Abraham Goldstein

The influence of stimulus deviance and novelty on the P300 and novelty P3.

This study examined the relationship between ERP components elicited by deviant stimuli by disentangling the P300 and Novelty P3 components, using spatiotemporal principal components analysis and a dense electrode array. The three-tone paradigm was used and the pitch attributes of the tones were systematically manipulated so as to map the amplitude of the ERP components on the stimulus context. A comparison was made between the components elicited by events in the three-stimulus, classical oddball, and novelty oddball paradigms. Responses to deviant stimuli consisted of independent and dissociable ERP components in the 400-600-ms time range: A parietal component (P300) that was larger for targets than rare nontargets and was affected by the difficulty of discrimination, a fronto-central component (Novelty P3) that was larger for novel tones and for rare nontargets in the difficult discrimination condition, and an additional anterior negative component responded similarly to all types of deviant stimuli.

Mindfulness-induced changes in gamma band activity – Implications for the default mode network, self-reference and attention

OBJECTIVE There is a growing scientific interest in mindfulness meditation (MM), yet its underlying neurophysiological mechanism is still uncertain. We investigated whether MM affects self-referential processing, associated with default mode network (DMN), either as short (state) - or long-term (trait) effects. METHODS Three levels of MM expertise were compared with controls (n=12 each) by electroencephalography (EEG). RESULTS DMN deactivation was identified during the transition from resting state to a time production task, as lower gamma (25-45 Hz) power over frontal and midline regions. MM practitioners exhibited a trait lower frontal gamma activity, related to narrative self-reference and DMN activity, as well as producing longer durations, these being negatively correlated with frontal gamma activity. Additionally, we found state increases in posterior gamma power, suggesting increased attention and sensory awareness. MM proficiency did not affect the results. CONCLUSIONS Gamma power over frontal midline areas reflects DMN activity. MM practitioners exhibit lower trait frontal gamma activity, as well as a state and trait increases in posterior gamma power, irrespective of practice proficiency. SIGNIFICANCE First, the DMN can be studied non-invasively by EEG. Second, MM induces from the early stages of practice neuroplasticity in self-referential and attentional networks.

Brainwaves are stethoscopes: ERP correlates of novel metaphor comprehension

The processing of unfamiliar metaphors was examined using event related potentials (ERPs). We compared the patterns of brain electrical activity elicited by processing two-word expressions denoting literal, conventional metaphoric, and novel metaphoric meaning, as well as unrelated word pairs. Participants performed a semantic judgment task in which they decided whether each word pair conveyed a meaningful expression. N400 amplitude to the second word of the pair varied as a function of expression type in a graded manner increasing from literal expressions to conventional metaphors, to novel metaphors and to unrelated pairs. N400s elicited by novel metaphors showed a right-biased scalp distribution as compared to those elicited by conventional metaphors. Novel metaphors also elicited a right-sided late negativity suggesting further attempts to integrate meaning in a non-literal fashion, a result that supports the sequential view of novel metaphor comprehension. These findings are consistent with recent brain imaging studies and complement them by adding the temporal dynamics dimension.

The impact of Internet interactivity and need for closure on consumer preference

Abstract The Internet is used by an ever-increasing number of people worldwide. However, there is little understanding of the interaction between Internet technology and the behavior of different human personality types. This article focuses on the impact of the need for closure on the desired level of interactivity of a given Website. For this experiment, four commercialized Websites were created: (1) flat—with no hyperlinks and no time pressure; (2) flat with time pressure; (3) interactive with no time pressure; and (4) interactive with time pressure. All of the Websites contained identical information presented in different ways. The interaction between need for closure as a personality variable and as a situational variable and level of interactivity of the Website as a variable on consumer behavior was examined. A 2 (high need for closure vs. low need for closure)×2 (time pressure vs. no time pressure)×2 (interactive vs. non-interactive Website) between-subjects design was used. One hundred and eighty-two experienced Web surfers took part in the experiment, and were randomly assigned to one of the Websites. After surfing they completed a questionnaire about their level of satisfaction with the Website, their willingness to purchase the product offered there, and their wish to return to the Website. It was predicted that people with a high need for closure would prefer a Website with fewer hyperlinks, while people with a low need for closure would prefer a Website containing more hyperlinks. Results confirmed our predictions with regard to the conditions without time pressure. In contrast, when participants were under time pressure, the results were completely reversed: People with a low need for closure preferred the flat Website and those with a high need for closure preferred an interactive Website. The implications of the results on Website design are discussed.

