N400 Amplitude Reduction Correlates with an Increase in Pupil Size

Pupil dilation is classically associated with increase in cognitive load in humans. Here, we studied the potential link between human pupil dilation and meaning integration effort as indexed by event-related brain potentials (ERPs). We recorded pupil size variation and ERPs simultaneously while participants were presented with matching or unrelated picture–word pairs. Whilst relatedness in meaning between spoken words and pictures typically modulated ERPs, pupil size was also affected quickly after picture onset. Moreover, during the time-window associated with meaning integration, greater pupil dilation correlated with less negative N400 amplitudes elicited by unrelated pictures. Since pupil dilation has been linked to activity of the locus coeruleus–norepinephrine (LC–NE) system, these findings may provide new insights into the suggested link between human high-level cognitive function and activity of the LC–NE system

Semantic priming in the motor cortex: Evidence from combined repetitive transcranial magnetic stimulation and event-related potential

Reading action verbs is associated with activity in the motor cortices involved in performing the corresponding actions. Here, we present new evidence that the motor cortex is involved in semantic processing of bodily action verbs. In contrast to previous studies, we used a direct, nonbehavioural index of semantic processing after repetitive transcranial magnetic stimulation (rTMS). Participants saw pairs of hand-related (e.g. to grab-to point) or mouth-related (e.g. to speak-to sing) verbs, whereas semantic priming was assessed using event-related potentials. Presentation of the first verb coincided with rTMS over the participant's cortical-left hand area and event-related brain potentials were analysed time-locked to the presentation onset of the second verb. Semantic integration - indexed by the N400 brain potential - was impaired for hand-related but not for mouth-related verb pairs after rTMS. This finding provides strong evidence that the motor cortex is involved in semantic encoding of action verbs, and supports the ‘embodied semantics' hypothesis

Abstract images and words can convey the same meaning

Intuitively, deriving meaning from an abstract image is a uniquely human, idiosyncratic experience. Here we show that, despite having no universally recognised lexical association, abstract images spontaneously elicit specific concepts conveyed by words, with a consistency akin to that of concrete images. We presented a group of naïve participants with abstract picture–word pairs construed as ‘related’ or ‘unrelated’ according to a preliminary norming procedure conducted with different participants. Surprisingly, the naïve participants with no prior exposure to the abstract images or any hints regarding their possible meaning, displayed a reaction time priming effect for ‘related’ versus ‘unrelated’ picture-word pairs. Critically, this behavioural priming effect, and an associated decrease in N400 mean amplitude indexing semantic priming, both correlated significantly with the degree of relatedness established in the preliminary norming procedure. Given that ratings and electrophysiological measures were obtained in different groups of individuals, our results show that abstract images evoke consistent meaning across observers, as has been shown in the case of music

Variations in pupil size related to memory for recently presented words and event related potentials

Pupillometry has been found to be correlated with activity of Cholinergic (ACh) and Noradrenergic (NE) neuromodulator systems. These systems regulate the level of cortical arousal and therefore perception, attention, and memory. Here we tested how different types of pupil size variance (prestimulus baseline and prestimulus hippus power) may correlate with behavioural and electrophysiological brain responses (ERPs). We recorded pupil size and ERPs whilst participants were presented with a series of words and then asked whether they had been in the initial list when they were later presented intermixed with unpresented words. We found that a smaller prestimulus baseline pupil size during the study phase was associated with better memory performance. Study items also evoked a larger P3 response at presentation and a greater old/new memory ERP effect at test when prestimulus pupil size was small rather than large. Prestimulus hippus power was found to be a between-subjects factor affecting the robustness of memory encoding with less power being associated with a greater old/new memory ERP effect. These results provide evidence relating memory and ERPs to variables defined on pupil size that are thought to reflect varying states of parasympathetic and sympathetic arousal.Output Status: Forthcoming/Available Onlin

Word meaning acquisition is reflected in brain potentials of isolated words

Learning a new concept and corresponding word typically involves repeated exposure to the word in the same or a similar context until the link crystallizes in long term memory. Although electrophysiological indices of the result of learning are well documented, there is currently no measure of the process of conceptually-mediated learning itself. Here, we recorded event-related brain potentials from participants who read unfamiliar words presented in isolation followed by a definition that either explained the meaning of the word or was a true, but uninformative statement. Self-reported word knowledge ratings increased for those words that were followed by meaningful definitions and were correlated with a decrease in ERP amplitude of a late frontal negativity (LFN) elicited by the isolated word. Importantly, the rate of LFN amplitude change predicted post-hoc learning outcome measures. Therefore, the LFN is real-time measure that is not under conscious control and which reflects conceptually-mediated learning. We propose that the LFN provides for the first time the opportunity to assess learning during study

Anomalous Transfer of Syntax between Languages

Each human language possesses a set of distinctive syntactic rules. Here, we show that balanced Welsh-English bilinguals reading in English unconsciously apply a morphosyntactic rule that only exists in Welsh. The Welsh soft mutation rule determines whether the initial consonant of a noun changes based on the grammatical context (e.g., the feminine noun cath-"cat" mutates into gath in the phrase y gath-"the cat"). Using event-related brain potentials, we establish that English nouns artificially mutated according to the Welsh mutation rule (e.g., "goncert" instead of "concert") require significantly less processing effort than the same nouns implicitly violating Welsh syntax. Crucially, this effect is found whether or not the mutation affects the same initial consonant in English and Welsh, showing that Welsh syntax is applied to English regardless of phonological overlap between the two languages. Overall, these results demonstrate for the first time that abstract syntactic rules transfer anomalously from one language to the other, even when such rules exist only in one language

