Prefrontal Syndrome

The cerebral cortex directs functions like speech, behavior, reactions, movement, thinking, and learning. In fact, some research suggests that bipolar disorder originates with problems with the thalamus, which links sensory input to good and bad feelings. The hippocampus also affects depression. It, like the amygdala, is part of the limbic system. It is vital in processing long-term memory. This section of the brain registers recurring fear. In people with clinical depression, the hippocampus is much smaller. Research suggests, even, that ongoing exposure to stress impairs the growth of nerve cells in this part of the brain. One of the most important jobs of the brain is to process senses, through neurons. Neurotransmitters are specific substances that help relay information to the brain. Scientists have identified many neurotransmitters that affect depression. A lack or excess of the neurotransmitters acetylcholine, serotonin, norepinephrine, dopamine, glutamate, lithium carbonate and gamma-aminobutyric acid are thought to contribute to depression. Acetylcholine is involved in learning and enhances memory. Serotonin helps regulate sleep, appetite, and mood, and inhibits pain. Research shows the idea that many depressed people have reduced levels of serotonin. Low levels of a byproduct of serotonin have been linked to a high risk for suicide. Norepinephrine is a neurotransmitter which constricts blood vessels and raises blood pressure. An excess in

In Chapter 8 “Where the Wild Things Are,” the author Le Doux looked at the how our brain regions and systems functioned during the development of anxiety disorders. He introduced many researchers’ ideas and theories such as Pavlovian conditioning and instrumental conditioning; then, he listed the brain regions that were associated with anxiety and fear conditioning such as hippocampus, amygdala, sympathetic nervous system, and various brain cortexes. He also explained how our brain became conditioned for different anxiety disorders.

Among these different processes are encoding, storage, consolidation, and retrieval. This study hypothesized that the hippocampus plays a different role in each of these. The method of this study is especially unique because it used temporary chemical inactivation of the hippocampus, which had not been done before. This temporary inactivation is unique because it lets the researchers selectively assess the role of the hippocampus during each of the processes discussed above. To test encoding, the inactivation occurred during learning of a maze task; to test retrieval, inactivation occurred during a retention task. Results indicate the temporary inactivation of the hippocampus impairs both encoding and retrieval. To test long-term consolidation, rats were trained and then separate groups received hippocampal treatment for different amounts of time between one and five days. Results showed that temporary inactivation during this time period disrupts memory for the already learned task. This study partially supports the result of the study by Eldridge et al. (2000) in that they both show the hippocampus is necessary for memory retrieval. However, it does not address the retrieval of different types of memory. This study also supports the idea from Wang et al. (2012) that the hippocampus may be involved in consolidation and storage of new memories but not necessarily of older

Patricia Rakic Goldman’s work on mapping the prefrontal cortex was crucial for understanding the many mental disorders that we have today.

The temporal lobe consists of the hippocampal region as well as the the entorhinal, perirhinal and parahippocampal cortices which are important for long-term memory. The hippocampal region consists of the hippocampus proper, the dentate gyrus and the subicular complex. The entorhinal cortex receives most of its input from the perirhinal and parahippocampal cortices as well as inputs from the olfactory bulb, orbital frontal cortex, insular cortex, cingulate cortex and superior temporal gyrus (Squire & Zola,

In contrast to the control, the MCI group showed significant decreases of Cnodal in the hippocampus and the fusiform gyrus on the right side and in the dorsal medial prefrontal cortex on the left side (Fig.5). In this group, SAnodal increased in the postcentral gyrus and decreased in the superior frontal, middle frontal, and lingual and fusiform gyri on the right side and in the left middle occipital

The amygdala specializes in threat detection, fear, excitement, and arousal, hippocampus helps format long-term declarative memories and spatial reasoning. The anterior cingulate cortex influences autonomic function, decision making, error detection and emotion while the posterior has a role in spatial annotations memory. The septal area produces pleasurable feeling,

Since hippocampus plays an important function in the brain, it has become a great topic for many conducted research not only on human but also animals, specifically primates and rodents. In primate model of amnesia, the experiment is performed through three main tasks – delayed nonmatch to sample, object discrimination paradigm and motor skill learning across multiple trials (Eichenbaum et al, 1992). In delayed non-matching test, both amnesic and intact monkey show nearly same performance rate in remembering objects across delayed in short period of time (Eichenbaum et al, 1992). In contrast, amnesic monkeys show a great impairment for longer delayed conditions, hours, in picking the right non-matched samples (Eichenbaum et al, 1992). Likewise, in object discrimination task, amnesic monkeys are unable to recognize objects, as compared to control monkeys (Eichenbaum et al, 1992).These tests suggest the importance of hippocampus in acquisition of new information and recollection old events from episodic memory. Additionally, hippocampus also contributes largely to relational representation, as a characteristic of declarative memory (Eichenbaum et al, 1992). This can be shown through odor discrimination and place

(Parkin, 1996). In addition, hippocampus is part of the limbic system in the brain that is shape like a seahorse and is located within in the temporal lobes. The hippocampus is involved in memory forming, organizing, and storing (Bailey). Moreover, “The hippocampus acts as a memory indexer by sending memories out to the appropriate part of the cerebral hemisphere for long-term storage and retrieving them when necessary” (Bailey). Furthermore, the afferent and efferent of the hippocampus are packed together and goes the same way. According to an article from University of Texas Medical

Chow, T. W., & Cummings, J. L. (2000). The amygdala and Alzheimer’s disease. In J. P. Aggleton (Ed.), The amygdala: A functional analysis (pp. 656–680). Oxford, England: Oxford University Press.

2) Jason R. Tregellas, Ph.D. Jason Smucny, M.S. Josette G. Harris, Ph.D. Ann Olincy, M.D. Keeran Maharajh,Ph.D. Eugene Kronberg, Ph.D. Lindsay C. Eichman, B.S. Emma Lyons, B.S. Robert Freedman, M.D, (Published: Nov 12th , 2013). Intrinsic Hippocampal Activity as a Biomarker for Cognition and Symptoms in Schizophrenia. The American Journal of Psychiatry, 549-554.

Also, the studies by Wender et al, suggest “there are differences found in brain structure which can be related to mental disorders” (1986). When studies were conducted the chemical makeup of the brain has scientifically lead to successful drug treatments including Prozac used to treat depression. This, however, is disputed

Previous research has also identificated anterior insula and dorsal anterior cingulate cortex as a frontoparietal control network, that may indirectly contribute to episodic memory recall such as goal-directed selection for stimulus and responses and may mediate these functions by integrating information from external and internal sources or across multiple domains such as attention or working memory

The assortment of appropriate goal objects and the action to be executed depends on the perceptual apparatus of the ventral system. A remaining question that is yet to be answered is how the two streams interrelate with each other and how the other brain regions construct purposive behavior (Goodale & Servos, 1995). Nevertheless, at the height of visual processing, the visuomotor modules in the parietal lobe function alone from the occipitotemporal area which produces perception-based knowledge. The perceptual system can provide proper information for our thought processes to act upon. In comparison, the other is designed to guide actions purely in the ‘here and now’, and its products are consequently useless for later reference (Goodale & Servos, 1995). In other words, it is through knowledge expanding through the ventral stream that we can practice insight, hindsight, and foresight regarding the visual world. The visuomotor system can give blind sight, but in doing this may offer no direct contribution to our mental life (Weiskrantz, 1997).