Lack of an association between delayed memory and hippocampal and temporal lobe size in patients with schizophrenia and healthy controls

Brain Morphological Characteristics of Cognitive Subgroups of Schizophrenia-Spectrum Disorders and Bipolar Disorder: A Systematic Review with Narrative Synthesis

Despite a growing body of research, there is yet to be a cohesive synthesis of studies examining differences in brain morphology according to patterns of cognitive function among both schizophrenia-spectrum disorder (SSD) and bipolar disorder (BD) individuals. We aimed to provide a systematic overview of the morphological differences-inclusive of grey and white matter volume, cortical thickness, and cortical surface area-between cognitive subgroups of these disorders and healthy controls, and between cognitive subgroups themselves. An initial search of PubMed and Scopus databases resulted in 1486 articles of which 20 met inclusion criteria and were reviewed in detail. The findings of this review do not provide strong evidence that cognitive subgroups of SSD or BD map to unique patterns of brain morphology. There is preliminary evidence to suggest that reductions in cortical thickness may be more strongly associated with cognitive impairment, whilst volumetric deficits may be largely tied to the presence of disease.

Brain morphology does not clearly map to cognition in individuals on the bipolar-schizophrenia-spectrum: a cross-diagnostic study of cognitive subgroups

BACKGROUND

Characterisation of brain morphological features common to cognitively similar individuals with bipolar disorder (BD) and schizophrenia spectrum disorders (SSD) may be key to understanding their shared neurobiological deficits. In the current study we examined whether three previously characterised cross-diagnostic cognitive subgroups differed among themselves and in comparison to healthy controls across measures of brain morphology.

METHOD

T1-weighted structural magnetic resonance imaging scans were obtained for 143 individuals; 65 healthy controls and 78 patients (SSD, n = 40; BD I, n = 38) classified into three cross-diagnostic cognitive subgroups: Globally Impaired (n = 24), Selectively Impaired (n = 32), and Superior/Near-Normal (n = 22). Cognitive subgroups were compared to each other and healthy controls on three separate analyses investigating (1) global, (2) regional, and (3) vertex-wise comparisons of brain volume, thickness, and surface area.

RESULTS

No significant subgroup differences were evident in global measures of brain morphology. In region of interest analyses, the Selectively Impaired subgroup had greater right accumbens volume than those Superior/Near-Normal subgroup and healthy controls, and the Superior/Near-Normal subgroup had reduced volume of the left entorhinal region compared to all other groups. In vertex-wise comparisons, the Globally Impaired subgroup had greater right precentral volume than the Selectively Impaired subgroup, and thicker cortex in the postcentral region relative to the Superior/Near-Normal subgroup.

LIMITATIONS

Exploration of medication effects was limited in our data.

CONCLUSIONS

Although some differences were evident in this sample, generally cross-diagnostic cognitive subgroups of individuals with SSD and BD did not appear to be clearly distinguished by patterns in brain morphology.

Characterising the structure of cognitive heterogeneity in schizophrenia spectrum disorders. A systematic review and narrative synthesis

The aim of the present review was to systematically summarise our current understanding of the structure of the cognitive heterogeneity that exists within schizophrenia spectrum disorder (SSD). Fifty-two relevant studies were identified from January 1980 to March 2019 that investigated cognitive subgroups within SSD. Twenty-five studies employed classification criteria based on current neuropsychological function, 14 studies employed various data-driven subgrouping methodologies and 13 studies investigated putative cognitive symptom trajectories. Despite considerable methodological variability, three distinct cognitive subgroups reliability emerged; a relatively intact cognitive subgroup characterised by high cognitive performance, an intermediate cognitive subgroup defined by mixed or moderate levels of cognitive function/dysfunction and a globally impaired subgroup characterised by severe cognitive deficits. Whilst preliminary evidence suggests that these subgroups may have further investigative relevance in and of themselves, additional research is required and discussed. A set of reporting guidelines are also presented to overcome the methodological inconsistencies identified in the reviewed literature.

Hippocampal integrity and neurocognition in first-episode schizophrenia: a multidimensional study

OBJECTIVES

Impairments in memory and executive function are key components of schizophrenia. These disturbances have been linked to several subcortical and cortical networks. For example, anatomical and functional changes in the hippocampus have been linked to deficits in these cognitive domains. However, the association between hippocampal morphometry, neurochemistry and function is controversial. Therefore, we aimed to investigate the relationship between hippocampal anomalies and their functional relevance.

METHODS

Fifty-seven first-episode schizophrenia patients (FE-SZ) and 61 healthy control subjects (HC) participated in this study. Hippocampal volumes were investigated using structural magnetic resonance imaging (sMRI) and hippocampal neurochemistry was determined using proton magnetic resonance spectroscopy (1H MRS). Verbal memory was used as a hippocampus-dependent cognitive task whereas working memory and cognitive flexibility assessed frontal lobe function.

RESULTS

FE-SZ presented smaller volumes of the left hippocampus, with a significant correlation between left hippocampal volume and verbal memory performance (immediate recall). There was also an inverse correlation between neurochemical ratios (NAA/Cho and Cho/Cr) and verbal memory (delayed recognition). Tests of cognitive flexibility and working memory were not correlated with MRI and 1H MRS values. Compared to HC, FE-SZ demonstrated reduced performance in all of the assessed neurocognitive domains.

