Identifying canonical and replicable multi-scale intrinsic connectivity networks in 100k+ resting-state fMRI datasets

Despite the known benefits of data-driven approaches, the lack of approaches for identifying functional neuroimaging patterns that capture both individual variations and inter-subject correspondence limits the clinical utility of rsfMRI and its application to single-subject analyses. Here, using rsfMRI data from over 100k individuals across private and public datasets, we identify replicable multi-spatial-scale canonical intrinsic connectivity network (ICN) templates via the use of multi-model-order independent component analysis (ICA). We also study the feasibility of estimating subject-specific ICNs via spatially constrained ICA. The results show that the subject-level ICN estimations vary as a function of the ICN itself, the data length, and the spatial resolution. In general, large-scale ICNs require less data to achieve specific levels of (within- and between-subject) spatial similarity with their templates. Importantly, increasing data length can reduce an ICN's subject-level specificity, suggesting longer scans may not always be desirable. We also find a positive linear relationship between data length and spatial smoothness (possibly due to averaging over intrinsic dynamics), suggesting studies examining optimized data length should consider spatial smoothness. Finally, consistency in spatial similarity between ICNs estimated using the full data and subsets across different data lengths suggests lower within-subject spatial similarity in shorter data is not wholly defined by lower reliability in ICN estimates, but may be an indication of meaningful brain dynamics which average out as data length increases.

A method for estimating and characterizing explicitly nonlinear dynamic functional network connectivity in resting-state fMRI data

The past 10 years have seen an explosion of approaches that focus on the study of time-resolved change in functional connectivity (FC). FC characterization among networks at a whole-brain level is frequently termed functional network connectivity (FNC). Time-resolved or dynamic functional network connectivity (dFNC) focuses on the estimation of transient, recurring, whole-brain patterns of FNC. While most approaches in this area have attempted to capture dynamic linear correlation, we are particularly interested in whether explicitly nonlinear relationships, above and beyond linear, are present and contain unique information. This study thus proposes an approach to assess explicitly nonlinear dynamic functional network connectivity (EN dFNC) derived from the relationship among independent component analysis time courses. Linear relationships were removed at each time point to evaluate, typically ignored, explicitly nonlinear dFNC using normalized mutual information (NMI). Simulations showed the proposed method estimated explicitly nonlinearity over time, even within relatively short windows of data. We then, applied our approach on 151 schizophrenia patients, and 163 healthy controls fMRI data and found three unique, highly structured, mostly long-range, functional states that also showed significant group differences. In particular, explicitly nonlinear relationships tend to be more widespread than linear ones. Results also highlighted a state with long range connections to the visual domain, which were significantly reduced in schizophrenia. Overall, this work suggests that quantifying EN dFNC may provide a complementary and potentially valuable tool for studying brain function by exposing relevant variation that is typically ignored.

Moving beyond the 'CAP' of the Iceberg: Intrinsic connectivity networks in fMRI are continuously engaging and overlapping

Resting-state functional magnetic resonance imaging is currently the mainstay of functional neuroimaging and has allowed researchers to identify intrinsic connectivity networks (aka functional networks) at different spatial scales. However, little is known about the temporal profiles of these networks and whether it is best to model them as continuous phenomena in both space and time or, rather, as a set of temporally discrete events. Both categories have been supported by series of studies with promising findings. However, a critical question is whether focusing only on time points presumed to contain isolated neural events and disregarding the rest of the data is missing important information, potentially leading to misleading conclusions. In this work, we argue that brain networks identified within the spontaneous blood oxygenation level-dependent (BOLD) signal are not limited to temporally sparse burst moments and that these event present time points (EPTs) contain valuable but incomplete information about the underlying functional patterns. We focus on the default mode and show evidence that is consistent with its continuous presence in the BOLD signal, including during the event absent time points (EATs), i.e., time points that exhibit minimum activity and are the least likely to contain an event. Moreover, our findings suggest that EPTs may not contain all the available information about their corresponding networks. We observe distinct default mode connectivity patterns obtained from all time points (AllTPs), EPTs, and EATs. We show evidence of robust relationships with schizophrenia symptoms that are both common and unique to each of the sets of time points (AllTPs, EPTs, EATs), likely related to transient patterns of connectivity. Together, these findings indicate the importance of leveraging the full temporal data in functional studies, including those using event-detection approaches.

Targeting location relates to treatment response in active but not sham rTMS stimulation

Background:

Precise targeting of brain functional networks is believed critical for treatment efficacy of rTMS (repetitive pulse transcranial magnetic stimulation) in treatment resistant major depression.

Objective:

To use imaging data from a “failed” clinical trial of rTMS in Veterans to test whether treatment response was associated with rTMS coil location in active but not sham stimulation, and compare fMRI functional connectivity between those stimulation locations.

Methods:

An imaging substudy of 49 Veterans (mean age, 56 years; range, 27e78 years; 39 male) from a randomized, sham-controlled, double-blinded clinical trial of rTMS treatment, grouping participants by clinical response, followed by group comparisons of treatment locations identified by individualized fiducial markers on structural MRI and resting state fMRI derived networks.

Results:

The average stimulation location for responders versus nonresponders differed in the active but not in the sham condition (P = .02). The average responder location derived from the active condition showed significant negative functional connectivity with the subgenual cingulate (P < .001) while the nonresponder location did not (P = .17), a finding replicated in independent cohorts of 84 depressed and 35 neurotypical participants. The responder and nonresponder stimulation locations evoked different seed based networks (FDR corrected clusters, all P < .03), revealing additional brain regions related to rTMS treatment outcome.

Conclusion:

These results provide evidence from a randomized controlled trial that clinical response to rTMS is related to accuracy in targeting the region within DLPFC that is negatively correlated with subgenual cingulate. These results support the validity of a neuro-functionally informed rTMS therapy target in Veterans.

Persistent negative symptoms in youth at clinical high risk for psychosis: A longitudinal study

BACKGROUND

Severity of negative symptoms has been associated with poor functioning, cognitive deficits, and defeatist beliefs in schizophrenia patients. However, one area that remains understudied is persistent negative symptoms (PNS). Negative symptoms, including PNS, have been observed in those at clinical high-risk (CHR) for psychosis. The aim of this study was to determine if PNS were associated with functioning, neurocognition, and defeatist beliefs in a CHR sample.

METHOD

CHR participants (n = 764) were recruited for the North American Prodrome Longitudinal Study. Negative symptoms were rated on the Scale of Psychosis-risk Symptoms. Generalized linear mixed models for repeated measures were used to examine changes over time between and within groups (PNS vs non-PNS).

RESULTS

The PNS group (n = 67) had significant deficits in functioning at baseline, 6, 12, 18, and 24-months compared to the non-PNS group (n = 673). Functioning improved over time in the non-PNS group, while functioning in the PNS group remained relatively stable and poor over a two-year period. A consistent trend emerged demonstrating higher defeatist beliefs in the PNS group; however, this result was lost when controlling for persistent depressive symptoms. There were no significant differences between the groups on neurocognition, social cognition, and transition to psychosis.

CONCLUSIONS

PNS exist in youth at CHR for psychosis, resulting in significant and persistent functional impairment, which remains when controlling for persistent depressive symptoms. PNS remain even in CHR youth who do not transition to psychosis. Thus, PNS may represent an unmet therapeutic need in CHR populations for which there are currently no effective treatments.

Resting-state thalamic dysconnectivity in schizophrenia and relationships with symptoms

BACKGROUND

Schizophrenia (SZ) is a severe neuropsychiatric disorder associated with disrupted connectivity within the thalamic-cortico-cerebellar network. Resting-state functional connectivity studies have reported thalamic hypoconnectivity with the cerebellum and prefrontal cortex as well as thalamic hyperconnectivity with sensory cortical regions in SZ patients compared with healthy comparison participants (HCs). However, fundamental questions remain regarding the clinical significance of these connectivity abnormalities.

