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Biomedical subjects

L Leinonen

Publications and source records attributed to L Leinonen.

At least 37 records · Page 2Linked to original sources
PubMed1989

Auditory evoked potentials and magnetic fields in patients with lesions of the auditory cortex.

Auditory evoked potentials and magnetic fields of 40-200 ms latencies were measured from 4 patients with temporal lobe infarcts and compared with results from healthy subjects. Magnetic fields over the diseased hemisphere were abnormal in all 4; the responses were missing in 2. In one patient the responses were of abnormally high amplitude, and in one parts of the response sequence were missing. Evoked potentials were also abnormal in all 4 patients and the results were in accordance with the findings in the magnetic field measurements.

Adult↗
PubMed1989

Ethanol induced EMG changes and muscle force in a patient with polyneuropathy.

A patient with chronic relapsing polyneuropathy noticed that when he took some alcohol in the evening his muscle force increased substantially during the next day. To measure this beneficial effect of ethanol we measured the force of hand grip, conduction velocities and distal latencies of ulnar and median nerves, and the power spectra of EMG during maximal and submaximal hand grip before and after alcohol ingestion. A 50% increase in the muscle force was documented 24 hours after the alcohol administration, with a concomitant increase of high frequency components in the power spectrum of EMG. Slight decreases in distal latencies were also measured.

Adolescent↗
PubMed1989

Interaction of lidocaine and hypothermia in Bier blocks in volunteers.

The present investigation was designed to study the interaction of temperature, lidocaine, and ischemia during intravenous regional anesthesia (IVRA) of the arm. Five volunteers were studied during exposure of one of their arms to four different experimental conditions: hypothermia and ischemia; hypothermia, ischemia, and lidocaine; normothermia and ischemia; normothermia, ischemia, and lidocaine. Each subject was tested on four different occasions with only one test condition imposed per occasion and with 3 or more days between experiments. Somatosensory evoked responses (SERs) and muscle responses to ulnar nerve stimulation were measured, and sensory testing was done to determine whether the neural effects of the particular treatments differed. Anesthesia developed sooner and was more extensive when local anesthetic was injected. A 5-10 degrees C decrease in tissue temperature did not accentuate the anesthetic effects of lidocaine as determined by time to loss of pinprick and touch sensation. With ischemia alone, anesthesia of the finger tips with preservation of sensation on the arm was observed in all subjects 20 min after tourniquet inflation. Anesthesia at all cutaneous test sites was achieved in 7 of 10 lidocaine experiments; no systematic order of sensory loss, such as progression from distal to proximal sites, was observed. Decrease in limb temperature slowed the development of lidocaine effects on evoked responses and recovery from the effect. Under conditions of ischemia, deterioration of sensation generally began earlier under cold rather than warm conditions. Primary differences between changes in the SERs and muscle responses under condition of ischemia versus ischemia and lidocaine were the rate and magnitude of change of potential latency and amplitude.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Magnetic responses of the human auditory cortex to noise/square wave transitions.

We recorded evoked magnetic fields from the human auditory cortex to noise/square wave sequences. Two prominent deflections were observed: one 100 msec after the noise onset (N100m) and another 100 msec after the noise/square wave transition (N100m'). The amplitude of N100m' increased with decrease in square wave frequency from 2 kHz to 0.125 kHz and with increase in square wave duration from 4 msec to 200 msec. The latency of N100m' was on the average 23 msec longer for noise durations of 60 msec than 310 msec, whereas the amplitude of N100m' did not change. Increase in interstimulus interval from 1.1 to 8.8 sec enhanced the amplitude of N100m significantly more than that of N100m'. The small interaction between N100m and N100m' and their different recovery cycles suggest that different activation patterns underlie these two 100 msec responses at the auditory cortex.

Adult↗
PubMed1987

Cerebral magnetic responses to stimulation of ulnar and median nerves.

We have compared spatial patterns of somatosensory evoked magnetic fields (SEFs) to stimulation of the ulnar and median nerves at the wrist. An oddball paradigm was used additionally to examine whether an infrequent change in the stimulation site would alter the field pattern. The response consisted of 3 parts: an early small deflection at 22-28 msec, a large deflection peaking between 34 and 86 msec, and a late deflection at 110-180 msec. The wave forms and amplitudes of the responses to ulnar and median nerve stimulation were similar, without any additional deflections for the infrequent stimuli. The field patterns, which were interpreted in terms of the dipole model, could be explained by activation of the primary sensorimotor cortex during all peaks of the response. For the early parts of the response at 22-46 msec, the locations of the equivalent sources for median and ulnar nerve stimulation differed from each other, in agreement with the known somatotopy of SI. No somatotopical order was found for the sources of the later deflections.

Adult↗
PubMed1987

Nocturnal periodic breathing in adults with Down's syndrome.

