Search

The orbitofrontal cortex (OFC) plays a prominent role in signaling reward expectations. Two important features of rewards are their value (how good they are) and their specific identity (what they are). Whereas research on OFC has traditionally focused on reward value, recent findings point toward a pivotal role of reward identity in understanding OFC signaling and its contribution to behavior. Here, we review work in rodents, nonhuman primates, and humans on how the OFC represents expectations about the identity of rewards, and how these signals contribute to outcome-guided behavior. Moreover, we summarize recent findings suggesting that specific reward expectations in OFC are learned and updated by means of identity errors in the dopaminergic midbrain. We conclude by discussing how OFC encoding of specific rewards complements recent proposals that this region represents a cognitive map of relevant task states, which forms the basis for model-based behavior. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

When direct experience is unavailable, animals and humans can imagine or infer the future to guide decisions. Behavior based on direct experience versus inference may recruit partially distinct brain circuits. In rodents, the orbitofrontal cortex (OFC) contains neural signatures of inferred outcomes, and OFC is necessary for behavior that requires inference but not for responding driven by direct experience. In humans, OFC activity is also correlated with inferred outcomes, but it is unclear whether OFC activity is required for inference-based behavior. To test this, we used noninvasive network-based continuous theta burst stimulation (cTBS) in human subjects (male and female) to target lateral OFC networks in the context of a sensory preconditioning task that was designed to isolate inference-based behavior from responding that can be based on direct experience alone. We show that, relative to sham, cTBS targeting this network impairs reward-related behavior in conditions in which outcome expectations have to be mentally inferred. In contrast, OFC-targeted stimulation does not impair behavior that can be based on previously experienced stimulus–outcome associations. These findings suggest that activity in the targeted OFC network supports decision-making when outcomes have to be mentally simulated, providing converging cross-species evidence for a critical role of OFC in model-based but not model-free control of behavior.SIGNIFICANCE STATEMENTIt is widely accepted that the orbitofrontal cortex (OFC) is important for decision-making. However, it is less clear how exactly this region contributes to behavior. Here we test the hypothesis that the human OFC is only required for decision-making when future outcomes have to be mentally simulated, but not when direct experience with stimulus–outcome associations is available. We show that targeting OFC network activity in humans using network-based continuous theta burst stimulation selectively impairs behavior that requires inference but does not affect responding that can be based solely on direct experience. These results are in line with previous findings in animals and suggest a critical role for human OFC in model-based but not model-free behavior.

We summarize the operational realities of re-aluminizing 8.4-meter primary mirrors in-situ on the Large Binocular Telescope. We review the evaporative coating system design, and summarize its performance in the 16 coatings since 2005. A mostly manual system with long-handled mops and traditional chemicals is used to remove the old coating and to clean the glass surface. After cleaning, the telescope is moved to horizon-pointing orientation and the aluminizing belljar is mounted to the primary mirror cell using the overhead crane internal to the enclosure. We report on the multi-year struggle to understand variations in deposition rate among the 28 crucibles that evaporate the aluminum. We describe the challenges of making operational improvements to a system that must reliably coat one of the two primary mirrors every year, and we report on some lessons learned along the way.

Although it is widely accepted that the orbitofrontal cortex (OFC) is important for decision making, its precise contribution to behavior remains a topic of debate. While many loss of function experiments have been conducted in animals, causal studies of human OFC function are relatively scarce. This review discusses recent causal investigations into the human OFC, with an emphasis on advances in network-based brain stimulation approaches to indirectly perturb OFC function. Findings show that disruption of human OFC impairs decisions that require mental simulation of outcomes. Taken together, these results support the idea that human OFC contributes to decision making by representing a cognitive map of the task environment, facilitating inference of outcomes not yet experienced. Future work may utilize similar non-invasive approaches in clinical settings to mitigate decision making deficits in neuropsychiatric disorders.

