Inter-site and inter-scanner diffusion MRI data harmonization

We propose a novel method to harmonize diffusion MRI data acquired from multiple sites and scanners, which is imperative for joint analysis of the data to significantly increase sample size and statistical power of neuroimaging studies. Our method incorporates the following main novelties: i) we take into account the scanner-dependent spatial variability of the diffusion signal in different parts of the brain; ii) our method is independent of compartmental modeling of diffusion (e.g., tensor, and intra/extra cellular compartments) and the acquired signal itself is corrected for scanner related differences; and iii) inter-subject variability as measured by the coefficient of variation is maintained at each site. We represent the signal in a basis of spherical harmonics and compute several rotation invariant spherical harmonic features to estimate a region and tissue specific linear mapping between the signal from different sites (and scanners). We validate our method on diffusion data acquired from seven different sites (including two GE, three Philips, and two Siemens scanners) on a group of age-matched healthy subjects. Since the extracted rotation invariant spherical harmonic features depend on the accuracy of the brain parcellation provided by Freesurfer, we propose a feature based refinement of the original parcellation such that it better characterizes the anatomy and provides robust linear mappings to harmonize the dMRI data. We demonstrate the efficacy of our method by statistically comparing diffusion measures such as fractional anisotropy, mean diffusivity and generalized fractional anisotropy across multiple sites before and after data harmonization. We also show results using tract-based spatial statistics before and after harmonization for independent validation of the proposed methodology. Our experimental results demonstrate that, for nearly identical acquisition protocol across sites, scanner-specific differences can be accurately removed using the proposed method.

Cognitive effects of one season of head impacts in a cohort of collegiate contact sport athletes

OBJECTIVE

To determine whether exposure to repetitive head impacts over a single season negatively affects cognitive performance in collegiate contact sport athletes.

METHODS

This is a prospective cohort study at 3 Division I National Collegiate Athletic Association athletic programs. Participants were 214 Division I college varsity football and ice hockey players who wore instrumented helmets that recorded the acceleration-time history of the head following impact, and 45 noncontact sport athletes. All athletes were assessed prior to and shortly after the season with a cognitive screening battery (ImPACT) and a subgroup of athletes also were assessed with 7 measures from a neuropsychological test battery.

RESULTS

Few cognitive differences were found between the athlete groups at the preseason or postseason assessments. However, a higher percentage of the contact sport athletes performed more poorly than predicted postseason on a measure of new learning (California Verbal Learning Test) compared to the noncontact athletes (24% vs 3.6%; p < 0.006). On 2 postseason cognitive measures (ImPACT Reaction Time and Trails 4/B), poorer performance was significantly associated with higher scores on several head impact exposure metrics.

CONCLUSION

Repetitive head impacts over the course of a single season may negatively impact learning in some collegiate athletes. Further work is needed to assess whether such effects are short term or persistent.

Judgment in older adults: development and psychometric evaluation of the Test of Practical Judgment (TOP-J)

This article reports on the development and validation of a novel, objective test of judgment for use with older adults. The Test of Practical Judgment (TOP-J) is an open-ended measure that evaluates judgment related to safety, medical, social/ethical, and financial issues. Psychometric features were examined in a sample of 134 euthymic individuals with mild Alzheimer's disease (AD), amnestic mild cognitive impairment (MCI), or cognitive complaints but intact neuropsychological performance (CC), and demographically-matched healthy controls (HC). Measures of reliability were adequate to high, and TOP-J scores correlated with select measures of executive functioning, language, and memory. AD participants obtained impaired TOP-J scores relative to HCs, while MCI and CC participants showed an intermediate level of performance. Confirmatory factor analyses were consistent with a unidimensional structure. Results encourage further development of the TOP-J as an indicator of practical judgment skills in clinical and research settings. Longitudinal assessments are being performed to examine predictive validity of the TOP-J for cognitive progression in our clinical groups.

Regional brain atrophy in cognitively intact adults with a single APOE 4 allele

OBJECTIVE

To determine whether cognitively intact adults with the APOE epsilon3/epsilon4 genotype show reduced gray matter density on voxel-based morphometry (VBM) vs those homozygous for the epsilon3 allele.

