From visual encoding to meaning: processing numbers, letters and pictures
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1
Basque Center on Cognition, Brain and Language, Spain
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2
Low Temperature Lab, United States
How visual strings are represented and how visual words are recognized and accessed is still under debate. Tarkiainen et al. (1999) reported larger Equivalent Current Dipole (ECD) amplitudes in left occipitotemporal cortex to words compared to symbols 140 ms after the onset. Cornelissen et al. (2003) compared ECD responses to words and consonants strings, and in a similar time-window (i.e., ~150 ms) found no reliable difference, suggesting that these early cortical visual responses reflect prelexical alphabetic character encoding. The goal of the current experiment was to investigate the underlying spatial and temporal brain dynamics of word, number and picture processing. Native speakers of Spanish (n = 14) performed a go/no-go task to visually presented words, numbers and pictures. All experimental conditions were no-go trials. The evoked neuromagnetic activity was recorded using a 306-channel whole-head Elekta MEG system. ECD waveforms were calculated based on sensor-level data. The earliest reliably elicited peak (i.e., N1) showed no differences between conditions. Dipolar activity in occipito-temporal areas ~150 ms, however, showed a maximum amplitude for words compared to numbers. Picture strings elicited the smallest ECD amplitudes. Later, between 300 and 500 ms, we found stronger amplitudes for dipoles localized to left MTG for words compared to numbers and pictures that did not differ between them. These findings support the role of the left ventral-lateral pathway as a critical network involved in expert word recognition. After an initial stage of visual feature extraction, those features are mapped onto pre-existing internal alphabetic and numeric representations stored in left occipitotemporal cortex. Funding: Supported by CONSOLIDER INGENIO2010-CSD_00048.
Keywords:
ECD waveforms,
Language
Conference:
XI International Conference on Cognitive Neuroscience (ICON XI), Palma, Mallorca, Spain, 25 Sep - 29 Sep, 2011.
Presentation Type:
Poster Presentation
Topic:
Poster Sessions: Neural Bases of Language
Citation:
Carreiras
M,
Molinaro
N,
Monahan
P,
Helenius
P and
Duñabeitia
J
(2011). From visual encoding to meaning: processing numbers, letters and pictures.
Conference Abstract:
XI International Conference on Cognitive Neuroscience (ICON XI).
doi: 10.3389/conf.fnhum.2011.207.00183
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Received:
19 Nov 2011;
Published Online:
28 Nov 2011.
*
Correspondence:
Prof. Manuel Carreiras, Basque Center on Cognition, Brain and Language, San Sebastián, Spain, m.carreiras@bcbl.eu