The effect of induced mood on word imagery processing: An ERP study

Measuring brain potentials of imagination linked to physiological needs and motivational states

Introduction

While EEG signals reflecting motor and perceptual imagery are effectively used in brain computer interface (BCI) contexts, little is known about possible indices of motivational states. In the present study, electrophysiological markers of imagined motivational states, such as craves and desires were investigated.

Methods

Event-related potentials (ERPs) were recorded in 31 participants during perception and imagery elicited by the presentation of 360 pictograms. Twelve micro-categories of needs, subdivided into four macro-categories, were considered as most relevant for a possible BCI usage, namely: primary visceral needs (e.g., hunger, linked to desire of food); somatosensory thermal and pain sensations (e.g., cold, linked to desire of warm), affective states (e.g., fear: linked to desire of reassurance) and secondary needs (e.g., desire to exercise or listen to music). Anterior N400 and centroparietal late positive potential (LPP) were measured and statistically analyzed.

Results

N400 and LPP were differentially sensitive to the various volition stats, depending on their sensory, emotional and motivational poignancy. N400 was larger to imagined positive appetitive states (e.g., play, cheerfulness) than negative ones (sadness or fear). In addition, N400 was of greater amplitude during imagery of thermal and nociceptive sensations than other motivational or visceral states. Source reconstruction of electromagnetic dipoles showed the activation of sensorimotor areas and cerebellum for movement imagery, and of auditory and superior frontal areas for music imagery.

Discussion

Overall, ERPs were smaller and more anteriorly distributed during imagery than perception, but showed some similarity in terms of lateralization, distribution, and category response, thus indicating some overlap in neural processing, as also demonstrated by correlation analyses. In general, anterior frontal N400 provided clear markers of subjects’ physiological needs and motivational states, especially cold, pain, and fear (but also sadness, the urgency to move, etc.), than can signal life-threatening conditions. It is concluded that ERP markers might potentially allow the reconstruction of mental representations related to various motivational states through BCI systems.

Positive and negative moods differently affect creative meaning processing in both the native and non-native language

Previous research has shown that positive and negative moods differently modulate lexico-semantic processes. However, little is known about effects of mood on creative meaning comprehension in bilinguals. Here, Polish-English (L1-L2) female bilinguals made meaningfulness judgments on L1 and L2 novel metaphoric, literal, and anomalous sentences during an EEG session featuring positive and negative mood induction. While novel metaphors elicited comparable event-related potential responses to anomalous sentences in the N400 time frame indexing lexico-semantic processing, the former evoked smaller amplitudes than the anomalous condition in the late positive complex (LPC) window, marking meaning re-evaluation. Also, the LPC responses to the three sentence types all converged when participants were in a negative mood, indicating that a negative mood, unlike a positive one, inhibits reliance on general knowledge structures and leads to more detail-oriented processing of semantically complex meanings in both L1 and L2.

Mood effects on semantic processes: Behavioural and electrophysiological evidence

Mood (i.e., our current background affective state) often unobtrusively yet pervasively affects how we think and behave. Typically, theoretical frameworks position it as an embodied source of information (i.e., a biomarker), activating thinking patterns that tune our attention, perception, motivation, and exploration tendencies in a context-dependent manner. Growing behavioural and electrophysiological research has been exploring the mood–language interactions, employing numerous semantics-oriented experimental paradigms (e.g., manipulating semantic associations, congruity, relatedness, etc.) along with mood elicitation techniques (e.g., affectively evocative film clips, music, pictures, etc.). Available behavioural and electrophysiological evidence has suggested that positive and negative moods differently regulate the dynamics of language comprehension, mostly due to the activation of mood-dependent cognitive strategies. Namely, a positive mood has been argued to activate global and heuristics-based processing and a negative mood – local and detail-oriented processing during language comprehension. Future research on mood–language interactions could benefit greatly from (i) a theoretical framework for mood effects on semantic memory, (ii) measuring mood changes multi-dimensionally, (iii) addressing discrepancies in empirical findings, (iv) a replication-oriented approach, and (v) research practices counteracting publication biases.

