Synesthesia: When colors count

A tacitly held assumption in synesthesia research is the unidirectionality of digit-color associations. This notion is based on synesthetes' report that digits evoke a color percept, but colors do not elicit any numerical impression. In a random color generation task, we found evidence for an implicit co-activation of digits by colors, a finding that constrains neurological theories concerning cross-modal associations in general and synesthesia in particular.

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.

The development of a new measure for the assessment of psychopathology in adults with intellectual disability

BACKGROUND

People with intellectual disability (ID) and untreated psychiatric disorder lead unnecessarily difficult and unhappy lives. The prevalence of mental illness in children and adults with ID is greater than that found in the general population. A carer-completed checklist of psychopathology that could be used with both children and adults would help identify those individuals with ID most likely to have a mental health problem, help ensure that they receive the limited services that are usually available and also assist the process of clinical assessment, diagnosis and management.

METHOD

This research aimed to develop a reliable and valid carer-completed checklist of psychopathology for adults with ID by redeveloping an existing measure for children with ID, the Developmental Behaviour Checklist (DBC-P). The new checklist, The Developmental Behaviour Checklist for Adults (DBC-A) was devised by changing, deleting and adding to DBC-P items. Reliability studies were conducted with paid and family carers, and DBC-A scores were compared with the results from two other measures of psychopathology.

RESULTS

One DBC-P item was deleted, seven items changed and 12 items added. The psychometric properties of this new checklist, the DBC for Adults with ID (DBC-A), were investigated and found to be satisfactory. Intraclass correlations for test-retest and inter-rater reliability ranged from 0.72 to 0.85, and concurrent validity with two measures of emotional and behavioural disturbance was satisfactory.

CONCLUSIONS

The carer-completed DBC-A provides a broad and comprehensive survey of the emotional and behavioural problems of adults with ID. It has satisfactory psychometric properties and therefore can be used with confidence in clinical, research and service settings, and its development allows continuous assessment of psychopathology across the lifespan for all people with ID.

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.

The anterior cingulate cortex contains distinct areas dissociating external from self-administered painful stimulation: a parametric fMRI study

The anterior cingulate cortex (ACC) has a pivotal role in human pain processing by integrating sensory, executive, attentional, emotional, and motivational components of pain. Cognitive modulation of pain-related ACC activation has been shown by hypnosis, illusion and anticipation. The expectation of a potentially noxious stimulus may not only differ as to when but also how the stimulus is applied. These combined properties led to our hypothesis that ACC is capable of distinguishing external from self-administered noxious tactile stimulation. Thermal contact stimuli with noxious and non-noxious temperatures were self-administered or externally applied at the resting right hand in a randomized order. Two additional conditions without any stimulus-eliciting movements served as control conditions to account for the certainty and uncertainty of the impending stimulus. Calculating the differences in the activation pattern between self-administered and externally generated stimuli revealed three distinct areas of activation that graded with perceived stimulus intensity: (i) in the posterior ACC with a linear increase during external but hardly any modulation for the self-administered stimulation, (ii) in the midcingulate cortex with activation patterns independent of the mode of application and (iii) in the perigenual ACC with increasing activation during self-administered but decreasing activation during externally applied stimulation. These data support the functional segregation of the human ACC: the posterior ACC may be involved in the prediction of the sensory consequences of pain-related action, the midcingulate cortex in pain intensity coding and the perigenual ACC is related to the onset uncertainty of the impending stimuli.

Psychometric schizotypy modulates levodopa effects on lateralized lexical decision performance

Emergence of psychotic thought has been related to a breakdown in left-hemisphere language dominance. Dopamine (DA) is implicated in both psychotic pathology and modulation of the semantic system. The present study explored whether controlled DA administration modulates basic language functions: (1) in general and/or (2) as a function of schizophrenia-associated thought. Forty healthy men performed a tachistoscopic lexical decision task. Participants' performance was also analyzed as a function of their positive (magical ideation, MI) and negative (physical anhedonia, PHYSAN) schizotypal features. Half of the subjects received 200 mg levodopa, the other half a placebo. Our findings showed that pharmacological treatment per se did not influence task performance, but influenced laterality patterns as a function of participants' schizotypal features. In the placebo, but not in the levodopa group, right hemisphere language contribution increased as a function of increasing MI scores. In the levodopa, but not in the placebo group, superior left hemisphere lexical decision performance was related to increasing PHYSAN scores. The findings from both substance groups suggest that in the healthy brain, a DA agonist restores left-hemispheric dominance for language by reducing right-hemispheric contribution with respect to a positive schizotypal trait and by increasing left-hemispheric specialization with respect to a negative schizotypal trait. We conjecture that the healthy brain compensates through intact neurochemical mechanisms an increased DA concentration, in particular for persons with elevated positive psychotic-like features.

