Biomedical subjects

K Hugdahl

Publications and source records attributed to K Hugdahl.

At least 37 records · Page 2Linked to original sources

PubMed1999

[Intracranial arachnoidal cysts--localization, gender and sidedness].

The aim of the present study was to investigate whether data on location and distribution of intracranial cysts in a large patient population may explain why and how such cysts are formed. We investigated 123 patients with 129 intracranial cysts, consecutively admitted to the Department of Neurosurgery in Bergen 1988-97. Data were analyzed with regard to intracranial location and gender distribution. Cysts were much more commonly located in the temporal fossae than one would expect if the distribution were random; 68.1% of patients had temporal cysts. We suggest a theory that may explain how mal-development of the leptomeninges may contribute to the formation of cysts, and why such cysts are more common in the temporal fossae. Temporal cysts were significantly more frequent in males than in females (3.9:1), while cysts of other locations did not show preponderance for a specific gender. New in this study is the interesting connection between gender distribution and sidedness: the significant predominance of left-sided temporal cysts was found only in males. In patients with a unilateral temporal cyst, the left/right ratio was 2.0:1 (males 44 left and 20 right, females eight left and six right). We discuss whether the preponderance of left-sided temporal cysts in males can be explained by a gender specific developmental failure, as previously suggested for dyslexia.

Adolescent↗

PubMed1999

[Intracranial arachnoidal cysts--some neuropsychological experiences].

Arachnoid cysts may cause neurological symptoms. The aim of this study was to investigate whether they also affect cognition. 31 patients (26 males and five females) underwent decompressive surgery for a symptomatic cyst in the left temporal fossa, with craniotomy and fenestration or with a cystosubdural shunt. The patients were tested for asymmetries in verbal perception and verbal memory before and after surgery, using dichotic listening techniques with different auditory stimuli presented simultaneously to the two ears. In the preoperative perception (dichotic listening-DL) test, the patients failed to show the normal advantage for auditory input to the right ear. After decompression, their DL performance normalised, as they now had a right ear advantage. In the preoperative dichotic memory test, the patients differed significantly from a normal reference group in two respects: they remembered fewer words, and they exhibited a clear left ear advantage, in contrast to the normal right ear advantage seen in the reference group. Postoperatively, overall memory performance was enhanced, and the preoperative superiority of the left ear had changed to a normal right ear advantage. The results indicate that arachnoid cysts in the left temporal fossa impair cognition, that neuropsychological tests are required to disclose such impairments, and that decompressive surgery improves cognition.

Adolescent↗

PubMed1999

Hemispheric asymmetry in schizophrenia: a "dual deficits" model.

BACKGROUND: The aim was 1) to investigate left hemisphere functional integrity for auditory language processing in schizophrenic patients; and 2) to investigate the interaction between brain laterality and attentional processing by having subjects shift attention to the left or right ear. METHODS: The subjects were 33 schizophrenic inpatients, and 33 healthy comparison subjects with the same age, handedness, and gender distribution as the patient subjects. All subjects were tested with dichotic listening (DL) to consonant-vowel syllables, which is a measure of lateralized temporal lobe language processing. The subjects were tested under three different attentional conditions: a non-forced attention condition, attention focused to the right ear stimulus, and attention focused to the left ear stimulus. RESULTS: The main findings were 1) an absence of the expected right ear advantage in the schizophrenic group during the non-forced attention condition; and 2) a failure to modify DL performance through shifting of attention to either the right or left ear. The comparison group showed a right ear advantage during the non-forced and forced-right attention conditions (increased right ear advantage during the forced-right condition), and a left ear advantage during the forced-left attention condition. There were no significant effects of handedness. CONCLUSIONS: This pattern of results may indicate a "dual deficit" involving both automatic and controlled processing deficits in schizophrenia.

Adult↗

PubMed1999

Brain activation during dichotic presentations of consonant-vowel and musical instrument stimuli: a 15O-PET study.

