Biomedical subjects

Kenneth Hugdahl

Publications and source records attributed to Kenneth Hugdahl.

At least 55 records · Page 3Linked to original sources

PubMed2003

Verbal laterality and handedness in patients with intracranial arachnoid cysts.

Left-handedness is most often genetic, but may also follow early, localised damage to the developing brain. This so-called "pathological" left-handedness syndrome is often associated with right hemisphere speech dominance. To find out whether verbal laterality or handedness were affected by congenital, intracranial arachnoid cysts, 51 consecutive patients with temporal or frontal arachnoid cysts were tested for handedness and verbal laterality, as measured with the dichotic listening (DL) technique. Handedness was normal in all subgroups of patients. In the preoperative DL test, only 51 % of the patients showed the normal superiority of the right ear (Right Ear Advantage - REA), significantly different from the REA frequency (74 %) in a normal reference group. Patients with a left temporal, or a frontal cyst had significantly lower preoperative REA frequencies than the reference group, whereas patients with a right temporal cyst did not differ from the reference group. Three to six months after decompressive surgery, the REA frequency (73 %) in the cyst patients was no longer different from that of the reference group. This postoperative normalization was seen both in patients with a left temporal or a frontal cyst. It is concluded that arachnoid cysts may suppress cognitive, cortical functions, and that this suppression can be reversed by surgical decompression of the cyst, even in adults. In our opinion, this cognitive "normalization" may in itself be an indication for decompressive surgery. It is further concluded that, although such cysts are congenital, the pressure from the cyst on the adjacent brain is not strong, nor persistent enough to cause a pathological left-handedness.

Arachnoid Cysts↗

PubMed2003

Lateralization of auditory-cortex functions.

In the present review, we summarize the most recent findings and current views about the structural and functional basis of human brain lateralization in the auditory modality. Main emphasis is given to hemodynamic and electromagnetic data of healthy adult participants with regard to music- vs. speech-sound encoding. Moreover, a selective set of behavioral dichotic-listening (DL) results and clinical findings (e.g., schizophrenia, dyslexia) are included. It is shown that human brain has a strong predisposition to process speech sounds in the left and music sounds in the right auditory cortex in the temporal lobe. Up to great extent, an auditory area located at the posterior end of the temporal lobe (called planum temporale [PT]) underlies this functional asymmetry. However, the predisposition is not bound to informational sound content but to rapid temporal information more common in speech than in music sounds. Finally, we obtain evidence for the vulnerability of the functional specialization of sound processing. These altered forms of lateralization may be caused by top-down and bottom-up effects inter- and intraindividually In other words, relatively small changes in acoustic sound features or in their familiarity may modify the degree in which the left vs. right auditory areas contribute to sound encoding.

Acoustic Stimulation↗

PubMed2003

Significant relation between MR measures of planum temporale area and dichotic processing of syllables in dyslexic children.

In the present study, we investigated differences between dyslexic and normal reading children in asymmetry of the planum temporale area in the upper posterior part of the temporal lobe and dichotic listening performance to consonant-vowel syllables. The current study was an extension of previous studies in our laboratory on the same participants, now including also girls and left-handers. There were 20 boys and 3 girls in the dyslexic group and 19 boys and 4 girls in the normal reading group. The age of the participants was 10-12 years for both groups. The participants were screened from a population of 950 students in the fourth school grade in the greater Bergen district. The planum temporale area was measured in sagittal magnetic resonance (MR) images. Mean left and right area and asymmetry index were compared between the groups. Dichotic presentations of consonant-vowel syllables made it possible to separately probe left and right hemisphere phonological function, and to correlate this with planum temporale area. The results showed a significantly larger left than right planum temporale area for both groups. However, while the right planum temporale area was similar for the dyslexic and control groups, the left planum temporale was significantly (one-tailed t-test) smaller in the dyslexic group. Both groups also showed a significant right ear advantage to the consonant-vowel syllables in the dichotic listening test. The relation between planum temporale and dichotic listening asymmetry showed a significant correlation for the dyslexic group only, indicating a positive relation between brain structure and function in dyslexic children. The results are discussed in terms of important subject characteristics with regard to brain markers of dyslexia.

