Biology subjects

Rice, G. E.

Publications and source records attributed to Rice, G. E..

3 recordsLinked to original sources

bioRxiv2022

Systematic evaluation of high level visual deficits and lesions in posterior cerebral artery stroke

Knowledge about the consequences of stroke on high level vision comes primarily from single case studies of patients selected based on their behavioural profiles with deficits in the recognition of a specific visual category such as faces or words. There are, however, no systematic, detailed, large-scale evaluations of the more typical clinical behavioural and lesion profiles of impairments in high level vision that may follow posterior cerebral artery (PCA) stroke. These goals were met by the current study through the data collected in the Back of the Brain (BoB) project: to date, the largest (N=64) and most detailed examination of patients with cortical PCA strokes selected based on lesion location rather than behavioural symptoms. We present here two complementary analyses of the structural neuroimaging data and key indices of behavioural performance with the visual processing words, objects and faces: (1) a multivariate multiple regression analysis to establish the relationships between lesion volume, lesion laterality or the presence of a bilateral lesion with performance on words, objects and faces; and, (2) a voxel-based correlational method (VBCM) analysis to establish whether there are distinct or separate regions within the PCA territory that underpin the visual processing of these categories. In contrast to the characterization of specific stroke syndromes like pure alexia or prosopagnosia in the literature, most patients in our cohort showed more general deficits in high level vision (n=22) or no deficits at all (n=21). Category-selective deficits were rare (n=6), and were only found for words, which, interestingly could follow left or right hemisphere lesions. The lesion analyses mainly confirmed the pattern reported in more selective cases: word recognition impairments are associated with a left-sided pattern of damage and face recognition deficits with a bilateral albeit right-dominant lesion pattern. Importantly, however, both general and more selective impairment may follow from left or right unilateral as well as bilateral lesions. While the findings provide partial support for the relative laterality of posterior brain regions supporting reading in the left and, to a lesser extent, face processing in the right hemisphere, the results suggest that both hemispheres are involved in the visual processing of faces, words and objects. This has ramifications for researchers studying the healthy brain and for clinicians working with patients with PCA stroke. Clinicians are recommended to carry out formal assessment of face, word and object recognition as most patients are expected to present with a mixed picture of deficits.

neuroscience↗

bioRxiv2021

The Coherent Default Mode Network is not involved in Episodic Recall or Social Cognition

Resting-state network research is extremely influential, yet the functions of many networks remain unknown. In part, this is due to typical (e.g., univariate) analyses testing the function of individual regions and not the full set of co-activated regions that form a network. Connectivity is dynamic and the function of a region may change based on its current connections. Therefore, determining the function of a network requires assessment at the network-level. Yet popular theories implicating the default mode network (DMN) in episodic memory and social cognition, rest principally upon analyses performed at the level of individual brain regions. Here we use independent component analysis to formally test the role of the DMN in episodic and social processing at the network level. As well as an episodic retrieval task, two independent datasets were employed to assess DMN function across the breadth of social cognition; a person knowledge judgement and a theory of mind task. Each task dataset was separated into networks of co-activated regions. In each, the co-activated DMN, was identified through comparison to an a priori template and its relation to the task model assessed. This co-activated DMN did not show greater activity in episodic or social tasks than high-level baseline conditions. Thus, no evidence was found to support hypotheses that the co-activated DMN is involved in explicit episodic or social processing tasks at a network-level. The networks associated with these processes are described. Implications for prior univariate findings and the functional significance of the co-activated DMN are considered.

neuroscience↗

bioRxiv2020

Individual Differences in the Connectivity of Left and Right Anterior Temporal Lobes Relate to Modality and Category Effects in Semantic Categorisation

Contemporary neuroscientific accounts suggest that ventral anterior temporal lobe (ATL) regions act as a bilateral heteromodal semantic hub. However, research also shows graded functional differences between the hemispheres relating to linguistic versus non-linguistic semantic tasks and to knowledge of objects versus people. Individual differences in connectivity from bilateral ATL and between left and right ATL might therefore give rise to differences in function within this system. We investigated whether the relative strength of intrinsic connectivity from left and right ATL would relate to differences in performance on semantic tasks. We examined resting-state fMRI in 74 individuals and, in a separate session, examined semantic categorisation, manipulating stimulus type (famous faces versus landmarks) and modality of presentation (visual versus verbal). We found that people with greater connectivity between left and right ATL were more efficient at categorising landmarks, especially when these were presented visually. In addition, participants who showed stronger connectivity from right than left ATL to medial occipital cortex showed more efficient semantic categorisation of landmarks regardless of modality of presentation. These findings show that individual differences in the intrinsic connectivity of left and right ATL are associated with effects of category and modality in semantic categorisation. The results can be interpreted in terms of graded differences in the strengths of inputs from spoke regions, such as regions of visual cortex, to a bilateral yet partially segregated semantic hub, encompassing left and right ATL.

neuroscience↗