The Distinct Role of the Amygdala, Superior Colliculus and Pulvinar in Processing of Central and Peripheral Snakes

Heterogeneity in Category Recognition across the Visual Field

Visual information emerging from the extrafoveal locations is important for visual search, saccadic eye movement control, and spatial attention allocation. Our everyday sensory experience with visual object categories varies across different parts of the visual field which may result in location-contingent variations in visual object recognition. We used a body, animal body, and chair two-forced choice object category recognition task to investigate this possibility. Animal body and chair images with various levels of visual ambiguity were presented at the fovea and different extrafoveal locations across the vertical and horizontal meridians. We found heterogeneous body and chair category recognition across the visual field. Specifically, while the recognition performance of the body and chair presented at the fovea were similar, it varied across different extrafoveal locations. The largest difference was observed when the body and chair images were presented at the lower-left and upper-right visual fields, respectively. The lower/upper visual field bias of the body/chair recognition was particularly observed in low/high stimulus visual signals. Finally, when subjects' performances were adjusted for a potential location-contingent decision bias in category recognition by subtracting the category detection in full noise condition, location-dependent category recognition was observed only for the body category. These results suggest heterogeneous body recognition bias across the visual field potentially due to more frequent exposure of the lower visual field to body stimuli.

Hooding cobras can get ahead of other snakes in the ability to evoke human fear

Fear of snakes is common not only in humans but also in other primates. Consequently, snakes are salient stimuli associated with prioritized attention, early detection and emotional significance. This has been interpreted as an adaptive evolutionary response of the primate brain to a risk of envenoming by a hidden snake. However, the struggle between mammals and snakes is not one-sided. Humans and carnivores regularly kill snakes, and thus snakes develop deterring defensive behaviour that may directly evoke enhanced fear. Here, we show that snakes depicted in threatening posture evoked on average more fear than those in resting posture. Significantly, African (Somali) and European (Czech) respondents considerably agreed on the relative fear elicited by various snakes. Nonetheless, not all defensive postures are equally efficient. Threatening cobras were perceived as top fear-evoking stimuli, even though most of them are not considered very frightening in resting posture. This effect can be attributed to their conspicuous hooding posture which evolved into an efficient warning signal for mammalian predators. Our result demonstrates that cobras are more effective than other snakes in the ability to evoke human fear by a simple behavioural display-hooding. This can be primarily explained by the behavioural evolution of cobras which successfully exploited pre-existing cognitive mechanisms of mammals. Whether human ancestors cohabiting with deadly venomous cobras further improved their fear response to hooding is uncertain, but likely.

Rapid integration of face detection and task set in visually guided reaching

The superior colliculus (SC) has been increasingly implicated in the rapid processing of evolutionarily relevant stimuli like faces, but the behavioural relevance of such processing is unclear. The SC has also been implicated in the generation of express visuomotor responses (EVR), which are very short-latency (~80 ms) bursts of muscle activity time-locked to visual target presentation. These observations led us to investigate the influence of faces on EVRs. We recorded upper limb muscle activity from healthy participants as they reached toward targets in the presence of a distractor. In some experiments, faces were used as stimuli. Across blocks of trials, we varied the instruction as to which stimulus served as the target or distractor. Doing so allowed us to assess the impact of instruction on muscle recruitment given identical visual stimuli. We found that responses were uniquely modulated in tasks involving high-contrast faces, promoting reaches toward or away from a face depending on instruction. Follow-up experiments confirmed that the phenomenon required highly salient repeated faces and was not observed to non-facial stimuli nor to faces expressing different affects. This study extends the hypothesis that the SC mediates the EVR by demonstrating that faces impact muscle recruitment at short latencies that precede cortical activity for face perception. Our results constitute direct evidence for the behavioural relevance of face detection in the brainstem, and also implicate a role for top-down cortical pre-setting of the EVR depending on task context.

Macaque claustrum, pulvinar and putative dorsolateral amygdala support the cross-modal association of social audio-visual stimuli based on meaning

Social communication draws on several cognitive functions such as perception, emotion recognition and attention. The association of audio-visual information is essential to the processing of species-specific communication signals. In this study, we use functional magnetic resonance imaging in order to identify the subcortical areas involved in the cross-modal association of visual and auditory information based on their common social meaning. We identified three subcortical regions involved in audio-visual processing of species-specific communicative signals: the dorsolateral amygdala, the claustrum and the pulvinar. These regions responded to visual, auditory congruent and audio-visual stimulations. However, none of them was significantly activated when the auditory stimuli were semantically incongruent with the visual context, thus showing an influence of visual context on auditory processing. For example, positive vocalization (coos) activated the three subcortical regions when presented in the context of positive facial expression (lipsmacks) but not when presented in the context of negative facial expression (aggressive faces). In addition, the medial pulvinar and the amygdala presented multisensory integration such that audiovisual stimuli resulted in activations that were significantly higher than those observed for the highest unimodal response. Last, the pulvinar responded in a task-dependent manner, along a specific spatial sensory gradient. We propose that the dorsolateral amygdala, the claustrum and the pulvinar belong to a multisensory network that modulates the perception of visual socioemotional information and vocalizations as a function of the relevance of the stimuli in the social context. SIGNIFICANCE STATEMENT: Understanding and correctly associating socioemotional information across sensory modalities, such that happy faces predict laughter and escape scenes predict screams, is essential when living in complex social groups. With the use of functional magnetic imaging in the awake macaque, we identify three subcortical structures-dorsolateral amygdala, claustrum and pulvinar-that only respond to auditory information that matches the ongoing visual socioemotional context, such as hearing positively valenced coo calls and seeing positively valenced mutual grooming monkeys. We additionally describe task-dependent activations in the pulvinar, organizing along a specific spatial sensory gradient, supporting its role as a network regulator.

