Temporal Integration in Visual Word Recognition

Abstract

Abstract■ When two displays are presented in close temporal succession at the same location, how does the brain assign them to one versus two conscious percepts? We investigate this issue using a novel reading paradigm in which the odd and even letters of a string are presented alternatively at a variable rate. The results reveal a window of temporal integration during reading, with a nonlinear boundary around ∼80 msec of presentation duration. Below this limit, the oscillating stimulus is easily fused into a single percept, with all characteristics of normal reading. Above this limit, reading times are severely slowed and suffer from a wordlength effect. ERPs indicate that, even at the fastest frequency, the oscillating stimulus elicits synchronous oscillations in posterior visual cortices, while late ERP components sensitive to lexical status vanish beyond the fusion threshold. Thus, the fusion/segregation dilemma is not resolved by retinal or subcortical filtering, but at cortical level by at most 300 msec. The results argue against theories of visual word recognition and letter binding that rely on temporal synchrony or other fine temporal codes. ■

Recognition of letters displayed as briefly flashed dot patterns

“…The information persistence lasted for at least 200 ms. At longer intervals the two-flash models did not drop all the way to the one-flash baseline, which could reflect the contribution of information that has been stored in working memory intervals may be quite different where the observer must synthesize across groups of complete letters in order to perceive a word. Forget et al (2010) flashed two three-letter components of a six-letter word, e.g., B_A_N_ and _R_I_S to form BRAINS. They found effective two-pulse summation that allowed recognition of the whole word out to 80 ms.…”

“…Stimulus information was integrated only under limited task conditions (Brockmole et al 2002;Jiang et al 2005). Busey (1998) provided quantitative modeling of inhibitory interactions with successive displays of digits, and Forget et al (2010) found competition in the perception of trigrams.…”

The cortical representation of simple mathematical expressions

“…During reading, the VWFA is thought to play a key role in processing all of a word's letters in a parallel rather than serial fashion (Dehaene et al, 2005;Forget et al, 2009). Expert readers show essentially constant naming times, regardless of the number of letters in a word, at least below~8 letters (Cohen et al, 2008;Lavidor and Ellis, 2002).…”

Evaluating cognitive models of visual word recognition using fMRI: Effects of lexical and sublexical variables

“…Reilhac et al, 2013) prior to their mapping to phonemes. However, the visual operation of spatial attention is distinct from GPC mapping: In the DRC model, all letters are hypothesized to be activated simultaneously (a view supported by recent behavioral and neural findings: Adelman, Marquis, & Sabatos-DeVito, 2010;Forget, Buiatti, & Dehaene, 2010).…”