Unlocking the symmetric transfer of irrelevant information: gene-environment interplay and enhanced interhemispheric cross-talk.

Hemispheric specialization influences stimulus processing and behavioural control, affecting responses to relevant stimuli. However, most sensory input is irrelevant and must be filtered out to prevent interference with task-relevant behaviour, a process known as habituation. Despite habituation's vital role, little is known about hemispheric specialization for this brain function. We conducted an experiment with domestic chicks, an elite animal model to study lateralization. They were exposed to distracting visual stimuli while feeding when using binocular or monocular vision. Switching the viewing eye after habituation, we examined if habituation was confined to the stimulated hemisphere or shared across hemispheres. We found that both hemispheres learned equally to ignore distracting stimuli. However, embryonic light stimulation, influencing hemispheric specialization, revealed an asymmetry in interhemispheric transfer of the irrelevant information discarded via habituation. Unstimulated chicks exhibited a directional bias, with the right hemisphere failing to transfer distracting stimulus information to the left hemisphere, while transfer from left to right was possible. Nevertheless, embryonic light stimulation counteracted this asymmetry, enhancing communication from the right to the left hemisphere and reducing the pre-existing imbalance. This sharing extends beyond hemisphere-specific functions and encompasses a broader representation of irrelevant events.

Fast-moving features in the debris disk around AU Microscopii.

In the 1980s, excess infrared emission was discovered around main-sequence stars; subsequent direct-imaging observations revealed orbiting disks of cold dust to be the source. These 'debris disks' were thought to be by-products of planet formation because they often exhibited morphological and brightness asymmetries that may result from gravitational perturbation by planets. This was proved to be true for the ß Pictoris system, in which the known planet generates an observable warp in the disk. The nearby, young, unusually active late-type star AU Microscopii hosts a well-studied edge-on debris disk; earlier observations in the visible and near-infrared found asymmetric localized structures in the form of intensity variations along the midplane of the disk beyond a distance of 20 astronomical units. Here we report high-contrast imaging that reveals a series of five large-scale features in the southeast side of the disk, at projected separations of 10-60 astronomical units, persisting over intervals of 1-4 years. All these features appear to move away from the star at projected speeds of 4-10 kilometres per second, suggesting highly eccentric or unbound trajectories if they are associated with physical entities. The origin, localization, morphology and rapid evolution of these features are difficult to reconcile with current theories.

Context learning before birth: evidence from the chick embryo.

Learning contextual information to form associative memories with stimuli of interest is an important brain function in both human and non-human animals. Intuitively, one would expect that such a sophisticated cognitive skill develops postnatally, as the organism starts exploring the surrounding environment to search for significant contingencies among stimuli. Here we show, instead, that even before hatching, domestic chicks are capable of forming associative memories between discrete alerting sounds and the surrounding context, as attested by the fact that habituation of the freezing response to the sounds is affected by the context of stimulation. This finding indicates that, while in the egg, chicks recognize and learn the context in which they are stimulated. Hence, context learning in chicks is an innate brain function already active before birth, which can provide an immediate survival advantage to the newborns of this precocial avian species.

Multiple reward-cue contingencies favor expectancy over uncertainty in shaping the reward-cue attentional salience.

Reward-predicting cues attract attention because of their motivational value. A debated question regards the conditions under which the cue's attentional salience is governed more by reward expectancy rather than by reward uncertainty. To help shedding light on this relevant issue, here, we manipulated expectancy and uncertainty using three levels of reward-cue contingency, so that, for example, a high level of reward expectancy (p = .8) was compared with the highest level of reward uncertainty (p = .5). In Experiment 1, the best reward-cue during conditioning was preferentially attended in a subsequent visual search task. This result was replicated in Experiment 2, in which the cues were matched in terms of response history. In Experiment 3, we implemented a hybrid procedure consisting of two phases: an omission contingency procedure during conditioning, followed by a visual search task as in the previous experiments. Crucially, during both phases, the reward-cues were never task relevant. Results confirmed that, when multiple reward-cue contingencies are explored by a human observer, expectancy is the major factor controlling both the attentional and the oculomotor salience of the reward-cue.

