Behavioural Neurobiology

In a group setting, individuals' perceptions of their own level of dominance or of the dominance level of others, and the ability to adequately control their behavior based on these perceptions are crucial for living within a social environment. Recent advances in neural imaging and molecular technology have enabled researchers to investigate the neural substrates that support the perception of social dominance and the formation of a social hierarchy in humans. At the systems' level, recent studies showed that dominance perception is represented in broad brain regions which include the amygdala, hippocampus, striatum, and various cortical networks such as the prefrontal, and parietal cortices...

The ability to differentiate stimuli predicting positive or negative outcomes is critical for survival, and perturbations of emotional processing underlie many psychiatric disease states. Synaptic plasticity in the basolateral amygdala complex (BLA) mediates the acquisition of associative memories, both positive and negative. Different populations of BLA neurons may encode fearful or rewarding associations, but the identifying features of these populations and the synaptic mechanisms of differentiating positive and negative emotional valence have remained unknown...

As the global population ages, older decision makers will be required to take greater responsibility for their own physical, psychological and financial well-being. With this in mind, researchers have begun to examine the effects of ageing on decision making and associated neural circuits. A new 'affect-integration-motivation' (AIM) framework may help to clarify how affective and motivational circuits support decision making. Recent research has shed light on whether and how ageing influences these circuits, providing an interdisciplinary account of how ageing can alter decision making...

The capacity for self-regulation allows people to control their thoughts, behaviors, emotions, and desires. In spite of this impressive ability, failures of self-regulation are common and contribute to numerous societal problems, from obesity to drug addiction. Such failures frequently occur following exposure to highly tempting cues, during negative moods, or after self-regulatory resources have been depleted. Here we review the available neuroscientific evidence regarding self-regulation and its failures...

Dopamine neurons located in the midbrain play a role in motivation that regulates approach behavior (approach motivation). In addition, activation and inactivation of dopamine neurons regulate mood and induce reward and aversion, respectively. Accumulating evidence suggests that such motivational role of dopamine neurons is not limited to those located in the ventral tegmental area, but also in the substantia nigra. The present paper reviews previous rodent work concerning dopamine's role in approach motivation and the connectivity of dopamine neurons, and proposes two working models: One concerns the relationship between extracellular dopamine concentration and approach motivation...

Facial attractiveness provides a very powerful motivation for sexual and parental behavior. We therefore review the importance of faces to the study of neurobiological control of human reproductive motivations. For heterosexual individuals there is a common brain circuit involving the nucleus accumbens, the medial prefrontal, dorsal anterior cingulate and the orbitofrontal cortices that is activated more by attractive than unattractive faces, particularly for faces of the opposite sex. Behavioral studies indicate parallel effects of attractiveness on incentive salience or willingness to work to see faces...

Love is a complex neurobiological phenomenon, relying on trust, belief, pleasure and reward activities within the brain, i.e., limbic processes. These processes critically involve oxytocin, vasopressin, dopamine, and serotonergic signaling. Moreover, endorphin and endogenous morphinergic mechanisms, coupled to nitric oxide autoregulatory pathways, play a role. Naturally rewarding or pleasurable activities are necessary for survival and appetitive motivation, usually governing beneficial biological behaviors like eating, sex, and reproduction...

The neurobiology of sleep and narcolepsy is reviewed. Non-rapid eye movement (NREM) sleep is generated by neurons in the preoptic region of the hypothalamus and adjacent basal forebrain. Lesions in these regions cause insomnia. Stimulation of these regions rapidly produces sleep onset. The key brain structure for generating REM sleep is the pons and adjacent portions of the midbrain. Damage to the pons and/or caudal midbrain can cause abnormalities in REM sleep. The persistent sleepiness of narcolepsy is a result of a loss of hypocretin function...

PURPOSE OF REVIEW: The basic circuitries that regulate wake-sleep cycles are described, along with how these are affected by different disease states and how those alterations lead to the clinical manifestations of those disorders. RECENT FINDINGS: The discovery of both sleep-promoting neurons in the ventrolateral preoptic nucleus and wake-promoting neurons, such as the lateral hypothalamic orexin (also called hypocretin) neurons, has allowed us to recognize that these two populations of neurons are mutually antagonistic (ie, inhibit each other) and form a "flip-flop switch," a type of circuit that results in rapid and complete transition in behavioral state...

Testosterone influences the brain via organizational and activational effects. Numerous relevant studies on rodents and a few on humans focusing on specific behavioral and cognitive parameters have been published. The results are, unfortunately, controversial and puzzling. Dosing, timing, even the application route seem to considerably affect the outcomes. In addition, the methods used for the assessment of psychometric parameters are a bit less than ideal regarding their validity and reproducibility. Metabolism of testosterone contributes to the complexity of its actions...