Case-Control Studies↗

PubMed2003

The effects of attention on speech perception: an fMRI study.

Focusing of attention to a specific speech source plays an important role in everyday speech perception. However, little is known of the neuronal substrates of focused attention in speech perception. Thus, the present study investigated the effects on neuronal activation of directed attention to auditory stimuli that differed in semantic content. Using an event-related fMRI protocol, single vowels, three-phoneme pseudowords and three- and four-phoneme real nouns and words were randomly presented to the subjects during four different instructional conditions. One condition was passive listening without any specific instructions of focusing of attention. The other conditions were attention focused on either the vowels, the pseudowords or the words. Thus, the acoustic stimulation was constant across conditions. The subjects were 13 healthy adults. Functional MRI was performed with a 1.5 T scanner, using an event-related design. During passive listening, there were significant activations bilaterally in the superior temporal gyrus. Instruction to attend to the pseudowords caused activation in middle temporal lobe areas, extending more anterior compared to the activations seen during passive listening. Instruction to attend to the vowel sounds caused an increase in activation in the superior/medial temporal lobe, with a leftward asymmetry. Instruction to attend to the words caused a leftward asymmetry, particularly in the middle and superior temporal gyri. It is concluded that attention plays a modulatory role in neuronal activation to speech sounds, producing specific activations to specific stimulus categories that may act to facilitate speech perception.

Adult↗

PubMed2003

Dichotic listening performance and frontal lobe function.

In the present paper we report on speech perception in left (n=16) and right (n=10) frontal lobe nonaphasic patients compared with healthy controls (n=26). The patients were inpatients of the University Clinic of Neurology, Innsbruck, Austria, who participated in a prospective neuropsychological study dealing with several aspects of lateralized functioning. The patients were tested with dichotic presentations of consonant-vowel syllables, which allows for specific probing of speech perception in the left and right hemisphere, respectively. The task was to report which syllable they heard best on each trial, emphasizing single answers on each trial. There were 36 dichotic trials with pairs of CV syllables made up of the six stop consonants /p/, /t/, /k/, /b/, /d/, /g/, all paired with the vowel /a/. There were always two different syllables presented on each trial, one in each ear. The results showed significant differences between the left and right lesioned patients in their performance on the dichotic listening test. While the right lesioned patients and the control subjects had a normal and expected right ear advantage, the left lesioned patients performed almost at random with regard to the right and left ear stimulus. The right lesioned patients and the control group showed a right ear advantage of the same magnitude, although the overall performance was somewhat impaired in the right lesioned group compared to the healthy control group. The left lesioned patients showed no ear advantage at all, and particularly their right ear scores were impaired compared to both the control group and the right lesioned patient group. The results are discussed in terms of the role played by the left frontal cortex in speech perception and language asymmetry.

Adult↗

PubMed2003

Focused attention in a simple dichotic listening task: an fMRI experiment.

Whole-head functional magnetic resonance imaging (fMRI) was used in nine neurologically intact subjects to measure the hemodynamic responses in the context of dichotic listening (DL). In order to eliminate the influence of verbal information processing, tones of different frequencies were used as stimuli. Three different dichotic listening tasks were used: the subjects were instructed to either concentrate on the stimuli presented in both ears (DIV), or only in the left (FL) or right (FR) ear and to monitor the auditory input for a specific target tone. When the target tone was detected, the subjects were required to indicate this by pressing a response button. Compared to the resting state, all dichotic listening tasks evoked strong hemodynamic responses within a distributed network comprising of temporal, parietal, and frontal brain areas. Thus, it is clear that dichotic listening makes use of various cognitive functions located within the dorsal and ventral stream of auditory information processing (i.e., the 'what' and 'where' streams). Comparing the three different dichotic listening conditions with each other only revealed a significant difference in the pre-SMA and within the left planum temporale area. The pre-SMA was generally more strongly activated during the DIV condition than during the FR and FL conditions. Within the planum temporale, the strongest activation was found during the FR condition and the weakest during the DIV condition. These findings were taken as evidence that even a simple dichotic listening task such as the one used here, makes use of a distributed neural network comprising of the dorsal and ventral stream of auditory information processing. In addition, these results support the previously made assumption that planum temporale activation is modulated by attentional strategies. Finally, the present findings uncovered that the pre-SMA, which is mostly thought to be involved in higher-order motor control processes, is also involved in cognitive processes operative during dichotic listening.

