Place and Environment in the Ongoing Evolution of Cognitive Neuroscience.

Cognitive science today increasingly is coming under the influence of embodied, embedded, extended, and enactive perspectives, superimposed on the more traditional cybernetic, computational assumptions of classical cognitive research. Neuroscience has contributed to a greatly enhanced understanding of brain function within the constraints of the traditional cognitive science approach, but interpretations of many of its findings can be enriched by the newer alternative perspectives. Here, we note in particular how these frameworks highlight the cognitive requirements of an animal situated within its particular environment, how the coevolution of an organism's biology and ecology shape its cognitive characteristics, and how the cognitive realm extends beyond the brain of the perceiving animal. We argue that these insights of the embodied cognition paradigm reveal the central role that "place" plays in the cognitive landscape and that cognitive scientists and philosophers alike can gain from paying heed to the importance of a concept of place. We conclude with a discussion of how this concept can be applied with respect to cognitive function, species comparisons, ecologically relevant experimental designs, and how the "hard problem" of consciousness might be approached, among its other implications.

Behavioral indicators of heterogeneous subjective experience in animals across the phylogenetic spectrum: Implications for comparative animal phenomenology.

This behavioral study was undertaken to provide empirical evidence in favor of or opposed to the notion that animals across a wide breadth of the animal kingdom have subjective (personal) experience that varies with their lifestyles, ecological constraints, or phylogeny. Twelve species representing two invertebrate phyla and six vertebrate classes were observed unobtrusively in 15-min episodes, during which three modes of behavior (volitional, interactive, and egocentric) were quantified according to the frequency, variety, and dynamism of each mode. Volitional behavior was the most prevalent and dynamic mode for nearly all species, largely without regard to phylogenetic position. Interactive behavior likewise varied inconsistently across the entire evolutionary spectrum. Egocentric behavior was concentrated among the avian and mammalian species, but evidence of it were observed in the invertebrate species as well. Diagrams of the matrix constructed from the three qualitative modes and three quantitative attributes for each mode provide a metaphorical representation of the unique experiential profile of each species. To the extent that these behavioral measures correlate with the nature of the animal's subjective experience, they support the growing view that phenomenology is heterogeneous, multimodal, and non-linear in extent across the animal kingdom.

Proposed Missions to Collect Samples for Analyzing Evidence of Life in the Venusian Atmosphere.

The recent and still controversial claim of phosphine detection in the venusian atmosphere has reignited consideration of whether microbial life might reside in its cloud layers. If microbial life were to exist within Venus' cloud deck, these microorganisms would have to be multi-extremophiles enclosed within the cloud aerosol particles. The most straightforward approach for resolving the question of their existence is to obtain samples of the cloud particles and analyze their interior. While developing technology has made sophisticated in situ analysis possible, more detailed information could be obtained by examining samples with instrumentation in dedicated ground-based facilities. Ultimately, therefore, Venus Cloud-level Sample Return Missions will likely be required to resolve the question of whether living organisms exist in the clouds of Venus. Two multiphase mission concepts are currently under development for combining in situ analyses with a sample return component. The Venus Life Finder architecture proposes collection of cloud particles in a compartment suspended from a balloon that floats for weeks at the desired altitude, while the Novel solUtion for Venus explOration and Lunar Exploitation (NUVOLE) concept involves a glider that cruises within the cloud deck for 1200 km collecting cloud aerosol particles through the key regions of interest. Both architectures propose a rocket-driven ascent with the acquired samples transported to a high venusian orbit as a prelude to returning to Earth or the Moon. Both future conceptual missions with their combined phases will contribute valuable information relative to the habitability of the clouds at Venus, but their fulfillment is decades away. We suggest that, in the meantime, a simplification of a glider cloud-level sample collection scenario could be accomplished in a shorter development time at a lower cost. Even if the cloud particles are not organic and show no evidence of living organisms, they would reveal critical insights about the natural history and evolution of Venus.

Life Unknown: Preliminary Scheme for a Magnetotrophic Organism.

No magnetotrophic organism on Earth is known to use magnetic fields as an energy source or the storage of information. However, a broad diversity of life forms is sensitive to magnetic fields and employs them for orientation and navigation, among other purposes. If the magnetic field strength were much larger, such as that on planets around neutron stars or magnetars, metabolic energy could be obtained from these magnetic fields in principle. Here, we introduce three hypothetical models of magnetotrophic organisms that obtain energy via the Lorentz force. Even if an organism uses magnetic fields only as an energy source, but otherwise is relying on biochemistry, this organism would be by definition a magnetotrophic form of life as we do not know it.

Disialogangliosides and TNFα alter gene expression for cytokines and chemokines in primary brain cell cultures.

