Posterior Cortical Functions Research Articles

Where is my hand? Proprioceptive disturbances in posterior cortical atrophy and typical Alzheimer’s disease

AbstractBackgroundPosterior cortical atrophy (PCA) is a neurodegenerative syndrome most commonly caused by Alzheimer’s disease (AD) pathology. PCA is often considered the canonical ‘visual dementia’, characterised by the progressive loss of visual and posterior cortical functions corresponding to parieto‐occipital and occipito‐temporal atrophy. However, patient reports of difficulties finding sleeves of clothes, transferring between postures and determining heading direction imply non‐visual disturbances, consistent with the multisensory role of the posterior parietal cortex. Such reports raise questions regarding AD clinical heterogeneity, representing a substantial challenge to patients' independence and management of PCA and typical AD (tAD).MethodPatient (total n = 39; PCA n = 23; tAD n = 16) and control (n = 19) participants repeatedly reached to a proprioceptive target (their non‐dominant thumb) (Fig.A) with and without vision and tactile feedback (n = 40 trials per participant). The target was positioned passively behind a screen apparatus at five positions using an adjustable foam handrest. The primary outcome measure was absolute (medio‐lateral) error determined using whole‐body motion capture data (Fig.B).ResultAbsolute error was greater without than with vision across groups. However, the effect of removing vision on absolute error was smallest in the control group (estimated mean error with vision [95%CI]: 15mm [6,25]; without vision: 23mm [14,32]), greatest in PCA (with vision: 39mm [30,49]; without vision: 76mm [67,86]) and intermediate in the tAD group (with vision: 26mm [16,37]; without vision: 49mm [39,60]) (vision‐by‐group interaction: p<.001; Fig.C). For ∼5% of trials, absolute error exceeded 200mm in PCA and 120mm in tAD participants (Fig.B; control range: 0.01‐80mm). There was no evidence of an effect of tactile feedback in any group.The effect of target location differed between groups (location‐by‐group interaction: p<.001). Patient reaching errors were particularly apparent under postures where the target arm crossed the body midline (e.g. left arm in right hemispace); this effect was notably evident in the PCA group even with available vision (Fig.C).ConclusionFindings emphasise disturbed spatial awareness in PCA and tAD in the absence of vision, consistent with diminished body position sense‐ proprioception ‐ which may be mediated centrally through posterior parietal vulnerability. Findings suggest implications for assessment and management of disabling dressing, mobility, navigation and balance difficulties.

Resting-state functional connectivity is modulated by cognitive reserve in early Parkinson's disease.

Fronto-striatal disconnection is thought to be at the basis of dysexecutive symptoms in patients with Parkinson's disease (PD). Multiple reserve-related processes may offer resilience against functional decline. Among these, cognitive reserve (CR) refers to the adaptability of cognitive processes. To test the hypothesis that functional connectivity of pathways associated with executive dysfunction in PD is modulated by CR. Twenty-six PD patients and 24 controls underwent resting-state functional magnetic resonance imaging. Functional connectivity was explored with independent component analysis and seed-based approaches. The following networks were selected from the outcome of the independent component analysis: default-mode (DMN), left and right fronto-parietal (l/rFPN), salience (SalN), sensorimotor (SMN), and occipital visual (OVN). Seed regions were selected in the substantia nigra and in the dorsolateral and ventromedial prefrontal cortex for the assessment of seed-based functional connectivity maps. Educational and occupational attainments were used as CR proxies. Compared with their counterparts with high CR, PD individuals with low CR had reduced posterior DMN functional connectivity in the anterior cingulate and basal ganglia, and bilaterally reduced connectivity in fronto-parietal regions within the networks defined by the dorsolateral and ventrolateral prefrontal seeds. Hyper-connectivity was detected within medial prefrontal regions when comparing low-CR PD with low-CR controls. CR may exert a modulatory effect on functional connectivity in basal ganglia and executive-attentional fronto-parietal networks. In PD patients with low CR, attentional control networks seem to be downregulated, whereas higher recruitment of medial frontal regions suggests compensation via an upregulation mechanism. This upregulation might contribute to maintaining efficient cognitive functioning when posterior cortical function is progressively reduced.