Pathways for Naturalistic Looking Behavior in Primate II. Superior Colliculus Integrates Parallel Top-down and Bottom-up Inputs

Volitional signals for gaze control are provided by multiple parallel pathways converging on the midbrain superior colliculus (SC), whose deeper layers output to the brainstem gaze circuits. In the first of two papers (Takahashi and Veale, 2023), we described the properties of gaze behavior of several species under both laboratory and natural conditions, as well as the current understanding of the brainstem and spinal cord circuits implementing gaze control in primate. In this paper, we review the parallel pathways by which sensory and task information reaches SC and how these sensory and task signals interact within SC's multilayered structure. This includes both bottom-up (world statistics) signals mediated by sensory cortex, association cortex, and subcortical structures, as well as top-down (goal and task) influences which arrive via either direct excitatory pathways from cerebral cortex, or via indirect basal ganglia relays resulting in inhibition or dis-inhibition as appropriate for alternative behaviors. Models of attention such as saliency maps serve as convenient frameworks to organize our understanding of both the separate computations of each neural pathway, as well as the interaction between the multiple parallel pathways influencing gaze. While the spatial interactions between gaze's neural pathways are relatively well understood, the temporal interactions between and within pathways will be an important area of future study, requiring both improved technical methods for measurement and improvement of our understanding of how temporal dynamics results in the observed spatiotemporal allocation of gaze.

Can the processing of task-irrelevant threatening stimuli be inhibited? - The role of shape and valence in the saliency of threatening objects

Numerous studies have demonstrated that attention is quickly oriented towards threatening stimuli, and that this attentional bias is difficult to inhibit. The root cause(s) of this bias may be attributable to the affective (e.g., valence) or visual features (e.g., shape) of threats. In two experiments (behavioral, eye-tracking), we tested which features play a bigger role in the salience of threats. In both experiments, participants looked for a neutral target (butterfly, lock) among other neutral objects. In half of the trials a threatening (snake, gun) or nonthreatening (but visually similar; worm, hairdryer) task-irrelevant distractor was also present at a near or far distance from the target. Behavioral results indicate that both distractor types interfered with task performance. Rejecting nonthreatening distractors as nontargets was easier when they were presented further from the target but distance had no effect when the distractor was threatening. Eye-tracking results showed that participants fixated less often (and for less time) on threatening compared to nonthreatening distractors. They also viewed targets for less time when a threatening distractor was present (compared to nonthreatening). Results suggest that visual features of threats are easier to suppress than affective features, and the latter may have a stronger role in eliciting attentional biases.

Are vipers prototypic fear-evoking snakes? A cross-cultural comparison of Somalis and Czechs

Snakes are known as highly fear-evoking animals, eliciting preferential attention and fast detection in humans. We examined the human fear response to snakes in the context of both current and evolutionary experiences, conducting our research in the cradle of humankind, the Horn of Africa. This region is characterized by the frequent occurrence of various snake species, including deadly venomous viperids (adders) and elapids (cobras and mambas). We conducted experiments in Somaliland and compared the results with data from Czech respondents to address the still unresolved questions: To which extent is human fear of snakes affected by evolutionary or current experience and local culture? Can people of both nationalities recognize venomous snakes as a category, or are they only afraid of certain species that are most dangerous in a given area? Are respondents of both nationalities equally afraid of deadly snakes from both families (Viperidae, Elapidae)? We employed a well-established picture-sorting approach, consisting of 48 snake species belonging to four distinct groups. Our results revealed significant agreement among Somali as well as Czech respondents. We found a highly significant effect of the stimulus on perceived fear in both populations. Vipers appeared to be the most salient stimuli in both populations, as they occupied the highest positions according to the reported level of subjectively perceived fear. The position of vipers strongly contrasts with the fear ranking of deadly venomous elapids, which were in lower positions. Fear scores of vipers were significantly higher in both populations, and their best predictor was the body width of the snake. The evolutionary, cultural, and cognitive aspects of this phenomenon are discussed.

Dopamine modulates visual threat processing in the superior colliculus via D2 receptors

Innate defensive responses, unlearned behaviors improving individuals’ chances of survival, have been found to involve the dopamine (DA) system. In the superior colliculus (SC), known for its role in defensive behaviors to visual threats, neurons expressing dopaminergic receptors of type 1 (Drd1+) and of type 2 (Drd2+) have been identified. We hypothesized that SC neurons expressing dopaminergic receptors may play a role in promoting innate defensive responses. Optogenetic activation of SC Drd2+ neurons, but not Drd1+ neurons, triggered defensive behaviors. Chemogenetic inhibition of SC Drd2+ neurons decreased looming-induced defensive behaviors, as well as pretreatment with the pharmacological Drd2+ agonist quinpirole, suggesting an essential role of Drd2 receptors in the regulation of innate defensive behavior. Input and output viral tracing revealed SC Drd2+ neurons mainly receive moderate inputs from the locus coeruleus (LC). Our results suggest a sophisticated regulatory role of DA and its receptor system in innate defensive behavior.

