Quantifying the variability of scene-selective regions: Interindividual, interhemispheric, and sex differences.

Previous work has shown that different cortical regions are sensitive to objects of differing real-world sizes (Konkle & Oliva, 2012; Mullally & Maguire, 2011; Bainbridge et al, 2012). Whereas a region in the occipito-temporal sulcus (OTS) shows small object selectivity, scene-selective regions (parahippocampal place area, PPA; retrosplenial cortex, RSC; and occipital place area, OPA) show systematically more activity for objects that are large in the world than smaller objects. What is the nature of this scene-like representation of objects? Here, we study an affordance-based object property: "interaction space". Interaction space is the area around objects that users traverse when interacting with the object. This interaction may include calculations of grasping points and surface area of contact, and is not necessarily conjoined with size. To fully deconvolve object interaction from physical size, we conducted a 2 x 2 factor design fMRI study with four conditions: 1) small one-handed objects (i.e., hairbrush), 2) large one-handed objects (i.e., umbrella), 3) small two-handed objects (i.e., hamburger), and 4) large two-handed objects (i.e., guitar). Stimuli were matched for ground truth size (based on physical sizes and weights), subjective size from an online survey, color, luminance, spectral energy, and retinal size. Results from a 2-factor ANOVA on beta values in functionally-defined ROIs show PPA, OPA, and RSC are sensitive to interaction space regardless of size, while PPA, OPA, and OTS are also sensitive to size regardless of interaction space. Importantly, effect sizes for interaction space in the PPA, OPA, and RSC were greater than those for object size, while the reverse was true for the OTS. These results show that interaction space is a perceptual object property that is represented in scene-selective regions, and suggest an overlapping interaction-based representation of objects and scenes in the brain. Meeting abstract presented at VSS 2013

The human entorhinal-hippocampal circuitry is characterized by an information-specific functional organization where two routes, that are preferentially connected to the parahippocampal cortex or the perirhinal and retrosplenial cortices, divide the entorhinal cortex as well as hippocampal subiculum and CA1 subregions.

The parahippocampal place area (PPA) is one of several brain regions that respond more strongly to scenes than to non-scene items such as objects and faces. The mechanism underlying this scene-preferential response remains unclear. One possibility is that the PPA is tuned to low-level stimulus features that are found more often in scenes than in less-preferred stimuli. Supporting this view, Nasr et al. (2014) recently observed that some of the stimuli that are known to strongly activate the PPA contain a large number of rectilinear edges. They further demonstrated that PPA response is modulated by rectilinearity for a range of non-scene images. Motivated by these results, we tested whether rectilinearity suffices to explain PPA selectivity for scenes. In the first experiment, we replicated the previous finding of modulation by rectilinearity in the PPA for arrays of 2-d shapes. However, two further experiments failed to find a rectilinearity effect for faces or scenes: high-rectilinearity faces and scenes did not activate the PPA any more strongly than low-rectilinearity faces and scenes. Moreover, the categorical advantage for scenes vs. faces was maintained in the PPA and two other scene-selective regions—the retrosplenial complex (RSC) and occipital place area (OPA)—when rectilinearity was matched between stimulus sets. We conclude that selectivity for scenes in the PPA cannot be explained by a preference for low-level rectilinear edges.

A Real-World Size Organization of Object Responses in Occipitotemporal Cortex

Human adults flawlessly and effortlessly navigate boundaries and obstacles in the immediately visible environment, a process we refer to as guided navigation. Neuroimaging work in adults suggests this ability involves the occipital place area (OPA) [1, 2]-a scene-selective region in the dorsal stream that selectively represents information necessary for visually guided navigation [3-9]. Despite progress in understanding the neural basis of visually guided navigation, however, little is known about how this system develops. Is navigationally relevant information processing present in the first few years of life? Or does this information processing only develop after many years of experience? Although a handful of studies have found selective responses to scenes (relative to objects) in OPA in childhood [10-13], no study has explored how more specific navigationally relevant information processing emerges in this region. Here, we do just that by measuring OPA responses to first-person perspective motion information-a proxy for the visual experience of actually navigating the immediate environment-using fMRI in 5- and 8-year-old children. We found that, although OPA already responded more to scenes than objects by age 5, responses to first-person perspective motion were not yet detectable at this same age and rather only emerged by age 8. This protracted development was specific to first-person perspective motion through scenes, not motion on faces or objects, and was not found in other scene-selective regions (the parahippocampal place area or retrosplenial complex) or a motion-selective region (MT). These findings therefore suggest that navigationally relevant information processing in OPA undergoes prolonged development across childhood.

