Biomedical subjects

K Hugdahl

Publications and source records attributed to K Hugdahl.

At least 73 records · Page 4Linked to original sources

PubMed1994

Verbal and non-verbal function of children with right- versus left-hemiplegic cerebral palsy of pre- and perinatal origin.

Eighteen children with right- and 13 with left-sided congenital hemiplegia were compared with 19 normal age-matched controls for verbal and non-verbal function. CT scans were obtained from 27 of the 31 hemiplegic children. The two hemiplegic groups were impaired in non-verbal function compared with controls. The right-hemiplegic group was more impaired in verbal function than the left-hemiplegic group and controls; however, impairments were restricted to the girls in the right-hemiplegic group. The results are discussed in terms of cerebral plasticity and functional reorganisation of cognitive functions after an early unilateral injury. It is argued that girls with left-hemisphere lesions may be more limited in cerebral plasticity than boys.

Adolescent↗

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↗

PubMed1994

Dichotic listening during auditory hallucinations in patients with schizophrenia.

OBJECTIVE: Auditory hallucinations are a serious problem for a large subgroup of psychotic patients who do not respond optimally to neuroleptic medication. It has been hypothesized that hearing imaginary voices involves the same physiological processes as those involved in hearing real voices, but this hypothesis has not been conclusively confirmed. METHOD: In this study a consonant-vowel version of the Dichotic Listening Test was used to assess the functional integration of the left hemisphere in hallucinating and nonhallucinating psychotic patients. The test was administered under three conditions: a nonforced attention condition, a condition in which attention was forced to the left ear, and one in which attention was forced to the right ear. RESULTS: The nonhallucinating patients showed the normal right ear advantage, which indicates a left hemisphere superiority in the processing of linguistic stimuli. In contrast, the hallucinating patients showed no ear advantage. Neither group was able to modify its performance when instructed to attend to either the left or the right ear. A subgroup of patients was tested in both hallucinating and nonhallucinating states, but the ear asymmetry was not noticeably different between these states. CONCLUSIONS: The results suggest that auditory hallucinations are associated with abnormalities in left hemisphere functioning and that these abnormalities might not be limited to the time of the auditory hallucinations. It is hypothesized that a relatively enduring left hemisphere abnormality may leave some patients at risk for auditory hallucinations.

Adult↗

PubMed1993

Routine ultrasonography in utero and subsequent handedness and neurological development.

OBJECTIVE: To examine any associations between routine ultrasonography in utero and subsequent brain development as indicated by non-right handedness at primary school age and neurological development during childhood. DESIGN: Follow up of 8 and 9 year old children of women who took part in two randomised, controlled trials of routine ultrasonography during pregnancy. SETTING: Clinics of 60 general practitioners in Norway during 1979-81. Maternal and child health centres. SUBJECTS: 2161 (89%) of 2428 eligible singletons were followed up, partly through a questionnaire to their parents and partly through information from health centres. MAIN OUTCOME MEASURES: The dominant hand of the child was assessed by 10 questions. Deficits in attention, motor control, and perception were evaluated by five questions. Impaired neurological development during the first year of life was assessed by an abbreviated version of the Denver developmental screening test. RESULTS: The odds of non-right handedness were higher among children who had been screened in utero than among control children (odds ratio 1.32; 95% confidence interval 1.02 to 1.71). No clear differences were found between the groups with regard to deficits in attention, motor control, and perception or neurological development during the first year of life. CONCLUSION: Our data suggest a possible association between routine ultrasonography in utero and subsequent non-right handedness, whereas no association with impaired neurological development was found. As the question on non-right handedness was one of six initial hypotheses, the observed results may be due to chance. None the less, the results suggest that the hypothesis may have some merit and should be tested in future studies.

Child↗

PubMed1993

Left-handedness and old age: do left-handers die earlier?