Brain State-dependent Functional Hemispheric Specialization in Men but not in Women

Hemispheric specialization is reliably demonstrated in patients with unilateral lesions or disconnected hemispheres, but is inconsistent in healthy populations. The reason for this paradox is unclear. We propose that functional hemispheric specialization in healthy participants depends upon functional brain states at stimulus arrival (FBS). Brain activity was recorded from 123 surface electrodes while 22 participants (11 women) performed lateralized lexical decisions (left hemisphere processing) on neutral and emotional (right hemisphere processing) words. We determined two classes of stable FBS, one with right anterior-left posterior orientations (RA-LP maps) and one with left anterior-right posterior orientations (LA-RP maps). Results show that functional hemispheric specialization is dependent upon the class of FBS and gender. Of those with LA-RP maps, only men showed a strong emotional word advantage (EWA) after left visual field (right hemisphere) presentation, but no EWA after right visual field (left hemisphere) presentation. Subsequent to all other brain states, there was an almost equal EWA after presentation to either visual field. Only about half of the FBS in men led to the pattern of functional hemispheric specialization. We suggest that 'split-brain' research may be marginally describable by a model, but only in exceptional situations, while in connected brains this functional hemispheric specialization is only one of many dynamic states.

Levodopa reverses gait asymmetries related to anhedonia and magical ideation

Animals and men turn preferentially away from the hemisphere with the more active dopamine (DA) system. Consistent with the idea of a right-hemispheric hyperdopaminergia in schizophrenia, a leftsided turning bias was described for unmedicated psychotic patients. We investigated the modulating role of DA and schizophrenia-like thought on whole-body turns in a controlled double-blind study. The number of veers to either side when walking blindfolded straight ahead (20 meter) was assessed in 40 healthy righthanded men (20 men received levodopa, the remaining participants placebo). Side preferences were analyzed in terms of individuals' positive (Magical Ideation, MI) and negative (Physical Anhedonia, PhysAn) schizotypal features. In the placebo group, increasing MI scores were related to increasing left-sided veering and increasing PhysAn scores were related to increasing right-sided veering. In the levodopa group, this relationship between preferred veering side and type of schizotypy was reversed. The finding in the placebo group suggests an association between MI and a relative right-hemispheric hyperdopaminergia. Unexpectedly, levodopa did not enhance this veering bias, but reversed it, suggesting that psychosis-protective mechanisms exist in the healthy positive "schizotypic" brain. Also unexpectedly, levodopa made "anhedonics" veer like "magics" after placebo, suggesting that DA agonists suppress negative schizotypal symptoms.

Compound measure of hand-foot-eye preference masked opposite turning behavior in healthy right-handers and non-right-handers: technical comment on Mohr et al. (2003)

A previous article reported opposite turning behavior in right-handers and non-right-handers (C. Mohr. T. Landis, H. S. Bracha, & P. Brugger, 2003). This observation appears contradictory to the 1st study on long-term spontaneous turning behavior in healthy participants (H. S. Bracha, D. J. Seitz, J. Otemaa, & S. D. Click, 1987). These latter authors found a complex interaction between hemispheric dominance, preferred turning side, and sex. C. Mohr et al. (2003) argued that the differentiation of the population in hemisphere-dominant groups by a compound measure of hand-foot-eye preference might have masked their recent finding. Thus, this commentary presents a reanalysis of the original data set (H. S. Bracha et al., 1987). Replicating recent observation, right-handers preferred left-sided turns; and non-righthanders, right-sided turns. This replication strengthens the proposition that handedness and turning behavior might depend on interhemispheric dopamine asymmetries.

