Treatment for Addiction & Psychiatric Disorders



The Neuroanatomy of the Brain

and

the Functions of each Lobe

The cerebrum (cortex) is divided into 6 lobes:

1. Frontal lobe—conscious thought; the most uniquely human of all the brain structures.

2. Limbic lobe—emotion, memory

3. Parietal lobe—integrates sensory information; manipulation of objects; visuospatial processing

4. Occipital lobe—sense of sight

5. Temporal lobe—senses of smell and sound; process complex stimuli like faces/scenes.

6. Insular cortex—pain, some other senses.

_____________________________________________________________________________________

[pic] [pic]

_____________________________________________________________________________________

Limbic System

The limbic system is involved in motivation, emotion, learning, and memory. It operates by influencing the endocrine system and the autonomic nervous system. The hypothalamus, the amygdala, the nucleus accumbens, and the hippocampus are part of the limbic system. The limbic system is a group of forebrain structures, located beneath the cortex and on both sides of the thalamus where the subcortical structures meet the cortex.

This system is important because it controls some behaviors that are essential to the life of all mammals such as finding food and self-preservation. In humans, the limbic system is more involved in motivation and emotional behaviors.

[pic]

The limbic system supports a variety of functions, including emotion, behavior, motivation, long-term memory, and olfaction.[3] It appears to be primarily responsible for emotional life, and it has a great deal to do with the formation of memories.

The amygdala and the hippocampus seem to be the main areas involved with emotions. Their connection with the thalamus enables it to play an important role in the mediation and control of major activities like friendship, love and affection, and on the expression of mood.

The amygdala is involved in signaling the cortex of motivationally significant stimuli such as those related to reward and fear in addition to social functions such as mating. The amygdalae stimulate the hippocampus to remember many details surrounding the situation, as well.

The amygdala is believed to play a senior role in coordinating unconscious emotional states. Noteworthy is its connection with the autonomic nervous system autonomic nervous system: see nervous system.

[pic]

autonomic nervous system

Part of the nervous system that is not under conscious control and that regulates the internal organs. It includes the sympathetic, parasympathetic, and enteric nervous systems.

..... Click the link for more information.. Physiological responses to stressful emotional experiences like 'fight or flight' are largely orchestrated by the amygdala. In addition, because it is linked to the prefrontal cortex, it has a hand in the conscious awareness of emotion. One consequence of these connections is that spiritual experiences are both channeled and interpreted with assistance from the amygdala.

The hippocampus is involved in various processes of cognition such as cognitive maps for navigation and spatial memory. It converts things that are “on one's mind” at the moment (in short-term memory) into long-term memory. The dorsal hippocampus was found to be an important component for the generation of new neurons, called adult-born granules (GC), in adolescence and adulthood. The hippocampus has a huge impact in learning through mental and physical training resulting in this neurogenesis.

The limbic system is highly interconnected with the nucleus accumbens, the brain's pleasure center, which plays a role in sexual arousal and the "high" derived from "recreational" drugs. These responses are heavily modulated by dopaminergic projections from the limbic system. The nucleus accumbens role in pleasure also includes laughter, reward, and reinforcement learning, as well as fear, aggression, impulsivity, addiction, and the placebo effect. It is located in the basal forebrain.

The activation of dopamine in the nucleus accumbens is central to "wanting". Dopamine release in the accumbens occurs in anticipation of reward, and facilitates many kinds of approach and goal-oriented behaviors like exploration, affiliation, aggression, sexual behavior, and food hoarding. Lesions to the nucleus accumbens reduce the motivation to work for reward.

The levels of dopamine in the extracellular fluid of the nucleus accumbens increases with the use of cocaine, heroin, nicotine, or alcohol. This increase in dopamine is believed to be responsible for the reinforcing effects that later stimulate drug-taking behavior. Environmental cues (e.g. triggers such as talking about the high from using) associated with addictive drugs releases dopamine in the nucleus accumbens.

In 1954, Olds and Milner found that rats with metal electrodes implanted into their nucleus accumbens repeatedly pressed a lever activating this region. They would do this in preference to eating and drinking, eventually dying of exhaustion.

The nucleus accumbens has been targeted by stereotactic surgery for ablation as a treatment in China for alcoholism. Prior to the fall of communism in the USSR, the treatment of addiction was also considered to be surgical.