•

Optogenetic activation of SC Drd2 + neurons, but not Drd1 + , induces defensive behaviors

•

Repeated activation of SC Drd2 + provokes aversive memory and depression-like behavior

•

Chemogenetic and pharmacological inhibition of SC Drd2 + impaired defensive behaviors

•

Monosynaptic tracing revealed SC Drd2 + neurons mainly receive TH + projections from LC

The effects of task-irrelevant threatening stimuli on orienting- and executive attentional processes under cognitive load

Human visual attention is biased to rapidly detect threats in the environment so that our nervous system can initiate quick reactions. The processes underlying threat detection (and how they operate under cognitive load), however, are still poorly understood. Thus, we sought to test the impact of task-irrelevant threatening stimuli on the salience network and executive control of attention during low and high cognitive load. Participants were exposed to neutral or threatening pictures (with moderate and high arousal levels) as task-irrelevant distractors in near (parafoveal) and far (peripheral) positions while searching for numbers in ascending order in a matrix array. We measured reaction times and recorded eye-movements. Our results showed that task-irrelevant distractors primarily influenced behavioural measures during high cognitive load. The distracting effect of threatening images with moderate arousal level slowed reaction times for finding the first number. However, this slowing was offset by high arousal threatening stimuli, leading to overall shorter search times. Eye-tracking measures showed that participants fixated threatening pictures more later and for shorter durations compared to neutral images. Together, our results indicate a complex relationship between threats and attention that results not in a unitary bias but in a sequence of effects that unfold over time.

Fast Detection of Snakes and Emotional Faces in the Macaque Amygdala

Primate vision is reported to detect snakes and emotional faces faster than many other tested stimuli. Because the amygdala has been implicated in avoidance and emotional behaviors to biologically relevant stimuli and has neural connections with subcortical nuclei involved with vision, amygdalar neurons would be sensitive to snakes and emotional faces. In this study, neuronal activity in the amygdala was recorded from Japanese macaques (Macaca fuscata) during discrimination of eight categories of visual stimuli including snakes, monkey faces, human faces, carnivores, raptors, non-predators, monkey hands, and simple figures. Of 527 amygdalar neurons, 95 responded to one or more stimuli. Response characteristics of the amygdalar neurons indicated that they were more sensitive to the snakes and emotional faces than other stimuli. Response magnitudes and latencies of amygdalar neurons to snakes and monkey faces were stronger and faster than those to the other categories of stimuli, respectively. Furthermore, response magnitudes to the low pass-filtered snake images were larger than those to scrambled snake images. Finally, analyses of population activity of amygdalar neurons suggest that snakes and emotional faces were represented separately from the other stimuli during the 50–100 ms period from stimulus onset, and neutral faces during the 100–150 ms period. These response characteristics indicate that the amygdala processes fast and coarse visual information from emotional faces and snakes (but not other predators of primates) among the eight categories of the visual stimuli, and suggest that, like anthropoid primate visual systems, the amygdala has been shaped over evolutionary time to detect appearance of potentially threatening stimuli including both emotional faces and snakes, the first of the modern predators of primates.

The Hypothesis of Subliminal Cue Reactivity in Addiction Revisited: An fMRI Study

INTRODUCTION

Exposure to conditioned cues is a common trigger of relapse in addiction. It has been suggested that such cues can activate motivationally relevant neurocircuitry in individuals with substance use disorders even without being consciously perceived. We aimed to see if this could be replicated in a sample with severe amphetamine use disorder and a control group of healthy subjects.

METHODS

We used fMRI to test the hypothesis that individuals with amphetamine use disorder, but not healthy controls, exhibit a specific neural reactivity to subliminally presented pictures related to amphetamine use. Twenty-four amphetamine users and 25 healthy controls were recruited and left data of sufficient quality to be included in the final analysis. All subjects were exposed to drug-related and neutral pictures of short duration (13.3 ms), followed by a backward visual mask image. The contrast of interest was drug versus neutral subliminal pictures.

RESULTS

There were no statistically significant differences in BOLD signal between the drug and neutral cues, neither in the limbic regions of primary interest nor in exploratory whole-brain analyses. The same results were found both in amphetamine users and controls.

DISCUSSION/CONCLUSION

We found no evidence of neural reactivity to subliminally presented drug cues in this sample of subjects with severe amphetamine dependence. These results are discussed in relation to the earlier literature, and the evidence for subliminal drug cue reactivity in substance use disorders is questioned.

The Saliency of Snake Scales and Leopard Rosettes to Infants: Its Relevance to Graphical Patterns Portrayed in Prehistoric Art

Geometrically arranged spots and crosshatched incised lines are frequently portrayed in prehistoric cave and mobiliary art. Two experiments examined the saliency of snake scales and leopard rosettes to infants that are perceptually analogous to these patterns. Experiment 1 examined the investigative behavior of 23 infants at three daycare facilities. Four plastic jars (15×14.5cm) with snake scales, leopard rosettes, geometric plaid, and plain patterns printed on yellowish-orange paper inside were placed individually on the floor on separate days during playtime. Fourteen 7–15-month-old infants approached each jar hesitantly and poked it before handling it for five times, the criterion selected for statistical analyses of poking frequency. The jars with snake scales and leopard rosettes yielded reliably higher poking frequencies than the geometric plaid and plain jars. The second experiment examined the gaze and grasping behavior of 15 infants (spanning 5months of age) seated on the laps of their mothers in front of a table. For paired comparisons, the experimenter pushed two of four upright plastic cylinders (13.5×5.5cm) with virtually the same colored patterns simultaneously toward each infant for 6s. Video recordings indicated that infants gazed significantly longer at the cylinders with snake scales and leopard rosettes than the geometric plaid and plain cylinders prior to grasping them. Logistic regression of gaze duration predicting cylinder choice for grasping indicated that seven of 24 paired comparisons were not significant, all of which involved choices of cylinders with snake scales and leopard rosettes that diverted attention before reaching. Evidence that these biological patterns are salient to infants during an early period of brain development might characterize the integration of subcortical and neocortical visual processes known to be involved in snake recognition. In older individuals, memorable encounters with snakes and leopards coupled with the saliency of snake scales and leopard rosettes possibly biased artistic renditions of similar patterns during prehistoric times.