METHOD

Resting state seed-based functional connectivity was used to investigate thalamus to whole brain connectivity using multi-site data including 183 SZ patients and 178 matched HCs. Statistical significance was based on a voxel-level FWE-corrected height threshold of p < 0.001. The relationships between positive and negative symptoms of SZ and regions of the brain demonstrating group differences in thalamic connectivity were examined.

RESULTS

HC and SZ participants both demonstrated widespread positive connectivity between the thalamus and cortical regions. Compared with HCs, SZ patients had reduced thalamic connectivity with bilateral cerebellum and anterior cingulate cortex. In contrast, SZ patients had greater thalamic connectivity with multiple sensory-motor regions, including bilateral pre- and post-central gyrus, middle/inferior occipital gyrus, and middle/superior temporal gyrus. Thalamus to middle temporal gyrus connectivity was positively correlated with hallucinations and delusions, while thalamus to cerebellar connectivity was negatively correlated with delusions and bizarre behavior.

CONCLUSIONS

Thalamic hyperconnectivity with sensory regions and hypoconnectivity with cerebellar regions in combination with their relationship to clinical features of SZ suggest that thalamic dysconnectivity may be a core neurobiological feature of SZ that underpins positive symptoms.

Decreased hemispheric connectivity and decreased intra- and inter- hemisphere asymmetry of resting state functional network connectivity in schizophrenia

Many studies have shown that schizophrenia patients have aberrant functional network connectivity (FNC) among brain regions, suggesting schizophrenia manifests with significantly diminished (in majority of the cases) connectivity. Schizophrenia is also associated with a lack of hemispheric lateralization. Hoptman et al. (2012) reported lower inter-hemispheric connectivity in schizophrenia patients compared to controls using voxel-mirrored homotopic connectivity. In this study, we merge these two points of views together using a group independent component analysis (gICA)-based approach to generate hemisphere-specific timecourses and calculate intra-hemisphere and inter-hemisphere FNC on a resting state fMRI dataset consisting of age- and gender-balanced 151 schizophrenia patients and 163 healthy controls. We analyzed the group differences between patients and healthy controls in each type of FNC measures along with age and gender effects. The results reveal that FNC in schizophrenia patients shows less hemispheric asymmetry compared to that of the healthy controls. We also found a decrease in connectivity in all FNC types such as intra-left (L_FNC), intra-right (R_FNC) and inter-hemisphere (Inter_FNC) in the schizophrenia patients relative to healthy controls, but general patterns of connectivity were preserved in patients. Analyses of age and gender effects yielded results similar to those reported in whole brain FNC studies.

Widespread white matter microstructural differences in schizophrenia across 4322 individuals: results from the ENIGMA Schizophrenia DTI Working Group

The regional distribution of white matter (WM) abnormalities in schizophrenia remains poorly understood, and reported disease effects on the brain vary widely between studies. In an effort to identify commonalities across studies, we perform what we believe is the first ever large-scale coordinated study of WM microstructural differences in schizophrenia. Our analysis consisted of 2359 healthy controls and 1963 schizophrenia patients from 29 independent international studies; we harmonized the processing and statistical analyses of diffusion tensor imaging (DTI) data across sites and meta-analyzed effects across studies. Significant reductions in fractional anisotropy (FA) in schizophrenia patients were widespread, and detected in 20 of 25 regions of interest within a WM skeleton representing all major WM fasciculi. Effect sizes varied by region, peaking at (d=0.42) for the entire WM skeleton, driven more by peripheral areas as opposed to the core WM where regions of interest were defined. The anterior corona radiata (d=0.40) and corpus callosum (d=0.39), specifically its body (d=0.39) and genu (d=0.37), showed greatest effects. Significant decreases, to lesser degrees, were observed in almost all regions analyzed. Larger effect sizes were observed for FA than diffusivity measures; significantly higher mean and radial diffusivity was observed for schizophrenia patients compared with controls. No significant effects of age at onset of schizophrenia or medication dosage were detected. As the largest coordinated analysis of WM differences in a psychiatric disorder to date, the present study provides a robust profile of widespread WM abnormalities in schizophrenia patients worldwide. Interactive three-dimensional visualization of the results is available at www.enigma-viewer.org.

Intranasal oxytocin increases facial expressivity, but not ratings of trustworthiness, in patients with schizophrenia and healthy controls

BACKGROUND

Blunted facial affect is a common negative symptom of schizophrenia. Additionally, assessing the trustworthiness of faces is a social cognitive ability that is impaired in schizophrenia. Currently available pharmacological agents are ineffective at improving either of these symptoms, despite their clinical significance. The hypothalamic neuropeptide oxytocin has multiple prosocial effects when administered intranasally to healthy individuals and shows promise in decreasing negative symptoms and enhancing social cognition in schizophrenia. Although two small studies have investigated oxytocin's effects on ratings of facial trustworthiness in schizophrenia, its effects on facial expressivity have not been investigated in any population.

METHOD

We investigated the effects of oxytocin on facial emotional expressivity while participants performed a facial trustworthiness rating task in 33 individuals with schizophrenia and 35 age-matched healthy controls using a double-blind, placebo-controlled, cross-over design. Participants rated the trustworthiness of presented faces interspersed with emotionally evocative photographs while being video-recorded. Participants' facial expressivity in these videos was quantified by blind raters using a well-validated manualized approach (i.e. the Facial Expression Coding System; FACES).

RESULTS

While oxytocin administration did not affect ratings of facial trustworthiness, it significantly increased facial expressivity in individuals with schizophrenia (Z = -2.33, p = 0.02) and at trend level in healthy controls (Z = -1.87, p = 0.06).

CONCLUSIONS

These results demonstrate that oxytocin administration can increase facial expressivity in response to emotional stimuli and suggest that oxytocin may have the potential to serve as a treatment for blunted facial affect in schizophrenia.

Subcortical brain volume abnormalities in 2028 individuals with schizophrenia and 2540 healthy controls via the ENIGMA consortium

The profile of brain structural abnormalities in schizophrenia is still not fully understood, despite decades of research using brain scans. To validate a prospective meta-analysis approach to analyzing multicenter neuroimaging data, we analyzed brain MRI scans from 2028 schizophrenia patients and 2540 healthy controls, assessed with standardized methods at 15 centers worldwide. We identified subcortical brain volumes that differentiated patients from controls, and ranked them according to their effect sizes. Compared with healthy controls, patients with schizophrenia had smaller hippocampus (Cohen's d=-0.46), amygdala (d=-0.31), thalamus (d=-0.31), accumbens (d=-0.25) and intracranial volumes (d=-0.12), as well as larger pallidum (d=0.21) and lateral ventricle volumes (d=0.37). Putamen and pallidum volume augmentations were positively associated with duration of illness and hippocampal deficits scaled with the proportion of unmedicated patients. Worldwide cooperative analyses of brain imaging data support a profile of subcortical abnormalities in schizophrenia, which is consistent with that based on traditional meta-analytic approaches. This first ENIGMA Schizophrenia Working Group study validates that collaborative data analyses can readily be used across brain phenotypes and disorders and encourages analysis and data sharing efforts to further our understanding of severe mental illness.

Oxytocin administration selectively improves olfactory detection thresholds for lyral in patients with schizophrenia

BACKGROUND

Olfaction plays an important role in mammalian social behavior. Olfactory deficits are common in schizophrenia and correlate with negative symptoms and low social drive. Despite their prominence and possible clinical relevance, little is understood about the pathological mechanisms underlying olfactory deficits in schizophrenia and there are currently no effective treatments for these deficits. The prosocial neuropeptide oxytocin may affect the olfactory system when administered intranasally to humans and there is growing interest in its therapeutic potential in schizophrenia.

METHODS

To examine this model, we administered 40IU of oxytocin and placebo intranasally to 31 patients with a schizophrenia spectrum illness and 34 age-matched healthy control participants in a randomized, double-blind, placebo-controlled, cross-over study. On each test day, participants completed an olfactory detection threshold test for two different odors: (1) lyral, a synthetic fragrance compound for which patients with schizophrenia have specific olfactory detection threshold deficits, possibly related to decreased cyclic adenosine 3',5'-monophosphate (cAMP) signaling; and (2) anise, a compound for which olfactory detection thresholds change with menstrual cycle phase in women.

