The neural architecture of discourse compression

Re-telling a story is thought to produce a progressive refinement in the mental representation of the discourse. A neuroanatomical substrate for this compression effect, however, has yet to be identified. We used a discourse re-listening task and functional magnetic resonance imaging (fMRI) to identify brain regions responsive to repeated discourse in twenty healthy volunteers. We found a striking difference in the pattern of activation associated with the first and subsequent presentations of the same story relative to rest. The first presentation was associated with a highly significant increase in blood oxygen level dependent (BOLD) signal in a bilateral perisylvian distribution, including auditory cortex. Listening to the same story on subsequent occasions revealed a wider network with activation extending into frontal, parietal, and subcortical structures. When the first and final presentations of the same story were directly compared, significant increments in activation were found in the middle frontal gyrus bilaterally, and the right inferior parietal lobule, suggesting that the spread of activation with re-listening reflected an active neural process over and above that required for comprehension of the text. Within the right inferior parietal region the change in BOLD signal was highly correlated with a behavioural index of discourse compression based in re-telling, providing converging evidence for the role of the right inferior parietal region in the representation of discourse. Our findings demonstrate, for the first time, the existence of a neural network underlying discourse compression, showing that parts of this network are common to re-telling and re-listening effects

Supplementary Material for: Differential Functional Connectivity Correlates of Cerebrospinal Fluid Biomarkers in Dementia of the Alzheimer's Type

<b><i>Background:</i></b> Alzheimer's disease (AD) is characterized by two cardinal pathologies, which have different topological distributions. The differential anatomical distributions of these pathologies raise the possibility that they exert differential effects on brain networks. <b><i>Objectives:</i></b> To investigate whether cerebrospinal fluid (CSF) biomarkers of the cardinal pathologies have differential relationships with functional connectivity networks in patients with dementia of the Alzheimer's type (DAT). <b><i>Methods:</i></b> Thirty-nine participants underwent CSF sampling and resting-state functional magnetic resonance imaging. Functional connectivity networks were computed for each participant. CSF biomarker levels of p-tau and amyloid-β (Aβ) were regressed onto these networks to identify subnetworks associated with each biomarker. <b><i>Results:</i></b> A subnetwork associated with tau-related pathology was identified with its hub in the right anterior entorhinal cortex. A separate subnetwork associated with Aβ with its hub in the right dorsal anterior cingulate cortex was identified. <b><i>Conclusion:</i></b> These results demonstrate the differential effects of AD biomarkers on functional connectivity networks, supporting a possible division of labour between the cardinal pathologies

Language Cortex Activation in Normal Children

Objective: To describe a protocol for use in young children and adolescents for determining language represen- tation. Methods: We performed 130 fMRI studies in 48 children and 17 adults. Verb generation (VG) and orthographic lexical retrieval (OLR) were used. The localization and lateralization of activation was rated visually. Regional voxel counts measured asymmetry and extent of activation. Results: Activation was predominantly left-lateralized (children 85%, adults 94%), and there was no difference in the localization of activation for either paradigm. Children’s typical sites of activation included mesial (96%), inferior (94%) and middle frontal (92%) gyri, the inferior (85%) and superior (65%) temporal cortex, and the cerebellum (67%). Less frequently activated sites were insular (50%) and posterior parietal (48%) cortices. Quantitative asymmetry index scores and visual inspection of laterality were concordant. Greater quantitative asymmetry for VG than OLR occurred in children. Laterality was not related to age, sex, task proficiency, or handedness. Frontal region voxel counts lower in children than adults and left sided counts correlated with task proficiency. Conclusions: Language fMRI can be performed in young children using resources available to clinical centers. The similarity in frequency of left language lateralization between children and adults suggests that language representation establishes early in development. The reduced amount of frontal region of interest activation in task-specific regions in children may reflect different levels of ability. However, the left-right distribution of activation does not appear to depend on task performance or age. These normative data provide a basis for decisions about language laterality in pediatric patients

Memory for faces and paired associates after temporal lobectomy in childhood

Findings are reported from the first examination of the Beardsworth Memory for Children's Faces Test (BMCFT) (Beardsworth & Zaidel, 1994) tested on a selected sample of 10 left (LATL) and 7 right (RATL) anterior temporal lobectomy patients an average of 7 years post surgery. No differences between LATL and RATL groups were found on immediate or delayed memory trials of the BMCFT. Verbal memory was assessed with a verbal analogue of this test, the Extended Verbal Paired Associates Test (EVPAT) specifically constructed for this study. Differences were obtained on the immediate (F = 5.17; p < .01) and delayed (F = 6.55; p < .01) memory trials of the EVPAT with LATL patients learning and retrieving fewer verbal associations than their right ATL counterparts. No differences were found on the memory decline to delayed recall scores on the EVPAT. The findings suggest that people who have left or right ATL in childhood cannot be distinguished on the basis of their immediate or delayed memory for paired faces an average of 7 years post-surgery. These results are consistent with the immediate memory performance of children 6 months post-surgery as reported by Beardsworth and Zaidel (1994), but are not consonant with the delayed memory performance of their children on this task. This indicates that left-right dissociations found in children on measures of delayed memory for faces 6 months post-surgery may represent a component of memory that is still in a state of recovery. The findings for the immediate memory trials of the EVPAT conformed to expectations and underscore the dependability of simple rote verbal memory tasks in dissociating left from right ATL 7 years post-surgery. The study addresses the issue of the recovery of immediate versus delayed memory and time of assessment post-surgery