Biomedical subjects

Hartmut Schächinger

Publications and source records attributed to Hartmut Schächinger.

11 recordsLinked to original sources

PubMed2004

Selective processing of food words during insulin-induced hypoglycemia in healthy humans.

RATIONALE: Hypoglycemia leads to undernutrition of the brain. Favoring selective processing of food stimuli would be an adaptive cognitive strategy. However, hypoglycemia is known to impair several aspects of cognitive function, and it is unknown whether selective cognitive processing of food stimuli occurs during insulin-induced hypoglycemia. METHODS: In a single-blind repeated measures design, healthy young adults (n=12, six female, mean age 28 years; mean body mass index 22.5 kg/m(2)) performed a standard Stroop word-color test, as well as a variant with food words designed to detect selective processing of food cues. Two sessions were scheduled with a 4-week interval. In each session, a hyperinsulinemic clamp method produced a normoglycemic (plasma glucose: 4.7 mmol/l) period, followed on 1 day by a hypoglycemic (2.7 mmol/l) testing period, and on the other day a second normoglycemic testing period (counterbalanced order). RESULTS: Color naming verbal reaction time (RT) increased during hypoglycemia (P<0.0001). The extent of the Stroop cognitive interference was independent of plasma glucose level. The key finding is that RT for food words increased more than for non-food control words (P<0.004), and this effect was not predicted by hunger ratings. CONCLUSIONS: Our data provide new evidence that during hypoglycemia, attention is directed selectively to food-relevant stimuli. The results are discussed in terms of adaptation.

Adaptation, Physiological↗

PubMed2004

Mental relaxation improves long-term incidental visual memory.

Experimental evidence has linked increased arousal to enhanced memory retention. There is also evidence that procedures reducing arousal, i.e., mental relaxation, might improve memory, but conflicting results have been reported. To clarify this issue, we studied the effects of a single session of relaxation training on incidental visual long-term memory. Thirty-two relaxation-naive subjects viewed 280 slides without being told that there would be subsequent memory testing. Afterwards, subjects listened to a 12 min relaxation tape; 16 subjects relaxed by following the instructions (relaxation group), and the other 16 subjects pressed a button whenever a body part was mentioned (control group). While listening to the relaxation tape, high frequency heart rate variability (HRV) was greater and low frequency HRV was lower in the relaxation group, implying effective relaxation and increasing parasympathetic activation. The relaxation group had superior memory retention 4 weeks later (p = .004), indicating enhancement of long-term memory performance. This effect could not be explained by retroactive interference experienced in the control group because short-term memory performance immediately after the tape was slightly better in the control group. Retention of materials acquired after the relaxation session remained unaffected, suggesting relaxation has retrograde effects on memory consolidation. Our data demonstrate a favorable influence of relaxation on at least this aspect of learning. Our data also extend previous knowledge on the beneficial effects of ascending parasympathetic stimulation on memory retention in that enhanced long-term memory consolidation may also occur in the presence of central and descending parasympathetic activation triggered by willful psychomotor activity.

Adult↗

PubMed2004

Increased high-frequency heart rate variability during insulin-induced hypoglycaemia in healthy humans.

Despite causing sympathetic activation, prolonged hypoglycaemia produces little change in HR (heart rate) in healthy young adults. One explanation could be concurrent parasympathetic activation, resulting in unchanged net effects of autonomic influences. In the present study, hypoglycaemic (2.7 mmol/l) and normoglycaemic (4.7 mmol/l) hyperinsulinaemic clamp studies were performed after normoglycaemic baseline clamp periods with 15 healthy volunteers (seven male; mean age, 27 years) on two occasions in a randomized single-blind cross-over design. Non-invasive indices of cardiac autonomic activity and hormones were measured at baseline and 1 h after the beginning of hypoglycaemia or control normoglycaemia. Plasma insulin levels and mean HR were similar during both conditions. During hypoglycaemia, there was a 485% increase in plasma adrenaline (epinephrine). A shortening of the pre-ejection period by 45% suggested strong sympathetic cardiac activation. High-frequency (0.15-0.45 Hz) HRV (HR variability) increased, indicating a concomitant increase in parasympathetic tone. Thus, during hypoglycaemia-induced sympathetic cardiac activation in healthy adults, parasympathetic mechanisms are involved in stabilizing mean HR.