Data are presented on the prevalence of current left-handedness and prior left-handedness (switched) in 2787 subjects from 21 to 101 years of age. In addition, data on sex differences, familial sinistrality, hand posture when writing, and education were recorded. Two hypotheses were tested. The elimination hypothesis states that reduced frequency of left-handers in old age is due to reduced longevity. The modification hypothesis states that differences in the number of left-handers between older and younger persons are due to changing patterns of social norms. The results showed a decreasing prevalence of left-handedness across the age span, with 15.22% in the youngest group (21-30 years), but only 1.67% in subjects older than 80 years. There was however a corresponding increase in the number of subjects who had switched hand for writing, 2.69% in the youngest group to 6.75% in subjects 80 years and above. This supports the modification hypothesis and questions the elimination hypothesis. However, the mean percent score was still lower in subjects above compared to below age 40 after correction for hand switching. Thus, although changes in social norms towards left-handers seem to be the most likely explanation, we have not empirically disproved the elimination hypothesis.

Adult↗

PubMed1993

Effects of lateralized US and CS presentations on conditioned head turning and bilateral cingulate cortex responses in cats.

A lateralized tone conditioned stimulus (CS+) paired with a rewarding medial forebrain bundle (MFB) stimulation unconditioned stimulus (US) was presented to one ear of the cat, while the same tone was presented to the other ear alone (CS-). Specifically, the electrical stimulation of the MFB elicited a contralateral head turn as the unconditioned response (UR). Correspondingly, the CS+ was given to an ear contralateral to the direction of the UR. During the CS test session the cats oriented toward the tones, but these head movements habituated rapidly. During conditioning the cats developed stereotypical extended vigorous head turns to the CS+, with significantly greater acceleration and shorter onset latencies to the CS+ than to the CS-. Head turns in response to the CS+ were always ipsilateral to the tone, but responses to the CS- were in some cats ipsilateral and in most cats contralateral to the tone. Recordings of the slow potential responses showed a broad negative deflection in the cingulate cortex, with peaks at 140 and 250 ms. The amplitude of this negative potential to the CS+ was larger than that to the CS-, but no asymmetries were found between the hemispheres. The present behavioral paradigm is potentially useful for studying the neural basis of conditioned approach responses.

Acoustic Stimulation↗

PubMed1993

Laterality for facial expressions: does the sex of the subject interact with the sex of the stimulus face?

Seventy right-handed subjects (35 males and 35 females) were shown lateralized pictures of negative, neutral, and positive facial emotional expressions. For each emotional category, half of the pictures were of a male face showing the emotion, half were of a female face. The pictures were shown in the left visual half-field for half of the trials and in the right half-field for the other half of the trials. The question addressed was whether the sex of the stimulus face interacts with the sex of the subject for hemisphere differences in perception of facial emotions. Response accuracy and reaction time were measured. The pictures were shown from a slide projector with a high-speed shutter mounted to the lens to allow for tachistoscopic presentations. The results showed that the right hemisphere was more accurate and faster than the left in recognizing the stimulus faces, and that positive emotions were overall more easily recognized. The lack of a significant interaction between sex of the stimulus and sex of the subject indicates that these two factors are not interrelated or confounded in laterality research.

Adolescent↗

PubMed1993

Bilaterally recorded multiple-unit activity of the cingulate cortex during head turning conditioning with unilateral medial forebrain bundle stimulation.

Cats were conditioned to turn their heads using a tone conditioned stimulus (CS) and medial forebrain bundle stimulation (MFB) unconditioned stimulus (US). The CS+ was delivered to one ear at a time, in random order, followed by the US. A tone of a different frequency was used as a CS-. The cats learned to respond differentially to the CSs showing head movements of greater acceleration to the CS+ than CS- over sessions. Bilateral recordings of cingulate cortex multiple-unit activity showed increased response amplitudes over sessions and larger responses in the hemisphere ipsilateral to the US. Since ipsilateral multiple-unit responses did not differ for the CSs, the asymmetry was probably due to the sensitizing effect of the unilateral US. Although increases in cingulate cortex neural activity coincided with increases in conditioned head movements, larger activation of the cingulate cortex ipsilateral to the US suggests that the neural changes were independent of these movements.

Animals↗

PubMed1993

Right hemisphere representation of autonomic conditioning to facial emotional expressions.