METHODS

Participants were healthy, cognitively intact, right-handed adults, age 19 to 80, who completed genotyping, neuropsychological testing, and MRI. Forty-nine participants had the epsilon3/epsilon3 genotype and 27 had the epsilon3/epsilon4 genotype. Gray matter data were analyzed using the general linear model as implemented in the Statistical Parametric Mapping package, adjusting for age and sex.

RESULTS

The epsilon3/epsilon4 participants showed lower gray matter density than the epsilon3/epsilon3 participants in right medial temporal and bilateral frontotemporal regions as well as other areas. There were no regions in which epsilon3/epsilon4 participants showed higher gray matter density than epsilon3/epsilon3 participants.

CONCLUSIONS

Regionally reduced gray matter density is detectable in cognitively intact adults with a single copy of the APOE epsilon4 allele.

Older adults with cognitive complaints show brain atrophy similar to that of amnestic MCI

OBJECTIVE

To examine the neural basis of cognitive complaints in healthy older adults in the absence of memory impairment and to determine whether there are medial temporal lobe (MTL) gray matter (GM) changes as reported in Alzheimer disease (AD) and amnestic mild cognitive impairment (MCI).

METHODS

Participants were 40 euthymic individuals with cognitive complaints (CCs) who had normal neuropsychological test performance. The authors compared their structural brain MRI scans to those of 40 patients with amnestic MCI and 40 healthy controls (HCs) using voxel-based morphometry and hippocampal volume analysis.

RESULTS

The CC and MCI groups showed similar patterns of decreased GM relative to the HC group on whole brain analysis, with differences evident in the MTL, frontotemporal, and other neocortical regions. The degree of GM loss was associated with extent of both memory complaints and performance deficits. Manually segmented hippocampal volumes, adjusted for age and intracranial volume, were significantly reduced only in the MCI group, with the CC group showing an intermediate level.

CONCLUSIONS

Cognitive complaints in older adults may indicate underlying neurodegenerative changes even when unaccompanied by deficits on formal testing. The cognitive complaint group may represent a pre-mild cognitive impairment stage and may provide an earlier therapeutic opportunity than mild cognitive impairment. MRI analysis approaches incorporating signal intensity may have greater sensitivity in early preclinical stages than volumetric methods.

Performance of subjects with and without severe mental illness on a clinical test of problem solving

Severe mental illness is associated with impairments in executive functions, such as conceptual reasoning, planning, and strategic thinking all of which impact problem solving. The present study examined the utility of a novel assessment tool for problem solving, the Rapid Assessment of Problem Solving Test (RAPS) in persons with severe mental illness. Subjects were 47 outpatients with severe mental illness and an equal number healthy controls matched for age and gender. Results confirmed all hypotheses with respect to how subjects with severe mental illness would perform on the RAPS. Specifically, the severely mentally ill subjects (1) solved fewer problems on the RAPS, (2) when they did solve problems on the test, they did so far less efficiently than their healthy counterparts, and (3) the two groups differed markedly in the types of questions asked on the RAPS. The healthy control subjects tended to take a systematic, organized, but not always optimal approach to solving problems on the RAPS. The subjects with severe mental illness used some of the problem solving strategies of the healthy controls, but their performance was less consistent and tended to deteriorate when the complexity of the problem solving task increased. This was reflected by a high degree of guessing in lieu of asking constraint questions, particularly if a category-limited question was insufficient to continue the problem solving effort.

Brain activation patterns associated with working memory in relapsing-remitting MS

BACKGROUND

Patients with multiple sclerosis (MS) show changes in brain activation patterns during visual and motor tasks that include decreases in the typical local network for a function and increases in other brain regions.

OBJECTIVE

To determine whether brain activation patterns associated with working memory are affected by MS.

METHODS

Activation of working memory circuitry was examined using an fMRI n-back task in adults with mild relapsing-remitting MS (RRMS; n = 10) and demographically matched healthy controls (n = 10).

RESULTS

Group differences in brain activation emerged during both low- and high-demand conditions (p < 0.001). Overall, patients showed less activation than controls in core prefrontal and parietal regions of working memory circuitry, and greater activation in other regions within and beyond typical working memory circuitry, including bilateral medial frontal, cingulate, parietal, bilateral middle temporal, and occipital regions.