Goal-directed behavior is sensitive to the current value of expected outcomes. This requires independent representations of specific rewards, which have been linked to orbitofrontal cortex (OFC) function. However, the mechanisms by which the human brain updates specific goals on the fly, and translates those updates into choices, have remained unknown. Here we implemented selective devaluation of appetizing food odors in combination with pattern-based neuroimaging and a decision-making task. We found that in a hungry state, participants chose to smell high-intensity versions of two value-matched food odor rewards. After eating a meal corresponding to one of the two odors, participants switched choices toward the low intensity of the sated odor but continued to choose the high intensity of the nonsated odor. This sensory-specific behavioral effect was mirrored by pattern-based changes in fMRI signal in lateral posterior OFC, where specific reward identity representations were altered after the meal for the sated food odor but retained for the nonsated counterpart. In addition, changes in functional connectivity between the OFC and general value coding in ventromedial prefrontal cortex (vmPFC) predicted individual differences in satiety-related choice behavior. These findings demonstrate how flexible representations of specific rewards in the OFC are updated by devaluation, and how functional connections to vmPFC reflect the current value of outcomes and guide goal-directed behavior.SIGNIFICANCE STATEMENTThe orbitofrontal cortex (OFC) is critical for goal-directed behavior. A recent proposal is that OFC fulfills this function by representing a variety of state and task variables (“cognitive maps”), including a conjunction of expected reward identity and value. Here we tested how identity-specific representations of food odor reward are updated by satiety. We found that fMRI pattern-based signatures of reward identity in lateral posterior OFC were modulated after selective devaluation, and that connectivity between this region and general value coding ventromedial prefrontal cortex (vmPFC) predicted choice behavior. These results provide evidence for a mechanism by which devaluation modulates a cognitive map of expected reward in OFC and thereby alters general value signals in vmPFC to guide goal-directed behavior.

(Abridged) We describe here the most ambitious survey currently planned in the optical, the Large Synoptic Survey Telescope (LSST). A vast array of science will be enabled by a single wide-deep-fast sky survey, and LSST will have unique survey capability in the faint time domain. The LSST design is driven by four main science themes: probing dark energy and dark matter, taking an inventory of the Solar System, exploring the transient optical sky, and mapping the Milky Way. LSST will be a wide-field ground-based system sited at Cerro Pach\'{o}n in northern Chile. The telescope will have an 8.4 m (6.5 m effective) primary mirror, a 9.6 deg$^2$ field of view, and a 3.2 Gigapixel camera. The standard observing sequence will consist of pairs of 15-second exposures in a given field, with two such visits in each pointing in a given night. With these repeats, the LSST system is capable of imaging about 10,000 square degrees of sky in a single filter in three nights. The typical 5$\sigma$ point-source depth in a single visit in $r$ will be $\sim 24.5$ (AB). The project is in the construction phase and will begin regular survey operations by 2022. The survey area will be contained within 30,000 deg$^2$ with $\delta, Comment: 57 pages, 32 color figures, version with high-resolution figures available from https://www.lsst.org/overview

Outcome-guided behavior requires knowledge about the current value of expected outcomes. Such behavior can be isolated in the reinforcer devaluation task, which assesses the ability to infer the current value of specific rewards after devaluation. Animal lesion studies demonstrate that orbitofrontal cortex (OFC) is necessary for normal behavior in this task, but a causal role for human OFC in outcome-guided behavior has not been established. Here, we used sham-controlled, non-invasive, continuous theta-burst stimulation (cTBS) to temporarily disrupt human OFC network activity by stimulating a site in the lateral prefrontal cortex that is strongly connected to OFC prior to devaluation of food odor rewards. Subjects in the sham group appropriately avoided Pavlovian cues associated with devalued food odors. However, subjects in the stimulation group persistently chose those cues, even though devaluation of food odors themselves was unaffected by cTBS. This behavioral impairment was mirrored in changes in resting-state functional magnetic resonance imaging (rs-fMRI) activity such that subjects in the stimulation group exhibited reduced OFC network connectivity after cTBS, and the magnitude of this reduction was correlated with choices after devaluation. These findings demonstrate the feasibility of indirectly targeting the human OFC with non-invasive cTBS and indicate that OFC is specifically required for inferring the value of expected outcomes.

