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W Byne

Publications and source records attributed to W Byne.

At least 19 recordsLinked to original sources
PubMed2001

Thalamic activation during an attention-to-prepulse startle modification paradigm: a functional MRI study.

BACKGROUND: Prepulse inhibition (PPI) of the startle reflex reflects early stages of information processing and is modulated by selective attention. Animal models indicate medial frontal-thalamic circuitry is important in PPI modulation. We report data from the first functional magnetic resonance imaging (fMRI) study examining whether attending to or ignoring a prepulse differentially activates brain areas within this circuitry. METHODS: Ten healthy subjects received structural and functional MRI. During fMRI acquisition, subjects heard intermixed attended and ignored tones serving as prepulses to the startle stimulus. Regions of interest were traced on structural MRI and coregistered to fMRI images. RESULTS: Greater amplitude fMRI blood-oxygen-level-dependent response to attended than ignored PPI conditions occurred in the right thalamus, and bilaterally in the anterior and mediodorsal thalamic nuclei, whereas the startle-alone condition showed deactivation. In transitional medial cortex (Brodmann Area 32), which is involved in affective processing of noxious stimuli, the startle-alone condition elicited the greatest response, the attended-PPI condition showed the smallest response, and the ignored-PPI condition was intermediate. CONCLUSIONS: These findings extend animal models to humans by indicating thalamic involvement in the modulation of PPI. Further fMRI investigations may elucidate other key structures in the circuitry underlying normal and disordered modulation of PPI.

Adult↗
PubMed2001

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.

Adult↗
PubMed2001

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.

Adult↗
PubMed2000

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.

Adolescent↗
PubMed2000

Prevalence and correlates of parkinsonism in an institutionalized population of geriatric patients with chronic schizophrenia.

BACKGROUND: Geriatric patients with chronic schizophrenia are at increased risk for parkinsonism and cognitive impairment, but the relationship between the two has been insufficiently studied. OBJECTIVES: (1) To determine the prevalence of parkinsonism in a cohort of institutionalized geriatric patients with chronic schizophrenia (N=79). (2) To examine the relationship of parkinsonism to potentially relevant variables including cognitive functioning, positive and negative symptoms, sex, age, age at first hospitalization, psychopharmacological regimen and tardive dyskinesia (TD). METHOD: Tremor, rigidity and bradykinesia were rated on a five-point severity scale. Clinically significant parkinsonism was defined by the unambiguous presence of at least two of those signs. TD was assessed with the Modified Simpson Dyskinesia Scale. Schizophrenic symptoms were rated with the Positive and Negative Syndrome Scale, and cognitive functioning with the Mini-Mental State Examination and the Consortium to Establish a Registry for Alzheimer's Disease battery. RESULTS: The prevalence of parkinsonism was 19% and was significantly higher in women than in men. Age was a significant predictor of parkinsonism. Independent of age, bradykinesia was significantly correlated with MMSE, fluency and naming. Tremor, rigidity and medication status did not correlate with any cognitive variable assessed. Cognitive measures did not differ between subjects meeting and not meeting criteria for clinically significant parkinsonism. Rigidity and bradykinesia were significantly correlated with negative symptoms but no parkinsonism sign correlated with positive symptoms. Twelve subjects received ratings consistent with both TD and parkinsonism; however, no parkinsonian variable predicted the co-occurrence of TD. CONCLUSIONS: The present correlations suggest potential overlap among the neural substrates for bradykinesia, cognitive impairment and negative symptoms; however, further research is required to clarify that issue.

Age Distribution↗
PubMed1999

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.

Activities of Daily Living↗
PubMed1999

Three-dimensional analysis with MRI and PET of the size, shape, and function of the thalamus in the schizophrenia spectrum.

OBJECTIVE: In an exploration of the schizophrenia spectrum, the authors compared thalamic size, shape, and metabolic activity in unmedicated patients with schizophrenia and schizotypal personality disorder to findings in age- and sex-matched healthy control subjects. METHOD: Coregistered magnetic resonance imaging (MRI) and positron emission tomography scans were obtained in 27 schizophrenic patients, 13 patients with schizotypal personality disorder, and 32 control subjects who performed a serial verbal learning test during tracer uptake. After thalamus edges were outlined on 1.2-mm MRI scans, a radial warping program yielded significance probability mapping in three dimensions. RESULTS: Significance probability mapping (with resampling) identified an area in the region of the mediodorsal nucleus bilaterally with significantly lower relative metabolism in the schizophrenia group than in either the control or schizotypal personality disorder groups, which did not differ from each other. The three groups did not differ significantly in total thalamic volume in square millimeters or thalamic volume relative to brain volume. Shape analyses revealed that schizophrenic patients had significantly fewer pixels in the left anterior region, whereas patients with schizotypal personality disorder had significantly fewer pixels in the region of the right mediodorsal nucleus than did control subjects. CONCLUSIONS: Schizophrenic patients showed significant metabolism and shape differences from control subjects in selective subregions of the thalamus, whereas patients with schizotypal personality disorder showed only a difference in shape. Because the mediodorsal and anterior nuclei have different connections with limbic and prefrontal structures, the anterior thalamic shrinkage and mediodorsal metabolic and shape changes might relate to the different clinical pictures in schizotypal personality disorder and schizophrenia.