CONCLUSIONS

Relative to controls, patients with mild RRMS showed shifts in brain activation patterns within and beyond typical components of working memory circuitry.

Chronic deep brain stimulation for the treatment of tremor in multiple sclerosis: review and case reports

BACKGROUND

Deep brain stimulation (DBS) offers a non-ablative alternative to thalamotomy for the surgical treatment of medically refractory tremor in multiple sclerosis. However, relatively few outcomes have been reported.

OBJECTIVE

To provide a systematic review of the published cases of DBS use in multiple sclerosis and to present four additional patients.

METHODS

Quantitative and qualitative review of the published reports and description of a case series from one centre.

RESULTS

In the majority of reported cases (n=75), the surgical target for DBS implantation was the ventrointeromedial nucleus of the thalamus. Tremor reduction and improvement in daily functioning were achieved in most patients, with 87.7% experiencing at least some sustained improvement in tremor control postsurgery. Effects on daily functioning were less consistently assessed across studies; in papers reporting relevant data, 76.0% of patients experienced improvement in daily functioning. Adverse effects were similar to those reported for DBS in other patient populations.

CONCLUSIONS

Few of the studies reviewed used highly standardised quantitative outcome measures, and follow up periods were generally one year or less. Nonetheless, the data suggest that chronic DBS often produces improved tremor control in multiple sclerosis. Complete cessation of tremor is not necessarily achieved, there are cases in which tremor control decreases over time, and frequent reprogramming appears to be necessary.

Sex differences in semantic language processing: a functional MRI study

Predictions based on two models of sex differences in cerebral organization of language were compared by examining fMRI patterns of 10 females and 9 males during a semantic processing task. Both groups displayed activation of left inferior frontal gyrus (IFG), left superior temporal gyrus (STG), and cingulate. Females, but not males, showed bilateral IFG and STG activation. Further analyses revealed females had less diffuse left activation and greater right posterior temporal and insula region activation than males. Results support both an interhemispheric and an intrahemispheric model of sex differences in language, suggesting that the models may not be mutually exclusive.

Neuroimaging findings in mild traumatic brain injury

The role of neuroimaging in the diagnosis and management of mild traumatic brain injury (TBI) is evolving. In general, the structural imaging techniques play a role in acute diagnosis and management, while the functional imaging techniques show promise for clarification of pathophysiology, symptom genesis, and mechanisms of recovery. A wide array of neuropathological processes are involved in mild TBI including changes in bone (e.g., a skull fracture), tissue density and water content (edema), blood flow, white matter integrity and pathway connectivity (diffuse axonal injury), and subtle changes in the neuronal and extracellular biochemical milieu. No single imaging technique is capable of addressing all these processes. It is, therefore, important to be aware of the advantages and limitations of the various available imaging modalities. This paper selectively reviews the pertinent literature on the structural and functional imaging in mild TBI.

Differential working memory load effects after mild traumatic brain injury

The objective of this study was to explore the effects of increasing working memory (WM) processing load on previously observed abnormalities in activation of WM circuitry shortly after mild traumatic brain injury (MTBI). Brain activation patterns in response to increasing WM processing load (auditory n-back: 0-, 1-, 2-, and 3-back conditions) were assessed with fMRI in 18 MTBI patients within 1 month of their injury and in 12 healthy controls. Performance accuracy on these tasks was also measured. Brain activation patterns differed between MTBI patients and controls in response to increasing WM processing loads. Controls maintained their ability to increase activation in regions of WM circuitry with each increase in WM processing load. MTBI patients showed disproportionately increased activation during the moderate processing load condition, but very little increase in activation associated with the highest processing load condition. Task performance did not differ significantly between groups on any task condition. MTBI patients showed a different pattern of allocation of processing resources associated with a high processing load condition compared to healthy controls, despite similar task performance. This suggests that injury-related changes in ability to activate or modulate WM processing resources might underlie some of the memory complaints after MTBI.

