Neural mechanisms of emotion

When viewed from an evolutionary perspective, the neural mechanisms of emotion can be seen to be distributed across the brainstem, limbic, paralimbic, and neocortical regions. Descending and ascending connections among these levels are discussed in relation to three types of emotional processes: peripheral effects on patterned bodily responses, central effects on cognitive processing, and subjective emotional experience. Descending influences from the higher to the lower levels allow for an increasing coordination and flexibility of emotional responses, culminating in patterned activity across the peripheral endocrine, autonomic, and motor systems. Ascending influences from lower to higher levels provide preparatory modulation of cortical pathways, thus enabling perceptual and cognitive processing that is adaptive given the current emotional state. The bodily feelings of emotion are a function of cortical interoceptive sensory fields, activated by centrally generated signals or peripheral inputs from the body.

A Cognitive-Anatomical Approach to Attention in Lexical Access

Recent PET studies have suggested a specific anatomy for feature identification, visual word forms and semantic associations. Our studies seek to explore the time course of access to these systems by use of reaction time and scalp electrical recording. Target detection times suggest that different forms of representation are involved in the detection of letter features, feature conjunctions (letters), and words. Feature search is fastest at the fovea and slows symmetrically with greater foveal eccentricity. It is not influenced by lexicality. Detecting a letter case (conjunction) shows a left to right search which differs between words and consonant strings. Analysis of scalp electrical distribution suggest an occipito-temporal distribution for the analysis of visual features (right sided) and for the visual word form discrimination (left sided). These fit with the PET results, and suggest that the feature related analysis begins within the first 100 millisec and the visual word form discriminates words from strings by about 200 msec. Lexical decision instructions can modify the computations found in both frontal and posterior areas.

Molybdenum target x-ray spectra: a semiempirical model

A semiempirical model for generating molybdenum target x-ray spectra is presented. The model is an extension of a previous model developed by the authors for tungsten and takes into account the depth of production for both bremsstrahlung and characteristic x-ray photons. As in the previous work, the optimal model parameters were determined using nonlinear least-squares fits to experimental data. Good agreement between the two was obtained. By varying target angle, off-axis angle, and filtration in the model in accordance with the x-ray tube and geometry of interest, results consistent with tabulated spectra for different conditions have been obtained.

Spectral dependence of glandular tissue dose in screen-film mammography

The average glandular tissue dose in mammography is generally determined from published tables with knowledge of the breast entrance skin exposure, x-ray tube target material, beam quality (half-value layer [HVL]), breast thickness, and breast composition. Using a carefully designed and experimentally validated Monte Carlo simulation, the authors found that average glandular dose also depends on x-ray tube voltage and, to a lesser extent, on x-ray tube voltage waveform. For currently employed molybdenum target-molybdenum filter source assemblies, a difference in dose of 10% or more is possible in estimating the average glandular dose obtained with different x-ray tube voltages but with the same HVL. Presented are normalized average glandular tissue doses in units of radiation absorbed dose per unit entrance skin exposure for different tube voltages and tube voltage waveforms as well as for different breast thicknesses and compositions and beam filtrations.

Semiempirical model for generating tungsten target x-ray spectra

A semiempirical model for generating tungsten target x-ray spectra is presented. This model extends earlier work in two significant areas. First, both bremsstrahlung and characteristic x-ray production are assumed to occur at varying depths within the target. Second, optimal parameters for the model were determined from experimental spectra utilizing nonlinear least-squares techniques. As a result, good agreement is obtained between calculated and measured x-ray tube spectra and output for different target angles and a wide range of x-ray tube potentials. Such is not the case with previously published models.

A patient monitoring system designed as a platform for application development

This paper presents a patient data monitoring system for use in critical care areas. The system incorporates design criteria from the Institute of Electrical and Electronic Engineers' (IEEE) proposed standards body (P1073), the Medical Information Bus (MIB) and from our design team. Existing hardware and software technology is utilized wherever possible to maintain cost effectiveness. A major design objective is providing a consistent environment in which to develop applications for critical patient care delivery. The system allows applications to be developed without specific knowledge of the configuration of the bedside environment. Therefore, investments in 'user' application development are shielded from changes in patient care delivery technology. The system has been in limited operation in a surgical intensive care unit for several months with prototype applications.