Decline in Visual and Posterior Cortical Functions in Logopenic Progressive Aphasia (P5-6.001)

<h3>Objective:</h3> To determine how frequently features of posterior cortical atrophy (PCA) occur in patients with logopenic progressive aphasia (LPA) and determine the neuroimaging correlates of these features. <h3>Background:</h3> LPA and PCA are two atypical clinical variants of Alzheimer’s disease. Overlap can be observed clinically between phenotypes, although it is unclear how frequently patients meeting criteria for LPA develop clinical PCA features, and whether these features are associated with neuroanatomical overlap with PCA. <h3>Design/Methods:</h3> Thirty-six LPA patients recruited by the Neurodegenerative Research Group underwent extensive neuropsychological testing, MRI and [¹⁸F] flortaucipir PET. All patients were evaluated for PCA features including simultanagnosia, Gerstmann syndromes, ideomotor apraxia, and visuospatial and visuoperceptual function, with cut-points used to define abnormality. Patients were classified as Pure-LPA (having no PCA feature), LPA+ (impairment on one test) or LPA-PCA (impairment on 2+ tests). Neuroimaging profiles in each of the three LPA groups were compared to 14 matched healthy controls and 14 matched typical PCA patients using multiple regression analysis in SPM12. <h3>Results:</h3> Eleven patients (31%) were classified as pure-LPA, 16 (44%) as LPA+ and 9 (25%) as LPA-PCA. There were no differences in disease duration, naming, or sentence repetition across groups. The LPA+ group showed worse simultanagnosia (29%), ideomotor apraxia and Gerstmann syndrome (34%) compared to Pure-LPA group. The LPA-PCA group showed further worsening in simultanagnosia (89%), and visuospatial and visuoperceptual impairment compared to LPA+ group. All three LPA groups showed greater left temporoparietal volume loss and flortaucipir uptake compared to controls and PCA, with greater flortaucipir uptake occurring in the occipital and frontal lobes in LPA+ and LPA-PCA compared to Pure-LPA. <h3>Conclusions:</h3> Our results demonstrate that LPA patients can develop features of PCA related to spread of tau into occipito-frontal regions, highlighting syndromic and anatomical overlap between atypical variants of AD. <b>Disclosure:</b> Dr. Singh has nothing to disclose. Dr. Graff-Radford has received personal compensation for serving as an employee of Mayo Clinic. Dr. Graff-Radford has received personal compensation in the range of $0-$499 for serving on a Scientific Advisory or Data Safety Monitoring board for NINDS/NIH. Dr. Graff-Radford has received personal compensation in the range of $5,000-$9,999 for serving as an Editor, Associate Editor, or Editorial Advisory Board Member for American Academy of Neurology. The institution of Dr. Graff-Radford has received research support from NIH. Arenn Faye Carlos, MD has nothing to disclose. The institution of Dr. Machulda has received research support from NIH. Christopher Schwarz has received personal compensation for serving as an employee of Mayo Clinic. The institution of Christopher Schwarz has received research support from NIH. Matthew Senjem has received stock or an ownership interest from Align Technology, Inc.. Matthew Senjem has received stock or an ownership interest from Inovio Biomedical Corp.. Matthew Senjem has received stock or an ownership interest from Johnson &amp; Johnson. Matthew Senjem has received stock or an ownership interest from Mesa Laboratories, Inc.. Matthew Senjem has received stock or an ownership interest from Nvidia Inc.. Matthew Senjem has received stock or an ownership interest from LHC Group, Inc.. Matthew Senjem has received stock or an ownership interest from Natus Medical Incorporated. Matthew Senjem has received stock or an ownership interest from Varex Imaging Corporation. Matthew Senjem has received personal compensation in the range of $100,000-$499,999 for serving as a IT Technical Specialist II with Mayo Clinic. The institution of Dr. Jack has received research support from NIH. The institution of Dr. Jack has received research support from Alexander Family Alzheimer’s Disease Research Professorship of the Mayo Clinic. Dr. Lowe has received personal compensation in the range of $10,000-$49,999 for serving as a Consultant for AVID Radiopharmaceutical. Dr. Lowe has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Eisai Inc. The institution of Dr. Lowe has received research support from AVID Radiopharmaceuticals. Dr. Josephs has nothing to disclose. Dr. Whitwell has nothing to disclose.

