Biomedical subjects

Kenneth Hugdahl

Publications and source records attributed to Kenneth Hugdahl.

60 records · Page 4Linked to original sources

PubMed2002

Right-left discrimination in younger and older children measured with two tests containing stimuli on different abstraction levels.

Two paper-and-pen tests, consisting of line drawings of human figures, viewed from the back, the front, or randomly alternating between back and front drawings, were used to study right-left discrimination in younger and older children. One test, called the Abstract test, had just a circle to indicate heads of the figures. The other test, called the Concrete test, showed facial characteristics and hair in the head circle. The sample consisted of 280 younger and older children, ages 7-8 and 12-13 years, respectively. The main findings were that participants who responded to the Concrete test solved more items correctly compared to those using the old figures in the Abstract test. The error scores did not differ between the tests. The older children solved more items correctly than the younger children. The older children also showed a significant decrease in correct scores on the subtest with the alternating views subtest compared with the other subtests. Their error scores did not differ across the subtests. The younger children solved a similar number of correct items on all subtests; however, they made significantly more errors on the subtest using the front view than on the other two subtests. The results are discussed in relation to theories of hemispheric lateralization, brain development, and cognitive development.

Adolescent↗

PubMed2002

Planum temporale asymmetry and ear advantage in dichotic listening in Developmental Dyslexia and Attention-Deficit/Hyperactivity Disorder (ADHD).

The planum temporale is clearly involved in language processing, for it serves as the auditory association cortex. Research has consistently demonstrated that 60 to 70% of the population has leftward asymmetry of the planum temporale. Research has also suggested that dyslexic individuals tend to have either rightward asymmetry or symmetrical plana. Moreover, many studies have found a relationship between the presence of dyslexia and/or language impairment and deficits in the normal right ear advantage found in dichotic listening paradigms. In this context, this study examined the relationship between planum temporale asymmetry and ear preference in dichotic listening performance in children with Developmental Dyslexia and Attention-Deficit/Hyperactivity Disorder (ADHD). Subjects included 19 children with dyslexia (10 of whom had a comorbid diagnosis of ADHD), 23 children with ADHD, and 12 diagnosed normal control children. Dichotic listening data were not collected for 8 of the 12 normal control children and for 3 of the 23 ADHD children. Results revealed no significant difference between ADHD and dyslexic subjects in regard to ear advantage on the free recall dichotic listening task. In addition, although the directed dichotic listening tasks were not related to degree of planum asymmetry, as predicted, results indicated that subjects who consistently displayed an atypical left ear advantage tended to have larger right bank lengths than those who consistently displayed a typical right ear advantage. These findings support the notion that some individuals with dyslexia or language deficits tend to have a larger right planum temporale and that performance on dichotic listening tasks may reflect this relatively unusual pattern.

Attention Deficit Disorder with Hyperactivity↗

PubMed2002

Bridging psychology and biology. The analysis of individuals in groups.

Biological systems are particularly prone to variation, and the authors argue that such variation must be regarded as important data in its own right. The authors describe a method in which individual differences are studied within the framework of a general theory of the population as a whole and illustrate how this method can be used to address three types of issues: the nature of the mechanisms that give rise to a specific ability, such as mental imagery; the role of psychological or biological mediators of environmental challenges, such as the biological bases for differences in dispositional mood; and the existence of processes that have nonadditive effects with behavioral and physiological variables, such as factors that modulate the response to stress and its effects on the immune response.

Affect↗

PubMed2002

A multivariate classification study of attentional orienting in patients with right hemisphere lesions.

OBJECTIVE: To characterize patterns of orienting dysfunction that were typical to patients with lesions in the right hemisphere (RH). BACKGROUND: Brain lesions in the right hemisphere are commonly associated with dysfunction of visual orienting (e.g., visual neglect and extinction). In a clinical study of these symptoms, the multicomponent nature of attentional orienting calls upon a multivariate statistical design with careful selection of neurocognitive variables. METHODS: Thirty-eight patients with verified brain lesions and four patients with peripheral motor dysfunction after poliomyelitis were included in the study. Cognitive function was evaluated in all patients. Three reaction-time (RT) measures derived from the cue-target paradigm were selected as features in a data-driven multivariate classification scheme to generate natural subgroups of patients. RESULTS: Four subgroups were generated, with only RH patients allocated to two of them. All patients within one of the RH subgroups were characterized by a pattern of impairment earlier described as a "disengage failure" by Posner et al. ( 5, 6), signs of visual neglect on Behavioral Inattention Test, and a severely impaired cognitive function. Results for the other RH subgroup were heterogeneous on both experimental and clinical variables. Age and cognitive function were found to strongly influence two of the features, but could not predict the clusters generated from the RT measures. CONCLUSIONS: The present findings show that the cue-target paradigm together with multivariate clustering of selected feature variables can serve as a useful tool to explore and characterize patients with right hemisphere lesions. Although the concept of "disengage failure" was suited to describe the typical RT pattern in patients with neglect, other neurocognitive models and concepts can be applied to the results in the current study.

Adolescent↗

PubMedDate not supplied

"Soundmorphing": a new approach to studying speech perception in humans.

A problem in current studies of brain activation in speech perception is that most studies use stimuli that are sampled from different categories. This study presents a new approach in creating acoustic stimuli by filtering real words in different ways, thus this enables one to 'morph' the sounds gradually from something like tones to real words while preserving temporal characteristics ("soundmorphing"). This will make it possible to explore steps between tone and speech processing on a gradual scale. This study aimed to investigate more closely the network, involved in the perception of speech and the decoding of auditory (speech-)stimuli. Sets of auditory stimuli were created by dividing real words into several frequency-bands and creating a randomised rearrangement of these components. Four different sets of stimuli were used, containing 1, 2, 3 or 4 frequency bands (total range: 0-2500 Hz). Only the latter one contained intelligible words. During the fMRI session, these four trial types were presented pseudo-randomised. In all conditions, significant activations of auditory cortex were observed. The number of activated voxels and their significance increased over the four trial types. In addition, Broca's area, SMA, left thalamus, and right cerebellum were activated in the most complex and most speech-like condition. Comparing these complexes with the tone-like trials, only the left auditory cortex, left SMA, and cingulate gyrus became significant. These activations reflect the bilateral processing of the auditory stimuli, but only the left temporal areas demonstrated an increasing BOLD response with an increasing number of presented frequency components.

Acoustic Stimulation↗

PubMedDate not supplied

Impaired visual attention in children with dyslexia.

Reading involves the correct and rapid identification of visual stimuli with letters and words. The processing of visual stimuli depends not only on the integrity of the peripheral and central visual system but also on the attentional systems involved. In the present study, a cue-target visual attention task was administered to a population-based sample of 25 children with dyslexia from 10 to 12 years of age. A control group matched for group size, age, and gender was obtained from the same general population. A two-stage screening process involved a spelling task of regular words followed by a battery of five single-word reading tasks. The cue-target task involved both a computer-controlled stimulus presentation and a computer-controlled measurement of reaction time. The data were analyzed by visual field, cue condition (valid, invalid, and no cue), and cue-target interval (CTI). The results showed a general pattern of slower responses in the dyslexia group compared to the control group. The dyslexia group also had longer reaction times in the short CTI condition (covert shift of attention) and in the long CTI condition (overt shift of attention). The findings may reflect a general attentional deficit to visual stimuli in dyslexia, possibly related to problems with the recruitment of necessary cognitive resources for the performance of complex reaction time tasks and for fluent reading.

Attention↗