CONCLUSIONS

These results point to a relationship between verbal memory and hippocampal integrity in schizophrenia patients which might be independent from deficits in other memory domains. Disturbed verbal memory functions in FE-SZ might be linked specifically to hippocampal function.

Hippocampal volume reduction and autobiographical memory deficits in chronic schizophrenia

Although autobiographical memory (AM) deficits and hippocampal changes are frequently found in schizophrenia, their actual association remained yet to be established. AM performance and hippocampal volume were examined in 33 older, chronic schizophrenic patients and 21 healthy volunteers matched for age, gender and education. Psychopathological symptoms and additional neuropsychological parameters were assessed by using appropriate rating scales; magnetic resonance imaging (MRI) 3-T data were analyzed via an automated region-of-interest procedure. When compared with the control subjects, patients showed significantly decreased left anterior and posterior hippocampal volumes. Episodic but not semantic AM performance was significantly lower in the patients than in the healthy controls. Both episodic and semantic AM deficits were significantly correlated with volume of the left hippocampus in the patient group. In contrast, deficits in verbal memory, working memory and remote semantic memory observed in the patients did not relate to hippocampal volume. Our findings indicate that AM deficits in chronic schizophrenia are associated with hippocampal volume reductions and underline the importance of this pathology in schizophrenia.

Different characteristics of cognitive impairment in elderly schizophrenia and Alzheimer's disease in the mild cognitive impairment stage

We compared indices of the revised version of the Wechsler Memory Scale (WMS-R) and scaled scores of the five subtests of the revised version of the Wechsler Adult Intelligence Scale (WAIS-R) in 30 elderly schizophrenia (ES) patients and 25 Alzheimer's disease (AD) patients in the amnestic mild cognitive impairment (aMCI) stage (AD-aMCI). In the WMS-R, attention/concentration was rated lower and delayed recall was rated higher in ES than in AD-aMCI, although general memory was comparable in the two groups. In WAIS-R, digit symbol substitution, similarity, picture completion, and block design scores were significantly lower in ES than in AD-aMCI, but the information scores were comparable between the two groups. Delayed recall and forgetfulness were less impaired, and attention, working memory and executive function were more impaired in ES than in AD-aMCI. These results should help clinicians to distinguish ES combined with AD-aMCI from ES alone.

Comparison of manual and automated determination of hippocampal volumes in MCI and early AD

MRI-based hippocampal volume analysis has been extensively employed given its potential as a biomarker for brain disorders such as Alzheimer's disease (AD), and accurate and efficient determination of hippocampal volumes from brain images is still a challenging issue. We compared an automated method, FreeSurfer (V4), with a published manual protocol for the determination of hippocampal volumes from T1-weighted MRI scans. Our study included MRI data from 125 older adult subjects: healthy controls with no significant cognitive complaints or deficits (HC, n=38), euthymic individuals with cognitive complaints (CC, n=39) but intact neuropsychological performance, and patients with amnestic mild cognitive impairment (MCI, n=37) or a clinical diagnosis of probable AD (AD, n=11). Pearson correlations and intraclass correlation coefficients (ICCs) were calculated to evaluate the relationship between results of the manual tracing and FreeSurfer methods and to estimate their agreement. Results indicated that these two methods derived highly correlated results with strong agreement. After controlling for the age, sex and intracranial volume in statistical group analysis, both the manual tracing and FreeSurfer methods yield similar patterns: both the MCI group and the AD group showed hippocampal volume reduction compared to both the HC group and the CC group, and the HC and CC groups did not differ. These comparisons suggest that FreeSurfer has the potential to be used in automated determination of hippocampal volumes for large-scale MCI/AD-related MRI studies, where manual methods are inefficient or not feasible.

Comparing prefrontal gray and white matter contributions to intelligence and decision making in schizophrenia and healthy controls

The authors examined the relationship between neuropsychological performance and MRI of the orbital frontal cortex (OFC) and diffusion tensor imaging (DTI) of the cingulum bundle (CB) within groups of patients with schizophrenia and healthy subjects. The authors analyzed data from subjects, who had participated in prior MRI, DTI, and neuropsychological studies (Nakamura et al., 2008; Nestor et al., 2008). In comparison to healthy subjects, patients showed the expected reductions across CB fractional anisotropy (white matter) and OFC gray matter volume as well as lower neuropsychological scores. In addition, in comparison to healthy subjects, patients showed a very different pattern of functional-anatomical correlates. For patients, CB white matter but not OFC gray matter correlated with various aspects of intelligence, including general abilities and working memory. For controls, OFC gray matter but not CB white matter correlated with scores on tests of intelligence and decision making. These results point to the potentially important role of CB white matter in the neuropsychological disturbance in schizophrenia.