Rapid plasticity attenuation soon after birth revealed by habituation in newborn chicks.

Habituation reflects a form of experience-dependent plasticity whereby the organism progressively learns to ignore the irrelevant information repeatedly encountered. Here, we measured the freezing response to a repeated loud noise in three groups of newborn chicks (Gallus gallus) of different ages (1-2 Day old, 2-3 Day old, and 3-4 Day old) to investigate the ontogeny of habituation in this avian species. Habituation was already present 1 Day after hatching, revealing that the neural mechanisms underlying this form of plasticity are immediately active. Unexpectedly, however, we also found that in the second Day of stimulation the amount of learning was significantly attenuated in chicks of 3-4 days of age as compared to the younger animals, thus showing that 24-48 hr of maturation were sufficient to reduce plasticity. While previous findings in other animal species have proved the existence of a precocious critical period of plasticity in early cortical areas by means of sensory deprivation, our results demonstrate that during the initial development of an intact avian brain also the degree of plasticity underlying a learning process like habituation is maximal soon after birth, and then is subject to a rapid attenuation.

Independent circuits in basal ganglia and cortex for the processing of reward and precision feedback.

In order to understand human decision making it is necessary to understand how the brain uses feedback to guide goal-directed behavior. The ventral striatum (VS) appears to be a key structure in this function, responding strongly to explicit reward feedback. However, recent results have also shown striatal activity following correct task performance even in the absence of feedback. This raises the possibility that, in addition to processing external feedback, the dopamine-centered "reward circuit" might regulate endogenous reinforcement signals, like those triggered by satisfaction in accurate task performance. Here we use functional magnetic resonance imaging (fMRI) to test this idea. Participants completed a simple task that garnered both reward feedback and feedback about the precision of performance. Importantly, the design was such that we could manipulate information about the precision of performance within different levels of reward magnitude. Using parametric modulation and functional connectivity analysis we identified brain regions sensitive to each of these signals. Our results show a double dissociation: frontal and posterior cingulate regions responded to explicit reward but were insensitive to task precision, whereas the dorsal striatum - and putamen in particular - was insensitive to reward but responded strongly to precision feedback in reward-present trials. Both types of feedback activated the VS, and sensitivity in this structure to precision feedback was predicted by personality traits related to approach behavior and reward responsiveness. Our findings shed new light on the role of specific brain regions in integrating different sources of feedback to guide goal-directed behavior.

Short-term and long-term plasticity in the visual-attention system: Evidence from habituation of attentional capture.

Attention is known to be crucial for learning and to regulate activity-dependent brain plasticity. Here we report the opposite scenario, with plasticity affecting the onset-driven automatic deployment of spatial attention. Specifically, we showed that attentional capture is subject to habituation, a fundamental form of plasticity consisting in a response decrement to repeated stimulations. Participants performed a visual discrimination task with focused attention, while being occasionally exposed to a distractor consisting of a high-luminance peripheral onset. With practice, short-term and long-term habituation of attentional capture emerged, making the visual-attention system fully immune to distraction. Furthermore, spontaneous recovery of attentional capture was found when the distractor was temporarily removed. Capture, however, once habituated was surprisingly resistant to spontaneous recovery, taking from several minutes to days to recover. The results suggest that the mechanisms subserving exogenous attentional orienting are subject to profound and enduring plastic changes based on previous experience, and that habituation can impact high-order cognitive functions.

Immediate effect of internal reward on visual adaptation.

In the past decade, there has been an increasing interest in the effects of rewards on visual perception. Exogenous rewards have been shown to increase visual sensitivity and to affect attentional selection. Human beings, however, also feel rewarded by the correct execution of a task. It has been proposed that this form of endogenous reward triggers reinforcement signals in the brain, making the sensory system more sensitive to stimuli that have been extensively and repeatedly paired with the rewarding experiences and modulating long-term cortical plasticity. Here, we report the striking observation that a well-known visual illusion, the tilt aftereffect, which is due to a form of short-term cortical plasticity, is immediately enhanced by a concurrent and independent target-recognition process. Our results show that endogenous rewards can alter visual experience with virtually no delay.

