Marine wild-capture fisheries after nuclear war.

Nuclear war, beyond its devastating direct impacts, is expected to cause global climatic perturbations through injections of soot into the upper atmosphere. Reduced temperature and sunlight could drive unprecedented reductions in agricultural production, endangering global food security. However, the effects of nuclear war on marine wild-capture fisheries, which significantly contribute to the global animal protein and micronutrient supply, remain unexplored. We simulate the climatic effects of six war scenarios on fish biomass and catch globally, using a state-of-the-art Earth system model and global process-based fisheries model. We also simulate how either rapidly increased fish demand (driven by food shortages) or decreased ability to fish (due to infrastructure disruptions), would affect global catches, and test the benefits of strong prewar fisheries management. We find a decade-long negative climatic impact that intensifies with soot emissions, with global biomass and catch falling by up to 18 ± 3% and 29 ± 7% after a US-Russia war under business-as-usual fishing-similar in magnitude to the end-of-century declines under unmitigated global warming. When war occurs in an overfished state, increasing demand increases short-term (1 to 2 y) catch by at most ∼30% followed by precipitous declines of up to ∼70%, thus offsetting only a minor fraction of agricultural losses. However, effective prewar management that rebuilds fish biomass could ensure a short-term catch buffer large enough to replace ∼43 ± 35% of today's global animal protein production. This buffering function in the event of a global food emergency adds to the many previously known economic and ecological benefits of effective and precautionary fisheries management.

Use of supplemental anti-HBc testing of donors showing non-discriminating reactive results in multiplex nucleic acid testing.

BACKGROUND AND OBJECTIVES: The Korean Red Cross began nucleic acid amplification testing (NAT) for HIV and HCV in February 2005, and added HBV NAT beginning in June 2012. The current NAT system utilizes a multiplex assay for simultaneous detection of HBV DNA, HCV RNA and HIV-1 RNA. For samples that are reactive in the multiplex assay, we do specific tests for each virus. However, there have been cases of non-discriminated reactive (NDR) results which appear to be the result of non-specific reactions or cross-contamination, although some cases are considered to arise from the presence of low levels of HBV DNA due to occult hepatitis B infection. MATERIALS AND METHODS: We examined the incidence of NDR results in previous donations of some NAT-reactive donors. Additionally, for those donors with NDR results, we performed an HBV core antibody (anti-HBc) assay. RESULTS: From November 2015 to March 2016, there were 408 NAT-reactive donors. Of these, nineteen HBV NAT-reactive donors showed a history of NDR results in the past donations. Seven donors showed NDR results more than once. Of 771 NDR donors, 362 (47·0%) were anti-HBc reactive. CONCLUSION: The NDR donors had a substantially higher rate of anti-HBc reactivity than other blood donors indicating that some with anti-HBc reactivity represent donors with occult HBV. Therefore, the incorporation of an anti-HBc testing for NDR donors could improve blood safety testing for the Korean Red Cross.

An effective diagnostic strategy for accurate detection of RhD variants including Asian DEL type in apparently RhD-negative blood donors in Korea.