The occipital place area represents the local elements of scenes

Perceived egocentric distance sensitivity and invariance across scene-selective cortex

Path integration, the constant updating of the navigator's knowledge of position and orientation during movement, requires both visuospatial knowledge and memory. This study aimed to develop a systems-level understanding of human path integration by examining the basic building blocks of path integration in humans. To achieve this goal, we used functional imaging to examine the neural mechanisms that support the tracking and memory of translational and rotational components of human path integration. Critically, and in contrast to previous studies, we examined movement in translation and rotation tasks with no defined end-point or goal. Navigators accumulated translational and rotational information during virtual self-motion. Activity in hippocampus, retrosplenial cortex (RSC), and parahippocampal cortex (PHC) increased during both translation and rotation encoding, suggesting that these regions track self-motion information during path integration. These results address current questions regarding distance coding in the human brain. By implementing a modified delayed match to sample paradigm, we also examined the encoding and maintenance of path integration signals in working memory. Hippocampus, PHC, and RSC were recruited during successful encoding and maintenance of path integration information, with RSC selective for tasks that required processing heading rotation changes. These data indicate distinct working memory mechanisms for translation and rotation, which are essential for updating neural representations of current location. The results provide evidence that hippocampus, PHC, and RSC flexibly track task-relevant translation and rotation signals for path integration and could form the hub of a more distributed network supporting spatial navigation. Hum Brain Mapp 37:3636-3655, 2016. © 2016 Wiley Periodicals, Inc.

Finding a path between locations is a routine task in daily life. Mental navigation is often used to plan a routeto a destination that is not visible from the current location. We first used functional magnetic resonance imaging (fMRI)and surface-based averaging methods to find high-level brain regions involved in imagined navigation between locationsin a building very familiar to each participant. This revealed a mental navigation network that includes the precuneus,retrosplenial cortex (RSC), parahippocampal place area (PPA), occipital place area (OPA), supplementary motor area(SMA), premotor cortex, and areas along the medial and anterior intraparietal sulcus. We then visualized retinotopic mapsin the entire cortex using wide-field, natural scene stimuli in a separate set of fMRI experiments. This revealed fivedistinct visual streams or ‘fingers’ that extend anteriorly into middle temporal, superior parietal, medial parietal,retrosplenial and ventral occipitotemporal cortex. By using spherical morphing to overlap these two data sets, we showedthat the mental navigation network primarily occupies areas that also contain retinotopic maps. Specifically, scene-selectiveregions RSC, PPA and OPA have a common emphasis on the far periphery of the upper visual field. Theseresults suggest that bottom-up retinotopic organization may help to efficiently encode scene and location information inan eye-centered reference frame for top-down, internally generated mental navigation. This study pushes the border ofvisual cortex further anterior than was initially expected.

Sex differences and laterality of rat hippocampus with respect to insulin-like growth factor-1 receptor (IGF-1R) and insulin receptor (InsR) expression as two important contributors to/regulators of developmental and cognitive functions were examined using real-time PCR and western blot analysis at P0, P7 and P14. Expression of the IGF-1R gene was lowest at P0 in all studied hippocampi. In males, we found the highest expression at P7 in the right hippocampus, and at P14 in the left one. In contrast, the peaked IGF-1R expression occurred at P7 in female hippocampi independent of laterality. Hippocampal InsR expression in males decreased significantly between P0 and P7, followed by a marked upregulation at P14. Conversely, the expression of InsR in females peaked at P7 and then decreased again significantly at P14. We found significant interhemispheric differences in IGF-1R mRNA levels in both male and female hippocampi at different time points. In contrast, we only found significant interhemispheric differences in InsR mRNA expression in P14 male rats, with higher values in the left hippocampus. Interestingly, changes in mRNA expression and in protein levels followed the same developmental pattern, indicating that IGF-1R and InsR transcription is not subject to modulatory effects during the first two weeks of development. These findings indicate that there are prominent interhemispheric and sex differences in IGF-1R and InsR expression in the developing rat hippocampus, suggesting a probable mechanism for the control of gender and laterality differences in development and function of the hippocampus.

L-DOPA induced increases in brain uric acid in an animal model of Parkinson's disease: A relationship to behavioral activation

The external morphology of the occipital lobe was investigated in 15 human post-mortem brains (30 hemispheres) fixed in formalin. We identified, described and measured the lengths of nine major human occipital sulci and five variable ones, comparing both types between individuals and hemispheres. Morphological variability of human occipital sulci is related to interindividual and interhemispheric differences in their presence, origin, type, segmentation, intersection and length. The major occipital sulci, particularly the parieto-occipital, the calcarine, the inferior lateral occipital and the anterior occipital sulci, as well as two points of their intersections (cuneal point and intersection of the transverse occipital and superior occipital sulcus) may be used as reliable anatomical landmarks for the location of architectonically and functionally defined human visual areas (V1, V2, V3, V3A, V5/MT+, LO1 and LO2) and during less invasive neurosurgical procedures in the cases of focal lesions within the occipital lobe. Two lateral occipital sulci (inferior and superior) were defined on the lateral surface of the occipital lobe. The variable lunate sulcus was studied and combining our results with those from histological and functional imaging studies, we suggest that the lunate sulci of human and nonhuman primates are not homologous.

