Dorsolateral Prefrontal Cortex

Question: Discuss about the Dorsolateral Prefrontal Cortex. Answer: Introduction Dorsolateral prefrontal cortex (DLPFC) performs an important role in the brain and serves as the central site of the cognitive control in both humans and non-human primates. It is a region found in the prefrontal cortex of the human and monkey brain. The DLPFC does not majorly present as an anatomical structure but rather as one that has functional properties. (Baddeley, 2013) It majorly occupies the frontal, middle gyrus in humans while in macaque monkeys, it lies around the principal sulcus. The DLPFC has connections with the basal ganglia, parts of the orbitofrontal cortex, hippocampus, as well as the thalamus. It also serves as the endpoint for the stream of the dorsal pathway. As the DLPFC consist of spatial selective nerve neurons, it encompasses the sub-functions needed to carry out integrated responses through its neural circuitry. These functions include sensory input, signaling of motor nerves and short term memory. (Baddeley, 2013) An essential aspect of the DLPFC is the functional executive roles it provides such as the working memory, planning, abstract reasoning and cognitive flexibility. The value of DLPFC to the working memory was reinforced by studies that used adult macaques. It was shown that lesions that diminished DLPFC disturbed the macaques performance regarding the A-not-B response that was delayed while other brain part lesions did not impair their task performance. (Fuster, 2015) The DLPFC is also implicated in moral and risky decision-making process. An example is when DLPFC is activated when individuals have to make moral decisions for instance when they have to distribute resources that are limited. DLPFC possess clinical significance in conditions that are mental and psychological. An example is in schizophrenia where the condition is attributed to the insufficient or lack of activity in the frontal lobe. It has been seen that the DLPFC is less active if a person has chronic schizophrenia. (Zuffante, 2013) Concerning depression, DLPFC has ties to the ventromedial prefrontal cortex which is involved at the emotional level during the suppression stage. Damage to the DLPFC has been linked to exposure to severe stress. When stress impact on a person, their neural activity is seen to reduce the working memory that is correlated to activity in the DLPFC. These findings suggest that DLPFC not only plays a role to stress but also in psychiatry disorders. Studies and researches supporting and against the statement Studies and researchers have postulated an architectural segregation between components, through the dominant cognitive theory, that is responsible for the maintenance of short-term information and is responsible for coordination and control of the specified information. Strong evidence has been produced by the cognitive neuroscience revealing that prefrontal cortex (PFC) works like a neural substrate of working memory (WM). A theory implemented as connectionist computational model attempts to resolve the conflict as to whether PFC should be regarded as a storage component or a control one. Simulation studies have also been used to demonstrate that the models may show a wide range of behavioral information that can be associated with task paradigms that differentiate the storage and control working memory functions. Neurological studies have been presented that help to examine the predictions of the models concerning the role PFC play in the context processing. This theories and mode ls provide new perspectives on the control and storage relationship in WM and also the function of PFC in the service of these roles. (Uylings, 2012) Much excitement in the study of WM can be followed by the contributions of researchers such as Alan Baddeley, who outlined experimental and theoretical studies concerning this area that had a long last and widespread reputation on the field. A dominant model has come across by the theoretical account concerning the architecture of WM put forth by Baddeley and colleagues. In this model, there exists two domain specific buffer systems which are the visuospatial scratchpad and the phonological loop whose coordinated action is influenced by a primary control structure that is titled as the central executive. The main aspect of the model is that the control and storage processes are architecturally segregated and distinct but are also included under the heading of the WM. These distinctions between working memory within the theoretical aspect of Baddeley model have attracted psychologists who studied the properties of and functional divisions between the cognitive buffer systems. This stu dy was done without the feeling to need to understand the vaguely described characteristics of the central executive. In parallel, the cognitive neurology scientists have had the attraction to discover the neural substrates that are stipulated in each element within the model. (Baddeley, 2013) In cognitive neuroscience, the research and studies of WM concerning the prefrontal cortex (PFC) have been more of a subject of focus. In the studies conducted on neuropsychological clients, the PFC has been pointed out as the brain region that is implicated in behavioral and cognitive regulation. It is therefore not unusual that many researchers have identified the PFC as the principal component in the executive Baddeley's model. (Baddeley, 2013) It is in conjunction to this that a prominent neuropsychological theory has been put forward by Shallice and colleagues describing PFC as a system of supervisory attention that controls roles and functions specifically attached to the central executive. (Shallice, 2015) However, this perspective on the neuropsychological presentation holds in contrast with various studies emerging out of the literature on animals on the function of the PFC. In some report, PFC has been found to be critically connected to the active maintenance of short-term information. Researchers such as Goldman-Rakic have claimed that PFC activity in the neural system may serve as the cellular component of the WM. Thus, considerable controversy has been brought about by the search for the neural substrate of the WM which is within the cognitive neuroscience. (Goodkind, 2012) In recent studies, there has been an attempt to resolve controversies concerning the control or storage functions of PFC in the WM. This attempt has been through newly developed functional neuroimaging techniques. Various investigators arguing from the vast analysis of the WM neuroimaging studies have demonstrated that there exists an anatomical segregation occurring in the lateral PFC. It has therefore been insinuated that ventral regions of PFC are connected directly in functions of active maintenance, ventral and dorsal PFC regions, on the other hand, are involved with the aspects of control and not storage of WM. (Krawczyk, Michelle McClelland, Donovan, 2012) Some researchers have supported the role of PFC in WM from the perspective that it is developed through a mechanistically explicit computational approach that relies on principles of a neural network framework. These principles are those of the neural processing of information and are associated with the connectionist model. The model subserves a computational function in which PFC is involved in the representing and maintaining context data and information. Other studies describe computer simulations that focus on the model to outline a description of the role PFC has in the particular behavioral task which investigates both the control and storage functions of the