Nonstereotyped responding in positive schizotypy after a single dose of levodopa

Stereotyped behavior and left-sided orientation biases, associated with the dopamine (DA) system, were observed in populations of the schizophrenia spectrum disorders. We investigated whether heightened DA concentrations influence both side biases and stereotyped responding in a visuo-motor computer task, in which 90, 180, and 270 degrees rotated objects had to be brought into a target position. To account for the role of the schizophrenia spectrum, task performance was also analyzed as a function of healthy participants' high or low magical ideation (MI), a positive schizotypal feature. The first 36 participants (20 women) remained substance free. In a second sample, 20 men received levodopa and 20 men a placebo in a double-blind procedure. Results showed that high MI scorers responded more stereotyped than low MI scorers, without being specifically biased towards the left side. Rotation preferences toward one or the other side made high MI scorers less flexible for objects efficiently to be rotated into the opposite direction. This inflexibility may reflect impaired left hemisphere functioning. Unexpectedly, in the levodopa group, high MI scorers performed superior to low MI scorers. Since DA actions appear to follow an inverted U-shape function, the 'low' performing high MI scorers profited from the enhanced DA availability. Our observation in the levodopa group points to a dissociation between schizotypy and schizophrenia: while cognitive improvement in schizophrenia can occur after treatment with atypical neuroleptic agents, in our positive schizotypal participants a DA agonist resulted in improved task performance. This dissociation may point to protective neurochemical mechanisms preventing healthy schizotypes from developing full-blown psychotic symptoms.

Cerebellar neural responses related to actively and passively applied noxious thermal stimulation in human subjects: a parametric fMRI study

Cerebellar activation is consistently found during noxious stimulation but little is known about its pain-related specificity. Under natural circumstances noxious stimuli are actively or passively delivered with concomitant tactile sensory stimulation. Using fMRI we therefore studied pain-related cerebellar activation with innocuous and noxious thermal stimuli in a parametric design taking motor execution as confounding factor into account. With respect to psychophysical pain ratings anterior vermal and ipsilateral hemispheric lobule VI activation was parametrically modulated for stimulus intensity in actively but not in passively elicited thermal stimulation. The cerebellum seems to be capable of distinguishing active from passive painful stimuli.

Electrical neuroimaging reveals early generator modulation to emotional words

Functional electrical neuroimaging investigated incidental emotional word processing. Previous research suggests that the brain may differentially respond to the emotional content of linguistic stimuli pre-lexically (i.e., before distinguishing that these stimuli are words). We investigated the spatiotemporal brain mechanisms of this apparent paradox and in particular whether the initial differentiation of emotional stimuli is marked by different brain generator configurations using high-density, event-related potentials. Such would support the existence of specific cerebral resources dedicated to emotional word processing. A related issue concerns the possibility of right-hemispheric specialization in the processing of emotional stimuli. Thirteen healthy men performed a go/no-go lexical decision task with bilateral word/non-word or non-word/non-word stimulus pairs. Words included equal numbers of neutral and emotional stimuli, but subjects made no explicit discrimination along this dimension. Emotional words appearing in the right visual field (ERVF) yielded the best overall performance, although the difference between emotional and neutral words was larger for left than for right visual field presentations. Electrophysiologically, ERVF presentations were distinguished from all other conditions over the 100-140 ms period by a distinct scalp topography, indicative of different intracranial generator configurations. A distributed linear source estimation (LAURA) of this distinct scalp potential field revealed bilateral lateral-occipital sources with a right hemisphere current density maximum. These data support the existence of a specialized brain network triggered by the emotional connotation of words at a very early processing stage.

[Quantitative ultrasound for the diagnosis of osteoporosis]

Quantitative ultrasound (QUS) methods are promising tools for the assessment of the bone status in osteoporosis. The techniques are based on changes in speed and amplitude of a broadband ultrasound signal propagating through the bone. However, ultrasound propagation through the anisotropic bone is complex and cannot be described in a simple way. The devices are easy to use, inexpensive, portable, do not use ionizing radiation, and therefore have advantages compared to conventional densitometry. This review discusses the technical basics, current research, clinical applications, points of weakness, and future prospects of QUS. For better understanding ultrasound propagation through bone is visualized with a simulation software.