BACKGROUND AND OBJECTIVES: The purpose of this study was to provide an effective RHD genotyping strategy for the East Asian blood donors. MATERIAL AND METHODS: RhD phenotyping, weak D testing and RhCE phenotyping were performed on 110 samples from members of the RhD-negative club, private organization composed of RhD-negative blood donors, in the GwangJu-Chonnam region of Korea. The RHD promoter, intron 4, and exons 7 and 10 were analysed by real-time PCR. Two nucleotide changes (c.1227 G>A, and c.1222 T>C) in exon 9 were analysed by sequencing. RESULTS: Of 110 RhD-negative club members, 79 (71·8%) showed complete deletion of the RHD gene, 10 (9·1%) showed results consistent with RHD-CE-D hybrid, and 21 (19·1%) showed amplification of RHD promoter, intron 4, and exons 7 and 10. Of the latter group, 16 (14·5%) were in the DEL blood group including c.1227 G>A (N = 14) and c.1222 T>C (N = 2), 2 (1·8%) were weak D, 1(0·9%) was partial D, and 2 (1·8%) were undetermined. The RhD-negative phenotype samples consisted of 58 C-E-c+e+, 19 C-E+c+e+, 3 C-E+c+e-, 21 C+E-c+e-, 6 C+E-c+e+ and 3 C+E-c-e + . Notably, all 58 samples with the C-E-c+e+ phenotype were revealed to have complete deletion of the RHD gene. The C-E-c+e+ phenotype showed 100% positive predictive value for detecting D-negative cases. CONCLUSIONS: RHD genotyping is not required in half of D-negative cases. We suggest here an effective RHD genotyping strategy for accurate detection of RhD variants in apparently RhD-negative blood donors in East Asia.

Morphological and morphometric study of the androgenetic alopecic scalp using two- and three-dimensional analysis comparing regional differences.

BACKGROUND: Androgenetic (male-type) alopecia (AGA) is caused by genetic and androgenetic effects. The progression of baldness results in smaller hair papillae, thinner hair and a shortened hair cycle. Alopecia occurs mainly in the frontal region and, to a lesser extent, in the occipital region. OBJECTIVES: The morphological differences in the hair follicular units between the alopecic frontal scalp and the vertex and occipital regions were compared using cross-sectional histology and three-dimensional reconstruction. METHODS: Skin specimens were obtained from the frontal, vertex and occipital regions of 24 male human cadavers with fully progressed AGA, and from the frontal region of 32 normal cadaveric scalps. These specimens were fixed, processed using routine histological methods, serially sectioned at a thickness of 10 µm and then stained with Masson's trichrome. The serial sections were reconstructed three-dimensionally using 'Reconstruct' software. RESULTS: The ratios between the numbers of terminal and vellus hairs in the frontal and occipital regions in the AGA scalps were 0·2 : 1 and 3·5 : 1, respectively. Almost all of the hair follicles in the frontal region were vellus hair follicles. The sebaceous gland and arrector pili muscle were larger in the frontal region than in the occipital region. CONCLUSIONS: The morphology of the AGA scalp has been characterized. The terminal-to-vellus hair ratio in the occipital (normal) region was different from that in the frontal (alopecic) region. Moreover, sebaceous glands were larger in the frontal alopecic region than in the occipital region. These larger glands may be associated with other dermatological pathologies, such as seborrhoeic dermatitis.

Production of Endoglucanase, Beta-glucosidase and Xylanase by Bacillus licheniformis Grown on Minimal Nutrient Medium Containing Agriculture Residues.

Bacillus licheniformis was grown in minimal nutrient medium containing 1% (w/v) of distillers dried grain with soluble (DDGS), palm kernel meal (PKM), wheat bran (WB) or copra meal (CM), and the enzyme activity of endoglucanase, ß-glucosidase, xylanase and reducing sugars was measured to investigate a possibility of using cost-effective agricultural residues in producing cellulolytic and hemicellulolytic enzymes. The CM gave the highest endoglucanase activity of 0.68 units/mL among added substrates at 48 h. CM yielded the highest titres of 0.58 units/ml of ß-glucosidase, compared to 0.33, 0.23, and 0.16 units/mL by PKM, WB, and DDGS, respectively, at 72 h. Xylanase production was the highest (0.34 units/mL) when CM was added. The supernatant from fermentation of CM had the highest reducing sugars than other additional substrates at all intervals (0.10, 0.12, 0.10, and 0.11 mg/mL respectively). It is concluded that Bacillus licheniformis is capable of producing multiple cellulo- and hemicellololytic enzymes for bioethanol production using cost-effective agricultural residues, especially CM, as a sole nutrient source.

Comparing the efficacy of different methods of faecal microbiota transplantation via oral capsule, oesophagogastroduodenoscopy, colonoscopy, or gastric tube.

