Damage-induced alarm cues influence lateralized behaviour but not the relationship between behavioural and habenular asymmetry in convict cichlids (Amatitlania nigrofasciata).

Cerebral lateralization, the partitioning of functions into a certain hemisphere of the brain, is ubiquitous among vertebrates. Evidence suggests that the cognitive processing of a stimulus is performed with a specific hemisphere depending in part upon the emotional valence of the stimulus (i.e. whether it is appetitive or aversive). Recent work has implicated a predominance of right-hemisphere processing for aversive stimuli. In fish with laterally placed eyes, the preference to view an object with a specific eye has been used as a proxy for assessing cerebral lateralization. The habenula, one of the most well-known examples of an asymmetrical neural structure, has been linked to behavioural asymmetry in some fish species. Here, we exposed convict cichlid fish (Amatitlania nigrofasciata) to both a social and non-social lateralization task and assessed behavioural lateralization in either the presence or absence of an aversive stimulus, damage-induced alarm cues. We also assessed whether behavioural asymmetry in these tests was related to asymmetry of the habenular nuclei. We found that when alarm cues were present, fish showed increased left-eye (and by proxy, right hemisphere) preference for stimulus viewing. In addition, females, but not males, showed stronger eye preferences when alarm cues were present. We did not find a relationship between behavioural lateralization and habenular lateralization. Our results conflict with previous reports of concordance between behavioural and habenular lateralization in this fish species. However, our results do provide support for the hypothesis of increased right-hemisphere use when an organism is exposed to aversive stimuli.

ZENK activation in the nidopallium of black-capped chickadees in response to both conspecific and heterospecific calls.

Neuronal populations in the songbird nidopallium increase in activity the most to conspecific vocalizations relative to heterospecific songbird vocalizations or artificial stimuli such as tones. Here, we tested whether the difference in neural activity between conspecific and heterospecific vocalizations is due to acoustic differences or to the degree of phylogenetic relatedness of the species producing the vocalizations. To compare differences in neural responses of black-capped chickadees, Poecile atricapillus, to playback conditions we used a known marker for neural activity, ZENK, in the caudal medial nidopallium and caudomedial mesopallium. We used the acoustically complex 'dee' notes from chick-a-dee calls, and vocalizations from other heterospecific species similar in duration and spectral features. We tested the vocalizations from three heterospecific species (chestnut-backed chickadees, tufted titmice, and zebra finches), the vocalizations from conspecific individuals (black-capped chickadees), and reversed versions of the latter. There were no significant differences in the amount of expression between any of the groups except in the control condition, which resulted in significantly less neuronal activation. Our results suggest that, in certain cases, neuronal activity is not higher in response to conspecific than in response to heterospecific vocalizations for songbirds, but rather is sensitive to the acoustic features of the signal. Both acoustic features of the calls and the phylogenetic relationship between of the signaler and the receiver interact in the response of the nidopallium.

Neural correlates of threat perception: neural equivalence of conspecific and heterospecific mobbing calls is learned.

Songbird auditory areas (i.e., CMM and NCM) are preferentially activated to playback of conspecific vocalizations relative to heterospecific and arbitrary noise. Here, we asked if the neural response to auditory stimulation is not simply preferential for conspecific vocalizations but also for the information conveyed by the vocalization. Black-capped chickadees use their chick-a-dee mobbing call to recruit conspecifics and other avian species to mob perched predators. Mobbing calls produced in response to smaller, higher-threat predators contain more "D" notes compared to those produced in response to larger, lower-threat predators and thus convey the degree of threat of predators. We specifically asked whether the neural response varies with the degree of threat conveyed by the mobbing calls of chickadees and whether the neural response is the same for actual predator calls that correspond to the degree of threat of the chickadee mobbing calls. Our results demonstrate that, as degree of threat increases in conspecific chickadee mobbing calls, there is a corresponding increase in immediate early gene (IEG) expression in telencephalic auditory areas. We also demonstrate that as the degree of threat increases for the heterospecific predator, there is a corresponding increase in IEG expression in the auditory areas. Furthermore, there was no significant difference in the amount IEG expression between conspecific mobbing calls or heterospecific predator calls that were the same degree of threat. In a second experiment, using hand-reared chickadees without predator experience, we found more IEG expression in response to mobbing calls than corresponding predator calls, indicating that degree of threat is learned. Our results demonstrate that degree of threat corresponds to neural activity in the auditory areas and that threat can be conveyed by different species signals and that these signals must be learned.

Lateralized behaviour of a non-social cichlid fish (Amatitlania nigrofasciata) in a social and a non-social environment.

Cerebral lateralization, the partitioning of cognitive function preferentially into one hemisphere of the brain, is a trait ubiquitous among vertebrates. Some species exhibit population level lateralization, where the pattern of cerebral lateralization is the same for most members of that species; however, other species show only individual level lateralization, where each member of the species has a unique pattern of lateralized brain function. The pattern of cerebral lateralization within a population and an individual has been shown to differ based on the stimulus being processed. It has been hypothesized that sociality within a species, such as shoaling behaviour in fish, may have led to the development and persistence of population level lateralization. Here we assessed cerebral lateralization in convict cichlids (Amatitlania nigrofasciata), a species that does not shoal as adults but that shoals briefly as juveniles. We show that both male and female convict cichlids display population level lateralization when in a solitary environment but only females show population level lateralization when in a perceived social environment. We also show that the pattern of lateralization differs between these two tasks and that strength of lateralization in one task is not predictive of strength of lateralization in the other task.

Note types and coding in Parid vocalizations: the chick-a-dee call of the boreal chickadee (Poecile hudsonicus).

An important first step in characterizing a vocalization is to classify, describe, and measure the elements of that vocalization. Here, this methodology is employed to study the chick-a-dee call of the boreal chickadee (Poecile hudsonicus). The note types (A, B, C, D, and D(h)) in a sample of boreal chickadee calls are identified and described, spectral and temporal features of each note type are analyzed, and production phenomena in each note type are identified and quantified. Acoustic variability is compared across note types and individuals to determine potential features used for note-type and individual discrimination. Frequency measures appear to be the most useful features for identifying note types and individuals, though total duration may also be useful. Call syntax reveals that boreal chick-a-dee calls follow a general rule of note-type order, namely A-B-C-D(h)-D, and that any note type in this sequence may be repeated or omitted. This work provides a thorough description of the boreal chickadee chick-a-dee call and will serve as a foundation for future studies aimed at elucidating this call's functional significance within this species, as well as for studies comparing chick-a-dee calls across Poecile species.

Note types and coding in Parid vocalizations: the chick-a-dee call of the chestnut-backed chickadee (Poecile rufuscens).

A first step to understanding how a species communicates acoustically is to identify, categorize, and quantify the acoustic parameters of the elements that make up their vocalizations. The "chick-a-dee" call notes of the chestnut-backed chickadee (Poecile rufescens) were sorted into four call note categories, A, C, D, and Dh notes, based on their acoustic structure as observed in sound spectrograms, and evaluated based on the syntactical ordering of the note types within calls. The notes were then analyzed using quantitative measures and it was determined which features have the potential to convey information to discriminate note type, individual, and the geographic origin of the producer. The findings were comparable to previous research of congeners in that chestnut-backed chickadee calls were produced with a relatively fixed syntax and contained similarly structured note types across all geographic regions. Overall this information will form a base for future research on chestnut-backed chickadee vocalizations and will strengthen the foundation for future comparative evolutionary studies.