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PubMed1999

Masking by light in hamsters with SCN lesions.

Inhibition of wheel running by light (masking) was investigated in Syrian hamsters with suprachiasmatic nucleus or sham lesions. Approximately 90% of the wheel revolutions made by hamsters with complete suprachiasmatic nucleus lesions, as judged by histology and power spectrum analysis of their wheel running, occurred during the dark phases of an ultradian light-dark cycle (3.5 h light, 3.5 h dark). This was demonstrated for two illumination levels (380 lx and 6 lx). Similar results were obtained with sham-operated animals. In further tests, the hamsters with lesions also retained a strong preference for the dark side of a box divided into dark and light sides. These results demonstrate that the suprachiasmatic nucleus is not necessary for masking by light or the preference for a dark over a light compartment. Evidently the direct effects of light can substitute for the endogenous control by the suprachiasmatic nucleus to maintain appropriate behaviour in time and space.

Activity Cycles↗
PubMed2004

Effect of different vibration frequencies on heart rate variability and driving fatigue in healthy drivers.

OBJECTIVE: This investigation was to assess the effect of different vibration frequencies on heart rate variability (HRV) and driving fatigue in healthy subjects during simulated driving, by the use of power spectrum analysis and subjective evaluation. MATERIALS AND METHODS: Sixty healthy subjects (29.6+/-3.3 years) were randomly divided into three groups, A, B and C, and the subjects of each group participated in the simulated driving for 90 min with vertical sinusoidal vibration (acceleration 0.05 g) of 1.8 Hz (group A), 6 Hz (group B) and no vibration (group C), respectively. Low-frequency (LF) and high-frequency (HF) components of HRV, reflecting sympathetic and parasympathetic activities, and the LF:HF ratio, indicating sympathovagal balance, were measured throughout all periods. All indices of HRV were calculated in the pre-experiment period, mid-experiment period and end-experiment period, and were analyzed by repeated measures analysis of variance. Subjective responses to a questionnaire were obtained after the simulated task for the three groups. RESULTS: Significant differences in all indices of HRV were observed between different experiment periods and between any two groups. The ratings of subjective fatigue exhibited significant differences between any two groups. CONCLUSION: The drivers' fatigue ratings were associated with vibration frequencies in simulated driving. The study quantitatively demonstrated that different effects on autonomic nerve activities were induced by different vibration frequencies.

Adult↗
PubMed2002

The effects of voluntary contraction effort on quadriceps femoris electromyogram median frequency in humans: a muscle and sex comparison.

The purpose of this study was to examine the effect of voluntary contraction efforts on the median frequency (f(med)) of the electromyogram (EMG) recorded from the quadriceps femoris muscle in healthy men and women. A group of 30 healthy volunteers (15 men, 15 women) were assessed for EMG activity of the vastus medialis (VM), vastus lateralis (VL), and rectus femoris (RF) muscles during isometric contractions with the knee at 60 degrees flexion. Subjects performed a series of 5 s maximal voluntary isometric contractions that anchored the perceptual range with a "10" on a 10-point scale. Sub-maximal isometric contractions were then separately performed at the following perceived effort levels on the 10-point scale: 1, 2, 3, 4, 5, 6, 7, 8 and 9, in a random order. Subjects were instructed to maintain the contraction at each perceived level of effort for 5 s. The f(med) of the three muscles was assessed using a power spectrum analysis performed over 11 consecutive, 512 ms, epochs overlapping each other by half their length during the middle 3 s of each contraction. The f(med) for each of the 11 epochs was then determined for each muscle, followed by calculation of the means and normalized coefficients of variation [(standard deviation/mean)x100%] for each contraction. The results demonstrated that the mean f(med) of VL was significantly greater than those of the other two muscles, and that f(med) of RF was significantly greater than that of VM. The VL muscle demonstrated a significant increase in mean f(med) across the contraction efforts, compared to the VM and RF muscles that displayed a significant decrease. The men displayed significantly higher f(med) values for the VM muscle than did the women, as well as showing a significantly greater increase across the contraction efforts for the VL muscle. The variability of f(med) was shown to be significantly higher for the VM muscle, compared to the VL and RF muscles. The findings of this study suggest that the f(med) statistic is most sensitive to contraction intensity efforts for the VL muscle, and that men display significantly higher values for the VL and VM muscles, compared to women.

Adult↗
PubMed2002

Genioglossal electromyogram during maintained contraction in normal humans.

