The neural basis of illusory gustatory sensations: two rare cases of lexical-gustatory synaesthesia

Lexical-gustatory synaesthesia is a rare phenomenon in which the individual experiences flavour sensations when they read, hear, or imagine words. In this study, we provide insight into the neural basis of this form of synaesthesia using functional neuroimaging. Words known to evoke pleasant, neutral, and unpleasant synaesthetic tastes and synaesthetically tasteless words were presented to two lexical-gustatory synaesthetes, during fMRI scanning. Ten non-synaesthetic participants were also scanned on the same list of words. The synaesthetic brain displayed a different pattern of activity to words when compared to the non-synaesthetes, with insula activation related to viewing words that elicited tastes that have an associated emotional valence (i.e., pleasant or unpleasant tastes). The subjective intensity of the synaesthesia was correlated with activity in the medial parietal lobes (precuneus/retrosplenial cortex), which are implicated in polymodal imagery and self-directed thought. This region has also previously been activated in studies of lexical-colour synaesthesia, suggesting its role may not be limited to the type of synaesthesia explored here.     

Visuo-spatial representations of the alphabet in synaesthetes and non-synaesthetes

Visuo-spatial representations of the alphabet (so-called 'alphabet forms') may be as common as other types of sequence-space synaesthesia, but little is known about them or the way they relate to implicit spatial associations in the general population. In the first study, we describe the characteristics of a large sample of alphabet forms visualized by synaesthetes. They most often run from left to right and have salient features (e.g., bends, breaks) at particular points in the sequence that correspond to chunks in the 'Alphabet Song' and at the alphabet mid-point. The Alphabet Song chunking suggests that the visuo-spatial characteristics are derived, at least in part, from those of the verbal sequence learned earlier in life. However, these synaesthetes are no faster at locating points in the sequence (e.g., what comes before/after letter X?) than controls. They tend to be more spatially consistent (measured by eye tracking) and letters can act as attentional cues to left/right space in synaesthetes with alphabet forms (measured by saccades), but not in non-synaesthetes. This attentional cueing suggests dissociation between numbers (which reliably act as attentional cues in synaesthetes and non-synaesthetes) and letters (which act as attentional cues in synaesthetes only).     

The aesthetic appeal of auditory-visual synaesthetic perceptions in people without synaesthesia

The term 'visual music' refers to works of art in which both hearing and vision are directly or indirectly stimulated. Our ability to create, perceive, and appreciate visual music is hypothesised to rely on the same multisensory processes that support auditory visual (AV) integration in other contexts. Whilst these mechanisms have been extensively studied, there has been little research on how these processes affect aesthetic judgments (of liking or preference). Studies of synaesthesia in which sound evokes vision and studies of cross-modal biases in non-synaesthetes have revealed non-arbitrary mappings between visual and auditory properties (eg high-pitch sounds being smaller and brighter). In three experiments, we presented members of the general population with animated AV clips derived from synaesthetic experiences and contrasted them with a number of control conditions. The control conditions consisted of the same clips rotated or with the colour changed, random AV pairings, or animated clips generated by non-synaesthetes. Synaesthetic AV animations were generally preferred over the control conditions. The results suggest that non-arbitrary AV mappings, present in the experiences of synaesthetes, can be readily appreciated by others and may underpin our tendency to engage with certain forms of art.     

Handedness and calendar orientations in time-space synaesthesia

In one common variant of time-space synaesthesia, individuals report the consistent experience of months bound to a spatial arrangement, commonly described as a circle extending outside of the body. Whereas the layout of these calendars has previously been thought to be relatively random and to differ greatly between synaesthetes, Study 1 provides the first evidence suggesting one critical aspect of these calendars is mediated by handedness: clockwise versus counter-clockwise orientation. A study of 34 time-space synaesthetes revealed a strong association between handedness and the orientation of circular calendars. That is, left-handed time-space synaesthetes tended to report counter-clockwise arrangements and right-handed synaesthetes clockwise. Study 2 tested whether a similar bias was present in non-synaesthetes whose task was to memorize and recall the spatial configuration of a clockwise and counter-clockwise calendar. Non-synaesthetes' relative performance on these two sorts of calendars was significantly correlated with their handedness scores in a pattern similar to synaesthetes. Specifically, left-handed controls performed better on counter-clockwise calendars compared to clockwise, and right-handed controls on clockwise over counter-clockwise. We suggest that the implicit biases seen in controls are mediated by similar mechanisms as in synaesthesia, highlighting the graded nature of synaesthetic associations.     

