The pain matrix reloaded: a salience detection system for the body

Neuroimaging and neurophysiological studies have shown that nociceptive stimuli elia salience detection system for the bodycit responses in an extensive cortical network including somatosensory, insular and cingulate areas, as well as frontal and parietal areas. This network, often referred to as the "pain matrix", is viewed as representing the activity by which the intensity and unpleasantness of the perception elicited by a nociceptive stimulus are represented. However, recent experiments have reported (i) that pain intensity can be dissociated from the magnitude of responses in the "pain matrix", (ii) that the responses in the "pain matrix" are strongly influenced by the context within which the nociceptive stimuli appear, and (iii) that non-nociceptive stimuli can elicit cortical responses with a spatial configuration similar to that of the "pain matrix". For these reasons, we propose an alternative view of the functional significance of this cortical network, in which it reflects a system involved in detecting, orienting attention towards, and reacting to the occurrence of salient sensory events. This cortical network might represent a basic mechanism through which significant events for the body's integrity are detected, regardless of the sensory channel through which these events are conveyed. This function would involve the construction of a multimodal cortical representation of the body and nearby space. Under the assumption that this network acts as a defensive system signaling potentially damaging threats for the body, emphasis is no longer on the quality of the sensation elicited by noxious stimuli but on the action prompted by the occurrence of potential threats

DEVELOPMENTAL FMRI STUDY: FACE AND OBJECT RECOGNITION

Visual processing, though seemingly automatic, is complex. Typical humansprocess objects and faces routinely. Yet, when a disease or disorder disrupts face andobject recognition, the effects are profound. Because of its importance and complexity,visual processing has been the subject of many adult functional imaging studies.However, relatively little is known about the development of the neural organization andunderlying cognitive mechanisms of face and object recognition. The current projectused functional magnetic resonance imaging (fMRI) to identify maturational changes inthe neural substrates of face and object recognition in 5-8 year olds, 9-11 year olds, andadults. A passive face and object viewing task revealed cortical shifts in the faceresponsiveloci of the ventral processing stream (VPS), an inferior occipito-temporalregion known to function in higher visual processing. Older children and adults recruitedmore anterior regions of the ventral processing stream than younger children. Toinvestigate the potential cognitive basis for these developmental changes, researchersimplemented a shape-matching task with parametric variations of shape overlap,structural similarity (SS), in stimulus pairs. VPS regions sensitive to high SS emerged inolder children and adults. Younger children recruited no structurally-sensitive regions inthe VPS. Two right hemisphere VPS regions were sensitive to maturational changes inSS. A comparison of face-responsive regions from the passive viewing task and the VPSSS regions did not reveal overlap. Though SS drives organization of the VPS, it did notexplain the cortical shifts in the neural substrates for face processing. In addition to VPSregions, results indicated additional maturational SS changes in frontal, parietal, andcerebellar regions. Based on these findings, further analyses were conducted to quantifyand qualify maturational changes in face and object processing throughout the brain.Results indicated developmental changes in activation extent, signal magnitude, andlateralization of face and object recognition networks. Collectively, this project supportsa developmental change in visual processing between 5-8 years and 9-11 years of age.Chapters Four through Six provide an in-depth discussion of the implications of thesefindings

Functional and Neural Mechanisms of Out-of-Body Experiences: Importance of Retinogeniculo-Cortical Oscillations

Current research on the various forms of autoscopic phenomena addresses the clinical and neurological correlates of out-of-body experiences, autoscopic hallucinations,and heautoscopy. Yet most of this research is based on functional magnetic resonance imaging results and focuses predominantly on abnormal cortical activity. Previously we proposed that visual consciousness resulted from the dynamic retinogeniculo-cortical oscillations, such that the photoreceptors dynamically integrated with visual and other vision-associated cortices, and was theorized to be mapped out by photoreceptor discs and rich retinal networks which synchronized with the retinotopic mapping and the associated cortex. The feedback from neural input that is received from the thalamus and cortex via retinogeniculo-cortical oscillations and sent to the retina is multifold higher than feed-forward input to the cortex. This can effectively translate into out-of-body experiences projected onto the screen formed by the retina as it is perceived via feedback and feed-forward oscillations from the reticular thalamic nucleus, or “internal searchlight”. This article explores the role of the reticular thalamic nucleus and the retinogeniculo-cortical oscillations as pivotal internal components in vision and various autoscopic phenomena