BACKGROUND: The increasing prevalence of multidrug-resistant organism (MDRO) carriage poses major challenges to medicine as healthcare costs increase. Recently, faecal microbiota transplantation (FMT) has been discussed as a novel and effective method for decolonizing MDRO. AIM: To compare the efficacy of different FMT methods to optimize the success rate of decolonization in patients with MDRO carriage. METHODS: This prospective cohort study enrolled patients with MDRO carriages from 2018 to 2021. Patients underwent FMT via one of the following methods: oral capsule, oesophagogastroduodenoscopy (EGD), colonoscopy, or gastric tube. FINDINGS: A total of 57 patients underwent FMT for MDRO decolonization. The colonoscopy group required the shortest time for decolonization, whereas the EGD group required the longest (24.9 vs 190.4 days, P = 0.022). The decolonization rate in the oral capsule group was comparable to that in the EGD group (84.6% vs 85.7%, P = 0.730). An important clinical factor associated with decolonization failure was antibiotic use after FMT (odds ratio = 6.810, P = 0.008). All four groups showed reduced proportions of MDRO species in microbiome analysis after FMT. CONCLUSION: Compared to other conventional methods, the oral capsule is an effective FMT method for patients who can tolerate an oral diet. The discontinuation of antibiotics after FMT is a key factor in the success of decolonization.

Upregulation of Fas and downregulation of CD94/NKG2A inhibitory receptors on circulating natural killer cells in patients with new-onset psoriasis.

BACKGROUND: Psoriasis has been considered as a T-helper 1 cell-mediated autoimmune disease driven by collaboration with multiple components of innate and acquired immune cells. Natural killer (NK) cells have been shown to bridge innate and acquired immunity, and thus could potentially contribute to the pathophysiology of psoriasis. OBJECTIVES: To investigate the phenotypic changes of circulating NK cells in patients with new-onset psoriasis. METHODS: Fifteen patients with plaque psoriasis (eight women and seven men) who visited our clinic after their first episode of psoriasis and did not have a history of previous systemic therapy or phototherapy participated in this study. Peripheral blood mononuclear cells were isolated and stained with a panel of antibodies against cell surface receptors expressed on T and/or NK cells and analysed by flow cytometry. RESULTS: As compared with normal healthy volunteers, patients with new-onset psoriasis showed no significant changes in numbers of peripheral NK, NK-T or T cells. NK activating receptors 2B4, CD48, NKG2D, CD16 and CD56 were found to be unchanged in new-onset psoriasis. However, the expression of Fas (activation-induced death receptor) was upregulated, whereas the expression of the NK inhibitory receptors CD94 and NKG2A was dramatically reduced on NK cells of new-onset psoriasis. These changes occurred at the level of mean fluorescent intensity, but minimally affected percentages of cells expressing Fas, CD94 and NKG2A. CONCLUSIONS: Our findings demonstrate that changes in the expression of Fas and CD94/NKG2A receptors on NK cells may occur during new-onset psoriasis, and are likely to contribute to the pathogenesis of psoriasis.

Neural correlates of a decision in the dorsolateral prefrontal cortex of the macaque.

To make a visual discrimination, the brain must extract relevant information from the retina, represent appropriate variables in the visual cortex and read out this representation to decide which of two or more alternatives is more likely. We recorded from neurons in the dorsolateral prefrontal cortex (areas 8 and 46) of the rhesus monkey while it performed a motion discrimination task. The monkey indicated its judgment of direction by making appropriate eye movements. As the monkey viewed the motion stimulus, the neural response predicted the monkey's subsequent gaze shift, hence its judgment of direction. The response comprised a mixture of high-level oculomotor signals and weaker visual sensory signals that reflected the strength and direction of motion. This combination of sensory integration and motor planning could reflect the conversion of visual motion information into a categorical decision about direction and thus give insight into the neural computations behind a simple cognitive act.

