Search

In humans, several neuroimaging studies have demonstrated that passive viewing of optic flow stimuli activates higher-level motion areas, like V6 and the cingulate sulcus visual area (CSv). In macaque, there are few studies on the sensitivity of V6 and CSv to egomotion compatible optic flow. The only fMRI study on this issue revealed selectivity to egomotion compatible optic flow in macaque CSv but not in V6 (Cotterau et al. Cereb Cortex 27(1):330–343, 2017, but see Fan et al. J Neurosci. 35:16303–16314, 2015). Yet, it is unknown whether monkey visual motion areas MT + and V6 display any distinctive fMRI functional profile relative to the optic flow stimulation, as it is the case for the homologous human areas (Pitzalis et al., Cereb Cortex 20(2):411–424, 2010). Here, we described the sensitivity of the monkey brain to two motion stimuli (radial rings and flow fields) originally used in humans to functionally map the motion middle temporal area MT + (Tootell et al. J Neurosci 15: 3215-3230, 1995a; Nature 375:139–141, 1995b) and the motion medial parietal area V6 (Pitzalis et al. 2010), respectively. In both animals, we found regions responding only to optic flow or radial rings stimulation, and regions responding to both stimuli. A region in the parieto-occipital sulcus (likely including V6) was one of the most highly selective area for coherently moving fields of dots, further demonstrating the power of this type of stimulation to activate V6 in both humans and monkeys. We did not find any evidence that putative macaque CSv responds to Flow Fields. [ABSTRACT FROM AUTHOR]

Social psychology has long established that the mere presence of a conspecific, be it an active co-performer (coaction effect), or a passive spectator (audience effect) changes behavior in humans. Yet, the process mediating this fundamental social influence has so far eluded us. Brain research and its nonhuman primate animal model, the rhesus macaque, could shed new light on this long debated issue. For this approach to be fruitful, however, we need to improve our patchy knowledge about social presence influence in rhesus macaques. Here, seven adults (two dyads and one triad) performed a simple cognitive task consisting in touching images to obtain food treats, alone vs. in presence of a co-performer or a spectator. As in humans, audience sufficed to enhance performance to the same magnitude as coaction. Effect sizes were however four times larger than those typically reported in humans in similar tasks. Both findings are an encouragement to pursue brain and behavior research in the rhesus macaque to help solve the riddle of social facilitation mechanisms. [ABSTRACT FROM AUTHOR]

The frontostriatal system has been implicated in linking sensory information and action through arbitrary rules. The aim of the present study was to investigate the role of the striatum, a key, integrative structure in such behavior. We recorded single neuronal activity from the anterior striatum of two macaque monkeys as they learned to associate new visual cues with motor responses. Monkeys held a joystick which they could move in one of four constrained directions. During the recording sessions, they were presented with a set of well-learned associations (familiar condition), and with sets of new cues which they were required to map, by trial and error, with joystick movements (novel condition). A sample of 50 striatum neurons were studied during execution of familiar and novel conditions. Activity of most of them was strongly modulated during learning. These modulations were either transient or long lasting changes of neuronal firing rate. The findings suggest that the striatum is involved in early stages of conditional visuomotor learning, and are interpreted in relation with previous data on frontal cortex. [ABSTRACT FROM AUTHOR]

Abstract The role of norepinephrine (NE) in visuo-spatial attention remains poorly understood. Our goal was to identify the attentional processes influenced by atomoxetine (ATX) injections, a NE-reuptake inhibitor that boosts the level of NE in the brain, and to characterize these influences. We tested the effects of ATX injections, on seven monkeys performing a saccadic cued task in which cues and distractors were used to manipulate spatial attention. We found that when the cue accurately predicted the location of the upcoming cue in 80% of the trials, ATX consistently improved attentional orienting, as measured from reaction times (RTs). These effects were best accounted for by a faster accumulation rate in the valid trials, rather than by a change in the decision threshold. By contrast, the effect of ATX on alerting and distractor interference was more inconsistent. Finally, we also found that, under ATX, RTs to non-cued targets were longer when these were presented separately from cued targets. This suggests that the impact of NE on visuo-spatial attention depends on the context, such that the adaptive changes elicited by the highly informative value of the cues in the most frequent trials were accompanied by a cost in the less frequent trials. Highlights • Atomoxetine decreases reaction time of the most prevalent trials. • Atomoxetine modulates the accumulation rate of sensory information. • Atomoxetine adapts the response strategy to the context. [ABSTRACT FROM AUTHOR]

Visuo-spatial attentional orienting is fundamental to selectively process behaviorally relevant information, depending on both low-level visual attributes of stimuli in the environment and higher-level factors, such as goals, expectations and prior knowledge. Growing evidence suggests an impact of the locus-cœruleus-norepinephrine (LC-NE) system in attentional orienting that depends on taskcontext. Nonetheless, most of previous studies used visual displays encompassing a target and various distractors, often preceded by cues to orient the attentional focus. This emphasizes the contribution of goal-driven processes, at the expense of other factors related to the stimulus content. Here, we aimed to determine the impact of NE on attentional orienting in more naturalistic conditions, using complex images and without any explicit task manipulation. We tested the effects of atomoxetine (ATX) injections, a NE reuptake inhibitor, on four monkeys during free viewing of images belonging to three categories: landscapes, monkey faces and scrambled images. Analyses of the gaze exploration patterns revealed, first, that the monkeys spent more time on each fixation under ATX compared to the control condition, regard less of the image content. Second, we found that, depending on the image content, ATX modulated the impact of low-level visual salience on attentional orienting. This effect correlated with the effect of ATX on the number and duration of fixations. Taken together, our results demonstrate that ATX adjusts the contribution of salience on attentional orienting depending on the image content, indicative of its role in balancing the role of stimulus-driven and top-down control during free viewing of complex stimuli. • Atomoxetine increases fixation durations during image exploration. • Atomoxetine modulates the contribution of low-level signaling on spatial orienting. • Atomoxetine adjusts attentional orienting depending on the image content. [ABSTRACT FROM AUTHOR]