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H Lyytinen

Publications and source records attributed to H Lyytinen.

At least 37 records · Page 2Linked to original sources
PubMed1997

Auditory event-related potentials (ERP) reflect temporal changes in speech stimuli.

We studied the brain's reactions to deviations in the duration of a stop consonant using event-related potentials in an oddball paradigm. A naturally produced nonsense word was used as a frequent standard stimulus which differed from two infrequently presented deviant stimuli only by the duration of the silence period inside the stop, making the consonant sound longer. Evoked responses to the deviant stimuli showed sharply rising negativity after the unexpected prolongation of the silence and a later negativity, the duration of which was related to the timing of the beginning of the second part of the deviant sound. This later negativity is, at least partly, elicited by a mismatch process to the omission of a sound at the expected latency.

Acoustic Stimulation↗
PubMed1997

Precursors of the evoked K-complex in event-related brain potentials in stage 2 sleep.

The aim of the study was to examine precursors of the evoked K-complex as manifested in event-related brain potentials (ERPs) during stage 2 sleep. ERPs to infrequent deviant tones of 1100 and 2000 Hz and immediately preceding frequent standard tones of 1000 Hz were compared between trials containing and trials not containing a K-complex (KC trials, NO KC trials, respectively) to the deviant tones. The N350 wave to the deviant tones was markedly larger during the KC than during the NO KC trials. Also the P210 wave to the 2000 Hz deviant tone showed the same phenomenon. No definite evidence was found for the mismatch negativity-like deflection during the KC trials. ERPs to the standard tones presented immediately (625 ms) prior to the deviant tones showed a larger early positive wave during the KC trials than during the NO KC trials. No corresponding phenomenon could be observed for the identical standard tone presented 1250 ms prior to the deviant tones. In all, the results suggest that the sleeping brain is momentarily more responsive to incoming sensory events preceding a K-complex than preceding a no K-complex response to a stimulus.

Adult↗
PubMed1997

Apolipoprotein E phenotypes and cardiovascular responses to experimentally induced mental stress in adolescent boys.

We investigated the relationship between apolipoprotein E (apoE) polymorphism and cardiovascular responses to experimentally induced mental stress. Mental stress was induced in 28 healthy 16-year-old boys with a series of stressors (e.g., mental arithmetic, Stroop Color-Word Interference Test). Heart rate (HR), finger blood volume, and skin conductance level were recorded continuously during the task performance. We found that boys with apoE3/2 or apoE3/3 showed marginally significantly greater HR reactivity and significantly greater task levels of HR and HR variability (HRV) during the mental stress than subjects with apoE4/2, apoE4/3, or apoE4/4. In addition, E4/2, E4/3, and E4/4 subjects manifested a distinct stress-related decrease in HRV relative to baseline values while E3/2 and E3/3 subjects showed a slight increase. The results suggests that apoE polymorphism is associated with cardiovascular responsivity to mental stress in adolescent boys.

Adolescent↗
PubMed1997

Mismatch negativity during objective and subjective sleepiness.

The mismatch negativity (MMN) and P3 of auditory event-related potentials were studied during subjectively and objectively (physiologically) defined sleepiness under optimal stimulus conditions for MMN elicitation. The MMN and P3 were elicited by either small or large unattended auditory deviants presented to the left ear. The participant's task was to detect either rare auditory targets presented to the right ear or rare changes in the light flashes. Eleven young adults served as participants in a nighttime experiment. The MMN declined especially at Fz and Cz but not so markedly at the right mastoid as either subjective or objective alertness decreased. The amplitude of P3 also decreased during sleepiness. The attenuation of the MMN was paralleled by a decline in behavioral performance. The results show that the MMN is attenuated by a decrease in alertness even before an actual sleep state is reached.

Acoustic Stimulation↗
PubMed1997

Heart rate responses to real and simulated BA Hawk MK 51 flight.