Gangliosides have long been implicated in multiple pathologies affecting the central nervous system. Empirical studies have suggested the possibility that gangliosides, particularly GD3, work in tandem with pro-inflammatory cytokines, especially tumor necrosis factor alpha (TNFα), to initiate or facilitate cell death in the CNS. As a step toward unraveling the metabolic pathways activated in the pathogenesis of brain cell death, we have surveyed gene expression for a host of cytokines and chemokines in primary brain cell cultures exposed to GD3, GD1b, and TNFα for 24 h. An initial screen of 98 genes on a focused mini-array revealed the expression of at least 28 genes related to cell growth, death, or inflammation in our system of mixed cells cultured from neonatal rat brains. Clear evidence of a differential response to the gangliosides or TNFα was seen in 12 genes. Quantitative PCR was used to validate the response of six of these genes. We found that both GD3 and GD1b, but not TNFα, up-regulated expression of macrophage inflammatory protein 3 (MIP3A) and interleukin-1 receptor 1 (IL1R1), but down-regulated fibroblast growth factor 13 (FGF13). The expression of FGF receptor activating protein 1 (FRAG1) and interleukin-3 receptor alpha (IL3RA) was down-regulated by GD3. Exposure to TNFα resulted in a dramatic up-regulation of IL3RA and chemokine ligand 2 (CCL2), both of which have been implicated in multiple sclerosis. Our results provide strong evidence that the expression of these genes might be critical links in the metabolic cascades leading to cell degeneration and death in the brain.

Renewed Perspectives on the Deep Roots and Broad Distribution of Animal Consciousness.

The vast majority of neurobiologists have long abandoned the Cartesian view of non-human animals as unconscious automatons-acknowledging instead the high likelihood that mammals and birds have mental experiences akin to subjective consciousness. Several lines of evidence are now extending those limits to all vertebrates and even some invertebrates, though graded in degrees as argued originally by Darwin, correlated with the complexity of the animal's brain. A principal argument for this view is that the function of consciousness is to promote the survival of an animal-especially one actively moving about-in the face of dynamic changes and real-time contingencies. Cognitive ecologists point to the unique features of each animal's environment and the specific behavioral capabilities that different environments invoke, thereby suggesting that consciousness must take on a great variety of forms, many of which differ substantially from human subjective experience.

Sex and diet affect the behavioral response of rats to chronic mild stressors.

To investigate the interaction between sex, stressors, and dietary choice in rats, a preferred diet under the influence of chronic mild stressors was empirically determined to consist of soybeans and cookies in addition to lab chow. This preferred mixed diet was then tested for its influence on several behavioral tests at the end of prolonged exposure to the potential stressors. Rats of both sexes decreased their frequency of rearing but increased their attention to novelty in response to stressors. In the elevated plus maze, diet interacted with exposure to stressors to influence time spent in the open arm in females but not males. In the forced swim test, females but not males fed the mixed diet showed increased immobility, whether exposed to stressors or not. Finally, females but not males showed a differential effect of diet under stressors on the sucrose preference test, but this result was confounded by estrus cycling, demonstrating the importance of this factor in analyzing behavior in females. These results suggest that male and female rats differ in their susceptibility to the behavioral-modifying influences of stressors. And to the extent that diet serves as a coping mechanism, it does so differently in males and females.

Chronic mild stressors and diet affect gene expression differently in male and female rats.

While depression is reportedly more prevalent in women than men, a neurobiological basis for this difference has not been documented. Chronic mild stress (CMS) is a widely recognized animal model, which uses mild and unpredictable environmental stressors to induce depression. Studies of chronic stress, mainly in males, have reported an increase in the relative intake of "comfort food" as a means of counteracting the effects of stress. This study was designed to test the hypothesis that genes for certain neurotrophic factors, stress markers, and appetite regulators would be expressed differentially in male and female rats exposed to chronic, mild stressors with access to a preferred diet. Gene expression for neuropeptide Y was upregulated in females purely in response to stressors, whereas that for the epidermal growth factor receptor (EGFR) and arginine vasopressin (AVP) in males and fatty acid synthase (FASN) in females responded primarily to diet. Genes for brain-derived neurotrophic factor (BDNF), AVP, and the cocaine-amphetamine regulator of transcription (CART) in males, and leptin in females, showed a significant response to the interaction between stressors and diet. Every affected gene showed a different pattern of expression in males and females. This study confirms the intimate relationship between dietary intake and response to stress at the molecular level, and emphasizes the sex- and gene-specific nature of those interactions. Therefore, it supports a neurobiological basis for differences in the affective state response to stress in males and females.

