Balkin, T. J., Braun, A. R., Wesensten, N. J., Jeffries, K., Varga, M., Baldwin, P., Belenky, G., & Herscovitch, P. (2002). The process of awakening: a PET study of regional brain activity patterns mediating the re-establishment of alertness and consciousness. Brain, 125(10), 2308-2319.
Awakening from sleep entails rapid re-establishment of consciousness followed by the relatively slow (20-30 min later) re-establishment of alertness--a temporal dissociation that facilitates specification of the physiological underpinnings of each of these facets of the awakening process. H215O PET was used to assess changes in regional cerebral blood flow (rCBF) upon awakening from stage 2 sleep. Cerebral blood flow (CBF) was most rapidly re-established in centrencephalic regions (e.g. brainstem and thalamus), suggesting that the reactivation of these regions underlies the re-establishment of conscious awareness. Across the ensuing 15 min of wakefulness, further increases in CBF were evident primarily in anterior cortical regions, suggesting that the dissipation of sleep inertia effects (post-awakening performance and alertness deficits) is effected by reactivation of these regions. Concomitant shifts in correlation patterns of regional brain activity across the post-awakening period [in particular, a waning negative correlation between prefrontal cortex and mesencephalic reticular formation (RF) activity, and a waxing positive correlation between prefrontal cortex and ventromedial caudate nucleus (CAUD) activity] suggest that the post- awakening reversal of sleep inertia effects may be mediated by more than mere reactivation--it may also involve the functional reorganization of brain activity. Conversely, stable post-awakening correlations--such as those found between the anterior cingulate cortex (ACC) and most other brain regions--may denote the pattern of functional connectivity that underlies consciousness itself.
Berthoz, S., Armony, J. L., Blair, R. J. R., & Dolan, R. J. (2002). An fMRI study of intentional and unintentional (embarrassing) violations of social norms. Brain, 125(8), 1696- 1708.
The aim of this investigation was to identify neural systems supporting the processing of intentional and unintentional transgressions of social norms. Using event-related fMRI, we addressed this question by comparing neural responses to stories describing normal behaviour, embarrassing situations or violations of social norms. Processing transgressions of social norms involved systems previously reported to play a role in representing the mental states of others, namely medial prefrontal and temporal regions. In addition, the processing of transgressions of social norms involved systems previously found to respond to aversive emotional expressions (in particular angry expressions); namely lateral orbitofrontal cortex (Brodmann area 47) and medial prefrontal cortex. The observed responses were similar for both intentional and unintentional social norm violations, albeit more pronounced for the intentional norm violations. These data suggest that social behavioural problems in patients with frontal lobe lesions or fronto-temporal dementia may be a consequence of dysfunction within the systems identified in light of their possible role in processing whether particular social behaviours are, or are not, appropriate.
Blanke, Ortigue, S., Landis, T., & Seeck, M. (2002). Neuropsychology: Stimulating illusory own-body perceptions. Nature, 419(September 19), 269 - 270.
'Out-of-body' experiences (OBEs) are curious, usually brief sensations in which a person's consciousness seems to become detached from the body and take up a remote viewing position. Here we describe the repeated induction of this experience by focal electrical stimulation of the brain's right angular gyrus in a patient who was undergoing evaluation for epilepsy treatment. Stimulation at this site also elicited illusory transformations of the patient's arm and legs (complex somatosensory responses) and whole-body displacements (vestibular responses), indicating that out-of-body experiences may reflect a failure by the brain to integrate complex somatosensory and vestibular information
Blanke, O., Landis, T., Spinelli, L., & Seeck, M. (2004). Out-of-body experience and autoscopy of neurological origin. Brain, 127(2), 243-258.
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
Goel, V., & Dolan, R. J. (2001). The functional anatomy of humor:
segregating cognitive and affective components. Nature
Neuroscience, 4(3), 237-238.
