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Olaf Blanke

Publications and source records attributed to Olaf Blanke.

At least 19 recordsLinked to original sources
PubMed2007

Duration and not strength of activation in temporo-parietal cortex positively correlates with schizotypy.

Impaired self- and own body processing in patients with schizophrenia and individuals along the schizophrenia spectrum have been associated with dysfunctional cortical activation at the temporo-parietal junction. Here we investigated whether strength or duration of temporo-parietal junction activation during an own body processing task correlates with level of abnormal self-processing in healthy subjects as measured by the frequency of spontaneously experienced schizotypal body schema alterations (perceptual aberrations) and dissociative experiences. Participants carried out a mental imagery task with respect to their own body. Behavioral data and high density EEG were measured. EEG data were analyzed using evoked potential mapping and electrical neuroimaging. Participants completed two validated self-report questionnaires, one asking about perceptual aberration and one about dissociative experiences. The own body transformation task activated the right temporo-parietal junction at 310-390 ms. Participants' reaction times and duration of activation at the right temporo-parietal junction, but not its strength, were found to correlate positively with perceptual aberration scores. No relationship was found with dissociative experiences scores. Brain activations proceeding and following activation of the right temporo-parietal junction did not correlate with scores on either scale. The positive correlation between performance and right temporo-parietal activation in an own body transformation task with perceptual aberrations scores in our healthy population suggests that disturbances in self- and body processing in individuals along the schizophrenia spectrum might be due to prolonged, rather than stronger activation of the right temporo-parietal junction. We argue that this might reflect local pathology, pathologies in cortico-cortical connections and/or re-entry of top-down processing.

Adult↗
PubMed2006

Induction of an illusory shadow person.

Stimulation of a site on the brain's left hemisphere prompts the creepy feeling that somebody is close by. The strange sensation that somebody is nearby when no one is actually present has been described by psychiatric and neurological patients, as well as by healthy subjects, but it is not understood how the illusion is triggered by the brain. Here we describe the repeated induction of this sensation in a patient who was undergoing presurgical evaluation for epilepsy treatment, as a result of focal electrical stimulation of the left temporoparietal junction: the illusory person closely 'shadowed' changes in the patient's body position and posture. These perceptions may have been due to a disturbance in the multisensory processing of body and self at the temporoparietal junction.

Adult↗
PubMed2006

Neural basis of embodiment: distinct contributions of temporoparietal junction and extrastriate body area.

Embodiment, the sense of being localized within one's physical body, is a fundamental aspect of the self. Recently, researchers have started to show that self and body processing require distinct brain mechanisms, suggesting two posterior brain regions as key loci: the temporoparietal junction (TPJ), which is involved in self processing and multisensory integration of body-related information; and the extrastriate body area (EBA), which responds selectively to human bodies and body parts. Here we used evoked potential mapping and a distributed linear inverse solution to show that activations in EBA and TPJ code differentially for embodiment and self location, because the location and timing of brain activation depended on whether mental imagery is performed with mentally embodied (EBA) or disembodied (TPJ) self location. In a second experiment, we showed that only EBA activation, related to embodied self location, but not TPJ activation, related to disembodied self location, was modified by the subjects' body position during task performance (supine or sitting). This suggests that embodied self location and actual body location share neural mechanisms. Collectively, these data show that distributed brain activity at the EBA and TPJ as well as their timing are crucial for the coding of the self as embodied and as spatially situated within the human body.

Adult↗
PubMed2006

Neural mechanisms of embodiment: asomatognosia due to premotor cortex damage.

BACKGROUND: Patients with asomatognosia generally describe parts of their body as missing or disappeared from corporeal awareness. This disturbance is generally attributed to damage in the right posterior parietal cortex. However, recent neuroimaging and electrophysiological studies suggest that corporeal awareness and embodiment of body parts are instead linked to the premotor cortex of both hemispheres. PATIENT: We describe a patient with asomatognosia of her left arm due to damage in the right premotor and motor cortices. The patient's pathological embodiment for her left arm was associated with mild left somatosensory loss, mild frontal dysfunction, and a behavioral deficit in the mental imagery of human arms. CONCLUSION: Asomatognosia may also be associated with damage to the right premotor cortex.

Agnosia↗
PubMed2006

Polyopic heautoscopy: Case report and review of the literature.