SummaryMost real-world odors are complex mixtures of distinct molecular components. Olfactory systems can adopt different strategies to contend with this stimulus complexity. In elemental processing, odor perception is derived from the sum of its parts; in configural processing, the parts are integrated into unique perceptual wholes. Here we used gas-chromatography/mass-spectrometry techniques to deconstruct a complex natural food smell and assess whether olfactory salience is confined to the whole odor or is also embodied in its parts. By implementing an fMRI sensory-specific satiety paradigm, we identified reward-based changes in orbitofrontal cortex (OFC) for the whole odor and for a small subset of components. Moreover, component-specific changes in OFC-amygdala connectivity correlated with perceived value. Our findings imply that the human brain has direct access to the elemental content of a natural food odor, and highlight the dynamic capacity of the olfactory system to engage both object-level and component-level mechanisms to subserve behavior.

Searching for food, friends, and mates often begins with an airborne scent. Importantly, odor concentration rises with physical proximity to an odorous source, suggesting a framework for orienting within olfactory landscapes to optimize behavior. Here, we created a two-dimensional odor space composed purely of odor stimuli to model how a navigator encounters smells in a natural environment. We show that human subjects can learn to navigate in olfactory space and form predictions of to-be-encountered smells. During navigation, fMRI responses in entorhinal cortex and ventromedial prefrontal cortex take the form of grid-like representations with hexagonal periodicity and entorhinal grid strength scaled with behavioral performance across subjects. The identification of olfactory grid-like codes with 6-fold symmetry highlights a unique neural mechanism by which odor information can be assembled into spatially navigable cognitive maps, optimizing orientation, and path finding toward an odor source.

Perceptually similar stimuli often predict vastly different outcomes, requiring the brain to maintain specific associations in the face of potential ambiguity. This could be achieved either through local changes in stimulus representations, or through modulation of functional connections between stimulus-coding and outcome-coding regions. Here we test these competing hypotheses using classical conditioning of perceptually similar odours in the context of human fMRI. Pattern-based analyses of odour-evoked fMRI activity reveal that odour category, identity and value are coded in piriform (PC), orbitofrontal (OFC) and ventromedial prefrontal (vmPFC) cortices, respectively. However, we observe no learning-related reorganization of category or identity representations. Instead, changes in connectivity between vmPFC and OFC are correlated with learning-related changes in value, whereas connectivity changes between vmPFC and PC predict changes in perceived odour similarity. These results demonstrate that dissociable neural pathways support associative and perceptual representations of sensory stimuli., Animals often need to form specific associations between perceptually similar stimuli and the different outcomes they may predict. Howard et al. find that the human brain accomplishes this via enhanced coupling between stable codes of sensory features and flexible codes of stimulus reward value.

Ongoing sensory input is critical for shaping internal representations of the external world. Conversely, a lack of sensory input can profoundly perturb the formation of these representations. The olfactory system is particularly vulnerable to sensory deprivation, due to the widespread prevalence of allergic, viral, and chronic rhinosinusitis, but how the brain encodes and maintains odor information under such circumstances remains poorly understood. Here we combined functional magnetic resonance imaging (fMRI) with multivariate (pattern-based) analyses and psychophysical approaches to show that a seven-day period of olfactory deprivation induces reversible changes in odor-evoked fMRI activity in piriform cortex and orbitofrontal cortex (OFC). Notably, multivoxel ensemble codes of odor quality in OFC became decorrelated following deprivation, and the magnitude of these changes predicted subsequent olfactory perceptual plasticity. Our findings suggest that transient changes in these key olfactory brain regions are instrumental in sustaining odor perception integrity in the wake of disrupted sensory input.

Understanding how the human brain translates sensory impressions into conscious percepts is a key challenge of neuroscience research. Work in this area has overwhelmingly centered on the conscious experience of vision at the exclusion of the other senses—in particular, smell. We hypothesized that the orbitofrontal cortex (OFC) is a central substrate for olfactory conscious experience because of its privileged physiological role in odor processing. Combining functional magnetic resonance imaging, peripheral autonomic recordings, and olfactory psychophysics, we studied a case of complete anosmia (smell loss) in a patient with circumscribed traumatic brain injury to the right OFC. Despite a complete absence of conscious olfaction, the patient exhibited robust “blind smell,” as indexed by reliable odor-evoked neural activity in the left OFC and normal autonomic responses to odor hedonics during presentation of stimuli to the left nostril. These data highlight the right OFC’s critical role in subserving human olfactory consciousness.