Hippocampus volume and episodic memory in schizophrenia

Previous studies of schizophrenia have suggested a linkage between neuropsychological (NP) deficits and hippocampus abnormality. The relationship between hippocampus volume and NP functioning was investigated in 24 patients with chronic schizophrenia and 24 matched healthy controls. Overall intracranial, white and gray matter, and anterior (AH) and posterior (PH) hippocampus volumes were assessed from magnetic resonance images (MRI). NP domains of IQ, attention, and executive function were also evaluated with respect to volumetric measures. It was hypothesized that AH and PH volumes and episodic memory scores would be positively associated in controls and that the schizophrenia group would depart from this normative pattern. NP functioning was impaired overall and AH volume was smaller in the schizophrenia group. In the controls, the hippocampus-memory relationships involved AH and PH, and correlations were significant for verbal memory measures. In the schizophrenia group, positive correlations were constrained to PH. Negative correlations emerged between AH and verbal and visual memory measures. For both groups, cortical volume negatively correlated with age, but a negative correlation between age and hippocampus volume was found only in the schizophrenia group. In this sample of adults with schizophrenia, atypical relationships between regional hippocampus volumes and episodic memory ability were found, as was an atypical negative association between hippocampus volume and age.

Left posterior hippocampal density reduction using VBM and stereological MRI procedures in schizophrenia

Structural deficits in the hippocampus have been implicated in the pathophysiology of schizophrenia. However the role played by structural impairments in the hippocampus in the memory deficits of schizophrenic patients remains unclear. Magnetic resonance imaging was used in this study to investigate left, right, anterior and posterior hippocampal volume and density in 28 schizophrenic patients and 33 normal controls. Voxel-based morphometry analysis showed that schizophrenics had significantly lower density in the right and posterior hippocampus than controls. MRI stereological analysis revealed significant differences in left posterior hippocampus than controls. MRI stereological analysis revealed significant differences in anterior and posterior on both sides, with the left posterior region predominating. Schizophrenics showed significant impairments in verbal learning and long term retention (P<0.001). The correlation analyses between hippocampal density and memory variables yielded a significant correlation between forgetting and density of the anterior hippocampus. These findings support the hypothesis of a regional atrophy within the hippocampus in schizophrenic patients.

Reduced anterior hippocampal formation volume in hyponatremic schizophrenic patients

Diminished hippocampal volume occurs in the anterior segment of some schizophrenic patients, and in the posterior segment in others. The significance of hippocampal pathology in general and these segmental differences in specific is not known. Several lines of evidence suggest anterior hippocampal pathology underlies the life-threatening hyponatremia seen in a subgroup of patients with schizophrenia; therefore our goal was to determine if this region was preferentially diminished in hyponatremic patients. We studied seven polydipsic hyponatremic, ten polydipsic normonatremic, and nine nonpolydipsic normonatremic schizophrenic inpatients, as well as 12 healthy controls. All underwent structural scanning on a high resolution (3.0 T) magnetic resonance imaging (MRI) scanner. Hippocampal formation, amygdala, and third ventricle volumes were manually traced in each subject. The hippocampus was divided at the posterior extent of the uncus, and all structural volumes were corrected for whole brain volume and other significant recognized factors (i.e., age, gender, height, parental education). Despite being overhydrated, anterior hippocampal formation volume was diminished in those with polydipsia and hyponatremia relative to each of the other three groups. Third ventricle volume was larger in this group than in healthy controls but similar to the two patient groups. Posterior hippocampal and amygdala volumes did not differ between groups. Other potential confounds (e.g., water imbalance) either had no effect or accentuated these differences. We conclude the anterior hippocampal formation is smaller in hyponatremic schizophrenic patients, thereby linking an important and objective clinical feature of schizophrenia to a neural pathway that can be investigated in animal models. The findings strengthen the hypothesis that anterior hippocampal formation pathology disrupts functional connectivity with other limbic structures in schizophrenia.

Neuropsychological functioning and brain structure in schizophrenia

Cognitive deficits are core features of schizophrenia that are already evident at early phases of the illness. The study of specific relationships between cognition and brain structure might provide valuable clues about neural basis of schizophrenia and its phenomenology. The aim of this article was to review the most consistent findings of the studies exploring the relationships between cognitive deficits and brain anomalies in schizophrenia. Besides several important methodological shortcomings to bear in mind before drawing any consistent conclusion from the revised literature, we have attempted to systematically summarize these findings. Thus, this review has revealed that whole brain volume tends to positively correlate with a range of cognitive domains in healthy volunteers and female patients. An association between prefrontal morphological characteristics and general inability to control behaviour seems to be present in schizophrenia patients. Parahippocampal volume is related to semantic cognitive functions. Thalamic anomalies have been associated with executive deficits specifically in patients. Available evidence on the relationship between cognitive functions and cerebellar structure is still contradictory. Nonetheless, a larger cerebellum appears to be associated with higher IQ in controls and in female patients. Enlarged ventricles, including lateral and third ventricles, are associated with deficits in attention, executive and premorbid cognitive functioning in patients. Several of these reported findings seem to be counterintuitive according to neural basis of cognitive functioning drawn from animal, lesion, and functional imaging investigations. Therefore, there is still a great need for more methodologically stringent investigations that would help in the advance of our understanding of the cognition/brain structure relationships in schizophrenia.