Dichotic listening means that two different stimuli are presented at the same time, one in each ear. This technique is frequently used in experimental and clinical studies as a measure of hemispheric specialization. The primary aim of the present study was to record regional changes in the distribution of cerebral blood flow (CBF) with the 15O-PET technique to dichotically presented consonant-vowel (CV) and musical instrument stimuli, in order to test the basic assumption of differential hemispheric involvement when stimuli presented to one ear dominate over stimuli presented in the other ear. All stimuli were 380 ms in duration with a 1000 ms interstimulus interval, and were presented in blocks of either CV-syllable or musical instrument pairs. Twelve normal healthy subjects had to press a button whenever they detected a CV-syllable or a musical instrument target in a stream of CV- and musical instrument distractor stimuli. The targets appeared equally often in the right and left ear channel. The CV-syllable and musical instrument targets activated bilateral areas in the superior temporal gyri. However, there were significant interactions with regard to asymmetry of the magnitude of peak activation in the significant activation clusters. The CV-syllables resulted in greater neural activation in the left temporal lobe while the musical instruments resulted in greater neural activation in the right temporal lobe. Within-subjects correlations between magnitude of dichotic listening and CBF asymmetry were, however, non-significant. The changes in neural activation were closely mimicked by the performance data which showed a right ear superiority in response accuracy for the CV-syllables, and a left ear superiority for the musical instruments. In addition to the temporal lobe activations, there were activation tendencies in the left inferior frontal lobe, right dorsolateral prefrontal cortex, left occipital lobe, and cerebellum.

Adult↗

PubMed1999

Effects of hypnotizability on performance of a Stroop task and event-related potentials.

The effect of hypnotizability on verbal reaction times and event-related potentials during performance of a Stroop color-naming task was studied. The Stroop stimuli (colored words) were randomly presented to 5 high and 5 low hypnotizable subjects in the right and left peripheral visual fields during both waking state and hypnotic induction conditions. Unlike studies in which the Stroop stimuli were foveally presented to the subjects, the highly hypnotizable subjects did not show prolonged verbal reaction times in either waking or hypnotic conditions. There was a marked deterioration in performance accuracy, however, for highly hypnotizable subjects during hypnosis. Event-related potentials indicated that the highly hypnotizable subjects showed a reduced P3a amplitude and a decreased N2b latency to the visual stimuli in both waking and hypnotic conditions, suggesting a lack of orienting to or disengagement from peripherally occurring stimuli.

Attention↗

PubMed1999

Left frontal activation during a semantic categorization task: an fMRI-study.

In the present study we measured brain activation, with functional magnetic resonance imaging (fMRI) during the execution of a covert semantic categorization task. This involves activation of working memory and internal concept generation. Previous brain imaging studies of covert verbal fluency have shown widespread activation in the frontal and temporal lobes, and anterior cingulate. However, most of these studies have employed simple stimulus tasks with repetition of words e.g., beginning with a certain letter of the alphabet. Moreover, the subject is typically cued (either visually or auditory) every 2-5 second. In the present study we used a "single-cue" instruction at the beginning of each activation period where the subject was instructed to internally generate category specific names related to: "States in the USA," "UK Soccer clubs," and "Male names" during 54s periods. The three activation periods were compared to three baseline periods in which the subject was instructed to imagine mentally "lying on a beach and looking at the sky." Functional MRI was performed with a 1.5T Siemens Vision scanner. Initial TIW 3D FLASH scanning of anatomy was done, and thereafter, serial imaging with 60 BOLD sensitive echo planar whole brain measurements were done during the active and passive tasks. Main activation areas were found in the left middle frontal gyrus, partially overlapping with Brodmann area 9. This is in agreement with previous studies of increased activation in the left frontal lobe, and may indicate a left frontal neural network for accessing the mental lexicon.

Acoustic Stimulation↗

PubMed1998

Central auditory processing, MRI morphometry and brain laterality: applications to dyslexia.

We review data from our laboratory related to a view of dyslexia as a biological disorder, or deficit, caused by both structural and functional brain abnormalities. The review is focused on central auditory processing in dyslexia, and the possibility that impairments in the auditory or acoustic features of the phonological code may be at the heart of the impairments seen in dyslexia. Three methodological approaches by which to investigate central auditory processing deficits are outlined: dichotic listening (DL) to consonant-vowel syllables; magnetic resonance imaging (MRI), and the use of event-related potentials (ERPs). Consonant-vowel syllable DL is a technique for probing the functional status of phonological processing areas in the superior temporal gyrus, particularly in the left hemisphere. MRI is a corresponding structural, or morphological, measure of anatomical abnormalities in the same brain region, particularly covering the planum temporale area. The ERP technique, and particularly the mismatch negativity (MMN) component, reveals cortical dysfunctions in sensory processing and memory related to basic acoustic events. For all three approaches, the dyslexic children were seen to differ from their control counterparts, including absence of modulation of the right ear advantage (REA), in DL through shifting of attention, smaller left-sided planum temporale asymmetry, and prolonged latency in the MMN ERP complex, particularly in the time-deviant stimulus condition.

Auditory Diseases, Central↗

PubMed1998

Dichotic memory: paradoxical effect of removing a left frontal gyrus: a case study.