Heautoscopy, i.e., the encounter with one's double, is a multimodal illusory reduplication of one's own body and self. In its polyopic form, more than one double is experienced. In the present article, we review fourteen published cases of polyopic heautoscopy and describe in detail the case of a 41-year-old man with polyopic heautoscopy resulting from a tumor in the insular region of the left temporal lobe. Our case is illustrative in several respects: (1) The patient's five doubles were all confined to the right hemispace. Laterality in this case is discussed with reference to previous cases of unilateral heautoscopy after focal brain damage, which generally do not show a hemispatial or hemispheric bias. (2) The patient's psychological affinity with his doubles, and also the extent of their echopraxia of his movements, decreased as a function of their perceived spatial distance from the patient's body, corroborating previous observations of associations between spatial and psychological phenomenologies during autoscopic phenomena. (3) While classical heautoscopy (the reduplication of a single body and self) is considered a breakdown in the integrative processes that enable us to identify our self with our body, the phenomenon of polyopic heautoscopy (a multiplication of body and self) points to the multiple mappings of the body, whose disintegration may give rise to the illusory experience of multiple selves.

Adult↗
PubMed2005

Out-of-body experience, heautoscopy, and autoscopic hallucination of neurological origin Implications for neurocognitive mechanisms of corporeal awareness and self-consciousness.

Autoscopic phenomena (AP) are rare illusory visual experiences during which the subject has the impression of seeing a second own body in extrapersonal space. AP consist of out-of-body experience (OBE), autoscopic hallucination (AH), and heautoscopy (HAS). The present article reviews and statistically analyzes phenomenological, functional, and anatomical variables in AP of neurological origin (n = 41 patients) that have been described over the last 100 years. This was carried out in order to further our understanding of the underlying mechanisms of AP, much as previous research into the neural bases of body part illusions has demystified these latter phenomena. Several variables could be extracted, which distinguish between or are comparable for the three AP providing testable hypotheses for subsequent research. Importantly, we believe that the scientific demystification of AP may be useful for the investigation of the cognitive functions and brain regions that mediate processing of the corporeal awareness and self consciousness under normal conditions.

Awareness↗
PubMed2005

Preattentive interference between touch and audition: a case study on multisensory alloesthesia.

Alloesthesia is a rare clinical condition that corresponds to a spatial disorder of stimulus localization, in which patients experience a given stimulus on the side opposite to the side of stimulation. Whereas it has been mostly described for unisensory stimulations, evidence of multisensory alloesthesia is only anecdotal. Here, we investigated a case of multisensory auditory-tactile alloesthesia. Our data suggest that auditory-tactile integration and multisensory alloesthesia not only depend on attentional mechanisms, but also on somatotopic preattentive mechanisms.

Acoustic Stimulation↗
PubMed2005

Linking out-of-body experience and self processing to mental own-body imagery at the temporoparietal junction.

The spatial unity of self and body is challenged by various philosophical considerations and several phenomena, perhaps most notoriously the "out-of-body experience" (OBE) during which one's visual perspective and one's self are experienced to have departed from their habitual position within one's body. Although researchers started examining isolated aspects of the self, the neurocognitive processes of OBEs have not been investigated experimentally to further our understanding of the self. With the use of evoked potential mapping, we show the selective activation of the temporoparietal junction (TPJ) at 330-400 ms after stimulus onset when healthy volunteers imagined themselves in the position and visual perspective that generally are reported by people experiencing spontaneous OBEs. Interference with the TPJ by transcranial magnetic stimulation (TMS) at this time impaired mental transformation of one's own body in healthy volunteers relative to TMS over a control site. No such TMS effect was observed for imagined spatial transformations of external objects, suggesting the selective implication of the TPJ in mental imagery of one's own body. Finally, in an epileptic patient with OBEs originating from the TPJ, we show partial activation of the seizure focus during mental transformations of her body and visual perspective mimicking her OBE perceptions. These results suggest that the TPJ is a crucial structure for the conscious experience of the normal self, mediating spatial unity of self and body, and also suggest that impaired processing at the TPJ may lead to pathological selves such as OBEs.

Adult↗
PubMed2005

The demystification of autoscopic phenomena: experimental propositions.

Autoscopic phenomena (AP) are rare, illusory visual experiences during which the subject has the impression of seeing a second own body in extrapersonal space. AP consist of out-of-body experience, autoscopic hallucination, and heautoscopy. Recent neurologic reports support the role of multisensory integration deficits of body-related information and vestibular dysfunctions in AP at the temporo-parietal junction. A caveat to test the underlying neurologic and cognitive mechanisms of AP has been their rare and spontaneous occurrence. Recent evidence linked AP to mental own-body imagery engaging brain mechanisms at the temporo-parietal junction. These recent observations open a new avenue for testing AP-related cognitive mechanisms in selected clinical and normal populations. We review evidence on several clinical syndromes (psychosis, depression, anxiety, depersonalization, body dysmorphic disorder), suggesting that some of these syndromes may relate to AP-proneness, thereby leading to testable propositions for future research on body and self processing in addition to AP.