Hippocampal volume and shape analysis in an older adult population

This report presents a manual segmentation protocol for the hippocampus that yields a reliable and comprehensive measure of volume, a goal that has proven difficult with prior methods. Key features of this method include alignment of the images in the long axis of the hippocampus and the use of a three-dimensional image visualization function to disambiguate anterior and posterior hippocampal boundaries. We describe procedures for hippocampal volumetry and shape analysis, provide inter- and intra-rater reliability data, and examine correlates of hippocampal volume in a sample of healthy older adults. Participants were 40 healthy older adults with no significant cognitive complaints, no evidence of mild cognitive impairment or dementia, and no other neurological or psychiatric disorder. Using a 1.5 T GE Signa scanner, three-dimensional spoiled gradient recalled acquisition in a steady state (SPGR) sequences were acquired for each participant. Images were resampled into 1 mm isotropic voxels, and realigned along the interhemispheric fissure in the axial and coronal planes, and the long axis of the hippocampus in the sagittal plane. Using the BRAINS program (Andreasen et al., 1993), the boundaries of the hippocampus were visualized in the three orthogonal views, and boundary demarcations were transferred to the coronal plane for tracing. Hippocampal volumes were calculated after adjusting for intracranial volume (ICV). Intra- and inter-rater reliabilities, measured using the intraclass correlation coefficient, exceeded .94 for both the left and right hippocampus. Total ICV-adjusted volumes were 3.48 (+/-0.43) cc for the left hippocampus and 3.68 (+/-0.42) for the right. There were no significant hippocampal volume differences between males and females (p > .05). In addition to providing a comprehensive volumetric measurement of the hippocampus, the refinements included in our tracing protocol permit analysis of changes in hippocampal shape. Shape analyses may yield novel information about structural brain changes in aging and dementia that are not reflected in volumetric measurements alone. These and other novel directions in research on hippocampal function and dysfunction will be facilitated by the use of reliable, comprehensive, and consistent segmentation and measurement methods.

Regional cortical thickness matters in recall after months more than minutes

The aim of this study was to determine the role of regional cortical thickness in recall of verbal material over an extended time period. MRI scans of healthy adults of varying ages were obtained. Two scans were averaged per person to achieve high spatial resolution, and a semi-automated method for continuous measurement of thickness across the entire cortical mantle was employed. Verbal memory tests assessing recall after 5 min, 30 min, and a mean interval of 83 days were administered. A general linear model (GLM) of the effects of thickness at each vertex on the different memory indices was computed, controlling for gender, age, IQ, and intracranial volume. These analyses were repeated with hippocampal volume as an additional variable to be controlled for, to assess to which extent effects of cortical thickness were independent of hippocampal size. Minute effects of cortical thickness were observed with regard to shorter time intervals (5 and 30 min). However, even when controlling for the effects of hippocampal volume, higher recall across months was associated with thicker cortex of distinct areas including parts of the gyrus rectus, the middle frontal gyrus, the parieto-occipital sulcus and the lingual gyrus of both hemispheres. In addition, hemisphere-specific associations were found in parts of the right temporal and parietal lobe as well as parts of the left precuneus. This supports a unique and critical role of the thickness of distinct cortical areas in recall after months, more than after minutes.

Neuropsychological sequelae of bacterial and viral meningitis

Survivors of meningitis often complain about neurological and neuropsychological consequences. In this study, the extent of these sequelae was quantified and correlated to MRI findings. Neurological, neuropsychological and neuroradiological examinations were performed with adult patients younger than 70 years, 1-12 years after recovery from bacterial meningitis (BM; n = 59), or from viral meningitis (VM; n = 59). Patients with other potential causes for neuropsychological deficits (e.g. alcoholism) were carefully excluded. Patients were compared to 30 healthy subjects adjusted for age, gender and length of school education. With the exception of attention functions, both patient groups showed more frequently pathological results than the control group for all domains examined. Applying an overall cognitive sum score, patients after BM did not differ significantly in their performance from patients after VM. Separate analyses of various cognitive domains, however, revealed a higher rate of persistent disturbances in short-term and working memory after BM than after VM. Moreover, patients after BM exhibited greater impairment of executive functions. Associative learning of verbal material was also reduced. These deficits could not be ascribed to impaired alertness functions or decreased motivation in BM patients. Applying a logistic regression model, the neuropsychological outcome was related to the neurological outcome. Patients with a Glasgow Outcome Scale (GOS) of <5 had more frequently impaired test results for non-verbal learning and memory. GOS was also correlated with performance in executive functions. Brain volume was lower and ventricular volume was higher in the bacterial than in the VM group, and cerebral volume and the amount of white matter lesions of patients after BM were negatively correlated with short-term and working memory. In conclusion, patients after both BM and VM with favourable outcome showed affected learning and memory functions. More patients after BM than after VM displayed pathological short-term and working memory. BM resulted in poorer performance in executive functions, language, short-term memory and verbal learning/memory tests. As a result of neurological and neuropsychological sequelae, BM with a GOS > or = 4 led to decreased activities of daily living but only a minority of patients were disabled in a way that social functions were affected. The extent of neuropsychological sequelae of BM might have been overestimated in earlier studies which often had not been controlled for comorbidity factors such as alcoholism.

