The posterior superior temporal sulcus is sensitive to the outcome of human and non-human goal-directed actions

Prior studies have demonstrated that the posterior superior temporal sulcus (pSTS) is involved in analyzing the intentions underlying actions and is sensitive to the context within which actions occur. However, it is debated whether the pSTS is actually sensitive to goals underlying actions, or whether previous studies can be interpreted to suggest that the pSTS is instead involved in the allocation of visual attention towards unexpected events. In addition, little is known about whether the pSTS is specialized for reasoning about the actions of social agents or whether the pSTS is sensitive to the actions of both animate and inanimate entities. Here, using functional magnetic resonance imaging, we investigated activation in response to passive viewing of successful and unsuccessful animate and inanimate goal-directed actions. Activation in the right pSTS was stronger in response to failed actions compared to successful actions, suggesting that the pSTS plays a role in encoding the goals underlying actions. Activation in the pSTS did not differentiate between animate and inanimate actions, suggesting that the pSTS is sensitive to the goal-directed actions of both animate and inanimate entities.

Microbial removal from the separated liquid fraction of anaerobically digested pig manure in meso-scale integrated constructed wetlands

The aim was to investigate microbial removal from the liquid fraction of anaerobically digested pig manure in meso-scale integrated constructed wetlands (ICW's) over a 13 month period. Four treatments were investigated: T1 (standard), T2 (effluent recycling), T3 (high nutrient loading), and T4 (high flow rate). Mean counts of yeasts and moulds and spore-forming bacteria were higher in T3 and T4 than in T1 and T2 (P<0.05). Flow through the cells reduced mean counts of coliform, yeasts and moulds and spore-forming bacteria across all treatments (P<0.01). Counts varied with season; coliform were highest in the Summer (P<0.001), with yeasts and moulds highest in the Summer and Autumn (P<0.01) and spore-formers lowest in the Autumn (P<0.001). As Salmonella was undetectable in the influent and Escherichia coli and Enterococcus were rarely detected it is difficult to make conclusions regarding pathogen removal. Further investigations using marked strains would allow pathogen tracking within the ICW's.

The fMRI BOLD signal tracks electrophysiological spectral perturbations, not event-related potentials

Functional magnetic resonance imaging (fMRI) and electroencephalography (EEG) are primary tools of the psychological neurosciences. It is therefore important to understand the relationship between hemodynamic and electrophysiological responses. An early study by Huettel and colleagues found that the coupling of fMRI blood-oxygen-level-dependent signal (BOLD) and subdurally-recorded signal-averaged event-related potentials (ERPs) was not consistent across brain regions. Instead, a growing body of evidence now indicates that hemodynamic changes measured by fMRI reflect non-phase-locked changes in high frequency power rather than the phase-locked ERP. Here, we revisit the data from Huettel and colleagues and measure event-related spectral perturbations (ERSPs) to examine the time course of frequency changes. We found that, unlike the ERP, γ-ERSP power was consistently coupled with the hemodynamic response across three visual cortical regions. Stimulus duration modulated the BOLD signal and the γ-ERSP in the peri-calcarine and fusiform cortices, whereas there was no such modulation of either physiological signal in the lateral temporal-occipital cortex. This finding reconciles the original report with the more recent literature and demonstrates that the ERP and ERSP reflect dissociable aspects of neural activity.

Category-selective background connectivity in ventral visual cortex

Ventral visual cortex contains specialized regions for particular object categories, but little is known about how these regions interact during object recognition. Here we examine how the face-selective fusiform gyrus (FG) and the scene-selective parahippocampal cortex (PHC) interact with each other and with the rest of the brain during different visual tasks. To assess these interactions, we developed a novel approach for identifying patterns of connectivity associated with specific task sets, independent of stimulus-evoked responses. We tested whether this "background connectivity" between the FG and PHC was modulated when subjects engaged in face and scene processing tasks. In contrast to what would be predicted from biased competition or intrinsic activity accounts, we found that the strength of FG-PHC background connectivity depended on which category was task relevant: connectivity increased when subjects attended to scenes (irrespective of whether a competing face was present) and decreased when subjects attended to faces (irrespective of competing scenes). We further discovered that posterior occipital cortex was correlated selectively with the FG during face tasks and the PHC during scene tasks. These results suggest that category specificity exists not only in which regions respond most strongly but also in how these and other regions interact.

