Despite the lack of a layered neocortex and fundamental differences in endbrain organization in birds compared with mammals, intelligent species evolved from both vertebrate classes. Among birds, corvids show exceptional cognitive flexibility. Here we explore the neuronal foundation of corvid cognition by recording single-unit activity from an association area known as the nidopallium caudolaterale (NCL) while carrion crows make flexible rule-guided decisions, a hallmark of executive control functions. The most prevalent activity in NCL represents the behavioural rules, while abstracting over sample images and sensory modalities of the rule cues. Rule coding is weaker in error trials, thus predicting the crows' behavioural decisions. This suggests that the abstraction of general principles may be an important function of the NCL, mirroring the function of primate prefrontal cortex. These findings emphasize that intelligence in vertebrates does not necessarily rely on a neocortex but can be realized in endbrain circuitries that developed independently via convergent evolution.

Accurate timing is a critical aspect of motor control, yet the temporal structure of many mature behaviors emerges during learning from highly variable exploratory actions. How does a developing brain acquire the precise control of timing in behavioral sequences? To investigate the development of timing, we analyzed the songs of young juvenile zebra finches. These highly variable vocalizations, akin to human babbling, gradually develop into temporally-stereotyped adult songs. We find that the durations of syllables and silences in juvenile singing are formed by a mixture of two distinct modes of timing – a random mode producing broadly-distributed durations early in development, and a stereotyped mode underlying the gradual emergence of stereotyped durations. Using lesions, inactivations, and localized brain cooling we investigated the roles of neural dynamics within two premotor cortical areas in the production of these temporal modes. We find that LMAN (lateral magnocellular nucleus of the nidopallium) is required specifically for the generation of the random mode of timing, and that mild cooling of LMAN causes an increase in the durations produced by this mode. On the contrary, HVC (used as a proper name) is required specifically for producing the stereotyped mode of timing, and its cooling causes a slowing of all stereotyped components. These results show that two neural pathways contribute to the timing of juvenile songs, and suggest an interesting organization in the forebrain, whereby different brain areas are specialized for the production of distinct forms of neural dynamics.

The concept of working memory is key to cognitive functioning. Working memory encompasses the capacity to retain immediately past information, to process this information, and to use it to guide goal-directed behavior. Corvid songbirds are renowned for their high-level cognitive capabilities, but where and how visual information is temporarily retained by neurons in the avian brain in a behaviorally relevant way remains poorly understood. We trained four carrion crows (Corvus corone) on versions of a delayed match-to-sample task that required the crows to remember a visual stimulus for later comparison. While the crows performed the task, we recorded the activity of single neurons in the nidopallium caudolaterale (NCL), a pallial association area of the avian endbrain. We show that many NCL neurons encode information about visual stimuli and temporarily maintain this information after the stimulus disappeared by sustained delay activity. Selective delay activity allows the birds to hold relevant information in memory and correlates with discrimination behavior. This suggests that sustained activity of NCL neurons is a neuronal correlate of visual working memory in the corvid brain and serves to bridge temporal gaps, thereby offering a workspace for processing immediately past visual information.

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.association learning | crow | single-cell recordings | nidopallium caudolaterale | memory T he ability to form arbitrary associations between sensory stimuli is fundamental for many flexible goal-directed behaviors. Corvids exploit learned associations intensively when adapting their behavior to a changing environment (1, 2). For example, scrub jays learn to associate different foods with different degradation speeds as a component of their episodic-like memory during food-caching behavior (3). The neuronal basis of corvids' ability to learn arbitrary associations has never been investigated.The avian cognitive integration area nidopallium caudolaterale (NCL) is a good candidate to investigate learning-related changes in the representation of initially unknown stimuli, as they acquire behavioral meaning during association learning. We have recently demonstrated that single NCL neurons encode abstract behavioral rules, irrespective of the arbitrary, learned cues used to instruct the rule (4). Furthermore, pigeons with lesions of the NCL show deficits in a reversal learning task, indicating that the NCL is a crucial structure to flexibly adapt behavior based on feedback during learning (5). The NCL is the main pallial target of dopaminergic projections from the midbrain (6), and dopamine signaling in striatal and cortical structures is involved in learning and memory processes in birds, as in mammals (7).Here we investigate changes in the neuronal representation while associative learning links arbitrary visual items in memory. We trained two carrion crows on a delayed paired-association learning (DPA) task and recorded NCL neurons during the course of learning. The task design allowed us to compare neuronal responses during the mapping of highly familiar images onto test items, as well as to follow the emergence of associative signals in the same neurons while the crows learned to map novel sample images onto the ...

