Neural-activity mapping of memory-based dominance in the crow: neural networks integrating individual discrimination and social behaviour control

Social encounters produce different autonomic response between dominants and subordinates in crows

Recent studies of behavioural physiology on animals have suggested the crucial role of peripherally physiological signals in eliciting arousal and emotion. Heart rate (HR) is one of the useful and critical signals to measure autonomic regulation as a physiological basis for arousal and emotion in response to biologically significant stimuli such as social encounter with conspecific individuals. However, our understanding of peripherally physiological response such as HRs and autonomic activities under social contexts of non-human animals is still limited, particularly in birds. Here, we examined the autonomic activity of behaving crows exposed to a dominant and a subordinate conspecific by using non-invasive electrocardiogram recording. We found different patterns of autonomic responses dependent on the relative dominance position: dominant crows encountering subordinates showed the elevation of sympathetic activity, whereas subordinates encountering dominants showed decreased HR with elevated parasympathetic activity. This is the first study in birds to report different autonomic responses dependent on relative dominance positions during dyadic social encounters. The present study advances our understanding of the role of the peripheral autonomic system, as an interactive system with the brain, in eliciting emotion/arousal associated with socially challenging environments from an evolutionary perspective.

American Crow Brain Activity in Response to Conspecific Vocalizations Changes When Food Is Present

Social interaction among animals can occur under many contexts, such as during foraging. Our knowledge of the regions within an avian brain associated with social interaction is limited to the regions activated by a single context or sensory modality. We used 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) to examine American crow (Corvus brachyrhynchos) brain activity in response to conditions associated with communal feeding. Using a paired approach, we exposed crows to either a visual stimulus (the sight of food), an audio stimulus (the sound of conspecifics vocalizing while foraging) or both audio/visual stimuli presented simultaneously and compared to their brain activity in response to a control stimulus (an empty stage). We found two regions, the nucleus taenia of the amygdala (TnA) and a medial portion of the caudal nidopallium, that showed increased activity in response to the multimodal combination of stimuli but not in response to either stimulus when presented unimodally. We also found significantly increased activity in the lateral septum and medially within the nidopallium in response to both the audio-only and the combined audio/visual stimuli. We did not find any differences in activation in response to the visual stimulus by itself. We discuss how these regions may be involved in the processing of multimodal stimuli in the context of social interaction.

Neural basis of unfamiliar conspecific recognition in domestic chicks (Gallus Gallus domesticus)

Domestic chickens are able to distinguish familiar from unfamiliar conspecifics, however the neuronal mechanisms mediating this behaviour are almost unknown. Moreover, the lateralisation of chicks' social recognition has only been investigated at the behavioural level, but not at the neural level. The aim of the present study was to test the hypothesis that exposure to unfamiliar conspecifics will selectively activate septum, hippocampus or nucleus taeniae of the amygdala of young domestic chicks. Moreover we also wanted to test the lateralisation of this response. For this purpose, we used the immediate early gene product c-Fos to map neural activity. Chicks were housed in pairs for one week. At test, either one of the two chicks was exchanged by an unfamiliar individual (experimental 'unfamiliar' group) or the familiar individual was briefly removed and then placed back in its original cage (control 'familiar' group). Analyses of chicks' interactions with the familiar/unfamiliar social companion revealed a higher number of social pecks directed towards unfamiliar individuals, compared to familiar controls. Moreover, in the group exposed to the unfamiliar individual a significantly higher activation was present in the dorsal and ventral septum of the left hemisphere and in the ventral hippocampus of the right hemisphere, compared to the control condition. These effects were neither present in other subareas of hippocampus or septum, nor in the nucleus taeniae of the amygdala. Our study thus indicates selective lateralised involvement of domestic chicks' septal and hippocampal subregions in responses to unfamiliar conspecific.