Human side preferences in three different whole-body movement tasks☆

Animals turn away from the hemisphere with the more active dopamine (DA) system. For humans, a similar relationship has been assumed. However, results from independent studies were obtained from different tasks and indicated different side preferences. To investigate side preferences between different tasks within the same subject, we assessed in 36 healthy research participants (20 women) (1) long-term spontaneous turning (number of 360 degree turns during 20 h), (2) veering (lateral deviations during walking blindfolded straight forward) and (3) stepping (deviations while stepping blindfolded on a given spot) behavior. We observed a left-sided preference for long-term spontaneous turning behavior and no significant side preference for veering and stepping behavior. The absence of consistent side preferences suggests that DA does not equally control lateralized whole-body movements. We propose that visual control enhanced left-sided movement preferences, probably through an enhanced contribution of the right hemisphere to visuo-spatial behavior. Recently, we reported [Neurosci. Lett. 339 (2003) 115] that levodopa supplementation decreases right-sided veering tendencies, while stepping behavior was unaffected by substance intake. We suggest that veering tendencies, which appeared equally pronounced in either direction, are under dopaminergic control as long as attention is directed towards extrapersonal space. Side preferences in lateralized whole-body movement tasks are thus neither comparable between tasks nor within subjects. We conclude that experimental parameters such as visuo-spatial control and spatial task demands (veering is directed to extrapersonal space and stepping to peripersonal space) determine whether or not the DA system is involved.

The Ashbya gossypii Genome as a Tool for Mapping the Ancient Saccharomyces cerevisiae Genome

We have sequenced and annotated the genome of the filamentous ascomycete Ashbya gossypii. With a size of only 9.2 megabases, encoding 4718 protein-coding genes, it is the smallest genome of a free-living eukaryote yet characterized. More than 90% of A. gossypii genes show both homology and a particular pattern of synteny with Saccharomyces cerevisiae. Analysis of this pattern revealed 300 inversions and translocations that have occurred since divergence of these two species. It also provided compelling evidence that the evolution of S. cerevisiae included a whole genome duplication or fusion of two related species and showed, through inferred ancient gene orders, which of the duplicated genes lost one copy and which retained both copies.

3 Tesla-MRT: Der Erfolg h�herer Feldst�rken

The recent development of 3 Tesla MRI (3T MRI) has been fueled by promise of increased signal-to-noise ratio(SNR). Many are excited about the opportunity to not only use the increased SNR for clearer images, but also the chance to exchange it for better resolution or faster scans. These possibilities have caused a rapid increase in the market for 3T MRI, where the faster scanning tips an already advantageous economic outlook in favor of the user. As a result, the global market for 3T has grown from a research only market just a few years ago to an ever-increasing clinically oriented customer base. There are, however, significant obstacles to 3T MRI presented by the physics at higher field strengths. For example, the T1 relaxation times are prolonged with increasing magnet field strength. Further, the increased RF-energy deposition (SAR), the larger the chemical shift and the stronger susceptibility effect have to be considered as challenges. It is critical that one looks at both the advantages and disadvantages of using 3T. While there are many issues to address aand a number of different methods for doing so, to properly tackle each of these concerns will take time and effort on the part od researchers and clinicians. The optimization of 3T MRI scanning will have to be a combined effort, though much of the work to date has been in neuroimaging. Multiple applications have been explored in addition to clinical anatomical imaging, where resolution is improved showing structure in the brain never seen before in human MRI. Body and cardiac imaging provide a great challenge but are also achievable at 3T. As an example, the full range of clinical applications currently achieved on today's state-of-the-art 1.5T cardiac MR scanners has also been demonstrated at 3T. In the body, the full range of contrast is available over large fields of view allowing whole liver studies in the clinic or, as needed, one may choose a smaller field of view for high-resolution imaging of the pancreas. The ability to increase resolution for musculoskeletal imaging has provided previously unseen detail. Bone structure, cartilage, and tendons and ligaments can be clearly visualized and pathology more easily detected due to an increased image quality. As the increase in field strength continues, a push to look at 7T has begun. The design philosophy is to keep the system as similar as possible, while changing only the frequency-dependent components. To date, both animal and human imaging have been performed on a whole body 7T scanner. Results show promise for both detailed imaging and functional MRI, but the road ahead is too long to be able to predict where it will end. The move toward higher field strengths is an exciting adventure in which 3T plays the role of trailblazer.

Localisation of “unseen” visual stimuli: Blindsight in normal observers?

We developed two experiments on normal subjects to simulate “blindsight”, i.e., above chance localization performance of visual stimuli without phenomenal awareness. In both experiments, visual targets were presented on a computer screen at one of six possible locations, followed by a metacontrast mask. Subjects (1) indicated whether they had seen the target stimulus or not, and (2) guessed at which location the stimulus had been presented. Fifty percent were blank trials. We found that even when subjects did not acknowledge the presence of a stimulus, they nevertheless guessed its location with above chance accuracy. Apparent motion improved both detection and localization performance. Subjective confidence was related to stimulus presence and localisation performance. Thus, simulated blindsight appeared to be based on residual conscious awareness.

