Biomedical subjects

Kenneth Hugdahl

Publications and source records attributed to Kenneth Hugdahl.

At least 37 records · Page 2Linked to original sources

PubMed2005

Asymmetry of evoked potential latency to speech sounds predicts the ear advantage in dichotic listening.

The functional organization of the human auditory cortex is still not well understood with respect to speech perception and language lateralization. Especially, there is comparatively little data available in the brain imaging literature focusing on the timing of phonetic processing. We recorded auditory-evoked potentials (AEP) from 27 scalp and additional EOG channels in 12 healthy volunteers performing a free report dichotic listening task with simple speech sounds (CV syllables: [ba], [da], [ga], [pa], [ta], [ka]). ERP analysis employed independent components analysis (ICA) wavelet denoising for artifact reduction and improvement of the SNR. The main finding was a 15-ms shorter average latency of the N1-AEP recorded from the scalp approximately overlying the left supratemporal cortical plane compared to the N1-AEP over the homologous right side. Corresponding N1 amplitudes did not differ between these sites. The individual AEP latency differences significantly correlated with the ear advantage as an index of speech/language lateralization. The behaviorally relevant difference in N1 latency between the hemispheres indicates that an important key to understanding speech perception is to consider the functional implications of neuronal event timing.

Acoustic Stimulation↗

PubMed2005

Processing of conflicting cues in an attention-shift paradigm studied with fMRI.

We investigated the effects of conflicting cues in visual attention on brain function, based on a modified version of the Posner cue-target paradigm. The classic paradigm utilizes either a peripheral or centrally placed cue that involuntary or voluntary results in a shift of attention to the cued side. The modified paradigm involves presenting both a peripheral and central cue at the same time, but where the two cues convey conflicting information regarding direction of attention. Functional magnetic resonance imaging (fMRI) were used to record neuronal activation in localized brain areas and networks when the subjects performed the attention task. We hypothesized that the 'exogenous invalid/endogenous valid' condition would activate the anterior attention system to a larger extent than the 'exogenous valid/endogenous invalid' condition, reflecting a need for top-down information processing in this condition. The results for performance data showed that the peripheral cue took precedence over the centrally placed cue when the two cues were in conflict, since reaction times were significantly longer in the "exogenous invalid/endogenous valid" condition. The fMRI data showed an increase in activation in the visual cortex, the left parietal lobule, and in the left cingulate gyrus in both the exogenous valid/endogenous invalid and exogenous invalid/endogenous valid conditions. For the exogenous invalid/endogenous valid condition, there were, in addition, significant activations also in the inferior and middle frontal gyri, and in the precentral gyrus. We interpret these findings as reflecting that these brain areas particularly involved in top-down modulation of attention that interferes with a bottom-up, exogenous-driven effect.

Adult↗

PubMed2005

Arachnoid cysts cause cognitive deficits that improve after surgery.

The authors investigated cognition in patients with arachnoid cysts by assessing 55 patients and 32 control subjects on four different cognitive tests preoperatively and 3 months postoperatively. The patients improved their performance from preoperative to postoperative testing, whereas the control subjects did not show a similar improvement.

Adolescent↗

PubMed2005

Reversing spoken items--mind twisting not tongue twisting.

Using 12 participants we conducted an fMRI study involving two tasks, word reversal and rhyme judgment, based on pairs of natural speech stimuli, to study the neural correlates of manipulating auditory imagery under taxing conditions. Both tasks engaged the left anterior superior temporal gyrus, reflecting previously established perceptual mechanisms. Engagement of the left inferior frontal gyrus in both tasks relative to baseline could only be revealed by applying small volume corrections to the region of interest, suggesting that phonological segmentation played only a minor role and providing further support for factorial dissociation of rhyming and segmentation in phonological awareness. Most importantly, subtraction of rhyme judgment from word reversal revealed activation of the parietal lobes bilaterally and the right inferior frontal cortex, suggesting that the dynamic manipulation of auditory imagery involved in mental reversal of words seems to engage mechanisms similar to those involved in visuospatial working memory and mental rotation. This suggests that reversing spoken items is a matter of mind twisting rather than tongue twisting and provides support for a link between language processing and manipulation of mental imagery.

