The neural code for "face cells" is not face-specific

Face cells are neurons that respond more to faces than to non-face objects. They are found in clusters in the inferotemporal cortex, thought to process faces specifically, and, hence, studied using faces almost exclusively. Analyzing neural responses in and around macaque face patches to hundreds of objects, we found graded response profiles for non-face objects that predicted the degree of face selectivity and provided information on face-cell tuning beyond that from actual faces. This relationship between non-face and face responses was not predicted by color and simple shape properties but by information encoded in deep neural networks trained on general objects rather than face classification. These findings contradict the long-standing assumption that face versus non-face selectivity emerges from face-specific features and challenge the practice of focusing on only the most effective stimulus. They provide evidence instead that category-selective neurons are best understood by their tuning directions in a domain-general object space.

Human visual consciousness involves large scale cortical and subcortical networks independent of task report and eye movement activity

The full neural circuits of conscious perception remain unknown. Using a visual perception task, we directly recorded a subcortical thalamic awareness potential (TAP). We also developed a unique paradigm to classify perceived versus not perceived stimuli using eye measurements to remove confounding signals related to reporting on conscious experiences. Using fMRI, we discovered three major brain networks driving conscious visual perception independent of report: first, increases in signal detection regions in visual, fusiform cortex, and frontal eye fields; and in arousal/salience networks involving midbrain, thalamus, nucleus accumbens, anterior cingulate, and anterior insula; second, increases in frontoparietal attention and executive control networks and in the cerebellum; finally, decreases in the default mode network. These results were largely maintained after excluding eye movement-based fMRI changes. Our findings provide evidence that the neurophysiology of consciousness is complex even without overt report, involving multiple cortical and subcortical networks overlapping in space and time.

Improving the accuracy of single-trial fMRI response estimates using GLMsingle

Advances in artificial intelligence have inspired a paradigm shift in human neuroscience, yielding large-scale functional magnetic resonance imaging (fMRI) datasets that provide high-resolution brain responses to thousands of naturalistic visual stimuli. Because such experiments necessarily involve brief stimulus durations and few repetitions of each stimulus, achieving sufficient signal-to-noise ratio can be a major challenge. We address this challenge by introducing GLMsingle, a scalable, user-friendly toolbox available in MATLAB and Python that enables accurate estimation of single-trial fMRI responses (glmsingle.org). Requiring only fMRI time-series data and a design matrix as inputs, GLMsingle integrates three techniques for improving the accuracy of trial-wise general linear model (GLM) beta estimates. First, for each voxel, a custom hemodynamic response function (HRF) is identified from a library of candidate functions. Second, cross-validation is used to derive a set of noise regressors from voxels unrelated to the experiment. Third, to improve the stability of beta estimates for closely spaced trials, betas are regularized on a voxel-wise basis using ridge regression. Applying GLMsingle to the Natural Scenes Dataset and BOLD5000, we find that GLMsingle substantially improves the reliability of beta estimates across visually-responsive cortex in all subjects. Comparable improvements in reliability are also observed in a smaller-scale auditory dataset from the StudyForrest experiment. These improvements translate into tangible benefits for higher-level analyses relevant to systems and cognitive neuroscience. We demonstrate that GLMsingle: (i) helps decorrelate response estimates between trials nearby in time; (ii) enhances representational similarity between subjects within and across datasets; and (iii) boosts one-versus-many decoding of visual stimuli. GLMsingle is a publicly available tool that can significantly improve the quality of past, present, and future neuroimaging datasets sampling brain activity across many experimental conditions.

A massive 7T fMRI dataset to bridge cognitive neuroscience and artificial intelligence

Extensive sampling of neural activity during rich cognitive phenomena is critical for robust understanding of brain function. Here we present the Natural Scenes Dataset (NSD), in which high-resolution functional magnetic resonance imaging responses to tens of thousands of richly annotated natural scenes were measured while participants performed a continuous recognition task. To optimize data quality, we developed and applied novel estimation and denoising techniques. Simple visual inspections of the NSD data reveal clear representational transformations along the ventral visual pathway. Further exemplifying the inferential power of the dataset, we used NSD to build and train deep neural network models that predict brain activity more accurately than state-of-the-art models from computer vision. NSD also includes substantial resting-state and diffusion data, enabling network neuroscience perspectives to constrain and enhance models of perception and memory. Given its unprecedented scale, quality and breadth, NSD opens new avenues of inquiry in cognitive neuroscience and artificial intelligence.

Benign versus malignant solid breast masses: US differentiation

PURPOSE

To investigate the general applicability and interobserver variability of ultrasonographic (US) features in differentiating benign from malignant solid breast masses.

MATERIALS AND METHODS

One hundred sixty-two consecutive solid masses with a tissue diagnosis were reviewed. Three radiologists reviewed the masses without knowledge of clinical history or histologic examination results.

RESULTS

US features that most reliably characterize masses as benign were a round or oval shape (67 of 71 [94%] were benign), circumscribed margins (95 of 104 [91%] were benign), and a width-to-anteroposterior (AP) dimension ratio greater than 1.4 (82 of 92 [89%] were benign). Features that characterize masses as malignant included irregular shape (19 of 31 [61%] were malignant), microlobulated (four of six [67%] were malignant) or spiculated (two of three [67%] were malignant) margins, and width-to-AP dimension ratio of 1.4 or less (28 of 70 [40%] were malignant). If the three most reliable criteria had been strictly applied by each radiologist, the overall cancer biopsy yield would have increased (from 23% to 39%) by 16%. When US images and mammograms were available, the increase in biopsy yield contributed by US was not statistically significant (2%, P = .73). However, in independent reviews, one to three reviewers interpreted four carcinomas as benign at US.