It is widely assumed that the thalamus is functionally irrelevant for the sense of smell. Although animal studies suggest that the mediodorsal (MD) thalamus links primary olfactory (piriform) cortex to olfactory neocortical projection sites in orbitofrontal cortex (OFC), this transthalamic route is regarded to be inconsequential, particularly compared with a direct monosynaptic pathway linking piriform cortex and OFC. In this study, we combined functional magnetic resonance imaging with novel effective connectivity techniques to measure attention-dependent network coherence within direct (nonthalamic) and indirect (transthalamic) olfactory pathways. Human subjects were presented with (or without) an odor and with (or without) a tone, while selectively attending to either modality. Attention to odor significantly modulated neural coupling within the indirect pathway, strengthening MD thalamus–OFC connectivity. Critically, these effects were modality specific (odor > tone attention), directionally sensitive (forward > backward connections), and selective to route (indirect > direct pathway). Our findings support the idea that the human transthalamic pathway is an active modulatory target of olfactory attention. The results imply that olfaction, like all other sensory modalities, requires a thalamic relay, if only to consciously analyze a smell.

Objectives: Diffusion tensor magnetic resonance imaging (DT-MRI) assesses the integrity of white matter (WM) tracts in the brain. Children with bipolar disorder (BPD) may have WM abnormalities that precede illness onset. To more fully examine this possibility, we scanned children with DSM-IV BPD and compared them to healthy peers and children at risk for BPD (AR-BPD), defined as having a first-degree relative with the disorder. Methods: Ten children with BPD, eight healthy controls (HC), and seven AR-BPD, similar in age, had MRI scans on a 1.5 Tesla GE scanner, including a standard DT-MRI sequence (T2-EPI) with 25 axial slices. Fractional anisotropy (FA) values were compared between groups to determine regions of significant difference (p

Nervous systems must encode information about the identity of expected outcomes to make adaptive decisions. However, the neural mechanisms underlying identity-specific value signaling remain poorly understood. By manipulating the value and identity of appetizing food odors in a pattern-based imaging paradigm of human classical conditioning, we were able to identify dissociable predictive representations of identity-specific reward in orbitofrontal cortex (OFC) and identity-general reward in ventromedial prefrontal cortex (vmPFC). Reward-related functional coupling between OFC and olfactory (piriform) cortex and between vmPFC and amygdala revealed parallel pathways that support identity-specific and -general predictive signaling. The demonstration of identity-specific value representations in OFC highlights a role for this region in model-based behavior and reveals mechanisms by which appetitive behavior can go awry.

Sleep can strengthen memory for emotional information, but whether emotional memories can be specifically targeted and modified during sleep is unknown. In human subjects who underwent olfactory contextual fear conditioning, re-exposure to the odorant context in slow-wave sleep promoted stimulus-specific fear extinction, with parallel reductions of hippocampal activity and reorganization of amygdala ensemble patterns. Thus, fear extinction may be selectively enhanced during sleep, even without re-exposure to the feared stimulus itself.

Patients with early-stage Alzheimer's disease exhibit perceptual deficits in odour identification, often before the appearance of overt memory loss. This impairment coincides with the initial accumulation of pathological lesions in limbic olfactory brain regions. Although these data imply that odour stimuli may be effectively used as biological probes of limbic dysfunction, the precise neural mechanisms underlying the olfactory deficits in early Alzheimer's disease remain poorly understood. In the current study, we combined functional magnetic resonance imaging with an olfactory cross-adaptation paradigm to test the hypothesis that perceptual codes of odour quality in posterior piriform cortex are degraded in patients with Alzheimer's disease. In elderly control subjects, sequential presentation of qualitatively similar (versus qualitatively different) odourant pairs elicited cross-adapting responses in posterior piriform cortex, in accord with the pattern observed in healthy young adults. However, this profile was significantly blunted in patients with Alzheimer's disease, reflecting a functional disruption of odour quality coding in this olfactory brain area. These results highlight the potential of olfactory functional magnetic resonance imaging as a non-invasive bioassay of limbic functional integrity, and suggest that such an index could possibly aid in the early diagnosis of Alzheimer's disease. Furthermore, as a putative lesion model of odour quality processing in the human brain, our study suggests a causal role of posterior piriform cortex in differentiating olfactory objects.