Knowledge of the fatigability of the genioglossus muscle is of interest because this muscle prevents pharyngeal collapse, especially during sleep. In the present investigation, signs of fatigue in the genioglossus muscle were studied by measuring the tongue endurance using a force transducer and electromyographic (EMG) activity of the genioglossus muscle in eight nonapnoeic men. Mean absolute EMG values and spectrum analysis were calculated at three levels of submaximal effort. Median frequency and the force:mean absolute EMG value ratio were independent of force level (F = 0.37, P = 0.93; F = 0.35, P = 0.94, respectively) but dependent on effort duration (F = 52, P < 0.0001; F = 16, P < 0.0001). Force:mean absolute EMG value and logarithmic median frequency decreased linearly with respect to time and were similar at the three force levels when time was expressed as a percentage of total test time (F = 0.37, P = 0.93). The decrease in median frequency was ascribable to a larger increase in low- than in high-frequency components, as shown by the significant decrease in the high-frequency:low-frequency ratio (F = 27, P < 0.0001) with time. The method of investigation used in this study allowed detection of the behaviour of the tongue during fatigue and, therefore, should be useful in disorders where mechanical failure of the tongue is suspected, such as the sleep apnoea syndrome or in neuromuscular disorders.

Adult↗
PubMedDate not supplied

Adaptation of the short latency component of the stretch reflex plays only a minor role in compensating for muscle fatigue induced by spontaneous hopping in humans.

The influence of fatigue on the stretch reflex evoked in ankle extensor muscles by hopping was investigated in six healthy men. The men hopped on a force platform, at spontaneous frequency and amplitude, until they were unable to maintain the initial frequency or amplitude of the jumps. This task was done with the knees flexing normally during ground contact or under instructions to straighten the knees. Surface electromyograms (EMG) of soleus (SO), gastrocnemius medialis (GM), and tibialis anterior (TA) muscles were recorded simultaneously with the vertical component of the ground reaction force. Spectrum analysis of the EMG recorded during isometric tests performed immediately before and after the fatiguing hopping task demonstrated the existence of fatigue in SO and GM and often in TA. The stretch reflex was studied during the first and last ten jumps of every hopping series. The long-latency components of the reflex were too variable to be analysed. Whatever the hopping condition, latency and amplitude of the short latency component were not significantly modified by fatigue. Fatigue enhanced the occurrence of this reflex component in SO only. These data suggest that in fatiguing submaximal hopping, the neuromuscular system does not fundamentally change its stiffness regulation before the endurance time has been reached.

Adaptation, Physiological↗
PubMed2000

Difference in human cardiovascular response between upright and supine recovery from upright cycle exercise.

Cardiovascular responses were examined in seven healthy male subjects during 10 min of recovery in the upright or supine position following 5 min of upright cycle exercise at 80% peak oxygen uptake. An initial rapid decrease in heart rate (fc) during the early phase of recovery followed by much slower decrease was observed for both the upright and supine positions. The average fc at the 10th min of recovery was significantly lower (P < 0.05) in the supine position than in the upright position, while they were both significantly greater than the corresponding pre-exercise levels (each P < 0.05). Accordingly, the amplitude of the high frequency (HF) component of R-R interval variability (by spectrum analysis) in both positions was reduced with a decrease in mean R-R interval, the relationship being expressed by a regression line--mean R-R interval = 0.006 x HF amplitude + 0.570 (r = 0.905, n = 28, P < 0.001). These results would suggest that the slower reduction in fc following the initial rapid reduction in both positions is partly attributable to a retardation in the restoration of the activity of the cardiac parasympathetic nervous system. Post-exercise upright stroke volume (SV, by impedance cardiography) decreased gradually to just below the pre-exercise level, whereas post-exercise supine SV increased markedly to a level similar to that at rest before exercise. The resultant cardiac output (Qc) and the total peripheral vascular resistance (TPR) in the upright and supine positions returned gradually to their respective pre-exercise levels in the corresponding positions. At the 10th min of recovery, both average SV and Qc were significantly greater (each P < 0.005) in the supine than in the upright position, while average TPR was significantly lower (P < 0.05) in the supine than in the upright position. In contrast, immediately after exercise, mean blood pressure dropped markedly in both the supine and upright positions, and their levels at the 10th min of recovery were similar. Therefore we concluded that arterial blood pressure is maintained relatively constant through various compensatory mechanisms associated with fc, SV, Qc, and TPR during rest and recovery in different body positions.

