ENHANCING IMPLICIT LEARNING WITH POSTHYPNOTIC SUGGESTION: An ERP Study.

Can posthypnotic suggestion (PHS) enhance cognitive abilities? The authors tested behaviorally and with event-related potentials (ERP) if sequential learning (SL), the ability to learn statistical regularities, can be enhanced with PHS. Thirty adults were assessed with the Stanford Hypnotic Susceptibility Scale (Form C) and an auditory SL task. Before this task, half the sample received a PHS to enhance SL, and the other half received the same suggestion under normal waking state. Response times and ERPs indicated a strong effect of PHS. Compared to the control group, PHS inverted, attenuated, or left unaffected the response time SL effect in low, medium, and high hypnotizability participants, respectively. These results suggest that PHS cannot be used to enhance SL.

Visual statistical learning is related to natural language ability in adults: An ERP study.

Statistical learning (SL) is believed to enable language acquisition by allowing individuals to learn regularities within linguistic input. However, neural evidence supporting a direct relationship between SL and language ability is scarce. We investigated whether there are associations between event-related potential (ERP) correlates of SL and language abilities while controlling for the general level of selective attention. Seventeen adults completed tests of visual SL, receptive vocabulary, grammatical ability, and sentence completion. Response times and ERPs showed that SL is related to receptive vocabulary and grammatical ability. ERPs indicated that the relationship between SL and grammatical ability was independent of attention while the association between SL and receptive vocabulary depended on attention. The implications of these dissociative relationships in terms of underlying mechanisms of SL and language are discussed. These results further elucidate the cognitive nature of the links between SL mechanisms and language abilities.

Effect of pattern awareness on the behavioral and neurophysiological correlates of visual statistical learning.

Statistical learning is the ability to extract predictive patterns from structured input. A common assumption is that statistical learning is a type of implicit learning that does not result in explicit awareness of learned patterns. However, there is also some evidence that statistical learning may involve explicit processing to some extent. The purpose of this study was to examine the effect of pattern awareness on behavioral and neurophysiological correlates of visual statistical learning. Participants completed a visual learning task while behavioral responses and event-related potentials were recorded. Following the completion of the task, awareness of statistical patterns was assessed through a questionnaire scored by three independent raters. Behavioral findings indicated learning only for participants exhibiting high pattern awareness levels. Neurophysiological data indicated that only the high-pattern awareness group showed expected P300 event-related potential learning effects, although there was also some indication that the low awareness groups showed a sustained mid- to late-latency negativity. Linear mixed-model analyses confirmed that only the high awareness group showed neurophysiological indications of learning. Finally, source estimation results revealed left hemispheric activation was associated with statistical learning extending from frontal to occipital and parietal regions. Further analyses suggested that left insula, left parahippocampal, and right precentral regions showed different levels of activation based on pattern awareness. To conclude, we found that pattern awareness, a dimension associated with explicit processing, strongly influences the behavioral and neurophysiological correlates of visual statistical learning.

Effects of Transcranial Magnetic Stimulation on Body Perception: No Evidence for Specificity of the Right Temporo-Parietal Junction.

Previous data suggest that the right temporo-parietal junction (rTPJ) may have a specific role in abnormal body perception (ABP), including out-of-body experience. We tested this hypothesis with inhibitory (1 Hz) and excitatory (15 Hz) repetitive transcranial magnetic stimulation (rTMS) of the rTPJ and a control site (CS, 5 cm posterior to the rTPJ along the lateral sulcus direction in Brodmann area 19R) in 35 healthy adults. ABP frequency was higher with 1 Hz than with 15 Hz rTMS but unaffected by the rTMS site (rTPJ/CS). Response to an own-body transformation task were delayed with 1 Hz compared to 15 Hz rTMS but also unaffected by rTMS site. ABP from rTMS at both sites induced electroencephalographic power decrease in all frequencies at left anterior and central cortical sites. Our data suggest that inhibitory rTMS can lead to ABP. However, the rTPJ may not play a specific role in this process.

Neurocognitive mechanisms of statistical-sequential learning: what do event-related potentials tell us?

