Biomedical subjects

R M Bauer

Publications and source records attributed to R M Bauer.

At least 19 recordsLinked to original sources

PubMed2001

Basal ganglia dysfunction, working memory, and sentence comprehension in patients with Parkinson's disease.

To investigate the role of the basal ganglia in working memory and sentence comprehension, 14 patients with Parkinson's disease (PD) were administered experimental measures of semantic and phonological working memory, and a measure of sentence comprehension, while receiving dopaminergic medications and after a period of withdrawal from these medications. An age- and education- matched control group (N=14) received the same measures. Comparison with control subjects revealed deficits in patients with PD in sentence processing regardless of medication status, but no deficits in working memory. In contrast to previous studies, withdrawal of dopaminergic medications had no significant impact on task- related working memory functions or on sentence comprehension. Results suggest that basal ganglia dysfunction does not solely account for sentence comprehension deficits seen in PD.

Aged↗

PubMed2001

Unilateral vs. bilateral ultrasound in the monitoring of cerebral microemboli.

We used bilateral transcranial Doppler to monitor the number of microembolic events (ME) in the left and right middle cerebral arteries of 29 patients during cardiac surgery that required extracorporeal circulation. Based on a previously published study, we hypothesized that the commonly used method of doubling unilateral ME counts to obtain an estimated bihemispheric load would result in significant errors of estimation. In our sample, estimated bihemispheric counts were inaccurate by an average of 18% (range 0--80%). Despite this large range of error, calculation of Cronbach's alpha revealed that actual error due to unreliability (4%) was small relative to the large variation in ME counts across subjects in this patient series. These findings suggest that unilateral monitoring is sufficient when the goal is to characterize a given subject's ME load within the context of the other subjects in the sample. However, when precise ME counts are required, bilateral monitoring is essential.

Cardiac Surgical Procedures↗

PubMed2000

Electroencephalographic, volumetric, and neuropsychological indicators of seizure focus lateralization in temporal lobe epilepsy.

CONTEXT: Anterior temporal lobectomy is an effective treatment for medically intractable temporal lobe seizures. Identification of seizure focus is essential to surgical success. OBJECTIVE: To examine the usefulness of presurgical electroencephalography (EEG), magnetic resonance imaging (MRI), and neuropsychological data in the lateralization of seizure focus. DESIGN: Presurgical EEG, MRI, and neuropsychological data were entered, independently and in combination, as indicators of seizure focus lateralization in discriminant function analyses, yielding correct seizure lateralization rates for each set of indicators. SETTING: Comprehensive Epilepsy Program, Shands Teaching Hospital, University of Florida, Gainesville. PATIENTS: Forty-four right-handed adult patients who ultimately underwent successful anterior temporal lobectomy. Left-handed patients, those with less-than-optimal surgical outcome, and any patients with a history of neurological insult unrelated to seizure disorder were excluded from this study. MAIN OUTCOME MEASURES: For each patient presurgical EEG was represented as a seizure lateralization index reflecting the numbers of seizures originating in the left hemisphere, right hemisphere, and those unable to be lateralized. Magnetic resonance imaging data were represented as left-right difference in hippocampal volume. Neuropsychological data consisted of mean scores in each of 5 cognitive domains. RESULTS: The EEG was a better indicator of lateralization (89% correct) than MRI (86%), although not significantly. The EEG and MRI were significantly superior to neuropsychological data (66%) (P=.02 and .04, respectively). Combining EEG and MRI yielded a significantly higher lateralization rate (93%) than EEG alone (P<.01). Adding neuropsychological data improved this slightly (95%). CONCLUSIONS: The EEG and MRI were of high lateralization value, while neuropsychological data were of limited use in this regard. Combining EEG, MRI, and neuropsychological improved focus lateralization relative to using these data independently.

Adult↗

PubMed2000

Emotional and physiological responses to false feedback.