WM. The task is known as the AX-CPT. (Krawczyk, Michelle McClelland, Donovan, 2012) Functional neuroimaging studies may also be used to test the aspects of the design model. The conclusions of these studies have supported the assertion that dorsolateral PFC is mainly included in the active maintaining of the context data and information in WM, and that the knowledge is critical in the regulation of behavior. Some studies have brought evidence against the view on the function of PFC in the working memory. Some of the first evidence has been seen to originate from the neuroimaging studies in humans. Researchers posit that the lag in period activity in PFC did not decode and encode data that is precise to the stimuli being portrayed in the WM. In addition to the imaging examinations evidence, it has been seen that PFC lesions do not always undermine the storage in WM. This has been evidenced by the case that clients with considerable lesions that were confined in the lateral PFC had revealed fewer deficits in the verbal and memory span or either in the delayed recognition. A result similar to that was observed in monkeys which had lesions and tumors of the ventral PFC. (Coubard, 2015) Until recently, there had no sufficient electrophysiological evidence to support the views until Lebedev trained monkeys on how to maintain a specific spatial location in WM while at the same time served to a different location that would make a saccade to the identified location concerning the go cue. (Monsell, Driver, 2014) They found two neurons population which demonstrated that PFC neurons could play diverse roles in the WM tasks that are not strictly maintained per se. Another evidence comes from current work in which the studies used multivariate patterns in the review of recorded data during a prolonged paired associate performance of a task. This information has therefore shown that PFC does not keep the information stimulus in the WM per se, though it accesses the information and can encode it whether the stimulus in the subsequent data is a target or a distractor. Although the neuron system that is responsible for the WM is shown to include various regions of the brain, there exists ample evidence from the lesion and neurophysiological studies done on primates to prove that the PFC is a critical component. The new studies in brain imaging using positron emission tomography (PET) and functional magnetic resonance imaging (fMRI), have shown to support the implication of the PFC in WM. However, there remains some doubts and questions on the practical organization of the human PFC and its use in the WM. Transient versus sustained activity in the human PFC has shown evidence by the brain imaging studies that differentiate temporary, perception related activities to those that are sustained and memory related. It is also important to take account of the temporal active resolution from the fMRI to establish the functional purposes of prefrontal areas and posterior process activity in the WM. (Monsell, Driver, 2014) The domain specificity in an individual's human frontal cortex through object segregation versus spatial processing has increased the evidence proving that DLPFC stores memory. Goldman and colleagues showed that that the dorsal prefrontal areas show sustained activity delay that is essentially associated with the spatial information. The distributed neural systems have also revealed the relationship between the posterior visual processing areas to that of the frontal WM. This has been influenced by the advantage of the functional brain imaging which can obtain simultaneous measures of the brain activities hence allowing observations across the whole neural systems. (Diamond, Goldman-Rakic, 2012) What future research should focus on? Although the results from the various studies conducted seem to line up well with the previous imaging studies, the precise mechanisms that are responsible for the increase in effective connectivity remain unknown. The evolution of neural activity in the posterior targets is also not well postulated. Therefore, the future research should the study on the neurophysiological level where evidence on the changes in neural activity when problem-solving tasks are initiated in addition to nonspatial cues. The relationship on how prefrontal and posterior areas in the brain synchronize as behavior changes will be exhibited. (Milham, 2012) Since Goldman-Rakic focused on a spatial task, future research should include a logical continuation to study these processes in non-human primates with the use of different stimuli and different stimulus modalities. These experiments, therefore, provide a building block for such future studies. (Diamond, Goldman-Rakic, 2012) More work is required in future research to shed light on the character of the interaction between PFC and the WM to the sensory areas. Therefore, future use of recent large scale recording and analyzing techniques will prove to be of importance. This method will provide the potential to allow tracing of data and information from the WM to the PFC and goes back again during the manifestations of WM tasks. (Luk, 2012) Conclusion The role of DLPFC has been seen at first to be involved in a wide collection of processes. Varied behaviors are affected by damage, and different tasks seem to initiate it. In the real sense, the solution to a unified role in the cognitive ability of the DLPFC may be due to its connectivity with other regions. The fMRI has importantly revealed its unique capability to image many areas of the brain simultaneously. Therefore, it has demonstrated to have a touted potential which characterizes interactions between networks in neutral nodes and those that support WM. Although different nodes have roles that are different, they together sustain relevant representations that can be used in the selection of behaviors. A good understanding of the neural mechanism involved in WM is vital in gaining insight into the various goal-directed behaviors that are supported by the WM. The perspective on WM that emphasizes the encoding of WM information on the notion of distributed population activity is widely supported. Methodological advances in the past years have highlighted the high dimensional nature of Lateral prefrontal cortex (LPFC) activity and the lighted sensory nature of the manifested WM information. It is suggested that LPFC activity presents as a top-down influence on sensory areas contrary to its imputed storage buffer role. The conceptualization of LPFC supports models explaining the functions of the hippocampus which proposes that it stores pointers that can reactivate than store the cortical memory themselves. Future work should, therefore, prioritize efforts to specify the role lateral prefrontal cortex plays in working memory as well as the functional activities involved in the interactions between the LPFC, regions of the sensory area and other parts involved in WM. In areas for future research, a complete understanding of the implementation of WM in the brain will require new insights on how incoming sensory input affects the sustained representations in the sensory cortex. Therefore, an emphasis on the outlined representations which occurs through the increased mechanisms of neural activities will encourage the inclusion of these officiated mechanisms into the general theory of WM. This emphasis will encourage revisiting and further review of the studies involving the persistent role of the prefrontal cortex during working memory. References Baddeley, A. (2013). Working memory and language: an overview. 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