RESULTS

On the placebo test day, patients with schizophrenia did not significantly differ from healthy controls in detection of either odor. We found that oxytocin administration significantly and selectively improved olfactory detection thresholds for lyral but not for anise in patients with schizophrenia. In contrast, oxytocin had no effect on detection of either odor in healthy controls.

DISCUSSION

Our data indicate that oxytocin administration may ameliorate olfactory deficits in schizophrenia and suggest the effects of intranasal oxytocin may extend to influencing the olfactory system. Given that oxytocin has been found to increase cAMP signaling in vitro a possible mechanism for these effects is discussed.

Dynamic functional connectivity analysis reveals transient states of dysconnectivity in schizophrenia

Schizophrenia is a psychotic disorder characterized by functional dysconnectivity or abnormal integration between distant brain regions. Recent functional imaging studies have implicated large-scale thalamo-cortical connectivity as being disrupted in patients. However, observed connectivity differences in schizophrenia have been inconsistent between studies, with reports of hyperconnectivity and hypoconnectivity between the same brain regions. Using resting state eyes-closed functional imaging and independent component analysis on a multi-site data that included 151 schizophrenia patients and 163 age- and gender matched healthy controls, we decomposed the functional brain data into 100 components and identified 47 as functionally relevant intrinsic connectivity networks. We subsequently evaluated group differences in functional network connectivity, both in a static sense, computed as the pairwise Pearson correlations between the full network time courses (5.4 minutes in length), and a dynamic sense, computed using sliding windows (44 s in length) and k-means clustering to characterize five discrete functional connectivity states. Static connectivity analysis revealed that compared to healthy controls, patients show significantly stronger connectivity, i.e., hyperconnectivity, between the thalamus and sensory networks (auditory, motor and visual), as well as reduced connectivity (hypoconnectivity) between sensory networks from all modalities. Dynamic analysis suggests that (1), on average, schizophrenia patients spend much less time than healthy controls in states typified by strong, large-scale connectivity, and (2), that abnormal connectivity patterns are more pronounced during these connectivity states. In particular, states exhibiting cortical–subcortical antagonism (anti-correlations) and strong positive connectivity between sensory networks are those that show the group differences of thalamic hyperconnectivity and sensory hypoconnectivity. Group differences are weak or absent during other connectivity states. Dynamic analysis also revealed hypoconnectivity between the putamen and sensory networks during the same states of thalamic hyperconnectivity; notably, this finding cannot be observed in the static connectivity analysis. Finally, in post-hoc analyses we observed that the relationships between sub-cortical low frequency power and connectivity with sensory networks is altered in patients, suggesting different functional interactions between sub-cortical nuclei and sensorimotor cortex during specific connectivity states. While important differences between patients with schizophrenia and healthy controls have been identified, one should interpret the results with caution given the history of medication in patients. Taken together, our results support and expand current knowledge regarding dysconnectivity in schizophrenia, and strongly advocate the use of dynamic analyses to better account for and understand functional connectivity differences.

•

Studied both static and dynamic connectivity changes in schizophrenia during rest

•

Small but significant connectivity differences might be obscured in static analysis.

•

Patients show significant differences in dwell times in multiple states.

•

Disrupted thalamo-cortical connectivity in schizophrenia in a state-specific manner

Converging evidence for gamma synchrony deficits in schizophrenia

BACKGROUND

In electroencephalogram (EEG) studies of auditory steady-state responses (ASSRs), patients with schizophrenia show a deficit in power and/or phase-locking, particularly at the 40 Hz frequency where these responses resonate. In addition, studies of the transient gamma-band response (GBR) elicited by single tones have revealed deficits in gamma power and phase-locking in schizophrenia. We examined the degree to which the 40 Hz ASSR and the transient GBR to single tones are correlated and whether they assess overlapping or distinct gamma-band abnormalities in schizophrenia.

METHODS

EEG was recorded during 40 Hz ASSR and auditory oddball paradigms from 28 patients with schizophrenia or schizoaffective disorder (SZ) and 25 age- and gender-matched healthy controls (HC). The ASSR was elicited by 500 ms click trains, and the transient GBR was elicited by the standard tones from the oddball paradigm. Gamma phase and magnitude values, calculated using Morlet wavelet transformations, were used to derive total power and phase-locking measures.

RESULTS

Relative to HC, SZ patients had significant deficits in total gamma power and phase-locking for both ASSR- and GBR-based measures. Within both groups, the 40 Hz ASSR and GBR phase-locking measures were significantly correlated, with a similar trend evident for the total power measures. Moreover, co-varying for GBR substantially reduced 40 Hz ASSR power and phase-locking differences between the groups.

CONCLUSIONS

40 Hz ASSR and transient GBR measures provide very similar information about auditory gamma abnormalities in schizophrenia, despite the overall enhancement of 40 Hz ASSR total power and phase-locking values relative to the corresponding GBR values.

Electrophysiological and diffusion tensor imaging evidence of delayed corollary discharges in patients with schizophrenia

BACKGROUND

Patients with schizophrenia (SZ) characteristically exhibit supranormal levels of cortical activity to self-induced sensory stimuli, ostensibly because of abnormalities in the neural signals (corollary discharges, CDs) normatively involved in suppressing the sensory consequences of self-generated actions. The nature of these abnormalities is unknown. This study investigated whether SZ patients experience CDs that are abnormally delayed in their arrival at the sensory cortex.

METHOD

Twenty-one patients with SZ and 25 matched control participants underwent electroencephalography (EEG). Participants' level of cortical suppression was calculated as the amplitude of the N1 component evoked by a button press-elicited auditory stimulus, subtracted from the N1 amplitude evoked by the same stimulus presented passively. In the three experimental conditions, the auditory stimulus was delivered 0, 50 or 100 ms subsequent to the button-press. Fifteen SZ patients and 17 healthy controls (HCs) also underwent diffusion tensor imaging (DTI), and the fractional anisotropy (FA) of participants' arcuate fasciculus was used to predict their level of cortical suppression in the three conditions.

RESULTS

While the SZ patients exhibited subnormal N1 suppression to undelayed, self-generated auditory stimuli, these deficits were eliminated by imposing a 50-ms, but not a 100-ms, delay between the button-press and the evoked stimulus. Furthermore, the extent to which the 50-ms delay normalized a patient's level of N1 suppression was linearly related to the FA of their arcuate fasciculus.

CONCLUSIONS

These data suggest that SZ patients experience temporally delayed CDs to self-generated auditory stimuli, putatively because of structural damage to the white-matter (WM) fasciculus connecting the sites of discharge initiation and destination.

Working memory and DLPFC inefficiency in schizophrenia: the FBIRN study

BACKGROUND

The Functional Imaging Biomedical Informatics Network is a consortium developing methods for multisite functional imaging studies. Both prefrontal hyper- or hypoactivity in chronic schizophrenia have been found in previous studies of working memory.

METHODS

In this functional magnetic resonance imaging (fMRI) study of working memory, 128 subjects with chronic schizophrenia and 128 age- and gender-matched controls were recruited from 10 universities around the United States. Subjects performed the Sternberg Item Recognition Paradigm1,2 with memory loads of 1, 3, or 5 items. A region of interest analysis examined the mean BOLD signal change in an atlas-based demarcation of the dorsolateral prefrontal cortex (DLPFC), in both groups, during both the encoding and retrieval phases of the experiment over the various memory loads.

RESULTS

Subjects with schizophrenia performed slightly but significantly worse than the healthy volunteers and showed a greater decrease in accuracy and increase in reaction time with increasing memory load. The mean BOLD signal in the DLPFC was significantly greater in the schizophrenic group than the healthy group, particularly in the intermediate load condition. A secondary analysis matched subjects for mean accuracy and found the same BOLD signal hyperresponse in schizophrenics.

