Effects of the lexical-semantic variables in visual word recognition

In languages with a deep orthography such as English, a number of studies have shown the effects of lexical and semantic variables on word recognition. In languages with a shallow orthography such as Spanish the regularity of the grapheme - phoneme correspondences may mean that lexical and semantic variables could have less relevant roles. In this study, three variables were tested: frequency, age of acquisition and imageability. These three variables were factorially manipulated in three lexical decision task and three word naming tasks. The results show that in lexical decision both frequency and age of acquisition influence reaction times but imageability was not significant. In the word reading task, only the age of acquisition had a significant effect. The implications of these results for models of reading in Spanish are discussed.     

Effects of language comprehension on visual processing - MEG dissociates early perceptual and late N400 effects

We investigated whether and when information conveyed by spoken language impacts on the processing of visually presented objects. In contrast to traditional views, grounded-cognition posits direct links between language comprehension and perceptual processing. We used a magnetoencephalographic cross-modal priming paradigm to disentangle these views. In a sentence-picture verification task, pictures (e.g. of a flying duck) were paired with three sentence conditions: A feature-matching sentence about a duck in the air, a feature-mismatching sentence about a duck in a lake, and an unrelated sentence. Brain responses to pictures showed enhanced activity in the N400 time-window for the unrelated compared to both related conditions in the left temporal lobe. The M1 time-window revealed more activation for the feature-matching than for the other two conditions in the occipital cortex. These dissociable effects on early visual processing and semantic integration support models in which language comprehension engages two complementary systems, a perceptual and an abstract one.     

Spatial working memory effects in early visual cortex

The present study investigated how spatial working memory recruits early visual cortex. Participants were required to maintain a location in working memory while changes in blood oxygen level dependent (BOLD) signals were measured during the retention interval in which no visual stimulation was present. We show working memory effects during the retention period in early visual cortex which were retinotopically organized in the sense that evoked BOLD responses were specific to the position of the remembered location on an imaginary clock. We demonstrate that this activity is similar to activity observed in conditions in which participants have to direct spatial attention to the same location. We suggest that during the retention interval modulation of neurons coding the remembered location evoke a baseline shift, providing converging evidence for the notion that spatial working memory may use spatial attention as a rehearsal mechanism.     

Age of acquisition effects in picture naming: evidence for a lexical-semantic competition hypothesis

In many tasks the effects of frequency and age of acquisition (AoA) on reaction latencies are similar in size. However, in picture naming the AoA-effect is often significantly larger than expected on the basis of the frequency-effect. Previous explanations of this frequency-independent AoA-effect have attributed it to the organisation of the semantic system or to the way phonological word forms are stored in the mental lexicon. Using a semantic blocking paradigm, we show that semantic context effects on naming latencies are more pronounced for late-acquired than for early-acquired words. This interaction between AoA and naming context is likely to arise during lexical-semantic encoding, which we put forward as the locus for the frequency-independent AoA-effect.     

Priming effects on the N400 in the affective priming paradigm with facial expressions of emotion

We studied the effect of facial expression primes on the evaluation of target words through a variant of the affective priming paradigm. In order to make the affective valence of the faces irrelevant to the task, the participants were assigned a double prime–target task in which they were unpredictably asked either to identify the gender of the face or to evaluate whether the word was pleasant or unpleasant. Behavioral and electrophysiological (event-related potential, or ERP) indices of affective priming were analyzed. Temporal and spatial versions of principal components analyses were used to detect and quantify those ERP components associated with affective priming. Although no significant behavioral priming was observed, electrophysiological indices showed a reverse priming effect, in the sense that the amplitude of the N400 was higher in response to congruent than to incongruent negative words. Moreover, a late positive potential (LPP), peaking around 700 ms, was sensitive to affective valence but not to prime–target congruency. This pattern of results is consistent with previous accounts of ERP effects in the affective priming paradigm that have linked the LPP with evaluative priming and the N400 with semantic priming. Our proposed explanation of the N400 priming effects obtained in the present study is based on two assumptions: a double check of affective stimuli in terms of valence and specific emotion content, and the differential specificities of facial expressions of positive and negative emotions.     