Cross-modal personality attributions in synaesthetes and non-synaesthetes

Those variants of synaesthesia that trigger colour are well studied, although comparatively less is known about variants that involve cognitive constructs such as personality types. Here we investigate sequence-personality synaesthesia (also known as ordinal linguistic personification, OLP) in which sequenced units (e.g., letters) become associated to personalities or genders. We present the first group study of this variant, showing similarities and differences between synaesthetes and non-synaesthetes. In Experiment 1, we show that synaesthetes differ from the general population in the phenomenology of their reports, the depth of their personality associations, and the consistency of those associations over time. In Experiment 2, we show that synaesthetes are similar to the general population in the underlying rules that link their personalities to letters. Specifically, we show that these mappings are not random, but are based on a shared rule system linking linguistic qualities of letters with quantitative dimensions of personality (based on Goldberg's Big Five personality traits; Goldberg, 1990, 1992). Synaesthetes tend to associate high-frequency letters with high agreeable and low neurotic personalities, and non-synaesthetes share these tendencies at an implicit level. Together, these data show that synaesthetes differ from the general population in phenomenological ways, but that their underlying mechanisms may be common to all people.     

First and second language in the brain: Neuronal correlates of language processing and spelling strategies

This study explores oscillatory brain activity by means of event-related synchronization and desynchronization (%ERS/ERD) of EEG activity during the use of phonological and orthographic-morphological spelling strategies in L2 (English) and L1 (German) in native German speaking children. EEG was recorded while 33 children worked on a task requiring either phonological or orthographic-morphological spelling strategies. L2 processing elicited more theta %ERS than L1 processing (particularly at bilateral frontal and right posterior parietal sites) which might suggest a stronger involvement of semantic encoding and retrieval of the less familiar L2. The highest level of theta %ERS was revealed for the orthographic-morphological strategy in L2 which might indicate a more intense way of lexical retrieval compared to the phonological strategy in L2 and the orthographic-morphological strategy in L1. Analyses moreover revealed that phonological processing (both in L1 and L2) was associated with comparatively strong left-hemispheric %ERD in the upper alpha frequency band.     

认知重评和表达抑制情绪调节策略的脑网络分析：来自EEG和ERP的证据

本文旨在对认知重评和表达抑制两种常用情绪调节策略的自发脑网络特征及认知神经活动进行深入探讨。研究采集36名在校大学生的静息态和任务态脑电数据, 经过源定位和图论分析发现节点效率与两种情绪调节显著相关的脑区, 以及脑区之间的功能连接。研究结果表明, 在使用认知重评进行情绪调节时会激活前额叶皮质、前扣带回、顶叶、海马旁回和枕叶等多个脑区, 在使用表达抑制进行情绪调节时会激活前额叶皮质、顶叶、海马旁回、枕叶、颞叶和脑岛等多个脑区。因此, 这些脑区的节点效率或功能连接强度可能成为评估个体使用认知重评和表达抑制调节情绪效果的指标。     

Training synaesthesia

Synaesthetic inducers such as graphemes are typically cultural artifacts. Thus, a learning component seems evident in synaesthesia (Simner et al, 2009 Brain 132 57-64). Normally, synaesthetes report to have their experiences since they can remember. Nevertheless, a recent training study suggests that synaesthesia can be mimicked in non-synaesthetes. To date, the role of learning during the development of synaesthesia is still debated. It is not clear whether synaesthesia can be learned or trained at all. To address this question, we compared a non-adaptive and an adaptive training for their effectiveness. We assessed their impact on two types of priming tasks, before and after the training. We found stronger priming in the adaptive training group suggesting that adaptive training is more efficient to mimic synaesthesia.     