Nutrition status and brain function in aging

Biochemical indices of nutrition status assessed in 28 healthy persons aged greater than 60 y were related to cognitive performance and electroencephalographic (EEG) indices of neuropsychological function. Performance data were most frequently related to indices of nutrition status when tasks were demanding. Numerous correlations were also found between EEG indices and indices of thiamin, riboflavin, and iron nutriture. Certain observations, such as a decrement in alpha-wave activity in the EEG of subjects with low thiamin status, suggest that subtle neuropsychological impairment can occur in association with mild deficits in nutrition status. Other findings indicate that EEG frequency responses of older subjects with high iron status are similar to those of younger persons; however, these data are more difficult to interpret. The results suggest that further research on nutrition and neuropsychological function will lead to a better understanding of the role of nutrition in maintaining the functional integrity of the aging brain.

Clinical assessment of tactile extinction: traditional double simultaneous stimulation versus quality extinction test

The clinical assessment of tactile extinction is reviewed. The traditional or classical methods of double simultaneous stimulation (DSS) are compared/contrasted with the more recent Quality Extinction Test (QET). Various case studies are used to demonstrate the greater sensitivity of the QET over traditional DSS methods in detecting cerebral pathology. Clinical implications are discussed.

Right-sided facial asymmetry in infant emotional expression

In normal adults, emotional expressions tend to be more intense on the left side of the face, while in preschool-age children, no significant bias in facial asymmetry has been found. We examined facial asymmetries during smiling and distress in 59 infants studied longitudinally at 6.5, 10 and 13.5 months of age. In these infants, asymmetric expressions showed a bias toward greater intensity on the right side of the face. The study of infant facial expression may provide clues to the maturation of the cortical control of emotional responses.

Memory dysfunction following unilateral transection of the fornix: a hippocampal disconnection syndrome

This study presents a case with a discrete nondischarging lesion of the left fornix that resulted in a marked anterograde memory deficit that was defined by the same material, modality and methodologically specific features characteristic of unilateral lesions of the hippocampus. Since the fornix is the major efferent pathway of the hippocampus to the mamillary bodies, septal nuclei and anterior thalamic nuclei, this patient could be considered to have a hippocampal disconnection syndrome.

Memory dysfunction in myasthenia gravis: evidence for central cholinergic effects

Two studies are presented that investigate the possible central cholinergic effects of myasthenia gravis as measured by cognitive dysfunction. In the first study, performance on a battery of cognitive tasks by 12 subjects with myasthenia gravis is compared with that of ten healthy control subjects and ten medical control subjects with chronic disease of a nonneurologic nature. The tests used were the Boston Naming Test, Rey Auditory Verbal Learning Test (AVLT), and the Logical Memory and Design Reproduction portions of the Wechsler Memory Scale (WMS). Results indicate that the myasthenic group was significantly impaired relative to both the medical and healthy control groups for performance on the Boston Naming Test, WMS Logical Memory, and WMS Design Reproduction. Both the myasthenic and the medical control groups were impaired relative to the healthy controls on the AVLT. In the second study, a myasthenic patient had plasmapheresis for treatment of her myasthenia on two separate occasions. Her memory was examined prior to as well as following each series of plasma exchanges with a variation of the Peterson-Peterson consonant trigram task. Results showed that this patient had significantly fewer interference effects and less rapid forgetting following plasmapheresis. The results of these two studies support the hypothesis that myasthenia gravis has central cholinergic effects manifested by cognitive dysfunction.

MMPI indices in the identification of patients evidencing pseudoseizures

Data are presented on the clinical utility of two Minnesota Multiphasic Personality Inventory (MMPI) indices, the Pseudo-Neurologic (Pn) Scale developed by Shaw and Matthews and the configural rule system developed by Wilkus et al. for the prediction of pseudoseizures. Particular attention is given to base rates, hit rates, and error rates in the analyses. Only the configural rule system was found to be of clinical value in ruling out the probability of pseudoseizures.