Acoustic Stimulation↗

PubMed2004

Dichotic listening in schizophrenic patients: effects of previous vs. ongoing auditory hallucinations.

Auditory hallucinations (AH) in schizophrenia have been found to be related to both functional and structural brain abnormalities of left temporal lobe language areas. We do not know if these rain abnormalities are state or trait markers for AH. This study tested these alternatives by contrasting schizophrenic patients with ongoing AH and with a previous history of AH. A heterogeneous group of 26 schizophrenic patients was compared with a healthy control group matched for education and age. We used a verbal dichotic listening (DL) test with consonant-vowel syllables to study hemispheric asymmetry and the functional integrity of the left temporal lobe language areas. All subjects were tested during a divided and two focused attention conditions. Our data suggest that abnormal DL asymmetry for language stimuli is a state marker for AH, seen during the perception of AH. In contrast, problems of modulating DL performance by means of attentional control are a trait marker, seen both in patients with ongoing AH and only a history of AH.

Adult↗

PubMed2004

Impairment in visual and spatial perception in schizophrenia and delusional disorder.

The Judgment of Line Orientation Test, a visuospatial processing task, was administered to normal subjects, to schizophrenic patients and to patients with delusional disorder. Significantly better performance was seen in the normal subjects than in the schizophrenic and delusional patients. Delusional patients, in turn, showed better performance than the schizophrenic patients.

Adolescent↗

PubMed2004

Early visual information processing in schizophrenia compared to recurrent depression.

Patients with schizophrenia have repeatedly shown deficits in early visual processing using backward masking (VBM) tasks. Whether this represents a specific dysfunction in schizophrenia is an unsolved question. Patients with recurrent unipolar depression represent an interesting comparison group to examine the question of specificity, but have never previously been assessed on VBM. In addition to comparing VBM performance in patients with schizophrenia and patients with depression, we wanted to examine the relations between VBM and clinical symptoms. Fifty-one patients with schizophrenia were compared to 49 patients with recurrent unipolar depression and 47 healthy controls. All subjects were administered a two-digit identification task in a no-masking and four masking conditions. Patients with schizophrenia performed significantly worse than normal controls on four of the five conditions. No significant difference was found between depression patients and normal controls. The effect of masking stimuli had no differential effects on the three groups. VBM correlated strongly with positive symptoms in the schizophrenia group.

Adult↗

PubMed2004

Auditory target detection in dichotic listening involves the orbitofrontal and hippocampal paralimbic belts.

In dichotic listening, two similar, yet different stimuli are presented simultaneously to the left and right ear. When two syllables are presented in this way, they seem to blend and discrimination of syllables presented to one ear is only possible with uncertainty. In this event-related fMRI study, we found that the orbitofrontal and paralimbic belts were involved in target detection in dichotic listening. The posterior orbital gyri bilaterally, the left amygdala, hippocampal formation and the left pregenual paracingulate area (PPA) were activated more strongly during dichotic target detection than during correct rejection of target presence. The right posterior orbital gyrus also showed stronger activation during dichotic compared to diotic target detection. Further analyses showed that the blood oxygen level dependent (BOLD) responses in these areas, with the exception of the right hippocampal formation, varied with the subjective decision on target presence rather than with the physical target presence itself. The left PPA, amygdala and hippocampal formation responded differently to left and right ear target detection, suggesting their involvement in the right ear advantage observed in this task. The data show the importance of the orbitofrontal and hippocampal paralimbic belts for auditory stimulus decision processes based on ambivalent sensory information.

Adult↗

PubMed2004

Blind individuals show enhanced perceptual and attentional sensitivity for identification of speech sounds.

