Postmortem assessment of thalamic nuclear volumes in subjects with schizophrenia

OBJECTIVE

The authors assessed schizophrenia-associated changes in volume and neuronal number in the mediodorsal nucleus and the pulvinar regions of the thalamus.

METHOD

Right-hemisphere thalami obtained at autopsy from 14 schizophrenic and eight comparison subjects were examined. Computer-assisted morphometric techniques were used to determine volumes for the mediodorsal nucleus, pulvinar, and the anterior and centromedian nuclei as well as the parvocellular, magnocellular, and caudodorsal subdivisions of the mediodorsal nucleus. Neurons in the mediodorsal nucleus and pulvinar were counted and measured by using a stereology-based sampling strategy.

RESULTS

Four schizophrenic and three comparison subjects had Alzheimer's type pathology, leaving 10 schizophrenic and five comparison subjects without other documented neuropathological changes. In analyses that included either the full cohort or only the subjects without Alzheimer's type pathology, volumes of the mediodorsal nucleus and pulvinar, but not the anterior or centromedian nuclei, were significantly smaller in the schizophrenic subjects. For the schizophrenic subjects, neuronal number in the mediodorsal nucleus, parvocellular subdivision, and pulvinar was significantly lower, and neuronal size in the mediodorsal nucleus, caudodorsal subdivision, and pulvinar was significantly smaller.

CONCLUSIONS

Schizophrenia is associated with volume and neuronal changes in the mediodorsal nucleus and pulvinar, the major association nuclei of the thalamus, whereas total thalamic volume and the volumes of anterior and centromedian nuclei were not significantly altered.

The thalamus and schizophrenia: current status of research

The thalamus provides a nodal link for multiple functional circuits that are impaired in schizophrenia (SZ). Despite inconsistencies in the literature, a meta analysis suggests that the volume of the thalamus relative to that of the brain is decreased in SZ. Morphometric neuroimaging studies employing deformation, voxel-based and region of interest methodologies suggest that the volume deficit preferentially affects the thalamic regions containing the anterior and mediodorsal nuclei, and the pulvinar. Postmortem design-based stereological studies have produced mixed results regarding volume and neuronal deficits in these nuclei. This review examines those aspects of thalamic circuitry and function that suggest salience to SZ. Evidence for anomalies of thalamic structure and function obtained from postmortem and neuroimaging studies is then examined and directions for further research proposed.

The interstitial nuclei of the human anterior hypothalamus: an investigation of variation with sex, sexual orientation, and HIV status

The interstitial nuclei of the human anterior hypothalamus (INAH1-4) have been considered candidates for homology with the sexually dimorphic nucleus of the preoptic area of the rat. Volumetric sexual dimorphism has been described for three of these nuclei (INAH1-3), and INAH3 has been reported to be smaller in homosexual than heterosexual men. The current study measured the INAH in Nissl-stained coronal sections in autopsy material from 34 presumed heterosexual men (24 HIV- and 10 HIV+), 34 presumed heterosexual women (25 HIV- and 9 HIV+), and 14 HIV+ homosexual men. HIV status significantly influenced the volume of INAH1 (8% larger in HIV+ heterosexual men and women relative to HIV- individuals), but no other INAH. INAH3 contained significantly more neurons and occupied a greater volume in presumed heterosexual males than females. No sex difference in volume was detected for any other INAH. No sexual variation in neuronal size or density was observed in any INAH. Although there was a trend for INAH3 to occupy a smaller volume in homosexual men than in heterosexual men, there was no difference in the number of neurons within the nucleus based on sexual orientation.

Magnetic resonance imaging of the thalamic mediodorsal nucleus and pulvinar in schizophrenia and schizotypal personality disorder

BACKGROUND

The importance of neuronal interactions in development, the cortical dependence of many thalamic nuclei, and the phenomenon of transsynaptic degeneration suggest possible abnormalities in thalamic nuclei with connections to other brain regions implicated in schizophrenia. Because frontal and temporal lobe volumes are diminished in schizophrenia, volume loss could characterize their primary thalamic relay nuclei (mediodorsal nucleus [MDN] and pulvinar).

METHODS

Tracers delineated the thalamus, MDN, and pulvinar on contiguous 1.2-mm magnetic resonance images in 12 schizophrenic patients, 12 with schizotypal personality disorder (SPD), and 12 normal control subjects. The MDN and pulvinar were rendered visible by means of a Sobel intensity-gradient filter.