Deep brain stimulation in neuropsychiatric disorders

Deep brain stimulation (DBS) of the ventral intermediate nucleus of the thalamus, subthalamic nucleus, and internal globus pallidus has been put forth as an alternative to surgical ablation for the treatment of movement disorders. In this paper, the authors discuss the history and putative physiologic mechanisms underlying DBS of these target regions. The authors then review empirical findings pertaining to the effects of DBS on neurological symptoms, cognitive functioning, and psychiatric symptoms in Parkinson's disease and essential tremor, the disorders for which the procedure has been most extensively applied. Finally, emerging and potential novel areas of application of DBS for the treatment of neuropsychiatric disorders and symptoms are discussed.

Specific frontal lobe subregions correlated with unawareness of illness in schizophrenia: a preliminary study

The authors examined the relationship between unawareness of illness and eight frontal lobe subregions in 15 patients with schizophrenia. Significant inverse correlations were seen between unawareness and bilateral middle frontal gyrus volume and between symptom misattribution and superior frontal gyrus volume.

Effects of retroactive and proactive interference on word list recall in schizophrenia

Schizophrenia spectrum patients (N = 143) and healthy controls (N = 160) were administered the Rey Auditory Verbal Learning Test (RAVLT) and tests of executive functioning to directly investigate the effects of proactive interference (PI) and retroactive interference (RI) on word list recall. It was hypothesized that by virtue of the predicted preferential association between executive functioning and RI (relative to PI), patients would demonstrate increased susceptibility to RI in their ability to recall word lists. Results indicated that patients show increased susceptibility to RI relative to PI. Furthermore, this difference appeared to be related to the frontally-mediated central executive functions that were preferentially associated with RI but not PI susceptibility.

Brain activation on fMRI and verbal memory ability: functional neuroanatomic correlates of CVLT performance

We have recently reported (Saykin et al., 1999b) selective activation of left medial temporal lobe structures during processing of novel compared to familiar words using functional magnetic resonance imaging (fMRI). The current study describes the relationship between a widely used clinical test of verbal learning, the California Verbal Learning Test (CVLT), and the previously reported fMRI activations. Thirteen right-handed healthy adult participants were studied with whole brain echo-planar fMRI while listening to novel and recently learned (familiar) words intermixed pseudorandomly in an event-related design. These participants were also tested with the CVLT. Scores for CVLT Trial 1 (immediate encoding of novel words) and recognition discriminability (recognition of familiar vs. novel words) were correlated with fMRI signal change during processing of novel versus familiar words using a covariance model implemented in SPM96. For the novel words analysis, voxels in the right anterior hippocampus correlated significantly with Trial 1 (r = .76 at the maxima). For the recognition analysis, a significant cluster of voxels was found in the right dorsolateral prefrontal cortex (r = .88 at the maxima). Our prior results of separable left medial temporal activation to novel and familiar words, together with results of the covariance analyses reported here, suggest that in addition to the left medial temporal lobe (MTL) regions that are engaged during novel and familiar word processing, the right hippocampus and right frontal lobe are also involved, particularly in those participants with better memory ability. This positive relationship between fMRI activation and CVLT performance suggests a role for these right hemisphere regions in successful memory processing of verbal material, perhaps reflecting more efficient encoding and retrieval strategies that facilitate memory.

Smaller brain size associated with unawareness of illness in patients with schizophrenia

OBJECTIVE

Although several neuropsychological studies have supported the notion of frontal and parietal lobe involvement in unawareness of illness in schizophrenia, neuroanatomic differences have not been examined.

METHOD

Thirty patients with schizophrenia spectrum disorder were rated by means of a structured interview assessing awareness of illness and performance on clinical rating scales. With 13 healthy comparison subjects, they underwent neuropsychological assessment and a scan using three-dimensional, spoiled gradient recall acquisition volumetric magnetic resonance imaging.

RESULTS

Patients who were relatively unaware of their illness had smaller brain and intracranial volumes (brain tissue plus CSF) than either aware patients or normal comparison subjects, who did not differ significantly from each other.

CONCLUSIONS

These findings suggest that unawareness of illness is an important phenomenological feature with neurological correlates that is seen in at least one subgroup of patients with schizophrenia.