Brain activity underlying American crow processing of encounters with dead conspecifics

Animals utilize a variety of auditory and visual cues to navigate the landscape of fear. For some species, including corvids, dead conspecifics appear to act as one such visual cue of danger, and prompt alarm calling by attending conspecifics. Which brain regions mediate responses to dead conspecifics, and how this compares to other threats, has so far only been speculative. Using 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) we contrast the metabolic response to visual and auditory cues associated with a dead conspecific among five a priori selected regions in the American crow (Corvus brachyrhynchos) brain: the hippocampus, nidopallium caudolaterale, striatum, amygdala, and the septum. Using a repeated-measures, fully balanced approach, we exposed crows to four stimuli: a dead conspecific, a dead song sparrow (Melospiza melodia), conspecific alarm calls given in response to a dead crow, and conspecific food begging calls. We find that in response to observations of a dead crow, crows show significant activity in areas associated with higher-order decision-making (NCL), but not in areas associated with social behaviors or fear learning. We do not find strong differences in activation between hearing alarm calls and food begging calls; both activate the NCL. Lastly, repeated exposures to negative stimuli had a marginal effect on later increasing the subjects' brain activity in response to control stimuli, suggesting that crows might quickly learn from negative experiences.

Realigning the Neural Paradigm for Death

Whole brain failure constitutes the diagnostic criterion for death determination in most clinical settings across the globe. Yet the conceptual foundation for its adoption was slow to emerge, has evoked extensive scientific debate since inception, underwent policy revision, and remains contentious in praxis even today. Complications result from the need to relate a unitary construal of the death event with an adequate account of organismal integration and that of the human organism in particular. Advances in the neuroscience of higher human faculties, such as the self, personal identity, and consciousness, and dynamical philosophy of science accounts, however, are yielding a portrait of higher order global integration shared between body and brain. Such conceptual models of integration challenge a praxis relying exclusively on a neurological criterion for death.

Neural activation following offensive aggression in Japanese quail

Aggression is a fundamental part of animal social behaviour. In avian species, little is known about its neural representation. In particular, neural activity following offensive aggression has not been studied in detail. Here, we investigated the patterns of brain activation using immediate-early gene (IEG) expression in male Japanese quail that showed pronounced aggressive behaviours during a 30 min male–male interaction and compared them to those of males that did not interact with a conspecific. In aggressive males, we found a massive induction of the IEG ZENK in pallial brain structures such as the intermediate medial mesopallium, the caudomedial mesopallium and the intermediate medial nidopallium. To a lesser extent, activation was observed in subpallial areas such as the nucleus taeniae of the amygdala and in the medial portion of the bed nucleus of the stria terminalis. Our data suggest that the modulation of aggressive behaviour involves the integration of multisensory information.

Summary: The manuscript describes the pronounced activation of the immediate early gene ZENK in the pallium of male Japanese quails following offensive aggressive behaviour.

Social Memory Formation Rapidly and Differentially Affects the Motivation and Performance of Vocal Communication Signals in the Bengalese Finch (Lonchura striata var. domestica)

Cognitive processes like the formation of social memories can shape the nature of social interactions between conspecifics. Male songbirds use vocal signals during courtship interactions with females, but the degree to which social memory and familiarity influences the likelihood and structure of male courtship song remains largely unknown. Using a habituation-dishabituation paradigm, we found that a single, brief (<30 s) exposure to a female led to the formation of a short-term memory for that female: adult male Bengalese finches were significantly less likely to produce courtship song to an individual female when re-exposed to her 5 min later (i.e., habituation). Familiarity also rapidly decreased the duration of courtship songs but did not affect other measures of song performance (e.g., song tempo and the stereotypy of syllable structure and sequencing). Consistent with a contribution of social memory to the decrease in courtship song with repeated exposures to the same female, the likelihood that male Bengalese finches produced courtship song increased when they were exposed to a different female (i.e., dishabituation). Three consecutive exposures to individual females also led to the formation of a longer-term memory that persisted over days. Specifically, when courtship song production was assessed 2 days after initial exposures to females, males produced fewer and shorter courtship songs to familiar females than to unfamiliar females. Measures of song performance, however, were not different between courtship songs produced to familiar and unfamiliar females. The formation of a longer-term memory for individual females seemed to require at least three exposures because males did not differentially produce courtship song to unfamiliar females and females that they had been exposed to only once or twice. Taken together, these data indicate that brief exposures to individual females led to the rapid formation and persistence of social memories and support the existence of distinct mechanisms underlying the motivation to produce and the performance of courtship song.