Reliability of DNMSQuest as a Screening Tool for Mood Disorders in Cervical Dystonia

Background

The high prevalence of mood disorders in cervical dystonia, often unaddressed in botulinum toxin clinics, is a major factor in impaired quality of life. There is a clear need for a brief screening method for identifying these disorders; the Dystonia non-motor symptoms questionnaire (DNMSQuest) has been proposed as such.

Objective

We aimed to assess the practical utility of the DNMSQuest and compare it with validated rating scales for anxiety, depression and quality of life.

Methods

In 88 patients with cervical dystonia, we compared results from the DNMSQuest with mood rating scales [Beck Anxiety Inventory (BAI), Beck Depression Index (BDI-II) and Hospital Anxiety and Depression Scale (HADS)], quality of life measures [European Quality of Life (EQOL) and European Quality of Life Visual Analogue Scale (EQOLVAS)] and with assessments of dystonia severity [Cervical Dystonia Impact Profile-58 (CDIP58) and Toronto Western Rating Scale for Spasmodic Torticollis (TWSTRS)].

Results

Using a cut off score on the DNMSQuest of 5, we noted that DNMSQuest had a sensitivity of 85% for detecting anxiety and depression using the BAI and BDI-II, and 76% and 78% for anxiety and depression respectively using the HADS. The DNMSQuest correlated strongly with BAI (ρ = 0.715), BDI-II (ρ = 0.658), HADS-Anxiety (ρ = 0.616), HADS-Depression (ρ = 0.706), EQOL (ρ = 0.653) and CDIP-58 (ρ = 0.665).

Conclusion

The DNMSQuest is a brief, sensitive and non-specific instrument for identifying patients that warrant further review for anxiety and depression and can easily be implemented in a neurologist-run botulinum toxin clinic.

Super-natural fears

Supernatural fears, although common, are not as well-understood as natural fears and phobias (e.g., social, blood, and animal phobias) which are prepared by evolution, such that they are easily acquired through direct experience and relatively immune to cognitive mediation. In contrast, supernatural fears do not involve direct experience but seem to be related to sensory or cognitive biases in the interpretation of stimuli as well as culturally driven cognitions and beliefs. In this multidisciplinary synthesis and collaborative review, we claim that supernatural beliefs are "super natural." That is, they occur spontaneously and are easy to acquire, possibly because such beliefs rest on intuitive concepts such as mind-body dualism and animism, and may inspire fear in believers as well as non-believers. As suggested by psychological and neuroscientific evidence, they tap into an evolutionarily prepared fear of potential impending dangers or unknown objects and have their roots in "prepared fears" as well as "cognitively prepared beliefs," making fear of supernatural agents a fruitful research avenue for social, anthropological, and psychological inquires.

Right Hemisphere Dominance for Unconscious Emotionally Salient Stimuli

The present review will focus on evidence demonstrating the prioritization in visual processing of fear-related signals in the absence of awareness. Evidence in hemianopic patients without any form of blindsight or affective blindsight in classical terms will be presented, demonstrating that fearful faces, via a subcortical colliculo-pulvinar-amygdala pathway, have a privileged unconscious visual processing and facilitate responses towards visual stimuli in the intact visual field. Interestingly, this fear-specific implicit visual processing in hemianopics has only been observed after lesions to the visual cortices in the left hemisphere, while no effect was found in patients with damage to the right hemisphere. This suggests that the subcortical route for emotional processing in the right hemisphere might provide a pivotal contribution to the implicit processing of fear, in line with evidence showing enhanced right amygdala activity and increased connectivity in the right colliculo-pulvinar-amygdala pathway for unconscious fear-conditioned stimuli and subliminal fearful faces. These findings will be discussed within a theoretical framework that considers the amygdala as an integral component of a constant and continuous vigilance system, which is preferentially invoked with stimuli signaling ambiguous environmental situations of biological relevance, such as fearful faces.

Hunters and Gatherers of Pictures: Why Photography Has Become a Human Universal

Photography is ubiquitous worldwide. We analyzed why people take, share, and use personal photographs, independent of their specific cultural background. These behaviors are still poorly understood. Experimental research on them is scarce. Smartphone technology and social media have pushed the success of photography, but cannot explain it, as not all smartphone features are widely used just because they are available. We analyzed properties of human nature that have made taking and using photographs functional behaviors. We did this based on the four levels, which Nikolaas Tinbergen suggested for analyzing why animals behave in a particular way. Including findings from multiple disciplines, we developed a novel conceptual framework-the "Mental Utilization Hypothesis of Photography." It suggests that people adopt photography because it matches with core human mental mechanisms mainly from the social domain, and people use photography as a cognitive, primarily social coping strategy. Our framework comprises a range of testable predictions, provides a new theoretical basis for future empirical investigations into photography, and has practical implications. We conclude that photography has become a human universal, which is based on context-sensitive mental predispositions and differentiates itself in the social and societal environment.