CONCLUSION

The data confirm that certain US features can help differentiate benign from malignant masses. However, practice and interpreter variability should be further explored before these criteria are generally applied to defer biopsy of solid masses.

Effects of sexual behavioral manipulation on brain plasticity in adult rats

The purpose of the present study was to determine the effects of sexual behaviorial manipulation on brain plasticity in adult male rats. Adult male Sprague-Dawley rats that copulated during male sexual behavior testing were divided into four groups: control male; gonadectomized (Gdx) male; sexually active male; and sexually nonactive male. Female animals were used as an additional control group. At the end of a 12-week experimental period, the animals were again tested for male sexual behavior and tested for sexual motivation. Sexual behavior manipulations over the 12-week period resulted in significant differences in mount latency, mount frequency, intromission latency, intromission frequency, ejaculation latency, and the postejaculation interval. In the motivation test, significant differences in the number of approaches, contacts, and crossings of an electrified grid separating the test animal from a receptive female were also observed. Sexually dimorphic nucleus of the preoptic area (SDN-POA) volumes in sexually nonactive males were significantly smaller than in control males or sexually active males. Anteroventral periventricular nucleus (AVPV) volumes in the male groups were not significantly altered by sexual behavioral manipulations, however, the nonactive AVPV vol. was the only vol. not significantly different from the control female vol. These data demonstrate that in the adult rat, sexual behavioral manipulations resulted in significant alterations in behavior and in the vol. of the SDN-POA and that the effect of sexual behavior on the AVPV needs to be further investigated.

Studies on rapid assessment methods in leprosy

A study was undertaken in Pudukottai district, Tamilnadu, India to test rapid assessment methods: viz (i) sample surveys with lower coverages for clinical examination in estimating the disease problem in the community, (ii) utility of registered case prevalence for estimating the actual prevalence in a given area, (iii) leprosy in school-going children and its utility in estimating leprosy prevalence in the community, and (iv) information on disability and smear positivity in estimating leprosy prevalence; and develop correction factors for estimating leprosy situation. A sample of 23 clusters from 582 clusters of contiguous villages and hamlets was further divided into two random sub-samples for two surveys with differing coverages. One team covered nine clusters comprising 34 villages with a population of 17,562 and examined 15,596 with a population of 26,927 and examined 16,622 (62%) persons for leprosy. The results showed that: (i) leprosy sample surveys with lowered coverages would tend to miss valuable information, in terms of quality and quantity; (ii) from 'known case' registers, to estimate the true burden of leprosy disease and to monitor its trend over time is inadequate; (iii) school surveys are of limited value for estimating the disease burden in the community or to monitor its trend over time; (iv) the number of smear-positive cases is to small to serve as an indicator for the total case load in the community; and (v) the prevalence of active disease and that of grade 2 disability in the community are poorly correlated. Reliable methods other than those used here need to be developed for evaluation and monitoring of the disease burden particularly in the post-MDT era.

Direct connection between myelinosomes, endoplasmic reticulum and nuclear envelope in mouse hepatocytes grown with the amphiphilic drug, quinacrine

Mouse hepatocytes grown in 4 microM quinacrine had numerous myelinosomes which were directly connected to expanded cisternae of the rough endoplasmic reticulum (RER). The cisternae of the RER either subtended the electron transparent space of the myelinosome, expanded to form the outer membrane of the myelinosome or penetrated into it. Material of low electron density was frequently seen within the area where the cisternae penetrated into the electron transparent space of the myelinosome. Myelinosomes were also associated with the nuclear envelope in a pattern similar to that of the RER. Quinacrine appears to bind with the phospholipids of the membranes of the endoplasmic reticulum and nuclear envelope and this drug-lipid complex is then moved into myelinosomes effectively removing the drug from the cell.

Some recent advances in non-communicable diseases in the Tropics. 1. Hypertension: an emerging problem in tropical countries

With increasing urbanization, hypertension and its complications are becoming major health problems in many tropical countries. In particular, hypertension is a major cause of illness in black Africans. There is good evidence that an increasing dietary salt intake is partly responsible for this rising incidence of hypertension and possibly restriction of salt may help in prevention. The public health requirements for the prevention, detection and management of hypertension are likely to consume scarce resources in countries where life expectancy is gradually rising due to improved control of communicable disease and malnutrition. Failure to address the problem of hypertension could have serious effects on morbidity and mortality of economically active individuals in developing countries.

The effect of short-term exposure to low-iron diets on the mucosal processing of ionic iron

Short-term alterations in the amount of iron in the diets of rats caused substantial differences in the distribution of a test dose of radioiron between mucosal transferrin and mucosal ferritin, and also caused a change in the relative amounts of these two proteins in mucosal tissue without resulting in any detectable change in liver iron stores. These differences correlated with changes in the retention of radioiron by the intestinal mucosa and the transport of radioiron to the blood stream. These studies emphasize the importance of local changes in the intestinal mucosa in the regulation of dietary iron absorption.