Automatic semantic activation is no myth: semantic context effects on the N400 in the letter-search task in the absence of response time effects

The claim that semantic activation is an automatic process was recently called a myth, on the basis of the finding that if letter search is performed on a prime word, semantic priming effects on response time are eliminated, whereas repetition effects are preserved. The absence of semantic activation, however, cannot be validly inferred from the lack of response time effects, and converging evidence is needed. To this end, we examined the event-related potential correlate of priming, the N400 amplitude modulation, in a letter-search priming paradigm. Our experiment replicated the response time effects and demonstrated that the N400 amplitude successfully differentiates cross-case repetition priming, semantic priming, and neutral conditions. The results clearly indicate that the meaning of the prime word was processed and that semantic activation indeed was present in the letter-search task. The notion that semantic activation is an automatic process should not be abandoned prematurely.     

Font effects of Chinese characters and pseudo-characters on the N400: evidence for an orthographic processing view

Event-related brain potentials (ERPs) were recorded during a Chinese character decision task to examine whether N400 amplitude is modulated by stimulus font. Results revealed large negative-going ERPs in an N400 time window of 300-500ms to stimuli presented in degraded Xing Kai Ti (XKT) font compared with more intact Song Ti (ST) font regardless of whether the stimuli were real or pseudo-characters. ERPs for the pseudo-characters were more negative than for the real characters with similar timing and scalp distribution. The N400-like font effect on amplitude is interpreted as analogous to an N400 stimulus degradation effect, an extension to Holcomb (1993); the degraded perceptual cues provided by XKT supposedly account for this degradation effect. This effect is further interpreted to reflect relative difficulty, which results from orthographic processing difficulty, in retrieving the meaning of XKT stimuli compared with ST stimuli.     

ERPs and morphological processing: the N400 and semantic composition

Both behavioral and electrophysiological evidence suggests that fluent readers decompose morphologically complex words into their constituent parts. Previous event-related potential (ERP) research has been equivocal with regard to whether the N400 component indexes morphological decomposition or the integration of the products of decomposition, a process called semantic composition. In a visual lexical decision task with college students, we recorded ERPs to a well-controlled set of words and nonwords made up of bound morphemes (discern, predict; disject, percern) or free morphemes (cobweb, earring; cobline, bobweb) and monomorphemic control words and nonwords (garlic, minnow; gartus, buzlic). For each of the three morphological types, participants were faster to respond to words than to nonwords. Furthermore, for each of the three morphological types, the amplitude of the N400 was more negative to nonwords than to matched words, an effect indicating that the N400 is more sensitive to the lexicality of the whole stimulus than to the meaningfulness of the constituent parts of the stimulus. The N400 lexicality effect was not significantly different across the three morphological types. To our knowledge, this is the first ERP study to directly compare the processing of printed sets of words composed of bound and free morphemes and monomorphemic control stimuli in order to explore the relative sensitivity of the N400 to morphological decomposition (i.e., the status of the parts) and semantic composition (i.e., the status of the whole). Our findings are consistent with an interpretation of the N400 as an index of a process of semantic composition.     

Subcortical mechanisms in language: lexical-semantic mechanisms and the thalamus.

Four previously published cases of dominant thalamic lesion in which the author has participated are reviewed to gain a better understanding of thalamic participation in lexical-semantic functions. Naming deficits in two cases support Nadeau and Crosson's (1997) hypothesis of a selective engagement mechanism involving the frontal lobes, inferior thalamic peduncle, nucleus reticularis, and other thalamic nuclei, possibly the centromedian nucleus. This mechanism selectively engages those cortical areas required to perform a cognitive task, while maintaining other areas in a state of relative disengagement. Deficits in selective engagement disproportionately affect lexical retrieval based on semantic input, as opposed to lexical and sublexical processes, because the former is more dependent upon this attentional system. The concept of selective engagement is also useful in understanding thalamic participation in working memory, as supported by data from one recent functional neuroimaging study. Other processes also may be compromised in more posterior thalamic lesions which damage the pulvinar but not other components of this selective engagement system. A third case with aphasia after a more superior and posterior thalamic lesion also had oral reading errors similar to those in neglect dyslexia. The pattern of deficits suggested a visual processing problem in the early stages of reading. The fourth case had a category-specific naming deficit after posterior thalamic lesion. Taken together, the latter two cases indicate that the nature of language functions in more posterior regions of the dominant thalamus depends upon the cortical connectivity of the thalamic region. Together, findings from the four cases suggest that thalamic nuclei and systems are involved in multiple processes which directly or indirectly support cortical language functions.     

