The frontal eye field (FEF) is one of several cortical regions thought to modulate sensory inputs. Moreover, hypotheses suggest that the FEF can only early visual areas in presence a stimulus. To test for bottom-up gating signals, we microstimulated subregions two monkeys and measured effects throughout brain with functional magnetic resonance imaging. activity higher-order was strongly modulated by stimulation, independent stimulation. In contrast, stimulation induced topographically...

The macaque visual cortex contains >30 different functional areas, yet surprisingly little is known about the underlying organizational principles that structure its components into a complete “visual” unit. A recent model of cortical organization in humans suggests field maps are organized as clusters. Clusters minimize axonal connections between individual represent common percepts, with clusters thought to carry out functions. Experimental support for this hypothesis, however, lacking...

Spatial attention influences representations in visual cortical areas as well perception. Some models predict a contrast gain, whereas others response or activity gain when is directed to contrast-varying stimulus. Recent evidence has indicated that microstimulating the frontal eye field (FEF) can produce modulations of area V4 neuronal firing rates resemble spatial attention-like effects, and we have shown similar functional magnetic resonance imaging (fMRI) throughout system. Here, used...

We continually shift our attention between items in the visual environment. These shifts are usually based on task relevance (top-down) or saliency of a sudden, unexpected stimulus (bottom-up), and typically followed by goal-directed actions. It could be argued that any species can covertly its focus will rely similar, evolutionarily conserved neural substrates for processing such shift-signals. To address this possibility, we performed comparative fMRI experiments humans monkeys, combining...

A unifying function associated with the default mode network (DMN), which is more active during rest than under task conditions, has been difficult to define. The DMN activated monitoring external world for unexpected events, as a sentinel, and when humans are engaged in high-level internally focused tasks. existence of correlates other species, such mice, challenge idea that focused, cognitive operations, introspection, autobiographical memory retrieval, planning future, predicting someone...

The ventral tegmental area (VTA) is a midbrain structure at the heart of dopaminergic system underlying adaptive behavior. Endogenous firing rates dopamine cells in VTA vary from fast phasic bursts to slow tonic activity. Artificial perturbations VTA, through electrical or optogenetic stimulation methods, generate different and sometimes even contrasting behavioral outcomes depending on parameters such as frequency, amplitude, pulse width. Here, we investigate global functional effects...

Primate area V2 contains a repetitive pattern of thick, thin and pale cytochrome oxidase stripes that are characterized by largely discrete in- output channels, as well differences in function, myelo- cytoarchitecture. Stripes have been identified mainly using microscope-based imaging tiny portions superficially located V2, or postmortem methods, hence, the quest for (quasi) noninvasive tools to study these mesoscale functional units. Only recently, stripe-like patterns demonstrated humans...

Abstract Practice improves perception and enhances neural representations of trained visual stimuli, a phenomenon known as perceptual learning (VPL). While attention to task-relevant stimuli plays an important role in such learning, Pavlovian stimulus-reinforcer associations are sufficient drive VPL, even subconsciously. It has been proposed that reinforcement facilitates through the activation neuromodulatory centers, but this not directly confirmed primates. Here, we paired task-irrelevant...

Abstract The underlying biophysical mechanisms which affect cerebral diffusion contrast remain poorly understood. We hypothesized that metabolism may contrast. purpose of this study was to develop the methodology reversibly deactivate and measure effect on MRI signal. developed an MRI‐compatible cortical cooling system in rhesus monkey area V1 used MR thermometry calculate three‐dimensional temperature maps brain define extent deactivated vivo. Significant changes apparent coefficient (ADC)...

fMRI studies have shown that pairing a task-irrelevant visual feature with electrical micro-stimulation of the ventral tegmental area (VTA-EM) is sufficient to increase sensory cortical representation paired and improve perceptual performance. However, since provides an indirect measure neural activity, response changes underlying activations are unknown. Here, we pair grating orientation VTA-EM while attention directed difficult orthogonal task. We examine in properties macaques by...

Rodent studies have demonstrated the role of mesoaccumbal circuit in reinforcement-based learning. Importantly, however, while phasic activity ventral tegmental area (VTA) contributes to reinforcement learning, rodent evidence suggests that slow changes tonic VTA and associated accumbal dopamine release help regulate motivational behavior. Nonetheless, consequences sustained blockage for motivation learning not yet been examined primates. Using a double-infection viral vector technique, we...

SummaryRetinally-driven activity is modulated by cognitive signals, which originate in higher order brain areas and affect early levels of the visual system via feedback channels. Although oculomotor signals also interact with visually-driven occipital cortex, to stabilize vision enhance saccadic target detection, modulation neuronal non-saccadic somatomotor far less understood, especially primates. We trained monkeys associate color a stimulus either left- or righthand response. After...