The striatum, or corpus striatum, is a nucleus in the subcortical basal ganglia of the forebrain. The striatum is a critical component of the motor and reward systems; receives glutamatergic and dopaminergic inputs from different sources; and serves as the primary input to the rest of the basal ganglia.
The basal ganglia (BG), or basal nuclei, are a group of subcortical nuclei found in the brains of vertebrates. In humans and some primates, differences exist, primarily in the division of the globus pallidus into external and internal regions, and in the division of the striatum. Positioned at the base of the forebrain and the top of the midbrain, they have strong connections with the cerebral cortex, thalamus, brainstem and other brain areas. The basal ganglia are associated with a variety of functions, including regulating voluntary motor movements, procedural learning, habit formation, conditional learning, eye movements, cognition, and emotion.
Anhedonia is a diverse array of deficits in hedonic function, including reduced motivation or ability to experience pleasure. While earlier definitions emphasized the inability to experience pleasure, anhedonia is currently used by researchers to refer to reduced motivation, reduced anticipatory pleasure (wanting), reduced consummatory pleasure (liking), and deficits in reinforcement learning. In the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5), anhedonia is a component of depressive disorders, substance-related disorders, psychotic disorders, and personality disorders, where it is defined by either a reduced ability to experience pleasure, or a diminished interest in engaging in pleasurable activities. While the International Statistical Classification of Diseases and Related Health Problems, Tenth Revision (ICD-10) does not explicitly mention anhedonia, the depressive symptom analogous to anhedonia as described in the DSM-5 is a loss of interest or pleasure.
The mesolimbic pathway, sometimes referred to as the reward pathway, is a dopaminergic pathway in the brain. The pathway connects the ventral tegmental area in the midbrain to the ventral striatum of the basal ganglia in the forebrain. The ventral striatum includes the nucleus accumbens and the olfactory tubercle.
The cingulate cortex is a part of the brain situated in the medial aspect of the cerebral cortex. The cingulate cortex includes the entire cingulate gyrus, which lies immediately above the corpus callosum, and the continuation of this in the cingulate sulcus. The cingulate cortex is usually considered part of the limbic lobe.
In the human brain, the anterior cingulate cortex (ACC) is the frontal part of the cingulate cortex that resembles a "collar" surrounding the frontal part of the corpus callosum. It consists of Brodmann areas 24, 32, and 33.
Dopaminergic pathways in the human brain are involved in both physiological and behavioral processes including movement, cognition, executive functions, reward, motivation, and neuroendocrine control. Each pathway is a set of projection neurons, consisting of individual dopaminergic neurons.
In cognitive science and neuropsychology, executive functions are a set of cognitive processes that are necessary for the cognitive control of behavior: selecting and successfully monitoring behaviors that facilitate the attainment of chosen goals. Executive functions include basic cognitive processes such as attentional control, cognitive inhibition, inhibitory control, working memory, and cognitive flexibility. Higher-order executive functions require the simultaneous use of multiple basic executive functions and include planning and fluid intelligence.
The orbitofrontal cortex (OFC) is a prefrontal cortex region in the frontal lobes of the brain which is involved in the cognitive process of decision-making. In non-human primates it consists of the association cortex areas Brodmann area 11, 12 and 13; in humans it consists of Brodmann area 10, 11 and 47.
The reward system is a group of neural structures responsible for incentive salience, associative learning, and positively-valenced emotions, particularly ones involving pleasure as a core component. Reward is the attractive and motivational property of a stimulus that induces appetitive behavior, also known as approach behavior, and consummatory behavior. A rewarding stimulus has been described as "any stimulus, object, event, activity, or situation that has the potential to make us approach and consume it is by definition a reward". In operant conditioning, rewarding stimuli function as positive reinforcers; however, the converse statement also holds true: positive reinforcers are rewarding.
The ventromedial prefrontal cortex (vmPFC) is a part of the prefrontal cortex in the mammalian brain. The ventral medial prefrontal is located in the frontal lobe at the bottom of the cerebral hemispheres and is implicated in the processing of risk and fear, as it is critical in the regulation of amygdala activity in humans. It also plays a role in the inhibition of emotional responses, and in the process of decision-making and self-control. It is also involved in the cognitive evaluation of morality.
The dorsolateral prefrontal cortex is an area in the prefrontal cortex of the primate brain. It is one of the most recently derived parts of the human brain. It undergoes a prolonged period of maturation which lasts into adulthood. The DLPFC is not an anatomical structure, but rather a functional one. It lies in the middle frontal gyrus of humans. In macaque monkeys, it is around the principal sulcus. Other sources consider that DLPFC is attributed anatomically to BA 9 and 46 and BA 8, 9 and 10.