Better conversations: a language and communication intervention for aphasia in posterior cortical atrophy

ABSTRACT Posterior cortical atrophy (PCA) describes a neurodegenerative syndrome characterized by progressive difficulties in cortical visual and other posterior cortical functions consistent with parieto-occipital and occipito-temporal involvement. It is increasingly recognized that many patients develop difficulties with other aspects of daily living, in particular, with language and communication. We present a case emphasizing how language difficulties may emerge in PCA. Difficulties are interpreted as arising from interacting effects of linguistic deficits and impaired detection of nonverbal (particularly, visual) turns that normally facilitate, schedule, and disambiguate the exchange of verbal messages between speakers. We propose that relatively simple speech and language therapy interventions may hold promise in addressing language and communication difficulties as secondary features of PCA by targeting the behaviors of both the person with PCA and their communication partners.

Presence phenomena in parkinsonian disorders: Phenomenology and neuropsychological correlates.

The feeling of a presence that occurs in the absence of objectively identifiable stimuli is common in parkinsonian disorders. Although previously considered benign and insignificant, recent evidence suggests that presence phenomena may act as the gateway to more severe hallucinations and dementia. Despite this, we still know relatively little about these phenomena. To examine parkinsonian disorder patients' subjective experience of presence phenomena, and retrospectively analyse their cognitive correlates, in order to elucidate the emergence of information processing deficits in parkinsonian disorders. 25 patients who endorsed presence phenomena were asked to complete a semi-structured interview about their experiences. The cognitive profiles of these patients were then compared to those of age- and education-matched patients who denied presence phenomena. Patients described the presence as mostly that of an unknown human with neutral valence. Patients who described it as unpleasant were noted to also demonstrate elevated anxiety. Patients who identified the presence as a known person, described it as touching them, or interacted with the presence emotionally or physically demonstrated reduced insight. Patients with presence phenomena demonstrated more frequent impairments in visual processing, executive function and speed of processing. Presence phenomena occur in the company of advancing cognitive impairment and involvement of the posterior cortical functions. Initially encountered as a neutral spatial skeleton, the experience is then shaped by the patient's affective state and level of insight.

Effect of levodopa on frontal-subcortical and posterior cortical functioning in patients with Parkinson’s disease

Parkinson's disease (PD) is associated with cognitive decline but little is known about frontal-subcortical and posterior cortical cognitive functioning in patients with PD. The present study was designed to: (a) compare frontal and posterior cognitive functioning between patients with PD and healthy controls; (b) determine the effect of levodopa (L-dopa) on frontal-subcortical and posterior cortical cognitive functions; and (c) identify predictors of cognitive functions in patients with PD. 50 patients diagnosed with PD from April 2016 to May 2017 at Civil Hospital, Bahawal Victoria Hospital, Bahawalpur, and Nishter Hospital Multan, Pakistan, and 50 healthy individuals from the community participated in our study. Patients had two testing sessions - first, at the time of diagnosis before taking L-dopa medication to determine baseline scores; and second, after at least three months of L-dopa medication. Participants completed the Parkinson's Disease-Cognitive Rating Scale. Patients with PD showed impaired performance on frontal-subcortical and posterior cortical functions in contrast with the control group. L-dopa medication had beneficial effects on frontal-subcortical and posterior cortical functioning in patients with PD. Disease duration was a significant predictor of cognitive performance in patients with PD. L-dopa medication improves frontal-subcortical and posterior cortical cognitive functioning in patients with PD. Disease duration is a marker of cognitive decline in PD.

