of depression. Therefore, the aim of this study was to investigate the correlations between information processing speed and physical fatigue in a cohort of Italian PwMS from a single center, considering the effect of depression.MethodsTwo hundred (W = 128; mean age = 39.83 years; SD = 11.86) PwMS, from the Bari University Hospital, underwent testing for processing speed (Symbol Digit Modalities Test [SDMT]), fatigue level (Fatigue Severity Scale [FSS]), and depression (Beck’s Depression Inventory [BDI]).ResultsStatistically significant correlations emerged between SDMT and FSS, SDMT and BDI, FSS and BDI. Mediation analyses revealed that while physical fatigue had no significant direct negative effect on information processing speed (z=-0.891; p > 0.05), depression predicted the relationship between fatigue and information processing speed (z=-2.181; p < 0.05).ConclusionOur findings showed that cognitive performance at SDMT was not affected by patients’ perceived level of physical fatigue, but by depression. The presence of a high BDI score mediates the physical fatigue on cognitive performance impact.

Effect of deep gray matter atrophy on information processing speed in early relapsing-remitting multiple sclerosis.

Cognitive dysfunction, including reduced Information processing speed (IPS), is relatively common in multiple sclerosis(MS). IPS deficits have profound effects on several aspects of patients' life. Previous studies showed that deep gray matter atrophy is highly correlated with overall cognitive impairment in MS. However, the effect of deep gray matter atrophy on IPS deficits is not well understood. In this study, we evaluated the effects of deep gray matter volume changes on IPS in people with early relapse-remitting MS (RRMS) compared to healthy control. In this case-control study, we enrolled 63 case with RRMS and 36 healthy controls. All patients were diagnosed within 6 years. IPS was evaluated using the Integrated Cognitive Assessment (ICA) test. We also performed a 1.5T MRI to evaluate deep gray matter structures. People with RRMS had lower accuracy in the ICA test (p=.01). However, the reaction time did not significantly differ between RRMS and control groups (p=.6). Thalamus volume was significantly lower in the RRMS group with impaired IPS compared to the RRMS with normal IPS and control groups (p<10-4). Other deep gray matter structures were not significantly different between the RRMS with impaired IPS group and the RRMS with normal IPS group. Some people with MS are impaired in IPS even in the early stages of the disease. Thalamic atrophy affected IPS in these patients, however atrophy in other deep gray matter structures, including caudate, putamen, globus pallidus, hippocampus, amygdala, accumbens, and cerebellum, were not significantly correlated with IPS impairment in early RRMS.

Cognitive impairment in multiple sclerosis: Utility of electroencephalography.

to evaluate associations between neurocognitive impairment and electroencephalography (EEG) data in Multiple Sclerosis (MS). patients aged between 18 and 65 years, diagnosed with MS accordingly to the McDonald 2017 criteria and who were in remission for at least one month were included. Cognitive functions were evaluated by validated neuropsychological tests for Tunisian population. Electroencephalography data of each patient were analysed, Grand Total EEG (GTE) score was calculated and we evaluated their statistical links with cognitive impairment. Thirty five patients were included. Slower background activity was associated with presence of: reduced information processing speed (IPS) (p=0,03), verbal memory impairment (p=0,04) and executive dysfunction (p=0,016). The score 3 of GTE (reactivity of background activity) was associated with reduced IPS (p=0,007) and executive dysfunction (p=0,014). We found a positive correlation between background activity and Tunisian Verbal Test (TVLT) (ρ =0,46; p=0,005) and Symbol Digit Modalities Test (SDMT) (ρ =0,35; p=0,03). Sensitivity of GTE score was 68,4% for executive dysfunction (cut-off=2,5) and 66,7% for reduced IPS (cut-off=2,5). Our results have shown utility of EEG in detecting cortical involvement and its correlation with cognitive impairment in MS patients. EEG could be a tool for monitoring cortical involvement during MS and predict cognitive impairment.

