Does hand proximity enhance letter identification?

Adam et al. (2012) found that letters were identified more accurately when presented near, compared to away from, the hands. Participants performed the task in two conditions: with their hands held stationary and with their hands moving towards and away from the target letters. The near-hands effect included the contribution of both static and dynamic trials. Further studies showed that accuracy in letter discrimination was higher when hands were away from a target (a far-hands effect) and moving toward it, suggesting an interaction between hand position and movement direction. The present study aimed to test whether hand proximity affects letter identification when the hands are stationary, as it remains unclear if this effect can be reliably observed. Participants viewed strings of three consonants, briefly presented and masked, and had to verbally report their identity. Stimuli were presented under two different hand conditions: proximal and distal. The predicted effects of letter position and stimulus duration were all statistically significant and robust; however, we did not observe a hand proximity effect.

Objects with motor valence affect the visual processing of human body parts: Evidence from behavioural and ERP studies.

Recent findings indicate that the mental representation of an object contains crucial information about the motor interactions relevant for its intended functional use, suggesting a possible action-specific link with body effectors. For example, in the visual system, the extrastriate body area (EBA) responds to full body and body part images according to a functional/semantic organizational principle. However, the pliancy of the relationship between objects and body parts remains under-investigated. The present study aims to i) investigate this relationship more directly by assessing whether recognition of specific body parts can be facilitated by a brief exposure to functionally-related objects (Experiment 1) and ii) whether the functional relationship between objects and body parts modulates a posterior body-sensitive ERP waveform, peaking around 200 msec, and the more centro-parietal P300, linked to item categorization processes and visual awareness (Experiment 2). Participants were asked to quickly recognize targets (pictures of hands or feet) preceded by a functionally related (e.g., drum for hand target), unrelated (e.g., drum for foot target), or neutral (e.g., unknown object for both targets) prime. Findings showed that participants' performance was significantly more accurate with related than unrelated primes and that ERP amplitudes were modulated by the relationship between the prime and the target. These findings confirm the existence of action-specific links between objects and body parts and expand on recent findings on categorical organization of neural responses to human effectors in the visual system.

Is semantic processing impaired near the hands?

In a sentence decision task, Davoli et al. (2010) found that the semantic analysis of sentences differed depending on whether the participants' hands were close to or far from the computer screen. According to the authors, the findings reflected an impoverishment of semantic processing near the hands. In the current study, we examine this explanation by asking whether hand position affects 1) other aspects of sentence processing, such as syntactic analysis, 2) semantic processing at the individual word level, and 3) performance in a picture naming task that requires access to meaning. In Experiment 1, participants judged the acceptability of sentences, half of which included semantic or syntactic violations. In Experiment 2, only semantically acceptable or nonacceptable sentences were presented. In Experiment 3, participants performed a go/nogo semantic categorization task on individual words. In Experiment 4, participants performed a picture naming task. Participants performed these tasks both with their hands near to and far from the computer screen. Regardless of the task, we found no evidence of impoverished semantic processing near the hands.

Electrophysiological cross-language neighborhood density effects in late and early english-welsh bilinguals.

Behavioral studies with proficient late bilinguals have revealed the existence of orthographic neighborhood density (ND) effects across languages when participants read either in their first (L1) or second (L2) language. Words with many cross-language (CL) neighbors have been found to elicit more negative event-related potentials (ERPs) than words with few CL neighbors (Midgley et al., 2008); the effect started earlier, and was larger, for L2 words. Here, 14 late and 14 early English-Welsh bilinguals performed a semantic categorization task on English and Welsh words presented in separate blocks. The pattern of CL activation was different for the two groups of bilinguals. In late bilinguals, words with high CLND elicited more negative ERP amplitudes than words with low CLND starting around 175 ms after word onset and lasting until 500 ms. This effect interacted with language in the 300-500 ms time window. A more complex pattern of early effects was revealed in early bilinguals and there were no effects in the N400 window. These results suggest that CL activation of orthographic neighbors is highly sensitive to the bilinguals' learning experience of the two languages.

Posterior N1 asymmetry to English and Welsh words in Early and Late English-Welsh bilinguals.

We investigated the lateralization of the posterior event-related potential (ERP) component N1 (120-170 ms) to written words in two groups of bilinguals. Fourteen Early English-Welsh bilinguals and 14 late learners of Welsh performed a semantic categorization task on separate blocks of English and Welsh words. In both groups, the N1 was strongly lateralized over the left posterior sites for both languages. A robust correlation was found between N1 asymmetry for English and N1 asymmetry for Welsh words in both groups. Furthermore, in Late Bilinguals, the N1 asymmetry for Welsh words increased with years of experience in Welsh. These data suggest that, in Late Bilinguals, the lateralization of neural circuits involved in written word recognition for the second language is associated to the organization for the first language, and that increased experience with the second language is associated to a larger functional cerebral asymmetry in favor of the left hemisphere.

Brain systems mediating semantic and syntactic processing in deaf native signers: biological invariance and modality specificity.

Studies of written and spoken language suggest that nonidentical brain networks support semantic and syntactic processing. Event-related brain potential (ERP) studies of spoken and written languages show that semantic anomalies elicit a posterior bilateral N400, whereas syntactic anomalies elicit a left anterior negativity, followed by a broadly distributed late positivity. The present study assessed whether these ERP indicators index the activity of language systems specific for the processing of aural-oral language or if they index neural systems underlying any natural language, including sign language. The syntax of a signed language is mediated through space. Thus the question arises of whether the comprehension of a signed language requires neural systems specific for this kind of code. Deaf native users of American Sign Language (ASL) were presented signed sentences that were either correct or that contained either a semantic or a syntactic error (1 of 2 types of verb agreement errors). ASL sentences were presented at the natural rate of signing, while the electroencephalogram was recorded. As predicted on the basis of earlier studies, an N400 was elicited by semantic violations. In addition, signed syntactic violations elicited an early frontal negativity and a later posterior positivity. Crucially, the distribution of the anterior negativity varied as a function of the type of syntactic violation, suggesting a unique involvement of spatial processing in signed syntax. Together, these findings suggest that biological constraints and experience shape the development of neural systems important for language.