Humor, a unique human characteristic, is critical in thought,
communication and social interaction. Successful jokes involve a
cognitive juxtaposition of mental sets, followed by an affective
feeling of amusement; we isolated these two components of humor by
using event-related fMRI on subjects who listened to auditorily
present-ed semantic and phonological jokes (puns) and indicated
whether or not they found the items amusing. Our findings suggest
that where-as there are modality-specific pathways for processing the
juxtaposition of mental sets necessary for the appreciation of jokes,
a common component of humor is expressed in activity in medial
ventral prefrontal cortex, a region involved in reward processing.(Aka medial orbitofrontal cortex)
Hunter, M. D., Griffiths, T. D., Farrow, T. F. D., Zheng, Y., Wilkinson, I. D., Hegde, N., Woods, W., Spence, S. A., & Woodruff, P. W. R. (2003). A neural basis for the perception of voices in external auditory space. Brain, 126, 161-169.
We used functional imaging of normal subjects to identify the neural substrate for the perception of voices in external auditory space. This fundamental process can be abnormal in psychosis, when voices that are not true external auditory objects (auditory verbal hallucinations) may appear to originate in external space. The perception of voices as objects in external space depends on filtering by the outer ear. Psychoses that distort this process involve the cerebral cortex. Functional magnetic resonance imaging was carried out on 12 normal subjects using an inside-the-scanner simulation of 'inside head' and 'outside head' voices in the form of typical auditory verbal hallucinations. Comparison between the brain activity associated with the two conditions allowed us to test the hypothesis that the perception of voices in external space ('outside head') is subserved by a temperoparietal network comprising association auditory cortex posterior to Heschl's gyrus [planum temporale (PT)] and inferior parietal lobule. Group analyses of response to 'outside head' versus 'inside head' voices showed significant activation solely in the left PT. This was demonstrated in three experiments in which the predominant lateralization of the stimulus was to the right, to the left or balanced. These findings suggest a critical involvement of the left PT in the perception of voices in external space that is not dependent on precise spatial location. Based on this, we suggest a model for the false perception of externally located auditory verbal hallucinations.
Johnson, S. C., Baxter, L. C., Wilder, L. S., Pipe, J. G., Heiserman, J. E., & Prigatano, G. P. (2002). Neural correlates of self-reflection. Brain, 125(8), 1808-1814.
The capacity to reflect on one's sense of self is an important component of self-awareness. In this paper, we investigate some of the neurocognitive processes underlying reflection on the self using functional MRI. Eleven healthy volunteers were scanned with echoplanar imaging using the blood oxygen level-dependent contrast method. The task consisted of aurally delivered statements requiring a yes-no decision. In the experimental condition, participants responded to a variety of statements requiring knowledge of and reflection on their own abilities, traits and attitudes (e.g. I forget important things', I'm a good friend', I have a quick temper'). In the control condition, participants responded to statements requiring a basic level of semantic knowledge (e.g. 'Ten seconds is more than a minute', You need water to live'). The latter condition was intended to control for auditory comprehension, attentional demands, decision-making, the motoric response, and any common retrieval processes. Individual analyses revealed consistent anterior medial prefrontal and posterior cingulate activation for all participants. The overall activity for the group, using a random- effects model, occurred in anterior medial prefrontal cortex (t = 13.0, corrected P = 0.05; x, y, z, 0, 54, 8, respectively) and the posterior cingulate (t = 14.7, P = 0.02; x, y, z, -2, -62, 32, respectively; 967 voxel extent). These data are consistent with lesion studies of impaired awareness, and suggest that the medial prefrontal and posterior cingulate cortex are part of a neural system subserving self-reflective thought.
McGonigle, D. J., Hanninen, R., Salenius, S., Hari, R., Frackowiak, R. S. J., & Frith, C. D. (2002). Whose arm is it anyway? An fMRI case study of supernumerary phantom limb. Brain, 125, 1265-1274.
Under normal circumstances, information from a number of sources is combined to compute a unitary percept of the body. However, after pathology these influences may be perceived simultaneously, resulting in multiple dissociated conscious representations. In a recent paper, we described subject E.P., a right-handed female stroke patient with a right frontomesial lesion who sporadically experiences a supernumerary 'ghost' left arm that occupies the previous position of the real left arm after a delay of 60-90 s. We used a delayed response paradigm with functional MRI to examine the haemodynamic correlates of E.P.'s illusion. Comparison of periods of time during scanning when the ghost arm was present against when it was not revealed a single cluster (9 voxels, t = 5.11, P < 0.012 corrected for multiple comparisons) located on the right medial wall in the supplementary motor area ('SMA proper'). Our results suggest that areas traditionally classified as part of the motor system can influence the conscious perception of the body. We propose that, as a consequence of her injury, E.P. is aware of the position of the phantom limb in this 'action space' while also continuing to be aware of the true position of her real limb on the basis of afferent somatosensory information.
