Functional dissociation between medial and lateral prefrontal cortical spatiotemporal activation in negative and positive emotions: a combined fMRI/MEG study

The orbitofrontal cortex has been cytoarchitectonically andconnectionally subdivided into a medial and a lateral part whichare assumed to subserve distinct functions in emotional processing.However the exact spatiotemporal mechanisms of negative andpositive emotional processing in medial and lateral orbitofrontalcortex remain unclear. We therefore investigated spatiotemporalorbitofrontal and prefrontal cortical activation patterns duringemotional stimulation in a combined fMRI/MEG study. We investigated10 healthy subjects, 5 women and 5 men. Positive and negativepictures from the International Affective Picture system (IAPS)were used for emotional stimulation, whereas neutral and graypictures were taken as control conditions. fMRI/MEG measurementscovered the whole frontal lobe and a time window between –2000and +200 ms around motor responses (right index finger extension)associated with each picture. Positively and negatively correlatedactivities were determined in various prefrontal/frontal corticalregions in fMRI. Isocontour maps and single dipoles in MEG wereanalyzed in 50 ms time windows ranging from –2000 to +200ms. Dipoles and fMR images were mapped on three-dimensionalanatomical MRI so that anatomical localization of single dipolesand regional fMRI activity could be compared. Both negativeand positive emotional conditions differed from non-emotionalcontrol conditions by strong orbitofrontal and lateral prefrontalactivation as well as by the presence of early magnetic fields(–1700 to +1100 ms). Negative emotional processing wascharacterized by strong medial orbitofrontal activation andearlier (–1700 ms), stronger and more medially orientedorbitofrontal dipoles. In contrast positive emotional processingshowed a rather strong activation in lateral prefrontal cortexwith later (–1500 ms), weaker and more laterally orientedorbito and prefrontal dipoles. Negative emotional processingcan be characterized by strong and early medial orbitofrontalcortical activation, whereas positive emotional processing showedrather later and weaker activation in lateral orbitofrontal/prefrontalcortex. Such a functional dissociation between medial and lateralorbito-frontal/prefrontal cortex during negative and positiveemotional processing lends further support to the assumptionof a functional subdivision in the orbitofrontal cortex.     

Dissociable cortical processing of recognizable and non-recognizable biological movement: analysing gamma MEG activity

Recognition of biological motion is one of the essential ingredients of human evolutionary survival. When biological motion is revealed solely by a set of light dots on the joints of an invisible human figure, the perceptual system reliably distinguishes it from similar configurations. Here, we assessed the changes in neuromagnetic cortical responses during visual perception of biological motion. Healthy humans saw a randomized set of stimuli consisting of a point-light canonical walker and a scrambled configuration in which the spatial positions of dots were randomly rearranged on the screen. In separate runs, configurations were presented either within an upright or inverted (180 degrees ) orientation in the image plane. Participants performed a one-back repetition task lifting a forefinger in response to the second of two consecutive identical stimuli of each type. Both recognizable upright and non-recognizable inverted walkers evoke enhancements in oscillatory gamma brain activity (25-30 Hz) over the left occipital cortices as early as 100 ms from stimulus onset. Only a recognizable upright walker, however, yields further consecutive peaks over the parietal (130 ms) and right temporal (170 ms) lobes. Scrambled displays do not elicit any increases in the gamma response. The stimulus-specific time course and topographic dynamics of cortical oscillatory activity indicate that the brain rapidly dissociates spatial coherence and meaning revealed through biological movement.     

Individual differences in error processing: a review and reanalysis of three event-related fMRI studies using the GO/NOGO task

Three previous studies using the GO/NOGO task were examined to characterize the pattern of functional activation seen during error-related processing. The large sample size (n = 44) also allowed investigation of the influence of individual differences in age, sex, self-reported absentmindedness and reaction speed on the level of activation. Errors were seen to activate a network of regions including the anterior cingulate cortex (ACC), pre-supplementary motor area (pre-SMA), bilateral insula, thalamus and right inferior parietal lobule. Split-half comparisons performed for each of the individual difference variables indicated greater ACC and pre-SMA activation for older subjects while slower responders showed greater activation in the parietal, lateral PFC, insula and ACC regions. Whereas males and females demonstrated equivalent levels of activation in both the ACC and insula, self-reported absentmindedness related to reduced activation in these regions. Our review of the current imaging literature on error-related activation indicates that, despite the use of a variety of other cognitive paradigms, the network of regions identified here is consistent with these previous studies, suggesting that these regions are critical to a 'general' error-related response. Furthermore, this response is, in part, influenced by individual differences in both demographic characteristics and behavioural performance.     