Serotonin transporter gene polymorphisms and brain function during emotional distraction from cognitive processing in posttraumatic stress disorder

BACKGROUND

Serotonergic system dysfunction has been implicated in posttraumatic stress disorder (PTSD). Genetic polymorphisms associated with serotonin signaling may predict differences in brain circuitry involved in emotion processing and deficits associated with PTSD. In healthy individuals, common functional polymorphisms in the serotonin transporter gene (SLC6A4) have been shown to modulate amygdala and prefrontal cortex (PFC) activity in response to salient emotional stimuli. Similar patterns of differential neural responses to emotional stimuli have been demonstrated in PTSD but genetic factors influencing these activations have yet to be examined.

METHODS

We investigated whether SLC6A4 promoter polymorphisms (5-HTTLPR, rs25531) and several downstream single nucleotide polymorphisms (SNPs) modulated activity of brain regions involved in the cognitive control of emotion in post-9/11 veterans with PTSD. We used functional MRI to examine neural activity in a PTSD group (n = 22) and a trauma-exposed control group (n = 20) in response to trauma-related images presented as task-irrelevant distractors during the active maintenance period of a delayed-response working memory task. Regions of interest were derived by contrasting activation for the most distracting and least distracting conditions across participants.

RESULTS

In patients with PTSD, when compared to trauma-exposed controls, rs16965628 (associated with serotonin transporter gene expression) modulated task-related ventrolateral PFC activation and 5-HTTLPR tended to modulate left amygdala activation. Subsequent to combat-related trauma, these SLC6A4 polymorphisms may bias serotonin signaling and the neural circuitry mediating cognitive control of emotion in patients with PTSD.

CONCLUSIONS

The SLC6A4 SNP rs16965628 and 5-HTTLPR are associated with a bias in neural responses to traumatic reminders and cognitive control of emotions in patients with PTSD. Functional MRI may help identify intermediate phenotypes and dimensions of PTSD that clarify the functional link between genes and disease phenotype, and also highlight features of PTSD that show more proximal influence of susceptibility genes compared to current clinical categorizations.

Reduced hippocampal and amygdala activity predicts memory distortions for trauma reminders in combat-related PTSD

Neurobiological models of posttraumatic stress disorder (PTSD) suggest that altered activity in the medial temporal lobes (MTL) during encoding of traumatic memories contribute to the development and maintenance of the disorder. However, there is little direct evidence in the PTSD literature to support these models. The goal of the present study was to examine MTL activity during trauma encoding in combat veterans using the subsequent memory paradigm. Fifteen combat veterans diagnosed with PTSD and 14 trauma-exposed control participants viewed trauma-related and neutral pictures while undergoing event-related fMRI. Participants returned one week after scanning for a recognition memory test. Region-of-interest (ROI) and voxel-wise whole brain analyses were conducted to examine the neural correlates of successful memory encoding. Patients with PTSD showed greater false alarm rates for novel lures than the trauma-exposed control group, suggesting reliance on gist-based representations in lieu of encoding contextual details. Imaging analyses revealed reduced activity in the amygdala and hippocampus in PTSD patients during successful encoding of trauma-related stimuli. Reduction in left hippocampal activity was associated with high arousal symptoms on the Clinician-Administered PTSD Scale (CAPS). The behavioral false alarm rate for traumatic stimuli co-varied with activity in the bilateral precuneus. These results support neurobiological theories positing reduced hippocampal activity under conditions of high stress and arousal. Reduction in MTL activity for successfully encoded stimuli and increased precuneus activity may underlie reduced stimulus-specific encoding and greater gist memory in patients with PTSD, leading to maintenance of the disorder.

