Ron Borowsky

Visual word recognition: a multistage activation model.

Although many models of word recognition have postulated loci for the simple effects of Context, Stimulus Quality, and Word Frequency, most of them are problematic in that they do not account for the pattern of joint effects among these factors. The experiments reported here show that, among other things, Word Frequency interacts with Context but is additive with Stimulus Quality in the context of a lexical decision experiment that also produces an interaction between Stimulus Quality and Context. The pattern of joint effects among these factors is accommodated by a multistage activation model that is based on the framework proposed by Besner and Smith (1992a).

FMRI of Ventral and Dorsal Processing Streams in Basic Reading Processes: Insular Sensitivity to Phonology

SummaryMost current models of the neurophysiology of basic reading processes agree on a system involving two cortical streams: a ventral stream (occipital-temporal) used when accessing familiar words encoded in lexical memory, and a dorsal stream (occipital-parietal-frontal) used when phonetically decoding words (i.e., mapping sublexical spelling onto sounds). The models diverge, however, on the issue of whether the insular cortex is involved. The present fMRI study required participants to read aloud exception words (e.g., ‘one’, which must be read via lexical memory) and pseudohomophones (e.g., ‘wun’, which must be read via sublexical spelling to sound translation) to examine the processing streams as well as the insular cortex, and their relationship to lexical and sublexical reading processes. The present study supports the notion of independent ventral-lexical and dorsal-sublexical streams, and further suggests the insular cortex to be sensitive to phonological processing (particularly sublexical spelling-sound translation). These latter findings illuminate the nature of insular activity during reading, which must be explored further in future studies, and accounted for in models of the neurophysiology of reading.

Neural representations of visual words and objects : A functional MRI study on the modularity of reading and object processing

There have been several studies supporting the notion of a ventral-dorsal distinction in the primate cortex for visual object processing, whereby the ventral stream specializes in object identification, and the dorsal stream is engaged during object localization and interaction. There is also a growing body of evidence supporting a ventral stream that specializes in lexical (i.e., whole-word) reading, and a dorsal stream that is engaged during sub-lexical reading (i.e., phonetic decoding). Here, we consider the extent to which word-reading processes are located in regions either intersecting with, or unique from, regions that sub-serve object processing along these streams. Object identification was contrasted with lexical-based reading, and object interaction processing (i.e., deciding how to interact with an object) was contrasted with sub-lexical reading. Our results suggest that object identification and lexical-based reading are largely ventral and modular, showing mainly unique regions of activation (parahippocampal and occipital-temporal gyri function associated with object identification, and lingual, lateral occipital, and posterior inferior temporal gyri function associated with lexical-based reading) and very little shared activation (posterior inferior frontal gyrus). Object interaction processing and phonetic decoding are largely dorsal, and show both modular regions of activation (more lateralized to the dorsal-frontal right hemisphere for pseudohomophone naming, and more to the dorsal-frontal left hemisphere for the object interaction task) as well as significant shared regions of processing (precentral gyri, left inferior frontal cortex, left postcentral gyrus, left lateral occipital cortex, and superior posterior temporal gyri). Given that the perceptual experimental conditions show primarily modular and very little shared processing, whereas the analytical conditions show both substantial modular and shared processing, we discuss a reconsideration of “modularity of mind” which involves a continuum between strictly modular processing and varying degrees of shared processing, and which also depends on the nature of the tasks compared (i.e., perceptual versus analytical).

Visual word recognition across orthographies: on the interaction between context and degradation

The purpose of the present experiment was (a) to replicate the standard finding of overadditivity between context and degradation when the unrelated context consists of unrelated words, and (b) to assess Lukatela and Turveys assumption that a baseline context consisting of asterisks is functionally equivalent to a context consisting of unrelated words

fMRI of Two Measures of Phonological Processing in Visual Word Recognition: Ecological Validity Matters.

Previous functional magnetic resonance imaging (fMRI) studies have investigated the role of phonological processing by utilizing nonword rhyming decision tasks (e.g., Pugh et al., 1996). Although such tasks clearly engage phonological components of visual word recognition, it is clear that decision tasks are more cognitively involved than the simple overt naming tasks, which more closely map onto normal reading behavior. Our research aim for this study was to examine the advantages of overt naming tasks for fMRI studies of word recognition processes. Process models are presented to highlight the similarities and differences between two cognitive tasks that are used in the word recognition literature, pseudohomophone naming (e.g., pronounce BRANE) and rhyming decision (e.g., do LEAT and JEAT rhyme?). An fMRI study identified several differences in cortical activation associated with the differences observed in the process models. Specifically, the results show that the overt naming task involved the insular cortex and inferior frontal gyrus, whereas the rhyming decision task engaged the temporal-parietal regions. It is argued that future fMRI research examining the neuroanatomical components of basic visual word recognition utilize overt naming tasks.

