Biomedical subjects

D Hammerborg

Publications and source records attributed to D Hammerborg.

11 recordsLinked to original sources

PubMed1997

Left hemisphere advantage for classical conditioning to auditory verbal CSs: effects of nonattended extinction.

The effects of brain laterality, or hemispheric asymmetry, on electrodermal classical conditioning during both attended and nonattended stimulus conditions were studied. Participants were conditioned to consonant-vowel (CV) syllables during an acquisition, or learning, phase of the experiment. During a subsequent extinction phase, the conditioned stimuli (CS) were presented in a dichotic mode of presentation. Half of the participants attended to the left ear (right hemisphere) during the extinction phase and the other half of the participants attended to the right ear (left hemisphere). The results showed effects of conditioning for all participants during the acquisition phase. During dichotic extinction, the left hemisphere group showed remaining learning effects in both the attended and nonattended conditions, whereas the right hemisphere group demonstrated conditioning only in the attended condition.

Acoustic Stimulation↗

PubMed1997

Event-related potential (ERP) asymmetries to emotional stimuli in a visual half-field paradigm.

To investigate the hypothesis of a right hemispheric superiority in negative emotional processing, event-related potentials (ERPs) were recorded from 17 sites (Fz, Cz, Pz, F3/4, F7/8, C3/4, T7/8, P3/4, P7/8, O1/2) in a visual half-field paradigm. While maintaining fixation, right-handed women viewed pictures of patients with dermatological diseases before (negative) and after (neutral) cosmetic surgery. A principal components analysis with Varimax rotation performed on ERPs revealed factors identified as N1, N2, early P3, late P3, and slow wave. Repeated measures analyses of variance performed on factor scores revealed a significant effect of emotional content for all factors except for N1. However, asymmetries in emotional processing were restricted to N2 and early P3, with maximal effects over the right parietal region. N2-P3 amplitude was augmented for negative and reduced for neutral stimuli over right hemisphere regions. Visual field presentation interacted with these asymmetries in enhancing amplitudes contralaterally for early but ipsilaterally for late ERP components. Overall, findings for N2 and P3 support theories of an asymmetry in emotional processing.

Adult↗

PubMed1994

ERPs for infrequent omissions and inclusions of stimulus elements.

A negative event-related potential (ERP) wave called mismatch negativity (MMN) is elicited by an infrequent deviant stimulus in a sequence of frequent standard stimuli. Omission of a stimulus in a sequence of stimuli, however, has been considered to elicit a negativity different from MMN. The present study addressed this issue by examining ERPs for infrequent omissions and inclusions of compound stimuli or their elements. Three kinds of stimuli were presented: a 1000-Hz sine wave tone (Sine), white noise with the 1000-Hz frequency sharply filtered out (Noise), and a composite of the pure tone and the filtered white noise (SiNoise). All stimuli had 50 ms duration and were presented with a regular interstimulus interval of 650 ms. Intensities were 75 dB SPL for the tone and noise stimuli and slightly higher for the composite stimulus. The three kinds of stimuli were presented on separate runs, either as the frequent stimulus or one of two infrequent stimuli, each with 10% probability. Infrequent omission of the large stimulus element (Sine deviant to SiNoise) tended to elicit later MMN than inclusion of the same element (SiNoise deviant to Sine). Omission of the small stimulus element (Noise deviant to SiNoise) elicited a smaller and later MMN than did inclusion of the same element (SiNoise deviant to Noise). These data suggest that MMNs are also elicited by partial stimulus omissions, although they seem to be more sensitive to other kinds of stimulus deviances.

Adult↗

PubMed1993

European isolation and confinement study. Mental performance.

Six EMSInauts were confined for 28 days in a hyperbaric chamber complex at a low overpressure. During this period they were repeatedly given four different standard mental performance tests: (1) Operational Test of sustained attention vigilance; (2) short-term memory; (3) visual reaction time; and (4) cognitive evoked brain potentials (N100 and P300). The aim of the study was to determine whether there were any general or specific effects on mental performance during the isolation period. For the simple mental performance tests (operational test and visual reaction time), a distinct learning effect over the 28 days of isolation could be detected. On the more cognitive demanding tasks such as in the short-term memory test, patterns of impairment were found. Of the cognitive evoked brain potentials recorded, the noncognitive N100 wave latency was unchanged throughout the isolation period. The P300 wave latency, related to cognitive functioning, showed lower values in the middle and higher values at the end of the isolation period, compared with the pre-isolation values. Although a few individual, transient impairments of function were noticed in the more demanding tests, it is concluded that the mental performance of the six EMSInauts appeared to remain basically unchanged throughout the isolation phase, both at the group level and the individual level.