We performed cerebellum segmentation and parcellation on magnetic resonance images from right-handed boys, aged 6-13 years, including 22 boys with autism [16 with language impairment (ALI)], 9 boys with Specific Language Impairment (SLI), and 11 normal controls. Language-impaired groups had reversed asymmetry relative to unimpaired groups in posterior-lateral cerebellar lobule VIIIA (right side larger in unimpaired groups, left side larger in ALI and SLI), contralateral to previous findings in inferior frontal cortex language areas. Lobule VIIA Crus I was smaller in SLI than in ALI. Vermis volume, particularly anterior I-V, was decreased in language-impaired groups. Language performance test scores correlated with lobule VIIIA asymmetry and with anterior vermis volume. These findings suggest ALI and SLI subjects show abnormalities in neurodevelopment of fronto-corticocerebellar circuits that manage motor control and the processing of language, cognition, working memory, and attention.

Efficient recognition of odorous objects universally shapes animal behavior and is crucial for survival. To distinguish kin from non-kin, mate from non-mate, food from non-food, organisms must be able to create meaningful perceptual representations of odor qualities and categories. It is currently unknown where, and in what form, the brain encodes information about odor quality. By combining functional magnetic resonance imaging (fMRI) with multivariate (pattern-based) techniques, we show that spatially distributed ensemble activity in human posterior piriform cortex (PPC) coincides with perceptual ratings of odor quality, such that odorants with more (or less) similar fMRI patterns were perceived as more (or less) alike. Critically, these effects were not observed in anterior piriform cortex, amygdala, or orbitofrontal cortex, demonstrating that ensemble coding of odor categorical perception is regionally specific for PPC. These findings substantiate theoretical models emphasizing the importance of distributed piriform templates for the perceptual reconstruction of odor object quality.

Learning to associate sensory cues with threats is critical for minimizing aversive experience. The ecological benefit of associative learning relies on accurate perception of predictive cues, but how aversive learning enhances perceptual acuity of sensory signals, particularly in humans, is unclear. We combined multivariate functional magnetic resonance imaging with olfactory psychophysics to show that initially indistinguishable odor enantiomers (mirror-image molecules) become discriminable after aversive conditioning, paralleling the spatial divergence of ensemble activity patterns in primary olfactory (piriform) cortex. Our findings indicate that aversive learning induces piriform plasticity with corresponding gains in odor enantiomer discrimination, underscoring the capacity of fear conditioning to update perceptual representation of predictive cues, over and above its well-recognized role in the acquisition of conditioned responses. That completely indiscriminable sensations can be transformed into discriminable percepts further accentuates the potency of associative learning to enhance sensory cue perception and support adaptive behavior.

Diffusion tensor magnetic resonance imaging (DT-MRI) assesses the integrity of white matter (WM) tracts in the brain. Children with bipolar disorder (BPD) may have WM abnormalities that precede illness onset. To more fully examine this possibility, we scanned children with DSM-IV BPD and compared them to healthy peers and children at risk for BPD (AR-BPD), defined as having a first-degree relative with the disorder.Ten children with BPD, eight healthy controls (HC), and seven AR-BPD, similar in age, had MRI scans on a 1.5 Tesla GE scanner, including a standard DT-MRI sequence (T2-EPI) with 25 axial slices. Fractional anisotropy (FA) values were compared between groups to determine regions of significant difference (p0.05).Compared to HC, children with BPD had decreased FA in right and left superior frontal tracts, including the superior longitudinal fasciculus I (SLF I) and the cingulate-paracingulate WM (CG-PAC(WM)). In addition, the BPD group had reduced FA in left orbital frontal WM and the right corpus callosum body. Compared to AR-BPD, children with BPD showed reduced FA in the right and left CG-PAC(WM). Both the BPD and AR-BPD groups showed reduced FA relative to HC in bilateral SLF I.The bilateral SLF I finding in both the BPD and AR-BPD groups may represent a trait-based marker or endophenotype of the disorder. The finding of decreased FA in the right and left CG-PAC(WM) in children with BPD compared to the other two groups may represent a disease-state related finding.