CONCLUSIONS

The increase in BOLD signal change from minimal to moderate memory loads was greater in the schizophrenic subjects than in controls. This effect remained when age, gender, run, hemisphere, and performance were considered, consistent with inefficient DLPFC function during working memory. These findings from a large multisite sample support the concept not of hyper- or hypofrontality in schizophrenia, but rather DLPFC inefficiency that may be manifested in either direction depending on task demands. This redirects the focus of research from direction of difference to neural mechanisms of inefficiency.

Neurophysiological evidence of corollary discharge dysfunction in schizophrenia

OBJECTIVE

Speaking is hypothesized to generate a corollary discharge of motor speech commands transmitted to the auditory cortex, dampening its response to self-generated speech sounds. Event-related potentials were used to test whether failures of corollary discharge during speech contribute to the pathophysiology of schizophrenia.

METHOD

The N1 component of the event-related potential elicited by vowels was recorded while the vowels were spoken by seven patients with schizophrenia and seven healthy comparison subjects and while the same vowels were played back.

RESULTS

In the healthy subjects, the N1 elicited by spoken vowels was smaller than the N1 elicited by played-back vowels. This reduction in N1 elicited by spoken vowels was not observed in the patients with schizophrenia.

CONCLUSIONS

These findings provide direct neurophysiological evidence for a corollary discharge that dampens sensory responses to self-generated, relative to externally presented, percepts in healthy comparison subjects and its failure in patients with schizophrenia.

Cortical responsiveness during inner speech in schizophrenia: an event-related potential study

OBJECTIVE

The study assessed the effects of inner speech on auditory cortical responsiveness in schizophrenia.

METHOD

Comparison subjects (N=15) and patients with schizophrenia (N=15) were presented with acoustic and visual stimuli during three conditions: while subjects were silent, when spontaneous inner speech might occur; during directed inner speech, while subjects repeated a statement silently to themselves; and while subjects listened to recorded speech. N1 event-related potentials were recorded during the three conditions.

RESULTS

N1 event-related potentials elicited by acoustic stimuli, but not by visual stimuli, were lower during directed inner speech than during the silent baseline condition in the comparison subjects but not in the patients.

CONCLUSIONS

Abnormal auditory cortical responsiveness to inner speech in patients with schizophrenia may be a sign of corollary discharge dysfunction, which may potentially cause misattribution of inner speech to external voices.

Cortical responsiveness during talking and listening in schizophrenia: an event-related brain potential study

BACKGROUND

Failures to recognize inner speech as self-generated may underlie positive symptoms of schizophrenia-like auditory hallucinations. This could result from a faulty comparison in auditory cortex between speech-related corollary discharge and reafferent discharges from thinking or speaking, with misattribution of internal thoughts to external sources. Although compelling, failures to monitor covert speech (thoughts) are not as amenable to investigation as failures to monitor overt speech (talking).

METHODS

Effects of talking on auditory cortex responsiveness were assessed in 10 healthy adults and 12 patients with schizophrenia (DSM-IV) using N1 event-related potentials (ERPs) to acoustic and visual probes during talking aloud, listening to one's speech played back, and silent baseline. Trials contaminated by muscle artifact while talking were excluded.

RESULTS

Talking and listening affected N1 to acoustic but not to visual probes, reflecting modality specificity of effects. Patterns of responses to acoustic probes differed between control subjects and patients. N1 to acoustic probes was reduced during talking compared with baseline in control subjects, but not in patients. Listening reduced N1 equivalently in both groups.

CONCLUSIONS

Although the failure of N1 to be reduced during talking was not related to current hallucinations in patients, it may be related to the potential to hallucinate.

N1 and P300 abnormalities in patients with schizophrenia, epilepsy, and epilepsy with schizophrenialike features

BACKGROUND

The scalp-recorded N1 and P300 components of the event-related brain potential (ERP) are commonly reduced in patients with schizophrenia but not in patients with epilepsy. Epilepsy patients with interictal chronic schizophrenialike features (EPI-SZ) provide a comparison group for determining whether the ERP amplitude abnormalities seen in schizophrenic patients are associated with shared clinical features of EPI-SZ and schizophrenic patients or overlapping pathophysiologies, or are specific to a distinct schizophrenia etiology.

METHODS

Patients with schizophrenia (n = 24) were compared with normal control subjects (n = 32) and patients with epilepsy syndromes on visual and auditory oddball ERP paradigms. Epilepsy patients included those with chronic interictal schizophrenialike features (n = 6) and those without (n = 16).

RESULTS

Auditory P300 amplitude was reduced in both schizophrenic and EPI-SZ patients, whose positive or negative symptoms did not differ. In contrast, N1 amplitude was reduced only in schizophrenic patients. Delays in both N1 and P300 were associated with epilepsy patients and EPI-SZ but not schizophrenic patients.

CONCLUSIONS

The schizophrenialike symptoms in epilepsy probably represent a phenocopy of schizophrenia with common clinical features and some common pathophysiologies but distinct etiologies. P300 amplitude appears to be sensitive to schizophrenialike features, regardless of whether they occur in the context of schizophrenia or epilepsy. N1 amplitude reduction appears to be specific to schizophrenia, suggesting its sensitivity to the distinct etiology of schizophrenia.

Functional neuroanatomy of auditory working memory in schizophrenia: relation to positive and negative symptoms

Functional brain imaging studies of working memory (WM) in schizophrenia have yielded inconsistent results regarding deficits in the dorsolateral prefrontal (DLPFC) and parietal cortices. In spite of its potential importance in schizophrenia, there have been few investigations of WM deficits using auditory stimuli and no functional imaging studies have attempted to relate brain activation during auditory WM to positive and negative symptoms of schizophrenia. We used a two-back auditory WM paradigm in a functional MRI study of men with schizophrenia (N = 11) and controls (N = 13). Region of interest analysis was used to investigate group differences in activation as well as correlations with symptom scores from the Brief Psychiatric Rating Scale. Patients with schizophrenia performed significantly worse and were slower than control subjects in the WM task. Patients also showed decreased lateralization of activation and significant WM related activation deficits in the left and right DLPFC, frontal operculum, inferior parietal, and superior parietal cortex but not in the anterior cingulate or superior temporal gyrus. These results indicate that in addition to the prefrontal cortex, parietal cortex function is also disrupted during WM in schizophrenia. Withdrawal-retardation symptom scores were inversely correlated with frontal operculum activation. Thinking disturbance symptom scores were inversely correlated with right DLPFC activation. Our findings suggest an association between thinking disturbance symptoms, particularly unusual thought content, and disrupted WM processing in schizophrenia.

Event-related brain potential evidence of spared knowledge in Alzheimer's disease

The authors recorded event-related brain potentials (ERPs) to picture primes and word targets (picture-name verification task) in patients with Alzheimer's disease (AD) and in elderly and young participants. N400 was more negative to words that did not match pictures than to words that did match pictures in all groups: In the young, this effect was significant at all scalp sites; in the elderly, it was only at central-parietal sites; and in AD patients, it was limited to right central-parietal sites. Among AD patients pretested with a confrontation-naming task to identify pictures they could not name, neither the N400 priming effect nor its scalp distribution was affected by ability to name pictures correctly. This ERP evidence of spared knowledge of these items was complemented by 80% performance accuracy. Thus, although the name of an item may be inaccessible in confrontation naming, N400 shows that knowledge is intact enough to prime cortical responses.

Progressive brain volume changes and the clinical course of schizophrenia in men: a longitudinal magnetic resonance imaging study

BACKGROUND

We sought to determine whether the brain dysmorphology previously observed cross-sectionally in people with schizophrenia progresses over time and whether such progression is related to the severity of the illness course.

SUBJECTS AND METHODS

Men with chronic schizophrenia (n = 24) and control men (n = 25) received 2 brain magnetic resonance imaging scans, on average 4 years apart. Changes in brain volume were adjusted for head-repositioning error and expressed as slopes (cubic centimeters per year). Clinical course severity for the schizophrenic patients was assessed using the mean of time 1 and time 2 Brief Psychiatric Rating Scale (BPRS) scores and the percentage of time the patient was hospitalized during the interscan interval.