In a Bilingual Mood: Mood Affects Lexico-Semantic Processing Differently in Native and Non-Native Languages

Positive and negative moods tend to have differential effects on lexico-semantic processing in the native language (L1). Though accumulating evidence points to dampened sensitivity to affective stimuli in the non-native language (L2), little is known about the effects of positive and negative moods on L2 processing. Here, we show that lexico-semantic processing is differently affected by positive and negative moods only in L1. Unbalanced Polish–English bilinguals made meaningfulness judgments on L1 and L2 sentences during two EEG recording sessions featuring either positive- or negative-mood-inducing films. We observed a reduced N1 (lexical processing) for negative compared to positive mood in L2 only, a reduced N2 (lexico-semantic processing) in negative compared to positive mood in L1 only, a reduced N400 (lexico-semantic processing) for meaningless compared to meaningful L1 sentences in positive mood only, and an enhanced late positive complex (semantic integration and re-analysis) for L2 compared to L1 meaningful sentence in negative mood only. Altogether, these results suggest that positive and negative moods affect lexical, lexico-semantic, and semantic processing differently in L1 and L2. Our observations are consistent with previous accounts of mood-dependent processing and emotion down-regulation observed in bilinguals.

Spatiotemporal target selection for intracranial neural decoding of abstract and concrete semantics

Decoding the inner representation of a word meaning from human cortical activity is a substantial challenge in the development of speech brain-machine interfaces (BMIs). The semantic aspect of speech is a novel target of speech decoding that may enable versatile communication platforms for individuals with impaired speech ability; however, there is a paucity of electrocorticography studies in this field. We decoded the semantic representation of a word from single-trial cortical activity during an imageability-based property identification task that required participants to discriminate between the abstract and concrete words. Using high gamma activity in the language-dominant hemisphere, a support vector machine classifier could discriminate the 2-word categories with significantly high accuracy (73.1 ± 7.5%). Activities in specific time components from two brain regions were identified as significant predictors of abstract and concrete dichotomy. Classification using these feature components revealed that comparable prediction accuracy could be obtained based on a spatiotemporally targeted decoding approach. Our study demonstrated that mental representations of abstract and concrete word processing could be decoded from cortical high gamma activities, and the coverage of implanted electrodes and time window of analysis could be successfully minimized. Our findings lay the foundation for the future development of semantic-based speech BMIs.

Visual discrimination accuracy does not differ between nasal inhalation and exhalation when stimuli are voluntarily aligned to breathing phase

This study investigated the possible enhancement of visual discrimination accuracy by voluntarily adjusting the timing of stimulus presentation to a specific respiratory phase. Previous research has suggested that respiratory phases modulate perceptual and cognitive processing. For instance, a fearful face was identified faster when presented during nasal inhalation than during nasal exhalation, which could be related to changes in neural oscillatory activity synchronized with breathing in through one's nose. Based on such findings, the present study asked 40 young adults to perform an emotional discrimination task consisting of distinguishing fearful vs. neutral faces and a physical discrimination task consisting of distinguishing high- vs. low-contrast Gabor patches during nasal respiration. Participants presented themselves with the stimuli to be judged in a designated respiratory phase by pressing a button. It was hypothesized that fear discrimination accuracy would be higher during inhalation than exhalation if sensitivity to emotional stimuli increased during inhalation. Conversely, if overall visual sensitivity was enhanced during inhalation, the identical effect was expected for contrast discrimination. The results indicated that discrimination accuracy did not differ between inhalation and exhalation phases in either task. This result provided no evidence that the respiratory phase affected visual discrimination accuracy when people adjusted the timing of stimulus presentation to the onset of inhalation or exhalation.