Increased Prefrontal Activity with Aging Reflects Nonspecific Neural Responses Rather than Compensation

Elevated prefrontal cortex activity is often observed in healthy older adults despite declines in their memory and other cognitive functions. According to one view, this activity reflects a compensatory functional posterior-to-anterior shift, which contributes to maintenance of cognitive performance when posterior cortical function is impaired. Alternatively, the increased prefrontal activity may be less efficient or less specific because of structural and neurochemical changes accompanying aging. These accounts are difficult to distinguish on the basis of average activity levels within brain regions. Instead, we used a novel, model-based multivariate analysis technique applied to two independent fMRI datasets from an adult-lifespan human sample (N = 123 and N = 115; approximately half female). Standard analysis replicated the age-related increase in average prefrontal activation, but multivariate tests revealed that this activity did not carry additional information. The results contradict the hypothesis of a compensatory posterior-to-anterior shift. Instead, they suggest that the increased prefrontal activation reflects reduced efficiency or specificity rather than compensation.SIGNIFICANCE STATEMENT Functional brain imaging studies have often shown increased activity in prefrontal brain regions in older adults. This has been proposed to reflect a compensatory shift to greater reliance on prefrontal cortex (PFC), helping to maintain cognitive function. Alternatively, activity may become less specific as people age. This is a key question in the neuroscience of aging. In this study, we used novel tests of how different brain regions contribute to long- and short-term memory. We found increased activity in PFC in older adults, but this activity carried less information about memory outcomes than activity in visual regions. These findings are relevant for understanding why cognitive abilities decline with age, suggesting that optimal function depends on successful brain maintenance rather than compensation.

Frontal-subcortical defects correlate with task switching deficits in Parkinson`s disease.

Objectives:To examine correlation between frontal-subcortical/ parietal-cortical functioning and task switching.Methods:An experimental study was designed to examine objectives with 80 participants (40 patients with idiopathic Parkinson’s disease (PD) and 40 healthy controls). Patients were recruited from February until September 2016 at Recep Tayyip Erdogan Hospital Pakistan, Muzaffargarh, Pakistan and healthy controls participated from community. Participants were administered Parkinson’s disease cognitive rating scale and Word-Digit categorization task switching experiment.Results:In contrast to healthy controls, (i) PD patients showed impaired cognitive performance on frontal-subcortical and posterior-cortical functions as assessed through PD cognitive rating scale (ii) PD patients showed task switching deficits. Frontal-subcortical defects correlated with task switching deficits. Lesser the scores on frontal-subcortical functions, larger switch costs will appear. Frontal-subcortical defects significantly predicted task switch costs.Conclusion:Frontal-subcortical not the posterior-cortical dysfunctions are significant marker of task switching deficits.

Oculomotor abnormalities in posterior cortical atrophy: are they different from those in Alzheimer's disease after all?

This scientific commentary refers to ‘Abnormalities of fixation, saccade and pursuit in posterior cortical atrophy’, by Shakespeare et al. (doi:10.1093/brain/awv103). Posterior cortical atrophy (PCA) is a progressive degenerative condition characterized by a gradual loss of visual skills and other posterior cortical functions due to atrophy of parietal, occipital and occipito-temporal brain regions (Lehmann et al. , 2011). It is associated with a relative preservation of memory, language skills and judgement until late in the clinical course. Core features of PCA include partial or complete Balint’s syndrome (simultanagnosia, optic ataxia and ocular apraxia) and Gerstmann’s syndrome (acalculia, agraphia, finger agnosia), along with various combinations of visuo-spatial and visuo-perceptual impairments (Crutch et al. , 2012), apparent despite an otherwise normal ophthalmological examination. In this issue of Brain , Shakespeare et al. (2015) compare and contrast eye movement abnormalities revealed by basic oculomotor tests in patients with PCA, typical Alzheimer’s disease and healthy controls, in order to determine the extent to which abnormalities in basic (lower-order) oculomotor function contribute to visuo-perceptual disturbances in PCA (Shakespeare et al. , 2015). Patients with PCA typically present when they are between 50 and 65 years of age (Crutch et al. , 2012). One of the most important manifestations of PCA is simultanagnosia, an inability to synthesize the overall meaning of a visual scene despite being able to identify its individual elements; this should be suspected when a patient presents with an inability to read pseudo-isochromatic plates, despite intact colour vision (Beh et al. , 2015). The relative rarity of PCA makes it difficult to recruit large cohorts, but recently the number of studies of this disorder, often referred to as the cardinal visual dementia and the most common atypical Alzheimer’s disease phenotype, has been increasing. The study of …