Cognitive correlates of the negative, disorganized, and psychotic symptom dimensions of schizophrenia

Knowledge of the relationship between specific cognitive abnormalities and the clinical symptoms of schizophrenia could give insight into the nature of their underlying pathophysiology. Composite scores were generated for negative, disorganized, and psychotic symptom ratings in 134 patients with schizophrenia (DSM-IV criteria). Partial correlations (each composite corrected for the others) were computed with neuropsychological measures. Negative symptoms were related to poor performance on tests of verbal learning and memory, verbal fluency, visual memory, and visual-motor sequencing. Disorganized symptoms were correlated with lower verbal IQ and poor concept attainment. Psychotic symptoms had no significant relationship with cognitive deficit.

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.

Brain activation during working memory 1 month after mild traumatic brain injury: a functional MRI study

OBJECTIVE

To assess patterns of regional brain activation in response to varying working memory loads shortly after mild traumatic brain injury (MTBI).

BACKGROUND

Many individuals complain of memory difficulty shortly after MTBI. Memory performance in these individuals can be normal despite these complaints.

METHODS

Brain activation patterns in response to a working memory task (auditory n-back) were assessed with functional MRI in 12 MTBI patients within 1 month of their injury and in 11 healthy control subjects.

RESULTS

Brain activation patterns differed between MTBI patients and control subjects in response to increasing working memory processing loads. Maximum intensity projections of statistical parametric maps in control subjects showed bifrontal and biparietal activation in response to a low processing load, with little additional increase in activation associated with the high load task. MTBI patients showed some activation during the low processing load task but significantly increased activation during the high load condition, particularly in the right parietal and right dorsolateral frontal regions. Task performance did not differ significantly between groups.

CONCLUSION

MTBI patients differed from control subjects in activation pattern of working memory circuitry in response to different processing loads, despite similar task performance. This suggests that injury-related changes in ability to activate or to modulate working memory processing resources may underlie some of the memory complaints after MTBI.

Functional differentiation of medial temporal and frontal regions involved in processing novel and familiar words: an fMRI study

Results of recent functional magnetic resonance imaging (fMRI) studies of memory are not entirely consistent with lesion studies. Furthermore, although imaging probes have identified neural systems associated with processing novel visual episodic information, auditory verbal memory using a novel/familiar paradigm has not yet been examined. To address this gap, fMRI was used to compare the haemodynamic response when listening to recently learned and novel words. Sixteen healthy adults (6 male, 10 female) learned a 10-item word list to 100% criterion, approximately 1 h before functional scanning. During echo-planar imaging, subjects passively listened to a string of words presented at 6-s intervals. Previously learned words were interspersed pseudo-randomly between novel words. Mean scans corresponding to each word type were analysed with a random-effects model using statistical parametric mapping (SPM96). Familiar (learned) words activated the right prefrontal cortex, posterior left parahippocampal gyrus, left medial parietal cortex and right superior temporal gyrus. Novel words activated the anterior left hippocampal region. The results for the familiar words were similar to those found in other functional imaging studies of recognition and retrieval and implicate the right dorsolateral prefrontal and left posterior medial temporal lobe (MTL) regions. The results for novel words require replication, but are consistent with the substantial lesion and PET literature implicating the anterior MTL as a critical site for processing novel episodic information, presumably to permit encoding. Together, these results provide evidence for an anterior-posterior functional differentiation within the MTL in processing novel and familiar verbal information. The differentiation of MTL functions that was obtained is consistent with a large body of PET activation studies but is unique among fMRI studies, which to date have differed from results with PET. Further, the finding of left MTL lateralization is consistent with lesion-based material-specific models of memory.

Neuroanatomic substrates of semantic memory impairment in Alzheimer's disease: patterns of functional MRI activation

Impairment in semantic processing occurs early in Alzheimer's disease (AD) and differential impact on subtypes of semantic relations have been reported, yet there is little data on the neuroanatomic basis of these deficits. Patients with mild AD and healthy controls underwent 3 functional MRI auditory stimulation tasks requiring semantic or phonological decisions (match-mismatch) about word pairs (category-exemplar, category-function, pseudoword). Patients showed a significant performance deficit only on the exemplar task. On voxel-based fMRI activation analyses, controls showed a clear activation focus in the left superior temporal gyrus for the phonological task; patients showed additional foci in the left dorsolateral prefrontal and bilateral cingulate areas. On the semantic tasks, predominant activation foci were seen in the inferior and middle frontal gyrus (left greater than right) in both groups but patients showed additional activation suggesting compensatory recruitment of locally expanded foci and remote regions, for example, right frontal activation during the exemplar task. Covariance analyses indicated that exemplar task performance was strongly related to signal increase in bilateral medial prefrontal cortex. The authors conclude that fMRI can reveal similarities and differences in functional neuroanatomical processing of semantic and phonological information in mild AD compared to healthy elderly, and can help to bridge cognitive and neural investigations of the integrity of semantic networks in AD.