RESULTS

Schizophrenic patients exhibited faster volume decline than control subjects in right frontal gray matter and bilateral posterior superior temporal gray matter, as well as faster cerebrospinal fluid volume expansion in right frontal sulci, left lateral ventricle, and bilateral prefrontal and posterior superior temporal sulci. Faster rates of frontal sulcal expansion were related to greater BPRS total and positive symptom scores and longer time hospitalized. Prefrontal gray matter decline and sulcal expansion were associated with greater BPRS negative symptom scores and longer time hospitalized. Temporal lobe gray matter decline was associated with greater BPRS total and negative symptom scores.

CONCLUSIONS

This controlled study revealed that patients with chronic schizophrenia exhibited accelerated frontotemporal cortical gray matter decline and cortical sulcal and lateral ventricular expansion. Further, greater clinical severity was associated with faster rates of frontotemporal brain volume changes. These observations are consistent with a progressive pathophysiological process but need to be replicated in a larger sample.

Left temporal deficit of P300 in patients with schizophrenia: effects of task

P300 is often, but not always, observed to be more reduced over left than right temporal lobes in patients with schizophrenia. The possibility that task differences contribute to the inconsistency in the literature was explored in this study. ERPs were collected from 17 right-handed men with schizophrenia (DSM-IIIR) and 11 right-handed healthy male community controls, performing three auditory oddball tasks - respond to a target tone by: (1) counting; (2) pressing a response button with the right index finger; or (3) pressing a response button with the left index finger. Although patients with schizophrenia had smaller and later P300 amplitudes than controls, they did not have smaller P300s over the left temporal scalp (T3) than over the right (T4). P300 recorded over the left (C3) and right (C4) motor cortices indicated sensitivity to responding hand, with greater negativity being associated with contralateral button pressing. Failure to find P300 asymmetry is not related to the presence or absence of a button pressing task, or the hand used for button pressing. Rather, P300 asymmetry may be related to structural neuroanatomical asymmetries.

Contribution of alcohol abuse to cerebellar volume deficits in men with schizophrenia

BACKGROUND

It is controversial whether cerebellar tissue volume deficits occur in schizophrenia and, if so, what regions and tissue types are affected. Complicating such investigations is the high incidence of alcoholism comorbidity in patients with schizophrenia that itself can contribute to cerebellar abnormalities.

METHOD

We studied 61 healthy men (control subjects), 25 men with alcoholism, 27 men with schizophrenia, and 19 men comorbid for schizophrenia and alcoholism with the use of magnetic resonance imaging. Cerebellar structures were outlined manually, tissue classification was determined statistically, and regional volumes were corrected for normal variation in head size and age.

RESULTS

Patients with schizophrenia alone had enlarged fourth ventricles (1.5 SD relative to controls) but showed no cerebellar tissue volume deficits. The alcoholic group had gray and white matter vermian deficits (-0.5 SD), most prominent in anterior superior lobules, and gray matter hemisphere deficits (-0.8 SD), but not fourth ventricle enlargement. The comorbid group had cerebellar hemisphere (-1.3 SD) and vermian gray matter volume deficits (-0.7 SD) and fourth ventricular enlargement (1.6 SD); these abnormalities were greater than in either single-diagnosis group, despite significantly lower levels of alcohol consumption compared with the alcoholic group. Gray matter volume in the anterior superior vermis correlated with lifetime alcohol consumption in the schizophrenic and comorbid groups when combined.

CONCLUSIONS

Cerebellar tissue volume deficits were detected in schizophrenia only when accompanied by alcoholism. By contrast, fourth ventricular enlargement occurred in schizophrenia even without alcoholism, although it was exacerbated by alcoholism. These findings support a model of cerebellar supersensitivity to alcohol-related tissue volume deficits in schizophrenia.

P300 reduction and prolongation with illness duration in schizophrenia

BACKGROUND

The P300 component of the auditory event-related potential (ERP) is both reduced in amplitude and delayed in schizophrenia. P300 is prolonged and, less consistently, reduced with normal aging. Additional latency delays are observed in neurodegenerative disorders. We asked whether P300 is reduced and delayed with longer illness duration in schizophrenia, consistent with a neurodegenerative process.

METHODS

P300 amplitude and latency were recorded to infrequent auditory target stimuli from 35 men with schizophrenia (DSM-III-R) and 26 control men. Effects of current age, age of onset, and duration of illness on P300 were assessed using regression analysis.

RESULTS

P300 amplitude showed no age-related decrease in either group; however, among schizophrenic participants, P300 amplitude correlated positively with onset age and negatively with illness duration. P300 latency correlated positively with age in schizophrenic participants and also tended to increase with age in controls. Slopes of the latency-age relationships were significantly greater in schizophrenic participants than in control participants. Latency also correlated positively with illness duration but showed no relationship to onset age.

CONCLUSIONS

P300 amplitude and latency are reduced and delayed with longer illness duration in schizophrenia, consistent with a progressive pathophysiological process. Reduced P300 amplitude may also be a marker of an early onset variant of schizophrenia.

Trait and state aspects of P300 amplitude reduction in schizophrenia: a retrospective longitudinal study

BACKGROUND

The P300 component of the auditory event-related brain potential (ERP) is consistently reduced in schizophrenia. Longitudinal data are examined to determine whether P300 amplitude is a trait marker of schizophrenia or a state marker tracking clinical fluctuations over time.

METHODS

Schizophrenic men (DSM-III-R) (n = 36) received ERP and the Brief Psychiatric Rating Scale (BPRS) assessments on multiple occasions, at varying intervals, under varying medication states. Automatically elicited auditory P3a and effortfully elicited auditory and visual P3b amplitudes were assessed. Brief Psychiatric Rating Scale scores were regressed on P300 amplitude within patients using both multiple regression models and nonparametric analyses of individual patient slopes. Event related brain potentials in patients were compared to ERPs from 34 age-matched control men, and stability of P300 over time was estimated with intraclass correlations.

RESULTS

P300 amplitude, regardless of elicitation method or sensory modality, tracked BPRS Total and positive symptom scores over time, decreasing with symptom exacerbations and increasing with improvements. In addition, effortful auditory and visual P3b amplitudes tracked negative symptoms, and automatic auditory P3a tracked depression-anxiety symptoms. When analyses were limited to unmedicated occasions, auditory P3a and P3b persisted in tracking BPRS Total scores, with additional tracking of positive symptoms by P3b and mood symptoms by P3a. Mean auditory and visual P3bs, averaged over all measurement occasions for each individual, were inversely related to mean negative symptoms. Auditory P3a and P3b, but not visual P3b, amplitudes were smaller in patients than control subjects, even when patients were least symptomatic. P300 amplitudes showed high test-retest reliability in control subjects and patients and moderate stability over time in patients.

CONCLUSIONS

Auditory, and possibly visual, P300 amplitudes track fluctuations in clinical state, but only auditory P300 amplitude is a trait marker of schizophrenia.

P300 amplitude is related to clinical state in severely and moderately ill patients with schizophrenia

BACKGROUND

Relationships between illness severity and neurobiologic abnormalities in schizophrenia were studied in subpopulations varying in clinical severity.

METHODS

Auditory ERPs were collected from 28 severely ill, chronically hospitalized schizophrenic men from a state hospital; 29 moderately ill inpatient and outpatient schizophrenic men from a veterans hospital; and 30 healthy male subjects from the community as controls. Clinical symptoms were evaluated in patients using the Brief Psychiatric Rating Scale (BPRS).

RESULTS

Both schizophrenic patient groups had smaller P300 amplitude than the control subjects. Severely ill patients had smaller P300s than moderately ill patients and scored higher on three BPRS factor scores as well as BPRS Total. Among severely ill patients, P300 amplitude was unrelated to clinical symptoms. Among moderately ill patients, P300 was related to Withdrawal/Retardation, Anxiety/Depression, and BPRS Total. After combining patients, Thinking Disturbance emerged as an additional correlate of P300. Group differences in P300 could not be accounted for by group differences in symptom severity using analysis of covariance.