Awareness↗
PubMed2005

Why revelations have occurred on mountains? Linking mystical experiences and cognitive neuroscience.

The fundamental revelations to the founders of the three monotheistic religions, among many other revelation experiences, had occurred on a mountain. These three revelation experiences share many phenomenological components like feeling and hearing a presence, seeing a figure, seeing lights, and feeling of fear. In addition, similar experiences have been reported by non-mystic contemporary mountaineers. The similarities between these revelations on mountains and their appearance in contemporary mountaineers suggest that exposure to altitude might affect functional and neural mechanisms, thus facilitating the experience of a revelation. Different functions relying on brain areas such as the temporo-parietal junction and the prefrontal cortex have been suggested to be altered in altitude. Moreover, acute and chronic hypoxia significantly affect the temporo-parietal junction and the prefrontal cortex and both areas have also been linked to altered own body perceptions and mystical experiences. Prolonged stay at high altitudes, especially in social deprivation, may also lead to prefrontal lobe dysfunctions such as low resistance to stress and loss of inhibition. Based on these phenomenological, functional, and neural findings we suggest that exposure to altitudes might contribute to the induction of revelation experiences and might further our understanding of the mountain metaphor in religion. Mystical and religious experiences are important not only to the mystic himself, but also to many followers, as it was indeed with respect to the leaders of the three monotheistic religions. Yet, concerning its subjective character, mystical experiences are almost never accessible to the scholars interested in examining them. The tools of cognitive neuroscience make it possible to approach religious and mystical experiences not only by the semantical analysis of texts, but also by approaching similar experiences in healthy subjects during prolonged stays at high altitude and/or in cognitive paradigms. Cognitive neurosciences, in turn, might profit from the research of mysticism in their endeavor to further our understanding of mechanisms of corporeal awareness and self consciousness.

Acclimatization↗
PubMed2005

The out-of body experience: precipitating factors and neural correlates.

Out-of-body experiences (OBEs) are defined as experiences in which a person seems to be awake and sees his body and the world from a location outside his physical body. More precisely, they can be defined by the presence of the following three phenomenological characteristics: (i) disembodiment (location of the self outside one's body); (ii) the impression of seeing the world from an elevated and distanced visuo-spatial perspective (extracorporeal, but egocentric visuo-spatial perspective); and (iii) the impression of seeing one's own body (autoscopy) from this perspective. OBEs have fascinated mankind from time immemorial and are abundant in folklore, mythology, and spiritual experiences of most ancient and modern societies. Here, we review some of the classical precipitating factors of OBEs such as sleep, drug abuse, and general anesthesia as well as their neurobiology and compare them with recent findings on neurological and neurocognitive mechanisms of OBEs. The reviewed data suggest that OBEs are due to functional disintegration of lower-level multisensory processing and abnormal higher-level self-processing at the temporo-parietal junction. We argue that the experimental investigation of the interactions between these multisensory and cognitive mechanisms in OBEs and related illusions in combination with neuroimaging and behavioral techniques might further our understanding of the central mechanisms of corporal awareness and self-consciousness much as previous research about the neural bases of complex body part illusions such as phantom limbs has done.

Body Image↗
PubMed2005

The out-of-body experience: disturbed self-processing at the temporo-parietal junction.

Folk psychology postulates a spatial unity of self and body, a "real me" that resides in one's body and is the subject of experience. The spatial unity of self and body has been challenged by various philosophical considerations but also by several phenomena, perhaps most notoriously the "out-of-body experience" (OBE) during which one's visuo-spatial perspective and one's self are experienced to have departed from their habitual position within one's body. Here the authors marshal evidence from neurology, cognitive neuroscience, and neuroimaging that suggests that OBEs are related to a failure to integrate multisensory information from one's own body at the temporo-parietal junction (TPJ). It is argued that this multisensory disintegration at the TPJ leads to the disruption of several phenomenological and cognitive aspects of self-processing, causing illusory reduplication, illusory self-location, illusory perspective, and illusory agency that are experienced as an OBE.

Brain Mapping↗
PubMed2004

Letters lost in space: hemispace dependent handwriting errors.

Although handwriting is a daily life activity commonly attributed to the left hemisphere in the majority of right-handers, it is also known to require attentional and spatial mechanisms that rely on right hemispheric processing. The underlying spatial organization of handwriting in patients with right brain damage remains unresolved. Here we show in a patient with circumscribed right superior parietal damage that handwriting systematically depends on the hand's position in space with respect to her body-midline. Most importantly, handwriting in contralesional space not only leads to spatial but also to language errors. This suggests that the right hemisphere's role in handwriting may surpass its generally assumed purely spatial contribution. We discuss our results in term of co-registration between both cerebral hemispheres in language processing.