Statistical-sequential learning (SL) is the ability to process patterns of environmental stimuli, such as spoken language, music, or one's motor actions, that unfold in time. The underlying neurocognitive mechanisms of SL and the associated cognitive representations are still not well understood as reflected by the heterogeneity of the reviewed cognitive models. The purpose of this review is: (1) to provide a general overview of the primary models and theories of SL, (2) to describe the empirical research - with a focus on the event-related potential (ERP) literature - in support of these models while also highlighting the current limitations of this research, and (3) to present a set of new lines of ERP research to overcome these limitations. The review is articulated around three descriptive dimensions in relation to SL: the level of abstractness of the representations learned through SL, the effect of the level of attention and consciousness on SL, and the developmental trajectory of SL across the life-span. We conclude with a new tentative model that takes into account these three dimensions and also point to several promising new lines of SL research.

Resting brain activity varies with dream recall frequency between subjects.

Dreaming is still poorly understood. Notably, its cerebral underpinning remains unclear. Neuropsychological studies have shown that lesions in the temporoparietal junction (TPJ) and/or the white matter of the medial prefrontal cortex (MPFC) lead to the global cessation of dream reports, suggesting that these regions of the default mode network have key roles in the dreaming process (forebrain 'dream-on' hypothesis). To test this hypothesis, we measured regional cerebral blood flow (rCBF) using [(15)O]H2O positron emission tomography in healthy subjects with high and low dream recall frequencies (DRFs) during wakefulness (rest) and sleep (rapid eye movement (REM) sleep, N2, and N3). Compared with Low recallers (0.5 ± 0.3 dream recall per week in average), High recallers (5.2 ± 1.4) showed higher rCBF in the TPJ during REM sleep, N3, and wakefulness, and in the MPFC during REM sleep and wakefulness. We demonstrate that the resting states of High recallers and Low recallers differ during sleep and wakefulness. It coheres with previous ERP results and confirms that a high/low DRF is associated with a specific functional organization of the brain. These results support the forebrain 'dream-on' hypothesis and suggest that TPJ and MPFC are not only involved in dream recall during wakefulness but also have a role in dreaming during sleep (production and/or encoding). Increased activity in the TPJ and MPFC might promote the mental imagery and/or memory encoding of dreams. Notably, increased activity in TPJ might facilitate attention orienting toward external stimuli and promote intrasleep wakefulness, facilitating the encoding of the dreams in memory.

REHABILITATING LANGUAGE DISORDERS BY IMPROVING SEQUENTIAL PROCESSING: A REVIEW.

Recent research suggests that language processing (LP) may rely heavily on sequential processing (SP), a cognitive ability that allows people to process the patterns of environmental stimuli that unfold in time, such as spoken language or music. Indeed, spoken language corresponds to a set of linguistic units (e.g., phonemes, syllables, words) that are organized in time in a non-random way, according to phonotactic and syntactic rules. In this review, we discuss recent research highlighting the importance of SP for learning and processing such linguistic regularities and argue that interventions focused on improving SP may provide a potentially effective way to rehabilitate language impairments. The first part of this review presents a series of findings showing that LP is intimately related to SP. We review the literature on populations with normal LP performance suggesting that LP relies upon SP. We then report two recent studies from our lab that demonstrated a direct link between LP and SP: (1) a behavioral study showing that variations on a non-linguistic SP task are significantly associated with LP, and (2) an event-related potential study showing that the neural correlates of SP interact with LP abilities in healthy adults. The second part of this review summarizes the literature suggesting that populations with LP impairments (such as language delays due to hearing loss, dyslexia, specific language impairment, and aphasia) also display SP impairments. Thus, disturbances to SP appear to be a commonality among what appears to be very different types of LP impairments, suggesting that impaired SP causes or exacerbates LP impairment. This leads to the third part of this review, where we first summarize recent findings from brain plasticity showing that: (1) cognitive training can improve cognitive processing, and that (2) increasing cognitive processing performance through training can result in a cognitive "transfer" by also increasing performance on other related cognitive skills. We then present a potentially new method for LP remediation that is based on the idea that some LP impairments might stem directly from SP disturbances and that improving SP processing will, via transfer, result in increased LP performance. This method was applied by our research team to conduct a study aimed at improving SP and LP mechanisms. To our knowledge, the SP training study presented here shows the first evidence that SP performance can be improved and therefore has strong clinical implications as a potentially effective and novel intervention to treat LP impairments.

Working memory is partially preserved during sleep.