Adult↗
PubMed1998

Heart rate variability in exercising humans: effect of water immersion.

Power spectrum analysis of heart-rate variability was made in seven men [mean age 22 (SEM 1) years] in head-out water immersion (W) and in air (A, control) at rest and during steady-state cycling to maximal intensity (maximum oxygen uptake, VO2max). At rest W resulted in a trebled increase in the total power (P < 0.05), coupled with minimal changes in the power (as a percentage of the total) of the high frequency peak (HF, centred at 0.26 Hz; 18% vs 28%) and of the low frequency peak (LF, 0.1 Hz; 24% vs 32%). A third peak at about 0.03 Hz (very low frequency, VLF) represented the remaining power both in W and A. These changes as a whole indicated that immersion caused a vagal dominance in cardiac autonomic interaction, due to the central pooling of blood and/or the pressure of water on the trunk. Exercise caused a decrease in the total power in W and A. The LF% did not change up to about 50% V02max, thereafter decreasing towards nil in both conditions. The HF% decreased in similar ways in W and A to about half at 55%-60% VO2max and then increased to reach 1.5 times the resting values at VO2max. The central frequency of HF increased linearly with oxygen uptake, showing a tendency to be higher in W than in A at medium to high intensities. The VLF% remained unchanged. The lack of differences in the LF peak between W and A during exercise would suggest that blood distribution had no effect on the readjustments in control mechanisms of arterial pressure. On the other hand, the findings of similar HF powers and the very similar values for ventilation in W and A confirmed the direct effect of the respiratory activity in heart rate modulation during exercise.

Adult↗
PubMed1999

Effects of hyperoxia on oxygen uptake kinetics in cystic fibrosis patients as determined by pseudo-random binary sequence exercise.

Patients with cystic fibrosis (CF) have been shown to exhibit impaired oxygen uptake (VO2) kinetics independent of their physical fitness. This study investigated whether oxygen supplementation improves VO2 kinetics in CF as determined by cycle ergometry at submaximal exercise intensities using a pseudo-random binary sequence exercise test i.e. a simultaneous application of different frequencies of sinusoidal work. The subjects were 9 CF patients and 13 healthy controls (HC) and they exercised while breathing humidified and heated air with a fractional concentration of oxygen in inspired air (F(I)O2) of either 0.21 or 0.40. With a F(I)O2 of 0.21 the respiratory exchange ratio (R) was higher in CF than in HC both at rest (0.91 vs 0.81) and during exercise (0.97 vs 0.89). Oxygen saturation (SO2) was slightly lower in CF. but remained above 90% during exercise (92.7% vs 95.2%). Spectrum analysis revealed that in CF, the amplitude ratio (AR) between V02 and exercise intensity was lower over a wide frequency range (P < 0.05). In addition, CF showed a larger negative phase shift (PS) at lower frequencies (P < 0.005). With a F(I)O2 of 0.40, SO2 increased to about 97% in both groups; while R remained higher in CF (0.92) compared to HC (0.81). In the control group, the O2 supplement raised AR but the VO, kinetics of the CF patients were not significantly affected. In HC the enhanced AR during oxygen supplementation would suggest a cardiopulmonary limitation of VO2 at the onset of submaximal exercise. In CF patients low AR and PS would indicate an attenuated VO2 response attributable to an impaired oxygen utilization in the muscles because the oxygen supplement normalised SO2 but failed to improve R and VO2 kinetics.

Adolescent↗
PubMed2001

Thermal stress modulates arterial pressure variability and arterial baroreflex response of heart rate during head-up tilt in humans.

To examine the effects of thermal stress on the blood pressure variability and the arterial baroreceptor-cardiac reflex during orthostatic stress, 11 male volunteers underwent whole body thermal stress using a cool or hot water-perfused suit during 5 min of 70 degrees head-up tilt (HUT). The spontaneous variability in arterial pressure was quantified by power spectrum analysis. The sensitivity of the arterial baroreceptor-cardiac reflex was calculated from the spontaneous changes in beat-to-beat arterial pressure and heart rate (fc). During supine rest the variability of arterial pressure decreased during cooling, while it remained unchanged during heating. The variability increased with HUT; it was greater (P < 0.05) with heating than with cooling. In the supine condition, the arterial baroreflex sensitivity of fc increased during cooling, while it did not change during heating. The sensitivities decreased (P < 0.05) with HUT during both thermal stresses; the decreased rate of sensitivity from the pre-tilt value was greater during heating [mean 63 (SEM 4)%] and smaller during cooling [mean 11 (SEM 24)%] than during normothermia [mean 47 (SEM 4)%] (both, P < 0.05). There were significant negative correlations between the sensitivities and the amplitude of the arterial pressure variability during normothermia and heating (P < 0.0001). The results suggest that the spontaneous baroreflex response of fc is a modulatory factor for the changes of arterial pressure variability brought about by thermal stress during orthostatic stress.