Adult↗

PubMed2004

Increased renovascular response to angiotensin II in persons genetically predisposed to arterial hypertension disappears after chronic angiotensin-converting enzyme inhibition.

OBJECTIVE AND METHODS: Functional changes in the kidneys of healthy men with (FH+) (n = 15) and without (FH-) (n = 15) family history of primary arterial hypertension were examined during administration of low-dose exogenous angiotensin II (A2) (1 ng/kg per min) before and after acute (1 mg intravenous enalaprilat) and chronic (7 days oral enalapril, 30 mg/day) angiotensin-converting enzyme (ACE) inhibition. RESULTS: Before chronic ACE inhibition, A2 increased mean arterial blood pressure (FH+, 8.7 +/- 0.8 mmHg; FH-, 8.9 +/- 0.9 mmHg), plasma immunoreactive A2 (FH+, 21 +/- 2 pg/ml; FH-, 18 +/- 3 pg/ml) and plasma aldosterone (FH+, 64 +/- 7 pg/ml; FH-, 56 +/- 6 pg/ml) to a similar degree in both groups. Chronic ACE inhibition had no impact on A2 blood pressure, plasma A2, or plasma aldosterone effects. A2 significantly increased renal vascular resistance in both groups (FH+, 3956 +/- 462 dyne s cm(-5); FH-, 2219 +/- 550 dyne s cm(-5)), but the effect was more pronounced in FH+ (P = 0.02). Glomerular hemodynamics, estimated by a modified Gomez model, revealed increased afferent and efferent responsiveness to A2 in FH+ subjects. These differences disappeared after chronic ACE inhibition when total, afferent and efferent sensitivities to A2 were similar in both groups. CONCLUSIONS: Systemic blood pressure and plasma aldosterone responses to A2 were similar in men with or without a genetic disposition to primary arterial hypertension. However, our data demonstrate that men with a family history of hypertension have increased renovascular sensitivity to A2, and that chronic ACE inhibition normalizes their sensitivity.

Adolescent↗

PubMed2003

Cognitive and psychomotor function in hypoglycemia: response error patterns and retest reliability.

Hypoglycemia has been shown to impair cognitive and psychomotor function, but it has been unclear which measures are most reliable and sensitive for detecting these effects. In a single-blind repeated measures design, healthy young adults (N=17, 8 male, mean age 27 years) performed three PC-based cognitive and psychomotor function tests: a paced auditory serial addition task (PASAT), an adaptive five-choice reaction time test (CRTT), and a manual tracking test on two occasions 4 weeks apart. In each session, a hyperinsulinemic clamp method was used during a normoglycemic (plasma glucose: 4.7 mmol/l) baseline testing period, followed in one session by a normoglycemic target testing period, and in the other session by a hypoglycemic (2.7 mmol/l) target testing period. All cognitive and psychomotor function measures showed high test-retest reliability (r ranging from.69 to.95) and sensitivity to hypoglycemia (P<.01). A new finding is that on the PASAT, hypoglycemia appears to differentially increase the rate of omission errors more than it increases false responses. Data on PASAT reaction time (RT) are also presented.

Adult↗

PubMed2003

Prepulse inhibition of the human startle eye blink response by visual food cues.