The Amygdala Responds Rapidly to Flashes Linked to Direct Retinal Innervation: A Flash-evoked Potential Study Across Cortical and Subcortical Visual Pathways

Rapid detection and response to visual threats are critical for survival in animals. The amygdala (AMY) is hypothesized to be involved in this process, but how it interacts with the visual system to do this remains unclear. By recording flash-evoked potentials simultaneously from the superior colliculus (SC), lateral posterior nucleus of the thalamus, AMY, lateral geniculate nucleus (LGN) and visual cortex, which belong to the cortical and subcortical pathways for visual fear processing, we investigated the temporal relationship between these regions in visual processing in rats. A quick flash-evoked potential (FEP) component was identified in the AMY. This emerged as early as in the LGN and was approximately 25 ms prior to the earliest component recorded in the SC, which was assumed to be an important area in visual fear. This quick P1 component in the AMY was not affected by restraint stress or corticosterone injection, but was diminished by RU38486, a glucocorticoid receptor blocker. By injecting a monosynaptic retrograde AAV tracer into the AMY, we found that it received a direct projection from the retina. These results confirm the existence of a direct connection from the retina to the AMY, that the latency in the AMY to flashes is equivalent to that in the sensory thalamus, and that the response is modulated by glucocorticoids.

The tectum/superior colliculus as the vertebrate solution for spatial sensory integration and action

The superior colliculus, or tectum in the case of non-mammalian vertebrates, is a part of the brain that registers events in the surrounding space, often through vision and hearing, but also through electrosensation, infrared detection, and other sensory modalities in diverse vertebrate lineages. This information is used to form maps of the surrounding space and the positions of different salient stimuli in relation to the individual. The sensory maps are arranged in layers with visual input in the uppermost layer, other senses in deeper positions, and a spatially aligned motor map in the deepest layer. Here, we will review the organization and intrinsic function of the tectum/superior colliculus and the information that is processed within tectal circuits. We will also discuss tectal/superior colliculus outputs that are conveyed directly to downstream motor circuits or via the thalamus to cortical areas to control various aspects of behavior. The tectum/superior colliculus is evolutionarily conserved among all vertebrates, but tailored to the sensory specialties of each lineage, and its roles have shifted with the emergence of the cerebral cortex in mammals. We will illustrate both the conserved and divergent properties of the tectum/superior colliculus through vertebrate evolution by comparing tectal processing in lampreys belonging to the oldest group of extant vertebrates, larval zebrafish, rodents, and other vertebrates including primates.

A Prototypical Template for Rapid Face Detection Is Embedded in the Monkey Superior Colliculus

Human babies respond preferentially to faces or face-like images. It has been proposed that an innate and rapid face detection system is present at birth before the cortical visual pathway is developed in many species, including primates. However, in primates, the visual area responsible for this process is yet to be unraveled. We hypothesized that the superior colliculus (SC) that receives direct and indirect retinal visual inputs may serve as an innate rapid face-detection system in primates. To test this hypothesis, we examined the responsiveness of monkey SC neurons to first-order information of faces required for face detection (basic spatial layout of facial features including eyes, nose, and mouth), by analyzing neuronal responses to line drawing images of: (1) face-like patterns with contours and properly placed facial features; (2) non-face patterns including face contours only; and (3) nonface random patterns with contours and randomly placed face features. Here, we show that SC neurons respond stronger and faster to upright and inverted face-like patterns compared to the responses to nonface patterns, regardless of contrast polarity and contour shapes. Furthermore, SC neurons with central receptive fields (RFs) were more selective to face-like patterns. In addition, the population activity of SC neurons with central RFs can discriminate face-like patterns from nonface patterns as early as 50 ms after the stimulus onset. Our results provide strong neurophysiological evidence for the involvement of the primate SC in face detection and suggest the existence of a broadly tuned template for face detection in the subcortical visual pathway.

Ultra High Field fMRI of Human Superior Colliculi Activity during Affective Visual Processing

Research on rodents and non-human primates has established the involvement of the superior colliculus in defensive behaviours and visual threat detection. The superior colliculus has been well-studied in humans for its functional roles in saccade and visual processing, but less is known about its involvement in affect. In standard functional MRI studies of the human superior colliculus, it is challenging to discern activity in the superior colliculus from activity in surrounding nuclei such as the periaqueductal gray due to technological and methodological limitations. Employing high-field strength (7 Tesla) fMRI techniques, this study imaged the superior colliculus at high (0.75 mm isotropic) resolution, which enabled isolation of the superior colliculus from other brainstem nuclei. Superior colliculus activation during emotionally aversive image viewing blocks was greater than that during neutral image viewing blocks. These findings suggest that the superior colliculus may play a role in shaping subjective emotional experiences in addition to its visuomotor functions, bridging the gap between affective research on humans and non-human animals.

Superior Colliculus Lesions Lead to Disrupted Responses to Light in Diurnal Grass Rats (Arvicanthis niloticus)

The circadian system regulates daily rhythms of physiology and behavior. Although extraordinary advances have been made to elucidate the brain mechanisms underlying the circadian system in nocturnal species, less is known in diurnal species. Recent studies have shown that retinorecipient brain areas such as the intergeniculate leaflet (IGL) and olivary pretectal nucleus (OPT) are critical for the display of normal patterns of daily activity in diurnal grass rats (Arvicanthis niloticus). Specifically, grass rats with IGL and OPT lesions respond to light in similar ways to intact nocturnal animals. Importantly, both the IGL and OPT project to one another in nocturnal species, and there is evidence that these 2 brain regions also project to the superior colliculus (SC). The SC receives direct retinal input, is involved in the triggering of rapid eye movement sleep in nocturnal rats, and is disproportionately large in the diurnal grass rat. The objective of the current study was to use diurnal grass rats to test the hypothesis that the SC is critical for the expression of diurnal behavior and physiology. We performed bilateral electrolytic lesions of the SC in female grass rats to examine behavioral patterns and acute responses to light. Most grass rats with SC lesions expressed significantly reduced activity in the presence of light. Exposing these grass rats to constant darkness reinstated activity levels during the subjective day, suggesting that light masks their ability to display a diurnal activity profile in 12:12 LD. Altogether, our data suggest that the SC is critical for maintaining normal responses to light in female grass rats.