We report on enhanced processing of speech sounds in congenitally and early blind individuals compared with normally seeing individuals. Two different consonant-vowel (CV) syllables were presented via headphones on each presentation. We used a dichotic listening (DL) procedure with pairwise presentations of CV syllables. The typical finding in this paradigm is a right ear advantage, indicating better processing of the CV-syllable stimuli in the left hemisphere. The dichotic listening procedure involved three different conditions, with instructions to pay attention to the right ear stimulus, the left ear stimulus or no specific instruction. The participants were 14 congenitally or early blind Finnish-speaking individuals that were compared with 129 normal seeing Finnish-speaking individuals. The blind participants reported overall significantly more correct syllables than seeing control subjects. When instructed to pay attention to the left ear stimulus and only report from the attended channel, they were again significantly better than the seeing control subjects. These findings indicate effects of hemispheric reorganization in blind individuals at both the sensory and cognitive levels of information processing in the auditory sensory modality.

Acoustic Stimulation↗

PubMed2004

Dichotic listening reveals functional specificity in prefrontal cortex: an fMRI study.

The present study used fMRI to investigate the relationship between stimulus presentation mode and attentional instruction in a free-report dichotic listening (DL) task with consonant-vowel (CV) syllables. Binaural and dichotic CV syllables were randomly presented to the subjects during four different instructional conditions: a passive listening instruction and three active instructions where subjects listened to both ears, right ear and left ear, respectively. The results showed that dichotic presentations activated areas in the superior temporal gyrus, middle and inferior frontal gyrus and the cingulate cortex to a larger extent than binaural presentations. Moreover, the results showed that increase of activation in these areas was differentially dependent on presentation mode and attentional instruction. Thus, it seems that speech perception, as studied with the DL procedure, involves a cortical network extending beyond primary speech perception areas in the brain, also including prefrontal cortex.

Adult↗

PubMed2004

Brain localization of attentional control in different age groups by combining functional and structural MRI.

The present study used functional and structural MRI to investigate differences in neuronal substrates underlying shifts of attention in young and old subjects, studied with dichotic listening. Two different consonant-vowel syllables were presented and the subjects were instructed to attend to and report from either the left or right ear stimulus. Typically, a right-ear advantage is observed when attending to the right-ear stimulus, and a left-ear advantage when attending to the left-ear stimulus. The behavioral results showed that the old group had difficulties with attentional modulation of the right-ear advantage in the attend left condition. This is interpreted as a failure of an important aspect of attentional control; the top-down biasing of attention for selection of task-relevant stimulus. The fMRI results showed that an area in the left middle frontal gyrus was more activated in the young group compared to the old group in the attend left condition. The structural MRI data showed reduced gray matter density of the same area in the old group. Based on these converging findings, we suggest that the left middle frontal gyrus plays an important role in top-down biasing of selecting task-relevant stimuli, and to inhibit processing of task-irrelevant stimuli. To our knowledge, this is one of the first studies addressing the question on how age-related changes in attentional processing is reflected in both functional and structural differences in the brain.

Adult↗

PubMed2004

FMRI brain activation in a finnish family with specific language impairment compared with a normal control group.

The aim of the present study was to investigate differences in brain activation in a family with SLI as compared to intact individuals with normally developed language during processing of language stimuli. Functional magnetic resonance imaging (fMRI) was used to monitor changes in neuronal activation in temporal and frontal lobe areas in 5 Finnish family members with specific language impairment (SLI) and 6 individuals in an intact control group. Magnetic resonance (MR) image acquisitions were made while the participants listened to series of isolated vowel sounds, pseudowords, and real words. The stimuli were digitized single Finnish vowel sounds, 3-phoneme pseudowords, and 3- and 4-phoneme real words. MR scanning was made with a 1.5 T Siemens Vision Plus scanner, and the auditory stimuli were presented according to an event-related fMRI design. The results showed significant differences between the family with SLI and the intact control group with regard to brain activation in areas in the temporal and frontal lobes. Temporal lobe activation differences were most pronounced in the middle temporal gyrus bordering the superior temporal sulcus. The control participants also activated an area in the inferior frontal lobe in BA 44. It is concluded that individuals with SLI showed reduced activation in brain areas that are critical for speech processing and phonological awareness. The present functional brain imaging data fit well with other recent imaging data that also showed structural abnormalities in the same and neighboring areas.