Magical ideation modulates spatial behavior

Previous research has found that animals as well as persons with psychotic disorders preferentially orient away from the cerebral hemisphere with the more active dopamine system. This study investigated the modulation of spatial behavior by a mode of thinking reminiscent of the positive symptoms of psychosis. In a non-treatment-seeking sample of healthy volunteers (20 women and 16 men), the authors assessed the lateral biases in turning and veering behavior and in line bisection as a function of their magical ideation, that is, a mild form of schizotypy. Across tasks, pronounced magical ideation was associated with reduced right-sided orientation preferences. This finding suggests a relative hyperdopaminergia of the right hemisphere as the biological basis of magical ideation.

Hyperfamiliarity for unknown faces after left lateral temporo-occipital venous infarction: a double dissociation with prosopagnosia

Right hemisphere dominance in face processing is well established and unilateral right inferior temporo-occipital damage can result in prosopagnosia. Here, we describe a 21-year-old right-handed woman with acute impairment in face recognition that selectively concerned unfamiliar faces, following a focal left lateral temporo-occipital venous infarct. She was severely impaired in discerning that unknown people seen in everyday life were unfamiliar, although she had no difficulty recognizing familiar people. Thus, she had no prosopagnosia, but abnormal 'hyperfamiliarity' for unknown faces. Her difficulty was not accompanied by delusions or deficits in discrimination, identification or memory for faces. Standard neuropsychological testing showed that her recognition of familiar faces was entirely normal. By contrast, her sense of personally knowing faces was severely impaired when unknown faces evoked weak signals of familiarity based on spurious cues, to the extent that she would misattribute fame to faces that were unknown but to which she had been incidentally exposed on a prior occasion. Priming experiments also revealed that, unlike normal subjects, she made familiarity judgements without accessing semantic identity representations. Moreover, in face recognition tests, she generally showed bias in that she relied more on right-hemisphere strategies to identify global traits and less on left-hemisphere processes compared with healthy subjects. This case provides novel evidence for a differential contribution of the two hemispheres to face recognition. Hyperfamiliarity for unknown faces might arise from an imbalance between reciprocal hemispheric functions in face recognition, with relative hypoactivation of left hemisphere processes but hyperactivation of right-hemisphere processes for retrieving stored associations about people, linking seen faces to representations of affective and personal relevance. Hence, abnormal bias in attributing some personal meaning to unknown faces could be evoked by spurious signals of familiarity based on irrelevant affective associations in the right hemisphere.

Human locomotion: levodopa keeps you straight

Locomotion depends on an intact dopamine system. This system seems to be functionally asymmetric, as evidenced by an asymmetric turning preference. Using a double-blind procedure, the effect of levodopa on the number of veers when walking blindfolded along a straight line (20 m) in the middle of a corridor was tested in 40 healthy dextral men. One group received 200 mg levodopa, while the other group received placebo. We found that (1). subjects veered less after levodopa than after placebo, and (2). improved straight-walking tendency was most prominent for the levodopa group which veered less often to the right side than the placebo group. These findings imply that spatial orientation skills improved under levodopa. We conjecture that a task-dependent dopamine demand during our task was satisfied by levodopa supplementation, and over-proportionately so by the right hemisphere.

Differential cerebellar activation related to perceived pain intensity during noxious thermal stimulation in humans: a functional magnetic resonance imaging study

Little is known about the cerebellar involvement in pain processing in spite of the fact that the cerebellum probably plays a crucial role in pain-related behavior. Using functional magnetic resonance imaging we examined the differential cerebellar activation in 18 healthy subjects in relation to their perceived pain-intensity of noxious and non-noxious thermal stimuli. In contrast to non-noxious (40 degrees C) stimuli, noxious (48.5 degrees C) stimuli revealed activation in the deep cerebellar nuclei, anterior vermis and bilaterally in the cerebellar hemispheric lobule VI. With the same noxious stimulus (48.5 degrees C) there was differential cerebellar activation depending on the perceived pain intensity: high pain intensity ratings were associated with activation in ipsilateral hemispheric lobule III-VI, deep cerebellar nuclei and in the anterior vermis (lobule III). This differential cerebellar activation pattern probably reflects not only somatosensory processing but also perceived pain intensity that may be important for cerebellar modulation of nociceptive circuits.