The Primacy of Cognition in Schizophrenia

Cognitive tasks and concepts are used increasingly in schizophrenia science and treatment. Recent meta-analyses show that across a spectrum of research domains only cognitive measures distinguish a majority of schizophrenia patients from healthy people. Average effect sizes derived from common clinical tests of attention, memory, language, and reasoning are twice as large as those obtained in structural magnetic resonance imaging and positron emission tomography studies. Chronic stress, genes, brain disturbances, task structure, gender, and sociocultural background may all enhance the sensitivity of cognitive performance to schizophrenia. At the same time, disease heterogeneity and the presence of endophenotypes and subtypes within the patient population may place upper limits on the strength of any specific cognitive finding. Schizophrenia is a complex biobehavioral disorder that manifests itself primarily in cognition.

MR-based in vivo hippocampal volumetrics: 1. Review of methodologies currently employed

The advance of neuroimaging techniques has resulted in a burgeoning of studies reporting abnormalities in brain structure and function in a number of neuropsychiatric disorders. Measurement of hippocampal volume has developed as a useful tool in the study of neuropsychiatric disorders. We reviewed the literature and selected all English-language, human subject, data-driven papers on hippocampal volumetry, yielding a database of 423 records. From this database, the methodology of all original manual tracing protocols were studied. These protocols differed in a number of important factors for accurate hippocampal volume determination including magnetic field strength, the number of slices assessed and the thickness of slices, hippocampal orientation correction, volumetric correction, software used, inter-rater reliability, and anatomical boundaries of the hippocampus. The findings are discussed in relation to optimizing determination of hippocampal volume.

MR-based in vivo hippocampal volumetrics: 2. Findings in neuropsychiatric disorders

Magnetic resonance imaging (MRI) has opened a new window to the brain. Measuring hippocampal volume with MRI has provided important information about several neuropsychiatric disorders. We reviewed the literature and selected all English-language, human subject, data-driven papers on hippocampal volumetry, yielding a database of 423 records. Smaller hippocampal volumes have been reported in epilepsy, Alzheimer's disease, dementia, mild cognitive impairment, the aged, traumatic brain injury, cardiac arrest, Parkinson's disease, Huntington's disease, Cushing's disease, herpes simplex encephalitis, Turner's syndrome, Down's syndrome, survivors of low birth weight, schizophrenia, major depression, posttraumatic stress disorder, chronic alcoholism, borderline personality disorder, obsessive-compulsive disorder, and antisocial personality disorder. Significantly larger hippocampal volumes have been correlated with autism and children with fragile X syndrome. Preservation of hippocampal volume has been reported in congenital hyperplasia, children with fetal alcohol syndrome, anorexia nervosa, attention-deficit and hyperactivity disorder, bipolar disorder, and panic disorder. Possible mechanisms of hippocampal volume loss in neuropsychiatric disorders are discussed.

Relationship between hippocampal volume and memory ability in healthy individuals across the lifespan: review and meta-analysis

Poor memory ability and small hippocampal volume measurements in magnetic resonance images co-occur in neurological patients. Numerous studies have examined the relationship between memory performance and hippocampal volumes in participants without neurological or psychiatric disorders, with widely varying results. Three hypotheses about volume-memory relationships in the normal human brain are discussed: "bigger is always better", a neuropsychological view that volume decreases due to normal aging are accompanied by memory decline, and a developmental perspective that regressive events in development may result in negative correlations between hippocampal volume and memory ability. Meta-analysis of results from 33 studies led to little support for the bigger-is-better hypothesis. A negative relationship between hippocampal volume and memory (smaller is better) was significant for studies with children, adolescents, and young adults. For studies with older adults, the most striking observation was extreme variability: the evidence for a positive relationship between hippocampal size and episodic memory ability in older adults was surprisingly weak. Some of the variability in results from older adults was associated with statistical methods of normalizing for age and head size, which are discussed.

Anterior hippocampal volume reduction in male patients with schizophrenia

Quantitative high resolution magnetic resonance imaging (MRI) was utilized to measure anterior, posterior, and total hippocampal volumes in 27 male patients with chronic schizophrenia and 24 male controls. To optimize measurement techniques, hippocampal volumes were: (1) acquired with 1.4-mm slices; (2) excluded with the amygdala; (3) normalized for position; and (4) corrected for total intracranial volume (ICV). The results of a linear mixed effects regression analysis, which made it possible to analyze total anterior and total posterior hippocampal volumes separately, indicated that the anterior hippocampus was significantly smaller in the schizophrenic group relative to the control group. There were no significant group differences with respect to posterior hippocampal volumes, and no significant correlations between hippocampal volumes and illness duration. A significant lateralized asymmetry was also noted in both groups with the right hippocampal volume being larger than the left. These preliminary findings support a significant anterior hippocampal volume reduction in men with schizophrenia as well as a similar hippocampal volume asymmetry in both male controls and schizophrenics.

Working and long-term memory deficits in schizophrenia: is there a common prefrontal mechanism?

This study tested the hypothesis that dorsolateral prefrontal cortex deficits contribute to both working memory and long-term memory disturbances in schizophrenia. It also examined whether such deficits were more severe for verbal than nonverbal stimuli. Functional magnetic resonance imaging was used to assess cortical activation during performance of verbal and nonverbal versions of a working memory task and both encoding and recognition tasks in 38 individuals with schizophrenia and 48 healthy controls. Performance of both working memory and long-term memory tasks revealed disturbed dorsolateral prefrontal cortex activation in schizophrenia, although medial temporal deficits were also present. Some evidence was found for more severe cognitive and functional deficits with verbal than nonverbal stimuli, although these results were mixed.