RESULTS

Pixel overlap for delineation of all structures by independent tracers was at least 80%; intraclass correlations were r = 0.78 for MDN and r = 0.83 for pulvinar. Pulvinar volume was smaller in schizophrenic (1.22 +/- 0.24 cm(3)) and SPD (1.20 +/- 0.23 cm(3)) patients than controls (1.37 +/- 0.25 cm(3)). Differences for MDN were not statistically significant; however, when expressed as percentage of total brain volume, pulvinar and MDN together were reduced in SPD (0.14%) and schizophrenic (0.15%) patients vs controls (0.16%). Reductions were more prominent in the left hemisphere, with MDN reduced only in the schizophrenic group, and pulvinar in both patient groups. Total thalamic volume did not differ among the 3 groups.

CONCLUSIONS

Measurement of MDN and pulvinar in magnetic resonance images is feasible and reproducible. Schizophrenic and SPD patients have volume reduction in the pulvinar, but only schizophrenic patients show reduction relative to brain volume in MDN.

D2/D3 dopamine receptor binding with [F-18]fallypride in thalamus and cortex of patients with schizophrenia

BACKGROUND

Abnormalities in the dopaminergic system are implicated in schizophrenia. [F-18]fallypride is a highly selective, high affinity PET ligand well suited for measuring D2/D3 receptor availability in the extrastriatal regions of the brain including thalamus, prefrontal, cingulate, and temporal cortex, brain regions implicated in schizophrenia with other imaging modalities.

METHODS

Resting [F-18]fallypride PET studies were acquired together with anatomical MRI for accurate coregistration and image analysis on 15 drug naïve schizophrenics (10 men, 5 women, mean age 28.5 years) and 15 matched controls (9 men, 6 women, mean age 27.4 years). Dopamine D2/D3 receptor levels were measured as binding potential (BP). The fallypride BP images of each subject were spatially normalized and subsequently smoothed for group comparison. Measures of significance between the schizophrenic and control groups were determined using statistical parametric mapping (SPM). The medial dorsal nucleus and pulvinar were also traced on coregistered MRI for detailed assessment of BP in these regions.

RESULTS

The thalamus of patients with schizophrenia had lower [F-18]fallypride BP than normal controls and this was the brain area with the greatest difference (range -8.5% to -27.2%). Left medial dorsal nucleus and left pulvinar showed the greatest decreases (-21.6% and -27.2% respectively). The patients with schizophrenia also demonstrated D2/D3 BP reduction in the amygdala region, cingulate gyrus, and the temporal cortices.

CONCLUSIONS

These findings suggest that drug naïve patients with schizophrenia have significant reductions in extrastratial D2/D3 receptor availability. The reductions were most prominent in regions of the thalamus, replicating other studies both with high affinity D2/D3 ligands and consistent with FDG-PET studies, further supporting the hypothesis of thalamic abnormalities in this patient population.

Abnormal glucose metabolism in the mediodorsal nucleus of the thalamus in schizophrenia

OBJECTIVE

Three thalamic nuclei--the mediodorsal nucleus, pulvinar, and centromedian nucleus--each have unique reciprocal circuitry with cortical and subcortical areas known to be affected in schizophrenia. To determine if the disorder is also associated with dysfunction in the mediodorsal nucleus, pulvinar, and centromedian nucleus, relative glucose metabolism in these regions was measured in a large group of unmedicated patients with schizophrenia.

METHOD

[18F]-deoxyglucose positron emission tomography (PET) and matching T1-weighted magnetic resonance imaging (MRI) scans were obtained for 41 unmedicated patients with schizophrenia and 60 age- and sex-matched healthy subjects. The PET and MRI images for each subject were coregistered, and the whole thalamus, mediodorsal nucleus, pulvinar, and centromedian nucleus were traced on the MRI image. Relative glucose metabolism in these regions was assessed.

RESULTS

Patients with schizophrenia showed significantly lower relative glucose metabolism in the mediodorsal nucleus and the centromedian nucleus and significantly higher relative glucose metabolism in the pulvinar, compared with the healthy subjects. Lower relative glucose metabolism in the total thalamus, mediodorsal nucleus, and pulvinar was associated with greater overall clinical symptoms as measured by the Brief Psychiatric Rating Scale. Lower relative glucose metabolism in the pulvinar was associated with more hallucinations and more positive symptoms, while lower relative glucose metabolism in the mediodorsal nucleus was associated with more negative symptoms.

CONCLUSIONS

The findings suggest that patients with schizophrenia exhibit dysfunction in thalamic subdivisions with distinct cortical connections and that these thalamic subdivisions have specific associations with clinical symptoms.

Guanfacine treatment of cognitive impairment in schizophrenia

Norepinephrine plays a significant role in the working memory functions of the prefrontal cortex by its actions at alpha-2a noradrenergic receptors. Guanfacine has demonstrated efficacy in reversing working memory deficits in non-human primate. In the present study the effect of guanfacine adjunctive treatment to neuroleptics on the cognitive performance of schizophrenic patients was investigated in a four week, placebo-controlled, double-blind, parallel design trial. The primary analyses revealed no significant differences between guanfacine and placebo treatment; however, exploratory non-parametric statistics revealed some significant and some trend differences between guanfacine and placebo on spatial working memory test performance and CPT reaction time in those subjects treated with atypical neuroleptics.