Personality factors and cognitive functioning in patients with somatic symptom and related disorders

ObjectiveSomatic symptom and related disorders (SSRD) are often complicated by cognitive symptoms, including reduced information processing speed, memory, and planning. Depression has been related to poor cognitive functioning in SSRD, but the role of underlying personality factors is poorly understood. This study investigates the association between personality factors (neuroticism, extraversion, openness, agreeableness, and conscientiousness) with cognitive functioning in patients with SSRD. MethodsData from 366 patients with SSRD from a tertiary care expert center (mean age = 42.1 years (SD = 13.4), 59.6% women) were analyzed using a cross-sectional design. Neuropsychological assessments included measures of information processing speed, memory, attention, and executive function. Personality factors were assessed using the NEO-FFI and depressive symptoms using the PHQ-9. ResultsRegression analyses showed associations between neuroticism with poorer performance on visual memory (B = −0.09, SE = 0.04, β = −0.14, p = .019), and planning (B = −0.09. SE = 0.02, β = −0.23, p < .001). Extraversion was also inversely associated with visual memory (B = −0.13, SE = 0.05, β = −0.18, p = .011) and planning (B = −0.07, SE = 0.03, β = −0.17, p = .021) and openness was associated with better visual memory (B = 0.17, SE = 0.05, β = 0.19, p = .002). These associations were attenuated but remained significant after adjusting for depressive symptoms. ConclusionNeuroticism, extraversion, and low openness were associated with lower cognitive functioning (particularly planning and visual memory) in patients with SSRD, which remained significant after taking depressive symptoms into account.

Theory of Mind and social functioning among neuropsychiatric disorders: A transdiagnostic study

Social dysfunction is commonly present in neuropsychiatric disorders of schizophrenia (SZ) and Alzheimer's disease (AD). Theory of Mind (ToM) deficits have been linked to social dysfunction in disease-specific studies. Nevertheless, it remains unclear how ToM is related to social functioning across these disorders, and which factors contribute to this relationship. We investigated transdiagnostic associations between ToM and social functioning among SZ/AD patients and healthy controls, and explored to what extent these associations relate to information processing speed or facial emotion recognition capacity. A total of 163 participants were included (SZ: n=56, AD: n=50 and age-matched controls: n=57). Social functioning was assessed with the Social Functioning Scale (SFS) and the De Jong-Gierveld Loneliness Scale (LON). ToM was measured with the Hinting Task. Information processing speed was measured by the Digit Symbol Substitution Test (DSST) and facial emotion recognition capacity by the facial emotion recognition task (FERT). Case-control deficits in Hinting Task performance were larger in AD (rrb = -0.57) compared to SZ (rrb = -0.35). Poorer Hinting Task performance was transdiagnostically associated with the SFS (βHinting-Task = 1.20, p<0.01) and LON (βHinting-Task = -0.27, p<0.05). DSST, but not FERT, reduced the association between the SFS and Hinting Task performance, however the association remained significant (βHinting-Task = 0.95, p<0.05). DSST and FERT performances did not change the association between LON and Hinting Task performance. Taken together, ToM deficits are transdiagnostically associated with social dysfunction and this is partly related to reduced information processing speed.

Effect of organophosphate pesticides poisoning on cognitive impairment

It has been suggested that organophosphate pesticides can cause cognitive impairment, most of which are presented as mild cognitive impairment such as decreased attention or vigilance, reduced information processing speed and memory impairment. An early diagnosis and timely intervention in mild cognitive impairment, which may provide a better prognosis. Mild cognitive impairment in clinical work can be easily ignored for a long time. However, it have a particularly impact on patients' life and work, and even progress to irreversible neurodegenerative diseases such as Alzheimer's disease and Parkinson's disease. Therefore, clinicians should raise the cognition of organophosphate pesticides poisoning in patients with cognitive impairment, especially for patients with mild cognitive impairment, and the significance of early detection and diagnosis of the disease is particularly important.