A 27-year-old right-handed woman was operated with resection of an epileptogenic lesion, a nonmalignant tumor, in the left frontal lobe. The surrounding cortical and subcortical tissue in the tumor-containing gyrus was also resected. Care was taken during the operation not to interfere with motor or language related cortical areas. Pre- and postoperatively, she was tested with a dichotic memory test. In the preoperative test, she showed a marked Left Ear Advantage. In the corresponding tests on the second and fourth postoperative days and at follow-up, her performance had changed to a Right Ear Advantage. A possible explanation of this result is that neighboring cortical areas involved in hemispheric specialization for lateralized, verbal cognitive functions are suppressed by a focal epiletogeneic activity caused by the tumor. The subsequent removal of this influence allowed these cortical areas to function normally.

Adult↗

PubMed1998

Cortical control of human classical conditioning: autonomic and positron emission tomography data.

A recent positron emission tomography (PET) study on brain mechanisms in classical, or Pavlovian, conditioning is reviewed. The PET data were compared with skin conductance data recorded off-line. The participants were five men who participated in three different experimental phases. In the first (habituation) phase, a tone was repeated 24 times at random intervals. In the second (acquisition) phase, the tone was paired with a brief shock to the wrist. In the third (extinction) phase, the tone was presented alone again. Statistical parametric mapping analysis of the PET data showed significantly increased activation of the right hemisphere in the orbitofrontal cortex, dorsolateral prefrontal cortex, inferior and superior frontal cortices, and inferior and middle temporal cortices. In the left hemisphere, only Area 19 and the superior frontal cortex showed significant activation. The findings are discussed within a theoretical framework that argues for different brain mechanisms in acquisition and extinction in classical conditioning.

Adolescent↗

PubMed1997

Dichotic-listening performance and intracarotid injections of amobarbital in children and adolescents. Preoperative and postoperative comparisons.

BACKGROUND: Dichotic listening (DL) to consonant-vowel syllables is frequently used in clinical and experimental studies of brain laterality. However, the paradigm of consonant-vowel syllables has not been thoroughly validated through a comparison with injections of amobarbital sodium (Amytal). OBJECTIVE: To validate the DL test for hemisphere dominance preoperatively vs postoperatively with the results from intracarotid injections of amobarbital (i.e., the Wada test) in epileptic children and adolescents. DESIGN AND MAIN OUTCOME MEASURES: Patients were tested with DL preoperatively and at 6-month follow-up. Correct reports in the DL tests were entered in a stepwise discriminant analysis for calculation of correct classification of hemisphere dominance with the results from the injections of amobarbital as the grouping variable. Correct reports from the right and left ears on the consonant-vowel DL test were compared preoperatively and postoperatively, separated for the subjects with regard to language dominance in the left and right hemispheres. SETTING: The Department of Pediatrics, Ostra Hospital, University of Göteborg, Göteborg, Sweden. PATIENTS: Thirteen children and adolescents between the ages of 10 and 19 years, who were surgically treated for resistant epilepsy, were included in the study. The operated area corresponded with morphological changes and functional dysfunctions according to findings from computed tomography, magnetic resonance imaging, single photon emission computed tomography, and electroencephalography. RESULTS: The results of the Wada tests revealed that 10 subjects had left hemisphere language dominance, with 3 subjects having right hemisphere language dominance. All 3 subjects with right hemisphere language dominance showed a left ear advantage on the DL test preoperatively and postoperatively, with 8 and 7 of the 10 subjects with left hemisphere dominance showing a right ear advantage, preoperatively and postoperatively, respectively. However, according to discriminant analysis, knowledge of the DL performance led to a correct classification according to the Wada test results in 12 (92%) of the 13 subjects. CONCLUSIONS: A quantitative classification procedure like discriminant analysis may be more sensitive when predicting hemisphere speech dominance from DL data than a qualitative procedure based on the ear advantage dichotomy. The ear advantage dichotomy may actually introduce arbitrary left-right categories that do not correspond to the actual clustering of the data.

Adolescent↗

PubMed1997

Conditioned emotional cueing of spatial attentional shifts in a go/no-go RT task.

The influence of conditioned emotional arousal on selective attention was evaluated in a go/no-go version of Posner's covert attention spatial orienting task (Posner et al., 1982). Ten males and 10 females participated in the study, which consisted of two phases; an initial conditioning phase and a subsequent attention phase. In the conditioning phase, the Conditioning group received a 90-dB white noise unconditioned stimulus (UCS) contingent with presentations of a frame-lit rectangle, which thus became a conditioned stimulus (CS+), while a completely-lit rectangle was never paired with the noise and became a CS-. The Control group received non-contingent presentations of the noise and the two rectangles. In the attention phase, both groups participated in a go/no-go version of the attention orienting task, where targets were cued by both the CS+ and the CS-. Half of the subjects in both the Conditioning and the Control group were instructed to respond only to targets cued by the CS+ (go cue) and ignore targets cued by the CS- (no-go cue). The other half of the subjects responded to targets cued by the CS- and ignored targets cued by CS+. The Conditioning group identified targets at the opposite location of the CS+ significantly faster than targets at the same location. The emotional salience of the cue thus reversed the typical cost of shifting attention to targets outside the cued location.