Sensitivity to syntax in visual cortex

One of the most intriguing findings on language comprehension is that violations of syntactic predictions can affect event-related potentials as early as 120 ms, in the same time-window as early sensory processing. This effect, the so-called early left-anterior negativity (ELAN), has been argued to reflect word category access and initial syntactic structure building (Friederici, 2002). In two experiments, we used magnetoencephalography to investigate whether (a) rapid word category identification relies on overt category-marking closed-class morphemes and (b) whether violations of word category predictions affect modality-specific sensory responses. Participants read sentences containing violations of word category predictions. Unexpected items varied in whether or not their word category was marked by an overt function morpheme. In Experiment 1, the amplitude of the visual evoked M100 component was increased for unexpected items, but only when word category was overtly marked by a function morpheme. Dipole modeling localized the generator of this effect to the occipital cortex. Experiment 2 replicated the main results of Experiment 1 and eliminated two non-morphology-related explanations of the M100 contrast we observed between targets containing overt category-marking and targets that lacked such morphology. Our results show that during reading, syntactically relevant cues in the input can affect activity in occipital regions at around 125 ms, a finding that may shed new light on the remarkable rapidity of language processing.     

Reduced N400 semantic priming effects in adult survivors of paediatric and adolescent traumatic brain injury

The immediate and long-term neural correlates of linguistic processing deficits reported following paediatric and adolescent traumatic brain injury (TBI) are poorly understood. Therefore, the current research investigated event-related potentials (ERPs) elicited during a semantic picture-word priming experiment in two groups of highly functioning individuals matched for various demographic variables and behavioural language performance. Participants in the TBI group had a recorded history of paediatric or adolescent TBI involving injury mechanisms associated with diffuse white matter pathology, while participants in the control group never sustained any insult to the brain. A comparison of N400 Mean Amplitudes elicited during three experimental conditions with varying semantic relatedness between the prime and target stimuli (congruent, semantically related, unrelated) revealed a significantly smaller N400 response in the unrelated condition in the TBI group, indicating residual linguistic processing deviations when processing demands required the quick detection of a between-category (unrelated) violation of semantic expectancy.     

Emotional facilitation of sensory processing in the visual cortex

A key function of emotion is the preparation for action. However, organization of successful behavioral strategies depends on efficient stimulus encoding. The present study tested the hypothesis that perceptual encoding in the visual cortex is modulated by the emotional significance of visual stimuli. Event-related brain potentials were measured while subjects viewed pleasant, neutral, and unpleasant pictures. Early selective encoding of pleasant and unpleasant images was associated with a posterior negativity, indicating primary sources of activation in the visual cortex. The study also replicated previous findings in that affective cues also elicited enlarged late positive potentials, indexing increased stimulus relevance at higher-order stages of stimulus processing. These results support the hypothesis that sensory encoding of affective stimuli is facilitated implicitly by natural selective attention. Thus, the affect system not only modulates motor output (i.e., favoring approach or avoidance dispositions), but already operates at an early level of sensory encoding.     

Incidental picture exposure affects later reading: evidence from the N400

Language comprehenders form a mental representation of the implied shape of objects mentioned in the text. In the present study, the influence of prior visual experience on subsequent reading was assessed. In two separate phases, participants saw a picture of an object and read a text about the object, suggesting the same or a different shape. When the shapes in the two phases mismatched, ERPs during reading showed a larger N400 amplitude than when the shapes matched, suggesting that a picture presented incidentally 15 min earlier affected reading. These results further strengthen the case for the interaction of language and visual experience during language comprehension.     