Semantic integration during metaphor comprehension in Asperger syndrome

Previous research indicates severe disabilities in processing figurative language in people diagnosed on the autism spectrum disorders. However, this aspect of language comprehension in Asperger syndrome (AS) specifically has rarely been the subject of formal study. The present study aimed to examine the possibility that in addition to their pragmatic deficits, the difficulties in the comprehension of metaphors in AS may be explained by deficient linguistic information processing. Specifically, we aimed to examine whether a deficient semantic integration process underlies the difficulties in metaphor comprehension frequently experienced by persons with AS. The semantic integration process of sixteen AS participants and sixteen matched controls was examined using event related potentials (ERPs). N400 amplitude served as an index for degree of effort invested in the semantic integration process of two-word expressions denoting literal, conventional metaphoric, and novel metaphoric meaning, as well as unrelated word pairs. Large N400 amplitudes for both novel and conventional metaphors demonstrated the greater difficulties in metaphor comprehension in the AS participants as compared to controls. Findings suggest that differences in linguistic information processing cause difficulties in metaphor comprehension in AS.

Dynamics of hemispheric activity during metaphor comprehension: Electrophysiological measures

Brain imaging studies have lead to conflicting findings regarding the involvement of the right hemisphere (RH) in metaphor comprehension. Some report more relative RH activation when processing figurative expressions but others have shown just the opposite. The inconsistencies might be a result of the low temporal resolution related to current brain imaging techniques which is insufficient to uncover patterns of hemispheric interaction that change over time. Event-related potentials and a source estimation technique (LORETA) were used to investigate such temporal interactions when processing two-word expressions denoting literal, conventional metaphoric, and novel metaphoric meaning, as well as unrelated word pairs. Participants performed a semantic judgment task in which they decided whether each word pair conveyed a meaningful expression. Our findings indicate that during comprehension of novel metaphors there are some stages of considerable RH involvement, mainly of the temporal and superior frontal areas. Although the processing mechanisms used for all types of expressions were similar and require both hemispheres, the relative contribution of each hemisphere at specific processing stages depended on stimulus type. Those stages correspond roughly to the N400 and LPC components which reflect semantic and contextual integration, respectively. The present study demonstrates that RH mechanisms are necessary, but not sufficient, for understanding metaphoric expressions. Both hemispheres work in concert in a complex dynamical pattern during literal and figurative language comprehension. Electrophysiological recordings together with source localization algorithms such as LORETA are a viable tool for measuring this type of activity patterns.

Alterations in the sense of time, space, and body in the mindfulness-trained brain: a neurophenomenologically-guided MEG study

Meditation practice can lead to what have been referred to as “altered states of consciousness.”One of the phenomenological characteristics of these states is a joint alteration in the sense of time, space, and body. Here, we set out to study the unique experiences of alteration in the sense of time and space by collaborating with a select group of 12 long-term mindfulness meditation (MM) practitioners in a neurophenomenological setup, utilizing first-person data to guide the neural analyses. We hypothesized that the underlying neural activity accompanying alterations in the sense of time and space would be related to alterations in bodily processing. The participants were asked to volitionally bring about distinct states of “Timelessness” (outside time) and “Spacelessness” (outside space) while their brain activity was recorded by MEG. In order to rule out the involvement of attention, memory, or imagination, we used control states of “Then” (past) and “There” (another place). MEG sensors evidencing alterations in power values were identified, and the brain regions underlying these changes were estimated via spatial filtering (beamforming). Particularly, we searched for similar neural activity hypothesized to underlie both the state of “Timelessness” and “Spacelessness.” The results were mostly confined to the theta band, and showed that: (1) the “Then”/“There” overlap yielded activity in regions related to autobiographic memory and imagery (right posterior parietal lobule (PPL), right precentral/middle frontal gyrus (MFG), bilateral precuneus); (2) “Timelessness”/“Spacelessness” conditions overlapped in a different network, related to alterations in the sense of the body (posterior cingulate, right temporoparietal junction (TPJ), cerebellum); and (3) phenomenologically-guided neural analyses enabled us to dissociate different levels of alterations in the sense of the body. This study illustrates the utility of employing experienced contemplative practitioners within a neurophenomenological setup for scientifically characterizing a self-induced altered sense of time, space and body, as well as the importance of theta activity in relation with these altered states.