Acoustic Stimulation↗

PubMed2004

Language asymmetry and auditory attention in young adulthood after being born small-for-gestational age or with cardio-pulmonary resuscitation at birth.

A dichotic listening test with consonant-vowel syllables was used to assess language asymmetry and shift of attention in 42 young adults who had been in need of cardio-pulmonary resuscitation at birth, with a mild or moderate clinical course during the neonatal period (n = 31), or were born small-for-gestational age (SGA; n = 11) and compared with healthy controls (n = 17). All the participants were followed up prospectively and displayed no neurological or developmental deficits at 18 months of age. All the groups had an expected right-ear advantage during a baseline condition with no instructions to shift attention. The SGA group and the moderate resuscitated group displayed clear signs of an attenuation of the right-ear advantage and they were also less able to modify the ear preference in forced-attention conditions, compared with the control group. The main finding was that the groups with the most severe pre- and perinatal complications were also most affected on the dichotic listening test at adult age.

Adult↗

PubMed2004

Altered interhemispheric connectivity in individuals with Tourette's disorder.

OBJECTIVE: The corpus callosum is the major commissure connecting the cerebral hemispheres. Prior evidence suggests involvement of the corpus callosum in the pathophysiology of Tourette's disorder. The authors assessed corpus callosum size and anatomical connectivity across the cerebral hemispheres in persons with Tourette's disorder. METHOD: The size of the corpus callosum was determined on the true midsagittal slices of reformatted, high-resolution magnetic resonance imaging scans and compared across groups in a cross-sectional case-control study of 158 subjects with Tourette's disorder and 121 healthy comparison subjects, ages 5-65 years. RESULTS: In the context of increasing midsagittal corpus callosum area from childhood to age 30 years, children with Tourette's disorder had smaller overall corpus callosum size, whereas adults with Tourette's disorder on average had larger corpus callosum size, yielding a prominent interaction of diagnosis with age. Corpus callosum size correlated positively with tic severity. Corpus callosum size also correlated inversely with dorsolateral prefrontal and orbitofrontal cortical volumes in both the subjects with Tourette's disorder and the comparison subjects, but the magnitudes of the correlations were significantly greater in the group with Tourette's disorder. The effects of medication and comorbid illnesses had no appreciable influence on the findings. CONCLUSIONS: Given prior evidence for the role of prefrontal hypertrophy in the regulation of tic symptoms, the current findings suggest that neural plasticity may contribute to smaller corpus callosum size in persons with Tourette's disorder, which thereby limits neuronal trafficking across the cerebral hemispheres and reduces input to cortical inhibitory interneurons within the prefrontal cortices. Reduced inhibitory input may in turn enhance prefrontal excitation, thus helping to control tics and possibly contributing to the cortical hyperexcitatibility reported previously in patients with Tourette's disorder.

Adolescent↗

PubMed2004

Brain activation measured with fMRI during a mental arithmetic task in schizophrenia and major depression.