Social Distance Evaluation in Human Parietal Cortex

Across cultures, social relationships are often thought of, described, and acted out in terms of physical space (e.g. “close friends” “high lord”). Does this cognitive mapping of social concepts arise from shared brain resources for processing social and physical relationships? Using fMRI, we found that the tasks of evaluating social compatibility and of evaluating physical distances engage a common brain substrate in the parietal cortex. The present study shows the possibility of an analytic brain mechanism to process and represent complex networks of social relationships. Given parietal cortex's known role in constructing egocentric maps of physical space, our present findings may help to explain the linguistic, psychological and behavioural links between social and physical space

Distilling the neural correlates of conscious somatosensory perception

The ability to consciously perceive the world profoundly defines our lives as human beings. Somehow, our brains process information in a way that allows us to become aware of the images, sounds, touches, smells, and tastes surrounding us. Yet our understanding of the neurobiological processes that generate perceptual awareness is very limited. One of the most contested questions in the neuroscientific study of conscious perception is whether awareness arises from the activity of early sensory brain regions, or instead requires later processing in widespread supramodal networks. It has been suggested that the conflicting evidence supporting these two perspectives may be the result of methodological confounds in classical experimental tasks. In order to infer participants’ perceptual awareness in these tasks, they need to report the contents of their perception. This means that the neural signals underlying the emergence of perceptual awareness often cannot be dissociated from pre- and postperceptual processes. Consequently, some of the previously observed effects may not be correlates of awareness after all but instead may have resulted from task requirements. In this thesis, I investigate this possibility in the somatosensory modality. To scrutinise the task dependence of the neural correlates of somatosensory awareness, I developed an experimental paradigm that controls for the most common experimental confounds. In a somatosensory-visual matching task, participants were required to detect electrical target stimuli at ten different intensity levels. Instead of reporting their perception directly, they compared their somatosensory percepts to simultaneously presented visual cues that signalled stimulus presence or absence and then reported a match or mismatch accordingly. As a result, target detection was decorrelated from working memory and reports, the behavioural relevance of detected and undetected stimuli was equated, the influence of attentional processes was mitigated, and perceptual uncertainty was varied in a controlled manner. Results from a functional magnetic resonance imaging (fMRI) study and an electroencephalography (EEG) study showed that, when controlled for task demands, the neural correlates of somatosensory awareness were restricted to relatively early activity (~150 ms) in secondary somatosensory regions. In contrast, late activity (>300 ms) indicative of processing in frontoparietal networks occurred irrespective of stimulus awareness, and activity in anterior insular, anterior cingulate, and supplementary motor cortex was associated with processing perceptual uncertainty and reports. These results add novel evidence to the early-local vs. late-global debate and favour the view that perceptual awareness emerges at the level of modality-specific sensory cortices.Die Fähigkeit zur bewussten Wahrnehmung bestimmt maßgeblich unser Selbstbild als Menschen. Unser Gehirn verarbeitet Informationen auf eine Weise, die es uns ermöglicht, uns der Bilder, Töne, Berührungen, Gerüche und Geschmäcker, die uns umgeben, bewusst zu werden. Unser Verständnis davon, wie neurobiologische Prozesse diese bewusste Wahrnehmung erzeugen, ist jedoch noch sehr begrenzt. Eine der umstrittensten Fragen in der neurowissenschaftlichen Erforschung des perzeptuellen Bewusstseins besteht darin, ob die bewusste Wahrnehmung aus der Aktivität früher sensorischer Hirnregionen entsteht, oder aber die spätere Prozessierung in ausgedehnten supramodalen Netzwerken erfordert. Eine mögliche Erklärung für die widersprüchlichen Ergebnisse, die diesen beiden Perspektiven zugrunde liegen, wird in methodologischen Störfaktoren vermutet, die in klassischen experimentellen Paradigmen auftreten können. Um auf die Wahrnehmung der Versuchspersonen schließen zu können, müssen diese den Inhalt ihrer Wahrnehmung berichten. Das führt dazu, dass neuronale Korrelate bewusster Wahrnehmung häufig nicht sauber von prä- und postperzeptuellen Prozessen getrennt werden können. Folglich könnten einige der zuvor beobachteten Effekte, anstatt tatsächlich bewusste Wahrnehmung widerzuspiegeln, aus den Anforderungen experimenteller Paradigmen entstanden sein. In dieser Arbeit untersuche ich diese Möglichkeit in der somatosensorischen Modalität. Um zu überprüfen, inwiefern neuronale Korrelate bewusster somatosensorischer Wahrnehmung von den Anforderungen experimenteller Aufgaben abhängen, habe ich ein Paradigma entwickelt, dass die häufigsten experimentellen Störfaktoren kontrolliert. In einer somatosensorisch-visuellen Vergleichsaufgabe mussten die Versuchspersonen elektrische Zielreize in zehn verschiedenen Intensitätsstufen detektieren. Anstatt diese jedoch direkt zu berichten, sollten sie ihre somatosensorischen Perzepte mit gleichzeitig präsentierten visuellen Symbolen vergleichen, die entweder Reizanwesenheit oder -abwesenheit signalisierten. Entsprechend wurde dann eine Übereinstimmung oder Nichtübereinstimmung berichtet. Dadurch wurde die Reizwahrnehmung von Arbeitsgedächtnis und Berichterstattung dekorreliert, die Verhaltensrelevanz detektierter und nicht detektierter Reize gleichgesetzt, der Einfluss von Aufmerksamkeitsprozessen reduziert und die mit der Detektion verbundene Unsicherheit auf kontrollierte Weise variiert. Die Ergebnisse aus einer funktionellen Magnetresonanztomographie (fMRT)-Studie und einer Elektroenzephalographie (EEG)-Studie zeigen, dass die neuronalen Korrelate bewusster somatosensorischer Wahrnehmung auf relativ frühe Aktivität (~150 ms) in sekundären somatosensorischen Regionen beschränkt sind, wenn experimentelle Störfaktoren kontrolliert werden. Im Gegensatz dazu trat späte Aktivität (>300 ms), die auf die Verarbeitung in frontoparietalen Netzwerken hindeutet, unabhängig von der Reizwahrnehmung auf, und Aktivität im anterioren insulären, anterioren cingulären und supplementär-motorischen Kortex war mit der Verarbeitung von Detektionsunsicherheit und der Berichterstattung verbunden. Diese Ergebnisse liefern neue Erkenntnisse zur Debatte um die Relevanz früher, lokaler vs. später, globaler Hirnaktivität und unterstützen die Ansicht, dass perzeptuelles Bewusstsein in modalitätsspezifischen sensorischen Kortizes entsteht