Evoked Potentials, Auditory↗

PubMed1992

Hemisphere differences in event-related potentials (ERPS) to monaural presentations of simple speech sounds.

The aim of the present study was to compare ERPs over the left and right hemispheres to monaural consonant-vowel (CV) syllables. It was predicted that, if the contralateral auditory representation is stronger than the ipsilateral one, then ERPs over the left hemisphere should be larger for right-ear stimulus input. Furthermore, if the hemispheres differ in efficiency in processing of speech sounds, then ERPs recorded at any given site should vary as a function of the ear to which the sound is presented. Twelve right-handed subjects participated. The CV-syllables used were /Ba/ and /Pa/ with 15 presentations of each syllable to each ear in a randomized order. EEG was recorded from F3, Fz, and F4 with linked ears as reference. The results showed no significant asymmetry in the ERP-leads. N1- and N2-amplitudes were, however, larger at Fz than at F3 and F4, and N1-latency was shorter for right-ear presentations, which also interacted with the /Pa/-syllable presentations. P3-latency was longer to the /Pa/-syllable compared to the /Ba/-syllable, while N4-latency was longer to the /Ba/-syllable. N4-amplitude was more negative for the /Pa/-syllable presented to the left ear. The results are discussed in terms of phonemic differences between the unvoiced /Pa/ and voiced /Ba/, and early versus late stages of processing. The results are also seen in relation to ear differences in dichotic listening.

Adult↗

PubMed1989

Evoked potential and other CNS reactions during a heliox dive to 360 msw.

Six divers were compressed to 360 msw on heliox. Visual and cognitive evoked responses were performed repeatedly predive, during the dive, and postdive. The evoked response changes were compared with other neuropsychological and neurophysiological results from the dive. The individual diver analysis revealed normal visual evoked responses (P100) for 5 out of 6 divers. The diver with significant increase in P100-latency had more marked HPNS than the others. On the cognitive evoked responses, the P300-waves were not obtainable at the deepest depths (for 4 out of 6 divers) even if the shorter wave forms were normal. The P300-wave was obtainable at 354 msw and 215 msw for 4 divers, and 3 of them had increase in the P300-latency compared with their predive average. There was a significant correlation between P100 change and the sign-index on the other CNS-tests. In conclusion, valid results on the visual and cognitive evoked responses were obtained at pressure. Mild symptoms and signs of HPNS led to normal visual evoked responses, while more marked effects gave significant increases in the visual evoked latency. The more major changes in cognitive evoked responses at pressure, even on minor HPNS-affected divers, indicated that higher cortical functions are affected at high pressures (greater than 300 msw).

Acoustic Stimulation↗

PubMed1987

Psychophysiologic response patterns in migraine before and after temperature biofeedback. Prediction of treatment outcome.

Psychophysiologic response patterns were studied in female migraine patients during headache-free periods (n = 16) and in controls (n = 8). Cardiovascular variables studied were heart rate (HR) and temporal artery pulse wave amplitudes (PWA). Phasic responses to 80-dB, 1000-Hz tones, each lasting 2 sec and sounded at irregular intervals, were studied within a habituation laboratory design. In addition, electromyographic (EMG) levels from the frontal muscles and hand temperature were measured. HR responses were less pronounced and PWA reduction more pronounced in migraine patients than in controls. There were no differences between migraine patients and controls in habituation pattern. Migraine patients showed lower hand temperature and higher EMG levels than controls. Migraine patients were treated with eight temperature biofeedback sessions and were evaluated clinically and psychophysiologically during and 2 months after treatment. Clinical follow-up evaluation was done 2 years after treatment. An average reduction in headache frequency of 66% was reported. A relationship between HR and PWA response pattern before treatment and treatment outcome was found. Migraine patient reporting most pronounced clinical improvement showed a "normalization" of the PWA response pattern after treatment.

Adult↗

PubMed1985

CNS reactions at 51 ATA on trimix and heliox and during decompression.