Scan-rescan reliability of subcortical brain volumes derived from automated segmentation

Large-scale longitudinal studies of regional brain volume require reliable quantification using automated segmentation and labeling. However, repeated MR scanning of the same subject, even if using the same scanner and acquisition parameters, does not result in identical images due to small changes in image orientation, changes in prescan parameters, and magnetic field instability. These differences may lead to appreciable changes in estimates of volume for different structures. This study examined scan-rescan reliability of automated segmentation algorithms for measuring several subcortical regions, using both within-day and across-day comparison sessions in a group of 23 normal participants. We found that the reliability of volume measures including percent volume difference, percent volume overlap (Dice's coefficient), and intraclass correlation coefficient (ICC), varied substantially across brain regions. Low reliability was observed in some structures such as the amygdala (ICC = 0.6), with higher reliability (ICC = 0.9) for other structures such as the thalamus and caudate. Patterns of reliability across regions were similar for automated segmentation with FSL/FIRST and FreeSurfer (longitudinal stream). Reliability was associated with the volume of the structure, the ratio of volume to surface area for the structure, the magnitude of the interscan interval, and the method of segmentation. Sample size estimates for detecting changes in brain volume for a range of likely effect sizes also differed by region. Thus, longitudinal research requires a careful analysis of sample size and choice of segmentation method combined with a consideration of the brain structure(s) of interest and the magnitude of the anticipated effects.

Staying cool when things get hot: emotion regulation modulates neural mechanisms of memory encoding

During times of emotional stress, individuals often engage in emotion regulation to reduce the experiential and physiological impact of negative emotions. Interestingly, emotion regulation strategies also influence memory encoding of the event. Cognitive reappraisal is associated with enhanced memory while expressive suppression is associated with impaired explicit memory of the emotional event. However, the mechanism by which these emotion regulation strategies affect memory is unclear. We used event-related fMRI to investigate the neural mechanisms that give rise to memory formation during emotion regulation. Twenty-five participants viewed negative pictures while alternately engaging in cognitive reappraisal, expressive suppression, or passive viewing. As part of the subsequent memory design, participants returned to the laboratory two weeks later for a surprise memory test. Behavioral results showed a reduction in negative affect and a retention advantage for reappraised stimuli relative to the other conditions. Imaging results showed that successful encoding during reappraisal was uniquely associated with greater co-activation of the left inferior frontal gyrus, amygdala, and hippocampus, suggesting a possible role for elaborative encoding of negative memories. This study provides neurobehavioral evidence that engaging in cognitive reappraisal is advantageous to both affective and mnemonic processes.

A novel method for quantifying scanner instability in fMRI

A method was developed to quantify the effect of scanner instability on functional MRI data by comparing the instability noise to endogenous noise present when scanning a human. The instability noise was computed from agar phantom data collected with two flip angles, allowing for a separation of the instability from the background noise. This method was used on human data collected at four 3 T scanners, allowing the physiological noise level to be extracted from the data. In a "well-operating" scanner, the instability noise is generally less than 10% of physiological noise in white matter and only about 2% of physiological noise in cortex. This indicates that instability in a well-operating scanner adds very little noise to functional MRI results. This new method allows researchers to make informed decisions about the maximum instability level a scanner can have before it is taken off line for maintenance or rejected from a multisite consortium. This method also provides information about the background noise, which is generally larger in magnitude than the instability noise.

The Wolfpack Effect

Imagine a pack of predators stalking their prey. The predators may not always move directly toward their target (e.g., when circling around it), but they may be consistently facing toward it. The human visual system appears to be extremely sensitive to such situations, even in displays involving simple shapes. We demonstrate this by introducing the wolfpack effect, which is found when several randomly moving, oriented shapes (darts, or discs with “eyes”) consistently point toward a moving disc. Despite the randomness of the shapes’ movement, they seem to interact with the disc—as if they are collectively pursuing it. This impairs performance in interactive tasks (including detection of actual pursuit), and observers selectively avoid such shapes when moving a disc through the display themselves. These and other results reveal that the wolfpack effect is a novel “social” cue to perceived animacy. And, whereas previous work has focused on the causes of perceived animacy, these results demonstrate its effects, showing how it irresistibly and implicitly shapes visual performance and interactive behavior.