Autism Pathogenesis: The Superior Colliculus

After been exposed to the visual input, in the first year of life, the brain experiences subtle but massive changes apparently crucial for communicative/emotional and social human development. Its lack could be the explanation of the very high prevalence of autism in children with total congenital blindness. The present theory postulates that the superior colliculus is the key structure for such changes for several reasons: it dominates visual behavior during the first months of life; it is ready at birth for complex visual tasks; it has a significant influence on several hemispheric regions; it is the main brain hub that permanently integrates visual and non-visual, external and internal information (bottom-up and top-down respectively); and it owns the enigmatic ability to take non-conscious decisions about where to focus attention. It is also a sentinel that triggers the subcortical mechanisms which drive social motivation to follow faces from birth and to react automatically to emotional stimuli. Through indirect connections it also activates simultaneously several cortical structures necessary to develop social cognition and to accomplish the multiattentional task required for conscious social interaction in real life settings. Genetic or non-genetic prenatal or early postnatal factors could disrupt the SC functions resulting in autism. The timing of postnatal biological disruption matches the timing of clinical autism manifestations. Astonishing coincidences between etiologies, clinical manifestations, cognitive and pathogenic autism theories on one side and SC functions on the other are disclosed in this review. Although the visual system dependent of the SC is usually considered as accessory of the LGN canonical pathway, its imprinting gives the brain a qualitatively specific functions not supplied by any other brain structure.

Pulvinar Lesions Disrupt Fear-Related Implicit Visual Processing in Hemianopic Patients

The processing of emotional stimuli in the absence of awareness has been widely investigated in patients with lesions to the primary visual pathway since the classical studies on affective blindsight. In addition, recent evidence has shown that in hemianopic patients without blindsight only unseen fearful faces can be implicitly processed, inducing enhanced visual encoding (Cecere et al., 2014) and response facilitation (Bertini et al., 2013, 2017) to stimuli presented in their intact field. This fear-specific facilitation has been suggested to be mediated by activity in the spared visual subcortical pathway, comprising the superior colliculus (SC), the pulvinar and the amygdala. This suggests that the pulvinar might represent a critical relay structure, conveying threat-related visual information through the subcortical visual circuit. To test this hypothesis, hemianopic patients, with or without pulvinar lesions, performed a go/no-go task in which they had to discriminate simple visual stimuli, consisting in Gabor patches, displayed in their intact visual field, during the simultaneous presentation of faces with fearful, happy, and neutral expressions in their blind visual field. In line with previous evidence, hemianopic patients without pulvinar lesions showed response facilitation to stimuli displayed in the intact field, only while concurrent fearful faces were shown in their blind field. In contrast, no facilitatory effect was found in hemianopic patients with lesions of the pulvinar. These findings reveal that pulvinar lesions disrupt the implicit visual processing of fearful stimuli in hemianopic patients, therefore suggesting a pivotal role of this structure in relaying fear-related visual information from the SC to the amygdala.

Association Between Fear and Beauty Evaluation of Snakes: Cross-Cultural Findings

According to the fear module theory, humans are evolutionarily predisposed to perceive snakes as prioritized stimuli and exhibit a fast emotional and behavioral response toward them. In Europe, highly dangerous snake species are distributed almost exclusively in the Mediterranean and Caspian areas. While the risk of a snakebite is relatively low in Central Europe, Azerbaijan, on the other hand, has a high occurrence of the deadly venomous Levant viper (Macrovipera lebetina). We hypothesize that co-habitation with this dangerous snake has shaped the way in which humans evaluate snake species resembling it. For that purpose, we asked respondents from the Czech Republic and Azerbaijan to rank photographs depicting 36 snake species according to perceived fear and beauty. The results revealed a high cross-cultural agreement in both evaluations (fear r² = 0.683, p < 0.0001; beauty: r² = 0.816, p < 0.0001). Snakes species eliciting higher fear tend to be also perceived as more beautiful, yet people are able to clearly distinguish between these two dimensions. Deadly venomous snakes representing a serious risk are perceived as highly fearful. This is especially true for the vipers and allies (pit vipers) possessing a characteristic body shape with a distinct triangular head and thick body, which was found as the most fear evoking by respondents from both countries. Although the attitude toward snakes is more negative among the respondents from Azerbaijan, their fear evaluation is similar to the Czechs. For instance, despite co-habitation with the Levant viper, it was not rated by the Azerbaijanis as more fearful than other dangerous snakes. In conclusion, agreement in the evaluation of snake fear and beauty is cross-culturally high and relative fear attributed to selected snake species is not directly explainable by the current environmental and cultural differences. This may provide some support for the evolutionary hypothesis of preparedness to fear snakes.

Early visual processing of snakes and angry faces: An ERP study

Snakes and angry faces are common fear stimuli and both elicit an Early Posterior Negativity (EPN) in the event-related potential, which indicates that they capture early automatic visual attention. But because snakes have been a predatory threat for primates since long before communication through facial expressions evolved, we tested the hypothesis that the EPN for snakes would be more pronounced than the EPN for angry faces. We carefully controlled for differences between reptiles and faces by using lizards and neutral faces as control stimuli. Participants viewed a rapid serial visual presentation of snakes (i.e., threatening reptiles), lizards (i.e., non-threatening reptiles), angry faces (i.e., threatening humans), and neutral faces (i.e., non-threatening humans). EPNs for snakes (vs. lizards) and angry (vs. neutral) faces started to develop around 120 ms after stimulus onset. The EPN was of the same size for snakes and angry faces between 150-225 ms, but was larger for snakes than for angry faces between 225-300 ms, which suggests that snakes capture more extensive early automatic attention than angry faces. These findings correspond with the notion that the visual system is specifically tuned to detect snakes because of the prolonged pressure of snakes on primate evolution.