Association of White Matter With Core Cognitive Deficits in Patients With Schizophrenia

Efforts to remediate the multiple cognitive function impairments in schizophrenia should consider white matter as one of the underlying neural mechanisms. To determine whether altered structural brain connectivity is responsible for 2 of the core cognitive deficits in schizophrenia- reduced information processing speed and impaired working memory. This cross-sectional study design took place in outpatient clinics from August 1, 2004, to August 31, 2015. Participants included 166 patients with schizophrenia and 213 healthy control individuals. These participants were from 3 independent cohorts, each of which had its own healthy control group. No participant had current or past neurological conditions or major medical conditions. Patients were diagnosed with either schizophrenia or schizoaffective disorder as defined by the DSM-IV. Controls had no Axis I psychiatric disorder. Mediation analyses and structural equation modeling were used to analyze the associations among processing speed, working memory, and white matter microstructures. Whole-brain and regional diffusion tensor imaging fractional anisotropy were used to measure white matter microstructures. Of the study participants, the 166 patients with schizophrenia had a mean (SD) age of 38.2 (13.3) years and the 213 healthy controls had a mean (SD) age of 39.2 (14.0) years. There were significantly more male patients than controls in each of the 3 cohorts (117 [70%] vs 91 [43%]), but there were no significant differences in sex composition among the 3 cohorts. Patients had significantly reduced processing speed (Cohen d = 1.24; P = 6.91 × 10-30) and working memory deficits (Cohen d = 0.83; P = 1.10 × 10-14) as well as a significant whole-brain fractional anisotropy deficit (Cohen d = 0.63; P = 2.20 × 10-9). In schizophrenia, working memory deficit was mostly accounted for by processing speed deficit, but this deficit remained when accounting for working memory (Cohen d = 0.89; P = 2.21 × 10-17). Mediation analyses showed a significant association pathway from fractional anisotropy to processing speed to working memory (P = 5.01 × 10-7). The strength of this brain-to-cognition pathway in different white matter tracts was strongly associated with the severity of schizophrenia-associated fractional anisotropy deficits in the corresponding white matter tracts as determined by a meta-analysis (r = 0.85-0.94; all P < .001). The same pattern was observed in patients and controls either jointly or independently. Study findings suggest that (1) processing speed contributes to the association between white matter microstructure and working memory in schizophrenia and (2) white matter impairment in schizophrenia is regional tract-specific, particularly in tracts normally supporting processing speed performance.

Reduced information processing speed and event-related EEG synchronization in traumatic brain injury (P6.149)

Reduced information processing speed and event-related EEG synchronization in traumatic brain injury (P6.149)

Reduced information processing speed as primum movens for cognitive decline in MS

Background: Cognitive impairment affects half of the multiple sclerosis (MS) patient population and is an important contributor to patients’ daily activities. Most cognitive impairment studies in MS are, however, cross-sectional or/and focused on the early disease stages. Objective: We aim to assess the time course of decline of different cognitive domains. Methods: We collected neuropsychological data on 514 MS patients to construct Kaplan-Meier survival curves of the tests included in the Neuropsychological Screening Battery for MS (NSBMS) and the Symbol Digit Modalities Test (SDMT). Cox-proportional hazard models were constructed to examine the influence of MS onset type, age at onset, gender, depression and level of education on the time course, expressed as age or disease. Results: Survival curves of tests focusing on information processing speed (IPS) declined significantly faster than tests with less specific demands of IPS. Median age for pathological decline was 56.2 years (95% CI: 54.4–58.2) on the SDMT and 63.9 years (95% CI: 60–66.9) on the CLTR, a memory task. Conclusion: In conclusion, IPS is the cognitive domain not only most widely affected by MS but it is also the first cognitive deficit to emerge in MS.

Disturbed phase relations in white matter hyperintensity based vascular dementia: An EEG directed connectivity study