Adult↗

PubMed1997

Relateralizing hypnosis: or, have we been barking up the wrong hemisphere?

Research and theory over the past couple decades have suggested that the right cerebral hemisphere might be the focus of brain activity during hypnosis. Recent evidence from electrodermal responding, visual event-related potentials, and Stroop interference, however, can make a case for a role of the left hemisphere in some hypnotic phenomena. Although hemispheric activation on hypnotic challenge may depend in large part on the kind of task the challenge might involve, several general aspects of hypnosis might be more appropriately seen as left-rather than right-hemisphere brain functions. Among these are concentrated attentional focus and the role of language in the establishment of hypnotic reality. A left-hemisphere theory of hypnosis is discussed in light of recent findings and theories about a left-hemisphere basis for synthetic or generational capabilities (Corballis, 1991) and a neuro-evolutionary model of a left-hemisphere dopaminergic activation system for the implementation of predetermined motor programs (Tucker & Williamson, 1984).

Attention↗

PubMed1997

Test-retest reliability for the consonant-vowel syllables dichotic listening paradigm.

The present study compared test-retest reliability for dichotic listening (DL) performance to consonant-vowel (CV) syllables under three different attentional instructions. Previous studies of reliability in dichotic listening have shown great variability which most likely reflects the large variations in stimuli, procedures, and techniques used in the different studies. Sixteen subjects were tested twice, 2 weeks apart, with the same dichotic listening procedure, including a divided attention condition and two focused attention conditions on each test occasion. The results showed test-retest correlations ranging from .61 to .86 for the three attentional conditions, with the smallest correlation coefficient for the divided attention condition.

Adult↗

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↗

PubMed1997

Thalamotomy and thalamic stimulation: effects on cognition.

Before, during and after ventrolateral thalamotomy, patients were subjected to neuropsychological tests with emphasis on verbal perception and memory. In the first study, the patients were tested with a dichotic listening task before surgery, during thalamic stimulation, and after the lesion. Left thalamic stimulation increased the number of correct responses from the right ear, whereas a left thalamotomy abolished the expected right ear superiority. Stimulation and lesions of the right thalamus did not have similar effects. In a second study, Parkinsonian patients were tested with an extended neuropsychological test battery before and after thalamotomy. The operation did not reduce the cognitive capacity in this group of patients. In the last study, the effects of thalamic stimulation on verbal memory was tested. High-intensity stimulation of the left thalamus resulted in fewer words being recalled as compared with right thalamic and low-intensity stimulation.

Auditory Perception↗

PubMed1997

Lateralized thalamic stimulation: effects on verbal memory.

This study was concerned with the effects of left- or right-thalamic stimulation on a simple verbal memory task, involving immediate free recall of lists of common words presented dichotically. The subjects were patients with Parkinson's disease undergoing stereotaxic thalamotomy. As a clinical routine, the patients also underwent a brief period of thalamic electrical stimulations before the lesion was made. The memory tests were performed during the stimulation phase of the operation and were accomplished inside the operating room. The main finding was a general deterioration of performance during thalamic stimulation compared with preoperative and postoperative testing. However, this general effect was modulated by stimulation intensity and side of stimulation. High-intensity stimulation of the left thalamus resulted in significantly fewer words being recalled compared with right thalamus stimulation and low-intensity stimulation. Finally, words presented in the first list were recalled better than words from the second and third lists, particularly during stimulation and at follow-up. The findings are discussed in relation to the thalamic activating-gating model originally proposed by Ojemann.

Adult↗

PubMed1996

Phantom limb imaginary fingertapping causes primary motor cortex activation: an fMRI study.

A conventional 1.0 T MR-scanner was used to detect signal intensity changes in blood oxygenation level dependent-sensitive acquisitions of motor cortex during real (left hand) and imaginary (right hand) fingertapping in a man who had his right arm amputated. The subject was instructed alternately to move the intact left hand fingers and to imagine tapping his 'fingers' on the amputated right hand. Activated areas were detected using a cross-correlation technique with superimposition of highly correlated voxels on to a corresponding high resolution, anatomical 3D image. Activation was observed in the right motor cortex during fingertapping with the intact left hand, and a corresponding activation in the left motor cortex for imaginary movements of the amputated right hand fingers.

Adult↗