J01 Cognitive alterations in Huntington's disease

Cognitive impairment constitutes one of the triad symptoms characterising Huntington9s disease (HD). Nevertheless, while some patients can remain relatively stable for a long time, others can exhibit cognitive defects for more than 15 years prior the diagnosis. The role of cognition in HD is under the focus of interest by the urgent need for objective biomarkers to track and attack the evolution of HD from the pre-symptomatic stage (preHD). Longitudinal follow-up studies demonstrated by means of neuropsychological testing some significant changes differentiating HD patients from preHD and controls. However, the differentiation between controls and preHD resulted controversial. Recent neuroimaging studies demonstrated -by means of progression of cortical thinning- a significant reduction in posterior-cortical areas in preHD population. However, most of the studies focused over cognitive assessment in HD outweighed the assessment of frontal-executive domains over posterior-cortical functions. As occurred in other neurodegenerative disorders, there is a need for a conceptualisation of the concept of mild cognitive impairment in HD based on an accurate differentiation between symptoms heralding different patterns of progression than those without prognostic values. The development of specific instruments for cognitive assessment in HD must represent a necessary step in order to better capture clinically meaningful cognitive symptoms from the preHD stage.

Visualizing the emergence of posterior cortical atrophy

Posterior cortical atrophy (PCA) is a neurodegenerative condition characterized by a progressive loss of visual processing skills and other posterior functions. Diagnosis is often delayed in PCA as symptoms can be difficult for the patient to articulate and for the clinician to detect. Diagnosis is particularly challenging in the earliest stages of the disease since visual symptoms are often mistaken as being related to ocular rather than cortical dysfunction. This report describes a 61-year-old man who volunteered as a healthy control participant in a longitudinal research study and was followed up for 5 years. During that time he showed a gradual decline in posterior cortical functions including visuoperceptual, visuospatial, and literacy impairments in the context of intact verbal episodic memory. Structural image analysis revealed atrophy which was initially most marked in inferior temporal and posterior parietal cortices before spreading to occipital cortices and subsequently to more anterior regions. Based on the clinical, neuropsychological and neuroimaging features, a diagnosis of PCA was made. The present case represents a unique opportunity to study and visualize the evolution of PCA from the very earliest symptomatic stages.

Heterogeneity of visual deficits in posterior cortical atrophy

Posterior cortical atrophy (PCA) is a progressive neurodegenerative condition most commonly associated with the histopathological features of Alzheimer's disease (AD). Individuals with PCA exhibit a progressive decline in higher visual object and space processing and other posterior cortical functions. However the extent to which these visuoperceptual and visuospatial processing problems are underpinned by basic visual processing deficits is unknown because elementary visual processes (e.g. form, colour, motion, location) have not been examined previously. This study investigated visual deficits in 21 patients with a clinical diagnosis of probable Alzheimer's disease (AD) who also met behavioural criteria for PCA. Basic visual processing skills were examined in detail, including assessments of form detection, form discrimination, form coherence, motion coherence, colour discrimination and point localisation. The relationship between these six basic visual processes was assessed, and their association with general cognitive function, episodic memory, dominant parietal function (calculation, spelling), space perception (dot counting, number location) and object perception (canonical and non-canonical view apperception) was investigated. 100% of participants showed impairment in at least one aspect of basic visual processing, but form, colour, motion and location processing were not uniformly affected (see Table). Higher order object and space perception deficits were associated with different patterns of basic visual impairment. However, with relevance to theories of network-based disease progression between non-contiguous brain areas in AD, basic visual processing did not correlate with performance on non-visual tasks (e.g. spelling, calculation) thought to depend upon cortical regions of equivalent proximity. Furthermore, the study revealed continuous rather than discrete differences in neuropsychological profile between three previously-claimed variant PCA syndromes held to reflect predominant dorsal, ventral and caudal tissue loss. The object and space perception problems commonly reported in PCA are underpinned by distinct and identifiable patterns of disruption to more basic visual processes associated with occipital lobe function. These behavioural data also complement neuroimaging findings from the same participants showing largely overlapping patterns of atrophy and cortical thinning, and indicate that different PCA phenotypes represent points within the space of continuous variation within the wider PCA syndrome.