Wakefulness and vigilance levels are required for maintaining purposeful activities and motivated behaviours, which are often triggered by sensory information conveying external cues. An increasing body of work has suggested that orexins (also known as hypocretins)--a pair of neuropeptides that are crucial for maintaining wakefulness - are also involved in the regulation of motivated behaviours, including feeding, emotional behaviour and reward seeking, and that these functions are mediated by two subtypes of orexin receptors...

Recent studies have revealed the existence of hippocampal neurons that fire at successive moments in temporally structured experiences. Several studies have shown that such temporal coding is not attributable to external events, specific behaviours or spatial dimensions of an experience. Instead, these cells represent the flow of time in specific memories and have therefore been dubbed 'time cells'. The firing properties of time cells parallel those of hippocampal place cells; time cells thus provide an additional dimension that is integrated with spatial mapping...

The relationships between mirror neurons (MNs) and motor imitation, and its clinical implications in autism spectrum disorder (ASD) have been widely investigated; however, the literature remains—at least partially—controversial. In this review we support a multi-level action understanding model focusing on the mirror-based understanding. We review the functional role of the parieto-frontal MNs (PFMN) network claiming that PFMNs function cannot be limited to imitation nor can imitation be explained solely by the activity of PFMNs...

The presence of asymmetry in the human cerebral hemispheres is detectable at both the macroscopic and microscopic scales. The horizontal expansion of cortical surface during development (within individual brains), and across evolutionary time (between species), is largely due to the proliferation and spacing of the microscopic vertical columns of cells that form the cortex. In the asymmetric planum temporale (PT), minicolumn width asymmetry is associated with surface area asymmetry. Although the human minicolumn asymmetry is not large, it is estimated to account for a surface area asymmetry of approximately 9% of the region's size...

Recent investigations of non-human primate communication revealed vocal behaviors far more complex than previously appreciated. Understanding the neural basis of these communicative behaviors is important as it has the potential to reveal the basic underpinnings of the still more complex human speech. The latest work revealed vocalization-sensitive regions both within and beyond the traditional boundaries of the central auditory system. The importance and mechanisms of multi-sensory face-voice integration in vocal communication are also increasingly apparent...

Retinal bipolar cells are the first 'projection neurons' of the vertebrate visual system - all of the information needed for vision is relayed by this intraretinal connection. Each of the at least 13 distinct types of bipolar cells systematically transforms the photoreceptor input in a different way, thereby generating specific channels that encode stimulus properties, such as polarity, contrast, temporal profile and chromatic composition. As a result, bipolar cell output signals represent elementary 'building blocks' from which the microcircuits of the inner retina derive a feature-oriented description of the visual world...

How does our brain choose the best course of action? Choices between material goods are thought to be steered by neural value signals that encode the rewarding properties of the choice options. Social decisions, by contrast, are traditionally thought to rely on neural representations of the self and others. However, recent studies show that many types of social decisions may also involve neural value computations. This suggests a unified mechanism for motivational control of behaviour that may incorporate both social and non-social factors...

Light has profoundly influenced the evolution of life on earth. As widely appreciated, light enables us to generate images of our environment. However, light - through intrinsically photosensitive retinal ganglion cells (ipRGCs) - also influences behaviours that are essential for our health and quality of life but are independent of image formation. These include the synchronization of the circadian clock to the solar day, tracking of seasonal changes and the regulation of sleep. Irregular light environments lead to problems in circadian rhythms and sleep, which eventually cause mood and learning deficits...

A hallmark of human language is that we combine lexical building blocks retrieved from memory in endless new ways. This combinatorial aspect of language is referred to as unification. Here we focus on the neurobiological infrastructure for syntactic and semantic unification. Unification is characterized by a high-speed temporal profile including both prediction and integration of retrieved lexical elements. A meta-analysis of numerous neuroimaging studies reveals a clear dorsal/ventral gradient in both left inferior frontal cortex and left posterior temporal cortex, with dorsal foci for syntactic processing and ventral foci for semantic processing...

Under normal conditions, food intake and energy expenditure are balanced by a homeostatic system that maintains stability of body fat content over time. However, this homeostatic system can be overridden by the activation of 'emergency response circuits' that mediate feeding responses to emergent or stressful stimuli. Inhibition of these circuits is therefore permissive for normal energy homeostasis to occur, and their chronic activation can cause profound, even life-threatening, changes in body fat mass. This Review highlights how the interplay between homeostatic and emergency feeding circuits influences the biologically defended level of body weight under physiological and pathophysiological conditions...