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PubMed2002

Effects of laughing and weeping on mood and heart rate variability.

We investigated the effects of laughing and weeping induced by watching comedy and tragedy videos on mood and autonomic nervous function. Ten healthy female subjects volunteered for the experiment. Chest electrocardiogram and respiration curve were recorded before, after, and during watching a comedy or a tragedy video. We also asked them to fill out profiles of mood states (POMS) to evaluate their mood states while watching videos. Autonomic nervous function was estimated by spectral analysis of heart rate variability (HRV). All subjects more or less laughed and wept while watching comedy and tragedy videos, respectively. Anger-hostility score of the POMS decreased and vigor score increased significantly after watching comedy videos, while depression-dejection score increased significantly after watching tragedy ones. Although both contents tended to increase a low to high frequency component ratio (LF/HF ratio) of HRV, the time course of responses was different. The LF/HF ratio which reflects cardiac sympathovagal balance increased immediately after they started watching comedy videos, and returned to the basal level right after they stopped watching, whereas the LF/HF ratio increased gradually to a lesser extent while watching tragedy videos. In contrast, the high-frequency component which reflects cardiac parasympathetic nerve activity gradually decreased while watching both videos but did not return to the basal level after watching tragedy ones. These results suggest that laughing has strong but transient effects on the autonomic nervous system, while weeping or feeling sad has moderate but sustained effects on it.

Adult↗
PubMed1993

Spontaneous cellular vibrations in the guinea-pig temporal-bone preparation.

Mechanical vibrations of Hensen cells were measured with a laser-heterodyne interferometer in the guinea-pig temporal-bone preparation without the application of an external acoustic stimulus. Smoothed periodograms (spectral-density estimates v. frequency) were constructed from the velocity v. time waveforms recorded from individual cells. Several peaks were seen in the periodograms at levels as high as 10 dB above the noise floor, indicating the presence of spontaneous vibrations. The frequencies at which the peaks were located differed in different preparations, indicating that the observed peaks were not caused by the presence of ambient noise or ambient vibrations. Furthermore, vibrations were seen only in fresh preparations. The tuning curves of cells from which spontaneous vibrations were measured (determined by applying an external stimulus to the ear) had single principal peaks. Several peaks in the periodogram were found to be located within the principal-peak region of the tuning curve. The spontaneous response does not arise from noise filtered through the tuning curve which would have a single peak. We propose that these spontaneous vibrations originate at the outer hair cells and are the source of spontaneous otoacoustic emissions in the ear.

Animals↗
PubMed2000

Effect of verapamil on baroreflex sensitivity and on cardiovascular variability.

OBJECTIVE: Epidemiological evidence indicates that depressed baroreflex sensitivity and heart rate variability are associated with reduced survival secondary to coronary heart disease as well as with an increased risk of developing coronary heart disease. In view of the conflicting data in the literature concerning the effect of calcium channel antagonists on autonomic balance, we evaluated the effect of verapamil on heart rate and blood pressure variability, and on baroreflex sensitivity. METHODS: Baroreflex sensitivity was studied in 11 rabbits (27 series) under slight sedation induced by pentobarbital infusion (5 mg/kg/hour), both with a steady-state method using phenylephrine-induced blood pressure ramps, and by spectral analysis estimating the transfer function from mean arterial blood pressure to heart rate. Mean arterial blood pressure in the femoral artery, heart rate, and a microphotoelectric plethysmogram of the capillary network of rabbit's ears were simultaneously recorded during the entire experiment. Baroreflex sensitivity was measured before and after 30 min of verapamil infusion (20 micrograms/kg/min). RESULTS: Verapamil-reduced baroreflex sensitivity measured by steady-state (2.6 +/- 0.2-1.7 +/- 0.2 beats/min/mmHg, mean +/- SEM) and transfer function methods (19.0 +/- 3.1-5.3 +/- 0.9; control vs. verapamil infusion, p < 0.001), and increased cardiovascular variability as estimated both by standard deviation in mean arterial blood pressure (2.0 +/- 0.1-4.0 +/- 0.4 mm Hg) and standard deviation in heart rate (6.5 +/- 1.0-9.8 +/- 1.1 bpm; p < 0.05). Verapamil increased heart rate (+3%; p < 0.05), reduced systemic mean arterial blood pressure (-12%; p < 0.05), and mean arterial blood pressure swings induced by increasing doses of phenylephrine bolus injections (-6% to -15%; p < 0.05). The reduction was larger for larger blood pressure ramps and exceeded the systemic arterial pressure reduction induced by verapamil infusion. A nonsignificant trend towards an increase in microcirculation was observed. CONCLUSIONS: Besides the direct cardiodepressant and vasodilatatory action of verapamil, its suppressive effect on baroreflex sensitivity should be taken into account, since this sensitivity might contribute to an increased risk of cardiac morbidity and mortality.