Neuropsychological correlates of methylphenidate treatment in adult ADHD with and without depression

The purpose of this study was to characterize the neuropsychological profiles of adult patients with attention deficit hyperactivity disorder (ADHD) alone and ADHD with active comorbid depression, and to evaluate changes in the neuropsychological profile in these two groups following a trial of methylphenidate. Forty patients with ADHD were classified into two groups based on their affective status resulting in a group of 21 patients with ADHD alone and 19 patients with ADHD and active comorbid symptoms of depression (ADHD-D). All subjects received a comprehensive neuropsychological evaluation including measures of cognitive, motor and affective functioning before and after treatment. Fifteen normal controls were also assessed at a yoked time interval. At baseline, both patient groups showed impairment in verbal memory, motor and processing speed, visual scanning, and auditory and visual distractibility. Following treatment, both patient groups showed improvement across all neuropsychological measures while controls remained relatively stable over time. Improvement in neuropsychological test performance was not related to gender, affective status or referral source. Patients with active comorbid symptoms of depression show a similar neuropsychological profile and appear equally likely to benefit from methylphenidate intervention as patients with ADHD alone.

Hippocampal volume reduction in schizophrenia as assessed by magnetic resonance imaging: a meta-analytic study

BACKGROUND

Although many quantitative magnetic resonance imaging studies have found significant volume reductions in the hippocampi of patients with schizophrenia compared with those of normal control subjects, others have not. Therefore, the issue of hippocampal volume differences associated with schizophrenia remains in question.

METHODS

Two meta-analyses were conducted to reduce the potential effects of sampling error and methodological differences in data acquisition and analysis. Eighteen studies with a total patient number of 522 and a total control number of 426 met the initial selection criteria.

RESULTS

Meta-analysis 1 yielded mean effect sizes of 0.37 (P<.001) for the left hippocampus and 0.39 (P<.001) for the right, corresponding to a bilateral reduction of 4%. Meta-analysis 2 indicated that the inclusion of the amygdala in the region of interest significantly increased effect sizes across studies (effect size for the left hippocampus and amygdala, 0.67; for the right, 0.72), whereas variables such as illness duration, total slice width, magnet strength, the use of the intracranial volume as a covariate, measurement reliability, and study quality did not. No laterality differences were observed in these data.

CONCLUSIONS

Schizophrenia is associated with a bilateral volumetric reduction of the hippocampus and probably of the amygdala as well. These findings reinforce the importance of the medial temporal region in schizophrenia and are consistent with frequently reported memory deficits in these patients. Future quantitative magnetic resonance imaging studies evaluating the hippocampal volume should measure the hippocampus and amygdala separately and compare the volumetric reduction in these structures to that observed in other gray matter areas.

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

The purpose of the present study was to investigate putative neural substrates of long-term (delayed) memory in schizophrenia and young healthy controls. Ten "low" and 10 "high" memory patients were selected from a large sample of DSM-III-R diagnosed schizophrenia spectrum patients, based on composite verbal and nonverbal delayed recall memory scores. Ten "low" and 9 "high" memory individuals were also selected from a larger sample of young healthy controls. Magnetic resonance imaging scans were acquired on a 1.5-T GE Signa scanner using a SPGR sequence (repetition time = 24 msec, echo time = 5 msec). Hippocampal volumes were computed from manual tracings (intraclass correlation = .96), and temporal lobe and whole brain tissue volumes were obtained using a semiautomated technique. In both the patient sample and controls, there was no significant relationship between delayed memory ability and hippocampal, temporal lobe, or whole brain volume. The integration of results from this study, and from studies on normal aging and Alzheimer's disease, supports a model suggesting that hippocampal size may be an indicator of long-term memory ability, but only when hippocampal measures reflect aging and degenerative hippocampal atrophy. If the hippocampal measures reflect individual differences in hippocampal size prior to the onset of hippocampal atrophy, then hippocampal size does not appear to predict long-term memory ability.

