The recognition potential: Semantic processing or the detection of differences between stimuli?

Neural substrates of the interplay between cognitive load and emotional involvement in bilingual decision making

Prior work has reported that foreign language influences decision making by either reducing access to emotion or imposing additional cognitive demands. In this fMRI study, we employed a cross-task design to assess at the neural level whether and how the interaction between cognitive load and emotional involvement is affected by language (native L1 vs. foreign L2). Participants completed a Lexico-semantic task where in each trial they were presented with a neutrally or a negatively valenced word either in L1 or L2, either under cognitive load or not. We manipulated cognitive load by varying the difficulty of the task: to increase cognitive demands, we used traditional characters instead of simplified ones in L1 (Chinese), and words with capital letters instead of lowercase letters in L2 (English). After each trial, participants decided whether to take a risky decision in a gambling game. During the Gamling task, left amygdala and right insula were more activated after having processed a negative word under cognitive load in the Lexico-semantic task. However, this was true for L1 but not for L2. In particular, in L1, cognitive load facilitated rather than hindered access to emotion. Further suggesting that cognitive load can enhance emotional sensitivity in L1 but not in L2, we found that functional connectivity between reward-related striatum and right insula increased under cognitive load only in L1. Overall, results suggest that cognitive load in L1 can favor access to emotion and lead to impulsive decision making, whereas cognitive load in L2 can attenuate access to emotion and lead to more rational decisions.

Rapid stream stimulation can enhance the stimulus selectivity of early evoked responses to written characters but not faces

The recognition potential (RP) is an early visually evoked response (~250 ms) whose magnitude is sensitive to object recognizability and related factors. The RP is often measured when objects are embedded in a rapid stream of masking stimuli (the RSS paradigm), especially in reading research. The idea is that RSS provides greater stimulus-dependent variations in RP, compared to the corresponding variations without RSS. However, this idea has never been subject to systematic evaluation. We directly test whether RSS can enhance 2 types of RP stimulus selectivity, by measuring the RP in conditions that only differ in the presence or absence of a masking stream and in the type of stimulus shown. We measure the effect of image inversion on RP for Chinese characters (experiment 1); the effect of orthographical correctness on RP for Chinese characters (experiment 3); and as a control study, the effect of image inversion on the N170 response to faces (experiment 2). To ensure a fair comparison, the earliest negative deflections (RP/N170) measured with and without RSS should at least have similar channel ranges, and topographical distributions of both amplitude and selectivity. Our first set of results clearly supports this. Our main results clearly show an increase in stimulus-selectivity for RSS over non-RSS in both of the RP (Chinese character) experiments, but no such enhancement in the N170 (face) experiment. This provides incentive for investigations into the underlying mechanisms of selectivity enhancement. Our findings may also help to explain contradictory findings between RP/N170 studies that differ only in the use of noise masks, which is sometimes treated as trivial detail in papers that do not reference the RP/RSS literature.

The effects of gender and self-insight on early semantic processing

This event-related potential (ERP) study explored individual differences associated with gender and level of self-insight in early semantic processing. Forty-eight Chinese native speakers completed a semantic judgment task with three different categories of words: abstract neutral words (e.g., logic, effect), concrete neutral words (e.g., teapot, table), and emotion words (e.g., despair, guilt). They then assessed their levels of self-insight. Results showed that women engaged in greater processing than did men. Gender differences also manifested in the relationship between level of self-insight and word processing. For women, level of self-insight was associated with level of semantic activation for emotion words and abstract neutral words, but not for concrete neutral words. For men, level of self-insight was related to processing speed, particularly in response to abstract and concrete neutral words. These findings provide electrophysiological evidence for the effects of gender and self-insight on semantic processing and highlight the need to take into consideration subject variables in related research.

Effects of long-time reading experience on reaction time and the recognition potential

The proposition that long-time experience in reading a language gradually builds up rapidly acting neural processes that facilitate the processing of words in that language and speed them into conscious awareness was examined. Behavioral reaction time (RT) and electrophysiological responsiveness to visually displayed words and non-language images were measured in persons who differed in how much experience they had in reading English. The electrophysiological response was the recognition potential (RP). Behavioral RT and the latency of the RP to English words were both expected to depend upon how much English reading experience a person had. The short latency of the RP was expected to free it from the influence of non-perceptual factors that affect RT, such as speed/accuracy tradeoff. This expectation yielded the prediction that the behavioral and electrophysiological results would differ in a specific way. Long-time readers of English were expected to show shorter RP latency to English words than less experienced (China-educated) readers of English but no RP latency difference for non-language images, with which neither group had greater experience. In contrast, due to speed accuracy tradeoff, the China-educated subjects were expected to show longer RT for both the words and the non-language images. The prediction was confirmed. The amount of language experience that a person had showed a stronger relationship to RP latency than it did to RT. This helped to validate the use of the RP as a tool for investigating perception and demonstrated definite advantages that it has for studying acquired perceptual processes in humans.

Looking at emotional words is not the same as reading emotional words: Behavioral and neural correlates

Recent research suggests that the allocation of attentional resources to emotional content during word processing might be sensitive to task requirements. This question was investigated in two tasks with similar instructions. The stimuli were positive, negative, and neutral nouns. Participants had to identify meaningful words embedded in a stream of non-recognizable stimuli (task 1) or pseudowords (task 2). Task 1 could be successfully performed on the basis of the perceptual features whereas a lexico-semantic analysis was required in task 2. Effects were found only in task 2. Positive nouns were identified faster, with fewer errors and elicited larger amplitude in an early negativity. Also, the amplitude of a late positivity was larger for both positive and negative nouns than for neutral nouns. It is concluded that some degree of linguistic processing is needed to direct attention to the affective content during word processing.

The recognition potential reflects an intermediate level of visual representation

A well-known event-related potential (ERP) component-the recognition potential (RP) is a response to recognizable stimuli, peaking at around 200-250 ms. The aim of the present study is to put to the test the contrasting perceptual and semantic accounts of the RP, with manipulation of word meaning and presentation format of stimuli. The hypothesis was that RP latencies would be observed to increase with the difficulty of identification in presentation formats in accord with both accounts and the present study would replicate the semantic effect independently of the perceptual manipulations. The stimuli were Chinese characters and presented to native speakers. The data yielded a negative component (RP) at around 250 ms for all formats of real characters and pseudocharacters at parietooccipital electrodes. The RP for real characters was larger in normal formats than in mirror formats and the RP for pseudocharacters was greater in normal-upright format than other formats. However, a significant RP latency difference was observed between real characters and pseudocharacters. It seems that our data could not be taken as evidence for semantic processing account. We suggest that the RP is a reflection of intermediate visual representation which integrates information from various pathways and then achieve word form analysis. When word form analysis becomes difficult, the categorical feature of word form contributes to word recognition.