Analysis of Variance↗
PubMedDate not supplied

A practical EMG-based human-computer interface for users with motor disabilities.

In line with the mission of the Assistive Technology Act of 1998 (ATA), this study proposes an integrated assistive real-time system which "affirms that technology is a valuable tool that can be used to improve the lives of people with disabilities." An assistive technology device is defined by the ATA as "any item, piece of equipment, or product system, whether acquired commercially, modified, or customized, that is used to increase, maintain, or improve the functional capabilities of individuals with disabilities." The purpose of this study is to design and develop an alternate input device that can be used even by individuals with severe motor disabilities. This real-time system design utilizes electromyographic (EMG) biosignals from cranial muscles and electroencephalographic (EEG) biosignals from the cerebrum's occipital lobe, which are transformed into controls for two-dimensional (2-D) cursor movement, the left-click (Enter) command, and an ON/OFF switch for the cursor-control functions. This HCI system classifies biosignals into "mouse" functions by applying amplitude thresholds and performing power spectral density (PSD) estimations on discrete windows of data. Spectral power summations are aggregated over several frequency bands between 8 and 500 Hz and then compared to produce the correct classification. The result is an affordable DSP-based system that, when combined with an on-screen keyboard, enables the user to fully operate a computer without using any extremities.

Biofeedback, Psychology↗
PubMed2001

[Altered heart rate variability but preserved temporal relationship with sleep stages in a patient with primary aldosteronism].

OBJECTIVE: In a previous study, we found oscillations in the autonomic nervous system activity--as estimated by spectral analysis of R-R intervals--strongly linked to the non-rapid-eye movement (NREM)--REM sleep cycles, with low sympathetic activity during NREM sleep and predominant sympathetic activity during REM sleep. In the present study we established the 5-min nighttime profiles in various measures of heart rate variability (HRV) in one patient with primary aldosteronism before and after successful surgery of Conn adenoma. METHODS: One patient (female, 36 years old) with primary aldosteronism underwent two experimental nights a few weeks before and after surgery by coeliscopy in which sleep and cardiac recordings were made. Power spectral analysis was performed on ectopic-free R-R intervals with a fast Fourier transform. We calculated also the standard deviation of normal R-R intervals (SDNN) and the root mean square difference among successive R-R intervals (RMSSD). RESULTS: While removal of adenoma resulted in a rapid complete normalization of blood pressure and classical signs and biological symptoms of aldosterone hypersecretion, HRV profile did not changed a few weeks after surgery. The overnight SDNN was low although not abnormal at 38 and 33 ms before and after surgery respectively vs 58 +/- 15 ms (33 to 83) in normal female controls. RMSSD was low although not abnormal at 33 and 31 ms before and after surgery respectively vs 60 +/- 20 ms (20 to 105). The total spectrum power was low although not abnormal at 2.3 and 1.8 ms2 before and after surgery, respectively vs 3.2 +/- 1.1 ms2 (1.4 to 4.9). One out of the 8 controls had comparable or lower SDNN (33 ms), RMSSD (20 ms) and total power (1.4 ms2) values. While LF/HF ratio was comparable, the VLF (0.003-0.04 Hz) and LF (0.04-0.15 Hz) relative power were decreased and increased respectively in the patient compared in controls. Despite this reduced HRV, the normal temporal relationship of spectral parameters with specific sleep stages was preserved. CONCLUSION: Altered HRV with normal temporal relationships with specific sleep stages was observed in a patient with primary hyperaldosteronism. This HRV profile did not changed 20 weeks after successful surgery i.e. complete remission of classical signs and symptoms of aldosterone hypersecretion.