Unconscious priming instructions modulate activity in default and executive networks of the human brain.

During task executions, brain activity increases in executive networks (ENs) and decreases in default-mode networks (DMNs). Here, we examined whether these large-scale network dynamics can be influenced by unconscious cognitive information processing. Volunteers saw instructions (cues) to respond either ipsilaterally or contralaterally to a subsequent lateralized target. Unbeknownst to them, each cue was preceded by a masked stimulus (prime), which could be identical (congruent), or opposite (incongruent) to the cue, or neutral (not an instruction). Behaviorally, incongruent primes interfered with performance, even though they were not consciously perceived. With functional magnetic resonance imaging, we individuated the anticorrelated ENs and DMNs involved during task execution. With effective connectivity analyses, we found that DMNs caused activity in ENs throughout the task. Unconscious interference during incongruent trials was associated with a specific activity increase in ENs and an activity drop in DMNs. Intersubject efficiency in performance during incongruent trials was correlated with functional connectivity between specific ENs and DMNs. These results indicate that unconscious instructions can prime activity in ENs and DMNs and suggest that the DMNs play a key role in unconscious monitoring of the environment in the service of efficient resource allocation for task execution.

Habituation (of attentional capture) is not what you think it is.

Habituation represents a well-established form of learning in various neuroscience domains. However, cognitive psychologists working in the field of visual attention have largely overlooked this phenomenon. In this regard, I would like to argue that the reduction in attentional capture observed with repetitive salient distractors, and specifically abrupt visual onsets, could be attributed to habituation. Three classic models of habituation, independently devised by Sokolov, Wagner, and by Thompson, will be presented and discussed in relation to the capture of attention. Of particular interest is the fact that Sokolov's model is governed by a prediction-error minimization principle, where a stimulus attracts attention to the extent that it violates the expected sensory input, which is anticipated on the basis of the previous history of stimulation. Hence, at least in humans, habituation is governed by high-order cognitive processes, and should not be confounded with peripheral sensory adaptation or fatigue. Furthermore, the cognitive nature of habituation is also attested by the fact that visual distractor filtering is context-specific. In conclusion, as already suggested by others, I believe that researchers working in the field of attention should give more consideration to the notion of habituation, especially with regard to the control of stimulus-driven capture. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Habituation to abrupt-onset distractors with different spatial occurrence probability.

Previous studies have shown that abrupt onsets randomly appearing at different locations can be ignored with practice, a result that was interpreted as an instance of habituation. Here we addressed whether habituation of capture can be spatially selective and determined by the rate of onset occurrence at different locations, and whether habituation is achieved via spatial suppression applied at the distractor location. In agreement with the habituation hypothesis, we found that capture attenuation was larger where the onset distractor occurred more frequently, similarly to what has been documented for feature-singleton distractors (the "distractor-location effect"), and that onset interference decreased across trials at both the high- and low-probability distractor locations. By contrast, evidence was inconclusive as to whether distractor filtering was also accompanied by a larger impairment in target processing when it appeared at the more likely distractor location (the "target-location effect"), as instead previously reported for feature-singleton distractors. Finally, here we discuss how and to what extent distractor rejection based on statistical learning and habituation of capture are different, and conclude that the two notions are intimately related, as the Sokolov model of habituation operates by comparing the upcoming sensory input with expectation based on the statistics of previous stimulation.

Habituation to onsets is controlled by spatially selective distractor expectation.

