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Biomedical subjects

K Hugdahl

Publications and source records attributed to K Hugdahl.

At least 91 records · Page 5Linked to original sources
PubMed1991

Hemispheric asymmetry in conditioning to facial emotional expressions.

In the present experiment, we report a right hemisphere advantage for autonomic conditioning to facial emotional expressions. Specifically, angry, but not happy, facial expressions showed significantly more resistance to extinction when presented initially to the right as compared to the left hemisphere. Slides of happy and angry faces were used as conditioned stimuli (CS+ and CS-) with shock as the unconditioned stimulus (UCS). Half of the subjects (n = 15) had the angry face as CS+ (and the happy face as CS-), the other half had the happy face as CS+ (and the angry face as CS-). During acquisition, the CSs were presented foveally. During extinction, using the Visual Half-Field (VHF) technique, half of the CS+ and CS- trials were randomly presented in the right visual half-field (initially to the left hemisphere), and half of the trials were presented in the left half-field (initially to the right hemisphere). Stimuli were presented for 210 ms during acquisition, and for 30 ms during extinction. Bilateral skin conductance responses (SCRs) were recorded. The results showed effects of acquisition only for the angry CS+ group. During extinction, there was a significant Conditioning X Half-field interaction which was due to greater SCRs to the CS+ angry face when it was presented in the left half-field. It is concluded that the present results reveal hemisphere asymmetry effects in facial emotional conditioning.

Adult↗
PubMed1991

Dichotic listening during forced-attention in a patient with left hemispherectomy.

A young left-handed girl with an extensive posttraumatic lesion in the left hemisphere was tested with dichotic listening (DL) under three different attentional instructions. The major aim of the study was to evaluate a structural vs attentional explanation for dichotic listening. As both her expressive and receptive language functions were intact after the lesion, it was assumed that the right hemisphere was the language-dominant one. In the free-report condition, she was free to divert attention to and to report from both ear inputs. In the forced-right condition, she was instructed to attend to and report only from the right ear input. In the forced-left condition, she was instructed to attend to and to report only from the left-ear input. Her performance was compared with data from a previously collected sample of normal left-handed females. Analysis showed that the patient, in contrast to the normal sample, revealed a complete right-ear extinction phenomenon, irrespective of attentional instruction. Furthermore, she showed superior correct reports from the left ear, compared with those of the normal sample, also irrespective of attentional instruction. It is concluded that these results support a structural, rather than attentional explanation for the right-ear advantage (REA) typically observed in dichotic listening. The utility of validating the dichotic listening technique on patients with brain lesions is discussed.

Adolescent↗
PubMed1991

Asymmetries in classically conditioned head movements and cingulate cortex slow potentials in cats.

Presuming that conditioned head movements in the cat indicate a preference for a specific direction, asymmetries were also expected to be found in bilaterally recorded cingulate cortex slow potentials to a symmetrical tone stimulus during discriminative conditioning. Conditioned stimuli (CS, 1000 and 2500 Hz tones) were delivered through two miniature loudspeakers fitted to the head in front of both ears. The unconditioned stimulus (US) was an electrical stimulation of either the left or right lateral hypothalamus yielding, in addition to its rewarding effects, an unconditioned head turning response (UR) either to the left, right, forwards or upwards. Discrimination learning appeared as more extended and more rapid headturns and greater negativity in the cingulate cortex to the CS+ than to the CS-. The preferred conditioned behavioral response (CR) was a headturn to the left in 11 of 12 cats accompanying increased negativity in evoked slow potentials in the right cingulate cortex during the 128-324 ms period after the CS onset. No differences in the movements and in the cingulate potentials were found between the left versus right US stimulations. The results showed that regardless of the direction of the original unconditioned head movement, the direction of the CR was at the end of the training period to the left in 11 out of the 12 cats. Larger evoked slow potentials observed in the right cingulate cortex which were not present in the baseline measurements suggest a population bias between the hemispheres.

Animals↗
PubMed1990

Immune and autoimmune diseases in dyslexic children.

One hundred and five dyslexic and 105 control children were compared for frequency of immune diseases, autoimmune diseases, and non-right-handedness in the light of the Geschwind-Behan (1982) "testosterone hypothesis". The results showed significantly more immune- and autoimmune-diseases int he dyslexic group. There were no differences between the groups in the frequency of non-right-handedness. There were no interactions with gender, although there were more non-right-handed boys than girls in the total sample. Mothers of children who were dyslexic experienced significantly more negative life-events during pregnancy, they also experienced the pregnancy as more difficult, and they had more spontaneous abortions. In conclusion, the results support some aspects of the "testosterone hypothesis", but they also point to a more complex pattern of interaction between the factors that still remain unanswered.