OBJECTIVE: The authors used functional magnetic resonance imaging (fMRI) to investigate brain activation in patients with schizophrenia and major depression while they performed two tasks-a vigilance task and a mental arithmetic task-that differed in cognitive complexity. METHOD: In the vigilance task, the participants had to press a response button whenever a specific number was seen on a screen inside the MR scanner. In the mental arithmetic task, the participants had to add two consecutive numbers and press the response button whenever the sum was 10. fMRI was performed with a 1.5-T MR scanner. Twelve patients with recurrent nonpsychotic unipolar major depression, 12 patients with schizophrenia, and 12 healthy comparison subjects were included in the study. RESULTS: Performance data showed that the patients were impaired relative to the comparison subjects and showed no difference in performance between the patient groups. The patients with schizophrenia, but not those with major depression, had less activation in prefrontal brain regions, relative to the comparison participants. However, subtracting brain activation during the vigilance task from activation during the mental arithmetic task showed that the schizophrenia patients had activation in parietal areas. CONCLUSIONS: A double dissociation of parietal and frontal lobe activation was found for the schizophrenia patients and the depression patients. The greater parietal lobe activation in the patients with schizophrenia may reflect a compensatory strategy for the failure to recruit cognitive processes that involve frontal lobe areas when solving a mental arithmetic task.

Adult↗

PubMed2004

Sleep deprivation and hemispheric asymmetry for facial recognition reaction time and accuracy.

We investigated the processing of emotional stimuli during a non-sleep-deprived state and following sleep deprivation in 36 right-handed men. Using the visual half-field technique, cartoon line drawings of emotional facial expressions were flashed on a computer screen for 250 msec. The participants were instructed to remember the content of the picture seen and to recognize it among nine alternatives shown immediately after the display of a single picture. Compared to the nondeprived condition, response latencies increased and accuracy decreased in sleep deprivation. Moreover, response latencies indicated that the performance of the right hemisphere deteriorated more following sleep deprivation than did the performance of the left hemisphere. The results also showed that hemispheric preference (for response latencies and response accuracy) tended to favour the left hemisphere when the participants were tested during sleep deprivation.

Adult↗

PubMed2003

Long-lasting cognitive impairment in unipolar major depression: a 6-month follow-up study.

The aim of the study was to investigate cognitive impairment in major depression both acutely and after 6 months. All patients were investigated within a neurocognitive experimental setting at two testing sessions: at inclusion and after 6 months. Automatic and effortful information processing was investigated with a visual search paradigm. Twenty-one patients with recurrent major depression according to DSM-IV and a Hamilton Depression Rating Scale score >18 were included in the study. Healthy subjects, matched for age and gender, were used as a control group. The results showed that the depressed patients performed equal to the control group on trials requiring automatic information processing at both sessions. However, the patients were impaired compared to the control group on trials requiring effortful information processing, also at both sessions. The depressed patients showed no improvement in cognitive performance from test 1 to test 2. The results indicate that the depressed patients had an impaired performance for effortful, but not automatic, visual search performance, and that the impairment remained after 6 months, despite significant improvement in their depression scores.

Adult↗

PubMed2003

Attentional and executive dysfunctions in schizophrenia and depression: evidence from dichotic listening performance.

BACKGROUND: We compared performance on a dichotic listening (DL) task between schizophrenic, depressed, and healthy control subjects. A variant of the traditional DL paradigm was used in which the subjects were required to focus attention either on the left (forced-left condition) or right (forced-right condition) ear stimulus. METHODS: The subjects were 51 patients with a DSM-IV diagnosis of schizophrenia, 49 patients with recurrent unipolar major depression, and 49 healthy control subjects. They were tested with a consonant-vowel syllables dichotic listening task under three attentional instructions. RESULTS: There was a significant overall right ear advantage during the nonforced condition, which increased dramatically during the forced-right condition and was eliminated during the forced-left condition. The depressed patients showed no signs of impairments compared with the healthy control group. Thus, they showed a right ear advantage during the nonforced and forced-right conditions, which was shifted to a left ear advantage during the forced left condition. The schizophrenic patients, however, were impaired on the forced-left condition compared with the healthy control and depressed subjects. CONCLUSIONS: The results are discussed in terms of separating attentional and inhibitory executive impairments in schizophrenia and depression, taking into consideration illness duration and information-processing demands.

Attention↗