Although several cognitive processes, including speech processing, have been studied during sleep, working memory (WM) has never been explored up to now. Our study assessed the capacity of WM by testing speech perception when the level of background noise and the sentential semantic length (SSL) (amount of semantic information required to perceive the incongruence of a sentence) were modulated. Speech perception was explored with the N400 component of the event-related potentials recorded to sentence final words (50% semantically congruent with the sentence, 50% semantically incongruent). During sleep stage 2 and paradoxical sleep: (1) without noise, a larger N400 was observed for (short and long SSL) sentences ending with a semantically incongruent word compared to a congruent word (i.e. an N400 effect); (2) with moderate noise, the N400 effect (observed at wake with short and long SSL sentences) was attenuated for long SSL sentences. Our results suggest that WM for linguistic information is partially preserved during sleep with a smaller capacity compared to wake.

The N400 and Late Positive Complex (LPC) Effects Reflect Controlled Rather than Automatic Mechanisms of Sentence Processing.

This study compared automatic and controlled cognitive processes that underlie event-related potentials (ERPs) effects during speech perception. Sentences were presented to French native speakers, and the final word could be congruent or incongruent, and presented at one of four levels of degradation (using a modulation with pink noise): no degradation, mild degradation (2 levels), or strong degradation. We assumed that degradation impairs controlled more than automatic processes. The N400 and Late Positive Complex (LPC) effects were defined as the differences between the corresponding wave amplitudes to incongruent words minus congruent words. Under mild degradation, where controlled sentence-level processing could still occur (as indicated by behavioral data), both N400 and LPC effects were delayed and the latter effect was reduced. Under strong degradation, where sentence processing was rather automatic (as indicated by behavioral data), no ERP effect remained. These results suggest that ERP effects elicited in complex contexts, such as sentences, reflect controlled rather than automatic mechanisms of speech processing. These results differ from the results of experiments that used word-pair or word-list paradigms.

Subliminal semantic priming in speech.

Numerous studies have reported subliminal repetition and semantic priming in the visual modality. We transferred this paradigm to the auditory modality. Prime awareness was manipulated by a reduction of sound intensity level. Uncategorized prime words (according to a post-test) were followed by semantically related, unrelated, or repeated target words (presented without intensity reduction) and participants performed a lexical decision task (LDT). Participants with slower reaction times in the LDT showed semantic priming (faster reaction times for semantically related compared to unrelated targets) and negative repetition priming (slower reaction times for repeated compared to semantically related targets). This is the first report of semantic priming in the auditory modality without conscious categorization of the prime.

Emotional electrodermal response in coma and other low-responsive patients.

Emotional processing in coma remains an open question. Skin conductance responses to emotional and neutral auditory stimuli were recorded in 13 low-responsive patients (12 of whom were in coma). A differential response between emotional and neutral stimuli was found, which significantly correlated with the Glasgow Coma Scale and the Cook and Palma score. These correlations indicate that emotional processing can occur in coma patients with relatively high clinical scores of reactivity.

Temporal aspects of the feeling of familiarity for music and the emergence of conceptual processing.

We tested whether the emergence of familiarity to a melody may trigger or co-occur with the processing of the concept(s) conveyed by emotions to, or semantic association with, the melody. With this objective, we recorded ERPs while participants were presented with highly familiar and less familiar melodies in a gating paradigm. The ERPs time locked to a tone of the melody called the "familiarity emergence point" showed a larger fronto-central negativity for highly familiar compared with less familiar melodies between 200 and 500 msec, with a peak latency around 400 msec. This latency and the sensitivity to the degree of familiarity/conceptual information suggest that this component was an N400, a marker of conceptual processing. Our data suggest that the feeling of familiarity evoked by a musical excerpt could be accompanied by other processing mechanisms at the conceptual level. Coupling the gating paradigm with ERP analyses might become a new avenue for investigating the neurocognitive basis of implicit musical knowledge.

Cortical information processing in coma.