Mindfulness-induced selflessness: a MEG neurophenomenological study

Contemporary philosophical and neurocognitive studies of the self have dissociated two distinct types of self-awareness: a “narrative” self-awareness (NS) weaving together episodic memory, future planning and self-evaluation into a coherent self-narrative and identity, and a “minimal” self-awareness (MS) focused on present momentary experience and closely tied to the sense of agency and ownership. Long-term Buddhist meditation practice aims at realization of a “selfless” mode of awareness (SL), where identification with a static sense of self is replaced by identification with the phenomenon of experiencing itself. NS-mediating mechanisms have been explored by neuroimaging, mainly fMRI, implicating prefrontal midline structures, but MS processes are not well characterized and SL even less so. To this end we tested 12 long-term mindfulness meditators using a neurophenomenological study design, incorporating both magnetoencephalogram (MEG) recordings and first person descriptions. We found that (1) NS attenuation involves extensive frontal, and medial prefrontal gamma band (60–80 Hz) power decreases, consistent with fMRI and intracranial EEG findings; (2) MS attenuation is related to beta-band (13–25 Hz) power decreases in a network that includes ventral medial prefrontal, medial posterior and lateral parietal regions; and (3) the experience of selflessness is linked to attenuation of beta-band activity in the right inferior parietal lobule. These results highlight the role of dissociable frequency-dependent networks in supporting different modes of self-processing, and the utility of combining phenomenology, mindfulness training and electrophysiological neuroimaging for characterizing self-awareness.

A Magnetoencephalographic Study of Face Processing: M170, Gamma-Band Oscillations and Source Localization

EEG studies suggested that the N170 ERP and Gamma‐band responses to faces reflect early and later stages of a multiple‐level face‐perception mechanism, respectively. However, these conclusions should be considered cautiously because EEG‐recorded Gamma may be contaminated by noncephalic activity such as microsaccades. Moreover, EEG studies of Gamma cannot easily reveal its intracranial sources. Here we recorded MEG rather than EEG, assessed the sources of the M170 and Gamma oscillations using beamformer, and explored the sensitivity of these neural manifestations to global, featural and configural information in faces. The M170 was larger in response to faces and face components than in response to watches. Scrambling the configuration of the inner components of the face even if presented without the face contour reduced and delayed the M170. The amplitude of MEG Gamma oscillations (30–70 Hz) was higher than baseline during an epoch between 230–570 ms from stimulus onset and was particularly sensitive to the configuration of the stimuli, regardless of their category. However, in the lower part of this frequency range (30–40 Hz) only physiognomic stimuli elevated the MEG above baseline. Both the M170 and Gamma were generated in a posterior‐ventral network including the fusiform, inferior‐occipital and lingual gyri, all in the right hemisphere. The generation of Gamma involved additional sources in the visual system, bilaterally. We suggest that the evoked M170 manifests a face‐perception mechanism based on the global characteristics of face, whereas the induced Gamma oscillations are associated with the integration of visual input into a pre‐existent coherent perceptual representation. Hum Brain Mapp, 2013.

Studying the default mode and its Mindfulness-induced changes using EEG functional connectivity

The default mode network (DMN) has been largely studied by imaging, but not yet by neurodynamics, using electroencephalography (EEG) functional connectivity (FC). mindfulness meditation (MM), a receptive, non-elaborative training is theorized to lower DMN activity. We explored: (i) the usefulness of EEG-FC for investigating the DMN and (ii) the MM-induced EEG-FC effects. To this end, three MM groups were compared with controls, employing EEG-FC (-MPC, mean phase coherence). Our results show that: (i) DMN activity was identified as reduced overall inter-hemispheric gamma MPC during the transition from resting state to a time production task and (ii) MM-induced a state increase in alpha MPC as well as a trait decrease in EEG-FC. The MM-induced EEG-FC decrease was irrespective of expertise or band. Specifically, there was a relative reduction in right theta MPC, and left alpha and gamma MPC. The left gamma MPC was negatively correlated with MM expertise, possibly related to lower internal verbalization. The trait lower gamma MPC supports the notion of MM-induced reduction in DMN activity, related with self-reference and mind-wandering. This report emphasizes the possibility of studying the DMN using EEG-FC as well as the importance of studying meditation in relation to it.