In this experiment, a lateralized right hemisphere effect was found for electrodermal associative learning to facial emotional expressions. Sixty-two subjects were presented simultaneously with a slide of a happy face in the right or left visual half field (VHF) and a slide of an angry face in the opposite VHF. Four groups were formed by the combination of the two VHF positions of angry/happy faces and the administration/omission of shock unconditioned stimuli. The results showed that simultaneous presentation of the angry face to the right hemisphere and the happy face to the left hemisphere, together with shock, resulted in a strong conditioned association with the angry face and a relatively weak association with the happy face. Furthermore, simultaneous presentation of the angry face to the left hemisphere and the happy face to the right hemisphere, together with shock, resulted in a relatively weak association with both stimuli. No significant differences were found for the no-shock control groups. The present results confirm previous findings of a right hemisphere advantage for representation of associative learning.

Adolescent↗

PubMed1992

Pathological left-handedness revisited: dichotic listening in children with left vs right congenital hemiplegia.

Thirty-one children with right (n = 18) and left (n = 13) congenital hemiplegia were compared for incidence of hand- and foot-preference, eye-dominance, and familial sinistrality. In addition, they were tested with dichotic listening for correct reports of consonant-vowel syllables. The two groups of children were closely matched on IQ and sensory functioning. Children with mental retardation, or epileptic seizures were not included. The results showed that 89% of the left hemisphere impaired (LHI) children were left-handed, all of them preferred the left foot, and 72% were left eye-dominant. In the right hemisphere impaired (RHI) group, everyone (100%) preferred the right hand and foot, and 62% were right eye dominant. The dichotic listening results showed a significant right ear advantage (REA) in the RHI-group, and a significant left ear advantage (LEA) in the LHI-group. The results are discussed in the framework of pathological handedness and shifts in hemisphere control of language in children with early brain injury. It is argued that the homogeneous samples, except for the site of lesion, provides an interesting possibility to compare cognitive effects of left and right hemisphere impairment in children.

Adolescent↗

PubMed1992

Dichotic listening performance in subtypes of developmental dyslexia and a left temporal lobe brain tumor contrast group.

This study examined dichotic listening performance in three subtypes of developmental dyslexia and in children with left temporal lobe brain tumors (clinical contrast group). Each child was administered a free-recall CV syllable dichotic paradigm (30 pairs). Analysis of variance and Tukey-HSD pairwise follow-up comparison indicated that the dichotic listening performance of the left temporal lobe brain tumor contrast group (strong LEA/right ear suppression) was significantly different from those of the visual-spatial/dyseidetic (strong REA/left ear depression) and mixed (moderate REA/bilateral ear suppression) dyslexic subtypes. The language disorder/dysphonetic dyslexic subtype demonstrated a REA with right ear depression. Closer inspection of the individual performances of the language disorder/dysphonetic dyslexic subtype revealed a bimodal distribution with 12 subjects demonstrating a strong LEA/right ear suppression and 8 subjects exhibiting a strong REA/left ear depression. These results lend support for the contention that the dyslexic population is heterogeneous in nature with each subgroup exhibiting (1) a distinct neuropsychological test profile and reading pattern and (2) a pattern of performance on the dichotic listening task which is consistent with what would be expected based upon the pattern of dysfunction exhibited on neuropsychological evaluation.

Adolescent↗

PubMed1992

Manipulations of subjects' level of arousal in dichotic listening.

The effects of manipulation of the subject's level of arousal on the right ear advantage (REA) in dichotic listening to CV-syllables were investigated. There were three different arousal manipulations under high and low incentive levels. Negative manipulations involved threat of electric shock (high incentive) or noise (low incentive) for incorrect answers. Positive manipulations involved the possibility to earn a substantial (high incentive) or small (low incentive) sum of money for correct answers. A third, neutral, condition involved no specific instructions about consequences for correct or incorrect answers. Thirty-six females participated in the study. Heart rate was recorded as an independent measure of change in level of arousal as a function of the experimental instructions. The results showed that the high negative condition abolished the REA effect, with a non-significant difference between ears. This was caused by both an increase in correct left ear reports and a decrease in correct right ear reports. The other arousal conditions had no effect on the REA. The results are discussed in terms of right hemisphere dominance for aversive emotional processing in dichotic listening.

Acoustic Stimulation↗

PubMed1992

Hemispheric asymmetry effects in children studied by dichotic listening and visual half-field testing.