Relatedness proportion effects on masked associative priming: an ERP study.

Abstract The effect of relatedness proportion (the percentage of related words in a list) on associative priming was investigated in two masked priming experiments. In Experiment 1, subjects were randomly assigned to either a high (80%) or low (20%) relatedness proportion condition and performed a lexical decision task. Semantically related and unrelated primes were briefly flashed (50 ms) before the targets and were preceded by a mask that prevented their overt identification. In Experiment 2, subjects were tested in both relatedness proportion conditions in a categorization task; the N400, an electrophysiological index of lexical and semantic priming, was measured in trials that did not require a button press. Behavioral and electrophysiological priming effects were observed in both high and low relatedness proportion conditions. The observed priming effects were not modulated by relatedness proportion. The results are discussed in terms of current theories of associative priming.

Motion and color processing in school-age children and adults: an ERP study.

Stimuli designed to selectively elicit motion or color processing were used in a developmental event-related potential study with adults and children aged 6, 7 and 8. A positivity at posterior site INZ (P-INZ) was greater to motion stimuli only in adults. The P1 and N1 were larger to color stimuli in both adults and children, but earlier to motion stimuli only in adults. Finally, the P2 was larger to color stimuli in adults but larger to motion stimuli in children, and earlier to motion stimuli only in children. The findings across components indicate development from middle childhood to adulthood in aspects of both the motion and color processing systems indexed by this paradigm, but are consistent with an hypothesis of a more protracted time course of development for the motion as compared to the color processing system.

Automatic word form processing in masked priming: an ERP study.

Five prime types (unrelated words, pronounceable nonwords, illegal strings of letters, false fonts, or neutral strings of Xs) preceded word and nonword targets in a masked priming study designed to investigate word form processing as indexed by event-related potentials (ERPs). Participants performed a lexical decision task on targets. In the 150-250-ms epoch at fronto-central, central, and temporo-parietal sites ERPs were smallest to targets preceded by words and nonwords, followed by letter strings, false fonts, and finally neutral primes. This refractory pattern sensitive to orthography supports the view that ERPs in the 150-250-ms epoch index activation of neural systems involved in word form processing and suggests that such activation may be graded, being maximal with word-like stimuli and relatively reduced with alphabet-like stimuli. Further, these results from a masked priming paradigm confirm the automatic nature of word form processing.

ERP nonword rhyming effects in children and adults.

In a simple prime-target auditory rhyming event-related potential (ERP) paradigm with adults and 6-, 7-, and 8-year-old children, nonword stimuli (e.g., nin-rin, ked-voo) were used to investigate neurocognitive systems involved in rhyming and their development across the early school years. Even absent semantic content, the typical CNV to primes and late rhyming effect (RE) to targets were evident in all age groups. The RE consisted of a more negative response to nonrhyming targets as compared to rhyming targets over posterior sites, with a reversal of this pattern at lateral anterior sites. The hypothesis that the CNV indexes phonological memory processes was not well supported by correlation analyses conducted with the ERP measures and scores on standardized behavioral tests. However, the onset of the rhyming effect was later in those scoring lower on phonological awareness measures.

Representation of change: separate electrophysiological markers of attention, awareness, and implicit processing.

Awareness of change within a visual scene only occurs in the presence of focused attention. When two versions of a complex scene are presented in alternating sequence separated by a blank mask, unattended changes usually remain undetected, although they may be represented implicitly. To test whether awareness of change and focused attention had the same or separable neurophysiological substrates, and to search for the neural substrates of implicit representation of change, we recorded event-related brain potentials (ERPs) during a change blindness task. Relative to active search, focusing attention in the absence of a change enhanced an ERP component over frontal sites around 100-300 msec after stimulus onset, and in posterior sites at the 150-300 msec window. Focusing attention to the location of a change that subjects were aware of, replicated those attentional effects, but also produced a unique positive deflection in the 350-600 msec window, broadly distributed with its epicenter in mediocentral areas. The unique topography and time course of this latter modulation, together with its dependence on the aware perception of change, distinguishes this "awareness of change" electrophysiological response from the electrophysiological effects of focused attention. Finally, implicit representation of change elicited a distinct electrophysiological event: Unaware changes triggered a positive deflection at the 240-300 msec window, relative to trials with no change. Overall, the present data suggest that attention, awareness of change, and implicit representation of change may be mediated by separate underlying systems.

Visual detection is gated by attending for action: evidence from hemispatial neglect.

We report observations in patients with visual extinction demonstrating that detection of visual events is gated by attention at the level of processing at which a stimulus is selected for action. In one experiment, three patients reported the identity of numerical words and digits presented either in the ipsilesional field, the contralesional field, or both fields. On the critical bilateral trials, extinction was greater when the competing items shared the same meaning and response, regardless of whether the items were visually different (e.g., ONE + 1), or identical (e.g., 1 + 1). A fourth patient was tested in a second experiment in which the competing items on bilateral trials were either different (e.g., ONE + TWO), identical (e.g., ONE + ONE) or homophones that were visually and semantically different but shared the same response (e.g., ONE + WON). Homophones and identical items caused similar extinction with less extinction occurring on different item trials.