Brain Damage, Chronic↗
PubMed2004

Cortical motion deafness.

The extent to which the auditory system, like the visual system, processes spatial stimulus characteristics such as location and motion in separate specialized neuronal modules or in one homogeneously distributed network is unresolved. Here we present a patient with a selective deficit for the perception and discrimination of auditory motion following resection of the right anterior temporal lobe and the right posterior superior temporal gyrus (STG). Analysis of stimulus identity and location within the auditory scene remained intact. In addition, intracranial auditory evoked potentials, recorded preoperatively, revealed motion-specific responses selectively over the resected right posterior STG, and electrical cortical stimulation of this region was experienced by the patient as incoming moving sounds. Collectively, these data present a patient with cortical motion deafness, providing evidence that cortical processing of auditory motion is performed in a specialized module within the posterior STG.

Acoustic Stimulation↗
PubMed2003

Out-of-body experience and autoscopy of neurological origin.

During an out-of-body experience (OBE), the experient seems to be awake and to see his body and the world from a location outside the physical body. A closely related experience is autoscopy (AS), which is characterized by the experience of seeing one's body in extrapersonal space. Yet, despite great public interest and many case studies, systematic neurological studies of OBE and AS are extremely rare and, to date, no testable neuroscientific theory exists. The present study describes phenomenological, neuropsychological and neuroimaging correlates of OBE and AS in six neurological patients. We provide neurological evidence that both experiences share important central mechanisms. We show that OBE and AS are frequently associated with pathological sensations of position, movement and perceived completeness of one's own body. These include vestibular sensations (such as floating, flying, elevation and rotation), visual body-part illusions (such as the illusory shortening, transformation or movement of an extremity) and the experience of seeing one's body only partially during an OBE or AS. We also find that the patient's body position prior to the experience influences OBE and AS. Finally, in five patients, brain damage or brain dysfunction is localized to the temporo-parietal junction (TPJ). These results suggest that the complex experiences of OBE and AS represent paroxysmal disorders of body perception and cognition (or body schema). The processes of body perception and cognition, and the unconscious creation of central representation(s) of one's own body based on proprioceptive, tactile, visual and vestibular information-as well as their integration with sensory information of extrapersonal space-is a prerequisite for rapid and effective action with our surroundings. Based on our findings, we speculate that ambiguous input from these different sensory systems is an important mechanism of OBE and AS, and thus the intriguing experience of seeing one's body in a position that does not coincide with its felt position. We suggest that OBE and AS are related to a failure to integrate proprioceptive, tactile and visual information with respect to one's own body (disintegration in personal space) and by a vestibular dysfunction leading to an additional disintegration between personal (vestibular) space and extrapersonal (visual) space. We argue that both disintegrations (personal; personal-extrapersonal) are necessary for the occurrence of OBE and AS, and that they are due to a paroxysmal cerebral dysfunction of the TPJ in a state of partially and briefly impaired consciousness.

Body Image↗
PubMed2003

Direction of saccadic and smooth eye movements induced by electrical stimulation of the human frontal eye field: effect of orbital position.

The present study reports on the direction of saccadic and smooth eye movements, which were induced electrically from the human dorsolateral frontal cortex including the human frontal eye field (FEF). The eye position prior to stimulation was varied in order to examine its effect on induced eye movement direction. The five patients of the study underwent invasive presurgical evaluation for pharmacoresistant epilepsy. The present data show that the direction of electrically induced eye movements was always contralateral and either horizontal or oblique upward if the eye started from the primary position. The elicited direction was changed if the eyes started from an eccentric position. The frequency of oblique eye movements was increased and oblique downward responses were induced, which were not observed if the eye started from the primary position. This was found for saccades and, especially, for smooth eye movements. Head movements, which were almost exclusively induced with saccades, did not depend on initial orbital position. Four conclusions can be drawn. Firstly, saccades and smooth eye movements induced from the human dorsolateral cortex including the human FEF have the same directional bias. Secondly, the frequent upward responses and the absence of downward responses induced from the primary position suggests either a more numerous or a more superficial representation of neurons that code for the former direction. Thirdly, at some sites the direction of saccades and smooth eye movements varies depending on the initial orbital position. Since these directional changes were observed without changes in eye-head coordination, our data suggest that stimulation of the FEF might evoke goal-directed saccades or interferes with a resettable saccade integrator. Fourthly, human studies that investigate eye movements induced from the lateral frontal cortex need to control eye position prior to stimulation.

Adolescent↗