Anterior Patches Research Articles

Natural scenes reveal diverse representations of 2D and 3D body pose in the human brain

Human pose, defined as the spatial relationships between body parts, carries instrumental information supporting the understanding of motion and action of a person. A substantial body of previous work has identified cortical areas responsive to images of bodies and different body parts. However, the neural basis underlying the visual perception of body part relationships has received less attention. To broaden our understanding of body perception, we analyzed high-resolution fMRI responses to a wide range of poses from over 4,000 complex natural scenes. Using ground-truth annotations and an application of three-dimensional (3D) pose reconstruction algorithms, we compared similarity patterns of cortical activity with similarity patterns built from human pose models with different levels of depth availability and viewpoint dependency. Targeting the challenge of explaining variance in complex natural image responses with interpretable models, we achieved statistically significant correlations between pose models and cortical activity patterns (though performance levels are substantially lower than the noise ceiling). We found that the 3D view-independent pose model, compared with two-dimensional models, better captures the activation from distinct cortical areas, including the right posterior superior temporal sulcus (pSTS). These areas, together with other pose-selective regions in the LOTC, form a broader, distributed cortical network with greater view-tolerance in more anterior patches. We interpret these findings in light of the computational complexity of natural body images, the wide range of visual tasks supported by pose structures, and possible shared principles for view-invariant processing between articulated objects and ordinary, rigid objects.

Scene Perception and Visuospatial Memory Converge at the Anterior Edge of Visually Responsive Cortex.

To fluidly engage with the world, our brains must simultaneously represent both the scene in front of us and our memory of the immediate surrounding environment (i.e., local visuospatial context). How does the brain's functional architecture enable sensory and mnemonic representations to closely interface while also avoiding sensory-mnemonic interference? Here, we asked this question using first-person, head-mounted virtual reality and fMRI. Using virtual reality, human participants of both sexes learned a set of immersive, real-world visuospatial environments in which we systematically manipulated the extent of visuospatial context associated with a scene image in memory across three learning conditions, spanning from a single FOV to a city street. We used individualized, within-subject fMRI to determine which brain areas support memory of the visuospatial context associated with a scene during recall (Experiment 1) and recognition (Experiment 2). Across the whole brain, activity in three patches of cortex was modulated by the amount of known visuospatial context, each located immediately anterior to one of the three scene perception areas of high-level visual cortex. Individual subject analyses revealed that these anterior patches corresponded to three functionally defined place memory areas, which selectively respond when visually recalling personally familiar places. In addition to showing activity levels that were modulated by the amount of visuospatial context, multivariate analyses showed that these anterior areas represented the identity of the specific environment being recalled. Together, these results suggest a convergence zone for scene perception and memory of the local visuospatial context at the anterior edge of high-level visual cortex.SIGNIFICANCE STATEMENT As we move through the world, the visual scene around us is integrated with our memory of the wider visuospatial context. Here, we sought to understand how the functional architecture of the brain enables coexisting representations of the current visual scene and memory of the surrounding environment. Using a combination of immersive virtual reality and fMRI, we show that memory of visuospatial context outside the current FOV is represented in a distinct set of brain areas immediately anterior and adjacent to the perceptually oriented scene-selective areas of high-level visual cortex. This functional architecture would allow efficient interaction between immediately adjacent mnemonic and perceptual areas while also minimizing interference between mnemonic and perceptual representations.

More Than the Face: Representations of Bodies in the Inferior Temporal Cortex.

Visual representations of bodies, in addition to those of faces, contribute to the recognition of con- and heterospecifics, to action recognition, and to nonverbal communication. Despite its importance, the neural basis of the visual analysis of bodies has been less studied than that of faces. In this article, I review what is known about the neural processing of bodies, focusing on the macaque temporal visual cortex. Early single-unit recording work suggested that the temporal visual cortex contains representations of body parts and bodies, with the dorsal bank of the superior temporal sulcus representing bodily actions. Subsequent functional magnetic resonance imaging studies in both humans and monkeys showed several temporal cortical regions that are strongly activated by bodies. Single-unit recordings in the macaque body patches suggest that these represent mainly body shape features. More anterior patches show a greater viewpoint-tolerant selectivity for body features, which may reflect a processing principle shared with other object categories, including faces.

P98. CSF NFL – A new biomarker for neurodegeneration in CSVD?