"Low road" to rehabilitation: a perspective on subliminal sensory neuroprosthetics

Fear can propagate parallelly through both cortical and subcortical pathways. It can instigate memory consolidation habitually and might allow internal simulation of movements independent of the cortical structures. This perspective suggests delivery of subliminal, aversive and kinematic audiovisual stimuli via neuroprosthetics in patients with neocortical dysfunctions. We suggest possible scenarios by which these stimuli might bypass damaged neocortical structures and possibly assisting in motor relearning. Anticipated neurophysiological mechanisms and methodological scenarios have been discussed in this perspective. This approach introduces novel perspectives into neuropsychology as to how subcortical pathways might be used to induce motor relearning.

Superior colliculus resting state networks in post-traumatic stress disorder and its dissociative subtype

OBJECTIVES

The innate alarm system (IAS) models the neurocircuitry involved in threat processing in posttraumatic stress disorder (PTSD). Here, we investigate a primary subcortical structure of the IAS model, the superior colliculus (SC), where the SC is thought to contribute to the mechanisms underlying threat-detection in PTSD. Critically, the functional connectivity between the SC and other nodes of the IAS remains unexplored.

EXPERIMENTAL DESIGN

We conducted a resting-state fMRI study to investigate the functional architecture of the IAS, focusing on connectivity of the SC in PTSD (n = 67), its dissociative subtype (n = 41), and healthy controls (n = 50) using region-of-interest seed-based analysis.

PRINCIPAL OBSERVATIONS

We observed group-specific resting state functional connectivity between the SC for both PTSD and its dissociative subtype, indicative of dedicated IAS collicular pathways in each group of patients. When comparing PTSD to its dissociative subtype, we observed increased resting state functional connectivity between the left SC and the right dorsolateral prefrontal cortex (DLPFC) in PTSD. The DLPFC is involved in modulation of emotional processes associated with active defensive responses characterising PTSD. Moreover, when comparing PTSD to its dissociative subtype, increased resting state functional connectivity was observed between the right SC and the right temporoparietal junction in the dissociative subtype. The temporoparietal junction is involved in depersonalization responses associated with passive defensive responses typical of the dissociative subtype.

CONCLUSIONS

Our findings suggest that unique resting state functional connectivity of the SC parallels the unique symptom profile and defensive responses observed in PTSD and its dissociative subtype. Hum Brain Mapp 39:563-574, 2018. © 2017 Wiley Periodicals, Inc.

A translational study on looming-evoked defensive response and the underlying subcortical pathway in autism

Rapidly approaching objects indicating threats can induce defensive response through activating a subcortical pathway comprising superior colliculus (SC), lateral posterior nucleus (LP), and basolateral amygdala (BLA). Abnormal defensive response has been reported in autism, and impaired synaptic connections could be the underlying mechanism. Whether the SC-LP-BLA pathway processes looming stimuli abnormally in autism is not clear. Here, we found that looming-evoked defensive response is impaired in a subgroup of the valproic acid (VPA) mouse model of autism. By combining the conventional neurotracer and transneuronal rabies virus tracing techniques, we demonstrated that synaptic connections in the SC-LP-BLA pathway were abnormal in VPA mice whose looming-evoked defensive responses were absent. Importantly, we further translated the finding to children with autism and observed that they did not present looming-evoked defensive response. Furthermore, the findings of the DTI with the probabilistic tractography showed that the structural connections of SC-pulvinar-amygdala in autism children were weak. The pulvinar is parallel to the LP in a mouse. Because looming-evoked defensive response is innate in humans and emerges much earlier than do social and language functions, the absence of defensive response could be an earlier sign of autism in children.

Basic Emotions in Human Neuroscience: Neuroimaging and Beyond

The existence of so-called ‘basic emotions’ and their defining attributes represents a long lasting and yet unsettled issue in psychology. Recently, neuroimaging evidence, especially related to the advent of neuroimaging meta-analytic methods, has revitalized this debate in the endeavor of systems and human neuroscience. The core theme focuses on the existence of unique neural bases that are specific and characteristic for each instance of basic emotion. Here we review this evidence, outlining contradictory findings, strengths and limits of different approaches. Constructionism dismisses the existence of dedicated neural structures for basic emotions, considering that the assumption of a one-to-one relationship between neural structures and their functions is central to basic emotion theories. While these critiques are useful to pinpoint current limitations of basic emotions theories, we argue that they do not always appear equally generative in fostering new testable accounts on how the brain relates to affective functions. We then consider evidence beyond PET and fMRI, including results concerning the relation between basic emotions and awareness and data from neuropsychology on patients with focal brain damage. Evidence from lesion studies are indeed particularly informative, as they are able to bring correlational evidence typical of neuroimaging studies to causation, thereby characterizing which brain structures are necessary for, rather than simply related to, basic emotion processing. These other studies shed light on attributes often ascribed to basic emotions, such as automaticity of perception, quick onset, and brief duration. Overall, we consider that evidence in favor of the neurobiological underpinnings of basic emotions outweighs dismissive approaches. In fact, the concept of basic emotions can still be fruitful, if updated to current neurobiological knowledge that overcomes traditional one-to-one localization of functions in the brain. In particular, we propose that the structure-function relationship between brain and emotions is better described in terms of pluripotentiality, which refers to the fact that one neural structure can fulfill multiple functions, depending on the functional network and pattern of co-activations displayed at any given moment.