Influence of syllabic lengthening on semantic processing in spoken French: behavioral and electrophysiological evidence

The present work investigates the relationship between semantic and prosodic (metric) processing in spoken language under 2 attentional conditions (semantic and metric tasks) by analyzing both behavioral and event-related potential (ERP) data. Participants listened to short sentences ending in semantically and/or metrically congruous or incongruous trisyllabic words. In the metric task, ERP data showed that metrically incongruous words elicited both larger early negative and late positive components than metrically congruous words, thereby demonstrating the online processing of the metric structure of words. Moreover, in the semantic task, metrically incongruous words also elicited an early negative component with similar latency and scalp distribution as the classical N400 component. This finding highlights the automaticity of metrical structure processing. Moreover, it demonstrates that violations of a word's metric structure may hinder lexical access and word comprehension. This interpretation is supported by the behavioral data showing that participants made more errors for semantically congruous but metrically incongruous words when they were attending to the semantic aspects of the sentence. Finally, the finding of larger N400 components to semantically incongruous than congruous words, in both the semantic and metric tasks, suggests that the N400 component reflects automatic aspects of semantic processing.     

Antero-postero differences in cortical thickness and cortical porosity of T12 to L5 vertebral bodies

OBJECTIVE: This study will investigate interrelationships between the cortical shell and cancellous bone trabecular thickness, in vertebral bodies. METHODS: One hundred and sixty vertebral bodies from T12 to L5 were obtained at autopsy. The average age of the cohort was 59.3+/-22.1 years (range = 20-94 years). Cortical thickness, cortical porosity and trabecular thickness from the adjacent cancellous bone were measured. RESULTS: At the mid-vertebral body anterior cortical thickness was significantly greater than posterior cortical thickness (524 +/- 352 vs. 370 +/- 283 microm, respectively, P < 0.0001) and mid-anterior cortical porosity was significantly less than mid-posterior cortical porosity (24 +/- 14% vs. 32 +/- 16%, respectively, P < 0.0001). There were no anterior/posterior differences in trabecular thickness of the cancellous bone adjacent to the cortical walls. CONCLUSION: This study provides a novel perspective of T12 to L5 vertebral body bone, where measurement of cortical thickness and cortical porosity in a cohort of skeletally normal individuals revealed structural differences between load bearing anterior and posterior cortical walls. The data suggest that modulators of change to vertebral body bone may affect the cortical and trabecular bone differently. The relationships between cortical and cancellous bone suggest that the middle sectors of the vertebral body play a critical role in load bearing.     

Ten-year survey reveals differences in GP management of neck and back pain

Purpose

Clinical guidelines provide similar recommendations for the management of new neck pain and low back pain (LBP) but it is unclear if general practitioner’s (GP) care is similar. While GP’s management of LBP is well documented, little is known about GP’s management of neck pain. We aimed to describe GP’s management of new neck pain and compare this to GP’s management of new LBP in Australia between April 2000 and March 2010.

Methods

All GP–patient encounters for a new (i.e. first visit to any medical practitioner) neck pain or LBP problem were compared in terms of treatment delivered, referral patterns and requests for laboratory and imaging investigations.

Results

General practitioners in Australia have managed new neck pain and LBP problems at a rate of 3.1 and 5.8 per 1,000 GP–patient encounters, respectively. GP’s primarily utilised medications, in particular non-steroidal anti-inflammatory drugs, to manage new neck and LBP problems and referred approximately 25% of all patients for imaging. Patients with new neck pain are more frequently managed using physical treatments and were referred more often to allied health professionals and specialists. In comparison, patients with new LBP were managed more frequently with medication, advice, provision of a sickness certificate and ordering of pathology tests.

