Attentional shifting and the role of the dorsal pathway in visual word recognition.

Full Abstract

A substantial amount of evidence has been collected to propose an exclusive role for the dorsal visual pathway in the control of guided visual search mechanisms, specifically in the preattentive direction of spatial selection [Vidyasagar, T. R. (1999). A neuronal model of attentional spotlight:
Parietal guiding the temporal. Brain Research and Reviews, 30, 66-76; Vidyasagar, T. R. (2001). From attentional gating in macaque primary visual cortex to dyslexia in humans. Progress in Brain Research, 134, 297-312]. Moreover, it has been suggested recently that the dorsal visual pathway is specifically involved in the spatial selection and sequencing required for orthographic processing in visual word recognition. In this experiment we manipulate the demands for spatial processing in a word recognition, lexical decision task by presenting target words in a normal spatial configuration, or where the constituent letters of each word are spatially shifted relative to each other. Accurate word recognition in the Shifted-words condition should demand higher spatial encoding requirements, thereby making greater demands on the dorsal visual stream. Magnetoencephalographic (MEG) neuroimaging revealed a high frequency (35-40Hz) right posterior parietal activation consistent with dorsal stream involvement occurring between 100 and 300ms post-stimulus onset, and then again at 200-400ms. Moreover, this signal was stronger in the shifted word condition, compared to the normal word condition. This result provides neurophysiological evidence that the dorsal visual stream may play an important role in visual word recognition and reading. These results further provide a plausible link between early stage theories of reading, and the magnocellular-deficit theory of dyslexia, which characterises many types of reading difficulty.

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Author information

Author/s: Pammer, Kristen (K); Hansen, Peter (P); Holliday, Ian (I); Cornelissen, Piers (P);

Affiliation: The School of Psychology, The Australian National University, Canberra, ACT 0200, Australia. Kriten.pammer(-atsign-)anu.edu.au

Journal and publication information

Publication Type: Comparative Study; Journal Article

Journal: Neuropsychologia (Neuropsychologia), published in England. (Language: eng)

Reference: 2006-; vol 44 (issue 14) : pp 2926-36

Dates: Created 2006/10/18; Completed 2006/12/12;

PMID: 16950456, status: MEDLINE (last retrieval date: 12/26/2008)

Sourced from the National Library of Medicine. Abstract text and other information may be subject to copyright.

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MeSH headings (categories)

This article was linked to the MESH Headings shown below.

Attention - physiology
Brain Mapping
Evoked Potentials - physiology
Humans
Image Processing, Computer-Assisted - methods
Magnetic Resonance Imaging - methods
Magnetoencephalography - methods

Magnetoencephalography - methods
Male
Oxygen - blood
Recognition (Psychology) - physiology
Visual Cortex - blood supply; physiology
Visual Pathways - blood supply; physiology
Vocabulary

Associated Chemicals: Oxygen (7782-44-7)

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