Amygdala-hippocampal volume and verbal memory in first-degree relatives of schizophrenic patients

Verbal memory deficits have been related to reduced volume of medial temporal structures in several neurological and psychiatric populations, including schizophrenic patients. Impairments in verbal memory have been proposed to be a marker of risk for schizophrenia. Recently, relatives of schizophrenic patients have been reported to have reduced volume of the amygdala-hippocampal complex. In this study, we evaluate the possibility that amygdala-hippocampal volume reductions may constitute one neural substrate of verbal memory deficits in first-degree relatives. Subjects were 20 healthy first-degree relatives of schizophrenic patients and 14 demographically similar controls. Verbal memory was assessed with the Logical Memory Test. Subjects were scanned with high-resolution MRI and the images were transformed into Talairach space. Volumes of interest were amygdala-anterior hippocampus and posterior hippocampus. Relatives of schizophrenic patients had intact immediate verbal memory but significantly poorer delayed verbal memory than controls. Relatives also had significantly reduced amygdala-anterior hippocampus volumes. Across all subjects, delayed verbal memory was significantly correlated with amygdala-anterior hippocampus volume. The magnitude of the correlation did not differ between the groups. These data provide an empirical link between memory performance and volumetric abnormalities in the amygdala-hippocampal complex in the relatives of schizophrenic patients.

A review of MRI findings in schizophrenia

After more than 100 years of research, the neuropathology of schizophrenia remains unknown and this is despite the fact that both Kraepelin (1919/1971: Kraepelin, E., 1919/1971. Dementia praecox. Churchill Livingston Inc., New York) and Bleuler (1911/1950: Bleuler, E., 1911/1950. Dementia praecox or the group of schizophrenias. International Universities Press, New York), who first described 'dementia praecox' and the 'schizophrenias', were convinced that schizophrenia would ultimately be linked to an organic brain disorder. Alzheimer (1897: Alzheimer, A., 1897. Beitrage zur pathologischen anatomie der hirnrinde und zur anatomischen grundlage einiger psychosen. Monatsschrift fur Psychiarie und Neurologie. 2, 82-120) was the first to investigate the neuropathology of schizophrenia, though he went on to study more tractable brain diseases. The results of subsequent neuropathological studies were disappointing because of conflicting findings. Research interest thus waned and did not flourish again until 1976, following the pivotal computer assisted tomography (CT) finding of lateral ventricular enlargement in schizophrenia by Johnstone and colleagues. Since that time significant progress has been made in brain imaging, particularly with the advent of magnetic resonance imaging (MRI), beginning with the first MRI study of schizophrenia by Smith and coworkers in 1984 (Smith, R.C., Calderon, M., Ravichandran, G.K., et al. (1984). Nuclear magnetic resonance in schizophrenia: A preliminary study. Psychiatry Res. 12, 137-147). MR in vivo imaging of the brain now confirms brain abnormalities in schizophrenia. The 193 peer reviewed MRI studies reported in the current review span the period from 1988 to August, 2000. This 12 year period has witnessed a burgeoning of MRI studies and has led to more definitive findings of brain abnormalities in schizophrenia than any other time period in the history of schizophrenia research. Such progress in defining the neuropathology of schizophrenia is largely due to advances in in vivo MRI techniques. These advances have now led to the identification of a number of brain abnormalities in schizophrenia. Some of these abnormalities confirm earlier post-mortem findings, and most are small and subtle, rather than large, thus necessitating more advanced and accurate measurement tools. These findings include ventricular enlargement (80% of studies reviewed) and third ventricle enlargement (73% of studies reviewed). There is also preferential involvement of medial temporal lobe structures (74% of studies reviewed), which include the amygdala, hippocampus, and parahippocampal gyrus, and neocortical temporal lobe regions (superior temporal gyrus) (100% of studies reviewed). When gray and white matter of superior temporal gyrus was combined, 67% of studies reported abnormalities. There was also moderate evidence for frontal lobe abnormalities (59% of studies reviewed), particularly prefrontal gray matter and orbitofrontal regions. Similarly, there was moderate evidence for parietal lobe abnormalities (60% of studies reviewed), particularly of the inferior parietal lobule which includes both supramarginal and angular gyri. Additionally, there was strong to moderate evidence for subcortical abnormalities (i.e. cavum septi pellucidi-92% of studies reviewed, basal ganglia-68% of studies reviewed, corpus callosum-63% of studies reviewed, and thalamus-42% of studies reviewed), but more equivocal evidence for cerebellar abnormalities (31% of studies reviewed). The timing of such abnormalities has not yet been determined, although many are evident when a patient first becomes symptomatic. There is, however, also evidence that a subset of brain abnormalities may change over the course of the illness. The most parsimonious explanation is that some brain abnormalities are neurodevelopmental in origin but unfold later in development, thus setting the stage for the development of the symptoms of schizophrenia. Or there may be additional factors, such as stress or neurotoxicity, that occur during adolescence or early adulthood and are necessary for the development of schizophrenia, and may be associated with neurodegenerative changes. Importantly, as several different brain regions are involved in the neuropathology of schizophrenia, new models need to be developed and tested that explain neural circuitry abnormalities effecting brain regions not necessarily structurally proximal to each other but nonetheless functionally interrelated. (ABSTRACT TRUNCATED)

Depth of lesion model in children and adolescents with moderate to severe traumatic brain injury: use of SPGR MRI to predict severity and outcome

OBJECTIVES

The utility of a depth of lesion classification using an SPGR MRI sequence in children with moderate to severe traumatic brain injury (TBI) was examined. Clinical and depth of lesion classification measures of TBI severity were used to predict neurological and functional outcome after TBI.