Episodic traces and statistical regularities: Paired associate learning in typical and dyslexic readers

Learning visual-phonological associations is a key skill underlying successful reading acquisition. However, we are yet to understand the cognitive mechanisms that enable efficient learning in good readers, and those which are aberrant in individuals with developmental dyslexia. Here, we use a repeated cued-recall task to examine how typical and reading-impaired adults acquire novel associations between visual and phonological stimuli, incorporating a looking-at-nothing paradigm to probe implicit memory for target locations. Cued recall accuracy revealed that typical readers’ recall of novel phonological associates was better than dyslexic readers’ recall, and it also improved more with repetition. Eye fixation-contingent error analyses suggest that typical readers’ greater improvement from repetition reflects their more robust encoding and/or retrieval of each instance in which a given pair was presented: whereas dyslexic readers tended to recall a phonological target better when fixating its most recent location, typical readers showed this pattern more strongly when the target location was consistent across multiple trials. Thus, typical readers’ greater success in reading acquisition may derive from their better use of statistical contingencies to identify consistent stimulus features across multiple exposures. We discuss these findings in relation to the role of implicit memory in forming new visual-phonological associations as a foundational skill in reading, and areas of weakness in developmental dyslexia

Little Scientists – Big Impact

First paragraph: In the Division of Psychology at the University of Stirling, we regard our onsite kindergarten as one of our greatest assets. However, when we say this to others, we are used to encountering reactions that range from incredulity or uneasiness to plain bewilderment. Some assume that we maintain the kindergarten to provide a childcare facility for staff. Others, who understand that the primary function of the kindergarten is to facilitate our research and research-led teaching, seem to think that the childcare experience itself might be somehow compromised by this goal. Readers may be relieved to hear that we don’t keep the children under strictly controlled conditions, austere and isolated, like bacteria in a petri dish. But we decided that it was time that we put the record straight more broadly

Auditory processing and high task demands facilitate the bilingual executive control advantage in young adults

Although bilingual children and elderly have been observed to outperform monolinguals in typical executive control tasks, this bilingual advantage is not consistently found in the young adult population. Proponents of the bilingual executive control advantage argue the reason for this is that task demands in the typical tasks used are not high enough, since young adults perform at ceiling level, whereas critics of the effect argue it has benefited from publication bias. Here we test the task-load hypothesis using a standard and a difficult version of the arrow-flanker task and identify stimulus processing characteristics underlying greater bilingual executive control. We increased task demands by using an “Opposite” task in which participants were to respond to the central arrow indicating its opposite direction whilst a task cue indicated which task was to be performed at each trial. Further increase in task difficulty was expected to arise from reducing the task preparation time by using different stimulus-onset-asynchronies between cue and target stimuli. As predicted, we observed no language group differences in the normal flanker task, whereas bilinguals displayed less errors than monolinguals and were less hampered by the difficult task than monolinguals when auditory task cues were used. Event-related potentials (ERPs) revealed that the bilinguals’ conflict monitoring response occurred much earlier than the monolinguals’ when the task cue was auditory but less so when the cue was visual. Indeed, bilinguals appeared to prioritize the cue signal when it was auditory, but not when it was visual. Further ERP results showed bilinguals displayed greater attentional responses to the target stimulus than monolinguals. Finally, the behavioral and conflict-monitoring ERP responses correlated with language proficiency and usage scores. Together, these results show that when tasks demands are high and auditory processing is part of the task, bilingual adults outperform monolinguals due to better stimulus identification and greater efficiency in managing task demands

Event-related brain potentials reveal the time-course of language change detection in early bilinguals

Using event-related brain potentials, we investigated the temporal course of language change detection in proficient bilinguals as compared to matched controls. Welsh-English bilingual participants and English controls were presented with a variant of the oddball paradigm involving picture-word pairs. The language of the spoken word was manipulated such that English was the frequent stimulus (75%) and Welsh the infrequent stimulus (25%). We also manipulated semantic relatedness between pictures and words, such that only half of the pictures were followed by a word that corresponded with the identity of the picture. The P2 wave was significantly modulated by language in the bilingual group only, suggesting that this group detected a language change as early as 200 ms after word onset. Monolinguals also reliably detected the language change, but at a later stage of semantic integration (N400 range), since Welsh words were perceived as meaningless. The early detection of a language change in bilinguals triggered stimulus re-evaluation mechanisms reflected by a significant P600 modulation by Welsh words. Furthermore, compared to English unrelated words, English words matching the picture identity elicited significantly greater P2 amplitudes in the bilingual group only, suggesting that proficient bilinguals validate an incoming word against their expectation based on the context. Overall, highly proficient bilinguals appear to detect language changes very early on during speech perception and to consciously monitor language changes when they occur