Where studied sufficiently, trace fossil assemblages generally have proven to be significant environ­ mental indicators in the Upper Cretaceous of the Western Interior. The full potential of such assemblages is yet to be realized, however, whether in reconstruction of local depositional settings or in evaluation of regional cyclic sedimentation. Ichnologic studies of nearshore elastics in Utah and offshore carbonates in Kansas constitute provisional models for both local and regional environmental analyses, including assessments of the problems and principles involved. The regional aspects, especially, require considerable additional reconnaissance, development, and testing before such models can be employed routinely.

Ophiomorpha, traditionally one of the most revered environmental indicators among trace fossils, is by no means an unambiguous entity in facies analysis and palaeoecology. Callianassa major, the best known modern analog for the Ophiomorpha-organism, is itself variable ethologically and ecologically, and it is only one of several species of thalassinidean shrimp that routinely construct knobby walled burrows. Other analogs presently known include not only additional species of Callianassa but also certain species of Upogebia and possibly Axius. Each species has its own peculiar range of habits and habitats. The collective result, in both recent and ancient settings, is a broad spectrum of burrow morphologies and environmental distributions. Each occurrence therefore must be evaluated independently, in terms of the specific evidence at hand. Only in this light is Ophiomorpha a valuable aid in environmental interpretation. The gross morphology of Ophiomorpha overlaps with that of such ichnogenera as Ardelia, Gyrolithes, Teichichnus, and Thalassinoides, yet these burrow forms should be retained as separate taxa. Reconized species of Ophiomorpha, also somewhat intergradational, include O. borneensis Keij, O. irregulaire n. sp., and O. nodosa Lundgren. Taxonomic criteria are based upon modes of wall construction rather than upon burrow configuration.

Configuration of the present Georgia coast, with its broad expanses of salt marsh and intricate tidal drainages behind Pleistocene—Holocene barrier islands, implies the filling of an extensive backbarrier lagoonal system. However, riverine and salt marsh estuaries dominate the modern depositional setting and reconstructed vertical sequences suggest that backbarrier filling was accomplished by estuarine processes. Backbarrier sediments exhibit considerable diversity in grain size and physical and biogenic sedimentary structures. Principal sediment textures include clean to muddy coarse and fine sand, mud and, to a lesser extent, shells, pebbles, and mud and bedrock clasts. Physical sedimentary structures, many modified by bioturbation, include large-scale cross-bedding (trough and planar) with graded sets, small-scale crossbedding (ripple lamination and flaser, wavy and lenticular bedding), laminated to interbedded sand and mud, and rare pebble or shell beds. Ebb-oriented structures predominate over flood-oriented ones. Except in upper reaches of riverine estuaries, biogenic sedimentary structures typically are diverse and abundant. characteristic lebensspuren include polychaete dwelling tubes, decapod and polychaete burrows, ray holes, and bioturbate textures imparted by amphipods, ophiuroids, bivalves and anemones. Patterns of bioturbation are controlled to some extent by sediment type, salinity levels and rates of deposition and physical reworking of sediments. Although intensity of bioturbation generally increases seaward, bioturbate textures are more readily preservable in the lower-energy, middle reaches of estuaries. Because of numerous local Pleistocene sediment sources and local variations in hydrographic regimes, the stratigraphic record of salt marsh estuaries differs relatively little from that of riverine estuaries. The basic sequence, in ascending order, typically consists of: (1) channel-lag and (or) channel-fill deposits; (2) estuarine accretionary beds; (3) point bar, tidal flat and shoal sediments; and (4) channel margin and salt marsh deposits.