Conclusions

This is the first time GP management of a new episode of neck pain has been documented using a nationally representative sample and it is also the first time that the management of back and neck pain has been compared. Despite guidelines endorsing a similar approach for the management of new neck pain and LBP, in actual clinical practice Australian GPs manage these two conditions differently.     

Persistent responsiveness of long-latency auditory cortical activities in response to repeated stimuli of musical timbre and vowel sounds

Long-latency auditory-evoked magnetic field and potential show strong attenuation of N1m/N1 responses when an identical stimulus is presented repeatedly due to adaptation of auditory cortical neurons. This adaptation is weak in subsequently occurring P2m/P2 responses, being weaker for piano chords than single piano notes. The adaptation of P2m is more suppressed in musicians having long-term musical training than in nonmusicians, whereas the amplitude of P2 is enhanced preferentially in musicians as the spectral complexity of musical tones increases. To address the key issues of whether such high responsiveness of P2m/P2 responses to complex sounds is intrinsic and common to nonmusical sounds, we conducted a magnetoencephalographic study on participants who had no experience of musical training, using consecutive trains of piano and vowel sounds. The dipole moment of the P2m sources located in the auditory cortex indicated significantly suppressed adaptation in the right hemisphere both to piano and vowel sounds. Thus, the persistent responsiveness of the P2m activity may be inherent, not induced by intensive training, and common to spectrally complex sounds. The right hemisphere dominance of the responsiveness to musical and speech sounds suggests analysis of acoustic features of object sounds to be a significant function of P2m activity.     

A developmental fMRI study of reading and repetition reveals changes in phonological and visual mechanisms over age

In this study of reading development, children (ages 7-10) and adults (ages 18-32) performed overt single-word reading and aural repetition tasks on high-frequency word stimuli during functional magnetic resonance imaging. Most regions showed similar activity across age groups. These widespread regions of similarity indicate that children and adults use largely overlapping mechanisms when processing high-frequency words. Significant task-related differences included greater activity in occipital cortex for the read task, and greater activity in temporal cortex for the repeat task; activity levels in these regions were similar for adults and children. However, age group differences were found in several posterior regions, including a set of regions implicated in adult reading: the left supramarginal gyrus, the left angular gyrus, and bilateral anterior extrastriate cortex. The angular and supramarginal gyrus regions, hypothesized to play a role in phonology, showed decreased activity in adults relative to children for high-frequency words. The extrastriate regions had significant activity for both the visual read task and auditory repeat task in children, but just for the read task in adults, showing significant task and age interactions. These results are consistent with decreasing reliance on phonological processing, and increasing tuning of visual mechanisms, with age.     

A frontoparietal network for spatial attention reorienting in the auditory domain: a human fMRI/MEG study of functional and temporal dynamics

Several studies have identified a supramodal network critical to the reorienting of attention toward stimuli at novel locations and which involves the right temporoparietal junction and the inferior frontal areas. The present functional magnetic resonance imaging (fMRI)\magnetoencephalography (MEG) study investigates: 1) the cerebral circuit underlying attentional reorienting to spatially varying sound locations; 2) the circuit related to the regular change of sound location in the same hemifield, the change of sound location across hemifields, or sounds presented randomly at different locations on the azimuth plane; 3) functional temporal dynamics of the observed cortical areas exploiting the complementary characteristics of the fMRI and MEG paradigms. fMRI results suggest 3 distinct roles: the supratemporal plane appears modulated by variations of sound location; the inferior parietal lobule is modulated by the cross-meridian effect; and the inferior frontal cortex is engaged by the inhibition of a motor response. MEG data help to elucidate the temporal dynamics of this network by providing high-resolution time series with which to measure latency of neural activation manipulated by the reorienting of attention.     