ObjectiveWhite matter hyperintensities (WMH), a feature seen on magnetic resonance imaging (MRI) and regarded to reflect small vessel disease, can lead to vascular dementia (WMH-VaD). In WMH-VaD, cognitive deficits typically consist of executive function disturbances, and reduced information processing speed, regarded as a result of cerebral hypoperfusion. We aimed to investigate whether this patient group has typical functional differences from controls. MethodsResting-state encephalography studies of 17 VaD patients and 17 age- and gender matched non-demented controls were analysed in the delta, theta, alpha1 and 2, and beta frequency bands. Undirected functional connectivity between electrodes was established with the Phase Lag Index (PLI) and directed functional connectivity with the directed Phase Lag Index (dPLI). PLI and dPLI were related to performance in cognitive testing. ResultsMean PLI did not differ between patients and controls. In the control group dPLI showed anterior to posterior phase gradients in all bands except the delta band. In the VaD patient group this pattern was significantly different without a clear directional pattern. No relationship with cognition was demonstrated. ConclusionsThis study shows a clear front-to-back direction of connectivity in non-demented controls. In VaD patients with extensive WMH, this pattern is disturbed. SignificanceStructural damage at the regions of long distance white matter tracts may induce changes in the direction of phase relationships of distinct brain regions.

Information processing speed in obstructive sleep apnea syndrome: a review

To provide a comprehensive review of studies on information processing speed in patients with obstructive sleep apnea syndrome (OSAS) as compared to healthy controls and normative data, and to determine whether continuous positive airway pressure (CPAP) treatment improves information processing speed. A systematic review was performed on studies drawn from Medline and PsycINFO (January 1990-December 2011) and identified from lists of references in these studies. After inclusion criteria, 159 articles were left for abstract review, and after exclusion criteria 44 articles were fully reviewed. The number of patients in the studies reviewed ranged from 10 to 157 and the study samples consisted mainly of men. Half of the studies reported that patients with OSAS showed reduced information processing speed when compared to healthy controls. Reduced information processing speed was seen more often (75%) when compared to norm-referenced data. Psychomotor speed seemed to be particularly liable to change. CPAP treatment improved processing speed, but the improvement was marginal when compared to placebo or conservative treatment. Patients with OSAS are affected by reduced information processing speed, which may persist despite CPAP treatment. Information processing is usually assessed as part of other cognitive functioning, not as a cognitive domain per se. However, it is important to take account of information processing speed when assessing other aspects of cognitive functioning. This will make it possible to determine whether cognitive decline in patients with OSAS is based on lower-level or higher-level cognitive processes or both.

Markers of low-grade inflammation and endothelial dysfunction are related to reduced information processing speed and executive functioning in an older population – the Hoorn Study

Low-grade inflammation and endothelial dysfunction are related to cognitive decline and dementia, in a complex interplay with vascular factors and aging. We investigated, in an older population, low-grade inflammation and endothelial dysfunction in relation to detailed assessment of cognitive functioning. Furthermore, we explored this association within the context of vascular factors. 377 participants (73 ± 6 years) of the population-based Hoorn Study were included. In plasma samples of 2000-2001 (n=363) and/or 2005-2008 (n=323), biomarkers were determined of low-grade inflammation (CRP, TNF-alpha, IL-6, IL-8, SAA, MPO, and sICAM-1) and endothelial dysfunction (vWF, sICAM-1, sVCAM-1, sTM, sE-selectin). In 2005-2008, all participants underwent neuropsychological examination. Composite z-scores were computed for low-grade inflammation and endothelial dysfunction at both time points, and for six domains of cognitive functioning (abstract reasoning, memory, information processing speed, attention and executive functioning, visuoconstruction, and language). The association between low-grade inflammation and endothelial dysfunction, and cognitive functioning was evaluated with linear regression analysis. In secondary analyses, we explored the relation with vascular risk factors and cardiovascular disease. Low-grade inflammation and endothelial dysfunction were associated with worse performance on information processing speed and attention and executive functioning, in prospective and cross-sectional analyses (standardized betas ranging from -0.20 to -0.10). No significant relation with other cognitive domains was observed. Adjusting for vascular factors slightly attenuated the associations. Low-grade inflammation and endothelial dysfunction accounted for only 2.6% explained variance in cognitive functioning, on top of related vascular risk factors and cardiovascular disease. Bootstrapping analyses show that low-grade inflammation and endothelial dysfunction mediate the relation between vascular risk factors and cognitive functioning. This study shows that low-grade inflammation and endothelial dysfunction contribute to reduced information processing speed and executive functioning in an older population.