Dichotic listening (DL) and visual half-field (VHF) testing were used to study hemisphere asymmetry in a developmental perspective. Five-, 8-, and 11-year-old children were presented lists of fused words using a DL technique in Experiment 1, and 8- and 11-year-old children were presented pictures of common objects using a VHF technique in Experiment 2. In both experiments, measures of identification, free recall, and recognition of the words/pictures were employed. The results revealed effects of ear input (right-ear advantage) and half-field presentation (right visual half-field advantage) for all age groups, although the magnitude of this lateralization effect differed between the three memory measures. The results are discussed in relation to developmental aspects of language laterality, and in relation to the clinical utility of non-invasive lateralization techniques.

Child↗

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↗

PubMed1992

Dichotic listening studies of hemispheric asymmetry in brain damaged patients.

In the present paper we review the empirical evidence for structural versus attentional explanations of the right ear advantage (REA) phenomenon in dichotic listening (DL). The ear advantage in DL is a behavioral "marker" of language function in the cerebral hemispheres. Dichotic listening data from four brain-lesioned patients are presented. The patients had a tumor or cyst in the left Sylvian region (2 cases); hemorrhage in the left frontotemporal region (1 case); and severe destruction of the left hemisphere (1 case). The results from all four patients showed marked reductions in correct recall of the right ear items, while left ear recall was left unaffected. In two of the cases, the DL data showed an immediate reinstatement of the REA after neurosurgery. It is concluded that the results favor a structural/anatomical explanation of the ear advantage phenomenon in DL, rather than an attentional bias explanation.

Adult↗

PubMed1991

Auditory neglect after right frontal lobe and right pulvinar thalamic lesions.

Auditory unilateral neglect or extinction to simultaneous stimulation is reported in a right-handed male with a lesion in the right frontal lobe and in the right thalamic pulvinar area. The patient was submitted to stereotactic thalamotomy for a post-traumatic intentional ataxia in the left extremities. He was subjected to repeated tests with dichotic listening to consonant-vowel syllables under three different attentional instructions. He was also tested monaurally with the same stimulus materials as used in the dichotic test. The results showed almost complete extinction of the left ear input during dichotic presentations, despite normal hearing when tested with audiometer screening. The left ear extinction effect was independent of instructions to attend to the left or right ear input. However, during monaural presentation, correct left ear reports increased to about 85%. The results are interpreted as showing an auditory attentional neglect caused by the right frontal and pulvinar lesions.

Adult↗

PubMed1991

Hemisphere differences in conditional learning: an ERP-study.

The present ERP-experiment investigated brain asymmetry in encoding and representation of the formation of conditional associations in a Pavlovian framework. Two consonant-vowel syllables were used as conditional stimuli, one of them paired with an unconditional noise during the acquisition phase (CS+), the other never paired with noise (CS-). During a subsequent test phase, both CS cues were presented dichotically i.e. at the same time. Half of the subjects had the CS+ probe presented to the right ear (contralateral to the left hemisphere). The other half of the subjects had the CS+ presented to the left ear (contralateral to the right hemisphere). ERPs from F3, Fz and F4 leads were recorded. The paradigm used was an adaptation of the standard dichotic listening technique for the study of learned associations. The results showed that conditional associative learning occurred during the acquisition phase in both "groups". The P235 latency was furthermore delayed over the left hemisphere to the CS+ probe. During the dichotic test phase, there was a clear laterality or asymmetry effect between the groups for both the N125 and N450 components, possibly supporting an interpretation of asymmetry in encoding and cortical representation of a conditional association, although alternative interpretations remain open.

Adult↗

PubMed1991

Anticipatory nausea and vomiting in cancer patients.

The present study reports on a mediating mechanism for anticipatory nausea and vomiting (ANV) in cancer chemotherapy. ANV is usually explained as a classically conditioned response. However, conditioning models have failed to explain individual variation in ANV susceptibility. On the basis of the positive correlation between degree of autonomic reactivity (AR) and conditionability, it is proposed that individual AR is predictive of ANV development. Of the 31 patients who participated in the study, 74% experienced postinfusion nausea and vomiting (PNV). Of the 23 patients who experienced PNV, 52% developed ANV. AR was recorded in a habituation paradigm before chemotherapy treatment was initiated. The patients in the ANV group showed significantly increased sympathetic reactivity as compared with the no-ANV group, implying that AR is a mediator of ANV development.

Adolescent↗