Adolescent↗
PubMed1990

The role of the left and right thalamus in language asymmetry: dichotic listening in Parkinson patients undergoing stereotactic thalamotomy.

Fourteen patients with Parkinson's disease (rigidity and unilateral tremor as main symptoms) were treated with stereotactic thalamotomy. The operation was performed in either the left or right ventrolateral thalamus, depending on which hand (or foot) was most affected with tremor. Nine patients were operated on the left side and four on the right side. All patients were tested for asymmetry of language functioning with dichotic presentations of consonant-vowel (CV) syllables. The patients had to indicate which of the two syllables he/she heard on each trial. Dichotic listening was performed before and after the operation, as well as during electrical stimulation of the VL nucleus just before the lesion was carried out. The results revealed essentially three things: an overall reduced right ear advantage (REA) in the patient group compared to what is known from studies of healthy individuals; an increase in REA during left-sided stimulations; and a marked reduction in REA after left-sided lesions. It is concluded that the present data support the notion put forward by Ojemann (e.g., 1975) of a lateralized activating gating mechanism in the left VL nucleus that gates access for language information to the appropriate cortical areas. The gating mechanism seems to be activated by stimulation, and deactivated after lesions. Dichotic listening may thus be a heuristic instrument in assessment of language functions in Parkinson patients.

Adult↗
PubMed1990

The effects of head and eye turns on the right ear advantage in dichotic listening.

The aim of the present experiment was to investigate the effects of head and eye turns on the ear advantage in dichotic listening (DL) to CV-syllables. Since head and eye turns also mean focusing attention to either the left or right side in space, a second aim was to evaluate recent arguments that ear advantages seen in DL are caused by the perceived position in space of the sound source. Forty right-handed females had 36 trials of CV-syllables under four different instructions. One group (n = 20) was instructed to turn their head (but not their eyes) to the right, the left, or straight ahead during stimulus presentations. The fourth condition was a standard (no instruction) condition. A second group (n = 20) had the same instructions but were told to turn their eyes instead of their heads. Conditions were pseudo-counterbalanced across subjects. Consistent with other studies, results showed a right ear advantage (REA) in both groups during all conditions. However, the REA was largest for the standard condition. Also, more subjects showed a REA during the standard condition, and especially compared to the turn-right condition. It is concluded that dichotic performance is not caused by selective attention to either side in space, and that lateral turns of the head and the eyes contralateral to the left hemisphere have an inhibitory (if anything) effect on the REA.

Adult↗
PubMed1990

Effects of habituation and classical conditioning on reflex modification.

Reflex modification is the inhibition or facilitation of a reflex by a stimulus (S1) occurring prior to a reflex-eliciting stimulus (S2). Two experiments were conducted that investigated the effects of habituation of the orienting response (OR) and classical conditioning on reflex modification of skin conductance responses (SCRs). During the first phase of Expt. 1 two groups (Group S1 and the Control group) received pre-presentations of S1 (200 Hz). Another group (Group S3) received pre-presentations of a different tone (S3, 3000 Hz). During the second phase, Groups S1 and S3 received pairings of S1 with S2 (white noise), whereas the Control group received pairings of S2 with S1. The predictions were: if the OR to S1 produces reflex modification of the response to S2, then Group S1 and the Control group will display larger SCRs on the first trial of the second phase of the experiment compared to Group S3, in which the OR to S1 will produce reflex modification. However, if conditioned diminution of the unconditioned response (UR) elicited by S1 produces reflex modification of the response to S2, then there should be no initial differences between the groups in the second phase of the experiment. The results showed that SCRs in Group S1 were significantly larger in the second phase compared to Group S3. This result favors an OR explanation of reflex modification. In Expt. 2, the effect of conditioned diminution of the UR on reflex modification was further investigated.(ABSTRACT TRUNCATED AT 250 WORDS)

Acoustic Stimulation↗
PubMed1990

Reflex modification in the electrodermal system: conceptual and methodological issues.

Reflex modification (RM) is the inhibition or facilitation of a reflex response by a stimulus (S1) occurring prior to a reflex-eliciting stimulus (S2). The present experiment investigated two issues: (1) whether RM may be confounded by orienting generated by changes in the experimental procedure, or habituation generated by repeated stimulus presentations; (2) whether the strength of RM is influenced by repeated pairing of S1 and S2, that is, classical conditioning. Two groups of subjects were given two series of stimulus presentations. Group A received first 10 S2-alone presentations, before 10 S1-S2 presentations. Group B received the stimuli in reversed order, that is, first 10 S1-S2 presentations, and then 10 S2-alone presentations. This design permits a comparison of unconfounded with confounded RM, as well as assessment of influences of learning. The results showed RM to be influenced by orienting caused by changes in the experimental procedure. The strength of RM tended to be gradually reduced as a function of the number of S1-S2 pairing, indicating that the orienting response to S1 habituated across trials. It is concluded that RM may be useful in the objective investigation of more complex cognitive processes.