Effects of chemical treatments on pH and bacterial population in poultry litter: a laboratory experiment.

1. The goal of this study was to evaluate the effects of three chemical treatments on pH and bacterial populations (total aerobic bacteria and gram-negative bacteria) in poultry litter under laboratory conditions. 2. Litter obtained from poultry houses was treated with three chemical treatments (alum, AlCl(3) and FeSO(4)) at the same concentration (8 g/100 g litter), while untreated litter served as a control. The study was conducted for 3 weeks. 3. All of the chemical treatments reduced total aerobic bacteria (22 to 87% of the untreated control) and gram-negative bacteria (63 to 99% of the untreated controls) populations and lowered litter pH values (5.95 to 6.64). However, a significant difference in gram-negative bacteria did not exist among chemical treatments at 0, 1 and 2 weeks. 4. These results suggest that the reduction in total aerobic bacteria and gram-negative bacteria populations is highly related to a decrease in litter pH, and acidifying treatment (alum, AlCl(3) and FeSO(4)) of poultry litter may serve as a means to help the reduction in pathogen populations and to improve economical benefits under commercial production conditions.

Controlling superconductivity by tunable quantum critical points.

The heavy fermion compound CeRhIn5 is a rare example where a quantum critical point, hidden by a dome of superconductivity, has been explicitly revealed and found to have a local nature. The lack of additional examples of local types of quantum critical points associated with superconductivity, however, has made it difficult to unravel the role of quantum fluctuations in forming Cooper pairs. Here, we show the precise control of superconductivity by tunable quantum critical points in CeRhIn5. Slight tin-substitution for indium in CeRhIn5 shifts its antiferromagnetic quantum critical point from 2.3 GPa to 1.3 GPa and induces a residual impurity scattering 300 times larger than that of pure CeRhIn5, which should be sufficient to preclude superconductivity. Nevertheless, superconductivity occurs at the quantum critical point of the tin-doped metal. These results underline that fluctuations from the antiferromagnetic quantum criticality promote unconventional superconductivity in CeRhIn5.

Spatial correlation of suppressive and excitatory receptive fields with direction selectivity of complex cells in cat striate cortex.

The aim of the study was to account for direction selectivity of visual cortical neurons through systematic positional mismatch between excitatory and suppressive influences on each neuron. Direction-selective complex neurons were therefore recorded from striate cortex of cats lightly anaesthetized with halothane in nitrous oxide-oxygen. All but small residual eye movements were eradicated with intravenous gallamine triethiodide. Excitatory receptive field (ERF) dimensions and centring were quantified with optimal sine-wave grating stimuli, appropriately windowed to limit them to variable locations along and across the receptive field (RF) centre. Related suppressive receptive fields (SRFS) were similarly mapped during binocular conditioning, induced by an optimal grating applied to the other eye and drifting continuously in each neuron's preferred direction. Its purpose was to elevate ongoing levels of discharge to reveal often concealed null suppression. ERF and SRF profiles were systematically offset, especially along the line of preferred direction such that, for stimuli moving in the non-preferred direction, the SRF lay ahead of the ERF. Derivations of ERFS and SRFS during conditioning, within a single batch of trials, excluded eye movements as a source of positional mismatch. It is concluded that this mismatch may provide the basis for direction selectivity and the emergence of null suppression.

Simultaneous determination of delta-aminolevulinic acid, porphobilinogen, levulinic acid and glycine in culture broth by capillary electrophoresis.