CONCLUSIONS

Reduced P300 amplitude marks the diagnosis of schizophrenia, but also reflects individual differences in severity, including positive symptoms. Previous failures to find relationships between positive symptoms and P300 may have been due to a restricted range of clinical severity.

A controlled study of cortical gray matter and ventricular changes in alcoholic men over a 5-year interval

BACKGROUND

We report on structural brain changes during a 5-year period in healthy control and alcoholic men.

METHODS

Alcoholic patients (n = 16), from an initial group of 58 who underwent brain magnetic resonance imaging scanning while in treatment, were rescanned with the same acquisition sequence approximately 5 years later. Control subjects (n = 28) spanning the same age range also were scanned twice at a comparable interval. Changes in brain volume were corrected for error due to differences in head placement between scans and expressed as slopes (cubic centimeters per year), percentage of change over baseline for the control subjects, and standardized change for the alcoholic patients. The alcoholic patients varied considerably in the percentage of time that symptoms of alcohol dependence were present and in the amount of alcohol consumed during follow-up.

RESULTS

The cortical gray matter diminished in volume over time in the control subjects, most prominently in the prefrontal cortex, while the lateral and third ventricles enlarged. The alcoholic patients showed similar age-related changes with a greater rate of gray matter volume loss than the control subjects in the anterior superior temporal lobe. The amount of alcohol consumed during follow-up predicted the rate of cortical gray matter volume loss, as well as sulcal expansion. The rate of ventricular enlargement in alcoholic patients who maintained virtual sobriety was comparable to that in the control subjects.

CONCLUSIONS

During a 5-year period, brain volume shrinkage is exaggerated in the prefrontal cortex in normal aging with additional loss in the anterior superior temporal cortex in alcoholism. The association of cortical gray matter volume reduction with alcohol consumption over time suggests that continued alcohol abuse results in progressive brain tissue volume shrinkage.

Association between regional brain volumes and clozapine response in schizophrenia

BACKGROUND

Clozapine has shown considerable therapeutic promise in the treatment of schizophrenia; however, the clinical risks and initial high treatment costs associated with its administration motivate the search to identify patients who will best respond. Neuroimaging studies have suggested that prefrontal sulcal prominence may be a predictor of nonresponsiveness.

METHODS

We used magnetic resonance imaging (MRI) to test whether volumes in any cortical regions of the brain were associated with symptom improvement with clozapine treatment. The 21 schizophrenic men studied were clinically evaluated during treatment with typical neuroleptics (baseline) and after a mean of 6.2 months treatment with clozapine (final dose 300-900, median = 562 mg/day). At least a 20% improvement on total Brief Psychiatric Rating Scale (BPRS) was seen in 47.6% of the schizophrenics. Clinical improvement was regressed on baseline differences in clinical severity, and the residual scores were related to MRI values.

RESULTS

Patients with larger anterior superior temporal lobe cerebrospinal fluid volumes (primarily sylvian fissure) showed greater improvement on total BPRS and withdrawal/retardation symptoms.

CONCLUSIONS

Even schizophrenics with significant brain dysmorphology can have a positive clinical response to clozapine.

Patterns of regional cortical dysmorphology distinguishing schizophrenia and chronic alcoholism

BACKGROUND

This study used magnetic resonance imaging (MRI) to compare the extent and pattern of tissue volume deficit and cerebrospinal fluid volume enlargement in chronic alcoholics and schizophrenics.

METHODS

The subjects included 62 detoxified chronic alcoholics (26-63 years), 71 schizophrenics (23-63 years), and 73 controls spanning the adult age range (21-70 years). MRI volumes were adjusted for normal variation in head size and age established from the control group.

RESULTS

Both patient groups showed widespread cortical gray matter volume deficits compared with controls, but only the alcoholics had white matter volume deficits. The schizophrenics had significantly greater volume deficits in the prefrontal and anterior superior temporal gray matter than in the more posterior cortical regions. By contrast, the deficits in the alcoholics were relatively homogeneous across the cortex. For white matter, the deficits in the alcoholics were greatest in the prefrontal and temporal-parietal regions. Although both patient groups had abnormally larger cortical sulci and lateral and third ventricles than the controls, the alcoholics had significantly larger sulcal volumes in the frontal, anterior, and posterior parietal-occipital regions than the schizophrenics.

CONCLUSIONS

This quantitative MRI study revealed different patterns of regional cortical volume abnormalities in schizophrenics and alcoholics. The schizophrenic group exhibited cortical gray matter volume deficits of modestly greater magnitude than that observed in the alcoholic group, and the alcoholics but not the schizophrenics exhibited cortical white matter volume deficits.

Frontal lobe volume loss observed with magnetic resonance imaging in older chronic alcoholics

This study used magnetic resonance imaging to quantify the extent and pattern of tissue volume deficit and cerebrospinal fluid volume enlargement in younger versus older chronic alcoholics relative to normal controls. In the present analysis, we divided our previously reported group of 62 alcoholic men into a younger group (n = 33, age mean = 37.5 +/- 4.5, and range = 26 to 44 years) and an older group (n = 29, age mean = 52.7 +/- 6.0, and range = 45 to 63 years) to examine whether, in addition to extent, the two age groups differed in pattern of tissue type and regional brain volume abnormalities quantified with magnetic resonance imaging. Brain volumes were adjusted for normal variation in head size and age established from a group of healthy controls and were expressed as Z-scores. The younger group had significant cortical gray, but not white, matter volume deficits and sulcal and ventricular enlargement relative to age-matched controls. The older group had volume deficits in both cortical gray and white matter and sulcal and ventricular enlargement that significantly exceeded the younger alcoholic group. An analysis of six cortical regions revealed that, although both age groups had gray matter volume deficits throughout the cortex, the older alcoholic group had a selectively more severe deficit in prefrontal gray matter relative to the younger alcoholic group. Similarly, the cortical white matter volume deficit in the older alcoholics was especially severe in the prefrontal and frontal regions. The differences in brain dysmorphology between the two alcoholic groups cannot easily be attributed to potential alcohol history differences typically related to age because the two groups had similar disease durations and amounts of lifetime alcohol consumption. These results provide in vivo evidence that the frontal lobes are especially vulnerable to chronic alcoholism in older men.

Relationship between alcohol withdrawal seizures and temporal lobe white matter volume deficits

A previous magnetic resonance imaging study from our laboratory reported significant temporal lobe volume deficits in cortical gray matter, white matter, and anterior hippocampus in chronic alcoholic men relative to controls. In the present study, we reexamined these data and asked whether withdrawal seizure history was predictive of either the hippocampal or the extrahippocampal volume deficits. A review of the medical charts indicated that 11 alcoholics had experienced one or more alcohol-related seizures and 35 were seizure-free; no patient had a seizure disorder unrelated to alcohol. The two alcoholic groups did not differ significantly in age, education, alcohol consumption variables, premorbid intelligence, Memory Quotient, Trail Making, or detection of hidden figures. Although each alcoholic group showed significant bilateral volume deficits of the anterior hippocampus and frontal-parietal and temporal gray matter, relative to controls, the seizure group had significantly smaller temporal lobe white matter volumes than either the control or the seizure-free groups; the latter two groups did not differ from each other. Both alcoholic groups, however, had white matter volume deficits in the frontal-parietal region. Thus, the seizure group accounted for the white matter volume deficits in the temporal lobe previously reported in the full sample of alcoholics. It seems, then, that reduced white matter volume in the temporal lobes may be either a risk factor for or sequela of alcohol withdrawal seizures.