The relationship between autonomic-visceral arousal and emotional experience is unclear. The attribution or cognitive-arousal theory of emotional experience posits that emotional experience is dependent on both visceral-autonomic nervous system feedback and the cognitive interpretation of the stimulus that induced this visceral activation. The finding that false cardiac feedback can alter emotional experience suggests that it may be the conscious perception that one is aroused, together with the cognitive interpretation of the stimulus that are important in developing emotional experience. Because the right hemisphere appears to play a special role in modulating arousal and interpreting emotional stimuli, it is possible that right hemisphere damage may interfere with developing the computations needed for emotional experience. To test this hypothesis we exposed men, both neurologically intact and those with right and left hemisphere lesions, to emotionally provocative pictures that were paired with false cardiac feedback, and examined the effects of this false feedback on their ratings of attractiveness of these pictures and their cardiac reactivity to this information. Subjects with left hemisphere damage, but not right hemisphere damage, showed significant changes in their emotional rating whereas control subjects showed marginal reactivity in their emotional ratings. Subjects with left hemisphere damage also showed significant changes in their cardiac reactivity. This finding is consistent with prior reports that indicate, when compared to right hemisphere damaged patients and normal controls, patients with left hemisphere lesions have an increased visceral-autonomic response to stimuli. These findings further provide support for the postulate that it is the cognitive interpretation of perceived physiological arousal together with the cognitive interpretation of the stimulus that is important in the development of emotional judgment and experience. These results do not support the approach-left hemisphere/avoidance-right hemisphere dichotomy, but instead suggest that left hemisphere damage increases reactivity to false feedback, and that the intact right hemisphere function integrates the cognitive interpretation of the emotional information and perceived arousal that lead to that emotional judgment. That these subjects showed no consistent relationship between their measures of cardiac reactivity and their ratings of attractiveness detracts from the James-Lange and attribution theories. These subjects also showed no consistent relationship between their knowledge of affective physiological reactivity and their ratings of attractiveness, or between their knowledge of physiological reactivity and actual measures of cardiac reactivity, suggesting that other neuropsychological factors are involved in making an emotional judgment.

Aged↗

PubMed2000

Digitizing the moving face during dynamic displays of emotion.

Humans typically decode facial signals during dynamic interactions in which the face moves. In this study, we digitized real time video signals in order to examine movement asymmetries across the face during emotional and nonemotional expressions. Forty dextral males were tested. For each expression, a 400 ms video segment was analyzed for changes in signal value (pixel intensity) over consecutive frames. The upper and lower face regions were examined separately due to differences in the cortical enervation of facial muscles in the upper (bilateral) vs lower face (contralateral). Results revealed distinctly different movement asymmetries over the lower and upper hemiface. In the upper face, more movement occurred over the right side for most facial expressions, regardless of emotionality. The latter finding questions the assumption that muscles of the upper face are symmetrical and/or bilaterally enervated in a symmetrical manner. In the lower face, negative expressions linked to fight-flight emotions (i.e. fear, anger) were associated with greater left sided movement, whereas happiness tended to be associated with more right sided movement. No consistent pattern of movement asymmetry occurred for nonemotional expressions. Although the valence-related movement asymmetries in the lower face are consistent with neuropsychological models of emotional expressivity, it remains unclear whether they reflect activation or inhibitory hemispheric mechanisms. Taken together, these data suggest that multiple factors may contribute to expressive movement asymmetries of the face.

Adolescent↗

PubMed1999

Conduction aphasia and the arcuate fasciculus: A reexamination of the Wernicke-Geschwind model.

Wernicke, and later Geschwind, posited that the critical lesion in conduction aphasia is in the dominant hemisphere's arcuate fasciculus. This white matter pathway was thought to connect the anterior language production areas with the posterior language areas that contain auditory memories of words (a phonological lexicon). Alternatively, conduction aphasia might be induced by cortical dysfunction, which impairs the phonological output lexicon. We observed an epileptic patient who, during cortical stimulation of her posterior superior temporal gyrus, demonstrated frequent phonemic paraphasias, decreased repetition of words, and yet had intact semantic knowledge, a pattern consistent with conduction aphasia. These findings suggest that cortical dysfunction alone may induce conduction aphasia.

Aphasia, Conduction↗

PubMed1999

Left-hemisphere processing of emotional connotation during word generation.

Areas of the brain's left hemisphere involved in retrieving words with emotional connotations were studied with fMRI. Participants silently generated words from different semantic categories which evoked either words with emotional connotations or emotionally neutral words. Participants repeated emotionally neutral words as a control task. Compared with generation of emotionally neutral words, generation of words with emotional connotations engaged cortices near the left frontal and temporal poles which are connected to the limbic system. Thus, emotional connotations of words are processed in or near cortices with access to emotional experience.

Adolescent↗

PubMed1998

Physiologic measures of emotion.