Prenatal exposure to the acetylcholinesterase inhibitor methanesulfonyl fluoride alters forebrain morphology and gene expression.

Methanesulfonyl fluoride (MSF) is a CNS-selective acetylcholinesterase (AChE) inhibitor, currently being developed and tested for the treatment of symptoms of Alzheimer's disease. We have previously confirmed that a single in utero exposure to MSF at clinically appropriate doses inhibits AChE activity in fetal rat brain by 20%, and when administered throughout gestation, MSF achieves a 40% level of inhibition. Here, we show that rats chronically exposed in utero to MSF display marked sex-specific differences in morphological development of the cerebral cortical layers compared with controls at 7 days of age. Forebrain size and cortical thickness were increased in females and decreased in males. An analysis of gene expression in neonate brain on the day of birth revealed sex-specific differential expression of over 25 genes, including choline acetyltransferase (ChAT), which were affected by prenatal MSF exposure. Many of these genes are associated with sexual differentiation and brain development, while others are involved in more generalized cellular and metabolic processes. The changes observed in cortical morphology and gene expression suggest a critical developmental role for AChE in the fetal nervous system, most likely through its effect on cholinergic neurotransmission.

Gene expression following traumatic brain injury in humans: analysis by microarray.

Global changes in gene expression were analyzed in pericontusional tissue taken during surgery from 4 patients with traumatic brain injury (TBI), in cerebral infarction tissue from a patient with vasculitis and in normal brain tissue resected during craniotomy for meningioma. Of approximately 1,200 genes showing some level of expression by cDNA microarray hybridization, 104 ( approximately 8%) showed differential expression in traumatized tissue. Genes controlling transcriptional regulation, intermediary and energy metabolism, signal transduction, and intercellular adhesion and recognition were differentially affected most often. Four genes previously shown to be associated with TBI (c-Fos, Jun B, HSP70, and Zif/268) were all found to be up-regulated in at least one TBI patient. Thus, the robust response to TBI of several immediate early genes is confirmed, and a longer list of candidate genes from other functional categories is suggested for further studies aimed at understanding the molecular and cellular consequences of TBI.

Strategy for modeling putative multilevel ecosystems on Europa.

A general strategy for modeling ecosystems on other worlds is described. Two alternative biospheres beneath the ice surface of Europa are modeled, based on analogous ecosystems on Earth in potentially comparable habitats, with reallocation of biomass quantities consistent with different sources of energy and chemical constituents. The first ecosystem models a benthic biosphere supported by chemoautotrophic producers. The second models two concentrations of biota at the top and bottom of the subsurface water column supported by energy harvested from transmembrane ionic gradients. Calculations indicate the plausibility of both ecosystems, including small macroorganisms at the highest trophic levels, with ionotrophy supporting a larger biomass than chemoautotrophy.

Energy cycling and hypothetical organisms in Europa's ocean.

While Europa has emerged as a leading candidate for harboring extraterrestrial life, the apparent lack of a source of free energy for sustaining living systems has been argued. In this theoretical analysis, we have quantified the amount of energy that could in principle be obtained from chemical cycling, heat, osmotic gradients, kinetic motion, magnetic fields, and gravity in Europa's subsurface ocean. Using reasonable assumptions based on known organisms on Earth, our calculations suggest that chemical oxidation-reduction cycles in Europa's subsurface ocean could support life. Osmotic and thermal gradients, as well as the kinetic energy of convection currents, also represent plausible alternative sources of energy for living systems at Europa. Organisms thriving on these gradients could interact with each other to form the complex energy cycling necessary for establishing a stable ecosystem.

Reassessing the possibility of life on venus: proposal for an astrobiology mission.

With their similar size, chemical composition, and distance from the Sun, Venus and Earth may have shared a similar early history. Though surface conditions on Venus are now too extreme for life as we know it, it likely had abundant water and favorable conditions for life when the Sun was fainter early in the Solar System. Given the persistence of life under stabilizing selection in static environments, it is possible that life could exist in restricted environmental niches, where it may have retreated after conditions on the surface became untenable. High-pressure subsurface habitats with water in the supercritical liquid state could be a potential refugium, as could be the zone of dense cloud cover where thermoacidophilic life might have retreated. Technology based on the Stardust Mission to collect comet particles could readily be adapted for a pass through the appropriate cloud layer for sample collection and return to Earth.

A sulfur-based survival strategy for putative phototrophic life in the venusian atmosphere.