Adult↗
PubMed2006

Seasonality of weather and tree phenology in a tropical evergreen mountain rain forest.

Flowering and fruiting as phenological events of 12 tree species in an evergreen tropical mountain rain forest in southern Ecuador were examined over a period of 3-4 years. Leaf shedding of two species was observed for 12 months. Parallel to the phenological recordings, meteorological parameters were monitored in detail and related to the flowering and fruiting activity of the trees. In spite of the perhumid climate of that area, a high degree of intra- and inter-specific synchronisation of phenological traits was apparent. With the exception of one species that flowered more or less continuously, two groups of trees could be observed, one of which flowered during the less humid months (September to October) while the second group started to initiate flowers towards the end of that phase and flowered during the heavy rains (April to July). As reflected by correlation coefficients, the all-time series of meteorological parameters showed a distinct seasonality of 8-12 months, apparently following the quasi-periodic oscillation of precipitation and related cloudiness. As revealed by power spectrum analysis and Markov persistence, rainfall and minimum temperature appear to be the only parameters with a periodicity free of long-term variations. The phenological events of most of the plant species showed a similar periodicity of 8-12 months, which followed the annual oscillation of relatively less and more humid periods and thus was in phase or in counter-phase with the oscillations of the meteorological parameters. Periods of unusual cold or dryness, presumably resulting from underlying longer-term trends or oscillations (such as ENSO), affected the homogeneity of quasi-12-month flowering events, fruit maturation and also the production of germinable seeds. Some species show underlying quasi-2-year-oscillations, for example that synchronise with the development of air temperature; others reveal an underlying decrease or increase in flowering activity over the observation period, influenced for instance by solar irradiance. As Ecuador suffers the highest rate of deforestation in South America, there is an urgent need for indigenous plant material for reforestation. A detailed knowledge of the biology of reproduction in relation to governing external factors (mainly climate) is thus required.

Altitude↗
PubMed2004

The value of electromyography of the lumbar paraspinal muscles in discriminating between chronic-low-back-pain sufferers and normal subjects.

The authors studied the surface electromyographic (EMG) spectrum of the paraspinal muscles of 350 subjects. They were classified by their history as normal (n=175), chronic low back pain (n=145), or past history (n=30). They pulled upwards on a floor-mounted load cell at two-thirds of their maximum voluntary contraction for 30 s, while the EMG was measured from the paraspinal muscles at the L4/L5 level. From the EMG signal the root-mean-square (RMS) was calculated. Power spectrum analysis allowed calculation of the median frequency slope, the initial median frequency (IMF), modal frequency, peak amplitude and spectral width at half peak amplitude (half-width). All of the variables of the chronic group were significantly different from the normal group, except the median frequency slope, RMS slope and mode. Half-width, age and maximum voluntary contraction were shown to be independent predictors of back pain classification. Half-width classified the subjects with a sensitivity of 0.65 and a specificity of 0.75.

Chronic Disease↗
PubMed2000

Endoscopic transthoracic sympathicotomy affects the autonomic modulation of heart rate in patients with palmar hyperhidrosis.

BACKGROUND: Palmar hyperhidrosis has been associated with an increased activity of the sympathetic nervous system. The objective of this study was to assess the immediate and long-term effects of endoscopic transthoracic sympathicotomy on the autonomic modulation of the heart rate in patients with palmar hyperhidrosis. METHODS: Power spectrum analysis of heart rate variability in the lying position and after passive tilt to the upright position was performed in thirteen patients the day before and after sympathicotomy. A follow-up recording was performed in ten patients approximately six months later. Recordings from 26 healthy subjects were used as a reference group. FINDINGS: The patients had a tendency to higher power of the low-frequency (LF: 0.04-0.15 Hz) and high-frequency (HF; above 0.15 Hz) components than controls in the upright position. After sympathicotomy LF power was reduced, but HF power was unchanged. At follow-up LF power remained at a lower level, but now HF power was reduced. INTERPRETATION: Patients with palmar hyperhidrosis have a sympathetic overactivity but also a compensatory high parasympathetic activity. Sympathicotomy results in an initial sympathovagal imbalance with a parasympathetic predominance, which is restored on a long-term basis.