Effects of cannabis use on event related potentials in subjects at ultra high risk for psychosis and healthy controls

Cannabis use has consistently been associated with psychotic symptoms as well as cognitive impairments. Moreover, its use may provoke subclinical psychotic symptoms and is associated with neuropsychological dysfunctions in subjects at ultra high risk (UHR) for developing psychosis. However, to our knowledge, no data are yet available on the relationship between cannabis use, UHR symptoms and information processing as assessed with event related potentials (ERP) in UHR subjects. This cross-sectional study therefore aimed to investigate N100, N200, P200 and P300 ERP components in 48 UHR subjects (19 cannabis users; UHR+C) and 50 healthy controls (21 cannabis users; HC+C). Results showed smaller P300 amplitudes in HC+C and UHR subjects compared to HC−C. Moreover, HC+C showed prolonged P300 and N200 latencies compared to HC−C and UHR−C. No significant ERP differences were found between UHR+C and UHR−C. Regarding the relationship between information processing and psychopathology, we found associations between ERP components and severity of UHR symptoms, findings being most pronounced for N100 latencies and P300 amplitudes and severity of general psychopathology and positive symptoms. We conclude that UHR subjects and healthy cannabis users demonstrate similar P300 amplitude reductions compared to non-using control subjects. In addition, the interrelation of cannabis use with prolonged ERP latencies may signify reduced information processing speed associated with cannabis use. Finally, our findings cautiously support the hypothesis that the clinical phenomena of the UHR state may be associated with abnormalities in stimulus processing.

Neuropsychological functioning in late-life depression

Background: The literature describing neurocognitive function in patients with late-life depression (LLD) show inconsistent findings in regard to incidence and main deficits. Reduced information processing speed is in some studies found to explain deficits in higher order cognitive function, while other studies report specific deficits in memory and executive function. Our aim was to determine the characteristics of neuropsychological functioning in non-demented LLD patients.Methods: A comprehensive neuropsychological battery was administered to a group of hospitalized LLD patients and healthy control (HC) subjects. Thirty-nine patients without dementia, 60 years or older meeting DSM-IV criteria for current episode of major depression, and 18 non-depressed control subjects were included. The patient group was characterized by having a long lasting current depressive episode of late-onset depression and by being non-responders to treatment with antidepressants. Neurocognitive scores were calculated for the domains of information processing speed, verbal memory, visuospatial memory, executive function, and language. Number of impairments (performance below the 10th percentile of the control group per domain) for each participant was calculated.Results: Nearly half of the patients had a clinically significant cognitive impairment in at least one neurocognitive domain. Relative to HC subjects, LLD patients performed significantly poorer in the domains of information processing speed and executive function. Executive abilities were most frequently impaired in the patient group (39% of the patients). Even when controlling for differences in processing speed, patients showed more executive deficits than controls.Conclusions: Controlling for processing speed, patients still showed impaired executive function compared to HCs. Reduced executive function thus appears to be the core neurocognitive deficit in LLD. Executive function seems to be an umbrella concept for several connected but distinct cognitive functions. Further studies of neuropsychological functioning in LLD patients are needed to characterize more specific what kinds of executive impairments patients have. Additional studies of remitted LLD patients are needed to separate episode-related and persistent impairments.

Cognitive impairment in clinically isolated syndrome: A systematic review.

The pattern of cognitive abnormalities in multiple sclerosis (MS) has been extensively studied and well characterized. However, little is known about the cognitive involvement in patients with the clinically isolated syndrome (CIS).ObjectivesTo perform a systematic review of the results of the studies on cognitive dysfunction in CIS patients.MethodsCochrane, Lilacs, PubMed/Medline and SciELO databases were searched for studies involving patients with clinically isolated syndrome submitted to neuropsychological evaluation.ResultsSeven studies fulfilled the selection criteria adopted in this review. The pattern of cognitive abnormalities in CIS resembles that found in patients with MS and is characterized by attention deficit, reduced information processing speed and impaired working memory and executive functions. The frequency of cognitive impairment in CIS seems to be lower than in MS.ConclusionsCognition should be evaluated in patients with CIS. Future studies are required to evaluate the impact of cognitive abnormalities and to correlate them with axonal damage findings in patients with CIS.