METHODS

One hundred and six children, aged 4 to 19, with moderate to severe TBI admitted to a rehabilitation unit had an SPGR MRI sequence obtained 3 months afterTBI. Acquired images were analyzed for location, number, and size of lesions. The Glasgow coma scale (GCS) was the clinical indicator of severity. The deepest lesion present was used for depth of lesion classification. Speed of injury was inferred from the type of injury. The disability rating scale at the time of discharge from the rehabilitation unit (DRS1) and at 1 year follow up (DRS2) were functional outcome measures.

RESULTS

The depth of lesion classification was significantly correlated with GCS severity, number of lesions, and both functional measures, DRS1 and DRS2. This result was more robust for time 1, probably due to the greater number of psychosocial factors impacting on functioning at time 2. Lesion volume was not correlated with the depth of lesion model. In multivariate models, depth of lesion was most predictive of DRS1, whereas GCS was most predictive of DRS2.

CONCLUSIONS

A depth of lesion classification of TBI severity may have clinical utility in predicting functional outcome in children and adolescents with moderate to severe TBI.

Cognitive functioning, cortisol release, and symptom severity in patients with schizophrenia

BACKGROUND

There is substantial evidence of dysregulation of cortisol secretion, hippocampal abnormalities, and memory deficits in schizophrenia and other psychotic disorders. Research also suggests that cortisol secretion augments dopaminergic activity, which may result in increased symptom expression in this clinical population.

METHODS

We examined the relations among cortisol release, cognitive performance, and psychotic symptomatology. Subjects were 18 adults with schizophrenia or schizoaffective disorder, seven with a nonpsychotic psychiatric disorder, and 15 normal control subjects. Tests of memory and executive function were administered. Cortisol was assayed from multiple saliva samples.

RESULTS

Findings indicated the following: 1) patients with psychotic disorders scored below the comparison groups on the cognitive measures; 2) for the entire sample, cortisol levels were inversely correlated with performance on memory and frontal tasks; and 3) among patients, cortisol levels were positively correlated with ratings of positive, disorganized, and overall symptom severity, but not with negative symptoms.

CONCLUSIONS

The present results suggest that abnormalities in the hypothalamic-pituitary-adrenal axis and hippocampal systems play a role in observed cognitive deficits across populations. Among psychotic patients, elevated cortisol secretion is linked with greater symptom severity.

Evidence for the involvement of the hippocampus in the pathophysiology of schizophrenia

The hippocampus, a medial temporal lobe structure, is often considered to play an important role in the pathophysiology of schizophrenia. Recent developments of neuroimaging and molecular postmortem techniques have significantly increased our ability to study the role of discrete brain regions in the pathophysiology of schizophrenia. This article describes animal models, structural, histological, molecular biology, and neuropsychological evidence for the involvement of the hippocampus in the pathophysiology of schizophrenia. The major findings in schizophrenic patients are decreased volumes, hypometabolism, and cytoarchitectural abnormalities which are more robust on the left hippocampus, as well as verbal memory impairment. It is yet to be determined whether these changes are neurodevelopmental or neurodegenerative in nature. Overall, these findings indicate that there are subtle changes in the hippocampus of schizophrenic patients. More comprehensive and focused hippocampal research in schizophrenia is required to elucidate the contribution of this intriguing brain structure to the pathophysiology of schizophrenia.

Evidence of a smaller left hippocampus and left temporal horn in both patients with first episode schizophrenia and normal control subjects

Findings from cerebral magnetic resonance imaging (MRI) studies in schizophrenia indicating temporal lobe involvement have been inconsistent and controversial. In a prospective study, we quantified the volumes of temporal lobe structures in 20 male patients with first episode schizophrenia (FES; mean+/-S.D.=27.4+/-4. 8 years) and 20 healthy age-matched male control subjects (27.7+/-3. 1 years). Measurements were performed on contiguous 2.2-mm coronal MRI slices, which included, as well as the temporal lobe, the amygdala, the hippocampal formation, and the temporal horn of the lateral ventricle. The definition of the borders of the structures relied on measurement guidelines derived from mutual comparisons of MRI and histological data. The definition of the hippocampus-amygdala interface was also validated in a correlated triplanar display. We did not detect any significant volume reductions of the measured structures in the FES group, as compared with healthy control subjects, on either side. Comparisons within groups, however, revealed that in both the patients and the healthy volunteers the hippocampal formations showed a significant right-sided bias (+9%, P=0.004, in the FES group; +12%, P=0.0003 in the control subjects). A significant volume difference in favor of the right hemisphere was also observed in the temporal horns of the lateral ventricles (+17%, P=0.02 in the patients with FES; +34%, P=0. 003, in the control group). There was only a nonsignificant trend for a larger temporal horn on the left side in patients with schizophrenia as compared with the control subjects. Our findings do not indicate a loss or reversal of the normal volume asymmetry pattern in the FES group.