Pragmatic skills predict online counterfactual comprehension: Evidence from the N400

Counterfactual thought allows people to consider alternative worlds they know to be false. Communicating these thoughts through language poses a social-communicative challenge because listeners typically expect a speaker to produce true utterances, but counterfactuals per definition convey information that is false. Listeners must therefore incorporate overt linguistic cues (subjunctive mood, such as in If I loved you then) in a rapid way to infer the intended counterfactual meaning. The present EEG study focused on the comprehension of such counterfactual antecedents and investigated if pragmatic ability—the ability to apply knowledge of the social-communicative use of language in daily life—predicts the online generation of counterfactual worlds. This yielded two novel findings: (1) Words that are consistent with factual knowledge incur a semantic processing cost, as reflected in larger N400 amplitude, in counterfactual antecedents compared to hypothetical antecedents (If sweets were/are made of sugar). We take this to suggest that counterfactuality is quickly incorporated during language comprehension and reduces online expectations based on factual knowledge. (2) Individual scores on the Autism Quotient Communication subscale modulated this effect, suggesting that individuals who are better at understanding the communicative intentions of other people are more likely to reduce knowledge-based expectations in counterfactuals. These results are the first demonstration of the real-time pragmatic processes involved in creating possible worlds.     

Perceptual capacity of the isolated visual cortex in the cat

The split-brain approach was utilized in 6 cats to test the degree of functional autonomy in the visual system. The central visual cortex of one hemisphere was isolated by the removal of most of the extravisual neocortex of the same hemisphere. Visual inflow was restricted to the isolated side in four cases by sectioning the crossed optic fibres at the chiasma and masking one eye and in two cases by section of the contralateral optic tract. The isolation produced severe deficits in visual performance, although all cases retained some ability to learn and to recall simple pattern discriminations. The results of two- and three-stage removals of the non-visual cortex, and of terminal section of the callosum, as well as histology of the lateral geniculate nucleus indicated that geniculo-striate damage was not the limiting factor. Removal of fronto-parietal cortex produced as much or more decrement in visual discrimination than did removal of temporal cortex.     

From retinotopy to recognition: fMRI in human visual cortex

Recent advances in functional magnetic resonance imaging (fMRI) have furnished increasingly informative and accurate maps of the retinotopy and functional organization in human visual cortex. Here we review how information in those sensory-based maps is topographically related to, and influenced by, more cognitive visuo-spatial dimensions, such as mental imagery, spatial attention, repetition effects and size perception.     

网络语言的创造性加工过程:新颖N400与LPC

采用事件相关电位(ERP)技术比较在语义违反范式下网络语言和标准汉语的语义加工差异。结果发现:(1)不管是网络语言还是标准汉语,相对于语义一致条件,语义不一致条件在400 ms诱发了一个更负的负成分,但网络语言的经典N400差异波具有更晚的潜伏期和更长的持续时间;(2)溯源结果发现,网络语言和标准汉语的经典N400差异波的早期和晚期的定位均分别定位于丘脑和前扣带回,表明N400延迟效应是由个体对网络语言相对低的流利度所致,反映了认知冲突的延续;(3)在语义一致性条件下,网络语言比标准汉语诱发了一个更负的新颖N400和一个更正的晚期正成分(LPC),分别定位于前扣带回和海马,二者分别反映了新颖网络含义的识别以及新颖语义信息的整合与新颖语义联结的形成。ERP结果支持了网络语言加工属于创造性思维过程。     

Reconstructing the recent visual past: Hierarchical knowledge-based effects in visual working memory

This paper presents two experiments that examine the influence of multiple levels of knowledge on visual working memory (VWM). Experiment 1 focused on memory for faces. Faces were selected from continua that were constructed by morphing two face photographs in 100 steps; half of the continua morphed a famous face into an unfamiliar one, while the other half used two unfamiliar faces. Participants studied six sequentially presented faces each from a different continuum, and at test they had to locate one of these within its continuum. Experiment 2 examined immediate memory for object sizes. On each trial, six images were shown; these were either all vegetables or all random shapes. Immediately after each list, one item was presented again, in a new random size, and participants reproduced its studied size. Results suggested that two levels of knowledge influenced VWM. First, there was an overall central-tendency bias whereby items were remembered as being closer to the overall average or central tokens (averaged across items and trials) than they actually were. Second, when object knowledge was available for the to-be-remembered items (i.e., famous face or typical size of a vegetable) a further bias was introduced in responses. The results extend the findings of Hemmer and Steyvers (Psychonomic Bulletin & Review, 16, 80–87, 2009a) from episodic memory to VWM and contribute to the growing literature which illustrates the complexity and flexibility of the representations subtending VWM performance (e.g., Bae, Olkkonen, Allred, & Flombaum, Journal of Experimental Psychology: General, 144(4):744–63, 2015).