Diagnostics of phonological lexical processing: Pseudohomophone naming advantages, disadvantages, and base-word frequency effects

Phonological lexical access has been investigated by examining both a pseudohomophone (e.g.,brane) base-word frequency effect and a pseudohomophone advantage over pronounceable nonwords (e.g.,frane) in a single mixed block of naming trials. With a new set of pseudohomophones and nonwords presented in a mixed block, we replicated the standard finding in the naming literature: no reliable base-word frequency effect, and a pseudohomophone advantage. However, for this and two of three other sets of stimuli—those of McCann and Besner (1987), Seidenberg, Petersen, MacDonald, and Plaut (1996), and Herdman, LeFevre, and Greenham (1996), respectively—reliable effects of base-word frequency on pseudohomophone naming latency were found when pseudohomophones were presented in pure blocks prior to nonwords. Three of the four stimulus sets tested produced a pseudohomophone naming disadvantage when pseudohomophones were presented prior to nonwords. When nonwords were presented first, these effects were diminished. A strategy-based scaling account of the data is argued to provide a better explanation of the data than is the criterion-homogenization theory (Lupker, Brown, & Colombo, 1997).

Modularity and Intersection of “What”, “Where” and “How” Processing of Visual Stimuli: A New Method of fMRI Localization

Summary:Research on the modularity of perceptual and cognitive processes has often pointed to a ventral-dorsal distinction in cortical pathways that depend upon the nature of the stimuli and the task. However, it is not clear whether the dorsal, occipital-parietal stream specializes in locating visual objects (i.e., a “where” stream), or taking action toward objects (i.e., a “how” stream), although there is some consensus for a ventral, occipital-temporal “what” stream that specializes in the identification of visual objects. It is also not clear to what extent word and picture processing are modular along these streams, as functional imaging maps to date have not addressed the modularity question directly. Here we present two types of functional imaging maps that directly show modularity and intersection of processing function for word and picture stimuli in tasks that require decisions about “what is”, “where is”, or “how do you interact with” a stimulus (N=6 participants). Our results reveal a middle dorsal “how” stream with some modular regions of activation that are distinct from activation during “where” processing, and that words and pictures involve several modular regions of activation along these streams.

Changes in Functional Magnetic Resonance Imaging Cortical Activation with Cross Education to an Immobilized Limb

PURPOSE The purpose of this study was to assess cortical activation associated with the cross-education effect to an immobilized limb, using functional magnetic resonance imaging. METHODS Fourteen right-handed participants were assigned to two groups. One group (n = 7) wore a cast and strength trained the free arm (CAST-TRAIN). The second group (n = 7) wore a cast and did not strength train (CAST). Casts were applied to the nondominant (left) wrist and hand. Strength training was maximal isometric handgrip contractions (right hand) 5 d·wk(-1). Peak force (handgrip dynamometer), muscle thickness (ultrasound), EMG, and cortical activation (functional magnetic resonance imaging) were assessed before and after the intervention. RESULTS CAST-TRAIN improved right handgrip strength by 10.7% (P < 0.01) with no change in muscle thickness. There was a significant group × time interaction for strength of the immobilized arm (P < 0.05). Handgrip strength of the immobilized arm of CAST-TRAIN was maintained, whereas the immobilized arm of CAST significantly decreased by 11% (P < 0.05). Muscle thickness of the immobilized arm decreased by an average of 3.3% (P < 0.05) for all participants and was not different between groups after adjusting for baseline differences. There was a significant group × time interaction for EMG activation (P < 0.05), where CAST-TRAIN showed an increasing trend and CAST showed a decreasing trend, pooled across arms. For the immobilized arm of CAST-TRAIN, there was a significant increase in contralateral motor cortex activation after training (P < 0.05). For the immobilized arm of CAST, there was no change in motor cortex activation. CONCLUSIONS Handgrip strength training of the free limb attenuated strength loss during unilateral immobilization. The maintenance of strength in the immobilized limb via the cross-education effect may be associated with increased motor cortex activation.

What Does Rapid Automatized Naming Measure? A New RAN Task Compared to Naming and Lexical Decision.

The present research investigated the relationship between Rapid Automatized Naming (RAN) performance, letter-string reading measures of sight vocabulary (SV) and phonetic decoding (PD), and lexical decision. Criterion-based naming rates were obtained from three types of RAN tasks: digits, letters, and letter sounds. Latency measures were obtained from the naming of regular words, exception words, nonwords and pseudohomophones; as well as button press and verbal lexical decision tasks. Regression analyses supported the hypotheses that RAN-Letters latency reflects SV processing in that its variance is uniquely accounted for by exception word naming latency and button press lexical decision latency, and that RAN-Letter Sounds latency best reflects PD processing in that its variance is uniquely accounted for by pseudohomophone and nonword naming latency. Findings are discussed in light of what the RAN tasks are measuring, implications involving visual word recognition models of reading, and the utility of the new RAN-Letter Sounds task with respect to diagnostic and remediation applications.

More than meets the eye : Context effects in word identification

The influence of semantic context on word identification was examined using masked target displays. Related prime words enhanced a signal detection measure of sensitivity in making lexical decisions and in determining whether a probe word matched the target word. When line drawings were used as primes, a similar benefit was obtained with the probe task. Although these results suggest that contextual information affects perceptual encoding, this conclusion is questioned on the grounds that sensitivity in these tasks may be determined by independent contributions of perceptual and contextual information. The plausibility of this view is supported by a simulation of the experiments using a connectionist model in which perceptual and semantic information make independent contributions to word identification. The model also predicts results with two other analytic methods that have been used to argue for priming effects on perceptual encoding.