Hippocampal pathology in schizophrenia: magnetic resonance imaging and spectroscopy studies

The hippocampus is a site of previously reported structural and functional abnormalities in schizophrenia. We used magnetic resonance imaging (MRI) and proton magnetic resonance spectroscopy (MRS) to measure gray matter volumes, the neuronal marker N-acetylaspartate (NAA), and the combination of glutamate (Glu), glutamine (Gln), and gamma-aminobutyric acid (GABA), designated Glx. Measurements were obtained of the medial temporal lobe, centered on the hippocampus, in 10 male patients with schizophrenia (3 neuroleptic-medicated and 7 medication-free), and 10 matched normal volunteers. MRI volumetric measurements and MRS data obtained with short echo time (TE=20 ms) one-dimensional STEAM chemical shift imaging (CSI) on a GE 1.5 Tesla Signa system were analyzed. A laterality index ¿(L-R)/(L+R) was generated from the ratio of Glx to choline-containing compounds (Cho) to test asymmetry changes. Reliability of the MRS measures was assessed with five test-retest studies of healthy volunteers and showed coefficients of variation (CV) in the range of 36-44% for the MRS ratios and standard deviations (S.D.) of 0.15-0.17 for the laterality indices. The Glx/Cho laterality index showed a relative right-sided excess in this region in the patients (-0.23+/-0.20) compared to the controls (+0.06+/-0.20), which was not confounded by tissue composition or placement variability of the MRS voxels. Hippocampal volume deficit and asymmetry were not significant, and other MRS measures showed no differences between patients and controls. The preliminary finding of a lateralized abnormality in Glx is consistent with postmortem findings of asymmetric neurochemical temporal lobe abnormalities in schizophrenia.

The relationship between fMRI activation and cerebral atrophy: comparison of normal aging and alzheimer disease

Functional MRI has recently been used to examine activation associated with aging and dementia, yet little is known regarding the effect of cerebral atrophy on fMRI signal. The purpose of this study was to examine the relationship between measures of global and regionally specific atrophy and fMRI activation in normal aging and in Alzheimer disease (AD). Two groups of subjects were studied with echoplanar imaging and quantitative structural volumetry: healthy controls spanning a broad age and atrophy range (n = 16) and patients with mild AD (n = 8). Results from a semantic task previously found to activate left inferior frontal (LIFG) and left superior temporal (LSTG) gyri were analyzed. The correlations between clusters of activation in the LIFG and LSTG and measures of local atrophy in the LIFG and LSTG regions were evaluated. For control subjects, there was no significant correlation between activation and regional or total brain atrophy (for LIFG r = -0.03, NS; for LSTG r = 0.20, NS). In contrast, for AD patients, there was a significant positive correlation between atrophy and activation in LIFG (r = 0.70, P = 0.05) but not LSTG (r = 0.00, NS). These results suggest that activation of language regions and atrophy within those regions may be independent among healthy adults spanning a broad age and atrophy range. However, in AD, a relationship exists in the LIFG that may reflect compensatory recruitment of cortical units or disease-specific changes in the hemodynamic response.

Is there a negative correlation between explicit memory and hippocampal volume?

The aim of this research was to study the relationship between explicit memory and hippocampal volume. Seventy healthy adults were administered one implicit memory test and one explicit memory (EM) test and underwent magnetic resonance imaging. The major finding was a negative correlation between the EM test and the right hippocampus/brain volume ratio (t = -0.25, P = 0.03) and the left hippocampus/brain volume ratio (t = -0.27, P = 0.02). This finding is not consistent with pathologic findings, which tend to show a relationship between decrease in memory performance and hippocampal atrophy. This discrepancy is discussed.

Reduced hippocampal N-acetylaspartate without volume loss in schizophrenia

Quantitative magnetic resonance imaging (MRI) can measure total gray matter volume but cannot discriminate between neurons and glia. Proton magnetic resonance spectroscopic imaging (1H MRSI) measures N-acetylaspartate (NAA) which is a selective marker of neuronal loss or neuronal dysfunction. The objective of this study was to obtain quantitative measures of hippocampal volume and hippocampal NAA to determine if there was evidence for hippocampal neuronal dysfunction or neuronal loss in schizophrenia. Quantitative MRI and 1H MRSI was performed on the right and left hippocampal regions in 23 chronic schizophrenic patients and 18 control subjects. Relative to the control group, the patients with schizophrenia demonstrated no change in hippocampal volumes bilaterally, but significantly decreased NAA in the hippocampal regions bilaterally. There was also no correlation between hippocampal volumes and NAA in either the schizophrenics or controls. These findings suggest that: (1) hippocampal NAA may be a more sensitive measure of neuronal loss than volumetric measurements; and (2) reduced hippocampal NAA may be measuring neuronal dysfunction or damage rather than neuronal loss in this sample of schizophrenics.