Modulation of connectivity in visual pathways by attention: cortical interactions evaluated with structural equation modelling and fMRI

Electrophysiological and neuroimaging studies have shown that attention to visual motion can increase the responsiveness of the motion- selective cortical area V5 and the posterior parietal cortex (PP). Increased or decreased activation in a cortical area is often attributed to attentional modulation of the cortical projections to that area. This leads to the notion that attention is associated with changes in connectivity. We have addressed attentional modulation of effective connectivity using functional magnetic resonance imaging (fMRI). Three subjects were scanned under identical stimulus conditions (visual motion) while varying only the attentional component of the task. Haemodynamic responses defined an occipito-parieto-frontal network, including the, primary visual cortex (V1), V5 and PR A structural equation model of the interactions among these dorsal visual pathway areas revealed increased connectivity between V5 and PP related to attention. On the basis of our analysis and the neuroanatomical pattern of projections from the prefrontal cortex to PP we attributed the source of modulatory influences, on the posterior visual pathway, to the prefrontal cortex (PFC). To test this hypothesis we included the PFC in our model as a 'modulator' of the pathway between V5 and PP, using interaction terms in the structural equation model. This analysis revealed a significant modulatory effect of prefrontal regions on V5 afferents to posterior parietal cortex.      

Geographic differences in the incidence of gallbladder disease. Influence of environment and ethnic background

A study comparing the incidence of gallbladder disease in eight races in Hawaii is reported. The study included all patients with diagnosis on discharge from 1965 through 1969 at The Queen's Medical Center, Honolulu. Significant differences have been found to exist among the races. The greatest incidence was in the Chinese for whom gallbladder disease accounted for 2.57 per cent of all hospital admissions. This value is compared with other values obtained from the literature for various racial groups. It was found to be comparable to that of the Pima Indians of Southwestern United States whose incidence is 2.3 per cent. Sex ratio for each group was calculated and differences were noted here as well. Age distribution for each race was obtained, but no differences were found.     

Changes in fMRI activation following rehabilitation of reading and visual processing deficits in subjects with traumatic brain injury

In this case series fMRI was used to examine activation patterns during presentation of a reading comprehension (RC) task in three adult subjects with a history of severe traumatic brain injury (TBI). These subjects received cognitive rehabilitation therapy (CRT) for visual processing and acquired reading deficits. fMRI and neuropsychological testing occurred pre- and post-rehabilitation. The study's objective was to evaluate the neurobiological changes using fMRI occurring with CRT and to compare these results to repeat fMRI in matched control subjects. While improvements in neuropsychological testing occurred post-CRT, diffuse and variable activation patterns in the subjects with TBI were still demonstrated when compared to the control subjects repeat imaging. Multiple networks exist to accomplish the complex task of sentence reading and rehabilitation of the cognitive components of reading, such as visual processing; in subjects with TBI, can alter the activation pattern demonstrated during reading comprehension in subjects many years post-injury. This is the first demonstration of changes in network activation patterns post-CRT in patients with severe, chronic TBI on an fMRI task shown to have imaging stability in a normal control sample.     

Changes in fMRI activation following rehabilitation of reading and visual processing deficits in subjects with traumatic brain injury

In this case series fMRI was used to examine activation patterns during presentation of a reading comprehension (RC) task in three adult subjects with a history of severe traumatic brain injury (TBI). These subjects received cognitive rehabilitation therapy (CRT) for visual processing and acquired reading deficits. fMRI and neuropsychological testing occurred pre- and post-rehabilitation. The study's objective was to evaluate the neurobiological changes using fMRI occurring with CRT and to compare these results to repeat fMRI in matched controlsubjects. While improvements in neuropsychologicaltesting occurred post-CRT, diffuse and variable activation patterns in the subjects with TBI were still demonstrated when compared to the control subjects repeat imaging. Multiple networks exist to accomplish the complex task of sentence reading and rehabilitation of the cognitive components of reading, such as visual processing; in subjects with TBI, can alter the activation pattern demonstrated during reading comprehension in subjects many years post-injury. This is the first demonstration of changes in network activation patterns post-CRT in patients with severe, chronic TBI on an fMRI task shown to have imaging stability in a normal control sample.     

Effects of spectrum, background noise, and stimulation rate on the auditory startle reflex in hyperbilirubinemic rats

The sensory element of the acoustic startle reflex was studied in neonatal rats. Stimulus frequency, background noise, and stimulus presentation rate all affected the reflex. The performance of jaundiced rats with central auditory pathology is initially poorer than that of nonjaundiced rats but rapidly improves to the level of the controls, suggesting that the jaundiced rats may be a model for central auditory disturbances in humans. Startle reflex measurements give no indication that jaundiced rats surviving the testing period had neural hearing loss.     