没听到？“听”到！——来自听觉表象神经机制研究的证据

近年来听觉表象开始得到关注,相关研究包括言语声音、音乐声音、环境声音的听觉表象三类。本文梳理了认知神经科学领域对上述三种听觉表象所激活的脑区研究,比较了听觉表象和听觉对应脑区的异同,并展望了听觉表象未来的研究方向。     

Type-based associations in grapheme-color synaesthesia revealed by response time distribution analyses

Determining the nature of binding in grapheme-color synaesthesia has consequences for understanding the neural basis of synaesthesia and visual awareness in general. We evaluated type- and token-based letter-color binding using a synaesthetic version of the object-reviewing paradigm. Although mean response times failed to reveal any significant differences between synaesthetes and control participants, RT analyses with ex-Gaussian distributions revealed that the response facilitation in the synaesthesia group reflected type representations exclusively, while response facilitation in the control group, who learned letter-color associations, was dominated by token representations. Thus, letter-color associations in associator synaesthetes are type-based, and do not involve binding to object tokens, consistent with their subjective reports. Contrary to recent studies that failed to find differences between synaesthetes and non-synaesthetes with behavioral measures, response time distribution analyses indicate that color sensations in synaesthetes are not simply the extreme form of normal letter-color associations, and cannot be attributed to demand characteristics.     

Do children with grapheme-colour synaesthesia show cognitive benefits?

Grapheme-colour synaesthesia is characterized by conscious and consistent associations between letters and colours, or between numbers and colours (e.g., synaesthetes might see A as red, 7 as green). Our study explored the development of this condition in a group of randomly sampled child synaesthetes. Two previous studies (Simner & Bain, 2013, Frontiers in Human Neuroscience, 7, 603; Simner, Harrold, Creed, Monro, & Foulkes, 2009, Brain, 132, 57) had screened over 600 primary school children to find the first randomly sampled cohort of child synaesthetes. In this study, we evaluate this cohort to ask whether their synaesthesia is associated with a particular cognitive profile of strengths and/or weaknesses. We tested our child synaesthetes at age 10–11 years in a series of cognitive tests, in comparison with matched controls and baseline norms. One previous study (Green & Goswami, 2008, Cognition, 106, 463) had suggested that child synaesthetes might perform differently to non-synaesthetes in such tasks, although those participants may have been a special type of population independent of their synaesthesia. In our own study of randomly sampled child synaesthetes, we found no significant advantages or disadvantages in a receptive vocabulary test and a memory matrix task. However, we found that synaesthetes demonstrated above-average performance in a processing-speed task and a near-significant advantage in a letter-span task (i.e., memory/recall task of letters). Our findings point to advantages for synaesthetes that go beyond those expected from enhanced coding accounts and we present the first picture of the broader cognitive profile of a randomly sampled population of child synaesthetes.     

Atrophy of the parietal lobe in preclinical dementia

Cortical grey matter atrophy patterns have been reported in healthy ageing and Alzheimer disease (AD), but less consistently in the parietal regions of the brain. We investigated cortical grey matter volume patterns in parietal areas. The grey matter of the somatosensory cortex, superior and inferior parietal lobule was measured in 75 older adults (38 cognitively stable and 37 individuals with cognitive decline after 3 years). Dementia screening 6 years after scanning resulted in nine AD cases from the cognitively stable (n=3) and cognitive decline group (n=6), who were assigned to a third group, the preclinical AD group. When regional differences in cortical volume in the parietal lobe areas were compared between groups, significant differences were found between either the cognitive decline or stable group on the one hand and preclinical AD individuals on the other hand in the inferior parietal lobule. Group membership was best predicted by the grey matter volume of the inferior parietal lobule, compared to the other parietal lobe areas. The parietal lobe was characterised by a differential atrophy pattern based on cognitive status, which is in agreement with the 'last-developed-first-atrophied' principle. Future studies should investigate the surplus value of the inferior parietal lobe as a potential marker for the diagnosis of AD compared to other brain regions, such as the medial temporal lobe and the prefrontal lobe.     