Nineteen adults with Down's syndrome were studied with the static charge sensitive bed (SCSB) method. A single whole-night recording was made of each subject. Two different periodic breathing indices (PBIf and PBI%) were calculated from a computerized analysis of these recordings. A polygraphic recording was also made of one subject, a 52-year-old male. The EEG, the EOG, the EMG, nasal and oral airflow, and diaphragmatic movement were recorded, the latter with an abdominal strain gauge and with the SCSB-method simultaneously. Good correlation was found between the recording with the SCSB and the strain gauge. The apnoea index (AI) calculated from the polygraphic recording was 23.3, while the PBIf of this patient recorded on another night and analysed automatically was 45 and the PBI% was 78.6. The patient group was divided into those aged 40 or older (n = 10) and those aged 39 or younger (n = 9). The mean PBI% of the older group was 24.0 while that of the younger group was 5.4 (t = 2.23; P less than 0.05). The mean PBIf of the older group was 16.7 and that of the younger was 3.6 (t = 2.70; P = less than 0.02). The mean body mass index (BMI) of the younger group was significantly higher than the mean BMI of the older group. The mean BMI of those patients, whose PBI values were considered to be normal (PBI% less than 3, PBIf less than 7), did not significantly differ from the BMI of those patients, whose PBI-values were abnormal.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

Neuromagnetic responses of the human auditory cortex to on- and offsets of noise bursts.

Cortical sources of neuromagnetic responses to noise bursts were compared in 7 healthy humans. The earliest response, P40m, peaking about 40 ms after the stimulus onset, was followed by a prominent deflection in the opposite direction at about 100 ms (N100m) and by another peak at 200 ms (P200m). A sustained field, seen near the end of the 400- to 550-ms stimuli, ended with an off-response of the same polarity as N100m. All deflections could be explained by cortical activity within the Sylvian fissure. The source of P200m was anterior to other sources of the on-response, except P40m. When noise bursts, or pauses of equal duration in a continuous noise were presented to the subject, striking similarities were found between the 100-ms deflections of the on- and off-responses: both peaked at about the same latency; their estimated sources were closed to each other in the supratemporal plane and their amplitudes depended in a similar way on the interstimulus interval (1.1-8.8 s). However, only the on-response was preceded by P40m, suggesting that P40m and N100m are not causally linked. N100m seems to reflect cortical activity related to any abrupt change in the auditory environment.

Auditory Cortex↗
PubMed1986

Automatic analysis of sleep records with static charge sensitive bed.

An automatic analysis of movements detected by the static charge sensitive bed (SCSB) was developed for the study of sleep and breathing disturbances (apnoeas) during sleep. Three signals on separate channels are analysed: one relating to body movements, one to respiratory movements and one to movements of the heart (ballistocardiogram). The analysis can be made on-line or from tape recordings. With a portable microcomputer the records and analyses can be carried out at home or on the ward without any professional personnel. The system can be preset to start and to end recording automatically. The subject just has to lie down. The automatic analysis of body movements on the basis of their amplitude and duration yields criteria for scoring of sleep into 'wakefulness,' 'quiet sleep' and 'active sleep.' A simple hypnogram and the statistics on the durations and proportions of these stages are printed. Simultaneous SCSB and polygraphic records were made on healthy subjects. Comparison of the two types of sleep scoring showed that the results agreed during 81% of the time. The amplitudes of the movements detected on the 3 channels are integrated in epochs and the results of this analysis are represented in a compressed graphic form which allows easy visualization of the overnight records. The pattern of 'respiratory movements' reveals whether the breathing has been regular, irregular or periodic.

Adult↗
PubMed1986

Sleep in Macaca arctoides and the effects of prazosin.

Polygraphic (EEG, EOG, EMG) 12-hr recordings were made in 3 adult monkeys (Macaca arctoides) to document their normal sleep pattern and to examine the effects of prazosin, an alpha-1-adrenoceptor antagonist. In comparison to man, REM episodes appeared at shorter intervals (50 min) and they always ended in movement arousal or waking up. As in man the proportion of deep sleep decreased and the proportion of REM sleep increased towards morning. During eight hours after parenteral administration of prazosin, at doses without any noticeable behavioral side effects, the number of REM episodes and the amount of REM sleep was 30 to 80 percent greater than during the control nights. The changes were statistically nonsignificant. However, since the results were similar in all three monkeys, it can be suggested that prazosin had some effect on the cyclicity of sleep. Dose 1 mg/kg resulted in behavioral side effects and disturbed sleep.

Animals↗
PubMed1984

Temporal integration and contrast sensitivity in foveal and peripheral vision.