The Scale of Functional Specialization within Human Prefrontal Cortex: Figure 1.

At what scale is it possible to observe consistent functional specialization within human prefrontal cortex (PFC), reproducible from one individual to the next? Some studies suggest gross functional divisions between large regions of PFC, but it is not known whether PFC exhibits specialization at the fine-grained scale known to differentiate posterior cortical functions. We used fMRI to confirm a three-way segregation of function between three regions of medial anterior PFC, each centered on coordinates within 15 mm of the other two. Naive participants performed three tasks based on earlier studies, and we investigated activity at regions defined by previous results. In each task, signal was significantly greater at the predicted region than the other two, just millimeters away. These results indicate reproducible functional specialization within PFC, at a much finer scale than previously demonstrated. Furthermore, these findings suggest that divergent results from previous studies may reflect the recruitment of functionally distinct regions and that "reverse inference" should be undertaken with caution.

Frontal-executive versus posterior-perceptual mental status deficits in early-onset dementias.

Compared to late-onset dementias, early-onset dementias (EODs) may have greater focal cognitive involvement with differences in frontal-executive compared to posterior-perceptual deficits. This study evaluated whether mental status screening based on this frontal-posterior axis can distinguish EODs. Twenty-three patients each with early-onset Alzheimer's disease (eAD), frontotemporal dementia (FTD), or subcortical ischemic vascular disease (SIVD), and 20 normal controls underwent the Frontal Assessment Battery (FAB) and the Perceptual Assessment Battery (PAB). Compared to controls, SIVD and FTD groups were impaired on the FAB whereas eAD and SIVD groups were impaired on the PAB. The FAB/PAB ratio further differentiated the groups (F(3,85) = 26.49, P < .001). For sensitivities and specificities of 93%, a cut-off score of 1.25 on the FAB/PAB distinguished eAD, and a cut-off of 0.83 distinguishing FTD. Although preliminary, this study indicates that mental status screening based on frontal versus posterior cortical functions may help clinicians diagnose EODs.

Clock Drawing Phenotypes in Community-Dwelling African Americans and Caucasians: Results from the University of Alabama at Birmingham Study of Aging

Background: Two dementia patterns have been described: ‘type 1’ dementia is characterized by executive function impairment and posterior cortical impairment, and ‘type 2’ dementia is characterized by executive impairment and relatively preserved posterior cortical function. The Executive Clock Drawing Task (CLOX) has been used to discriminate between type 1, type 2, and normal cognitive phenotypes. The aim of this study was to describe the prevalence of these phenotypes in community-dwelling African American and Caucasian elders. Methods: 433 African Americans and 477 Caucasians over the age of 65 were recruited. Executive function was assessed using CLOX1, a command-directed clock drawing task. Posterior cortical impairment was assessed using CLOX2, a clock copy task. CLOX scores were combined to estimate the prevalence of type 1 phenotype (those with poor CLOX1 and CLOX2 performance) versus type 2 phenotype (those with only poor CLOX1 performance). Results: 351 (39%) subjects had poor executive performance. Three hundred (33%) subjects had a type 1 phenotype and this pattern was 2.5 times more common among African Americans than Caucasians. One hundred and thirty-seven (15%) subjects had a type 2 phenotype with no significant difference between African Americans and Caucasians. African American ethnicity was independently associated with poor CLOX1 performance after adjusting for sociodemographic factors, posterior cortical function, and global cognition. CLOX2 performance was not associated with ethnicity. Conclusion: The prevalence of poor executive performance in community-dwelling elders is high. African Americans were more likely to have a type 1 phenotype and these ethnic differences were not explained by sociodemographic variables alone.