Associative learning rapidly establishes neuronal representations of upcoming behavioral choices in crows

The ability to form associations between behaviorally relevant sensory stimuli is fundamental for goal-directed behaviors. We investigated neuronal activity in the telencephalic area nidopallium caudolaterale (NCL) while two crows (Corvus corone) performed a delayed association task. Whereas some paired associates were familiar to the crows, novel associations had to be learned and mapped to the same target stimuli within a single session. We found neurons that prospectively encoded the chosen test item during the delay for both familiar and newly learned associations. These neurons increased their selectivity during learning in parallel with the crows' increased behavioral performance. Thus, sustained activity in the NCL actively processes information for the upcoming behavioral choice. These data provide new insights into memory representations of behaviorally meaningful stimuli in birds, and how such representations are formed during learning. The findings suggest that the NCL plays a role in learning arbitrary associations, a cornerstone of corvids' remarkable behavioral flexibility and adaptability.

Distinct neural circuits underlie assessment of a diversity of natural dangers by American crows

Social animals encountering natural dangers face decisions such as whether to freeze, flee or harass the threat. The American crow, Corvus brachyrhynchos, conspicuously mobs dangers. We used positron emission tomography to test the hypothesis that distinct neuronal substrates underlie the crow's consistent behavioural response to different dangers. We found that crows activated brain regions associated with attention and arousal (nucleus isthmo-opticus/locus coeruleus), and with motor response (arcopallium), as they fixed their gaze on a threat. However, despite this consistent behavioural and neural response, the sight of a person who previously captured the crow, a person holding a dead crow and a taxidermy-mounted hawk activated distinct forebrain regions (amygdala, hippocampus and portion of the caudal nidopallium, respectively). We suggest that aspects of mobbing behaviour are guided by unique neural circuits that respond to differences in mental processing-learning, memory formation and multisensory discrimination-required to appropriately nuance a risky behaviour to specific dangers.

Brain imaging reveals neuronal circuitry underlying the crow's perception of human faces

Crows pay close attention to people and can remember specific faces for several years after a single encounter. In mammals, including humans, faces are evaluated by an integrated neural system involving the sensory cortex, limbic system, and striatum. Here we test the hypothesis that birds use a similar system by providing an imaging analysis of an awake, wild animal's brain as it performs an adaptive, complex cognitive task. We show that in vivo imaging of crow brain activity during exposure to familiar human faces previously associated with either capture (threatening) or caretaking (caring) activated several brain regions that allow birds to discriminate, associate, and remember visual stimuli, including the rostral hyperpallium, nidopallium, mesopallium, and lateral striatum. Perception of threatening faces activated circuitry including amygdalar, thalamic, and brainstem regions, known in humans and other vertebrates to be related to emotion, motivation, and conditioned fear learning. In contrast, perception of caring faces activated motivation and striatal regions. In our experiments and in nature, when perceiving a threatening face, crows froze and fixed their gaze (decreased blink rate), which was associated with activation of brain regions known in birds to regulate perception, attention, fear, and escape behavior. These findings indicate that, similar to humans, crows use sophisticated visual sensory systems to recognize faces and modulate behavioral responses by integrating visual information with expectation and emotion. Our approach has wide applicability and potential to improve our understanding of the neural basis for animal behavior.

Crows cross-modally recognize group members but not non-group members

Recognizing other individuals by integrating different sensory modalities is a crucial ability of social animals, including humans. Although cross-modal individual recognition has been demonstrated in mammals, the extent of its use by birds remains unknown. Herein, we report the first evidence of cross-modal recognition of group members by a highly social bird, the large-billed crow (Corvus macrorhynchos). A cross-modal expectancy violation paradigm was used to test whether crows were sensitive to identity congruence between visual presentation of a group member and the subsequent playback of a contact call. Crows looked more rapidly and for a longer duration when the visual and auditory stimuli were incongruent than when congruent. Moreover, these responses were not observed with non-group member stimuli. These results indicate that crows spontaneously associate visual and auditory information of group members but not of non-group members, which is a demonstration of cross-modal audiovisual recognition of group members in birds.