Hyperreligiosity in temporal lobe epilepsy: redefining the relationship

Seventy-six subjects with the primary diagnosis of complex partial seizures with a unilateral temporal lobe focus were examined for the presence of hyperreligiosity. Fifty-one subjects had a left temporal lobe seizure focus and 25 had a right temporal lobe seizure focus. In addition to the temporal lobe epilepsy (TLE) groups, two reference groups were also examined. The first consisted of 31 subjects with primary generalized seizures. The second control group consisted of 27 subjects with documented pseudoseizures and no objective evidence of recurrent epileptic seizures. In all cases, the documentation of seizures or pseudoseizures as well as the localization of the seizure focus was accomplished through simultaneous videotaped recording of the 16-channel scalp EEG tracing and the concurrent overt behavior during the ictal phase. The results of this study fail to support the hypothesis that individuals with TLE are characteristically hyperreligious during the interictal state. There were no significant group differences between the left vs. the right TLE groups, nor were there any significant group differences between the two TLE groups vs. the two comparison groups.

Hormone and energy substrate changes during prolonged exercise in the heat

Eleven trained men (aged 34.5 +/- 2 yrs) were studied during a 16.1 km run in the heat (Ta = 30.2 degrees C). Fasting blood samples were taken prior to the run and at 6.4, 12.9, and 16.1 km, and 3 h recovery. Serum or plasma glucose, insulin, glucagon, glycerol, and catecholamines were measured. Mean values were: exercise intensity, 80% of VO2max; final rectal temperature, 39.9 degrees C; and weight loss, 4.0%. Glucose increased 61% by 6.4 km, then decreased significantly by 16.1 km. Glycerol increased by 415% at 6.4 km, and continued to increase throughout the run. Epinephrine increased progressively during the run, but norepinephrine increased at 6.4 km, and did not change further during the exercise. Insulin increased slightly at 6.4 km, then decreased significantly from 6.4-16.1 km. Glucagon increased from 6.4-12.9 km and remained elevated at 3 h recovery. Hormone and substrate measurements obtained only before and after prolonged exercise may not reflect changes that occur during the course of the exercise. The observed insulin-glucagon relationships vary from previous findings in nontrained subjects at lower exercise intensities.

Functional connections among cortical regions: topography of EEG coherence

The covariance among EEG signals can be examined with coherence analysis. Evidence that the right hemisphere has a more diffuse receptotopic organization than the left, together with evidence that it may have a higher proportion of white to gray matter, suggests a high degree of functional connectedness among right hemisphere regions. To determine whether this is reflected in greater EEG coherence among right than left hemisphere locations, we constructed a matrix of cross-spectra among all unique pairs of EEG channels in an 8-channel montage, then statistically de-structured this matrix to examine multiple coherences and both inter- and intra-hemispheric partial multiple coherences. Analyses on data from the resting EEGs of 14 right-handed men examined weekly for several months showed higher coherences for right hemisphere locations. For the inter-hemispheric partial multiple coherences the frontal lobe values were also higher on the right, but the occipital inter-hemispheric coherences were higher on the left. These asymmetries have interesting parallels with anatomical asymmetries of the human cortex and may have functional implications.

Effects of simultaneous vs sequential stimulus presentation on memory performance following temporal lobe resection in humans

This study examines the differential effects of simultaneous vs sequential stimulus presentation on performance of a visuo-spatial memory task in patients following unilateral temporal lobectomy for relief of complex-partial seizures. Eleven subjects with surgical resection of the left temporal lobe, 13 subjects with surgical resection of the right temporal lobe, and 12 normal controls were examined. Results indicate that both the Right and the Left surgical groups were impaired on the visuo-spatial memory task employed. Further, the Right resection group was significantly more impaired for the recall of stimuli presented in the sequential condition as compared to the simultaneous condition.