We present a new paradigm to investigate cognitive processing of food cues. The study assessed if pictures of food induce prepulse inhibition (PPI) of startle eye blink, and if any such effect is sensitive to food deprivation. In a balanced cross-over design, 16 healthy male volunteers (mean age: 29 years) were tested on 2 days 1 week apart, either after a period of normal food intake (NFI) or after a 24 h period of food restriction (RFI). On each experimental day, 80 control and 20 food pictures (slides) were displayed. Noise stimuli were presented 250 ms after slide onset. Startle responses were assessed by EMG recordings of the right M. orbicularis oculi. Startle elicited during dark inter-slide periods served as control responses to calculate PPI effects. The arousing content of each picture was rated by all subjects at the end of the session. The perceived arousal effect of control slides was strongly related to their PPI effect; no impact of food access status on this association was detectable. After NFI, food slides significantly induced PPI of startle (mean: -14.5%). After RFI, arousal ratings for food pictures increased but PPI did not. These results are evidence for a pre-attentive mechanism operative in the processing of visual food cues.

Adult↗

PubMed2003

Reduced vagal activity in salt-sensitive subjects during mental challenge.

BACKGROUND: Salt-sensitive normotensive men exhibit an enhanced pressor and heart rate (HR) response to mental stress. Stress-induced HR acceleration may result from sympathetic activation or vagal withdrawal. We studied the importance of vagal withdrawal for the increased stress responsiveness of salt-sensitive subjects. METHODS: We studied cardiovascular reactivity to mental challenge in 17 salt-sensitive healthy white male students and 56 salt-resistant control subjects who were comparable with respect to age, body mass index, and physical fitness. Salt sensitivity was determined by a 2-week dietary protocol (20 mmol v 240 mmol sodium/day). Mental stress was induced by a computerized information-processing task (manometer test). Electrocardiogram and finger blood pressure (BP; Finapres, Ohmeda, Louisville, CO) were registered continuously to determine HR and interbeat-interval length. Time and frequency domain (spectral power) based measures of respiratory-related heart rate variability (HRV) were calculated to estimate vagal cardiac control; diastolic BP reactivity was assessed to estimate peripheral sympathetic effects. RESULTS: Stress-induced increase in HR was higher in salt-sensitive than in salt-resistant subjects. Salt-sensitive subjects, in comparison to salt-resistant subjects, showed significantly reduced respiratory-related HRV during baseline and mental stress conditions (P <.01). The increase in diastolic BP during mental challenge was significantly greater in salt-sensitive subjects (P <.05). CONCLUSIONS: Our findings suggest reduced vagal and increased sympathetic tone during mental challenge in salt-sensitive subjects. Altered autonomic nervous system function may contribute to later development of hypertension in salt-sensitive individuals.

Adult↗

PubMed2003

Rate response of a closed-loop stimulation pacing system to changing preload and afterload conditions.

Closed-loop stimulation (CLS) is a new sensor concept for rate adaptive pacing measuring changes in the unipolar right ventricular impedance, which correlates to changes of the right ventricular contractility and reflects the autonomic nervous innervation of the heart. Some patients do not tolerate the CLS mode because of inappropriate tachycardia, mainly related to postural changes. This study tested if the rate response of the CLS sensor is influenced not only by myocardial contractility but also by rapid changes in right ventricular filling. In 12 patients (10 men, median age 77 years) with a Biotronik Inos(2)-CLS DDDR pacemaker and 14 controls (13 men, median age 59 years) head-up tilt and handgrip testing was performed to provoke rapid changes in pre- and afterload. Tilting the pacemaker patients resulted in a nonphysiological steep increase of the sensor rate (increase >20 beats/min, peak after 1 minute, return to baseline within 2-3 minutes), which was significantly different from the control group, showing only a slight rise in intrinsic heart rate immediately after tilting. Simultaneously to the rapid increase in sensor rate, the pacemaker patients showed a marked orthostatic decline of systolic blood pressure. During handgripping, heart rate and blood pressure curves were similar in both groups. In patients with this CLS pacemaker, rapid preload reduction during head-up tilting caused an overshooting sensor rate increase, reproducing the authors' clinical observation of postural pacemaker tachycardia in some patients. Consequently, they concluded that the rate response of the CLS pacing system can be inappropriately influenced by rapid shifts of blood volume, affecting right ventricular filling.

Aged↗

PubMed2003

Effect of non-hypotensive haemorrhage on plasma catecholamine levels and cardiovascular variability in man.