Adenoma↗
PubMed2001

[A statistical wavelength selection method of infrared spectra used in exhaust gas detection].

In order to extract the quantitative features of the rare pollution components from noisy atmospheric infrared spectra and thus create calibration models, a wavelength selection method based on statistic theory is proposed in this paper. In this method, an objective function is defined based on the estimation of spectral noise level at every wavelength position. Because the size of the wavelength subset is also included in the function, the model size will not become too big during the minimization of the error of the calibration model. To test the performance of this method, the wavelength subsets of measured spectra with background noises were selected and the calibration models were then created using neural network technique for three pollution gases, respectively. The test showed that the sizes of the selected wavelength subsets accorded with the calculated results. The subset sizes were less than 2% of the total wavelength points. Meantime, the spectral noises were also restrained markedly in the calibration model because of the wavelength selection. The experimental results proved the validity of the wavelength selection method.

Air Pollutants↗
PubMed1991

Significance and assessment of autonomic indices in cardiovascular reactions.

The purpose of this review was to integrate recent evidence supporting the reliability of noninvasive measures of parasympathetic and sympathetic activity. Literature concerning spectral analysis of heart period (HP) variability is reviewed with special emphasis on works revealing neural mediation of high-frequency and mid-frequency components of HP power spectrum and suggesting their use as a tool to assess autonomic balance. Problems of derivations of autonomic indices based on impedance cardiography and HP variance analysis are discussed. Advantages of parametric time series (autoregressive-AR) models are described with the objective of providing an informed basis for choosing among methodological alternatives. Two original approaches developed in our laboratory are outlined, namely the algorithms for systolic time interval assessment based on impedance cardiogram as well as the AR method developed for heart period power spectral density estimation.

Algorithms↗
PubMed1988

Regulatory role of vasoactive peptides in subcutaneous skin microcirculation of the hamster.

The microcirculatory effects of vasoactive peptides on arteriolar diameter were determined in the dorsal skin-fold preparation of conscious Syrian hamsters and related to arterial blood pressure (MABP). (5 Ile)-angiotensin II (ANG II), (8 Arg)-vasopressin (AVP), vasoactive intestinal polypeptide (VIP), atrial natriuretic factor (ANF), and substance P (SP) were administered intravenously as bolus injections in picomolar concentrations. The diameters of subcutaneous A3 arterioles (15-40 microns) at bifurcation sites were determined via a microscope video system and stored in a digital memory. When spontaneous rhythmic vasoconstrictions and dilations (vasomotion) were present, the diameter oscillations were analyzed by means of the Prony Spectral Line Estimator. ANG II caused sustained arteriolar contraction at increased MABP, but did neither induce nor modulate vasomotion. Both ANF and VIP slightly reduced MABP and had no effect on microcirculatory parameters. SP led to a significant dilation of subcutaneous arterioles in the hamster skin with concomitant drop in MABP, but did not influence arteriolar vasomotion. Physiological concentrations of AVP, as determined in the plasma by radioimmunoassay, caused a marked contraction of the arterioles and evoked a mild pressor response. In addition, AVP induced or greatly enhanced vasomotoric activity. This study therefore provides evidence that endogenous vasoactive peptides play an important role in regulation of skin peripheral resistance by altering arteriolar diameter in a tonic or even dynamic way.

Angiotensin II↗
PubMed1988

Biochemical and physiological consequences of an age-related increase in acetylcholinesterase activity at the rat neuromuscular junction.