Brain areas involved in synaesthesia: a review

Despite a recent upsurge of research, much remains unknown about the neurobiological mechanisms underlying synaesthesia. By integrating results obtained so far in Magnetic Resonance Imaging (MRI) studies, this contribution sheds light on the role of particular brain regions in synaesthetic experiences. First, in accordance with its sensory nature, it seems that the sensory brain areas corresponding to the type of synaesthetic experience are activated. Synaesthetic colour experiences can activate colour regions in occipito-temporal cortex, but this is not necessarily restricted to V4. Furthermore, sensory and motor brain regions have been obtained that extend beyond the particular type of synaesthesia studied. Second, differences in experimental setup, number and type of synaesthetes tested, and method to delineate regions of interest may help explain inconsistent results obtained in the BOLD-MRI (Blood Oxygen Level Dependent functional MRI) studies. Third, an overview of obtained results shows that a network of brain areas rather than a single brain region underlies synaesthesia. Six brain regions of overlapping results emerge, these regions are in sensory and motor regions as well as 'higher level' regions in parietal and frontal lobe. We propose that these regions are related to three different cognitive processes inherently part of synaesthesia; the sensory processes, the (attentional) 'binding' processes, and cognitive control processes. Finally, we discuss how these functional and structural brain properties might relate to the development of synaesthesia. In particular, we believe this relationship is better understood by separating the question what underlies the presence of synaesthesia ('trait') from what determines particular synaesthetic associations ('type').     

Development of infant sustained attention and its relation to EEG oscillations: an EEG and cortical source analysis study

The current study examined the relation between infant sustained attention and infant EEG oscillations. Fifty‐nine infants were tested at 6 (N = 15), 8 (N = 17), 10 (N = 14), and 12 (N = 13) months. Three attention phases, stimulus orienting, sustained attention, and attention termination, were defined based on infants' heart rate changes. Frequency analysis using simultaneously recorded EEG focused on infant theta (2–6 Hz), alpha (6–9 Hz), and beta (9–14 Hz) rhythms. Cortical source analysis of EEG oscillations was conducted with realistic infant MRI models. Theta synchronization was found over fontal pole, temporal, and parietal electrodes during infant sustained attention for 10 and 12 months. Alpha desynchronization was found over frontal, central and parietal electrodes during sustained attention. This alpha effect started to emerge at 10 months and became well established by 12 months. No difference was found for the beta rhythm between different attention phases. The theta synchronization effect was localized to the orbital frontal, temporal pole, and ventral temporal areas. The alpha desynchronization effect was localized to the brain regions composing the default mode network including the posterior cingulate cortex and precuneus, medial prefrontal cortex, and inferior parietal gyrus. The alpha desynchronization effect was also localized to the pre‐ and post‐central gyri. The present study demonstrates a connection between infant sustained attention and EEG oscillatory activities.     

Investigating the modality specificity of response selection using a temporal flanker task

The neurocognitive architecture for response selection is uncertain. Some theorists suggest that it is mediated by an amodal central mechanism, whereas others propose a set of independent control mechanisms. In a functional neuroimaging experiment, we investigated the nature of response selection by examining how its underlying brain mechanisms are affected by stimulus modality. To do this, we used a modified flanker task, in which the target and flanker (distractor) stimuli differed in time rather than space, making it accessible for both visual and auditory stimuli. As in the traditional flanker task, larger reaction times were observed for incongruent than congruent trials (i.e., a congruency effect) for both modalities. Congruency affected brain activation for both modalities in prefrontal cortex, parietal cortex, and the putamen. Modality-dependent activation was found in additional prefrontal and parietal regions for the visual modality and in left inferior prefrontal cortex for the auditory modality. Modality-dependent activity specifically related to response congruency was also found in sensory cortical regions. These data suggest that modality affects the brain regions throughout the cortex mediating response selection even for conceptually identical stimuli and tasks. They are consistent with the hypothesis that (at least partially) independent brain networks mediate response selection and that input modality may be a powerful factor for organizing neural activity to support task performance.     

The Cognitive Demands of Gait Retraining in Runners: An EEG Study

Abstract

High impact forces during running have been associated with tibial stress injuries. Previous research has demonstrated increasing step rate will decrease impact forces during running. However, no research has determined the cognitive demand of gait retraining. The primary purpose was to determine the cognitive demand and effectiveness of field-based gait retraining. We hypothesized that in-field gait retraining would alter running mechanics without increasing cognitive workload as measured by EEG following learning. Runners with a history of tibial injury completed a gait retraining protocol which included a baseline run, retraining phase, practice phase, and re-assessment following retraining protocol. Results demonstrated an increase in the theta, beta, and gamma power within prefrontal cortex during new learning and corresponding return to baseline following skill acquisition and changes across alpha, beta, gamma, mu, and theta in the motor cortex (p < .05). In the midline superior parietal cortex, spectral power was greater for theta activity during new learning with a corresponding alpha suppression. Overall, the results demonstrated the use of EEG as an effective tool to measure cognitive demand for implicit motor learning and the effectiveness of in-field gait retraining.     