Background Cerebrospinal fluid (CSF) neurofilament light chain (NfL) has emerged as a putative biomarker of neuroaxonal injury in various neurodegenerative diseases. Particularly, patients suffering from amyotrophic lateral sclerosis (ALS) display significantly elevated levels. We here aimed to compare CSF NfL between patients diagnosed to have cerebral small vessel disease (CSVD) and those exhibiting ALS. Supposing there to be some shared mechanisms of white matter injury we suspected to find similarly increased CSF NfL levels across the diagnostic groups. Methods Our analysis comprised (i) n = 22 patients with CSVD, defined according to the detectability of subcortical and cortical cerebral microbleeds and/or intracerebral hemorrhages (ICH), (ii) n = 39 patients diagnosed to have definite, probable or probable laboratory-supported ALS according to the El Escorial criteria and (iii) n = 31 hospital- and community-based control subjects. All cases were matched for age and sex, and all of them had CSF NfL levels available. In CSVD, cerebral MRIs were rated for the number of (i) cerebral microbleeds, (ii) enlarged perivascular spaces, (iii) lacunes and, for the existence of (a) cortical superficial siderosis and (b) white matter hyperintensities (WMH). WMH have thereby been assessed in a semiquantitative manner according to the Fazeka’s visual rating scale ranging from 0 to 3 and according to the existence of different patterns (multiple subcortical spots, peri-basal ganglia WMH, anterior subcortical patches, posterior subcortical patches). ANOVA was conducted with CSF NfL as dependent variable and group as a fixed factor; for subgroup comparisons Bonferroni adjusted post hoc analysis was performed. In CSVD, bivariate correlations and Mann–Whitney U test were calculated to relate CSF NfL levels to the various MRI measures. P-values £ 0.05 were deemed to be statistically significant. Results When considering the whole cohort CSF NfL levels were not related to age or sex. Analysis revealed a significant group effect (F(2) = 10.5, p ρ = 0.4, p = 0.04, one-tailed). Higher CSF NfL concentrations were, moreover, related to the existence of peri-basal ganglia WMH (Z = 1.9, p = 0.06 [trend-level]). Discussion Our data demonstrate that CSF NfL could serve as a biomarker for neuroaxonal injury in CSVD subjects, revealing similarly elevated concentrations as those found in ALS. In CSVD CSF NfL thereby seems to reflect the extent and patterns of white matter damage, as expected.

Abstract TMP116: White Matter Hyperintensity Lesion Patterns in Patients With Cardioembolic Strokes

Background: Among patients with a cardioembolic stroke, atrial fibrillation (AF) is a common comorbidity that is associated with a worse outcome. Mounting data indicates that AF may relate to stroke pathogenesis through mechanisms other than cerebral thromboembolic complications. We sought to identify different WMH patterns between patients with AF vs. non-AF related embolic ischemic strokes. Methods: We retrospectively analyzed consecutive patients with acute anterior circulation embolic ischemic stroke included in an academic medical center’s stroke registry. The stroke etiology was determined using the Causative Classification System of ischemic stroke. WMH lesion burden was assessed according to the Fazekas scale. An independent blinded examiner classified the different WMH-patterns, which included 5 categories: periventricular, subcortical spots, posterior subcortical patches, anterior subcortical patches, and severe confluent subcortical patches. Their association with AF was investigated using multivariable logistic regression (with backward elimination). Results: Overall, 174 patients (94 with and 80 without AF) were included. In unadjusted analyses, patients with AF had a significantly higher rate of anterior subcortical patches (p=0.018) and a lower rate of a periventricular pattern (p=0.022). After adjusting for WMH lesion burden, presence of multiple infarcts, infarct volume, the CHA2DS2-VASc score as well as pertinent two-way and three-way interactions the presence of anterior subcortical patches (OR 2.41, 95%-CI 1.02-5.72, p=0.045) and a higher CHA2DS2-VASc score (per point, OR 1.28, 95%-CI 1.08-1.52, p=0.005) were independently associated with AF. Conclusions: We found that AF is associated with specific WMH lesion patterns on MRI. The clinical significance of this observation remains to be clarified; yet it suggests that the well-established link between stroke and AF extends beyond thromboembolism and may reflect an underlying cardiovasculopathy that can be characterized by WMH. If confirmed in future studies further investigation into the underlying pathophysiological mechanisms may provide novel avenues to AF detection and treatment.

Intelligent information loss: the coding of facial identity, head pose, and non-face information in the macaque face patch system.