Electrophysiological correlates of processing faces of younger and older individuals

The 'own-age bias' in face processing suggests that the age of a face constitutes one important factor that influences attention to and memory for faces. The present experiment investigated electrophysiological correlates of processing faces of younger and older individuals. Younger participants were presented with pictures of unfamiliar younger and older faces in the context of a gender categorization task. A comparison of event-related potentials showed that early components are sensitive to faces of different ages: (i) larger positive potential peaking at 160 ms (P200) for older than younger faces at fronto-central electrodes; (ii) larger negative potential peaking at 252 ms (N200) for younger than older faces at fronto-central electrodes; (iii) larger negative-going deflection peaking at 320 ms (N250) for younger than older faces at occipito-temporal electrodes; and (iv) larger late positive potential peaking at 420 ms (LPP 420) for older than younger faces at parietal and other electrodes. We discuss similarities between the present study and a previously published study of faces of different races as suggesting involvement of comparable electrophysiological responses when differentiating between stimulus categories.

The relationship of γ oscillations and face-specific ERPs recorded subdurally from occipitotemporal cortex

The perception of faces evokes characteristic electrophysiological responses at discrete loci in human fusiform gyrus and adjacent ventral occipitotemporal cortical sites. Prominent among these responses are a surface-negative potential at ∼200-ms postonset (face-N200) and face-induced spectral perturbations in the gamma band (face-γERSP). The degree to which these responses represent activity in the same cortical loci and the degree to which they are influenced by the same perceptual and task variables are unknown. We evaluated this anatomical colocalization and functional correlation in 2 experiments in which the electrocorticogram was recorded from subdural electrodes in 51 participants. Experiment 1 investigated the category specificity of the γERSP and its colocalization with the face-N200. Experiment 2 examined differences in face-N200 and face-γERSP to face stimuli that varied in featural complexity. We found that γERSP is a category-specific phenomenon with separate, though overlapping, category sensitivities as the N200. Further, the presence of face-γERSP at an electrode site significantly predicted the presence and amplitude of face-N200 at that site. However, the converse was not true in that face-N200 was evoked by impoverished face stimuli that did not induce face-γERSP. These results demonstrate that these electrophysiological responses reflect separate components of the brain's face processing system.

Face-Specific Resting Functional Connectivity between the Fusiform Gyrus and Posterior Superior Temporal Sulcus

Faces activate specific brain regions in fMRI, including the fusiform gyrus (FG) and the posterior superior temporal sulcus (pSTS). The fact that the FG and pSTS are frequently co-activated suggests that they may interact synergistically in a distributed face processing network. Alternatively, the functions implemented by these regions may be encapsulated from each other. It has proven difficult to evaluate these two accounts during visual processing of face stimuli. However, if the FG and pSTS interact during face processing, the substrate for such interactions may be apparent in a correlation of the BOLD timeseries from these two regions during periods of rest when no faces are present. To examine face-specific resting correlations, we developed a new partial functional connectivity approach in which we removed variance from the FG that was shared with other category-selective and control regions. The remaining face-specific FG resting variance was then used to predict resting signals throughout the brain. In two experiments, we observed face-specific resting functional connectivity between FG and pSTS, and importantly, these correlations overlapped precisely with the face-specific pSTS region obtained from independent localizer runs. Additional region-of-interest and pattern analyses confirmed that the FG–pSTS resting correlations were face-specific. These findings support a model in which face processing is distributed among a finite number of connected, but nevertheless face-specialized regions. The discovery of category-specific interactions in the absence of visual input suggests that resting networks may provide a latent foundation for task processing.

British Association for Sexual Health and HIV: framework for guideline development and assessment

This article has been prepared by the Clinical Effectiveness Group (CEG) of the British Association for Sexual Health and HIV (BASHH) to specify the methodology BASHH requires for guideline development and the process of guideline evaluation by the CEG. This replaces the specifications for the development of UK guidelines on the management of sexually transmitted infections and closely related conditions previously published in this journal in 2004 and updated in 2005.