Two groups of divers (Group A and B) were compressed to 500 msw with trimix (n = 3) and heliox (n = 3). After 4 d at saturation depth Group A had a gas change to heliox. Both groups were followed with repeated neuropsychological and neurological tests during compression, at stable intermediate depths and at saturation depth. There were marked high pressure nervous syndrome effects during compression for both groups. Only tremor was inhibited by the nitrogen. In addition Group A was impaired due to nitrogen narcosis. During trimix and heliox saturation there was only some recovery in the EEG. Group B had a sustained high tremor during the saturation. On visuomotor and cognitive functions Group B performed up to predive level on the 3rd d at saturation while Group A was heavily impaired during the whole trimix saturation period. Although dizziness and tremor were the main symptoms in Group B, Group A reported concentration trouble, euphoria, and upset stomach during the saturation phase. Minor changes occurred in the EEG during the gas change. There was, however, a marked increase in postural tremor and recovery on cognitive tests relating to the elimination of the nitrogen. Up to the completion of the gas change no severe symptoms were reported. Six hours after the gas change, severe symptoms occurred with visual and auditory hallucinations and myoclonic jerks as the dominant characteristics. Some symptoms lasted for 12 h. During decompression there was a steady normalization in both groups.

Adult↗

PubMed1983

Central nervous system reactions during heliox and trimix dives to 51 ATA, DEEP EX 81.

UNLABELLED: Two groups of divers were compressed to 500 msw with heliox (n = 3) and trimix (n = 3). They were followed with repeated neuropsychological and neurological tests during compression, at stable intermediate depths, and at 500 msw. For the heliox group there was a marked increase in tremor and EEG slow waves and reduction in handgrip strength. For the trimix group the tremor increase did not occur, but the EEG changes were the same as in the heliox group. On motor tests only the trimix group showed impaired finger dexterity and manual dexterity. The same occurred for fine visuomotor coordination, but both groups had increased intentional tremor. On cognitive tests the same difference occurred. The trimix group was markedly impaired in reasoning and long-term memory, while only a mild impairment was found in the heliox group. Dizziness and other symptoms of high pressure nervous syndrome (HPNS) occurred in both groups. CONCLUSION: There were marked HPNS effects during compression for both groups. Only tremor was inhibited by the nitrogen. In addition, the trimix group was impaired because of nitrogen narcosis. These data indicated that 10% nitrogen did not inhibit HPNS effects during compression to 500 msw, but the considerable differences between subjects shows that susceptibility to compression must be an important area for future research.

Adult↗

PubMed1982

Psychophysiological response patterns in migraine patients.

Cardiovascular responses to strong auditory stimulation were compared in common migraine patients and controls. Two matched groups of eight subjects participated in two laboratory sessions. During each session, baseline recording of the cardiovascular variables was followed by twenty auditory stimuli (95 dB, 1000 Hz), sounded at irregular intervals. Phasic responses in heart rate and pulse wave amplitudes in the superficial temporal arteries were measured. A post stimulation sampling period ended each session. Different cardiovascular response patterns were found in the two groups. The migraine patients showed more pronounced heart rate responses and slower habituation to stimulation. Stronger pulse wave amplitude reduction during stimulation and an increase during the post stimulation period was also found in the migraine group.

Acoustic Stimulation↗

PubMed1982

Central nervous system reactions during heliox and trimix dives to 31 ATA.

UNLABELLED: Two groups of divers were compressed to 300 msw (984 fsw) with heliox (n = 3) and trimix (n = 3). Neuropsychological/neurological testing was performed repeatedly during the compression and on reaching 250 (820 fsw) and 300 msw. On the second day the trimix group was tested before and after a gas change to heliox. For the heliox group there was a marked increase in tremor and EEG slow waves, and reduction of alpha band and in hand-grip strength. For the trimix group visuomotor coordination was impaired. In the cognitive performance tests the heliox group was most impaired at 250 msw, whereas the trimix group was most impaired at 300 msw. Before the gas change to heliox the trimix group showed impaired performance in some tests. After the gas change, performance returned to predive levels, except for perceptual speed. There was an increase in tremor immediately after the gas change. CONCLUSION: There was a marked HPNS effect during compression on heliox. This effect was not observed in the trimix group, but this group was mildly intoxicated on reaching saturation depth. The tests indicated slight narcotic effects also after 26 h, but this disappeared after the change in heliox.

Adult↗