Acoustic Stimulation↗

PubMed2003

Selective impairment in effortful information processing in major depression.

Automatic and effortful information processing in depressed patients was investigated by a visual search paradigm, in order to examine dysfunctional effortful processing in depressed patients. Twenty-one patients with major depression, according to the DSM-IV, and with a moderate depression measured by the Hamilton Rating Scale score at >18 participated in the study. The healthy control group was matched for age, gender, and level of education. Half of the trials involved only one type of distractor, and the other half of the trials involved two types of distractors being presented. The results show that the performance of the depressed patients was equal to the control group when the target was easily recognized with only one type of distractor present. However, when target detection required a more difficult and complex attentive search strategy, effortful information processing, the depressed patients needed longer visual search time compared to the controls. Depressed patients seem to have impaired performance on effortful but not automatic information processing.

Adult↗

PubMed2003

Sensitivity and specificity of memory dysfunction in schizophrenia: a comparison with major depression.

Fifty-three schizophrenic subjects were compared to 50 patients with major depression and 50 normal controls on measures of working memory, declarative memory and malingering. The schizophrenic group scored 1-2 SDs below controls on all measures, while depressive patients exposed only lesser deficits in working memory and free recall. The memory deficit of the schizophrenic subjects was disproportionately greater than their intellectual decline. Differences between clinical groups could not be explained by differences in IQ, clinical symptom load or demographic characteristics. This indicates that impaired memory is a particular sensitive symptom of schizophrenia and that the impairment is specific to the illness. Working memory failure was prominent in both clinical groups. The schizophrenic subjects displayed primarily an acquisition failure, while the depressed group showed retrieval difficulties.

Adult↗

PubMed2003

Speech lateralization and attention/executive functions in a Finnish family with specific language impairment (SLI).

Hemisphere lateralization for speech perception was investigated in a Finnish family with specific language impairment. We used dichotic presentations of consonant-vowel (CV) syllables, consisting of the six stop-consonants paired with the vowel /a/, under three different attentional instructions. The dichotic listening technique means that two different speech stimuli are presented simultaneously, one in each ear. Left hemisphere dominance for speech perception is assessed from a preference for the right ear stimulus. Response accuracy was compared in five members, over three generations, of a family with SLI with 5 healthy control subjects. The dichotic listening task was performed under three different instructions, to attend only to the right ear stimulus, to attend only to the left ear stimulus, or with no instruction about attention. The subjects indicated orally which of the six CV-syllables they heard on each trial. There were 36 dichotic presentations of the CV-syllables for each instruction. The CV-syllables were played from a CD with digitized stimuli. The results showed no difference between the groups during the no instruction condition, indicating normal speech lateralization in the SLI group. However, the SLI group was deficient in modifying the ear advantage through focused attention to the left ear, thus indicating an attentional/executive deficit in addition to a deficit in left hemisphere lateralization. It is concluded that individuals with specific language impairment may have a cognitive deficit related to attention in addition to a language processing deficit related to left hemisphere function.

Attention↗

PubMed2003

Left hemisphere dysfunction affects dichotic listening in patients with temporal lobe epilepsy.

This study evaluated the relative effect of left hemisphere dysfunction and side of seizure onset on dichotic listening performance in patients with temporal lobe epilepsy and left hemisphere speech dominance. Seventeen patients were divided into groups based on side of seizure onset and based on scores on a composite measure revealing left hemisphere dysfunction. The group with left hemisphere dysfunction had more correct responses from the left ear, and a left ear advantage, on dichotic listening. The group with normal left hemisphere function showed the expected right ear advantage. Side of seizure onset did not affect dichotic listening performance significantly.