This article has focused on a brief review of major psychophysiologic response measures in emotions research, and has attempted to acquaint the reader with basic findings and interpretive issues in this vast and rapidly growing research area. It seems clear that measures of autonomic, somatic motor, and central nervous system activity in emotion provide one perspective on a complex biopsychosocial domain. We have moved from believing that physiologic arousal is sufficient for emotional experience to believing in multiple response systems that interact in complex ways to produce emotional experiences and expressions. The past decade has seen significant advances in our understanding of what is indexed by such responses, and it is now evident that important aspects of the underlying cognitive structure of emotions is revealed through multiple physiologic response channels. Thus, an exciting new era in the psychophysiology of emotions has begun. What will the next decade bring? I believe that the major advances in the next 10 years will emerge through an emerging cognitive neuroscience of emotions that weds traditional psychophysiology, neuroscience, neuroimaging, and neuropsychology through the development of cross-platform technologies. For example, combined psychophysiologic and functional imaging investigations will shed new light on the neural generators for specific response channels. Standardized, parametrically defined emotional stimuli will gain widespread use and will speed progress through experimentation in multiple laboratories. Well-designed and theoretically driven psychophysiologic investigations of emotional responding will continue to play a central role in many of these advances, as they have in the last 50 years of emotion research.

Animals↗

PubMed1997

State-dependent learning in older and younger adults.

In this study state-dependent learning in younger and older adults was compared. State was manipulated by having participants rest or exercise for 5 min, followed by exposure to 3 learning trials of a 20-item word list. After a 20-min delay, participants engaged either in the congruent or in the incongruent activity followed by free-recall trial, cued-recall, and recognition tests. Heart rate, blood pressure, and self-report of distress measures verified that the experimental conditions influenced the participants' physiologic state, but the distracter tasks did not. There was no difference in learning that was due to initial exercise condition, but both age groups showed greater recall when state was congruent before learning and delayed recall. This replicates previous research in which consistent state-dependent learning effects in younger adults were found and supports research suggesting that older adults spontaneously use contextual information to facilitate recall. The demonstration of state-dependent learning in older adults is discussed as an example of implicit memory not affected by aging.

Adolescent↗

PubMed1996

4-Aminopyridine antagonizes saxitoxin-and tetrodotoxin-induced cardiorespiratory depression.

Antagonism of saxitoxin-and tetrodotoxin-induced lethality by 4-aminopyridine was studied in urethane-anesthetized guinea pigs instrumented for the concurrent recordings of medullary respiratory-related unit activities (Bötzinger complex and Nu. para-Ambiguus), diaphragmatic electromyogram, electrocorticogram, Lead II electrocardiogram, blood pressure, end-tidal CO2 and arterial O2/CO2/pH. The toxin (either saxitoxin or tetrodotoxin) was infused at a dose rate of 0.3 microgram/kg/min (i.v.) to produce a state of progressive cardiorespiratory depression. The animals were artificially ventilated when the magnitude of integrated diaphragm activities was reduced to 50% of control. Immediately after the disappearance of the diaphragm electromyogram, the toxin infusion was terminated, and 4-aminopyridine (2 mg/kg, i.v.) was administered. The therapeutic effect of 4-aminopyridine was striking in that the toxin-induced blockade of diaphragmatic neurotransmission, vascular hypotension, myocardial anomalies, bradycardia and aberrant discharge patterns of medullary respiratory-related neurons could all be promptly restored to a level comparable to that of control condition. The animals were typically able to breathe spontaneously within minutes after 4-aminopyridine. At the dose level used to achieve the desired therapeutic responses, 4-aminopyridine produced no sign of seizure and convulsion. Although less serious side-effects such as cortical excitant/arousal and transient periods of fascicular twitch could be observed, these events were of minor concern, in our opinion, particularly in view of the remarkable therapeutic effects of 4-aminopyridine.

4-Aminopyridine↗

PubMed1996

Quantified volumes of temporal lobe structures in patients with epilepsy.

The T1-weighted volumetric magnetic resonance images of 31 patients with intractable temporal lobe epilepsy, and 13 control subjects matched for age and sex, were subjected to semiautomated threshold analysis. The method used proved to be relatively fast and reliable. An index of temporal lobe interhemispheric asymmetry was extracted by thresholding high-signal (white matter) pixels. Patients had significantly more asymmetrical indices for white matter and hippocampal volumes that did control subjects, and the two indices were significantly correlated, providing evidence for the validity of the white matter index. Differences in both indices were consistent with decreased tissue on the side of the focus. In classification analyses a combination of these two indices correctly predicted the side of focus at a greater rate than did either used alone. Findings provide support for the hypothesis that seizure activity is associated with atrophy in both mesial and lateral temporal lobe structures.