Merging into heavy motorway traffic by young and elderly drivers

An increase in the number of Heavy Goods Vehicles on motorways may lead to additional problems in the interaction with an increased number of elderly drivers. Elderly drivers suffer from reduced information processing speed and capacity, and in general effectively compensate for this by taking more time. However, this strategy, regulating task demands by slowing down will make merging into motorway traffic actually more difficult. In an experiment performed in a driving simulator, young and elderly drivers merged into motorway traffic. Driver behaviour and mental workload were studied while the following factors were manipulated: type of traffic and density of Heavy Goods Vehicles on the main road, the length of the acceleration lane, presence of a slowly driving lead car, and presence of a driver support system that encouraged the drivers to speed up if their speed was too low. Results show that the effects of an increased number of Heavy Goods Vehicles on the main road were not more adverse for elderly than for the young participants, with the exception that elderly drivers merged at a lower speed. This lower speed could make the manoeuvre more risky in real traffic. The support system and an extended acceleration lane facilitated merging, while a slowly driving lead car impeded completion of the manoeuvre.

Neuropsychological and positron emission tomography correlates in idiopathic environmental intolerances

It has been hypothesized that people with subjective hypersensitivity to chemicals may indeed suffer from neuronal damage due to widely distributed environmental toxins and that such deficits of diagnostic importance can be demonstrated with the help of functional neuroimaging even in single cases. In this study, a small group of well-characterized patients with idiopathic environmental intolerance were examined in order to identify such changes. Twelve patients with idiopathic environmental intolerance were investigated neuropsychologically and underwent cerebral F-18 fluorodeoxyglucose (F-18 FDG) positron emission tomography (PET). The imaging results were compared with findings from 17 healthy controls. Six patients showed deficits in verbal learning and memory, three of them also had a reduced information processing speed. In the individual analyses, 11 patients showed normal cerebral glucose metabolism. In the group analysis of the patients, no areas with significantly reduced glucose metabolism could be found. No consistent pathological cognitive performance and functional imaging pattern was found. It appears premature to claim specific neuropsychological or neuroimaging findings characteristic of idiopathic environmental intolerance. Therefore cerebral F-18 FDG PET should not be used to corroborate or rule out suspected idiopathic environmental intolerance, a syndrome whose potential biological underpinnings still need to be clarified.

Functional Outcome in TBI II: Verbal Memory and Information Processing Speed Mediators

Following traumatic brain injury (TBI), patients often report memory difficulties, as well as reduced information processing speed. However, it remains unclear the extent to which these deficits contribute to functional impairment. In the present study, we compared the relative contribution of verbal memory and information processing speed to functional impairment at 12-month post-injury, in 87 patients with moderate-to-severe TBI. Employing structural equation modeling, we found that information processing speed, but not verbal memory functions, significantly mediated the relationship between TBI severity and post-TBI adaptive functioning. These findings suggest that despite the pervasive memory complaints among patients with TBI, it is the impact of neurotrauma on frontal systems that appears to be primarily responsible for patients' difficulties in social and occupational functioning.

Spatial-temporal characteristics of perceptual organization following acquired brain injury

Objective: To assess characteristics of perceptual organization following brain injury. Research design: A repeated measures between groups design. Methods: Perceptual thresholds were compared between 10 persons with brain injury and 10 demographically matched healthy control subjects. Ten young control subjects were also tested to evaluate effects of normal ageing on these processes. Participants viewed stimuli on a computer monitor in which regularities existed in either the spatial or temporal domain. Psychophysical measurements were made of perceptual thresholds, as well as time required to process stimuli. Results: Relative to age-matched control subjects, patients were impaired on all measures, with greatest deficits in conditions that contained a temporal component. Impairment did not occur with normal ageing. Conclusions: These results reflect cognitive impairment resulting from reduced cortical integrative function as well as reduced information processing speed. Such deficits at this level of processing likely impact subsequent perceptual function, such as object recognition.