Fast Detector/First Responder: Interactions between the Superior Colliculus-Pulvinar Pathway and Stimuli Relevant to Primates

Primates are distinguished from other mammals by their heavy reliance on the visual sense, which occurred as a result of natural selection continually favoring those individuals whose visual systems were more responsive to challenges in the natural world. Here we describe two independent but also interrelated visual systems, one cortical and the other subcortical, both of which have been modified and expanded in primates for different functions. Available evidence suggests that while the cortical visual system mainly functions to give primates the ability to assess and adjust to fluid social and ecological environments, the subcortical visual system appears to function as a rapid detector and first responder when time is of the essence, i.e., when survival requires very quick action. We focus here on the subcortical visual system with a review of behavioral and neurophysiological evidence that demonstrates its sensitivity to particular, often emotionally charged, ecological and social stimuli, i.e., snakes and fearful and aggressive facial expressions in conspecifics. We also review the literature on subcortical involvement during another, less emotional, situation that requires rapid detection and response-visually guided reaching and grasping during locomotion-to further emphasize our argument that the subcortical visual system evolved as a rapid detector/first responder, a function that remains in place today. Finally, we argue that investigating deficits in this subcortical system may provide greater understanding of Parkinson's disease and Autism Spectrum disorders (ASD).

Amygdala Response to Emotional Stimuli without Awareness: Facts and Interpretations

Over the past two decades, evidence has accumulated that the human amygdala exerts some of its functions also when the observer is not aware of the content, or even presence, of the triggering emotional stimulus. Nevertheless, there is as of yet no consensus on the limits and conditions that affect the extent of amygdala’s response without focused attention or awareness. Here we review past and recent studies on this subject, examining neuroimaging literature on healthy participants as well as brain-damaged patients, and we comment on their strengths and limits. We propose a theoretical distinction between processes involved in attentional unawareness, wherein the stimulus is potentially accessible to enter visual awareness but fails to do so because attention is diverted, and in sensory unawareness, wherein the stimulus fails to enter awareness because its normal processing in the visual cortex is suppressed. We argue this distinction, along with data sampling amygdala responses with high temporal resolution, helps to appreciate the multiplicity of functional and anatomical mechanisms centered on the amygdala and supporting its role in non-conscious emotion processing. Separate, but interacting, networks relay visual information to the amygdala exploiting different computational properties of subcortical and cortical routes, thereby supporting amygdala functions at different stages of emotion processing. This view reconciles some apparent contradictions in the literature, as well as seemingly contrasting proposals, such as the dual stage and the dual route model. We conclude that evidence in favor of the amygdala response without awareness is solid, albeit this response originates from different functional mechanisms and is driven by more complex neural networks than commonly assumed. Acknowledging the complexity of such mechanisms can foster new insights on the varieties of amygdala functions without awareness and their impact on human behavior.

Snakes elicit earlier, and monkey faces, later, gamma oscillations in macaque pulvinar neurons

Gamma oscillations (30-80 Hz) have been suggested to be involved in feedforward visual information processing, and might play an important role in detecting snakes as predators of primates. In the present study, we analyzed gamma oscillations of pulvinar neurons in the monkeys during a delayed non-matching to sample task, in which monkeys were required to discriminate 4 categories of visual stimuli (snakes, monkey faces, monkey hands and simple geometrical patterns). Gamma oscillations of pulvinar neuronal activity were analyzed in three phases around the stimulus onset (Pre-stimulus: 500 ms before stimulus onset; Early: 0-200 ms after stimulus onset; and Late: 300-500 ms after stimulus onset). The results showed significant increases in mean strength of gamma oscillations in the Early phase for snakes and the Late phase for monkey faces, but no significant differences in ratios and frequencies of gamma oscillations among the 3 phases. The different periods of stronger gamma oscillations provide neurophysiological evidence that is consistent with other studies indicating that primates can detect snakes very rapidly and also cue in to faces for information. Our results are suggestive of different roles of gamma oscillations in the pulvinar: feedforward processing for images of snakes and cortico-pulvinar-cortical integration for images of faces.

I'll take the low road: the evolutionary underpinnings of visually triggered fear

Although there is general agreement that the central nucleus of the amygdala (CeA) is critical for triggering the neuroendocrine response to visual threats, there is uncertainty about the role of subcortical visual pathways in this process. Primates in general appear to depend less on subcortical visual pathways than other mammals. Yet, imaging studies continue to indicate a role for the superior colliculus and pulvinar nucleus in fear activation, despite disconnects in how these brain structures communicate not only with each other but with the amygdala. Studies in fish and amphibians suggest that the neuroendocrine response to visual threats has remained relatively unchanged for hundreds of millions of years, yet there are still significant data gaps with respect to how visual information is relayed to telencephalic areas homologous to the CeA, particularly in fish. In fact ray finned fishes may have evolved an entirely different mechanism for relaying visual information to the telencephalon. In part because they lack a pathway homologous to the lateral geniculate-striate cortex pathway of mammals, amphibians continue to be an excellent model for studying how stress hormones in turn modulate fear activating visual pathways. Glucocorticoids, melanocortin peptides, and CRF all appear to play some role in modulating sensorimotor processing in the optic tectum. These observations, coupled with data showing control of the hypothalamus-pituitary-adrenal axis by the superior colliculus, suggest a fear/stress/anxiety neuroendocrine circuit that begins with first order synapses in subcortical visual pathways. Thus, comparative studies shed light not only on how fear triggering visual pathways came to be, but how hormones released as a result of this activation modulate these pathways.