Habituation to onset distractors has been shown to be stronger the higher the distractor probability. However, since in previous studies distractor probability covaried with distractor numerosity, it was unclear whether habituation was controlled by a mechanism that relies on distractor expectation (Sokolov, 1963), or by a mechanism that is merely driven by the number of stimulations delivered to the nervous system (Groves & Thompson, 1970). To address this issue, we manipulated the probability of distractor occurrence at a fixed location, without varying the number of distractors being presented. The results of Experiment 1 clearly favored the Sokolov model of habituation, showing that habituation of capture is controlled by the level of distractor expectation for the same distractors number. Experiment 2 excluded that the pattern of habituation was determined by the difference in the temporal frequency of the distractor between higher and lower distractor rates. Furthermore, the results of Experiment 3 suggested that the amount of habituation of capture is mainly controlled by the local rather than by the global rate of the onset distractor occurrence, thus indicating that habituation of capture is largely spatially specific. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Ignoring visual distractors: Habituation to onsets is driven by time-based expectation.

An increasing bulk of evidence shows that through different mechanisms, experienced-based or voluntary, reactive or proactive, human beings can attenuate the distracting impact of salient visual, albeit irrelevant, stimuli. Current mechanisms assume that this is achieved by suppressing the salient distractor's features or location at the priority map level, or at lower dimension-based maps levels. However, this functional architecture has so far ignored the role of time in distractors filtering, a key question that we have addressed in the present study. We found that during a visual discrimination task, a "standard" onset distractor, always appearing at the same interval from the beginning of the trial, was subject to habituation. Crucially, however, when the onset distractor was unfrequently presented with an unexpected 1-second delay, it reboosted capture at full strength, while the "standard" distractor continued to remain overall habituated. As predicted by Sokolov's (1963, Annual Review of Physiology, 25[1], 545-580) theory, our results show that habituation mechanisms filter the irrelevant distracting sensory input also on the basis of its temporal parameters. We conclude that habituation to onsets is controlled also by time-based expectation mechanisms and suggest that more recently proposed theories of distractors filtering should also incorporate the temporal parameter among the factors that allow an efficient handling of visual distraction.

Habituation to visual onsets is affected by local and global distractors rate.

Recent findings demonstrate that habituation of capture is stronger where onset distractors are frequent and weaker where they are rare, thus showing that habituation to onsets has a spatial selective nature. However, a debated question is whether habituation at a specific location is exclusively determined by the distractors' local rate, or whether instead local habituation is also affected by the global rate of the distractors, which may occur also at other locations. Here, we report the results from a between-participants experiment involving three groups of participants exposed to visual onsets during a visual search task. In two groups, onsets appeared at a single location with a high 60% rate or a low 15% rate, respectively, whereas in a third group, distractors could appear in four distinct locations with the same 15% local rate, leading to a 60% global rate. Our results confirmed that locally, habituation of capture was stronger the higher the distractors rate. However, the key finding was that we found a clear and robust modulation of the global distractors rate on the local habituation level. Taken together, our results unambiguously show that habituation has both a spatially selective and a spatially nonselective nature.

Permeability of priming of pop out to expectations.

It is well established that repetition of the same target color across consecutive trials enhances search efficiency for pop-out targets; this phenomenon is known as Priming of Pop out (PoP). In three experiments, we addressed whether PoP interacts with top-down expectations in altering target visibility, which was manipulated via metacontrast masking. The target color either remained the same for n consecutive trials (blocked condition) or changed unpredictably (random condition). The results showed that PoP reduced the efficacy of masking and that its beneficial effect can be either potentiated or attenuated by participants' expectations about the upcoming target color. These findings undermine the view that PoP should be impermeable to top-down factors. In addition, we found evidence that both explicit and implicit expectations interact with PoP. The former can be induced via instructions on the rate of alternation of the target color, and the latter can be induced by random sequences in which repetitions of the same target color exceed those predicted by an internal model of randomness for binary events. In the latter case, more than three repetitions of the same target color led to a decline in target visibility. We speculate that, in the random condition, after few repetitions of the same target, participants developed an expectation for a change; this phenomenon is similar to the "gambler's fallacy." Finally, our analyses revealed no effect of expectation on switch trials (i.e., when the target color changed), which casts doubt on the efficacy of top-down control in feature search.

Impaired selection of a previously ignored singleton: Evidence for salience map plastic changes.

