Inaccessible time to visual awareness during attentional blinks in macaques and humans.

Even when we attend to successive visual events, we often cannot notice an event occurring during a certain temporal window. Such an inaccessible time for visual awareness is known as "attentional blink" (AB). Whether AB is a phenomenon unique to humans or exists also in other animals is unclear. Using a dual-task paradigm shared between macaques and humans, we here demonstrate a nonhuman primate model of AB. Although macaques also showed behavioral signatures of AB, their AB effect lasted longer than that of humans. To map the relation between macaque and human ABs, we introduced a time warping analysis. The analysis revealed a formal structure behind the interspecies difference of AB; the temporal window of macaque AB was scaled from that of human AB. The present study opens the door to combining the approaches of neuroscience, psychophysics, and theoretical models to further identify a scale-invariant biological substrate of visual awareness.

[The Map of Auditory Function].

Brodmann areas 41 and 42 are located in the superior temporal gyrus and regarded as auditory cortices. The fundamental function in audition is frequency analysis; however, the findings on tonotopy maps of the human auditory cortex were not unified until recently when they were compared to the findings on inputs and outputs of the monkey auditory cortex. The auditory cortex shows plasticity after conditioned learning and surgery of cochlear implant. It is also involved in speech perception, music appreciation, and auditory hallucination in schizophrenia through interactions with other brain areas, such as the thalamus, frontal cortex, and limbic systems.

Cerebral hierarchies: predictive processing, precision and the pulvinar.

This paper considers neuronal architectures from a computational perspective and asks what aspects of neuroanatomy and neurophysiology can be disclosed by the nature of neuronal computations? In particular, we extend current formulations of the brain as an organ of inference--based upon hierarchical predictive coding--and consider how these inferences are orchestrated. In other words, what would the brain require to dynamically coordinate and contextualize its message passing to optimize its computational goals? The answer that emerges rests on the delicate (modulatory) gain control of neuronal populations that select and coordinate (prediction error) signals that ascend cortical hierarchies. This is important because it speaks to a hierarchical anatomy of extrinsic (between region) connections that form two distinct classes, namely a class of driving (first-order) connections that are concerned with encoding the content of neuronal representations and a class of modulatory (second-order) connections that establish context-in the form of the salience or precision ascribed to content. We explore the implications of this distinction from a formal perspective (using simulations of feature-ground segregation) and consider the neurobiological substrates of the ensuing precision-engineered dynamics, with a special focus on the pulvinar and attention.

Responses of pulvinar neurons reflect a subject's confidence in visual categorization.

When we recognize a sensory event, we experience a confident feeling that we certainly know the perceived world 'here and now'. However, it is unknown how and where the brain generates such 'perceptual confidence'. Here we found neural correlates of confidence in the primate pulvinar, a visual thalamic nucleus that has been expanding markedly through evolution. During a categorization task, the majority of pulvinar responses did not correlate with any 'perceptual content'. During an opt-out task, pulvinar responses decreased when monkeys chose 'escape' options, suggesting less confidence in their perceptual categorization. Functional silencing of the pulvinar increased monkeys' escape choices in the opt-out task without affecting categorization performance; this effect was specific to the contralateral visual target. These data were supported by a theoretical model of confidence, indicating that pulvinar activities encode a subject's certainty of visual categorization and contribute to perceptual confidence.

Auditory thalamus integrates visual inputs into behavioral gains.

By binding multisensory signals, we get robust percepts and respond to our surroundings more correctly and quickly. How and where does the brain link cross-modal sensory information to produce such behavioral advantages? The classical role of sensory thalamus is to relay modality-specific information to the cortex. Here we find that, in the rat thalamus, visual cues influence auditory responses, which have two distinct components: an early phasic one followed by a late gradual buildup that peaks before reward. Although both bimodal presentation and reward value had similar effects on behavioral performance, the cross-modal effect on neural activity showed unique temporal dynamics: it affected the amplitude of the early component and starting level of the late component, whereas reward value affected only the slope of the late component. These results demonstrate that cross-modal cueing modulates gain in the sensory thalamus, potentially providing a priming influence on the choice of an optimal behavior.