More than 20 trace fossil species occur in marine facies of the Cretaceous Star Point and Blackhawk formations in the Book Cliffs and Wasatch Plateau provinces of Utah. Major genera include Ancorichnus, Arenicolites, Aulichnites, Chondrites, Conichnus, Cylindrichnus, Medousichnus, Ophiomorpha, Palaeophycus, Planolites, Rosselia, Schaubcylindrichnus, Scolicia, Skolithos, Teichichnus, Teredolites, and Thalassinoides. Newly named taxa include Ancorichnus capronus, Medousichnus loculatus, and Rosselia chonoides.Most trace fossils occur in characteristic, albeit intergradational ichnofacies correlative with major lithofacies of regressive nearshore to offshore sequences. The latter include foreshore, foreshore–shoreface transition, shoreface, and offshore facies. Landward facies are typified by clean, well sorted, well stratified, sparsely burrowed sandstones. Seaward facies, except where interrupted by hummocky bedded sandstones, exhibit successively less pure, less well sorted and stratified, more intensely bioturbated, finer grained sandstones, siltstones, and mudstones.Characteristic ichnofacies and lithofacies in the Cretaceous of east-central Utah should provide potentially useful models for reconstruction of nearshore to offshore sequences elsewhere, especially in the Western Interior Region of North America.

The Mesozoic succession of Kachchh, western India, is a classic example of the value of trace fossils in the interpretaion of depositional sequences. Because this sequence has traditionally been referred to as Gondwana and because the previous emphasis has been on body fossils, a misconception has been established concerning this fascinating nearshore sequence. Preliminary investigations of generally well-preserved physical and biogenic structures in the Mesozoic rocks of Kachchh reveal that the entire succession represents deposition in a shallow marine coastal setting, i.e., lagoons, embayments, tidal flats, estuarine channels, shoals and shallow shelf. The Patcham Formation shows poor preservation of trace fossils due to lack of appropriate lithologies. The Chari Formation contains a rich ichnofauna. Of special interest are horizons of “bioconglomerates” showing reworked fillings of Thalassinoides burrows and pholad borings. The Katrol Formation exhibits a diversified and well-preserved assemblage of burrows, including an unusual feeding burrow here recorded for the first time. The Umia Formation though devoid of body fossils contains a rich and varied assemblage of ichnofossils. The uppermost part of this unit, the Bhuj Member, contains several thick horizons of densely Rhizocorallium-bioturbated sand, which supports a marine setting contrary to the general belief of its fluvial origin.

Well-exposed vertical sequences of Pleistocene shoreline deposits are rare on the coastal plain of the southeastern United States. An important exception is an exposure along the St. Mary's River on the Georgia-Florida state line. This outcrop contains an excellent depositional strike section of a prograding offshore, shoreface, foreshore and backshore sequence with well-preserved physical and biogenic sedimentary structures. Offshore sediments are composed of highly bioturbated, muddy fine sand. Distinct burrows and bedding become progressively more abundant upward through a transition zone into shoreface deposits. The shoreface is dominated by the trace fossil Ophiomorpha nodosa and physical sedimentary structures are poorly preserved. Foreshore sediments contain low-angle seaward dipping beds, high-angle landward dipping beds and ripple laminae. Heavy-mineral accumulations in the backshore accentuate bedding and biogenic structures such as ghost crab and insect burrows and bioturbation by amphipods. Direct correlation of most primary physical and biogenic sedimentary structures and textures can be made between the Pleistocene and Holocene beach-to-offshore facies assemblages. However, our studies of the Pleistocene indicate that the existing Holocene vertical sequence model for the Georgia coast needs to be modified to account for biogenically produced post-depositional effects.

Sampling efficiencies of the Smith-McIntyre grab and the USNEL spade corer were compared based on macrofaunal abundance, biomass, and size. The spade corer’s efficiency was greater than that of the grab sampler; this is attributed to its greater depth penetration.

SUMMARY Examination of the primary sedimentary texture of rocks and sediments by X-radiography can be extended to include the study of bioturbation and burrowing by living organisms. This technique involves making time-lapse X-radiographs while the animals are in the process of disturbing the sediment. Artificially and naturally stratified sediments are contained in plexiglass aquaria connected to a continuously flowing seawater system. The burrowing animals to be studied are introduced into these aquaria and the effect of their activities on the sediments is recorded by X-radiography over a period of hours, days or weeks.

An inexpensive, portable vibrocorer has been developed for acquisition of cores of sand on barrier islands where transportation facilities are extremely limited. This corer is self-contained and requires a minimum of machine shop alteration to commercially available equipment. Cores to depths of 12 feet have been taken.