Sex differences in cortical thickness mapped in 176 healthy individuals between 7 and 87 years of age

Findings from previous magnetic resonance imaging studies of sex differences in gray matter have been inconsistent, with some showing proportionally increased gray matter in women and some showing no differences between the sexes. Regional sex differences in gray matter thickness have not yet been mapped over the entire cortical surface in a large sample of subjects spanning the age range from early childhood to old age. We applied algorithms for cortical pattern matching and techniques for measuring cortical thickness to the structural magnetic resonance images of 176 healthy individuals between the ages of 7 and 87 years. We also mapped localized differences in brain size. Maps of sex differences in cortical thickness revealed thicker cortices in women in right inferior parietal and posterior temporal regions even without correcting for total brain volume. In these regions, the cortical mantle is up to 0.45 mm thicker, on average, in women than in men. Analysis of a subset of 18 female and 18 male subjects matched for age and brain volume confirmed the significance of thicker gray matter in temporal and parietal cortices in females, independent of brain size differences. Further analyses were conducted in the adult subjects where gender differences were evaluated using height as a covariate, and similar sex differences were observed even when body size differences between the sexes were controlled. Together, these results suggest that greater cortical thickness in posterior temporal inferior parietal regions in females relative to males are independent of differences in brain or body size. Age-by-sex interactions were not significant in the temporoparietal region, suggesting that sex differences in these regions are present from at least late childhood and then are maintained throughout life. Male brains were larger than female brains in all locations, though male enlargement was most prominent in the frontal and occipital poles, bilaterally. Given the large sample and the large range of ages studied, these results help to address controversies in the study of central nervous system sexual dimorphisms.     

Segregating semantic and syntactic aspects of processing in the human brain: an fMRI investigation of different word types

The processing of single words that varied in their semantic (concrete/abstract word) and syntactic (content/function word) status was investigated under different task demands (semantic/ syntactic task) in an event-related functional magnetic resonance imaging experiment. Task demands to a large degree determined which subparts of the neuronal network supporting word processing were activated. Semantic task demands selectively activated the left pars triangularis of the inferior frontal gyrus (BA 45) and the posterior part of the left middle/superior temporal gyrus (BA 21/22/37). In contrast, syntactic processing requirements led to an increased activation in the inferior tip of the left frontal operculum (BA 44) and the cortex lining the junction of the inferior frontal and inferior precentral sulcus (BA 44/6). Moreover, for these latter areas a word class by concreteness interaction was observed when a syntactic judgement was required. This interaction can be interpreted as a prototypicality effect: non-prototypical members of a word class, i.e. concrete function words and abstract content words, showed a larger activation than prototypical members, i.e. abstract function words and concrete content words. The combined data suggest that the activation pattern underlying word processing is predicted neither by syntactic class nor semantic concreteness but, rather, by task demands focusing either on semantic or syntactic aspects. Thus, our findings that semantic and syntactic aspects of processing are both functionally distinct and involve different subparts of the neuronal network underlying word processing support a domain-specific organization of the language system.     

Real and illusory contour processing in area V1 of the primate: a cortical balancing act.

It is known that neurons in area V2 (the second visual area) can signal the orientation of illusory contours in the primate. Whether area V1 (primary visual cortex) can signal illusory contour orientation is more controversial. While some electrophysiology studies have ruled out illusory signaling in V1, other reports suggest that V1 shows some illusory-specific response. Here, using optical imaging and single unit electrophysiology, we report that primate V1 does show an orientation-specific response to the 'abutting line grating' illusory contour. However, this response does not signal an illusory contour in the conventional sense. Rather, we find that illusory contour stimulation leads to an activation map that, after appropriate subtraction of real line signal, is inversely related to the real orientation map. The illusory contour orientation is thus negatively signaled or de-emphasized in V1. This 'activation reversal' is robust, is not due merely to presence of line ends, is not dependent on inducer orientation, and is not due to precise position of line end stimulation of V1 cells. These data suggest a resolution for previous apparently contradictory experimental findings. We propose that the de-emphasis of illusory contour orientation in V1 may be an important signal of contour identity and may, together with illusory signal from V2, provide a unique signature for illusory contour representation.