Adult↗
PubMed1990

Dichotic listening, forced attention, and brain asymmetry in righthanded and lefthanded children.

Righthanded and lefthanded 7-year-old children (both boys and girls) were compared for dichotic listening performance under free report and forced attention conditions. Previous findings from our laboratory have shown that, while adults reverse the right ear advantage (REA) during the forced-left condition, children do not. Since the finding in children was unexpected, the first aim of the present study was to replicate our previous results. A second aim was to include lefthanded children with the hypothesis that they should more easily revert to a LEA, because of less homogeneous lateralization. The results essentially replicated our previous findings, during all three recall conditions. No sex differences were observed, and both handedness groups showed the same overall response pattern.

Attention↗
PubMed1990

Fear questionnaires for simple phobias: psychometric evaluations of a Norwegian sample.

The present study presents psychometric data for four different phobic fear questionnaires in a Norwegian sample of 284 subjects. The questionnaires concerned fear of flying, snakes, spiders and a questionnaire of general phobic complaints. The results showed a high estimate of internal consistency, and a very high test-retest reliability for all questionnaires. A low to moderate degree of intercorrelation between the questionnaires appeared. A clear sex difference emerged in responding to all four questionnaires. In addition, a clinical sample of phobics with fear of flying as the main symptom was compared to the larger sample on a fear of flying scale. The results showed a clear difference in responding between the samples. The present study concludes that the four different fear questionnaires yielded a high degree of reliability, and their use in clinical practice is encouraged.

Adult↗
PubMed1990

Dichotic listening in an aphasic male patient after a subcortical hemorrhage in the left fronto-parietal region.

Dichotic listening (DL) performance to consonant-vowel (CV) syllables is reported in an aphasic right-handed male patient. The patient suffered initially from a complete expressive aphasia after an intracerebral hemorrhage caused by the rupture of an arteriovenous malformation (AVM) underlying Broca's area. The patient was tested three times with DL; one week after the hemorrhage, five weeks after, and after at about 6 months. At the first test he could not speak, but understood well. At the second test he uttered one-syllable words, and could answer "yes" and "no" to questions. At the third test he could speak whole sentences, although slow and "stutter-like." Dichotic listening performance showed an almost perfect match with speech recovery. At the first test he showed a left ear advantage which changed to no ear advantage at the second test, and to a right ear advantage at the third test. The overall performance was markedly reduced at the first test, but improved at the following test. It is concluded that dichotic listening may be a valid complement to traditional language assessment procedures after unilateral brain lesions.

Adult↗
PubMed1989

Preparedness and electrodermal fear-conditioning: ontogenetic vs phylogenetic explanations.

In a review of existing theories of learning, Seligman (Psychol. Rev. 77, 406-418, 1970) suggested that humans should have an evolutionary derived preparedness to associate fear-relevant (e.g. snakes) events with aversive reinforcers. The preparedness hypothesis has been extensively tested by Ohman and his colleagues. One argument against a non-preparedness explanation for the Ohman findings has been that culturally aversive stimuli, like pictures of guns have not shown the same resistance towards extinction as pictures of snakes. However, the effect of pointing a gun directly towards the S vs pointing it to the side has not been tested. Therefore both slides of guns and snakes, directed both towards and aside from the subject, were used as conditioned stimuli (CSs) in the present study. A second question that has been discussed in the preparedness-literature is the quality of the unconditioned stimulus (UCS), i.e. if only shock can act as UCS for prepared CSs. Thus, both shock and noise UCSs were used in the present study. Skin conductance responses (SCRs) were recorded as dependent measures. The results showed conditioned acquisition, i.e. larger SCRs to CS+ than to CS-, in all groups except for the shock and noise UCS groups with the gun pointing aside as CS+ (where actually larger responses were observed to the CS-, i.e. the gun pointing towards). The extinction data showed significantly larger SCRs to CS+ than to CS- for both snakes and guns directed towards the S. Strongest resistance to extinction was observed for the group with the gun pointed towards as CS+ and with noise as UCS. The gun with noise as UCS pointed towards the S was not different from the snake with shock as UCS. Taken together, the results have shown three things; (a) directing a fear-relevant CS towards the S was a potent manipulation, and especially directing a gun with noise as UCS; (b) shock was overall not superior to noise as UCS, and especially not for snake CSs; (c) a weak form of unique belongingness was demonstrated.

Adult↗
PubMed1989

Dichotic listening in 126 left-handed children: ear advantages, familial sinistrality and sex differences.