Controlled scanpath variation alters fusiform face activation

We investigated the influence of experimentally guided saccades and fixations on fMRI activation in brain regions specialized for face and object processing. Subjects viewed a static image of a face while a small fixation cross made a discrete jump within the image every 500 ms. Subjects were required to make a saccade and fixate the cross at its new location. Each run consisted of alternating blocks in which the subject was guided to make a series of saccades and fixations that constituted either a Typical or an Atypical face scanpath. Typical scanpaths were defined as a scanpath in which the fixation cross landed on the eyes or the mouth in 90% of all trials. Atypical scanpaths were defined as scanpaths in which the fixation cross landed on the eyes or mouth on 12% of all trials. The average saccade length was identical in both typical and atypical blocks, and both were preceded by a baseline block where the fixation cross made much smaller jumps in the middle of the screen. Within the functionally predefined face area of the ventral occipitotemporal cortex (VOTC), typical scanpaths evoked significantly more activity when compared to atypical scanpaths. A voxel-based analysis revealed a similar pattern in clusters of voxels located within VOTC, frontal eye fields, superior colliculi, intraparietal sulcus, and inferior frontal gyrus. These results demonstrate that fMRI activation is highly sensitive to the pattern of eye movements employed during face processing, and thus illustrates the potential confounding influence of uncontrolled eye movements for neuroimaging studies of face and object perception in normal and clinical populations.

Reading about the actions of others: biological motion imagery and action congruency influence brain activity

Prior neuroimaging research has implicated regions within and near the posterior superior temporal sulcus (pSTS) in the visual processing of biological motion and of the intentions implied by specific movements. However, it is unknown whether this region is engaged during the processing of human motion at a conceptual level, such as during story comprehension. Here, we obtained functional magnetic resonance images from subjects reading brief stories that described a human character's background and then concluded with an action or decision made by the character. Half of the stories contained incidental descriptions of biological motion (such as the character's walking or grasping) while the remaining half did not. As a second factor, the final action of the story was either congruent or incongruent with the character's background and implied goals and intentions. Stories that contained biological motion strongly activated the pSTS bilaterally, along with ventral temporal areas, premotor cortex, left motor cortex, and the precuneus. Active regions of pSTS in individual subjects closely overlapped with regions identified with a separate biological motion localizer (point-light display) task. Reading incongruent versus congruent stories activated dorsal anterior cingulate cortex and bilateral anterior insula. These results support the hypothesis that reading can engage higher visual cortex in a content-specific manner, and suggest that the presence of biological motion should be controlled as a potential confound in fMRI studies using story comprehension tasks.

The effect of acute tryptophan depletion on emotional distraction and subsequent memory

Serotonin is a key neurotransmitter involved in emotional regulation and memory. A number of studies using acute tryptophan depletion (ATD) in healthy subjects have shown that a temporary serotonin reduction both induces a negative emotional bias and impairs long-term memory. However, little is known about the specific effects of ATD on emotional memory. Using functional magnetic resonance imaging (fMRI), we investigated the effect of ATD on negative memory and executive function in healthy volunteers. Our emotional oddball task required participants to distinguish infrequently presented targets from distracting negative and neutral pictures. Memory for the distracting pictures was tested 1 h following the fMRI session. ATD selectively enhanced memory for negative distractors relative to neutral distractors and increased activation in response to the negative distractors in the left orbital-inferior frontal, dorsomedial prefrontal and bilateral angular gyri. ATD also induced greater activation in the left inferior frontal gyrus and anterior cingulate across all stimuli. Stronger frontal activation to distractors was positively correlated with memory performance on ATD but not control days, indicating a possible compensatory mechanism for coping with increased task demand under the ATD challenge. These findings highlight the importance of serotonin in negative memory with implications for mood disorders.

Rebuttal to Hasan and Pedraza in comments and controversies: "Improving the reliability of manual and automated methods for hippocampal and amygdala volume measurements"

Here we address the critiques offered by Hasan and Pedraza to our recently published manuscript comparing the performance of two automated segmentation programs, FSL/FIRST and FreeSurfer (Morey R, Petty C, Xu Y, Pannu Hayes J, Wagner H, Lewis D, LaBar K, Styner M, McCarthy G. (2009): A comparison of automated segmentation and manual tracing for quantifying of hippocampal and amygdala volumes. Neuroimage 45:855-866). We provide an assessment and discussion of their specific critiques. Hasan and Pedraza bring up some important points concerning our omission of sample demographic features and inclusion of left and right hemisphere volumes as independent measures in correlational analyses. We present additional data on demographic attributes of our sample and correlations analyzed separately on left and right hemispheres of the amygdala and hippocampus. While their commentary aids the reader to more critically asses our study, it falls short of substantiating that our omissions ought to lead readers to significantly revise their interpretations. Further research will help to disentangle the advantages and limitations of the various freely-available automated segmentation software packages.