Neuronal correlates of full and partial visual conscious perception

Stimuli may induce only partial consciousness—an intermediate between null and full consciousness—where the presence but not identity of an object can be reported. The differences in the neuronal basis of full and partial consciousness are poorly understood. We investigated if evoked and oscillatory activity could dissociate full from partial conscious perception. We recorded human cortical activity with magnetoencephalography (MEG) during a visual perception task in which stimulus could be either partially or fully perceived. Partial consciousness was associated with an early increase in evoked activity and theta/low-alpha-band oscillations while full consciousness was also associated with late evoked activity and beta-band oscillations. Full from partial consciousness was dissociated by stronger evoked activity and late increase in theta oscillations that were localized to higher-order visual regions and posterior parietal and prefrontal cortices. Our results reveal both evoked activity and theta oscillations dissociate partial and full consciousness.Peer reviewe

Common Neural Systems Associated with the Recognition of Famous Faces and Names: An Event-Related fMRI Study

Person recognition can be accomplished through several modalities (face, name, voice). Lesion, neurophysiology and neuroimaging studies have been conducted in an attempt to determine the similarities and differences in the neural networks associated with person identity via different modality inputs. The current study used event-related functional-MRI in 17 healthy participants to directly compare activation in response to randomly presented famous and non-famous names and faces (25 stimuli in each of the four categories). Findings indicated distinct areas of activation that differed for faces and names in regions typically associated with pre-semantic perceptual processes. In contrast, overlapping brain regions were activated in areas associated with the retrieval of biographical knowledge and associated social affective features. Specifically, activation for famous faces was primarily right lateralized and famous names were left-lateralized. However, for both stimuli, similar areas of bilateral activity were observed in the early phases of perceptual processing. Activation for fame, irrespective of stimulus modality, activated an extensive left hemisphere network, with bilateral activity observed in the hippocampi, posterior cingulate, and middle temporal gyri. Findings are discussed within the framework of recent proposals concerning the neural network of person identification

Temporally Graded Activation of Neocortical Regions in Response to Memories of Different Ages