Plasma volume changes in middle-aged male and female subjects during marathon running

Circulatory fluid shifts were studied in middle-aged runners (6 males and 5 females, ages 32-58 yr) during a 42.2-km marathon race run in mild weather (dry-bulb temperature = 17.5-20.4 degrees C). Running times for the subjects were 3:12-4:40 (mean values were 3:34 for males and 4:10 for females). Venous blood samples were taken without stasis in all subjects seated at rest before the start of the race and within 3 min of finishing; eight of the subjects also paused for samples at 6 and 27 km during the race. At 6 km, body weight loss averaged less than 1%, whereas plasma volume (PV) had decreased by 6.5% in male subjects and 8.6% in female subjects. By the end of the race, hypohydration had reached 3.2% in male subjects and 2.9% in female subjects, but PV in both groups remained stable. Sweat rates during the race averaged 545 and 429 g X m-2 X h-1 for male and female subjects, respectively, with ad lib. water intake replacing 21-72% of fluid loss. Increases in plasma protein concentration throughout the race reflected the observed initial decrease in PV. The interpretation of PV responses to exercise and/or hypohydration is critically dependent on selection of base-line conditions; we were able to control for posture-exercise effects by treating the early exercise (6 km) sample as the base line for examining the effects of later fluid loss. Under these conditions, the vascular compartment resisted volume depletion. The ability to maintain stable PV can be explained in part by relationships among oncotic and hydrostatic pressures in the intra- and extravascular fluid compartments.

Regional changes in EEG power and coherence during cognition: intensive study of two individuals

Two men underwent weekly electroencephalogram (EEG) recordings while living for several months in a controlled laboratory environment. Data collected from an eight-channel EEG during a resting period and during performance of two cognitive tasks (word fluency and mental imagery) were subjected to spectral analysis. Statistical analyses on power and coherence were conducted for each subject separately, to determine whether that individual showed a characteristic pattern of EEG activity for a given cognitive task which was stable over time. Although substantial individual differences were observed, particularly for the theta band, both subjects showed changes in the spectral information over the anterior left hemisphere during the word fluency task.

Lateral brain function in normal and disordered emotion: interpreting electroencephalographic evidence

Given the developing awareness of the lateral specialization of the human brain for both cognitive and emotional processes, the recent findings of characteristic hemispheric asymmetries in psychopathological groups suggests a neuropsychological model may be explanatory for abnormal psychology. Since the activity of arousal systems of the brain is a primary issue in interpreting both biochemical abnormalities and thought disorders in psychopathology, electroencephalographic (EEG) measures of cortical arousal are relevant. A better understanding of the relation of EEG measures to normal emotional arousal and cognitive effort may facilitate interpretation of the functional significance of EEG asymmetries in psychopathology.

Asymmetric cognitive function in anorexia nervosa

Three anorexics, one at normal weight, were examined, with a neuropsychological battery including the Halstead-Reitan tests. Their data were contrasted with that of 24 psychiatric controls matched for age, sex and IQ. Individually and as a group the anorexics showed above average verbal/academic scores and impaired spatial skills, whereas visual-motor and problem solving skills were equivalent to controls. Somatosensory recognition was impaired bilaterally in all three patients, and motor skills were low in the two emaciated patients. Other sensory tests and intermanual comparisons of sensory and motor skills were not impaired relative to controls. The findings suggest that a spatial reasoning deficit may be a predisposing or maintaining factor in this disorder. High verbal skills, in contrast, may reflect substantial left hemisphere contributions to the anorexic's cognitive style.

Asymmetric EEG changes as method actors generated emotions

Nine method actors recalled personal experiences to create emotional states of sexual arousal or depression. Electroencephalographic (EEG) data recorded from left and right frontal, central, parietal and occipital locations were spectrally analyzed for power in each major frequency band and for coherence among all pairs of channels. Contrasts between the emotion conditions showed less alpha power (greater activation) over the right hemisphere for sexual arousal than for depression. Analysis of coherence topography showed higher coherence in right central and posterior regions during the sexual arousal condition. These data are consistent with previous evidence of right hemisphere contribution to sexual arousal and suggest further that asymmetric patterns of brain activity may be associated with specific emotional states.