Capillary electrophoretic simultaneous determination of a mixture containing delta-aminolevulinic acid, porphobilinogen, levulinic acid and glycine was investigated. With increases in the sodium tetraborate buffer concentration (5-70 mM), resolution of the four components was improved, but the migration time was increased. Alternatively, with increases in the applied voltage (5-22.5 kV), a shortened migration time was seen but this adversely affected resolution. The components were separated with high resolution by using a fused-silica capillary column (75 cm x 75 microm I.D.) filled with 30 mM sodium tetraborate buffer (pH 9.3-9.4) under the applied voltage of 20 kV (constant voltage mode). When the established method was applied to the culture broth of Rhodopseudomonas sphaeroides, a photosynthetic bacterium, the four components mentioned above were separated with good resolution. Furthermore, the use of this method would provide a fast, sensitive and specific method for monitoring the administration of delta-aminolevulinic acid in photodynamic cancer therapy, for the measurement of delta-aminolevulinic acid dehydratase activity in erythrocytes, and for testing the delta-aminolevulinic acid assay and for impurities in drug formulation.

Serum leptin, IGF-I and insulin levels in preterm infants receiving parenteral nutrition during the first week of life.

Leptin is involved in the regulation of body weight through a feedback signal between adipose tissue and the satiety center, to decrease food intake and increase energy expenditure. Newborn infants experience physiological weight loss during the first week of life. The leptin level may be decreased to enhance food intake and to decrease energy expenditure for physiological adaptation during early postnatal days. Insulin-like growth factor-I (IGF-I) and insulin are involved in the regulation of perinatal growth. Leptin might be interrelated with IGF-I or insulin, since both of these have adipogenic and somatotropic effects. We therefore hypothesized that leptin, IGF-I and insulin would be decreased during the first week of life, concurrently with physiological weight loss. Thirty preterm AGA infants (birth weight 1.574+/-313 g; GA 31.9+/-2.2 wk) were studied. All infants received parenteral nutrition from the third day after birth. Leptin was significantly decreased during the first week of life, and insulin was significantly increased at day 7 vs. day 1 and day 3. IGF-I did not change during the first week of life. Leptin was positively correlated with body weight (r = 0.368, p<0.01), body mass index (r = 0.267, p<0.05), and serum IGF-I (r = 0.330, p <0.01), but not with serum insulin. The percent of weight reduction during the first week of life was not correlated with the percent of leptin reduction during the first week of life. In conclusion, leptin was significantly decreased and positively correlated with body weight and IGF-I during the first week of life. Changes of leptin and insulin might be related to postnatal adaptation in metabolism, but the exact role of leptin, IGF-I and insulin in postnatal physiological weight loss is not clear.

Prospective evaluation of perinatal risk factors for cerebral palsy and delayed development in high risk infants.

Prematurity, intrauterine infection and perinatal brain injury have been reported to be significant risk factors of cerebral palsy (CP). We examined the perinatal predictors of cerebral palsy and delayed development (DD) in 184 high risk infants. Thirty-five infants were diagnosed as cerebral palsy and delayed development at 12 months corrected age. Antenatal, intrapartum, and neonatal factors were prospectively evaluated in 2 groups of high risk infants compared with controls; Group A (n = 79), infants weighing less than 2,000 g; Group B (n = 43), infants weighing 2,000 g or more. In univariate analysis, there were no significant antenatal and intrapartum factors associated with cerebral palsy and delayed development in either group. We found that significant postnatal risk factors of CP in group A included sepsis (p = 0.008), BPD (bronchopulmonary dysplasia) (p = 0.028), IVH (intraventricular hemorrhage) (p = 0.042), ventriculomegaly (VM) (p = 0.001) and a longer duration of mechanical ventilation (p = 0.001); while in group B, sepsis (p = 0.047) and neonatal seizure (p = 0.027) were significant risk factors. In multivariate analysis, sepsis in group B was a moderate risk factor of CP (OR (odds ratio) 1.47; 95% CI (confidence interval) 1.02-2.13). In conclusion, neonatal sepsis may contribute to the development of cerebral palsy and delayed development. We suggest that high risk infants who have sepsis should be carefully followed for cerebral palsy and delayed development. The prevention of cerebral palsy may be feasible by decreasing neonatal risk factors such as sepsis during the neonatal period.