Longitudinal changes in magnetic resonance imaging brain volumes in abstinent and relapsed alcoholics

Chronic alcoholism is associated with smaller volumes of cortical gray matter and white matter and a complementary increase in brain cerebrospinal fluid (CSF) volumes, relative to age norms. This longitudinal study quantified the extent of brain volume changes associated with abstinence and drinking at three time points in chronic alcoholics. We obtained magnetic resonance imaging (MRI) on 58 alcoholic men after an average of 12 days (MRI-1) and 32 days (MRI-2) of sobriety. In addition, 58 healthy control subjects were scanned at a comparable interval. At MRI-3, 11 controls and 39 alcoholics were rescanned, 2-12 months after MRI-2; 19 alcoholics had abstained, and 20 had resumed drinking. Axial MRI slices were segmented into cortical gray matter, white matter, and CSF and summed over seven slices; lateral and third ventricular volumes were also estimated. MRI volume changes were corrected using an estimate of interscan measurement error caused by head positioning differences, and then divided by the interval to yield rates of change (slopes). From MRI-1 to MRI-2, the alcoholic group showed declines in CSF volumes of the lateral ventricles and posterior cortical sulci, and a trend toward an increase in anterior cortical gray matter volume relative to the control group. From MRI-2 to MRI-3, third ventricular volumes decreased in the abstainers relative to the relapsers and controls; cortical white matter volume decreased in the relapsers. In the relapsers, lifetime consumption of alcohol (as of MRI-1) predicted later vulnerability to white matter volume decline and third ventricular enlargement with resumption of drinking. These data suggest that improvement in cortical gray matter, sulcal, and lateral ventricular volumes occur early in the course of abstinence, and that improvement in third ventricular volume appears later with continued abstinence.(ABSTRACT TRUNCATED AT 250 WORDS)

Age-related decline in MRI volumes of temporal lobe gray matter but not hippocampus

The effect of normal aging on the volume of the hippocampus and temporal cortex was assessed cross-sectionally with quantitative Magnetic Resonance Imaging (MRI) in 72 healthy men, spanning 5 decades of the adult age range (21 to 70 years). Neither the hippocampal nor cortical white matter volumes were significantly correlated with age. By contrast, left and right temporal lobe gray matter volumes, exclusive of the hippocampal measures, each decreased with age (p < 0.01). Volumes of temporal lobe sulcal CSF and the ventricular system (temporal horns and lateral and third ventricles) significantly increased with age. Measures of verbal and nonverbal working memory showed age-related declines and were related to enlargement of the three ventricular regions, which may be indicative of age-related atrophy of the adjacent cortex but not the hippocampus, at least up to age 70 years.

Longitudinal volumetric computed tomographic analysis of regional brain changes in normal aging and Alzheimer's disease

OBJECTIVE

This study used a semiautomated image analysis technique to quantify the rate and regional pattern of cerebrospinal fluid (CSF) volume changes in the computed tomographic brain examinations of healthy adults and patients with Alzheimer's disease (AD).

DESIGN

Longitudinal, within-subject design, with statistical correction for longitudinal method error (eg, head repositioning effects).

SETTING

Palo Alto (Calif) Department of Veterans Affairs Medical Center.

PATIENTS AND OTHER PARTICIPANTS

The 41 patients with AD were recruited from the Geriatric Psychiatry Research Unit and the National Institute of Mental Health Clinical Research Center of the Palo Alto Department of Veterans Affairs Medical Center. The 35 healthy control subjects were recruited from the local community.

MAIN OUTCOME MEASURES

Cerebrospinal fluid volumes estimated from computed tomographic scans.

RESULTS

Even after accounting for an estimate of method error (eg, head positioning effects) across computed tomographic examinations, the patients with AD showed greater annual CSF volume increases than did the control group. This CSF volume enlargement was not uniform across brain regions of interest; rather, the patients with AD showed disproportionate volume increases in the ventricular system and the sylvian fissures. Greater CSF volume changes in the patients with AD were significantly associated with greater cognitive decline on the Mini-Mental State Examination. Furthermore, younger patients with AD showed more rapid progression on computed tomographic scans than did older patients.

CONCLUSIONS

The rate of CSF volume enlargement is region specific, with the most marked annual rate of change occurring in the ventricular system and the sylvian fissures. In addition, younger patients show more rapid progression in the ventricular and frontal sulcal brain regions of interest than do older patients.

Anterior hippocampal volume deficits in nonamnesic, aging chronic alcoholics

Magnetic resonance imaging was used to quantify the volume of the hippocampus in 47 men with chronic alcoholism and 72 healthy male control subjects. The subjects ranged in age from 21 to 70 years, thus permitting a test of whether older alcoholics suffer greater brain tissue volume reduction than do younger ones. Comparison brain regions included temporal lobe gray matter, white matter, and cerebrospinal fluid, as well as measures of the lateral ventricles, third ventricle, and temporal horns. The results of this cross-sectional study showed that the anterior, but not the posterior, portions of the hippocampus in both hemispheres were significantly smaller in the alcoholic than the healthy control group. Furthermore, the bilateral anterior hippocampal volume loss was greater in older than younger alcoholics. Despite the hippocampal volume deficit, these alcoholics did not demonstrate an explicit memory impairment; furthermore, memory test scores did not correlate significantly with hippocampal volumes. In the alcoholics, the age-related volume loss, which was over and above that expected in normal aging, was also evident in the temporal cortex and white matter. Likewise, alcoholic ventricular enlargement was age-related. Analysis of covariance revealed that the anterior hippocampal deficit persisted after accounting for the temporal lobe gray matter volume deficit. Multiple regression analysis revealed that the age-related brain volume abnormalities observed in the alcoholics could not be attributed to duration of alcoholism or total lifetime consumption of alcohol.

A quantitative magnetic resonance imaging study of changes in brain morphology from infancy to late adulthood

OBJECTIVE

To model in vivo the dynamic interrelations of head size, gray matter, white matter, and cerebrospinal fluid (CSF) volumes from infancy to old age using magnetic resonance imaging (MRI).

DESIGN

Cross-sectional, between-subjects using an age-regression model.

SETTING

A Veterans Affairs medical center and community hospitals.

PARTICIPANTS

There were 88 male and female subjects aged 3 months to 30 years whose clinical MRI film had been read as normal and 73 healthy male volunteers aged 21 to 70 years who had an MRI performed specifically for this study.

MAIN OUTCOME MEASURES

These MRI data were quantified using a semiautomated computer technique for segmenting images into gray matter, white matter, and CSF compartments. The cortex was defined geometrically as the outer 45% on each analyzed slice, and the volumes of cortical white matter, gray matter, and CSF were computed. Subcortical (ventricular) CSF volume was computed for the inner 55% of each analyzed slice.

RESULTS

In the younger sample, intracranial volume increased by about 300 mL from 3 months to 10 years. The same patterns of change in volume of each compartment across the age range were seen in both sexes: cortical gray matter volume peaked around age 4 years and decreased thereafter; cortical white matter volume increased steadily until about age 20 years; cortical and ventricular CSF volumes remained constant. In the older sample, brain volumes were statistically adjusted for normal variation in head size through a regression procedure and revealed the following pattern: cortical gray matter volume decreased curvilin-early, showing an average volume loss of 0.7 mL/y, while cortical white matter volume remained constant during the five decades; complementary to the cortical gray matter decrease, cortical CSF volume increased by 0.6 mL/y and ventricular volumes increased by 0.3 mL/y.

CONCLUSIONS

These patterns of growth and change seen in vivo with MRI are largely consistent with neuropathological studies, as well as animal models of development, and may reflect neuronal progressive and regressive processes, including cell growth, myelination, cell death, and atrophy.