Faces are a behaviorally important class of visual stimuli for primates. Recent work in macaque monkeys has identified six discrete face areas where most neurons have higher firing rates to images of faces compared with other objects (Tsao et al., 2006). While neurons in these areas appear to have different tuning (Freiwald and Tsao, 2010; Issa and DiCarlo, 2012), exactly what types of information and, consequently, which visual behaviors neural populations within each face area can support, is unknown. Here we use population decoding to better characterize three of these face patches (ML/MF, AL, and AM). We show that neural activity in all patches contains information that discriminates between the broad categories of face and nonface objects, individual faces, and nonface stimuli. Information is present in both high and lower firing rate regimes. However, there were significant differences between the patches, with the most anterior patch showing relatively weaker representation of nonface stimuli. Additionally, we find that pose-invariant face identity information increases as one moves to more anterior patches, while information about the orientation of the head decreases. Finally, we show that all the information we can extract from the population is present in patterns of activity across neurons, and there is relatively little information in the total activity of the population. These findings give new insight into the representations constructed by the face patch system and how they are successively transformed.

Functional mapping of face-selective regions in the extrastriate visual cortex of the marmoset.

The cerebral cortex of humans and macaques has specialized regions for processing faces and other visual stimulus categories. It is unknown whether a similar functional organization exists in New World monkeys, such as the common marmoset (Callithrix jacchus), a species of growing interest as a primate model in neuroscience. To address this question, we measured selective neural responses in the brain of four awake marmosets trained to fix their gaze upon images of faces, bodies, objects, and control patterns. In two of the subjects, we measured high gamma-range field potentials from electrocorticography arrays implanted over a large portion of the occipital and inferotemporal cortex. In the other two subjects, we measured BOLD fMRI responses across the entire brain. Both techniques revealed robust, regionally specific patterns of category-selective neural responses. We report that at least six face-selective patches mark the occipitotemporal pathway of the marmoset, with the most anterior patches showing the strongest preference for faces over other stimuli. The similar appearance of these patches to previous findings in macaques and humans, including their apparent arrangement in two parallel pathways, suggests that core elements of the face processing network were present in the common anthropoid primate ancestor living ∼35 million years ago. The findings also identify the marmoset as a viable animal model system for studying specialized neural mechanisms related to high-level social visual perception in humans.

Erosion of an Extrapericardial Implantable Cardioverter Defibrillator Patch Through the Gastric Fundus With Fistulous Tract Formation

Until as recently as the mid-1990s, implantable cardioverter defibrillator (ICD) leads were placed through thoracotomy as anterior and/or posterolateral patches. The defibrillator patches have reportedly been associated with a number of relatively common mechanical complications as well as less common complications, including patch migration or erosion into contiguous structures. We report a previously unreported late complication of epicardial defibrillator patch placement in which patch migration and erosion through the gastric fundus resulted in fistulous tract formation from the mediastinum to the lumen of the stomach. Although surgically implanted epicardial patch defibrillator systems are relatively uncommon in current U.S. practice, these devices are still used when specific anatomic or electrophysiological considerations preclude the use of more common endocardial lead systems. Several thousand patients with epicardial patch leads in place are still believed to be alive in the United States. In these patients, continued vigilance for lead-related complications is appropriate. Prompt surgical intervention is usually warranted when patch migration or complications such as the one described occur.

Effect of abx, bx and pbx mutations on expression of homeotic genes in Drosophila larvae.

We have examined the patterns of expression of the homeotic gene Ubx in imaginal discs of Drosophila larvae carrying mutations in the abx, bx and pbx regulatory domains. In haltere discs, all five bx insertion mutations examined led to a general reduction in Ubx expression in the anterior compartment; for a given allele, the strength of the adult cuticle phenotype correlated with the degree of Ubx reduction. Deletions mapping near or overlapping the sites of bx insertions, including three abx alleles and the bx34e-prv(bx-prv) allele, showed greatly reduced Ubx expression in parts of the anterior compartment of the haltere disc; however, anterior patches of strong Ubx expression often remained, in highly variable patterns. As expected, the pbx1 mutation led to reduced Ubx expression in the posterior compartment of the haltere disc; surprisingly, pbx1 also led to altered expression of the en protein near the compartment border in the central region of the disc. In the metathoracic leg, all the bx alleles caused extreme reduction in Ubx expression in the anterior regions, with no allele-specific differences. In contrast, abx and bx-prv alleles resulted in patchy anterior reductions in third leg discs. In the larval central nervous system, abx but not bx alleles affected Ubx expression; the bx-prv deletion gave a wild-type phenotype, but it could not fully complement abx mutations. In the posterior wing disc, the bx-prv allele, and to a much lesser extent the bx34e chromosome from which it arose, led to ectopic expression of Ubx. Unlike other grain-of-function mutations in the BX-C, this phenotype appeared to be partially recessive to wild type. Finally, we asked whether the ppx transformation, which results from early lack of Ubx+ function in the mesothorax and is seen in abx animals, is due to ectopic Scr expression. Some mesothoracic leg and wing discs from abx2 larvae displayed ectopic expression of Scr, which was variable in extent but always confined to the posterior compartment.