Acoustic Stimulation↗

PubMed2003

Neuropsychological profile of patients with Parkinson's disease without dementia.

Cognitive deficits are often associated with Parkinson's disease (PD), although their prevalence in PD patients without dementia is still unknown. In order to describe the neuropsychological profile of PD patients without dementia, a sample of 103 PD patients was compared with a control group consisting of 38 healthy elderly subjects. Psychometric assessment consisted of the Mini Mental State Examination, the Dementia Rating Scale and a battery of neuropsychological tests. The Beck Depression Inventory was used to assess depression in PD patients. Dementia was diagnosed in 27 patients. Among non-demented subjects, 34 (45%) had no cognitive impairment and 42 (55%) had a mild cognitive impairment. Subjects with mild cognitive impairment were older, had a later onset of the disease, and more severe motor symptoms than cognitively intact subjects. Identification of mild cognitive impairment is important, since these symptoms are important for patient management and may also facilitate to determine prognosis.

Aged↗

PubMed2002

Functional brain asymmetry and attentional modulation in young and stabilised schizophrenic patients: a dichotic listening study.

Impaired functional brain asymmetry has been shown in schizophrenic patients, in addition to attentional deficits related to this laterality impairment. However, it has usually been shown in older patients with frequent positive symptoms. This is a matter of concern because previous studies have suggested that such deficits interact with subgroup characteristics, especially positive symptoms like hallucinations and age/duration of the illness. Thus, in this study, we tested a homogeneous group of young and stabilised schizophrenic patients. We used a verbal dichotic listening test with consonant-vowel syllables to study brain asymmetry and attentional modulation. Nineteen patients were compared with healthy subjects with the same age, handedness and gender distribution. All subjects were tested during a divided and two focused attention conditions. The patient and reference group showed the same performance pattern. This indicates that young and stabilised patients show normal functional brain asymmetry and normal ability to modulate attention. It is suggested that impairments in functional asymmetry and attentional modulation may follow a continuum related to symptomatology and age/duration of illness.

Adult↗

PubMed2002

Less developed corpus callosum in dyslexic subjects--a structural MRI study.

BACKGROUND: Based on previous studies and due to the characteristics of dyslexia as an auditory phonological decoding disorder, we predicted that the shape of the posterior corpus callosum (CC) would differ between dyslexic and control subjects. METHOD: Twenty right-handed boys with developmental dyslexia were selected from a carefully screened general population sample (mean age 11 years) and compared to a matched control group. The CC contour was manually traced on the aligned midsagittal MR slice and total callosal area and its subregions were compared between the groups. A statistical shape analysis and subsequent CC classification was performed using a recently developed shape model method. RESULTS: The shape analysis revealed shorter CC shape in the dyslexic group, localised in the posterior midbody/isthmus region. This region contains interhemispheric fibers from primary and secondary auditory cortices. A shape length difference larger than a fixed threshold in the posterior midbody region could correctly discriminate between control and dyslexic subject in 78% of the cases, where a dyslexic CC was shorter in this region than a control CC. However, there were no significant group differences with respect to overall CC area or subregions. CONCLUSION: A clear shape difference in the posterior midbody of the CC was found between dyslexic and control subjects. This fits with recent other studies that have reported a strong growth factor in this CC region during the late childhood years, coinciding with literacy acquisition. Our results show that the dyslexic group has not undergone the same growth pattern as the normal reading group.

Agenesis of Corpus Callosum↗

PubMed2002

Adrenocortical stress responses and altered working memory performance.