BACKGROUND: The effects of psychological workload on inflight heart rate were studied in five experienced (flight instructors) and five less experienced (cadets) military pilots of the Finnish Air Force (FAF). METHOD: The subjects performed the same flight mission twice; first with the BA Hawk MK 51 simulator with minimal G-forces and after that with the BA Hawk MK 51 jet trainer with Gz-forces below +2. The mission included: a) 2 min rest after seating; b) take-off; c) ILS approach in the minimum weather conditions (initial, intermediate and final approach); d) landing tour (visual approach); and e) landing. The heart rates were continuously measured using a small portable recorder developed at the University of Jyväskylä, Finland. The R-R intervals were stored and analyzed with an accuracy of 1 ms. The different phases of each flight were marked in the data by using codes given beforehand for each critical event. RESULTS: The take-off resulted in a significant increase in the heart rate from the resting levels both in the cadets and the flight instructors in both planes. In the simulator the heart rate decreased during the initial approach and slightly increased after it during the intermediate approach. Thereafter the heart rate decreased during the landing tour which seemed to be the least psychologically demanding phase of the simulated flight. The heart rate increased again during the landing but did not exceed the heart rates measured during the take-off and the ILS-approach. There were no statistical differences between the groups. In the jet trainer no decrease in the heart rate could be observed immediately after the take-off, unlike in the case of the simulated flight. The inflight heart rate increased during the final approach, decreased during the landing tour and finally increased during the landing. According to the heart rate analysis the final approach was the most loaded phase of the real flight. The changes towards the phases of final approach and landing were greater among the flight instructors. CONCLUSION: There were no statistically significant differences between the mean heart rates during the real and the simulated flight. It is suggested that the heart rate changes for most reflected the changes in cognitive workload.

Adult↗
PubMed1996

Postural stability and skilled performance--a study on top-level and naive rifle shooters.

Posture control during aiming over a period of 7.5 s preceding the shot was studied among national top-level rifle shooters as well as among national level shooters and amateurs familiar with rifle shooting. Movement of the center of forces (COF) was analyzed in terms of the speed and amplitude of the movement. These calculations were carried out in 1.5 s windows, the first window beginning 7.5 s and ending at 6.0 s prior the shot. The last window ended at the trigger pull. Posture control data differentiated the studied groups according to their level in competitive shooting. The male top-level shooters could stabilize their posture significantly better than female top-level or male national level shooters, who were, in turn, much more stable than naive shooters. The experienced shooters were able to stabilize their posture even better during the last seconds preceding the shot, whereas in naive shooters there were no significant differences when the successive windows were compared with each other. When a comparison was made between the best and worst 20 shots of each subject, a significant difference in balance parameters was only observed among the naive shooters, who showed more pronounced movement of the COF in the less successful trials. Among the highly trained top-level shooters a miss in whole-body posture stabilization apparently seldom is a reason for a poor result.

Adult↗
PubMed1996

Insulin resistance syndrome and autonomically mediated physiological responses to experimentally induced mental stress in adolescent boys.

We investigated the relationship between hemodynamic and other autonomically mediated responses to experimentally induced mental stress and the parameters of the insulin resistance syndrome (IRS) in 48 healthy adolescent boys. Mental stress was induced with mental arithmetic and the Stroop Color-Word Test. Heart rate (HR), finger blood volume (FBV), and skin conductance level (SCL) were recorded continuously during task performance. IRS parameters measured were serum insulin, high-density lipoprotein (HDL) cholesterol, serum triglyceride (TG), systolic blood pressure (SBP), subscapular skinfold (SSF), and subscapular to triceps skinfold ratio (STR). The results indicated that a high level and an increasing linear trend of HR and FBV during task performance were related, independently of each other and of body mass index (BMI), to a high insulin concentration. An increasing linear trend of HR during mental stress was also related to high SSFs independently of MI. In addition, a high SCL during task performance was associated with high TG levels, SSFs, and STRs. It is discussed whether stress-induced sympathetic overactivity might contribute to the development of the IRS.

Adolescent↗
PubMed1996

Processing of auditory stimuli during tonic and phasic periods of REM sleep as revealed by event-related brain potentials.