The posterior parietal cortex has been implicated in spatial functions, including navigation. The hippocampal and parahippocampal region and the retrosplenial cortex are crucially involved in navigational processes and connections between the parahippocampal/retrosplenial domain and the posterior parietal cortex have been described. However, an integrated account of the organization of these connections is lacking. Here, we investigated parahippocampal connections of each posterior parietal subdivision and the neighboring secondary visual cortex using conventional retrograde and anterograde tracers as well as transsynaptic retrograde tracing with a modified rabies virus. The results show that posterior parietal as well as secondary visual cortex entertain overall sparse connections with the parahippocampal region but not with the hippocampal formation. The medial and lateral dorsal subdivisions of posterior parietal cortex receive sparse input from deep layers of all parahippocampal areas. Conversely, all posterior parietal subdivisions project moderately to dorsal presubiculum, whereas rostral perirhinal cortex, postrhinal cortex, caudal entorhinal cortex and parasubiculum all receive sparse posterior parietal input. This indicated that the presubiculum might be a major liaison between parietal and parahippocampal domains. In view of the close association of the presubiculum with the retrosplenial cortex, we included the latter in our analysis. Our data indicate that posterior parietal cortex is moderately connected with the retrosplenial cortex, particularly with rostral area 30. The relative sparseness of the connectivity with the parahippocampal and retrosplenial domains suggests that posterior parietal cortex is only a modest actor in forming spatial representations underlying navigation and spatial memory in parahippocampal and retrosplenial cortex. © 2017 Wiley Periodicals, Inc.

We have investigated the cortical efferent projections of the macaque monkey retrosplenial and posterior cingulate cortices by using (3)H-amino acids as anterograde tracers. All the injections produced extensive local connections to other portions of this region. There were also a number of extrinsic efferent cortical connections, many of which have not hitherto been reported. Major projections from the retrosplenial cortex were directed to the frontal lobe, with heaviest terminations in areas 46, 9, 10, and 11. There were also very substantial projections to the entorhinal cortex, presubiculum, and parasubiculum of the hippocampal formation, as well as to areas TH and TF of the parahippocampal cortex. Some injections led to labeling of area V4, the dorsal bank of the superior temporal sulcus, and area 7a of the parietal cortex. Projections from the posterior cingulate cortex innervated all these same regions, although the density of termination was different from the retrosplenial projections. The posterior cingulate cortex gave rise to additional projections to parietal area DP and to the cortex along the convexity of the superior temporal gyrus. The ventral portion of the posterior cingulate cortex (area 23v) gave rise to much denser efferent projections to the hippocampal formation than the dorsal portions (areas 23e and i). These connections are discussed in relation to the clinical syndromes of retrosplenial amnesia and topographic disorientation in humans commonly caused by lesions in the caudoventral portions of the retrosplenial and posterior cingulate cortices.

How do we find a target object in a cluttered visual scene? Targets carrying unique salient features can be found in parallel without directing attention, whereas targets defined by feature conjunctions or non-salient features need to be scrutinized in a serial attentional process in order to be identified. In this article, we review a series of experiments in which we used fMRI to probe the neural basis of this active search process in the human brain. In all experiments, we compared the fMRI signal between a difficult and an easy visual search (each performed without eye movements) in order to isolate neural activity reflecting the search process from other components such as stimulus responses and movement-related activity. The difficult search was either a conjunction search or a hard feature search and compared with an easy feature search, matched in visual stimulation and motor requirements. During both, the conjunction search and the hard feature search the frontal eye fields (FEF) and three parietal regions located in the intraparietal sulcus (IPS) were differentially activated: the anterior and posterior part of the intraparietal sulcus (AIPS, PIPS) as well as the junction of the intraparietal with the transverse occipital sulcus (IPTO). Only in PIPS, the modulation strength was most indistinguishable between conjunction and hard feature search. In a further experiment we showed that AIPS and IPTO are involved in visual conjunction search even in the absence of distractors; by contrast, the involvement of PIPS seems to depend on the presence of distractors. Taken together, these findings from these experiments demonstrate that all four key nodes of the human ’frontoparietal attention network’ are generally engaged in the covert selection process of visual search. But they also suggest that these areas play differential roles, perhaps reflecting different sub-processes in active search. We conclude by discussing a number of such sub-processes, such as the direction of spatial attention, visual feature binding, and the active suppression of distractors.