Scientific studies have found that different brain areas show altered activity in humans with major depressive disorder (MDD), and this has encouraged advocates of various theories that seek to identify a biochemical origin of the disease, as opposed to theories that emphasize psychological or situational causes. Factors spanning these causative groups include nutritional deficiencies in magnesium, vitamin D, and tryptophan with situational origin but biological impact. Several theories concerning the biologically based cause of depression have been suggested over the years, including theories revolving around monoamine neurotransmitters, neuroplasticity, neurogenesis, inflammation and the circadian rhythm. Physical illnesses, including hypothyroidism and mitochondrial disease, can also trigger depressive symptoms.
The biology of obsessive–compulsive disorder (OCD) refers biologically based theories about the mechanism of OCD. Cognitive models generally fall into the category of executive dysfunction or modulatory control. Neuroanatomically, functional and structural neuroimaging studies implicate the prefrontal cortex (PFC), basal ganglia (BG), insula, and posterior cingulate cortex (PCC). Genetic and neurochemical studies implicate glutamate and monoamine neurotransmitters, especially serotonin and dopamine.
Mindfulness has been defined in modern psychological terms as "paying attention to relevant aspects of experience in a nonjudgmental manner", and maintaining attention on present moment experience with an attitude of openness and acceptance. Meditation is a platform used to achieve mindfulness. Both practices, mindfulness and meditation, have been "directly inspired from the Buddhist tradition" and have been widely promoted by Jon Kabat-Zinn. Mindfulness meditation has been shown to have a positive impact on several psychiatric problems such as depression and therefore has formed the basis of mindfulness programs such as mindfulness-based cognitive therapy, mindfulness-based stress reduction and mindfulness-based pain management. The applications of mindfulness meditation are well established, however the mechanisms that underlie this practice are yet to be fully understood. Many tests and studies on soldiers with PTSD have shown tremendous positive results in decreasing stress levels and being able to cope with problems of the past, paving the way for more tests and studies to normalize and accept mindful based meditation and research, not only for soldiers with PTSD, but numerous mental inabilities or disabilities.
The cortico-basal ganglia-thalamo-cortical loop is a system of neural circuits in the brain. The loop involves connections between the cortex, the basal ganglia, the thalamus, and back to the cortex. It is of particular relevance to hyperkinetic and hypokinetic movement disorders, such as Parkinson's disease and Huntington's disease, as well as to mental disorders of control, such as attention deficit hyperactivity disorder (ADHD), obsessive–compulsive disorder (OCD), and Tourette syndrome.
Neuromorality is an emerging field of neuroscience that studies the connection between morality and neuronal function. Scientists use fMRI and psychological assessment together to investigate the neural basis of moral cognition and behavior. Evidence shows that the central hub of morality is the prefrontal cortex guiding activity to other nodes of the neuromoral network. A spectrum of functional characteristics within this network to give rise to both altruistic and psychopathological behavior. Evidence from the investigation of neuromorality has applications in both clinical neuropsychiatry and forensic neuropsychiatry.
The salience network (SN), also known anatomically as the midcingulo-insular network (M-CIN) or ventral attention network, is a large scale network of the human brain that is primarily composed of the anterior insula (AI) and dorsal anterior cingulate cortex (dACC). It is involved in detecting and filtering salient stimuli, as well as in recruiting relevant functional networks. Together with its interconnected brain networks, the SN contributes to a variety of complex functions, including communication, social behavior, and self-awareness through the integration of sensory, emotional, and cognitive information.
Bipolar disorder is an affective disorder characterized by periods of elevated and depressed mood. The cause and mechanism of bipolar disorder is not yet known, and the study of its biological origins is ongoing. Although no single gene causes the disorder, a number of genes are linked to increase risk of the disorder, and various gene environment interactions may play a role in predisposing individuals to developing bipolar disorder. Neuroimaging and postmortem studies have found abnormalities in a variety of brain regions, and most commonly implicated regions include the ventral prefrontal cortex and amygdala. Dysfunction in emotional circuits located in these regions have been hypothesized as a mechanism for bipolar disorder. A number of lines of evidence suggests abnormalities in neurotransmission, intracellular signalling, and cellular functioning as possibly playing a role in bipolar disorder.
Joni Wallis is a cognitive neurophysiologist and Professor in the Department of Psychology at the University of California, Berkeley.