The brain has been reported to be more preoccupied with dreams during phasic than during tonic REM sleep. Whether these periods also differ in terms of the processing of external stimuli was examined. Event-related brain potentials (ERPs) to a frequent standard tone of 1000 Hz (P = 97%) and infrequent deviant tones of 1100 and 2000 Hz (P = 1.5% for each) were recorded (n = 13) during wakefulness and nocturnal sleep. An ERP wave (called REM-P3) resembling a waking P3 wave was larger for the 2000 Hz deviant during tonic than during phasic REM sleep. Also the P210 wave was larger during tonic than during phasic REM sleep. A reliable mismatch negativity component appeared only in wakefulness. In summary, these results support the hypothesis that the brain is more 'open' for changes in an auditory input during tonic than phasic REM sleep.

Adult↗
PubMed1995

Brain reacts to occasional changes in duration of elements in a continuous sound.

In order to study the event-related potential correlates of human ability to detect temporal changes within a continuous sound a sound consisting of two alternating pitches of the same constant duration, with infrequent shortenings of one of the tones, was presented to the subjects. The infrequent shortenings were found to elicit a negative component of the auditory event related potential, called the mismatch negativity (MMN). The experimental parameters were chosen to produce a MMN with a minimal contamination of N1, the main negative deflection of an evoked response with the same latency range as MMN and with a short experimental time. The duration of the whole experiment with three different deviant tones was only 11 min. The fast experiment is useful for subjects, for whom a long experiment may be too demanding (infants or patients).

Acoustic Stimulation↗
PubMed1995

Brain slow potentials reflecting successful shooting performance.

Preparatory brain activity from frontal, centro-lateral, and occipital areas were recorded from top-level rifle shooters during shooting performance. The aim of the study was to examine the relation of brain slow potentials to qualitative (rifle holding) and quantitative (hit) aspects of superior shooting performance. For this purpose, a typology of slow potentials (SPs) was developed. The resulting SP types were used for unraveling the associations between the electrocortical activity and behavioral output. The main finding was that frontal positivity was associated with successful performance, but only if the central-right SP was more negative than the central-left one. This finding was explained as showing that, in the case of superior performance, a shooter is able to refrain from irrelevant motor activity (frontal positivity) and concomitantly concentrate on the visual-spatial processing (right-sided negativity). In all, the present experiment suggests that the SPs are consistently related to the covert aspects of shooting performance, which lack an overt manifestation. At the practical level, this means that the SPs provide a tool for accessing information concerning the optimal balance between visual-spatial targeting and motor activity which can make a valuable contribution to the understanding of superior shooting performance.

Action Potentials↗
PubMed1995

Psychophysiological arousal related to Type A components in adolescent boys.

The association between psychophysiological responses (heart rate, skin conductance and blood volume) and Type A behavior was studied in adolescent boys (n = 48) in computer-controlled experiments. Although psychophysiological arousal was related to the type of stress-evoking element, task-specificity did not result in significant psychophysiological differences between Type As and Nontype As. The indication is that physiological arousal may be a constitutional characteristic of Type A behavior. The multidimensionality of type A behavior must be considered in any investigation examining the psychophysiological Type A-Nontype A differences. Different Type A dimensions, together with previously found psychological differences, were related to specific psychophysiological reactions.

Adolescent↗
PubMed1994

Is the appearance of mismatch negativity during stage 2 sleep related to the elicitation of K-complex?

There is no convincing evidence for the occurrence of mismatch negativity (MMN) elicited by infrequent deviant tones in a homogenous tone stream during sleep in adult humans. Also the data presented here failed to show an MMN during any stage of sleep when event-related potentials (ERPs) were averaged across all trials of the same sleep stage. The aim of the study was to determine whether the MMN appearance during sleep is related to the variations in microstates of sleep that differ in terms of stimulus elicited phasic EEG events. The focus was on stage 2 sleep. The single responses to a deviant tone were classified into 3 types during stage 2 prior to averaging ERPs. These 3 response types included K-complex, other phasic EEG events and no visually discernible phasic EEG events. The results showed that an MMN-like deflection indeed appeared during stage 2 but only when the deviant tone also elicited a K-complex. This type of deflection was not seen when the deviant tone was presented without the intervening standard tones. This supports the hypothesis that a true MMN to the deviant tone was seen during stage 2 sleep preceding a K-complex.

Adolescent↗
PubMed1994

Asymmetry of instructed motor response to auditory stimuli during sleep.