Schneider, P., Scherg, M., Dosch, H. G., Specht, H. J., Gutschalk, A., & Rupp, A. (2002). Morphology of Heschl's gyrus reflects enhanced activation in the auditory cortex of musicians. Nature Neuroscience, 5(7), 688-694.
Using magnetoencephalography (MEG), we compared the processing of sinusoidal tones in the auditory cortex of 12 non-musicians, 12 professional musicians and 13 amateur musicians. We found neurophysiological and anatomical differences between groups. In professional musicians as compared to non-musicians, the activity evoked in primary auditory cortex 19-30 ms after stimulus onset was 102% larger, and the gray matter volume of the anteromedial portion of Heschl's gyrus was 130% larger. Both quantities were highly correlated with musical aptitude, as measured by psychometric evaluation. These results indicate that both the morphology and neurophysiology of Heschl's gyrus have an essential impact on musical aptitude.
Small, D. M., Zatorre, R. J., Dagher, A., Evans, A. C., & Jones-Gotman, M. (2001). Changes in brain activity related to eating chocolate - From pleasure to aversion. Brain, 124, 1720- 1733.
We performed successive (H2O)-O-15-PET scans on volunteers as they ate chocolate to beyond satiety. Thus, the sensory stimulus and act (eating) were held constant while the reward value of the chocolate and motivation of the subject to eat were manipulated by feeding. Non- specific effects of satiety (such as feelings of fullness and autonomic changes) were also present and probably contributed to the modulation of brain activity. After eating each piece of chocolate, subjects gave ratings of how pleasant/ unpleasant the chocolate was and of how much they did or did not want another piece of chocolate. Regional cerebral blood flow was then regressed against subjects' ratings. Different groups of structures were recruited selectively depending on whether subjects were eating chocolate when they were highly motivated to eat and rated the chocolate as very pleasant [subcallosal region, caudomedial orbitofrontal cortex (OFC), insula/operculum, striatum and midbrain] or whether they ate chocolate despite being satiated (parahippocampal gyrus, caudolateral OFC and prefrontal regions). As predicted, modulation was observed in cortical chemosensory areas, including the insula and caudomedial and caudolateral OFC, suggesting that the reward value of food is represented here. Of particular interest, the medial and lateral caudal OFC showed opposite patterns of activity. This pattern of activity indicates that there may be a functional segregation of the neural representation of reward and punishment within this region. The only brain region that was active during both positive and negative compared with neutral conditions was the posterior cingulate cortex. Therefore, these results support the hypothesis that there are two separate motivational systems: one orchestrating approach and another avoidance behaviours.
Piefke, M., Weiss, P. H., Zilles, K., Markowitsch, H. J., & Fink, G. R. (2003). Differential remoteness and emotional tone modulate the neural correlates of autobiographical memory. Brain, 126, 650-668.
Autobiographical memory relies on complex interactions between
episodic memory contents, associated emotions and a sense of self-
continuity along the time axis of one's life history. The neural
correlates underlying autobiographical memory are known to primarily
comprise areas of prefrontal cortex, medial and lateral temporal
cortex, as well as posterior cingulate and retrosplenial cortex. By
contrast, the effect of encoding and/or storage parameters such as
the emotional tone of the memories retrieved or the length of the
time-interval between the initial encoding of information and
retrieval remains to be clarified. Using blocked design functional
MRI and statistical parametric mapping, we investigated the impact of
remoteness (factor 1: recent, remote) and emotional valence (factor
2: positive, negative) on the neural correlates of autobiographical
memory retrieval. Changes in neural activity (P < 0.05, corrected)
related to autobiographical memory retrieval (irrespective of
remoteness and emotional tone) relative to baseline were observed
bilaterally in medial and lateral temporal, temporal-occipital,
posterior cingulate and frontal cortices. Recent (relative to remote)
memories were associated with differentially increased neural
activity bilaterally in the retrosplenial cortex and the hippocampal
region, whereas remote (relative to recent) memories did not show any
statistically significant differential neural activations. Positive
(relative to negative) memories bilaterally activated the
orbitofrontal cortex, the temporal pole, as well as medial temporal
areas, with the activation peak being in the entorhinal region. By
contrast, negative (relative to positive) memories differentially
increased neural activity in the right middle temporal gyrus only.