Summary Background Uncertainty shapes our perception of the world and the decisions we make. Two aspects of uncertainty are commonly distinguished: uncertainty in previously acquired knowledge (prior) and uncertainty in current sensory information (likelihood). Previous studies have established that humans can take both types of uncertainty into account, often in a way predicted by Bayesian statistics. However, the neural representations underlying these parameters remain poorly understood. Results By varying prior and likelihood uncertainty in a decision-making task while performing neuroimaging in humans, we found that prior and likelihood uncertainty had quite distinct representations. Whereas likelihood uncertainty activated brain regions along the early stages of the visuomotor pathway, representations of prior uncertainty were identified in specialized brain areas outside this pathway, including putamen, amygdala, insula, and orbitofrontal cortex. Furthermore, the magnitude of brain activity in the putamen predicted individuals' personal tendencies to rely more on either prior or current information. Conclusions Our results suggest different pathways by which prior and likelihood uncertainty map onto the human brain and provide a potential neural correlate for higher reliance on current or prior knowledge. Overall, these findings offer insights into the neural pathways that may allow humans to make decisions close to the optimal defined by a Bayesian statistical framework.

A lack of detailed facies studies has resulted in a false impression of the Mesozoic depositional setting in Kachchh, western India (previously, Kachchh has been termed ‘Kutch’ or ‘Cutch’). In addition, designation of part of this sequence as Gondawana implies, by tradition, a predominantly non-marine origin. Recently, we examined these Jurassic–Cretaceous units and found numerous wave-built sedimentary structures that have been previously overlooked or unreported, abundant marine trace fossils, and highly bioturbated and glauconite-rich beds. Thus, we now propose a marine origin for the entire Kachchh succession. This interpretation has important implications regarding similar sequences around the Indian plate margin.

A device that separates a sediment suspension into four parts has been designed and tested for use with marine sediments. Operation of the splitter is rapid, clean, efficient, and suitable for a routine laboratory. The precision of the splitter was tested by comparing granulometric data from the splits. Comparison of the median particle size among the splits reveals little variation, and, although the mean, standard deviation and skewness show more discrepancy, the range of values is considered small enough for the splits to be designated as representative splits.

Box core X-ray radiographs from estuarine and closely adjacent nearshore shelf sediments of Georgia were used to study interrelationships among detrital valve orientations, sediment textures, and physical and biogenic sedimentary structures. The cores represent preserved sediment sequences and thus should be more indicative of the rock record than shell orientations observed on substrate surfaces. With little bioturbation, physical processes mainly govern shell configurations. Horizontal concave-down valves predominate in large- and small-scale crossbedded sands, laminated sands, and thin shell beds; inclined concave-down valves also are common, together with lesser numbers of horizontal concave-up valves. Vertical and inclined concave-up valves predominate in thick shell beds. shell-filled burrows, and thin shell beds consisting of shell-ornamented Diopatra tube fragments; horizontal concave-up valves also are common in each of these, and inclined concave-down valves are abundant in thick shell beds. With progressively more intense bioturbation, as is commonplace in estuarine and nearshore shelf sediments, proportions of horizontal and inclined concave-down valves decrease as those of vertical and inclined concave-up valves increase, the latter two becoming dominant. The abundance of horizontal concave-up valves increases initially but decreases between 90 and 100 percent bioturbation. Some of these results, especially the predominance of vertical and inclined concave-up valves, differ from those of previous workers. Small sizes of dominant Georgia bivalves probably account for much of the difference. Because of pronounced local variations, large numbers of measurements also are imperative.

In sedimentologie and stratigraphie studies we should consider most trace fossils for what they are: sedimentary structures. Used in this context, trace fossils can furnish valuable information concerning (1) general depositional processes, (2) episodes of local deposition and erosion, and (3) characteristics of currents, substrate consistency, and in some instances, causes of sediment sorting. This information is important in and for itself, and it should also be utilized more fully by paleoecologists and others concerned with the reconstruction of ancient depositional environments.

A new interpretation of late Pleistocene sea levels on the U.S. Atlantic continental shelf is based on in-place lagoonal and salt-marsh sediments obtained from vibra-cores. These data show sea levels during the last Wisconsinan transgression were about 30 meters shallower than is indicated by existing sea-level curves.