Adult↗

PubMed1994

Selective attention and aphasia in adults: preliminary findings.

Thirteen patients with left-hemisphere stroke and history of aphasia and 13 normal controls were administered the covert orientation of visual attention task (COVAT). This task presents targets to the right or left of a central fixation point after a cue (84% of trials) or with no cue (16% of trials). Left-hemisphere damaged patients also received tests of language function at the time of the study. For targets presented 100 msec after cue onset, normal controls demonstrated equivalent responding for targets to the left and to the right of a central fixation point. Patients with left-hemisphere damage showed slower reaction times when responding to targets on the right as opposed to the left side of space when attention was first cued to the opposite side of space (invalid trials) or when attention was focused on a central fixation point (uncued trials), but they did not show slower reaction times on the right side when attention was first cued to the right (valid trials). For left-sided targets, no differences between valid, invalid, and uncued trials existed. Slower responding to right- as opposed to left-sided targets on invalid and uncued trials was correlated with impaired performance on six of seven language measures for patients with left-hemisphere damage. Implications for the relationship between language and selective attention systems in the left hemisphere are discussed.

Adult↗

PubMed1993

An excitatory amino acid synapse in the thoracic spinal cord is involved in the pressor response to muscular contraction.

The increase in arterial pressure and heart rate elicited during exercise are produced by descending central command and by feedback from contracting limb muscles. Previous studies from this laboratory have demonstrated that neurons in the ventrolateral medulla (VLM) that project to the intermediolateral (IML) columns of the thoracic spinal cord are involved in the mediation of the pressor response to contraction of hind limb muscles. This study determines if these VLM neurons utilize excitatory amino acids (EAA) as the neurotransmitter at the synapse on IML neurons. The arterial pressure and heart rate responses to static muscular contraction, elicited by stimulation of the L7 and S1 ventral roots, and to electrical stimulation in the caudal hypothalamus were examined in anesthetized cats. Both muscular contraction and hypothalamic stimulation elicited significant increases in arterial pressure and heart rate. Intrathecal administration of the broad spectrum, postsynaptic EAA antagonist, kynurenic acid, greatly reduced (-77%) the pressor response to muscular contraction. A smaller (-27%) decrease in the magnitude of pressor response elicited by muscular contraction was produced by intrathecal administration of 2-amino-4-phosphonobutyric acid which acts on a presynaptic EAA receptor. Neither antagonist affected the heart rate responses associated with muscular contraction or the cardiovascular responses to hypothalamic stimulation. These results indicate that the pressor response elicited by feedback from contracting hind limb muscles is mediated through an excitatory amino acid synapse in the spinal cord.

Amino Acids↗

PubMed1992

Effect of 1,1-dimethylhydrazine (UDMH) on Corynebacterium parvum-associated immunosuppression in mice.

These studies further investigate the immunoenhancement properties of UDMH by utilizing Corynebacterium parvum-induced immunosuppressed mice as well as evaluating activated macrophage production of reactive oxygen intermediates or their effects. Forty-eight hour Con A-induced lymphoblastogenic responses from splenocytes isolated from C. parvum and UDMH-treated Balb/C mice were significantly increased compared with C. parvum alone, although less than normal control mice (no treatment). In vitro bioassay of IL-2 production in cell culture supernatant isolated from these same treatment groups exhibited a pattern of stimulation similar to that of lymphocyte blastogenesis. In addition, UDMH did not interfere with H2O2-mediated suppression of either Con A- or LPS-induced lymphocyte blastogenesis and actually enhanced suppression of Con A-induced lymphocyte cultures at 25 micrograms/ml. We also report that production of superoxide anion from TPA-activated peritoneal macrophages exposed to various concentrations of UDMH in vitro was not affected. Although in vivo exposure to UDMH partially reversed C. parvum-induced immunosuppression in mice, the exact mechanism by which UDMH acts to reverse this immune suppression is not clear. UDMH does not appear to interfere with either activated peritoneal macrophage production of superoxide anion or H2O2-induced suppression of lymphocyte blastogenesis to elicit immune enhancement.