Several observations indicate that the cloud deck of the venusian atmosphere may provide a plausible refuge for microbial life. Having originated in a hot proto-ocean or been brought in by meteorites from Earth (or Mars), early life on Venus could have adapted to a dry, acidic atmospheric niche as the warming planet lost its oceans. The greatest obstacle for the survival of any organism in this niche may be high doses of ultraviolet (UV) radiation. Here we make the argument that such an organism may utilize sulfur allotropes present in the venusian atmosphere, particularly S(8), as a UV sunscreen, as an energy-converting pigment, or as a means for converting UV light to lower frequencies that can be used for photosynthesis. Thus, life could exist today in the clouds of Venus.

Novel odors affect gene expression for cytokines and proteinases in the rat amygdala and hippocampus.

Olfaction in rodents provides an excellent modality for the study of cellular mechanisms of information processing and storage, since a single occurrence of precisely timed stimuli has high survival value. We have followed up preliminary evidence of cytokine and proteinase involvement in normal (as opposed to pathologically-induced) brain plasticity by surveying for the presence of these factors in the olfactory circuitry of the rat. Genes for 25-30 common cytokines and their receptors, and over 30 cell matrix and adhesion molecules were found to be expressed across the olfactory bulb, insular cortex, amygdala, and dorsal hippocampus. We then measured by real-time PCR the transcriptional expression of seven of these genes following a one-time exposure to the novel odor of blueberry bars or cornnuts, in contrast to presentation of the familiar odor of lab chow. In the amygdala significant up-regulation of interleukin-1 receptor 1 (IL1r1), interleukin-4 receptor (IL4r), fibroblast growth factor 13 (FGF13), and cathepsin-H (CtsH) was observed in males in response to the odor of cornnuts only. Changes were less consistent and widespread in the hippocampus, but were again sex specific for three genes: cathepsin-L (CtsL), matrix metalloproteinase-14 (MMP-14) and MMP-16. Our results show that transcription for several specific cytokines, growth factors, and proteinases responds to a one-time exposure to a novel odor, in a manner that tends to be region- and sex-specific. This suggests considerable variation in the way that olfactory information is processed at the cellular level in different brain regions and by the two sexes.

Pavilion lake microbialites: morphological, molecular and biochemical evidence for a cold-water transition to colonial aggregates.

The presence of microbialite structures in a freshwater, dimictic mid-latitudelake and their establishment after the last ice age about 10,000 years ago is puzzling.Freshwater calcite microbialites at Pavilion Lake, British Columbia, Canada, consist of acomplex community of microorganisms that collectively form large, ordered structuredaggregates. This distinctive assemblage of freshwater calcite microbialites was studied through standard microbial methods, morphological observations, phospholipid fatty acid(PLFA) analysis, DNA sequencing and the identification of quorum sensing molecules.Our results suggest that the microbialites may represent a transitional form from theexclusively prokaryotic colonial precursors of stromatolites to the multicellular organismicaggregates that give rise to coral reefs.

A two-tiered approach to assessing the habitability of exoplanets.

In the next few years, the number of catalogued exoplanets will be counted in the thousands. This will vastly expand the number of potentially habitable worlds and lead to a systematic assessment of their astrobiological potential. Here, we suggest a two-tiered classification scheme of exoplanet habitability. The first tier consists of an Earth Similarity Index (ESI), which allows worlds to be screened with regard to their similarity to Earth, the only known inhabited planet at this time. The ESI is based on data available or potentially available for most exoplanets such as mass, radius, and temperature. For the second tier of the classification scheme we propose a Planetary Habitability Index (PHI) based on the presence of a stable substrate, available energy, appropriate chemistry, and the potential for holding a liquid solvent. The PHI has been designed to minimize the biased search for life as we know it and to take into account life that might exist under more exotic conditions. As such, the PHI requires more detailed knowledge than is available for any exoplanet at this time. However, future missions such as the Terrestrial Planet Finder will collect this information and advance the PHI. Both indices are formulated in a way that enables their values to be updated as technology and our knowledge about habitable planets, moons, and life advances. Applying the proposed metrics to bodies within our Solar System for comparison reveals two planets in the Gliese 581 system, GJ 581 c and d, with an ESI comparable to that of Mars and a PHI between that of Europa and Enceladus.

The prospect of alien life in exotic forms on other worlds.

The nature of life on Earth provides a singular example of carbon-based, water-borne, photosynthesis-driven biology. Within our understanding of chemistry and the physical laws governing the universe, however, lies the possibility that alien life could be based on different chemistries, solvents, and energy sources from the one example provided by Terran biology. In this paper, we review some of these possibilities. Silanes may be used as functional analogs to carbon molecules in environments very different from Earth; solvents other than water may be compatible for life-supporting processes, especially in cold environments, and a variety of energy sources may be utilized, some of which have no Terran analog. We provide a detailed discussion of two possible habitats for alien life which are generally not considered as such: the lower cloud level of the Venusian atmosphere and Titan's surface environment.