Adult↗
PubMed2004

Use of principal component analysis in the frequency domain for mapping electroencephalographic activities: comparison with phase-encoded Fourier spectral analysis.

Principal component analysis (PCA) can separate multichannel electroencephalographic (EEG) epochs into linearly independent (temporally and spatially noncorrelated) components. Results of PCA include component time-series waveforms and factors representing the contribution of each component to each electrode; these factors may be displayed as contour maps representing the topographic distribution of each component. However, PCA often does not achieve the most useful separation of components. PCA may be performed in the frequency domain to potentially improve results. After inspecting principal components of the frequency spectra, spectral values in a selected frequency range are multiplied by a chosen factor to emphasize (or de-emphasize) these frequencies and PCA is redone, promoting the separation of different frequencies into different components. Phase-encoded Fourier spectral analysis (PEFSA) uses multichannel complex Fourier spectra (amplitude and phase) to obtain positive or negative (phase-encoded) potentials at each electrode for any selected frequency. These may be displayed as a contour map representing the topographic distribution of the selected frequency. Applying both techniques, we found that EEG activities of differing frequency were readily separated by PEFSA, while standard PCA often mixed activities with different frequencies into a single component. However, frequency-domain PCA gave a component whose spatial distribution well matched PEFSA results. PCA is superior to PEFSA for separating activities with overlapping frequencies but differing spatial distributions. Preservation of phase information is an advantage of PEFSA and PCA over topographic maps that represent only amplitude (or power) at a given frequency. PCA or PEFSA maps can serve as a starting point for source localization.

Brain↗
PubMed1991

Accuracy of assessment of cardiac vagal tone by heart rate variability in normal subjects.

The correlations of 11 indexes of heart rate variability were examined with pharmacologically determined cardiac vagal tone in 15 normal subjects at supine rest. After sympathetic influences by intravenous propranolol were eliminated, RR interval variability was measured for 10 minutes under controlled respiration (0.25 Hz), and cardiac vagal tone was determined as the decrease in mean RR interval following complete vagal blockade with atropine. Time domain indexes (standard deviation, coefficient of variance and mean successive difference) correlated strongly with vagal tone (r = 0.87, 0.81 and 0.92, respectively; p less than 0.001 for all). The same was true for frequency domain indexes for the high-frequency (0.25 Hz) component calculated both by autoregressive spectrum analysis (square root of power and coefficient of component variance) and by fast Fourier transform (mean amplitude) (r = 0.91, 0.85 and 0.86, respectively; p less than 0.0001 for all). However, frequency domain indexes for the low-frequency spectral component (0.03 to 0.15 Hz) correlated less strongly (r = 0.69, 0.55 and 0.70, respectively), and the fraction of power [power/(total power greater than 0.03 Hz)] of both components showed no correlation. Principal component analysis showed that the first 6 indexes with strong correlations contained solely the first principal component closely related to vagal tone, whereas the remaining 5 indexes also contained the second component unrelated to vagal tone. These results indicate that most of the time and frequency domain analyses in use provides an accurate and common measure of cardiac vagal tone at rest.

Adult↗
PubMed1992

Reactive hyperemia in the nonused internal mammary artery after median sternotomy.

Doppler spectrum analysis was performed in the nonused internal mammary artery in a group of patients who underwent myocardial revascularization using the contralateral internal mammary artery and in both internal mammary arteries in a group of patients who underwent median sternotomy for cardiac surgical procedures in which the internal mammary artery was not used. In all nonused internal mammary arteries the preoperatively triphasic systolic flow pattern had postoperatively converted into a unidirectional systolic flow pattern with a large diastolic flow component, characterized by a significant increase in the diastolic flow parameters and a significant decrease in the resistance and pulsatility indices. This effect had almost subsided at 6 months postoperatively. This study indicates that the reactive hyperemia observed in the nonused internal mammary artery in the early postoperative period is mainly caused by the temporarily increased metabolic demand of the anterior thoracic wall and mediastinum, rather than by the metabolic demand of the anterior diaphragm and the contralateral rectus abdominis muscle after deprivation of their main nutritional vessel.