Acetylcholinesterase (AChE) specific activity was assayed using diaphragm muscles obtained from mature adult (10 months) and aged (25-27 months) rats. Biochemical assays indicated significant age-related increases in the AChE specific activity of both noninnervated and innervated tissue. The different molecular forms of AChE were separated by velocity sedimentation and were further assayed. The age-related increase was manifest primarily in the 10S (G4) form in both noninnervated and innervated tissue and also the 16S (A12) form of the noninnervated samples. To ascertain more conclusively whether AChE activity in the end-plate junctional region of innervated tissue changed in the older rats, miniature end-plate currents (m.e.p.c.s) were recorded under voltage-clamp conditions before and after AChE inhibition. When AChE activity was inhibited by 10 microM echothiopate or 1 mM methanesulfonyl fluoride, m.e.p.c. amplitudes and decay time constants increased in both age groups. The magnitude of these increases was larger in the older animals. However, calculations of the relative change in m.e.p.c. amplitudes after AChE inhibition indicated that less ACh was hydrolyzed by AChE in the older animals. Inhibition of AChE did not affect mean channel open time, which was estimated from spectral analyses of ACh-induced membrane noise. These data indicate that the prolonged decay times in the older rats following AChE inhibition is quite likely due to an expanded field of postsynaptic ACh receptors and not exclusively to a change in junctional AChE.

Acetylcholinesterase↗
PubMed1981

Ultradian rhythms in stereotyped and self-injurious behavior.

Institutionalized profoundly mentally retarded persons who exhibited stereotyped motor movements, including self-injurious behavior, were observed continuously in their typical environments for periods of 8 to 14 hours on each of several days. In addition to targeting stereotyped responses, we collected data pertaining to activities, settings, other behavioral states, and social interactions. Spectral and cross-spectral analyses were conducted on data from each daily session. Power spectra indicated a marked ultradian or less than 24-hour rhythm for each subject on each day. Spectral density estimates were thought to reflect the influence of rhythmic changes in the institutional environment and, to a less degree, the influence of an endogenous rest--activity rhythm.

Adolescent↗
PubMed1976

[Electroencephalographic study of brain-infarction in dogs (author's transl)].

The evaluation of EEG-findings during the acute phase of stroke-patients is somewhat difficult particularly in regard to the voltage-production, less in regard to the temporary retardation of frequency. Within comparable neurophysiological and biochemical examinations of the experimental brain-infarct under standardized conditions of silicon-rubber-embolus was introduced intracarotideally and an occlusion of the media-trunk evoked. One day prior to the embolisation and on the first, third and fifth day thereafter EEG-derivation took place which were stored on analogous-tape, digitalized and were then confronted with the FFT-Algorithm. From the statistical point of view four animal groups were the result: HO-group (control group), H1-, H3- and H5-group (each time N = 6). Visual evaluation of the curves, descriptive and inferential statistics of the spectral EEG estimators showed a significant loss of power within five days after the infarction; it always was more distinct across the focal side than across the not immediately involved hemisphere. On the fifth day the original level of voltage was almost reached again. From the clinical standpoint the neurological deficits had practically been disappeared. The biochemical finishing of the dog-brains -- the results of which are planned to be confronted with the electrophysiological results in another paper -- in accordance with the papers of other authors brings close the assumption that the decrease of tension i.e. the loss of power of the electric potential during the first days after infarction is combined with a temporary decrease of the energetic potential of the metabolically active corticocerebral cells which is tied to the phosphagene-system of the highly energetical phosphates and metabolites of the energy-metabolism in the brain.

Animals↗
PubMed1996

Chromatic content of spectral lights.

Using three novel formats, we compare four estimates of the spectral sensitivity of the opponent stage channels: a Linear Model, Jameson and Hurvich's [Journal of the Optical Society of America, 45, 546-552 (1955)] hue cancellation sensitivities, Gordon and Abramov's [Optical Society of America Technical Digest Series, 15, 12-15 (1987)] hue scaling, and hue matching. The three formats are: the spectrum locus in the opponent equiluminant plane, null lines in the CIE XYZ chart and response functions for unique hues. All sensitivities show departures from the Linear Model and from each other. Relative to the model, common features of all estimates are that violets are compressed; long-wavelength reds are amplified; the redness component of violet lights is greatly attenuated; and saturation of violet stimuli is underestimated.