Spatial suppression of a salient colour distractor is achievable via statistical learning. Distractor suppression attenuates unwanted capture, but at the same time target selection at the most likely distractor location is impaired. This result corroborates the idea that the distractor salience is attenuated via inhibitory signals applied to the corresponding location in the priority map. What is less clear, however, is whether lingering impairment in target selection when the distractor is removed are due to the proactive strategic maintenance of the suppressive signal at the previous most likely distractor location or result from the fact that suppression has induced plastic changes in the priority map, probably changing input weights. Here, we provide evidence that supports the latter possibility, as we found that impairment in target selection persisted even when the singleton distractor in the training phase became the target of search in a subsequent test phase. This manipulation rules out the possibility that the observed impairments at the previous most likely distractor location were caused by a signal suppression maintained at this location. Rather, the results reveal that the inhibitory signals cause long-lasting changes in the priority map, which affect future computation of the target salience at the same location, and therefore the efficiency of attentional selection.

Testing reward-cue attentional salience: Attainment and dynamic changes.

A great wealth of studies has investigated the capacity of motivationally relevant stimuli to bias attention, suggesting that reward predicting cues are prioritized even when reward is no longer delivered and when attending to such stimuli is detrimental to reward achievement. Despite multiple procedures have been adopted to unveil the mechanisms whereby reward cues gain attentional salience, some open questions remain. Indeed, mechanisms different from motivation can be responsible for the capture of attention triggered by the reward cue. In addition, we note that at present only a few studies have sought to address whether the cue attractiveness dynamically follows changes in the associated reward value. Investigating how and to what extent the salience of the reward cue is updated when motivation changes, could help shedding light on how reward-cues attain and maintain their capacity to attract attention, and therefore on apparent irrational attentive behaviors.

Cooperative and opposing effects of strategic and involuntary attention.

To assess whether working memory contents can effectively bias visual selection even when they do not represent the current target in the attention task, we recorded the ERP activity from participants performing both a memory task and, in the retention period, a visual search task. In this task, a distracter matching the memory content could be presented on the same side (congruent trials) or on the opposite side (incongruent trials) relative to the target location (Experiment 1 and Experiment 2). On some trials, only the matching distracter (but no target) was presented (catch trials, Experiment 2). Results showed that the N2pc component was modulated by the presence and location of a matching distracter. We interpret these results as evidence that the involuntary control exerted by the irrelevant memory contents coexists with the strategic mechanism related to the search target, influencing attention selection with roughly equal power. In Experiment 3, we found that the modulation of the N2pc is not strictly related to the active maintenance of the memory-target features but can also be elicited by repetition priming. Overall, these findings suggest that, together with the physical properties of the stimuli presented in the visual field, irrelevant memory contents represent a powerful class of factors that lead to involuntary attentional control.

Distractor filtering is affected by local and global distractor probability, emerges very rapidly but is resistant to extinction.

Effects of statistical learning (SL) of distractor location have been shown to persist when the probabilities of distractor occurrence are equalized across different locations in a so-called extinction phase. Here, we asked whether lingering effects of SL are still observed when a true extinction phase, during which the distractor is completely omitted, is implemented. The results showed that, once established, the effects of SL of distractor location do survive the true extinction phase, indicating that the pattern of suppression in the saliency map is encoded in a form of long-lasting memory. Quite unexpectedly, we also found that the amount of filtering implemented at a given location is not only dictated by the specific rate of distractor occurrence at that location, as previously found, but also by the global distractor probability. We therefore suggest that the visual attention system could be more or less (implicitly) prone to suppression as a function of how often the distractor is encountered overall, and that this suppressive bias affects the degree of suppression at the specific distractor-probability location. Finally, our results showed that the effects of SL of distractor location can appear much more rapidly than has been previously documented, requiring a few trials to become manifest. Hence, SL of distractor location appears to have an asymmetrical rate of learning during acquisition and extinction, while the amount of suppression exerted at a specific distractor location is modulated by distractor contextual probabilistic information.