Adolescent↗
PubMed1991

1H-NMR spectroscopy of manno-oligosaccharides of the beta-1,2-linked series released from the phosphopeptidomannan of Candida albicans VW-32 (serotype A).

Manno-oligosaccharides (DP 2 to greater than 15) were released by mild acid hydrolysis from the phosphopeptidomannan of a Candida albicans strain of A serotype (VW-32). Manno-oligosaccharides ranging from biose to heptaose were obtained in appreciable amount. Structural investigation of these oligosaccharides showed them to be of the beta-1,2-linked series. The occurrence of such compounds has already been reported in other strains of Candida albicans. We here report the assignment of the structural reporter groups of each of them, and general rules applicable for the 1H-NMR spectrum analysis of linear manno-oligosaccharide of general structure: Man(beta 1-2) [Man(beta 1-2)]nMan

Candida albicans↗
PubMed1993

Species-dependent differences in the biochemical effects and metabolism of 5-benzylacyclouridine.

The pharmacokinetics and biochemical effects of the uridine phosphorylase (UrdPase) inhibitor 5-benzylacyclouridine (BAU) were investigated in the mouse, rat and monkey. Following i.p. administration of BAU (30 mg/kg) in the mouse and i.v. administration in the rat and monkey, initial BAU plasma half-life values were 36, 36 and 25 min, and the areas under the plasma BAU concentration versus time curves (AUC) were 127, 80 and 76 microM.hr, respectively. Rats were also dosed p.o. and i.v. with BAU at 90 mg/kg, and a comparison of the AUC values showed an oral bioavailability of 70%. Analyses of plasma samples by HPLC indicated that the metabolism of BAU differed in these species. A major BAU metabolite was observed in monkeys. Its concentration was greater than or equal to that of BAU in almost every plasma sample, and its elimination paralleled that of BAU. Urinary recovery of the metabolite was 10-fold higher than the recovery of unchanged drug. The compound was identified as the ether glucuronide of BAU by its UV absorption spectrum, its co-elution with BAU after incubation with beta-glucuronidase, and liquid chromatography/mass spectrum analysis. A different metabolite was detected in rat plasma; its maximum concentration was 15% of the BAU level, and its elution position on the HPLC chromatogram was not affected by the action of beta-glucuronidase. BAU had equivalent potency against UrdPase in liver extracts from the three species, with Ki values of about 0.17 microM. However, the in vivo effects of BAU on plasma uridine concentrations were species dependent. In mice, a 30 mg/kg i.p. dose of BAU increased the plasma uridine concentration to 11 microM from a control level of 1.8 microM. In the rat, a 30 mg/kg i.v. dose of BAU increased plasma uridine to 2.1 from 1.1 microM control levels, and a 300 mg/kg oral dose resulted in a peak plasma uridine concentration of only 6 microM. In the monkey, BAU (30 mg/kg, i.v.) had no effect on plasma uridine despite the presence of 10-100 microM BAU levels in plasma for 1.5 hr. These data show that there are significant differences in the biochemical effects and metabolism of BAU in CD-1 mice, CD rats and cynomolgus monkeys.

Animals↗
PubMed1981

Temporary desynchronization among circadian rhythms with lateral fornix ablation.

Lateral or medial fornix suction ablations were performed on adult male rats in order to selectively ablate or leave intact, respectively, fibers which terminate in the region of the suprachiasmatic nucleus and hypophysiotropic area of the hypothalamus. Plasma adrenal corticosteroid secretion, locomotor activity, body temperature, and food and water intake were recorded at 4 h intervals over a period of 48 h in individual animals 7-10 days postoperatively. Lateral fornix ablation specifically disrupted adrenal corticosteroid periodicity. A least-squares spectrum analysis of the data indicated that corticosteroid may be under ultradian control after this lesion. All animals, regardless of treatment, exhibited normal circadian locomotor activity patterns. Aberrations in feeding, drinking and body temperature rhythms were occasionally observed. This represents a temporary dissociation between the rhythmic expression of corticosteroid secretion and activity, temperature, feeding and drinking. The evidence presented lends support to the multi-oscillator theory of circadian organization, and suggests that the anteroventral subiculum, via the medial corticohypothalamic tract, is important in the regulation of some, but not all, circadian parameters. In addition to the observations on the rhythmicity of locomotor activity, the extent to which the animals are active is also significantly different between groups; ie., the hyperactivity of fornix-transected animals previously reported by others was found to be associated with lateral and not medial fornix ablation.

Animals↗