The interstitial nuclei of the human anterior hypothalamus: an investigation of sexual variation in volume and cell size, number and density

The four interstitial nuclei of the anterior hypothalamus (INAH) have been considered as candidate human nuclei for homology with the much studied sexually dimorphic nucleus of the preoptic area of the rat. Assessment of the INAH for sexual dimorphism has produced discrepant results. This study reports the first systematic examination of all four INAH in the human for sexual variation in volume, neuronal number and neuronal size. Serial Nissl-stained coronal sections through the medial preoptic area and anterior hypothalamus were examined from 18 males and 20 females who died between the ages of 17 and 65 without evidence of hypothalamic pathology or infection with the human immunodeficiency virus. A computer-assisted image-analysis system and commercial stereology software package were employed to assess total volume, neuronal number and mean neuronal size for each INAH. INAH3 occupied a significantly greater volume and contained significantly more neurons in males than in females. No sex differences in volume were detected for any of the other INAH. No sexual variation in neuronal size or packing density was observed in any nucleus. The present data corroborate two previous reports of sexual dimorphism of INAH3 but provide no support for previous reports of sexual variation in other INAH.

Correlations between ventricular enlargement and gray and white matter volumes of cortex, thalamus, striatum, and internal capsule in schizophrenia

Ventricular enlargement is one of the most consistent abnormal structural brain findings in schizophrenia and has been used to infer brain shrinkage. However, whether ventricular enlargement is related to local overlying cortex and/or adjacent subcortical structures or whether it is related to brain volume change globally has not been assessed. We systematically assessed interrelations of ventricular volumes with gray and white matter volumes of 40 Brodmann areas (BAs), the thalamus and its medial dorsal nucleus and pulvinar, the internal capsule, caudate and putamen. We acquired structural MRI ( patients with schizophrenia (n = 64) and healthy controls (n = 56)) and diffusion tensor fractional anisotropy (FA) (untreated schizophrenia n = 19, controls n = 32). Volumes were assessed by manual tracing of central structures and a semi-automated parcellation of BAs. Patients with schizophrenia had increased ventricular size associated with decreased cortical gray matter volumes widely across the brain; a similar but less pronounced pattern was seen in normal controls; local correlations (e.g. temporal horn with temporal lobe volume) were not appreciably higher than non-local correlations (e.g. temporal horn with prefrontal volume). White matter regions adjacent to the ventricles similarly did not reveal strong regional relationships. FA and center of mass of the anterior limb of the internal capsule also appeared differentially influenced by ventricular volume but findings were similarly not regional. Taken together, these findings indicate that ventricular enlargement is globally interrelated with gray matter volume diminution but not directly correlated with volume loss in the immediately adjacent caudate, putamen, or internal capsule.

Thalamic transcriptome screening in three psychiatric states

The prefrontal cortex has been implicated in schizophrenia (SZ) and affective disorders by gene expression studies. Owing to reciprocal connectivity, the thalamic nuclei and their cortical fields act as functional units. Altered thalamic gene expression would be expected to occur in association with cortical dysfunction. We screened the expression of the entire human genome of neurons harvested by laser-capture microdissection (LCM) from the thalamic primary relay to dorsolateral prefrontal cortex in three psychiatric disease states as compared with controls. Microarray analysis of gene expression showed the largest number of dysregulated genes was in SZ, followed by major depression (MD) and bipolar mood bipolar (BP) (1152, 385 and 288, respectively). Significantly, IGF1-mTOR-, AKT-, RAS-, VEGF-, Wnt- and immune-related signaling, eIF2- and proteasome-related genes were unique to SZ. Vitamin D receptor and calcium signaling pathway were unique to BP. AKAP95 pathway and pantothenate and CoA biosynthesis were unique to MD. There are significant differences among the three psychiatric disorders in MDNp cells. These findings offer new insights into the transcriptional dysregulation in the thalamus of SZ/BP/MD subjects.

Cognitive and functional changes with aging in schizophrenia

The variation in functional outcome in schizophrenia appears to be exaggerated in late life. The cognitive and functional deficits commonly seen in younger schizophrenic patients appear to worsen in some cases in late life, while others patients appear to have a stable course of illness without functional decline, and still other patients have been reported to have essentially no residual symptoms in their later years. Cognitive and functional deficits appear to worsen more significantly in patients with a lifetime course of severe functional deficit. Despite the profound functional and cognitive deficits in these patients, neuropathologic studies have found no evidence of typical causes of severe cognitive impairments. This paper reviews the current findings on cognitive and functional changes in aging in schizophrenia, with a specific focus on patients with a poor lifetime functional outcome.