The data suggest differential functional roles for temporal,
prefrontal and retrosplenial regions during autobiographical memory
retrieval depending on the remoteness and the emotional valence of
the memories retrieved. In particular, our findings support the
'classic' model of long-term memory processing, which suggests a time-
limited differential involvement of the hippocampus in memory
consolidation. Interestingly, the observation of such a time-
dependent involvement of the hippocampal region in memory
consolidation corresponds to the course of retrograde amnesia
observed in demented patients, with the loss of recent memories
appearing during early stages of the disease when conspicuous
neurofibrillary changes are restricted mainly to the hippocampal and
parahippocampal regions. Only during later stages, as the
neurofibrillary changes spread out to neocortical association areas,
do remote memories also become impaired. We conclude that the brain
regions involved in autobiographical memory retrieval are influenced
by the triggered memories' emotional significance and their
relationship to the individual time axis.
van Zuijen, T. L., Sussman, E., Winkler, I., Naatanen, R., & Tervaniemi, M. (2004). Grouping of sequential sounds - An event-related potential study comparing musicians and nonmusicians. Journal of Cognitive Neuroscience, 16(2), 331-338.
It is believed that auditory processes governing grouping and segmentation of sounds are automatic and represent universal aspects of music perception (e.g., they are independent of the listener's musical skill). The present study challenges this view by showing that musicians and nonmusicians differ in their ability to preattentively group consecutive sounds. We measured event-related potentials (ERPs) from professional musicians and nonmusicians who were presented with isochronous tone sequences that they ignored. Four consecutive tones in a sequence could be grouped according to either pitch similarity or good continuation of pitch. Occasionally, the tone-group length was violated by a deviant tone. The mismatch negativity (MMN) was elicited to the deviants in both subject groups when the sounds could be grouped based on pitch similarity. In contrast, MMN was only elicited in musicians when the sounds could be grouped according to good continuation of pitch. These results suggest that some forms of auditory grouping depend on musical skill and that not all aspects of auditory grouping are universal.
Vuilleumier, P., Chicherio, C., Assal, F., Schwartz, S., Slosman, D., & Landis, T. (2001). Functional neuroanatomical correlates of hysterical sensorimotor loss. Brain, 124, 1077- 1090.
Hysterical conversion disorders refer to functional neurological deficits such as paralysis, anaesthesia or blindness not caused by organic damage but associated with emotional 'psychogenic' disturbances. Symptoms are not intentionally feigned by the patients whose handicap often outweighs possible short-term gains. Neural concomitants of their altered experience of sensation and volition are still not known. We assessed brain functional activation in seven patients with unilateral hysterical sensorimotor loss during passive vibratory stimulation of both hands, when their deficit was present and 2-4 months later when they had recovered. Single photon emission computerized tomography using Tc-99m-ECD revealed a consistent decrease of regional cerebral blood flow in the thalamus and basal ganglia contralateral to the deficit. Independent parametric mapping and principal component statistical analyses converged to show that such subcortical asymmetries were present in each subject. Importantly, contralateral basal ganglia and thalamic hypoactivation resolved after recovery. Furthermore, lower activation in contralateral caudate during hysterical conversion symptoms predicted poor recovery at followup. These results suggest that hysterical conversion deficits may entail a functional disorder in striatothalamocortical circuits controlling sensorimotor function and voluntary motor behaviour. Basal ganglia, especially the caudate nucleus, might be particularly well situated to modulate motor processes based on emotional and situational cues from the limbic system. Remarkably, the same subcortical premotor circuits are also involved in unilateral motor neglect after organic neurological damage, where voluntary limb use may fail despite a lack of true paralysis and intact primary sensorimotor pathways. These findings provide novel constraints for a modern psychobiological theory of hysteria.