BACKGROUND: It is well known from animal research that non-hypotensive haemorrhage produces sympathoexcitatory responses assessable by both the rise in plasma catecholamine levels and the shift of autonomic influences on the heart to more sympathetic and less parasympathetic control. Data in humans are restricted. METHODS: Heart rate variability (HRV), systolic blood pressure (FINAPRES) variability (BPV), and catecholamine plasma levels were measured before and after haemorrhage in 30 healthy blood donors and compared with those from 10 control subjects without blood loss. Spectral power of HRV and BPV in very low (0.02-0.06 Hz), low (0.07-0.14 Hz), and high (0.15-0.40 Hz) frequency bands were calculated by Fourier analysis. Catecholamine plasma levels were assayed by dual column reverse-phased high-performance liquid chromatography (HPLC). RESULTS: Haemorrhage of 5.6 +/- 1.2 ml kg-1 body weight increased plasma norepinephrine levels (215 +/- 92 pg ml-1 versus 254 +/- 95 pg ml-1; P = 0.002), increased BPV in the low frequency band (Mayer waves; 1.8 +/- 1.0 ln [mmHg(2)] versus 2.0 +/- 0.9 ln [mmHg(2)]; P = 0.021), and decreased the vagally transmitted high frequency HRV (6.9 +/- 1.1 ln [MI(2)] versus 6.5+/-1.2 ln [MI(2)]; P<0.0001), but did not induce significant changes in heart rate (66 +/- 11 bpm versus 67 +/- 11 bpm; P = 0.79) and arterial blood pressure (mean values: 84 +/- 13 mmHg versus 87 +/- 13 mmHg; P = 0.12). CONCLUSIONS: As suggested by plasma norepinephrine levels, systolic BPV and HRV, non-hypotensive haemorrhage produces sympathoexcitatory responses as well as vagal withdrawal of heart rate control in humans.

Adaptation, Physiological↗

PubMed2002

Neural processing of auditory looming in the human brain.

Acoustic intensity change, along with interaural, spectral, and reverberation information, is an important cue for the perception of auditory motion. Approaching sound sources produce increases in intensity, and receding sound sources produce corresponding decreases. Human listeners typically overestimate increasing compared to equivalent decreasing sound intensity and underestimate the time to contact of approaching sound sources. These characteristics could provide a selective advantage by increasing the margin of safety for response to looming objects. Here, we used dynamic intensity and functional magnetic resonance imaging to examine the neural underpinnings of the perceptual priority for rising intensity. We found that, consistent with activation by horizontal and vertical auditory apparent motion paradigms, rising and falling intensity activated the right temporal plane more than constant intensity. Rising compared to falling intensity activated a distributed neural network subserving space recognition, auditory motion perception, and attention and comprising the superior temporal sulci and the middle temporal gyri, the right temporoparietal junction, the right motor and premotor cortices, the left cerebellar cortex, and a circumscribed region in the midbrain. This anisotropic processing of acoustic intensity change may reflect the salience of rising intensity produced by looming sources in natural environments.

Adult↗

PubMedDate not supplied

Hopelessness is associated with decreased heart rate variability during championship chess games.

OBJECTIVE: Clinical observations suggest that negative affects such as helplessness/hopelessness (HE/HO) may induce autonomic duration; affects were assessed for every move after reconstruction of the games. In all games compiled, 18 situation of intense confidence/optimism and 20 of intense helplessness/hopelessness were observed. RESULTS: Intense affects of HE/HO were associated with decreasing HF-HRV (Fisher exact test, p =.003), increasing "nervousness" (p =.0005), decreasing "optimism" (p =.0005), and decreasing "calmness" (p =.0005). CONCLUSIONS: Investigation of championship chess game players with an ELO strength > or = 2300 in a natural field setting revealed increasing HE/HO being associated with reduced HF-HRV suggestive of vagal withdrawal. Thus, our data may help link negative mood states, autonomic nervous system disturbances, and cardiac events.

Adolescent↗