Antithrombotic, procoagulant, and fibrinolytic mechanisms in cerebral circulation: implications for brain injury and protection

Maintaining a delicate balance among anticoagulant, procoagulant, and fibrinolytic pathways in the cerebral microcirculation is of major importance for normal cerebral blood flow. Under physiological conditions and in the absence of provocative stimuli, the anticoagulant and fibrinolytic pathways prevail over procoagulant mechanisms. Blood clotting is essential to minimize bleeding and to achieve hemostasis; however, excessive clotting contributes to thrombosis and may predispose the brain to infarction and ischemic stroke. Conversely, excessive bleeding due to enhanced anticoagulatory and fibrinolytic mechanisms could predispose the brain to hemorrhagic stroke. Recent studies in the author's laboratory indicate that brain capillary endothelium in vivo produces thrombomodulin (TM), a key cofactor in the TM-protein C system that is of major biological significance to the antithrombotic properties of the blood-brain barrier (BBB). The BBB endothelium also expresses tissue plasminogen activator (tPA), a key protein in fibrinolysis, and its rapid inhibitor, plasminogen activator inhibitor (PAI-1). The procoagulant tissue factor is normally dormant at the BBB. There is a vast body of clinical evidence to document the importance of hemostasis in the pathophysiology of brain injury. In particular, functional changes caused by major stroke risk factors in the TM-protein C, tPA/PAI-1, and tissue factor systems at the BBB may result in large and debilitating infarctions following an ischemic insult. Thus, correcting this hemostatic imbalance could ameliorate drastic CBF reductions at the time of ischemic insult, ultimately resulting in brain protection. Delineation of the molecular mechanisms of BBB-mediated hemostasis will likely contribute to future stroke prevention efforts and brain protection strategies.

Temporal lobe epilepsy and performance on the Wisconsin Card Sorting Test

The replicability of previous evidence for differential performance between left and right temporal lobe epileptic patients on the Wisconsin Card Sorting Test (WCST) was evaluated in a new sample of candidates for focal resection. Many subjects obtained high scores on indices of perseveration, which are commonly thought to reflect frontal dysfunction, but there were no differences in performance between patients with language-dominant and nondominant temporal foci. The findings confirm existing evidence that performance decrements on the WCST can be associated with epileptic foci and focal lesions in nonfrontal brain lesions.

Soft signs and neuropsychological performance in schizophrenia

OBJECTIVE

Both neuropsychological impairment and neurological soft signs have been documented in at least a subset of patients with schizophrenia. The purpose of the present study was to examine the relationship between soft signs and neuropsychological performance in patients with schizophrenia in order to address the issue of whether soft signs are related to global or more selective cognitive impairment.

METHOD

Patients with a DSM-III-R diagnosis of schizophrenia (N=176) were given a standardized neuropsychological battery and underwent a neurological examination. The study group was dichotomized on the basis of presence or absence of neurological soft signs.

RESULTS

Patients with neurological soft signs (N=68) demonstrated significantly poorer performance on neuropsychological tasks that assessed timed motor speed and motor coordination (e.g., finger tapping, the Purdue Pegboard task, and part B of the Trail Making Test). These findings continued to be significant even after lifetime medication exposure, extrapyramidal symptoms, and abnormal involuntary movements were used as covariates.

CONCLUSIONS

These findings support the notion that soft signs are a manifestation of a localizable behavioral deficit of the systems that are involved in motor speed, coordination, and sequencing and are not indicative of global cognitive impairment. The specific deficit in motor abilities is consistent with the types of neurological soft signs that are most frequently reported and suggests involvement of frontal/subcortical circuitry in schizophrenia.

Automatic atlas-based volume estimation of human brain regions from MR images

OBJECTIVE

MRI offers many opportunities for noninvasive in vivo measurement of structure-function relationships in the human brain. Although automated methods are now available for whole-brain measurements, an efficient and valid automatic method for volume estimation of subregions such as the frontal or temporal lobes is still needed.