Color Perception↗
PubMed2006

Comparing spectra and coherences for groups of unequal size.

Spectra and coherences are standard measures of association within and between time series. These measures have several advantages over their time-domain counterparts, not the least of which is the ability to derive and estimate confidence intervals. However, comparing spectra and coherences between two groups of observation is a problem that has not received much attention. This problem is important in neuroscience since it is often of great interest to determine whether the estimates differ between distinct experimental/behavioral conditions. Here we propose one approach to this problem. Based on the known distributional properties of spectral and coherence estimates, we derive a test for equality of two spectral or coherence estimates. The test is applicable to unequal sample sizes. We also derive jackknifed estimates of the variance of the proposed test statistic. We suggest that comparing the estimates obtained from the jackknife procedure with the theoretical estimates provides a robust means of determining whether the data in question shows non-Gaussian or non-stationary behavior. Finally, we present applications of the method to simulated and real data.

Computer Simulation↗
PubMed1998

Macular pigment densities derived from central and peripheral spectral sensitivity differences.

Estimates of the density spectrum of the macular pigment (Wyszecki G, Stiles WS. Color Science: Concepts and Methods. Quantitative Data and Formulas. 1st ed. New York: Wiley, 1967); (Vos JJ. Literature review of human macular absorption in the visible and its consequences for the cone receptor primaries. Institute for Perception. Soesterberg, The Netherlands, 1972) are partially based on the difference between central and peripheral spectral sensitivities, measured under conditions chosen to isolate a single cone class (Stiles WS. Madrid: Union Internationale de Physique Pure et Appliquée, 1953;1:65-103). Such derivations assume that the isolated spectral sensitivity is the same at both retinal locations, save for the intervening macular pigment. If this is true, then the type of cone class mediating detection should not influence the calculated difference spectrum. To test this assumption, we measured central and peripheral spectral sensitivities in a deuteranope, a protanope and a normal trichromat observer: (a) for short-wave sensitive (S-) cone detection; and (b) for long-wave sensitive (L-) cone detection (deuteranope), for middle-wave sensitive (M-) cone detection (protanope) or for both L- and M-cone detection (normal trichromat). The difference spectra determined for L- or M-cone detection deviate significantly from those measured for S-cone detection, at wavelengths below 450 nm. A theoretical analysis suggests that the discrepancies are owing, in part, to regional variation in the optical density of the cone pigments; and that such receptor variation cannot be ignored when deriving the standard density spectrum of the macular pigment.

Color Vision Defects↗
PubMed2005

Psychophysical estimates of the number of spectral-reflectance basis functions needed to reproduce natural scenes.

Theoretical analyses of spectral reflectances of natural surfaces suggest that their perceived colors can be well reproduced by approximations comprising combinations of three or four spectral basis functions. The aim of the present work was to assess psychophysically the number of basis functions necessary to reproduce entire natural outdoor scenes. Hyperspectral images of 20 such scenes were each subjected to a principal component analysis and then reproduced with a variable number of basis functions. The quality of the color approximation under daylight illumination was quantified theoretically in CIELAB space and psychophysically by spatial and temporal two-alternative forced-choice measurements in which the original and the approximated images were compared on a calibrated color monitor. Although five basis functions produced on average unit error in CIELAB space, original images were visually indistinguishable from their approximations only if there were at least eight basis functions. The combination of the spectral diversity of the natural world and the observed levels of color discrimination suggest that estimates of the minimum number of basis functions necessary to reproduce natural scenes may need to be revised upward.

Algorithms↗
PubMed1996

Alcohol effects on the heritability of EEG spectral power.