A Difference of Past Self-Evaluation Between College Students With Low and High Socioeconomic Status: Evidence From Event-Related Potentials

Socioeconomic status (SES) refers to the social position or class according to their material and non-material social resources. We conducted a study with 60 college students to explore whether SES affects past self-evaluation and used event-related potentials (ERPs) in a self-reference task that required participants to judge whether the trait adjectives (positive or negative) describing themselves 5 years ago were appropriate for them. Behavioral data showed that individuals’ positive past self-evaluations were significantly higher than individuals’ negative past self-evaluations, regardless of high or low SES. Individuals with high SES had significantly higher positive past self-evaluations than those with low SES. ERP data showed that in the low SES group, negative adjectives elicited a marginally greater N400 amplitude than positive adjectives; in the high SES group, negative adjectives elicited a greater late positive potential (LPP) amplitude than positive adjectives. N400 is an index of the accessibility of semantic processing, and a larger N400 amplitude reflects less fluent semantic processing. LPP is an index of continuous attention during late processing; the larger LPP amplitude is elicited, the more attention resources are invested. Our results indicated that compared with college students with low SES, the past self-evaluations of college students with high SES were more positive; college students with high SES paid more attention to negative adjectives. However, college students with low SES were marginally less fluent in processing negative adjectives.

High-frequency sound components of high-resolution audio are not detected in auditory sensory memory

High-resolution digital audio is believed to produce a better listening experience than the standard quality audio, such as compact disks (CDs) and digital versatile disks (DVDs). One common belief is that high-resolution digital audio is superior due to the higher frequency (> 22 kHz) of its sound components, a characteristic unique to this audio. This study examined whether sounds with high-frequency components were processed differently from similar sounds without these components in the auditory cortex. Mismatch negativity (MMN), an electrocortical index of auditory deviance detection in sensory memory, was recorded in young adults with normal hearing (N = 38) using two types of white noise bursts: original sound and digitally filtered sound from which high-frequency components were removed. The two sounds did not produce any MMN response and could not be discriminated behaviourally. In conclusion, even if high-resolution audio is superior to the standard format, the difference is apparently not detectable at the cortical level.

Time Passes Slowly When You Are Concealing Something

The item to be concealed elicits greater physiological arousal than other items. Since high physiological arousal causes an overestimation of time, the display duration of an item is expected to be perceived as longer when people intend to conceal it. After stealing and concealing one item, 36 university students were asked to judge the display duration of an item as shorter than, equal to, or longer than a memorised duration of 2 s. Pictures of three items including the stolen item were presented in the guilty condition, whereas pictures of three items that had not been stolen were presented in the innocent condition. The display of all items in the guilty condition was perceived as longer than in the innocent condition without difference between the concealed and other items. The intention to conceal increases tonic arousal reflected in a higher skin conductance level and leads to a non-specific temporal overestimation.

Embodied Cognition in Performance: The Impact of Michael Chekhov's Acting Exercises on Affect and Height Perception

Modern embodied approaches to cognitive science overlap with ideas long explored in theater. Performance coaches such as Michael Chekhov have emphasized proprioceptive awareness of movement as a path to attaining psychological states relevant for embodying characters and inhabiting fictional spaces. Yet, the psychology of performance remains scientifically understudied. Experiments, presented in this paper, investigated the effects of three sets of exercises adapted from Chekhov's influential techniques for actors' training. Following a continuous physical demonstration and verbal prompts by the actress Bonnie Eckard, 29 participants enacted neutral, expanding, and contracting gestures and attitudes in space. After each set of exercises, the participants' affect (pleasantness and arousal) and self-perceptions of height were measured. Within the limitations of the study, we measured a significant impact of the exercises on affect: pleasantness increased by 50% after 15 min of expanding exercises and arousal increased by 15% after 15 min of contracting exercises, each relative to the other exercise. Although the exercises produced statistically non-significant changes in the perceived height, there was a significant relation between perceived height and affect, in which perceived height increased with increases in either pleasantness, or arousal. These findings provide a preliminary support for Chekhov's intuition that expanding and contracting physical actions exert opposite effects on the practitioners' psychological experience. Further studies are needed to consider a wider range of factors at work in Chekhov's method and the embodied experience of acting in general.