Differentiating Alzheimer’s disease from subcortical vascular dementia with the FAB test

The frontal assessment battery (FAB) test is a composite tool for assessing executive functions related to the frontal lobe. Neuropsychological and blood-flow studies indicate distinct patterns of deterioration of anterior and posterior cortical function in Alzheimer's disease (AD) and subcortical vascular dementia (VD) patients. We predict that the FAB score may be useful for discriminating VD from AD. To evaluate the clinical usefulness of the FAB test for differential diagnosis of AD and VD. We compared FAB scores in 25 patients with AD, 27 patients with VD, and 80 age-matched normal control subjects. The AD group was matched for age, education and MMSE score with the VD group. The subtest scores in FAB were also compared among the three groups. The FAB scores were significantly decreased in both the AD and VD groups compared to the control group, and the reduction were greater in the VD group. Among the FAB subtests, mental flexibility (phonological verbal fluency) was the only subtest that significantly discriminated VD from the other two groups. The FAB test can provide useful information for differentiating AD and VD at the bedside.

Cognitive impairment in remission in bipolar affective disorder

Although the traditional view of bipolar affective disorder is that the majority of patients have full remission between episodes, recent evidence suggests that residual cognitive deficits are present. The aim of this study was to determine whether memory and executive deficits were present in a well-defined clinically remitted group of patients. This was a case-control study of bipolar patients in remission (N = 18). Subjects had to fulfil stringent clinical criteria for inclusion into the study and had to have been in remission for at least 4 months. Subjects also had no history of substance dependence. The cognitive battery examined memory and executive function. Patients in excellent clinical remission and who reported good social adaptation showed imipairment on tests of visuospatial recognition memory. Accuracy on four tests of executive function was not impaired in patients in remission compared with controls, although response latency on these executive tests was still impaired. As our group and others have shown, patients with mania and unipolar depression show generalized impairment on tests of memory and executive function. In comparison, this study has demonstrated that patients in remission show a relatively specific impairment in memory with recovery of accuracy measures on executive function task. The increased response latency on the executive tasks suggests a possible small residual impairment. These findings suggest that in netIroanatomical terms, more posterior cortical function (temporal lobe) has not improved but there is at least some recovery of frontal lobe function in remission.

Implicit learning in psychotic patients

Implicit verbal learning of psychotic patients ( n = 59) and non-psychotic control patients ( n = 20) was studied using stem completion and association tasks in lexical and semantic priming paradigms. Performance on these tasks was contrasted with explicit memory on Rey's verbal learning test. Furthermore, correlations of these aspects of memory with positive and negative symptoms of psychosis were examined. Symptom ratings were based on an interview by a psychiatrist using the CPRS and SANS. As expected, the lexical and semantic priming effects in both patient groups were not significantly different, whereas the psychotic patients compared to the controls were impaired in explicit learning. None of the memory variables was significantly correlated with negative or positive symptoms. These findings are explained by the fact that priming effects, as opposed to explicit learning, depend on automatic memory processes, which do not require conscious effort. Moreover, the findings suggest the intactness of posterior cortical functions in psychotic patients.

Cognitive impairment in long-term benzodiazepine users.

In view of the very extensive and often prolonged use of benzodiazepines in therapeutic practice, this study was designed to investigate whether or not cognitive ability is impaired in long-term benzodiazepine users, and to determine the nature and extent of any deficit. Fifty patients currently taking benzodiazepines for at least one year, thirty-four who had stopped taking benzodiazepines, and a matched control group of subjects who had never taken benzodiazepines or who had taken benzodiazepines in the past for less than one year were administered a battery of neuropsychological tests designed to measure a wide range of cognitive functions. It was found that patients taking high doses of benzodiazepines for long periods of time perform poorly on tasks involving visual-spatial ability and sustained attention. This is consistent with deficits in posterior cortical cognitive function.