Previous studies have demonstrated that motor activity during sleep is lateralized to the nondominant hand. There are two basic theories concerning this phenomenon: 1) The nondominant hemisphere is nonspecifically more alert or responsive than the dominant one, and 2) the lateralization to the nondominant side is task specific, reflecting the spatially oriented mode of information processing that is responsible for movements during sleep. We examined the motor responses to auditory stimuli during waking and sleep of 10 right-handed healthy subjects, who were instructed to switch off a tone stimulus by pressing a transducer that was attached to each hand. Sleep stage scoring was performed according to Rechtschaffen and Kales's criteria. During wakefulness and in all stages of sleep, with and without alpha activity occurring after stimulus onset, the dominant hand was used more, but during nonrapid eye movement S1 sleep the difference was not statistically significant. When alpha activity was present in the electroencephalogram after stimulus onset, the responses were significantly more lateralized to the right hand than when there was no alpha activity. During an actimetric home recording of both wrists of the subjects, there was an excess of left-sided movements during sleep as compared to waking. The results do not support the idea that the right hemisphere is generally more responsive than the left during sleep. They are, however, in accordance with the hypothesis that spatial information processing is a crucial factor in the nondominant lateralization of spontaneous sleep movements.(ABSTRACT TRUNCATED AT 250 WORDS)

Acoustic Stimulation↗
PubMed1993

Speech perception and brain laterality: the effect of ear advantage on auditory event-related potentials.

Dichotic listening has been used for assessing asymmetries in processing auditory stimuli. It is known that there is better recognition of dichotic stimuli in the right ear with verbal stimuli (right ear advantage, REA) by the majority of the subjects. We were interested in the psychophysiological correlates of ear advantage as it is manifested in event-related potentials (ERP). We compared ERPs to monaural and dichotic syllables in stable REA and LEA subjects. The most consistent finding was that REA subjects show larger positive ERP deflections over the left hemisphere (maximal at T5) and LEA subjects over the right hemisphere (maximal at T6) both at the latency range of 320-340 msec. Thus, brain event-related potentials support the contention that the REA and LEA reflect differential activation of the left and right hemispheres, respectively.

Acoustic Stimulation↗
PubMed1993

Brain slow waves preceding time-locked visuo-motor performance.

According to previous findings (Konttinen and Lyytinen, 1992), the slow brain negativity preceding the trigger pull in rifle-shooting tends to be decreased in successful shots among experienced marksmen, whereas no such pattern is found among inexperienced subjects. This effect was interpreted as resulting mainly from optimal arousal. However, another explanation is examined here. The aim of the experiment was to investigate slow electrocortical changes associated with motor regulation and visual aiming related to shooting performance. Four variations on a shooting task were used, in which the visual and motor components were contrasted. Motor activity related to gun stabilization was found to be associated with slow-wave positivity, whereas visual aiming was manifested as slow negativity. The results offer some basis for interpreting the individual slow brain wave patterns that predict shooting performance.

Action Potentials↗
PubMed1992

Event-related potentials and autonomic responses to a change in unattended auditory stimuli.

Event-related brain potentials (ERPs) and autonomic nervous system (ANS) responses to occasional pitch and rise-time changes in a task-irrelevant auditory stimulus repeating at short intervals were measured while the subject performed a difficult intellectual task (Raven Matrices). It was found that deviant stimuli elicited the mismatch negativity (MMN) component of the ERP even when they elicited no ANS response. There was no significant difference in the mismatch negativity between trials in which the skin conductance response was or was not elicited. The pitch deviant tone also elicited heart rate deceleration, whereas the rise-time deviant tone tended to elicit a later heart rate acceleration. Neither heart rate change correlated with the mismatch negativity. The pattern of results obtained suggests that the mismatch negativity is generated by an automatic discrimination process associated with the cerebral events initiating the orienting response to stimulus change, but does not necessarily lead to the orienting response elicitation. Longer-latency ERP components tended to show slight covariation with ANS responses. The P3 was larger when a skin conductance response was elicited than when it was not elicited. Further, heart rate change trials tended to be accompanied by larger slow waves than trials with no heart rate response. Heart rate acceleration trials were accompanied by a larger slow parietal positivity and a smaller frontal negativity than were heart rate deceleration trials.

Adolescent↗