The temporally graded memory impairment seen in many neurobehavioral disorders implies different neuroanatomical pathways and/or cognitive mechanisms involved in storage and retrieval of memories of different ages. A dynamic interaction between medial-temporal and neocortical brain regions has been proposed to account for memory\u27s greater permanence with time. Despite considerable debate concerning its time-dependent role in memory retrieval, medial-temporal lobe activity has been well studied. However, the relative participation of neocortical regions in recent and remote memory retrieval has received much less attention. Using functional magnetic resonance imaging, we demonstrate robust, temporally graded signal differences in posterior cingulate, right middle frontal, right fusiform, and left middle temporal regions in healthy older adults during famous name identification from two disparate time epochs. Importantly, no neocortical regions demonstrated greater response to older than to recent stimuli. Our results suggest a possible role of these neocortical regions in temporally dating items in memory and in establishing and maintaining memory traces throughout the lifespan. Theoretical implications of these findings for the two dominant models of remote memory functioning (Consolidation Theory and Multiple Trace Theory) are discussed

Modulation of emotional appraisal by false physiological feedback during fMRI

BACKGROUND James and Lange proposed that emotions are the perception of physiological reactions. Two-level theories of emotion extend this model to suggest that cognitive interpretations of physiological changes shape self-reported emotions. Correspondingly false physiological feedback of evoked or tonic bodily responses can alter emotional attributions. Moreover, anxiety states are proposed to arise from detection of mismatch between actual and anticipated states of physiological arousal. However, the neural underpinnings of these phenomena previously have not been examined. METHODOLOGY/PRINCIPAL FINDINGS We undertook a functional brain imaging (fMRI) experiment to investigate how both primary and second-order levels of physiological (viscerosensory) representation impact on the processing of external emotional cues. 12 participants were scanned while judging face stimuli during both exercise and non-exercise conditions in the context of true and false auditory feedback of tonic heart rate. We observed that the perceived emotional intensity/salience of neutral faces was enhanced by false feedback of increased heart rate. Regional changes in neural activity corresponding to this behavioural interaction were observed within included right anterior insula, bilateral mid insula, and amygdala. In addition, right anterior insula activity was enhanced during by asynchronous relative to synchronous cardiac feedback even with no change in perceived or actual heart rate suggesting this region serves as a comparator to detect physiological mismatches. Finally, BOLD activity within right anterior insula and amygdala predicted the corresponding changes in perceived intensity ratings at both a group and an individual level. CONCLUSIONS/SIGNIFICANCE Our findings identify the neural substrates supporting behavioural effects of false physiological feedback, and highlight mechanisms that underlie subjective anxiety states, including the importance of the right anterior insula in guiding second-order "cognitive" representations of bodily arousal state

Modulation of emotional appraisal by false physiological feedback during fMRI

BACKGROUND James and Lange proposed that emotions are the perception of physiological reactions. Two-level theories of emotion extend this model to suggest that cognitive interpretations of physiological changes shape self-reported emotions. Correspondingly false physiological feedback of evoked or tonic bodily responses can alter emotional attributions. Moreover, anxiety states are proposed to arise from detection of mismatch between actual and anticipated states of physiological arousal. However, the neural underpinnings of these phenomena previously have not been examined. METHODOLOGY/PRINCIPAL FINDINGS We undertook a functional brain imaging (fMRI) experiment to investigate how both primary and second-order levels of physiological (viscerosensory) representation impact on the processing of external emotional cues. 12 participants were scanned while judging face stimuli during both exercise and non-exercise conditions in the context of true and false auditory feedback of tonic heart rate. We observed that the perceived emotional intensity/salience of neutral faces was enhanced by false feedback of increased heart rate. Regional changes in neural activity corresponding to this behavioural interaction were observed within included right anterior insula, bilateral mid insula, and amygdala. In addition, right anterior insula activity was enhanced during by asynchronous relative to synchronous cardiac feedback even with no change in perceived or actual heart rate suggesting this region serves as a comparator to detect physiological mismatches. Finally, BOLD activity within right anterior insula and amygdala predicted the corresponding changes in perceived intensity ratings at both a group and an individual level. CONCLUSIONS/SIGNIFICANCE Our findings identify the neural substrates supporting behavioural effects of false physiological feedback, and highlight mechanisms that underlie subjective anxiety states, including the importance of the right anterior insula in guiding second-order "cognitive" representations of bodily arousal state