Smooth-pursuit eye movements are variable, even when the same tracking target motion is repeated many times. We asked whether variation in pursuit could arise from noise in the response of visual motion neurons in the middle temporal visual area (MT). In physiological experiments, we evaluated the mean, variance, and trial-by-trial correlation in the spike counts of pairs of simultaneously recorded MT neurons. The correlations between responses of pairs of MT neurons are highly significant and are stronger when the two neurons in a pair have similar preferred speeds, directions, or receptive field locations. Spike count correlation persists when the same exact stimulus form is repeatedly presented. Spike count correlations increase as the analysis window increases because of correlations in the responses of individual neurons across time. Spike count correlations are highest at speeds below the preferred speeds of the neuron pair and increase as the contrast of a square-wave grating is decreased. In computational analyses, we evaluated whether the correlations and variation across the population response in MT could drive the observed behavioral variation in pursuit direction and speed. We created model population responses that mimicked the mean and variance of MT neural responses as well as the observed structure and amplitude of noise correlations between pairs of neurons. A vector-averaging decoding computation revealed that the observed variation in pursuit could arise from the MT population response, without postulating other sources of motor variation.

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Previous event-related potential (ERP) and brain imaging studies have suggested observer responses to others' pain are modulated by various bottom-up and top-down factors, including emotional primes. However, the temporal dynamics underlying the impact of emotional primes on responses to others' pain remains poorly understood. In the present study, we explored effects of negative, neutral, and positive emotional priming stimuli on behavioral and cortical responses to visual depictions of others in pain. ERPs were recorded from 20 healthy adults, who were presented with painful and non-painful target pictures following observation of negative, neutral, and positive emotional priming pictures. ERP analyses revealed that relative to non-painful pictures, differential P3 amplitudes for painful pictures were larger followed by negative primes than either neutral or positive primes. There were no significant differential P3 amplitudes for painful pictures relative to non-painful pictures were found followed neutral and positive emotional primes. These results suggest that negative emotional primes strengthen observers' attention toward others' pain. These results support the threat value of pain hypothesis.

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Structural evidence suggest that this disruption might be immense (Meyerson et al., Nature 2014, Durr et al., Cell 2014. However, for GluA2, crosslinking mutations, which seem to contradict the hypothesis of desensitization requiring LBD interface opening, have been identified (Yelshanskaya et al., Science 2014). We illustrate how opening the LBD interface using steered molecular dynamics simulations, and analyzing the work values required, provides a quantitative measure for interface stability. We show that for kainate receptors, an iGluR subtype requiring binding of extracellular cations to activate, opening the GluK2 LBD interface without ions bound requires less work than with ions present, suggesting that ion binding stabilizes the interface. Likewise, for interface mutants with longer-lived active states, the interface is more stable, and for less active mutants, the work required to open the interface is reduced. To verify this method for other iGluRs, we show that the work required to open the interface of an inactive GluA2 mutant, L772A, is smaller than for GluA2 WT. Moreover, simulations for GluA2 crosslinked receptors suggest that these mutants can in fact still undergo initial interface opening similar to the GluA2 WT and at no further energetic cost when studied at the LBD dimer level. Thus, we propose that initial interface opening describes the first step of desensitization for both AMPA and kainate receptors.

The complete lower dentition of a new species of the basal anthropoid genus Eosimias shows a combination of primitive and derived traits unknown in other living or fossil primates. Although certain dental traits are decidedly more primitive in Eosimias than in other basal anthropoids, numerous derived aspects of jaw and dental morphology support the anthropoid affinities of Eosimiidae. Eosimiids document an early structural phase in the evolution of higher primates. Phylogenies that derive early anthropoids from cercamoniine adapiforms are inconsistent with eosimiid anatomy. Because early fossil anthropoids are known from both Asia and Africa, the fossil record is presently insufficient to specify the continent on which this clade originated.

Happiness refers to people's cognitive and affective evaluation of their life. Why are some people happier than others? One reason might be that unhappy people are prone to ruminate more than happy people. The default mode network (DMN) is normally active during rest and is implicated in rumination. We hypothesized that unhappiness may be associated with increased default-mode functional connectivity during rest, including the medial prefrontal cortex (MPFC), posterior cingulate cortex (PCC) and inferior parietal lobule (IPL). The hyperconnectivity of these areas may be associated with higher levels of rumination. One hundred forty-eight healthy participants underwent a resting-state fMRI scan. A group-independent component analysis identified the DMNs. Results indicated increased functional connectivity in the DMN was associated with lower levels of happiness. Specifically, relative to happy people, unhappy people exhibited greater functional connectivity in the anterior medial cortex (bilateral MPFC), posterior medial cortex regions (bilateral PCC) and posterior parietal cortex (left IPL). Moreover, the increased functional connectivity of the MPFC, PCC and IPL, correlated positively with the inclination to ruminate. These results highlight the important role of the DMN in the neural correlates of happiness, and suggest that rumination may play an important role in people's perceived happiness.

Visual motion perception relies on two opposing operations: integration and segmentation. Integration overcomes motion ambiguity in the visual image by spatial pooling of motion signals, whereas segmentation identifies differences between adjacent moving objects. For visual motion area MT, previous investigations have reported that stimuli in the receptive field surround, which do not elicit a response when presented alone, can nevertheless modulate responses to stimuli in the receptive field center. The directional tuning of this "surround modulation" has been found to be mainly antagonistic and hence consistent with segmentation. Here, we report that surround modulation in area MT can be either antagonistic or integrative depending upon the visual stimulus. Both types of modulation were delayed relative to response onset. Our results suggest that the dominance of antagonistic modulation in previous MT studies was due to stimulus choice and that segmentation and integration are achieved, in part, via adaptive surround modulation.