This study examined stress cortisol responses and cognitive performance. We initially measured cortisol responses of 40 right-handed healthy male volunteers to counterbalanced mental arithmetic and public speaking stressors. We then examined the relationship between cortisol reactivity and dichotic listening and mental arithmetic performance. High cortisol responders made more errors and completed fewer mental arithmetic items than low reactors. On dichotic listening, high responders tended toward better performance in all conditions and to both ears. High responders showed better performance to the right ear in the forced right than in the nonforced condition, whereas no difference between these conditions was found in low responders. High cortisol responders may have an increased focus on sensory stimuli and a decreased allocation of resources to working memory tasks.

Adrenal Cortex↗

PubMed2002

Dichotic listening in patients with splenial and nonsplenial callosal lesions.

The authors found splenial lesions to be associated with left ear suppression in dichotic listening of consonant-vowel syllables. This was found in both a rapid presentation dichotic monitoring task and a standard dichotic listening task, ruling out attentional limitations in the processing of high stimulus loads as a confounding factor. Moreover, directed attention to the left ear did not improve left ear target detection in the patients, independent of callosal lesion location. The authors' data may indicate that auditory callosal fibers pass through the splenium more posterior than previously thought. However, further studies should investigate whether callosal fibers between primary and secondary auditory cortices, or between higher level multimodal cortices, are vital for the detection of left ear targets in dichotic listening.

Adult↗

PubMed2002

Right-left discrimination in male and female, young and old subjects.

The present study investigated right-left discrimination, with a paper-and-pen test using line figures. The test consists of line drawings of a person with no, one, or both arms crossing the vertical body axis of the figure. The subjects' task is to mark with a pencil, as fast as possible, which is the right or left hand in the figure. The line drawings are either viewed from the back, from the front, or randomly alternating between the back and front views. The sample consisted of 322 male and female subjects, split into four different groups, from children to old adults. The results showed increasing performance from children to young adults, with a decline in performance in the old adults (>50 years). The condition with alternating front-back views was the most difficult, particularly when the figure also had both arms crossing the vertical body midline. There were no gender differences except for better male performance in the young adults group (18-22 years). The results are discussed in relation to theories of mental rotation and lateralization of information processing strategies, in addition to right-left discrimination across the age groups.

Adolescent↗

PubMed2002

Dichotic listening and sleep deprivation: vigilance effects.

Twelve sleep-deprived and 13 non-deprived Navy cadets were tested with the dichotic listening procedure for effects of sleep deprivation on hemispheric asymmetry and sustained attention. Consonant-vowel syllables were presented to the subjects in three different conditions, a divided (non-forced) attention condition, a forced right ear and a forced left ear attention condition. In the two forced attention conditions the subjects were instructed to focus attention only on the right or left ear stimulus. The results showed an expected right ear advantage for both groups during the non-forced and forced right attention conditions, indicating superior left hemisphere processing. During the forced left attention condition, the sleep-deprived subjects showed no ear advantage at all, while the non-deprived subjects showed an expected left ear advantage. The results are discussed within a theoretical framework of a dual process model, where sleep deprivation disrupts the ability to sustain attention, caused by a temporary failure of the right hemisphere's top-down (instruction-driven) processing to override the left hemisphere's bottom-up (stimulus-driven) processing.

Adult↗

PubMed2002

Auditory processing in children with dyslexia.

BACKGROUND: It has been claimed that children with dyslexia show a general impairment in the processing of rapid auditory stimuli. However, most previous studies in this field have focused on children with language impairment or children who do not meet accepted criteria for dyslexia. METHODS: In the present study, the processing of rapid non-verbal auditory stimuli (complex tones) was examined in a population-based sample of 24 children with dyslexia, 10 to 12 years of age, and a matched control group. RESULTS: The dyslexia group showed reduced tone processing relative to the control group, with significant main effects of tone duration, inter-stimulus interval and task complexity. The deficit was not specific for temporal order errors, and could not be explained by differences in short-term memory or verbal IQ. However, correlations between tone processing and reading ability were generally low or absent. CONCLUSION: Although a general processing deficit for rapid auditory stimuli in dyslexia was confirmed, its relevance for reading problems and hence for treatment programmes for dyslexia is questioned.

Acoustic Stimulation↗