333 research outputs found
Auditory processing in children with dyslexia
No full textBackground: 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.<br/
Behaviour problems in children with dyslexia
No full textThe association between behaviour problems and dyslexia was assessed in a population sample of 10- to 12-year-old children. Twenty-five dyslexic children and a matched control group were recruited through a screening in primary schools in the city of Bergen, Norway. For the assessment of behaviour problems the Child Behavior Checklist (CBCL), Teacher Self Report (TRF), and Youth Self Report (YSR) were filled out by parents, teachers, and children, respectively. Information on health and developmental factors were obtained from parents on a separate questionnaire designed for the study. The dyslexic group had significantly more behaviour problems than the control group according to both the CBCL and the TRF. On the YSR there was no significant difference between the groups. Dyslexic children had higher CBCL and TRF scores on the Total Behaviour Problem scale, the Internalizing and Externalizing subdomains, and the Attention problem subscale. The groups differed in social background, prenatal risk factors, birth weight, preschool language problems, and IQ, but these variables showed no relationship to the level of behaviour problems in the present sample. We conclude that pre-adolescent dyslexic children show a wide range of behaviour problems that cannot be attributed to social or developmental background variables
sj-docx-1-jop-10.1177_02698811231168243 – Supplemental material for Signatures of exposure to childhood trauma in young adults in the structure and neurochemistry of the superior temporal gyrus
No full textSupplemental material, sj-docx-1-jop-10.1177_02698811231168243 for Signatures of exposure to childhood trauma in young adults in the structure and neurochemistry of the superior temporal gyrus by Piril Hepsomali, Sandra Machon, Holly Barker, David J Lythgoe, Kenneth Hugdahl, Maria Gudbrandsen and Paul Allen in Journal of Psychopharmacology</p
Default mode network alterations underlie auditory verbal hallucinations in schizophrenia
No full textAlthough alterations of the default mode network (DMN) in schizophrenia (SZ) have been largely investigated, less research has been carried out on DMN alterations in different sub-phenotypes of this disorder. The aim of this pilot study was to compare DMN features among SZ patients with and without auditory verbal hallucinations (AVH). Three groups of 17 participants each were considered: patients with hallucinations (AVH-SZ), patients without hallucinations (nAVH-SZ) and age-matched healthy controls (HC). The DMN spatial pattern was similar between the nAVH-SZ and HC, but the comparison between these two groups and the AVH-SZ group revealed alterations in the left Angular Gyrus (lAG) node of the DMN. Using a novel approach based on normalized fractional Amplitude of Low-Frequency Fluctuations (fALFF), the AVH-SZ subgroup showed altered spectral activity in the DMN compared with the other two groups, especially in the lower-frequency bands (0.017–0.04 Hz). Significant positive correlations were found for both SZ groups collapsed, and for the nAVH-SZ group alone between delusional scores (PANSS-P1) and slow fALFF bands of the DMN. Narrowing the analysis to the ROI centered on the lAG, significant correlations were found in the AVH-SZ group for hallucination scores (PANSS- P3) and Slow-5 and Slow-4 (both positive), and Slow-3 (negative) fALFF bands. Our results reveal the central role of the lAG in relation to hallucinations, an important cortical area connecting auditory cortex with several hubs (including frontal linguistic centers) and involved in auditory process monitoring
Presentation of the Swedish Institute for Disability research (SIDR)
No full textEvaluators: Kenneth Hugdahl and Ruth Campbell</p
fMRI fluctuations within the language network are correlated with severity of hallucinatory symptoms in schizophrenia
No full textAbstract Although schizophrenia (SZ) represents a complex multiform psychiatric disorder, one of its most striking symptoms are auditory verbal hallucinations (AVH). While the neurophysiological origin of this pervasive symptom has been extensively studied, there is so far no consensus conclusion on the neural correlates of the vulnerability to hallucinate. With a network-based fMRI approach, following the hypothesis of altered hemispheric dominance (Crow, 1997), we expected that LN alterations might result in self-other distinction impairments in SZ patients, and lead to the distressing subjective experiences of hearing voices. We used the independent component analysis of resting-state fMRI data, to first analyze LN connectivity in three groups of participants: SZ patients with and without hallucinations (AVH/D+ and AVH/D–, respectively), and a matched healthy control (HC) group. Then, we assessed the fMRI fluctuations using additional analyses based on fractional Amplitude of Low Frequency-Fluctuations (fALFF), both at the network- and region of interest (ROI)-level. Specific LN nodes were recruited in the right hemisphere (insula and Broca homologous area) for AVH/D+ , but not for HC and AVH/D–, consistent with a left hemisphere deficit in AVH patients. The fALFF analysis at the ROI level showed a negative correlation between fALFF Slow-4 and P1 Delusions PANSS subscale and a positive correlation between the fALFF Slow-5 and P3 Hallucination PANSS subscale for AVH/D+ only. These effects were not a consequence of structural differences between groups, as morphometric analysis did not evidence any group differences. Given the role of language as an emerging property resulting from the integration of many high-level cognitive processes and the underlying cortical areas, our results suggest that LN features from fMRI connectivity and fluctuations can be a marker of neurophysiological features characterizing SZ patients depending on their vulnerability to hallucinate
Planum temporale, planum parietale and dichotic listening in dyslexia