Exploring the effects of EEG signals on collision cases happening in the process of young drivers’ braking

Detecting mental states in drivers offers an opportunity to reduce accidents by triggering alerts and signaling the need for rest or renewed focus. Here we used electroencephalography (EEG) to measure brain signals in young drivers operating a driving simulator to detect mental states and predict accidents. We measured reaction times to unexpected hazardous events and correlated them with EEG signals measured from the frontal, parietal, and temporal cortices as well as the central sulcus (corresponding to motor cortex). We found that EEG signals in the relative beta (power in beta (13–30 Hz) relative to total power of the EEG (0.5–30 Hz)), alpha/delta, alpha/theta, beta/delta, beta/theta frequency bands were higher for collisions than successful collision avoidance, and that the key decision-making period is the 2nd second before braking. Importantly, a decision tree classifier trained on these neural signals predicted collision avoidance outcomes. Then based on random forest model, we extracted three critical neural signals (beta/delta_frontal, relative beta_parietal and relative beta_central Sulcus) to classify collision avoidance outcomes. Our findings suggest measuring EEG during driving may provide useful signals for enhancing driver safety.     

几何图形类比推理的ERP研究

该研究以几何图形作为实验材料,测定14名硕士研究生在完成两种类比推理任务（大小变化和颜色变化）和其基线任务时的事件相关电位（ERP）,探讨类比推理过程的脑内时程动态变化。研究发现,两种推理任务所诱发的波形基本一致,而推理任务与其基线任务之间的ERP波形存在显著差异,两种基线任务之间的ERP波形也存在显著差异;类比推理的加工过程是有阶段性的,即编码潍断、映射、得出结论,研究结果进一步支持了Sternberg的成分理论;推断和映射这两个类比推理所特有的加工阶段都有其对应的脑机制,图式推断阶段主要激活的是前额皮层和双侧的顶叶皮层,类比映射和调整阶段主要激活的是左半球的颞叶、额叶和中央顶。     

When senses meet functions: an amodal stage in conceptual processing

Research has shown that concepts are associated with modality-specific features widely distributed in the brain and that semantic hubs or convergence zones may exist to mediate or integrate distributed representations. Although much neuropsychological and neuroimaging literature has provided support for the existence of hubs/convergence zones from the spatial perspective, opinions differ as to whether the representations in the hubs/convergence zones are modality-specific or amodal. The current ERP study aimed to explore whether there is an amodal stage in conceptual processing from the temporal perspective. Participants were presented with prime-target pairs and were asked to judge whether the prime (a sensory or functional feature) could be an attribute of the target (a noun in a natural or artifactual category). The results revealed that a semantic hub or convergence zone may be reached no later than 350–450?ms in conceptual processing and that the representations in the hub may be amodal.     

Neural correlates of feigned memory impairment are distinguishable from answering randomly and answering incorrectly: an fMRI and behavioral study

Previous functional magnetic resonance imaging (fMRI) studies have identified activation in the prefrontal-parietal-sub-cortical circuit during feigned memory impairment when comparing with truthful telling. Here, we used fMRI to determine whether neural activity can differentiate between answering correctly, answering randomly, answering incorrectly, and feigned memory impairment. In this study, 12 healthy subjects underwent block-design fMRI while they performed digit task of forced-choice format under four conditions: answering correctly, answering randomly, answering incorrectly, and simulated feigned memory impairment. There were three main results. First, six areas, including the left prefrontal cortex, the left superior temporal lobe, the right postcentral gyrus, the right superior parietal cortex, the right superior occipital cortex, and the right putamen, were significantly modulated by condition type. Second, for some areas, including the right superior parietal cortex, the right postcentral gyrus, the right superior occipital cortex, and the right putamen, brain activity was significantly greater in feigned memory impairment than answering randomly. Third, for the areas including the left prefrontal cortex and the right putamen, brain activity was significantly greater in feigned memory impairment than answering incorrectly. In contrast, for the left superior temporal lobe, brain activity was significantly greater in answering incorrectly than feigned memory impairment. The results suggest that neural correlates of feigned memory impairment are distinguishable from answering randomly and answering incorrectly in healthy subjects.