Increase in brain cerebrospinal fluid volume is greater in older than in younger alcoholic patients: a replication study and CT/MRI comparison

This cross-sectional study used a semi-automated analysis technique to quantify regional brain cerebrospinal fluid (CSF) volumes derived from computed tomography (CT) in 84 healthy men ranging from 21 to 82 years of age and 28 patients meeting Research Diagnostic Criteria for alcohol dependence. The goals were to replicate an earlier CT study of an independent sample of alcoholic and control subjects (Pfefferbaum et al., 1988a; Zipursky et al., 1988) and to compare CT assessments of brain changes with magnetic resonance imaging (MRI) assessments made in the same alcoholic patients (Pfefferbaum et al., 1992). Regional brain changes associated with normal aging were derived by regression analysis, using CT data collected from the healthy control subjects. As in the earlier CT study and in the concurrent MRI study, ventricular and sulcal CSF volumes in alcoholic patients were greater than would be expected for their age. Furthermore, the present CT study replicated the previous CT and MRI findings of a positive relationship between age and CSF volume enlargement in alcoholic patients over and above the normal age-related increase in CSF volume, suggesting greater vulnerability of the aging brain to alcohol. Comparison of CT- and MRI-derived estimates of ventricular and cortical sulcal volume revealed high correlations (> 0.80). MRI and CT produced similar absolute ventricular volumes, while MRI produced larger sulcal volume estimates than did CT. The difference in sulcal volume estimate may be due to differences between CT and MRI in slice thickness and sensitivity to partial volume effects.

Correction for head size in brain-imaging measurements

Structural brain-imaging measurements based on computed tomography (CT) or magnetic resonance imaging (MRI) are often corrected or adjusted for normal variation in head size. Some methods of head-size correction, such as the ventricle-brain ratio (VBR), are based on taking the brain structure size as a proportion of the estimated head size, while other methods have used a regression model to obtain head-size residualized structure measures. Recently, head-size correction was shown to result in less reliable volumetric measures of brain structures (Arndt et al., 1991). In the present study, MRI was used to examine the effects of head-size correction on the interrater reliability of volumetric measures of gray matter, white matter, and cerebrospinal fluid. Four raters independently scored MRI brain images from 26 subjects, generating separate estimates of head size and region of interest (ROI) size. Two methods were used to correct MRI values for differences in head size, one based on proportions and the other based on linear regression. Results confirmed that head-size correction did produce measures with lower reliability; however, further analysis based on classical measurement theory showed that the lower reliability was attributable not only to increased measurement error variance, but also to reduced true score variance. Subsequent analyses of criterion validity compared the raw (uncorrected) and head-size-corrected ROI measures in terms of their correlations with age in a sample of 43 normal control subjects, and in terms of their ability to differentiate schizophrenic patients (n = 22) from normal control subjects (n = 20). Results indicated that head-size correction often improved criterion validity, producing higher correlations with age and with diagnostic status than those produced by the raw measures. These findings suggest that head-size correction removes irrelevant true-score variance which reduces reliability yet improves the correlations with validity criteria such as age and diagnostic status.

Greater abnormalities of brain cerebrospinal fluid volumes in younger than in older patients with Alzheimer's disease

OBJECTIVE

This study used a semiautomated analysis technique to quantify differences in regional brain cerebrospinal fluid volumes observed with computed tomography between healthy adults and patients with Alzheimer's disease (AD).

DESIGN

Cross-sectional, between-subject design, using an age-regression model.

SETTING

Palo Alto (Calif) Department of Veterans Affairs Medical Center.

PATIENTS AND OTHER PARTICIPANTS

The 117 patients with probable or definite AD were recruited from the Geriatric Psychiatry Research Unit and National Institute of Mental Health Clinical Research Center of the Palo Alto Department of Veterans Affairs Medical Center. The 114 healthy volunteers were recruited from the local community.

MAIN OUTCOME MEASURES

Cerebrospinal fluid volumes estimated from computed tomographic scans and neuropsychological test scores.

RESULTS

The computed tomographic estimates of ventricular and sulcal cerebrospinal fluid volumes increased significantly in all sampled brain regions in normal aging and were vastly larger in AD than in normal aging. Furthermore, younger patients with AD had significantly greater cerebrospinal fluid volume enlargement than did older patients with AD compared with healthy controls of their age. When the AD group was divided on the basis of reported age at symptom onset, patients in the early-onset group (onset before age 65 years) were quantitatively more abnormal than and showed a different pattern of abnormality from the patients in the late-onset group. This onset difference was also evident in neuropsychological test performance.

CONCLUSIONS

This cross-sectional study revealed a number of converging findings that suggested greater abnormality in the early-onset than in the late-onset group of patients with AD. The possibility remains, however, that the two onset groups represent different stages along a continuum of pathologic changes.

Factors of the Wisconsin Card Sorting Test as measures of frontal-lobe function in schizophrenia and in chronic alcoholism

The purpose of this study was to examine the factor structure of the Wisconsin Card Sorting Test (WCST). The scores of 22 patients with schizophrenia, 20 patients with chronic alcoholism, and 16 normal control subjects were entered into a principal components analysis, which yielded three factors: Perseveration, Inefficient Sorting, and Nonperseverative Errors. WCST performance of seven patients with lesions invading the dorsolateral prefrontal cortex, available from another study, provided criterion validity for the Perseveration factor and, less strongly, for the Inefficient Sorting factor. Two patterns of performance characterized the three patient groups: the schizophrenic group and frontal lobe group had the highest Perseveration factor scores, whereas the alcoholic group had the highest Inefficient Sorting scores; the Nonperseverative Errors factor showed no significant group differences. Construct validity of these factors involved assessing, in all but the frontal group, the degree of overlap (convergent validity) and separation (discriminant validity) of each WCST factor with scores from tests of other cognitive functions. The convergent and discriminant validity of the Perseveration factor, but not the remaining two factors, received support only within the group of schizophrenic patients.

Brain gray and white matter volume loss accelerates with aging in chronic alcoholics: a quantitative MRI study

Magnetic resonance imaging (MRI) was used to study in vivo the brains of 49 patients with chronic alcoholism, 3 to 4 weeks post-withdrawal, and 43 normal healthy controls, all right-handed male veterans between the ages of 23 and 70 years. MRI scans were analyzed using a semi-automated procedure, which allowed the subcortical regions to be segmented into cerebrospinal fluid (CSF) and brain tissue and the cortical regions to be segmented into CSF, gray matter, and white matter. An age regression model was used to examine the effects of alcohol on brain structure, over and above that expected from the normal aging process. The alcoholics exhibited decreased tissue and increased CSF after correcting for aging. In the cortex, there was significant loss of both gray matter and white matter volume. In this sample of alcoholics, no particular cortical region was preferentially affected or spared. Furthermore, brain tissue volume loss increased with advanced age in the alcoholics. In this group of alcoholics there was no relationship between length of illness and age, i.e., the younger alcoholics had as heavy alcohol use histories as did the older alcoholics. Thus, the increased brain tissue loss with advanced age is interpreted as evidence for age-related increase in brain vulnerability to chronic alcohol abuse.

The contribution of constructional accuracy and organizational strategy to nonverbal recall in schizophrenia and chronic alcoholism

The Rey-Osterrieth complex figure was used to assess the separate influences of the constructional accuracy and the organizational strategy employed while copying the figure on the later, incidental recall of the figure. We tested a model, which hypothesized that subjects who copied the main framework of the figure holistically would be more likely to achieve good copy accuracy scores and to reproduce the figure more accurately at recall than subjects who used a piecemeal approach during copy. Subjects included 68 detoxified, chronic alcoholics (ALC), 28 patients with schizophrenia (SZ), and 69 normal control subjects (NCS). The results showed that the ALC and the SZ groups, on average, had lower accuracy and strategy scores at copy than did the NCS group, and furthermore, that the combined contributions of copy accuracy and copy strategy accounted for group differences at recall. A path analysis revealed that, for all three groups, copy strategy had a significant direct effect on copy accuracy. Moreover, copy accuracy and copy strategy made independent contributions to recall accuracy within the ALC and NCS groups; by contrast, within the SZ group, copy strategy made an independent contribution to recall performance but copy accuracy did not. These results suggest that (1) organizational strategy can influence constructional accuracy at both copy and recall; (2) copy accuracy and strategy have the potential to influence recall independently; and (3) the recall deficit in ALC could be attributed to abnormalities in both accuracy and strategy at copy, whereas in SZ it could be attributed only to strategy abnormalities. The deficits observed on the complex figure test in the ALC and SZ were primarily nonmnemonic and were related to ability in figure construction and organizational strategy.