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Caspases are essential components of the mammalian cell death machinery. Here we test the hypothesis that Caspase 9 (Casp9) is a critical upstream activator of caspases through gene targeting in mice. The majority of Casp9 knockout mice die perinatally with a markedly enlarged and malformed cerebrum caused by reduced apoptosis during brain development.(More)
Human observers combine multiple sensory cues synergistically to achieve greater perceptual sensitivity, but little is known about the underlying neuronal mechanisms. We recorded the activity of neurons in the dorsal medial superior temporal (MSTd) area during a task in which trained monkeys combined visual and vestibular cues near-optimally to discriminate(More)
Recent findings of vestibular responses in part of the visual cortex--the dorsal medial superior temporal area (MSTd)--indicate that vestibular signals might contribute to cortical processes that mediate the perception of self-motion. We tested this hypothesis in monkeys trained to perform a fine heading discrimination task solely on the basis of inertial(More)
Robust perception of self-motion requires integration of visual motion signals with nonvisual cues. Neurons in the dorsal subdivision of the medial superior temporal area (MSTd) may be involved in this sensory integration, because they respond selectively to global patterns of optic flow, as well as translational motion in darkness. Using a virtual-reality(More)
Heading perception is a complex task that generally requires the integration of visual and vestibular cues. This sensory integration is complicated by the fact that these two modalities encode motion in distinct spatial reference frames (visual, eye-centered; vestibular, head-centered). Visual and vestibular heading signals converge in the primate dorsal(More)
Functional links between neuronal activity and perception are studied by examining trial-by-trial correlations (choice probabilities) between neural responses and perceptual decisions. We addressed fundamental issues regarding the nature and origin of choice probabilities by recording from subcortical (brainstem and cerebellar) neurons in rhesus monkeys(More)
Fundamental observations and principles derived from traditional physiological studies of multisensory integration have been difficult to reconcile with computational and psychophysical studies that share the foundation of probabilistic (Bayesian) inference. We review recent work on multisensory integration, focusing on experiments that bridge single-cell(More)
Responses of neurons in early visual cortex change little with training and appear insufficient to account for perceptual learning. Behavioral performance, however, relies on population activity, and the accuracy of a population code is constrained by correlated noise among neurons. We tested whether training changes interneuronal correlations in the dorsal(More)
Recent studies have shown that most neurons in the dorsal medial superior temporal area (MSTd) signal the direction of self-translation (i.e., heading) in response to both optic flow and inertial motion. Much less is currently known about the response properties of MSTd neurons during self-rotation. We have characterized the three-dimensional tuning of MSTd(More)
Humans and monkeys use both vestibular and visual motion (optic flow) cues to discriminate their direction of self-motion during navigation. A striking property of heading perception from optic flow is that discrimination is most precise when subjects judge small variations in heading around straight ahead, whereas thresholds rise precipitously when(More)