To estimate the effects of a moderate dose of alcohol on heritability of the EEG power spectrum, 53 monozygotic and 38 like-sexed dizygotic Caucasian twin pairs (aged 30.0 +/- 7.0 years) were studied. Subjects were asked not to drink alcohol for 2 days and to fast after midnight before a protocol of: (1) a low fat meal at 8:00 AM; (2) a baseline EEG recording; (3) ingestion of alcohol over 10 min, which raised the breath alcohol concentration to 0.057 +/- 0.017% (SD); followed by (4) a postalcohol EEG recording 35.1 +/- 5.7 (SD) min after the start of drinking. One previous study (Propping, P., Hum. Genet. 35: 309-334, 1977) found that heritability (H2), the fraction of total variance in the EEG power that is attributable to genetic influences, increased after alcohol administration. In the current study, H2 of log-transformed, body-weight-adjusted spectral band power increased after alcohol for the theta-, alpha-slow, alpha-fast, beta-slow, and beta-fast bands (from an average of 0.47 to an average of 0.80). The increase in heritability was accompanied by a significant decrease in the within-pair differences of monozygotic cotwins for all of the same frequency bands except beta-fast. Because within-pair differences are expected to contain only environmental factors for the genetically identical individuals, it was concluded that alcohol decreases environmental variation of EEG power spectral density, causing the increase in H2.

Adult↗
PubMed1997

Spectral distortion properties of the integral pulse frequency modulation model.

The integral pulse frequency modulation (IPFM) model has been used for the following two purposes. First, it has been utilized to verify the correspondence between the spectral structure of autonomic input and the estimated spectrum of heart rate variability (HRV), relying mainly on the theoretical work of Bayly (1968). Second, the IPFM model provides a framework for evaluating how precisely the proposed method of HRV analysis could estimate the input spectral structure. However, the appropriateness of the IPFM model for both purposes has not been examined sufficiently in realistic situations. In this paper, the spectral structure of the pulse train generated by the IPFM model is theoretically derived for an input signal containing multiple frequency components. This is a more general condition than the single sinusoidal input signal used earlier. In accordance with the theoretical results, the magnitude of the spectral distortion is computed for a pair of varied frequencies, considering the corresponding coefficient of variation of interpulse intervals. Results show that the distortion could be nonnegligible under practical values of the coefficient of variation. Such distortion may well affect the spectral structure in the wide frequency range. This study suggests that the spectral structure of HRV should be interpreted carefully, taking the above distortion properties into account, even though the IPFM model appears to be established as a mechanism mediating between autonomic input and heart rate variability.

Heart Rate↗
PubMed1996

Severity of Aortic Regurgitation Assessed by Digital Image Processing of Doppler Spectral Recordings.

Visual estimates of the intensity of the regurgitant signal (RS) obtained by continuous-wave (CW) Doppler has been used as an indicator of the severity of aortic regurgitation (AR). This study was designed to test this concept quantitatively using digital image processing methods. Twenty-one patients with AR were studied, 14 of whom had concomitant mitral valve disease. Patients with aortic stenosis were excluded. By angiography, 10 patients had mild (grade 1 or 2), 5 had moderate (grade 3), and 6 severe (grade 4) AR. We digitized three well-defined AR envelopes and calculated the mean pixel intensity (MPI) of the RS and the systolic flow signal (SFS) using an offline computer analysis system developed in our laboratory. To negate the effects of different gain settings, the ratio of RS to SFS (RS/SFS ratio) was compared to angiographic grade of AR. Thus, each patient served as his own control. The mean RS/SFS ratio was 0.54 +/- 0.42 SD (range 0.46-0.59) for mild AR, 0.76 +/- 0.71 SD (range 0.65-0.82) for moderate AR, and 0.84 +/- 0.52 (range 0.77-0.92) for severe AR. This RS/SFS ratio correlated well with angiographic severity of AR (r = 0.9). A ratio of <0.6 identified patients with mild AR and >0.6 correlated with moderate-to-severe AR. We conclude that the ratio of the regurgitant to systolic flow CW Doppler signal is an accurate noninvasive indicator of AR severity. (ECHOCARDIOGRAPHY, Volume 13, May 1996)

Journal Article↗