Temperature behavior of dielectric and piezoelectric properties of samarium-doped lead titanate ceramics.

The dielectric and electromechanical coupling properties of Sm-doped and Mn-doped PbTiO(3) ceramics were investigated from 4.2 to 300 K. The upper and lower limits of the ceramic dielectric and piezoelectric properties were calculated by averaging the single-domain constants that were determined from a phenomenological theory. Comparisons of the measured and calculated properties were then made. The measured dielectric permittivity epsilon(T)(33) and piezoelectric strain coefficient d(33) appear to be mainly due to the averaging of the intrinsic single-domain response. The large piezoelectric and electromechanical anisotropies present in modified PbTiO(3) ceramics also appear to be an intrinsic property of the material. The piezoelectric coefficient d(31), as well as the planar coupling coefficient k(p), was found to have very small values over two temperature regions, from 120 to 170 K and from 240 to 270 K.

Effect of vaccination against foot-and-mouth disease on growth performance of Korean native goat (Capra hircus coreanae).

The objectives of this study were 1) to evaluate the effects of vaccination against foot-and-mouth disease (FMD) on growth performance, nutrient digestibility, hematological parameters, and behavior in a ruminant animal and 2) to investigate a possible strategy for reducing its adverse effect. A total of 12 Korean native goats (Capra hircus coreanae; 19.8 ± 2.9 kg) were used in a crossover design with 3 experimental periods and 3 treatments, randomized and balanced for counteracting possible carry-over effects. The treatments were 1) control, 2) co-injection with a commercially available dipyrone (CADI), and 3) supplementation with γ-amino butyric acid (GABA) at 10 g/kg in concentrate mix. Each period lasted 4 wk, and the vaccination against FMD was performed at 2 wk after the start of each period. The goats were individually housed in a metabolic cage and fed ad libitum with a diet consisting of bermuda grass and commercial concentrate mix (6:4, wt/wt). Dry matter intake, ADG, nutrients digestibility, hematological parameters, and behavioral activities of the goats were measured before and after vaccination. Although DMI was not decreased (P > 0.05), ADG was decreased by the vaccination to the goats (P < 0.01). The total number of leukocytes was increased while that of erythrocytes was decreased by the FMD vaccination (P < 0.01). The vaccination shortened standing time while extended lying time and the time spent in drinking (P < 0.05). The treatment by CADI reduced the adverse effect of vaccination on ADG and goat behavior compared with control and GABA treatment (P < 0.05). We concluded that the FMD vaccination decreased ADG of the goats without depression of diet intake, and CADI may attenuate the adverse effect of the FMD vaccination.

Riboswitches in eubacteria sense the second messenger cyclic di-GMP.

Cyclic di-guanosine monophosphate (di-GMP) is a circular RNA dinucleotide that functions as a second messenger in diverse species of bacteria to trigger wide-ranging physiological changes, including cell differentiation, conversion between motile and biofilm lifestyles, and virulence gene expression. However, the mechanisms by which cyclic di-GMP regulates gene expression have remained a mystery. We found that cyclic di-GMP in many bacterial species is sensed by a riboswitch class in messenger RNA that controls the expression of genes involved in numerous fundamental cellular processes. A variety of cyclic di-GMP regulons are revealed, including some riboswitches associated with virulence gene expression, pilus formation, and flagellum biosynthesis. In addition, sequences matching the consensus for cyclic di-GMP riboswitches are present in the genome of a bacteriophage.

Role of suppression in shaping orientation and direction selectivity of complex neurons in cat striate cortex.