In the present study we report data on dichotic listening (DL) performance in 126 left-handed children. Four specific questions were addressed: (1) What is the percentage of left-handers in a large sample of children in Sweden? (2) What is the distribution of children showing a right ear (REA), left ear (LEA), and no ear (NEA) advantage in DL? (3) What is the relationship between ear advantage and familial sinistrality in children? (4) Are there sex differences among left-handed children, and if so, are these differences also reflected in DL performance? The results showed that the left-handers constituted 8.1% of the total sample of the screened subjects. The DL results showed 65.0% REA, 25.4% LEA, and 9.6% NEA. Of the subjects, 45.2% had left-handed relatives. Overall, there were more boys than girls in the sample (65.1% vs 34.9%). It is concluded that the present data match the sodium-Amytal data on left-handed adults with about 2/3 of a left-handed population with left hemisphere language dominance.

Child↗
PubMed1989

Left and right-handed dyslexic boys: an empirical test of some assumptions of the Geschwind-Behan hypothesis.

Twenty-six dyslexic boys (13 left-handers and 13 right-handers) were tested for hemispheric asymmetry with dichotic listening (DL) and a visual half-field test (VHF). The purpose of the study was an empirical test of the Geschwind-Behan [Proc. natn. Acad. Sci. USA 79, 5097-5100, 1982] hypothesis of a difference in hemispheric asymmetry between left- and right-handed dyslexic boys. Following Geschwind and Behan, left-handedness and dyslexia are caused by a common factor affecting the development of the left hemisphere in utero which results in a right hemisphere dominance. As a consequence, handedness but not language is shifted to the right hemisphere. We therefore predicted that left-handed dyslexics should be superior to right-handed dyslexics on visuospatial tasks, but perform similar to right-handers on verbal tasks. The results revealed a significant right ear advantage (REA) in both groups during a dichotic listening test to verbal stimuli. The left-handed group was however superior to the right-handed group in recognition of visuo-spatial stimuli presented in the left half-field in a visual half-field test. It is concluded that the results provide some, although weak, support for the Geschwind-Behan hypothesis.

Adolescent↗
PubMed1989

An IBM-PC and Commodore 64 microcomputer-based system for elicitation and recording of eyeblink reflexes.

The eyeblink reflex is well suited for the study of habituation, sensitization, reflex modification and classical conditioning in humans. A microcomputer-based system for elicitation and recording of the eyeblink reflex is described. The system consists of three functional units: (1) an air-pressure bottle and pressure-reducing valves for delivery of air puffs to the eye in order to elicit the eyeblink reflex, and a CBM 64 computer for presentations of auditory stimuli in conjunction with air puffs; (2) a pair of light-emitting diodes and photocells placed in a pair of goggles placed on the subject for detection of eyeblinks; (3) an IBM-compatible personal computer, equipped with the ASYSTANT + software for eyeblink data acquisition and overall control of experiment and parameters. The system is presently in use in our laboratory, and technical details about the system can be obtained by writing to the first author.

Acoustic Stimulation↗
PubMed1989

Dichotic listening in children with serious language problems.

20 children with serious language problems (mainly expressive) were tested with the Dichotic Listening (DL) test for language laterality. 16 were right-handed and 4 left-handed. The dichotic test consisted of series of pairwise presentations of CVC-syllables with "target-syllables" that should be detected interspersed among "distractors." The child pointed to a sheet of paper on which a picture representing the targets (and distractors) was printed. In addition, the children were tested on several expressive and impressive language tests and on finger-tapping. Analysis showed an increased frequency of subjects with a left-ear advantage (LEA) and a reduced amplitude of the right-ear advantage (REA) for those subjects showing a right-ear advantage. Correlations with the language variables and with finger-tapping are presented and discussed.

Attention↗
PubMed1989

Visual half-field tests of lateralized letter presentations: differences between preliterate and literate children.

In the present study, hemispheric differences in global and analytic processing were investigated in preliterate and literate children, using the "dual-letter" matching task paradigm (Navon, 1977). The stimuli consisted of lateralized visual presentations of large uppercase letters made up of small uppercase letters. The task of the subject was to decide on each trial if the large or small letters were the same or not. Vocal reaction time (VRT) and error-frequency were used as dependent measures. In Experiment 1, 28 right-handed 8-years old children participated. The children were split into a preliterate and a literate group depending on teachers evaluations, and on scores on a reading test. The results showed longer VRTs for the preliterate children when the stimuli were initially presented to the right hemisphere and especially when the subjects were required to match the small letters. These results were followed up in Experiment 2, where the preliterate subjects were split into "fast" and "slow" readers. The results showed that the "slow" readers were more impaired in processing the letter stimuli when the stimuli were initially presented to the right hemisphere. It is concluded that hemispheric asymmetry for letter processing interacts with the development of normal reading ability in children.

Child↗