Adult↗
PubMed1998

The medial preoptic and anterior hypothalamic regions of the rhesus monkey: cytoarchitectonic comparison with the human and evidence for sexual dimorphism.

Examination of thionin-stained sections through the hypothalamus of the rhesus monkey revealed nuclei that resemble the first, second and third interstitial nuclei of the anterior hypothalamus (INAH1-3) of the human. Volumetric analysis of these nuclei in a small sample of monkeys suggests that the nucleus that resembles INAH3 is larger in males than in females. INAH1-3 have each been reported to be larger in men than in women and each has been considered as a potential candidate for homology with the much-studied sexually dimorphic nucleus of the preoptic area (SDN-POA) of the rat. Positional and cytoarchitectonic criteria suggest that of these nuclei, INAH3 and its potential counterpart in the rhesus monkey are the best candidates for homology with the SDN-POA. While the criteria employed in the present study may be used to suggest homologies, they are not adequate to confirm them. Confirmation of the homologies suggested here must rely on other considerations such as connectivity, neurotransmitter and peptide content, and function. It is hoped that the present report will stimulate interest in further examinations of the rhesus hypothalamus that will test both the suggested homologies and the evidence for sexual dimorphism.

Animals↗
PubMed1998

Tardive dyskinesia in a chronically institutionalized population of elderly schizophrenic patients: prevalence and association with cognitive impairment.

BACKGROUND: Chronically hospitalized geriatric inpatients with schizophrenia are at particular risk for both tardive dyskinesia (TD) and cognitive impairment but have been insufficiently studied in this regard. Similarly, the relationship between TD and cognitive impairment has not be adequately addressed in this population. OBJECTIVES: (1) To determine the prevalence of TD in a cohort of chronically institutionalized schizophrenic geriatric inpatients. (2) To examine the relationship between the manifestations of TD in various body regions and several potentially related variables including current pharmacological regimen, age, age at first hospitalization and cognitive status. METHOD: TD was assessed by the Modified Simpson Dyskinesia Scale and cognitive status by the Mini-Mental State Examination (MMSE). The relationship between manifestations of TD and other variables was examined by t-tests, ANOVA, MANOVA and correlational analysis. RESULTS: The prevalence of TD was 60%. Prevalence increased with age but was not related to current antipsychotic or anticholinergic regimen. Mean MMSE score did not differ between groups of patients with and without TD as defined by the criteria of Schooler and Kane (1982); however, the mean MMSE score was significantly (p < 0.0004) lower in subjects with orofacial TD as defined by Waddington and Youssef (1996), and the difference was not entirely accounted for by the older age of the latter group. CONCLUSIONS: TD and cognitive impairment both increase with age. However, TD alone does not account for the severity of cognitive impairment in this population. The present study provides further support for the hypothesis that the correlation between TD and cognitive impairment holds primarily for the orofacial manifestations of TD.

Age Factors↗
PubMed1997

Ethical implications of scientific research on the causes of sexual orientation.

In this article, we evaluate the status of current biological research into sexual orientation and examine the relevance of such research on the legal and social status of gay men and lesbians. We begin with a review of hormonal neuroanatomical and genetic studies of sexual orientation. We argue that the scientific study of sexual orientation is, at best, still in its infancy. We turn then to the ethical and social implications of this research. We argue that even if scientists could explain how sexual orientation develops, no significant ethical conclusions would follow. Further, we suggest that the current emphasis on finding a biological basis for sexual orientation is potentially harmful to lesbians, gay men and other sexual minorities in various ways (although perhaps it is in some ways potentially helpful as well).

Animals↗
PubMed1997

Why we cannot conclude that sexual orientation is primarily a biological phenomenon.

While all mental phenomena must have an ultimate biological substrate, the precise contribution of biological factors to the development of sexual orientation remains to be elucidated. Does biology merely provide the slate of neural circuitry upon which sexual orientation is inscribed by experience? Do biological factors directly wire the brain so that it will support a particular orientation? Or do biological factors influence sexual orientation only indirectly, perhaps by influencing personality variables that in turn influence how one interacts with and shapes the environment as it contributes to the social relationships and experiences that shape sexual orientation as it emerges developmentally? Recent neurostructural and genetic linkage evidence pertaining to sexual orientation must be viewed tentatively until it has been adequately corroborated and integrated with psychological and cultural models. Moreover, even a reliable and robust correlation between a biological marker and sexual orientation would be equally compatible with the second and third possibilities delineated above. Yet if the third possibility more closely approximates reality, the search for predisposing biological factors will result in incomplete and misleading findings until their interactions with environmental factors are taken into account and controlled for in adequate longitudinal studies.

Animals↗
PubMed1995

Science and belief: psychobiological research on sexual orientation.