1. Single binocularly driven complex neurons in cat striate cortex were recorded extracellularly under nitrous oxide-oxygen-halothane anesthesia and muscle relaxant. Orientational/directional tuning was initially derived for each eye in turn, with sine wave gratings of optimal spatial frequency and velocity, while the other eye viewed a uniform field. 2. For the dominant eye, previously concealed suppression was revealed against elevated levels of firing induced with a conditioning grating, drifting continuously in the preferred direction, simultaneously presented to the nondominant eye. During steady-state binocular conditioning, orientational/directional tuning was reestablished for the dominant eye. In a subset of cells, tuning curves during conditioning were also derived for the reverse configuration, i.e., nondominant eye tuning, dominant eye conditioning: results were qualitatively identical to those for conditioning through the nondominant eye. 3. Neurons were initially segregated into five groups, according to the observed suppression profiles induced at nonoptimal orientations/directions during conditioning: Type 1, suppression centered on orthogonal directions; Type 2, suppression around null directions; Type 3, null suppression combined with orthogonal suppression; Type 4, lateral suppression, maximal for directions immediately flanking those inducing excitation; and Type 5, the residue of cells, totally lacking suppression or showing complex or variable suppression. 4. Sharpness of (excitatory) tuning was correlated with directionality and with class of suppression revealed during binocular conditioning. Direction-biased neurons were more sharply orientation tuned than direction-selective neurons; similarly, neurons exhibiting lateral or orthogonal suppression during conditioning were more sharply tuned than neurons with null suppression. 5. Application of suboptimal directions of conditioning weakened the induced suppression but altered none of its main characteristics. 6. The relationship between excitation, suppression, and spatial frequency was investigated by comparing tuning curves for the dominant eye at several spatial frequencies, without and during conditioning. End-stopped neurons preferred lower spatial frequencies and higher velocities of motion than non-end-stopped neurons. Confirming previous reports, suppression in some neurons was still present for spatial frequencies above the cutoff frequency for excitation, demonstrating the tendency for suppression to be more broadly spatial frequency tuned than excitation. 7. Scatterplots of strength of suppression, in directions orthogonal and opposite maximal excitation, partially segregated neurons of Types 1-3. Clearer segregation of Types 1-4 was obtained by curve-fitting to profiles of suppression, and correlating half-width of tuning for suppression with the angle between the directions of optimal suppression and optimal excitation in each neuron. 8. Two interpretations are advanced-the first, based on three discrete classes of inhibition, orthogonal, null and lateral; the second, based on only two classes, orthogonal and null/lateral--in which null and lateral suppression are manifestations of the same inhibitory mechanism operating, respectively, on broadly tuned direction-selective or on sharply tuned direction-biased neurons. Orthogonal suppression may be untuned for direction, whereas lateral and null suppression are broadly direction tuned. Within each class, suppression is more broadly spatial frequency tuned than excitation. 9. It is concluded that orientational/directional selectivity of complex cells at different spatial frequencies is determined by the balance between tuned excitation and varying combinations of relatively broadly distributed or untuned inhibition.

Simulated optic flow and extrastriate cortex. I. Optic flow versus texture.

A locomoting observer sees a very different visual scene than an observer at rest: images throughout the visual field accelerate and expand, and they follow approximately radial outward paths from a single origin. This so-called optic flow field is presumably used for visual guidance, and it has been suggested that particular areas of visual cortex are specialized for the analysis of optic flow. In the cat, the lateral suprasylvian visual area (LS) is a likely candidate. To test the hypothesis that LS is specialized for analysis of optic flow fields, we recorded cell responses to optic flow displays. Stimulus movies simulated the experience of a cat trotting slowly across an endless plain covered with small balls. In different simulations we varied the size of balls, their organization (randomly or regularly dispersed), and their color (all one gray level, or multiple shades of gray). For each optic flow movie, a "texture" movie composed of the same elements but lacking optic flow cues was tested. In anesthetized cats, > 500 neurons in LS were studied with a variety of movies. Most (70%) of 454 visually responsive cells responded to optic flow movies. Visually responsive cells generally preferred optic flow to texture movies (69% of those responsive to any movie). The direction in which a movie was shown (forward or reverse) was also an important factor. Most cells (68%) strongly preferred forward motion, which corresponded to visual experience during locomotion.