Spatial contrast sensitivity functions and temporal integration functions for gratings with dark surrounds were measured at various eccentricities in photopic vision. Contrast sensitivity decreased with increasing eccentricity at all exposure durations and spatial frequencies tested. The decrease was faster at high than at low spatial frequencies, but similar at different exposure durations. When cortically similar stimulus conditions were produced at different eccentricities by M-scaling, contrast sensitivity became independent of visual field location at all exposure durations tested. The results support the view that in photopic vision spatiotemporal information processing is qualitatively similar across the visual field, and that quantitative differences result from retino-topical differences in ganglion cell sampling. For gratings of constant retinal area temporal integration (improvement of contrast sensitivity with increasing exposure duration) was more extensive at high than at low retinal spatial frequencies but independent of cortical spatial frequency and eccentricity. For M-scaled gratings temporal integration was more extensive at high than at low cortical spatial frequencies but independent of retinal spatial frequency and eccentricity. The results suggest that the primary determinant of temporal integration is not spatial frequency but grating value that is calculated as AF2 square cycles (cycle2), where A is grating area and F spatial frequency.

Fixation, Ocular↗
PubMed1981

Determinants of sexual behavior of Macaca arctoides in a laboratory colony.

Copulatory behavior of wild-born individually caged laboratory stumptail monkeys (Macaca arctoides) was investigated. The monkeys were paired daily for 20 min, and altogether 536 pairings were observed. The influence of the female's menstrual cycle and social factors of male sexual activity was determined. The reactions of the other monkeys during a pairing, and masturbation behavior of the males were observed and described. It was found that when a male and female were paired daily their sexual activity remained on a rather constant and high level for months provided the pair could not see, touch, or smell each other between pairings. In these conditions the most common copulatory behavior consisted of 3-4 ejaculations. When the couple lived continuously in adjacent cages, which allowed them visual, tactual, and olfactory communication between pairings, the male ejaculated, on the average, only once during five successive pairings. Thus separation and reunion was potent in triggering sexual activity. When the couple was visually separated between sessions the male's sexual activity did not depend on the menstrual cycle of the female. The males initiated copulation and the females were always willing, except in later stages of pregnancy, to cooperate. All males masturbated to ejaculation and it was often triggered by copulation, masturbation, or any happening causing arousal in the colony. The females were never seen to masturbate outside of the heterosexual context.

Animals↗
PubMed1980

Functional properties of neurons in the temporo-parietal association cortex of awake monkey.

The temporo-parietal association cortex around the caudal end of the Sylvian fissure was studied with the single cell recording technique in three awake behaving Macaca speciosa-monkeys. Of the 197 cells isolated, 5% were active only during the monkey's own movements, mostly during head rotation, and 95% were responsive to sensory stimulation: 54% to auditory stimuli, 24% to somatosensory stimuli, 13% to both of these and 4% to visual stimuli. Some cells, classified as responsive to somatosensory stimuli, were activated only by passive rotation of the head on the cervical axis; it is possible that they were driven by vestibular stimuli. Half of the cells were activated by stimuli on both sides of the monkey, and almost all the rest, only by stimuli on the side contralateral to the hemisphere recorded. Of the acoustically drivable cells, 95% responded to natural sounds, such as, rubbing hands together, rustle of clothes, clicks or jingles (sounds with noise spectrum and rapid intensity transitions). Most of these neurons were also examined with pure tones of 0.2-20 kHz: various inhibitory or excitatory responses were elicited in half of them, usually over a wide range of frequencies. The responses of most acoustically drivable cells (62%) depended on the location of the sound source with reference to the monkey's head so that the maximal response was elicited by sounds with a certain angle of incidence, usually on the contralateral side. The present results suggest that the area studied participates in the analysis of the temporal pattern of a sound, the location of the sound source and in spatial control of head movements.

Animals↗
PubMed1980

Functional properties of neurones in the posterior part of area 7 in awake monkey.

The posterolateral part of the parietal association cortex (area 7 of Brodmann) was investigated in three awake, behaving macaque monkeys using transdural microelectrode recording technique. Only one of the 114 cells isolated remained unidentified. Of the cells 79% responded to somesthetic (39%) or visual (23%) or both somesthetic and visual (17%) stimulation. The somesthetic receptive fields were large, covering, for instance, the whole arm or hand. Most receptive fields were on the upper extremities. Half of the somesthetically drivable cells had bilateral receptive fields. The visually drivable cells responded only to stimuli moving in a certain direction. The effective stimuli for most of the cells responding both to visual and somatosensory stimulation were: touching of the skin and visual stimuli moving towards the cutaneous receptive field. Of the cells 20% were active only during the monkey's own movements, most often during grasping and manipultion with fingers. The results indicate that the area studied is specialized in the control of hand movements, e. g. grasping, grooming and somesthetic recognition of the forms of objects.

Animals↗
PubMed1980

Functional properties of neurones in the parietal retroinsular cortex in awake monkey.