How do animals with learned vocalizations coordinate vocal production with respiration? Songbirds such as the zebra finch learn their songs, beginning with highly variable babbling vocalizations known as subsong. After several weeks of practice, zebra finches are able to produce a precisely timed pattern of syllables and silences, precisely coordinated with expiratory and inspiratory pulses (Franz M, Goller F. J Neurobiol 51: 129-141, 2002). While respiration in adult song is well described, relatively little is known about respiratory patterns in subsong or about the processes by which respiratory and vocal patterns become coordinated. To address these questions, we recorded thoracic air sac pressure in juvenile zebra finches prior to the appearance of any consistent temporal or acoustic structure in their songs. We found that subsong contains brief inspiratory pulses (50 ms) alternating with longer pulses of sustained expiratory pressure (50-500 ms). In striking contrast to adult song, expiratory pulses often contained multiple (0-8) variably timed syllables separated by expiratory gaps and were only partially vocalized. During development, expiratory pulses became shorter and more stereotyped in duration with shorter and fewer nonvocalized parts. These developmental changes eventually resulted in the production of a single syllable per expiratory pulse and a single inspiratory pulse filling each gap, forming a coordinated sequence similar to that of adult song. To examine the role of forebrain song-control nuclei in the development of respiratory patterns, we performed pressure recordings before and after lesions of nucleus HVC (proper name) and found that this manipulation reverses the developmental trends in measures of the respiratory pattern.

The flexible control of sequential behavior is a fundamental aspect of speech, enabling endless reordering of a limited set of learned vocal elements (syllables or words). Songbirds are phylogenetically distant from humans but share both the capacity for vocal learning and neural circuitry for vocal control that includes direct pallial-brainstem projections. Based on these similarities, we hypothesized that songbirds might likewise be able to learn flexible, moment-by-moment control over vocalizations. Here, we demonstrate that Bengalese finches (Lonchura striata domestica), which sing variable syllable sequences, can learn to rapidly modify the probability of specific sequences (e.g. ‘ab-c’ versus ‘ab-d’) in response to arbitrary visual cues. Moreover, once learned, this modulation of sequencing occurs immediately following changes in contextual cues and persists without external reinforcement. Our findings reveal a capacity in songbirds for learned contextual control over syllable sequencing that parallels human cognitive control over syllable sequencing in speech.

The avian pallial endbrain area nidopallium caudolaterale (NCL) shows important similarities to mammalian prefrontal cortex in connectivity, dopamine neurochemistry, and function. Neuronal processing in NCL has been studied with respect to sensory, cognitive, and reward information, but little is known about its role in more direct control of motor behavior. We investigated NCL activity during the choice period of a delayed match-to-sample task, as 2 trained crows searched and selected a previously remembered visual target among an array of 4 pictures. The crows exhibited behavioral response patterns consistent with serial visual search. Many single NCL neurons were spatially tuned to specific target positions during visual search and directed motor behavior. Moreover, single NCL neurons dynamically changed their tuning properties to represent different behaviorally relevant task variables across the trial. In consecutive task periods, single neurons responded to visual stimuli, stored stimulus information in working memory, guided goal-directed behavior depending on the remembered target picture, and encoded trial outcomes. This flexible encoding of all task-relevant aspects in the executive control of goal-directed behavior represents a striking convergence to neuronal encoding in primate prefrontal cortex. These data highlight key properties of associative endbrain areas underlying flexible cognitive behavior in corvids and primates.

Adaptive sequential behaviors rely on the bridging and integration of temporally separate information for the realization of prospective goals. Corvids' remarkable behavioral flexibility is thought to depend on the workings of the nidopallium caudolaterale (NCL), a high-level avian associative forebrain area. We trained carrion crows to remember visual items for three alternating delay durations in a delayed match-to-sample task and recorded single-unit activity from the NCL. Sample-selective delay activity, a correlate of visual working memory, was maintained throughout different working memory durations. Delay responses remained selective for the same preferred sample item across blocks with different delay durations. However, selectivity strength decreased with increasing delay durations, mirroring worsened behavioral performance with longer memory delays. Behavioral relevance of delay activity was further evidenced by reduced encoding of the preferred sample item during error trials. In addition, NCL neurons adapted their time-dependent discharges to blocks of different memory durations, so that delay duration could be successfully classified based on population activity a few trials after the delay duration switched. Therefore, NCL neurons not only maintain information from individual trials, but also keep track of the duration for which this information is needed in the context of the task. These results strengthen the role of corvid NCL in maintaining working memory for flexible control of temporally extended goal-directed behavior.