OBJECTIVES: To evaluate cortical information processing (particularly, semantic processing) in acute nontraumatic coma by means of event-related brain potentials (ERPs). METHODS: The tests included measures of obligatory auditory processing (N100), automatic (Mismatch Negativity) and controlled (P300) detection of stimulus deviance, and semantic processing (ERP effects in word pairs and sentences). The tests were presented to 20 healthy participants and 42 coma patients with Glasgow Coma Scale <9. RESULTS: Responders (ie, patients whose ERP data indicate that their brain was able to process the corresponding stimuli) were found in each ERP test, and their distribution was statistically different from that expected by chance. Particularly, 7 responders were found in the word pair paradigm and 3 responders in the sentence paradigm. The P300 responsiveness highly correlated with other ERP responses, with Glasgow Coma Scale and with the future development of coma (ie, P300 on day 4 was related to the clinical state on day 20). CONCLUSIONS: Results suggest a wide range of cortical information processing in coma, including semantic processing. The question is discussed of whether, and to what extent, these processing operations are related to conscious awareness of stimuli.

Is conceptual processing in music automatic? An electrophysiological approach.

Recent evidence suggests that music perception, much alike language perception, involves the cognitive processing of concepts, that is abstract general ideas. In a previous study (Daltrozzo and Schön, Conceptual processing in music as revealed by N400 effects on words and musical targets. Journal of Cognitive Neuroscience, In Press), we reported the effect of the presentation of a musical excerpt (the context) on the perception of a word, while participants judged the conceptual relatedness between the two stimuli. Event-Related Potentials (ERPs) showed a N400 effect: a larger N400 to words judged unrelated to their context compared to related words. In the present experiment, we decided to test the influence of the relatedness task on the N400 effect by using a more implicit task: lexical decision. We recorded behavioral and ERP data while participants were presented 50 related and 50 unrelated pairs (excerpt context/word target). An N400 effect was again observed. However, the N400 effect found with a lexical decision was more than two times smaller than with a relatedness judgment task and was significant in a later latency range: 500 to 650 ms instead of 300 to 550 ms with a relatedness judgment. These differences are interpreted as reflecting the task-induced modulation of explicit (strategic) mechanisms involved in the N400 effect.

Conceptual processing in music as revealed by N400 effects on words and musical targets.

The cognitive processing of concepts, that is, abstract general ideas, has been mostly studied with language. However, other domains, such as music, can also convey concepts. Koelsch et al. [Koelsch, S., Kasper, E., Sammler, D., Schulze, K., Gunter, T., & Friederici, A. D. Music, language and meaning: Brain signatures of semantic processing. Nature Neuroscience, 7, 302-307, 2004] showed that 10 sec of music can influence the semantic processing of words. However, the length of the musical excerpts did not allow the authors to study the effect of words on musical targets. In this study, we decided to replicate Koelsch et al. findings using 1-sec musical excerpts (Experiment 1). This allowed us to study the reverse influence, namely, of a linguistic context on conceptual processing of musical excerpts (Experiment 2). In both experiments, we recorded behavioral and electrophysiological responses while participants were presented 50 related and 50 unrelated pairs (context/target). Experiments 1 and 2 showed a larger N400 component of the event-related brain potentials to targets following a conceptually unrelated compared to a related context. The presence of an N400 effect with musical targets suggests that music may convey concepts. The relevance of these results for the comprehension of music as a structured set of conceptual units and for the domain specificity of the mechanisms underlying N400 effects are discussed.

Sex differences in two event-related potentials components related to semantic priming.

Although sex differences in language processing are well documented in behavioral studies, only a few electrophysiological studies have explored this topic. We analyzed sex differences in two language-related components of event-related potentials (ERPs): the N400 and the Late Positive Complex (LPC). Ten men and 10 women, matched by age and handedness, participated in the study. Two semantic priming paradigms were presented: word pairs (60 congruent and 60 incongruent) and sentences (50 with congruent and 50 with incongruent ending words). In addition, the effect of context was investigated by a comparison between ERP effects obtained in single word priming and sentential priming. The N400 effect was earlier and larger in women, and the LPC effect was larger in men. Furthermore, the LPC effect in men, but not in women, was much larger with sentence priming than with word priming, suggesting that the LPC effect may be more dependent on context in men than in women. The opposite sex difference on the two ERP components indicates different underlying mechanisms. While the LPC effect is thought to be generated by purely explicit mechanisms, such as postlexical integrative processes, the N400 effect may be also governed by prelexical implicit and explicit mechanisms. Our results were consistent with the notion of more automated processing of language in women than in men.