The parietal retroinsular cortex of three, awake, behaving macaque monkeys was investigated using transdural microelectrode recording technique. All 73 cells identified responded to somatosensory stimuli. Most of the neurones (51) were activated by compression of the skin in an on, off or on-off fashion; these cells were unresponsive to light touching or stroking of the skin. The rest of the cells responded to light touching, rotation of a joint or palpation of a muscle belly. All body parts were represented in this area. Of the cells 30% responded to stimulation of both sides of the body. The results indicate that the parietal retroinsular cortex participates in the analysis of skin compression. This information is used, i.e. in the control of manipulative movements and in discrimination of supported weights. It is possible that ablation of the area examined would impair these functions.

Animals↗
PubMed1979

I. Functional properties of neurons in lateral part of associative area 7 in awake monkeys.

The lateral part of area 7, area 7b, of alert, behaving macaque monkeys was investigated using transdural microelectrode recording technique. Two hundred twenty-eight cells from five hemispheres of four monkeys were isolated and studied. The functional properties of 2% of the cells isolated remained unidentified. Functions of the identified cells were prominently related to the spatial control of arm movements. Of the cells 70% responded to somatosensory (40%) or visual (16%) or both somatosensory and visual (14%) stimulation. The receptive fields of these passively drivable cells were large, covering e.g., the arm or leg or chest or even the skin of the whole body. Most of the visually drivable cells responded to stimuli in both halves of the visual field. Of the cells responding to sensory stimulation 80% were activated by stimuli moving in a certain direction. Of the directionally selective cells 25% received information through more than one sensory channel. The complex stimulus-response relationships of these "convergence" cells revealed the existence of an integrative system which analyzes the direction of a stimulus moving in one sensory system using an other sensory system as a reference. Of all the cells isolated 28% discharged only during active movements of the arms (25%) or eyes (3%). Firing of these neurons was related to contraction of a functionally uniform group of muscles and not individual muscles. Some previous investigations of the parietal association cortex, conducted mainly in area 7a, have shown that most cells were active only when the monkey himself moves his eyes or arms. In our study on area 7b most cells responded to passive stimulation. The discrepancy between the results indicates functional differentiation within area 7.

Animals↗
PubMed1979

II. Functional properties of cells in anterolateral part of area 7 associative face area of awake monkeys.

The most anterior part of area 7 of awake, behaving macaque monkeys was investigated using single cell recording technique. Eighty-five cells from three hemispheres of two monkeys were isolated and studied. These cells showed more complex functional properties than the cells in the primary and secondary cortical fields. Of the cells 61% responded to somatosensory (26%) or visual (2%) or both somatosensory and visual (33%) stimulation; 39% of the cells were active only during the monkey's own movements. Most of the cells studied were active while the monkey was bringing an object to the mouth with its hand, when reaching for an object with lips, or while chewing. The neurons responded selectively to, e.g., palpation of the flexors of the arm, a visual stimulus approaching the face, passive movement of the monkey's hand towards the mouth, or they were active only when the monkey was reaching for an object with its lips or was mouthing it. The cellular activity in the anterolateral part of area 7 was prominently related to the stimulation or motor activity of the face (especially the mouth). In this respect, it differed from the more posterior part of area 7 adjacent to it. The results thus indicate that there is a separate and rather extensive mouth (or face) area in the parietal association cortex of the monkey.

Animals↗
PubMed1979

Comparison of effects of pentobarbital and ethanol on the neuronal activity in the posterior parietal association cortex.

The problem of this study was whether the effects produced by alcohol in the posterior parietal association cortex are specific to this drug or shared by other centrally acting depressant drugs such as barbiturates. The effect of graded doses of pentobarbital on multineuronal impulse activity was recorded with transdural microelectrode technique in 30 expts. in Brodmann's area 7 of five stump-tailed monkeys (Macaca speciosa). The results were compared with those from 32 expts. performed with alcohol and published separately. The dosage of the two drugs was determined on the basis of the monkeys' sensori-motor coordination which was assessed with a rating scale of reaching accuracy for food rewards. There were several recording sites where the actions of the two drugs were similar at similar behavioural levels of intoxication. However, in the distribution of effects among various functional types of recording sites a significant difference was found between pentobarbital and alcohol. Alcohol commonly diminished cellular activity related to motor behaviour (reaching, grasping) and only rarely responses to somesthetic stimuli, whereas the effects of pentobarbital were the opposite being most common on somatosensory responses and least common on activity related to motor behaviour. Also responses to visual stimuli were more sensitive to pentobarbital than to alcohol. The actions of pentobarbital and alcohol on responses evoked by sensory stimulation differed significantly (P less than 0.01). We conclude that significant differences exist in the mechanisms of action of alcohol and barbiturate on the associative systems of the brain.

Animals↗