No full textA reduction or reversal of the normal leftward asymmetry of the planum temporale (PT) has been claimed to be typical of dyslexia, although some recent studies have challenged this view. In a population-based study of 20 right-handed dyslexic boys and 20 matched controls, we have measured the PT and the adjacent planum parietale (PP) region in sagittal magnetic resonance images. For the PT, mean left and right areas and asymmetry coefficients were compared. Since a PP area often could not be identified in one or both hemispheres, a qualitative comparison was used for this region. The total planar area (sum of PT and PP) was also compared between the two groups. A dichotic listening (DL) test with consonant–vowel syllables was administered to assess functional asymmetry of language. The results showed a mean leftward PT asymmetry in both the dyslexic and the control group, with no significant difference for the degree of PT asymmetry. Planned comparisons revealed however, a trend towards smaller left PT in the dyslexic group. In control children, but not in the dyslexic children, a significant correlation between PT asymmetry and reading was observed. A mean leftward asymmetry was also found for the total planar area, with no difference between the groups for the degree of asymmetry. Significantly fewer dyslexic children than control children showed a rightward asymmetry for the PP region. Both groups showed a normal right ear advantage on the DL task, with no significant difference for DL asymmetry. No significant correlation was observed between PT asymmetry and DL asymmetry. The present population-based study adds to recent reports of normal PT asymmetry in dyslexia, but indicates that subtle morphological abnormalities in the left planar area may be present in this condition
Left temporal lobe structural and functional abnormality underlying auditory hallucinations in schizophrenia
No full textIn this article, we have reviewed recent findings from our laboratory, originally presented in Hugdahl et al. (2008) . These findings reveal that auditory hallucinations in schizophrenia should best be conceptualized as internally generated speech mis-representations lateralized to the left superior temporal gyrus and sulcus, not cognitively suppressed due to enhanced attention to the ‘voices’ and failure of fronto-parietal executive control functions. An overview of diagnostic questionnaires for scoring of symptoms is presented together with a review of behavioral, structural, and functional MRI data. Functional imaging data have either shown increased or decreased activation depending on whether patients have been presented an external stimulus during scanning. Structural imaging data have shown reduction of grey matter density and volume in the same areas in the temporal lobe. We have proposed a model for the understanding of auditory hallucinations that trace the origin of auditory hallucinations to neuronal abnormality in the speech areas in the left temporal lobe, which is not suppressed by volitional cognitive control processes, due to dysfunctional fronto-parietal executive cortical networks
Asymmetry of White Matter Pathways
No full text"Here are eight instances in which the lesion was in the posterior third of the third frontal convolution. This number seems to me to be sufficient to give strong presumptions. And the most remarkable thing is that in all the patients the lesion was on the left side. I do not dare draw conclusions from this."—Paul Broca (1863)With these words, from a short report of a series of patients with acquired speech deficits, begins the modern period of the study of cerebral asymmetry. Despite Broca’s reticence to draw any conclusion from his clinical–anatomical observation, his words clearly allude to a concept that has stood the test of time: the asymmetrical distribution of functions in the human brain. In later writings, Broca not only vehemently defended his idea of left lateralization of speech but initiated the discussion on the anatomical correlates of cerebral dominance (Finger, 1994). This became an intensely growing field of research where anatomists focused their attention on either macroscopic (e.g., volume of gyri) or microscopic (e.g., cytoarchitectonic) differences between the two hemispheres. However, a handful of researchers faithful to their belief on the importance of brain connections have tried to explain cerebral dominance in terms of of white matter asymmetry. Their efforts have often been limited to mere speculation, for the availability of reliable methods to trace connections in the human brain have been lacking for decades. Recent developments in magnetic resonance imaging (MRI) have introduced new methods, based on diffusion imaging tractography that can reconstruct white matter trajectories in the living human brain (Basser et al., 2000; Le Bihan, 2003). The resultant influx of information on human connectional anatomy derived from tractography is likely to fill the gap on our anatomical knowledge of human brain connections and reinvigorate models of cognition based on asymmetrical distribution of large-scale networks (Catani & Mesulam, 2008).An overview of the hodological (pathway-based) approach to cerebral dominance and its historical context, with a special focus on the perisylvian networks, constitutes the subject matter of this chapter. We first focus on the nineteenth-century postmortem studies of white matter tracts and the models of brain function and cerebral dominance based on those anatomical findings. We then survey twentieth-century studies derived from blunt dissections and neuroimaging and highlight their advantages and limitations. Finally, we present preliminary contributions from diffusion imaging tractography to the anatomy of the perisylvian networks, its heterogeneity in the normal population, and possible functional and behavioral correlates of different patterns of lateralization. Other tracts such as the uncinate, the cingulum, and the corticospinal and cerebellar tracts will also be discussed. One outcome of this review will be to underline the merits of the hodological approach to cerebral dominance and its modern pursuit with diffusion imaging tractography
Visual-spatial information processing in the two hemispheres of the brain is dependent on the feature characteristics of the stimulus
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