The dominant paradigm that generates support for biological theories of sexual orientation has profound conceptual flaws. Not only does it equate the motor patterns of copulation in rodents with sexual orientation in humans, it assumes that the brain regions that regulate these behaviors in rodents participate in governing sexual orientation in humans. Reports of sex differences in the rodent brain generate speculation concerning the existence of differences in the human brain associated not only with sex but also with sexual orientation. Thus, recent years have witnessed numerous attempts to demonstrate that the brains of homosexuals exhibit characteristics that are typical of the opposite sex. In some cases, these attempt have come decades after persuasive evidence suggested that the brain characteristic in question does not differ between the sexes in humans. If a particular feature on the human brain does not differ between men and women, the phrase "typical of the opposite sex" is meaningless. It is, then, illogical to argue-even from the perspective of the biologically deterministic paradigm-that the feature should be typical of the opposite sex in homosexuals. This paper analyzes the assumptions and evidence that support biologically deterministic theories of sexual orientation. It is concluded that support for these theories derives as much from their appeal to prevailing cultural ideology as from their scientific merit. This appeal may explain why seriously flawed studies pass readily through the peer review process and become incorporated rapidly into the biologically deterministic canon where they remain viable even when replication attempts repeatedly fail.

Animals↗
PubMed1993

Human sexual orientation. The biologic theories reappraised.

Recent studies postulate biologic factors as the primary basis for sexual orientation. However, there is no evidence at present to substantiate a biologic theory, just as there is no compelling evidence to support any singular psychosocial explanation. While all behavior must have an ultimate biologic substrate, the appeal of current biologic explanations for sexual orientation may derive more from dissatisfaction with the present status of psychosocial explanations than from a substantiating body of experimental data. Critical review shows the evidence favoring a biologic theory to be lacking. In an alternative model, temperamental and personality traits interact with the familial and social milieu as the individual's sexuality emerges. Because such traits may be heritable or developmentally influenced by hormones, the model predicts an apparent nonzero heritability for homosexuality without requiring that either genes or hormones directly influence sexual orientation per se.

Animals↗
PubMed1991

Alz-50 immunoreactivity in the hypothalamus of the normal and Alzheimer human and the rat.

Alz-50 is a monoclonal antibody recognizing a 68 kilodalton protein that is abundant in Alzheimer's disease (AD) but not detectable by immunoblotting methods in normal brains. When used for immunohistochemistry in AD cortex, Alz-50 recognizes large numbers of neurofibrillary tangles (NFT), neuritic plaques, and some neurons that show no evidence of neurofibrillary degeneration by conventional histopathological staining methods. Alz-50 immunoreactivity is described at the light and electron microscopic levels in the hypothalamus of brains obtained at autopsy from normal and AD subjects. Alz-50 immunoreactivity in the rat hypothalamus is also described. A well-defined population of Alz-50 immunoreactive hypothalamic neurons was identified in both the normal human and rat. At the light microscopic level in the normal human, immunoreactive neurons were most concentrated in the periventricular region, but were also scattered throughout the arcuate nucleus (ARC), lateral hypothalamic area, and tuberal region. Immunoreactive fibers were seen in the periventricular region, dorsal division of the ventromedial nucleus (VMNd), ARC, and external layer of the median eminence (ME). In the rat, reactive neurons were seen only in the periventricular region, and reactive fibers were seen in the periventricular zone, medial preoptic nuclear complex, suprachiasmatic nucleus, VMNd, ARC, and external layer of the ME. Ultrastructurally, all immunoreactivity in the normal human and rat hypothalamus was associated with intraneuronal vesicles. In the AD hypothalamus, Alz-50 identified numerous senile plaques and NFT in addition to the cells and fibers that were stained in the normal brains. Immunoreactive plaques and NFT were most numerous in regions previously reported to undergo neurofibrillary degeneration. At the ultrastructural level, the immunoreactivity in the AD hypothalamus was associated with filaments as well as vesicles. The significance of the selective staining of a specific population of vesicles by Alz-50 is unknown; however, the present results suggest that it is independent of AD pathology.

Aged↗
PubMed1988

Variations in human corpus callosum do not predict gender: a study using magnetic resonance imaging.

Controversy exists in the neuropsychological literature concerning the existence of gender-associated differences in cognitive functioning and in hemispheric lateralization of cognitive functions. A recent study, based on 14 brains obtained at autopsy, reported sex differences in the splenium of the human corpus callosum and suggested that the larger splenium in females reflects less hemispheric lateralization, or "specialization," than the male brain for visuospatial functions. Our measurements of the human corpus callosum using magnetic resonance images of 37 living subjects failed to confirm reported sex differences in the splenium. A marginally significant sex-related difference in minimum body width and an age-related decrease in anteroposterior distance were found. Most striking were the large variations in callosal size and shape among individuals regardless of age or gender. Existing knowledge of the functions of the corpus callosum does not permit correlations between variations in callosal size and shape and variations in cognitive functions.

Adolescent↗