Animals↗

PubMed1992

Properties of ventrolateral medullary neurons that respond to muscular contraction.

Previous results from this laboratory have suggested that neurons in the ventrolateral medulla (VLM) modulate the pressor response to muscular contraction. The purpose of the present study was to determine 1) if VLM neurons with a discharge pattern related to sympathetic discharge and/or the cardiac cycle are stimulated during muscular contraction, 2) if the neurons activated by muscular contraction project to the intermediolateral columns of the spinal cord and 3) the location of glutamate immunoreactive neurons in the medulla. Single-unit responses of ventrolateral medullary neurons to hindlimb muscular contraction evoked by ventral root (L7 and S1) stimulation were recorded in one group of anesthetized cats. Computer analyses were performed to determine if the resting discharge of VLM neurons correlated temporally with sympathetic nerve discharge and/or the cardiac cycle. The discharge rate of 21 of 27 neurons which had a discharge related to sympathetic nerve activity increased during muscular contraction. Neurons in some of the experiments were tested for axonal projections to the intermediolateral nucleus (T2 or T5) of the spinal cord with antidromic activation techniques. The discharge pattern of 78% of the VLM neurons which were activated antidromically was related to the cardiac cycle or sympathetic nerve discharge. Most (92%) reticulospinal VLM neurons with cardiovascular related discharge were excited by muscular contraction. In a second set of experiments, glutamate immunoreactivity was demonstrated in neurons within an area overlapping the location of VLM neurons which were excited by muscular contraction. These findings suggest that reticulospinal neurons in the ventrolateral medulla which have a discharge pattern related to cardiovascular activity contribute to the pressor reflex evoked by muscular contraction. These neurons may utilize glutamate as a neurotransmitter.

Animals↗

PubMed1992

Behavioural and physiological evidence for covert face recognition in a prosopagnosic patient.

In a previous report, Bauer (1984) described the patient LF, who was unable to recognise familiar faces. Despite the inability to verbally identify familiar faces, psychophysiological examination revealed preserved covert processing of facial identity. Subsequent studies have demonstrated covert face recognition using behavioural tasks. Investigations of the patient PH showed normal face familiarity effects on matching, interference, priming, and learning tasks, while overt recognition was completely absent (De Haan, Young and Newcombe, 1987b). The use of different methodologies has led to different theoretical conceptualisation of the "covert recognition" phenomenon. Until now, no individual patient has been exposed to both methodologies. In this study we evaluated LF, who shows psychophysiological evidence of covert recognition, using behavioural tasks previously used with PH. The results reveal clear behavioural evidence of preserved face recognition without awareness. These findings suggest that both methodologies tap similar phenomena, and have important implications for theoretical models of covert face recognition. A conceptual model designed to integrate psychophysiological and behavioural evidence of covert face recognition is proposed.

Agnosia↗

PubMed1992

The role of psychological factors in the report of building-related symptoms in sick building syndrome.

Sick building syndrome (SBS) is an increasingly common problem, although continued skepticism exists regarding its validity. Because of this, the attribution of complaints to psychogenic causes or mas hysteria persists. In this study (N = 111), self-report measures of psychopathology (Minnesota Multiphasic Personality Inventory [Hathaway & McKinley, 1983] and SCL-90-R [Derogatis, 1983]) and physical symptom reports failed to discriminate symptomatic from nonsymptomatic workers in an affected building but could more generally differentiate workers in the target building from control subjects. These results suggest that SBS cannot be justifiably attributed to psychological factors alone, although working in a contaminated environment appeared to have deleterious psychological consequences for some workers. Smoking history (in pack/years [packs per day x number of years smoked]) was reliably associated with the development of symptoms in exposed workers. Issues related to the assessment of psychological complaints in SBS are discussed.

Air Pollution, Indoor↗

PubMed1992

A unique de novo interstitial deletion del(17)(q21.3q23) in a phenotypically abnormal infant.

We report on an infant with multiple congenital anomalies possessing a de novo, interstitially deleted no. 17 chromosome. The phenotype includes brachycephaly, club feet, delay of growth and development, and hypertelorism with upslanted palpebral fissures. We are unaware of other reported cases involving such interstitial deletion of 17, or of translocations involving the breakpoint regions observed in our case.

Abnormalities, Multiple↗