The nucleus accumbens plays an equal role in processing many rewards such as food and sex. The nucleus accumbens is selectively activated during the perception of pleasant, emotionally arousing pictures and during mental imagery of pleasant, emotional scenes. This is part of the mechanism involved with cravings.

A 2005 study found that it is involved in the regulation of emotions induced by music,] perhaps consequent to its role in mediating dopamine release. The nucleus accumbens plays a role in rhythmic timing and is considered to be of central importance to the limbic-motor interface.

Levels of dopamine increase in the nucleus accumbens during maternal behavior, while lesions in this area upset maternal behavior.[18] When human mothers are presented pictures of their children, functional MRI's show an increased brain activity in the nucleus accumbens and other reinforcing brain regions and a decrease in activity in areas of the brain involved with negative emotions.

In April 2007, two research teams reported on having inserted electrodes into the nucleus accumbens in order to use deep brain stimulation to treat severe depression.[19] In 2010 experiments reported that deep brain stimulation of the nucleus accumbens was successful in decreasing depression symptoms in 50% of patients who did not respond to other treatments such as electroconvulsive therapy.

The limbic system is also tightly connected to the prefrontal cortex. Some scientists contend that this connection is related to the pleasure obtained from solving problems. To cure severe emotional disorders, this connection was sometimes surgically severed, a procedure of psychosurgery, called a prefrontal lobotomy (this is actually a misnomer). Patients having undergone this procedure often became passive and lacked all motivation.

Paul D. MacLean, as part of his triune brain theory, hypothesized that the limbic system is older than other parts of the fore-brain, and that it developed to manage fight or flight circuitry, which is an evolutionary necessity for reptiles as well as humans. He believed that the brain stem was the most primitive (reptilian), the limbic system evolved next (mammalian), then the cortex (human).

Parietal Lobe

The parietal lobe integrates sensory information from different modalities, particularly determining spatial sense and navigation. Damage to the right hemisphere of this lobe results in the loss of imagery, visualization of spatial relationships and neglect of left-side space and left side of the body.

Frontal Lobe

The executive functions of the frontal lobes involve the ability to recognize future consequences resulting from current actions, to choose between good and bad actions (or better and best), override and suppress socially unacceptable responses, and determine similarities and differences between things or events.

Your personality lives in the frontal lobes, where emotions, problem solving, reasoning, planning and other functions are managed. The frontal lobes are linked to sensory and memory centers throughout the brain. Their primary job is to allow us to think things through and determine how to use information that is located elsewhere in the brain.

Higher-level thinking is supported by the frontal lobes. Activity in these lobes allows us to reason, make judgments, make plans for the near and far future, make choices, take action, solve problems and generally control our living environment. Without fully functioning frontal lobes, you may have intelligence, but you wouldn’t be able to put it to use.

The frontal lobes or, more specifically, the prefrontal cortex located within the frontal lobes, possess the ability to access information and memories we accumulate that remind us how to communicate and interact appropriately in social or public situations. The frontal lobes are responsible for empathetic behavior, allowing us to understand the thinking and experiences of others. This understanding helps us take cues as to how to behave or respond in different types of social situations, such as the correct response to a job interview question, or understand the punch line of a joke. Damage to some areas of the frontal lobe can also affect sexual interest and activity.

The frontal lobes also play an important part in retaining longer term memories which are not task-based. These are often memories associated with emotions derived from the limbic system. The frontal lobe reaches full maturity at ~25 years old, marking the cognitive maturity associated with adulthood.

Giedd, Jay N.; Blumenthal, J; Jeffries, NO; Castellanos, FX; Liu, H; Zijdenbos, A; Paus, T; Evans, AC et al. (October 1999). "Brain Development during childhood and adolescence: a longitudinal MRI study". Nature Neuroscience 2 (10): 861–863. doi:10.1038/13158. PMID 10491603.  |displayauthors= suggested (help)

The frontal lobe contains most of the dopamine-sensitive neurons in the cerebral cortex. The dopamine system is associated with reward, attention, short-term memory tasks, planning, and motivation. Dopamine tends to limit and select sensory information arriving from the thalamus to the fore-brain.

____________________________________________________________________________________

................
................

In order to avoid copyright disputes, this page is only a partial summary.

Google Online Preview   Download