MATERIALS AND METHODS

We adapted the Talairach atlas to the study of brain subregions. We supplemented the atlas with additional boxes to include the cerebellum. We assigned all the boxes to 1 of 12 regions of interest (ROIs) (frontal, parietal, temporal, and occipital lobes, cerebellum, and subcortical regions on right and left sides of the brain). Using T1-weighted MR scans collected with an SPGR sequence (slice thickness = 1.5 mm), we manually traced these ROIs and produced volume estimates. We then transformed the scans into Talairach space and compared the volumes produced by the two methods ("traced" versus "automatic"). The traced measurements were considered to be the "gold standard" against which the automatic measurements were compared.

RESULTS

The automatic method was found to produce measurements that were nearly identical to the traced method. We compared absolute measurements of volume produced by the two methods, as well as the sensitivity and specificity of the automatic method. We also compared the measurements of cerebral blood flow obtained through [15O]H2O PET studies in a sample of nine subjects. Absolute measurements of volume produced by the two methods were very similar, and the sensitivity and specificity of the automatic method were found to be high for all regions. The flow values were also found to be very similar by both methods.

CONCLUSION

The automatic atlas-based method for measuring the volume of brain subregions produces results that are similar to manual techniques. The method is rapid, efficient, unbiased, and not subject to the problems of rater drift or potentially poor interrater reliability that plague manual methods. Consequently, this method may be very useful for the study of structure-function relationships in the human brain.

Clinical utility of the CERAD word list memory test

The word list memory test from the Consortium to establish a registry for Alzheimer's disease (CERAD) neuropsychological battery (Morris et al. 1989) was administered to 230 psychiatric outpatients. Performance of a selected, age-matched psychiatric group and normal controls was compared using an ANCOVA design with education as a covariate. Results indicated that controls performed better than psychiatric patients on most learning and recall indices. The exception to this was the savings index that has been found to be sensitive to the effects of progressive dementias. The current data are compared and integrated with published CERAD data for Alzheimer's disease patients. The CERAD list memory test is recommended as a brief, efficient, and sensitive memory measure that can be used with a range of difficult patients.

The effects of chronic desmethylimipramine on entorhinal cortical kindling in rats

Chronic pretreatment of rats with desmethylimipramine (DMI) significantly slowed the rate of seizure generalization elicited by repeated electrical stimulation of the entorhinal cortex (kindling). An identical drug regimen administered to either fully kindled rats or rats partially kindled to early motor seizure stages failed to significantly alter kindling profiles in these animals. Under these latter conditions, in fact, there was a tendency for chronic DMI to exacerbate seizure activity. The effect of chronic DMI pretreatment to slow the development of kindled seizure generalization did not occur if a two-week delay was interposed between the end of drug treatment and the beginning of kindling trials. Results suggest that the retardation of entorhinal cortical kindling rate is dependent on DMI-induced CNS adaptations which recover within two weeks following treatment, and this effect is dependent on the presence of DMI-induced adaptations in a naive (unkindled) nervous system. Alterations of either the kindled state or the adaptational state produced by chronic drug eliminate the slowing of seizure generalization observed when both conditions are present.

Meal patterns following changes in procurement cost for rats with fornix transection

The purpose of the present study was to explore the effects of a varied procurement cost on the foraging behavior of rats with fornix transection. An operant analog of foraging requirements was used to examine the feeding patterns of the animals under free feeding, low procurement cost (FR5), and high procurement cost (FR80) situations, in an environment with minimal sensory distraction. It was found that animals with fornix transection did not differ from control rats in general consumption. Both groups were also able to adapt their feeding behavior to the varied procurement cost. As the procurement cost increased, the number of meals consumed decreased while the meal duration increased. The meal patterns themselves were different for the fornix transected animals and the control group. Animals with fornix transections ate more meals over the course of a day than did control animals; their meals were of a longer duration, and their intermeal intervals were shorter than those of control animals. During the course of a meal, the rats with fornix transections took a larger number of breaks, during which they drank, explored, or engaged in activities other than eating. These differences in the feeding patterns were seen across all procurement cost levels. The data support the possibility of hippocampal involvement in behavioral organization or sequencing.