Executive function The original studies of
Fuster and of
Goldman-Rakic emphasized the fundamental ability of the prefrontal cortex to represent information not currently in the environment, and the central role of this function in creating the "mental sketch pad". Goldman-Rakic spoke of how this representational knowledge was used to intelligently guide thought, action, and emotion, including the inhibition of inappropriate thoughts, distractions, actions, and feelings. In this way, working memory can be seen as fundamental to attention and behavioral inhibition. Fuster speaks of how this prefrontal ability allows the integration of past and future, allowing both cross-temporal and cross-modal associations in the creation of goal-directed, perception-action cycles. This ability to represent underlies all other higher executive functions. The prefrontal cortex is responsible for many executive functions, such as remembering information, cognitive flexibility, and inhibitory control. Although the prefrontal cortex does this, it does not carry out these responsibilities alone as other brain regions also play important roles during this. For example, the amygdala sends signals to the prefrontal cortex area known as 46d in order for one to comprehend the situation and to determine how to react. Shimamura proposed Dynamic Filtering Theory to describe the role of the prefrontal cortex in
executive functions. The prefrontal cortex is presumed to act as a high-level gating or filtering mechanism that enhances goal-directed activations and inhibits irrelevant activations. This filtering mechanism enables executive control at various levels of processing, including selecting, maintaining, updating, and rerouting activations. It has also been used to explain emotional regulation. Miller and Cohen proposed an Integrative Theory of Prefrontal Cortex Function, that arises from the original work of Goldman-Rakic and Fuster. The two theorize that "cognitive control stems from the active maintenance of patterns of activity in the prefrontal cortex that represents goals and means to achieve them. They provide bias signals to other brain structures whose net effect is to guide the flow of activity along neural pathways that establish the proper mappings between inputs, internal states, and outputs needed to perform a given task". In essence, the two theorize that the prefrontal cortex guides the inputs and connections, which allows for cognitive control of our actions. The prefrontal cortex is of significant importance when
top-down processing is needed. Top-down processing by definition is when behavior is guided by internal states or intentions. According to the two, "The PFC is critical in situations when the mappings between sensory inputs, thoughts, and actions either are weakly established relative to other existing ones or are rapidly changing". When analyzing and thinking about attributes of other individuals, the medial prefrontal cortex is activated, however, it is not activated when contemplating the characteristics of inanimate objects. Studies using fMRI have shown that the medial prefrontal cortex (mPFC), specifically the anterior medial prefrontal cortex (amPFC), may modulate mimicry behavior. Neuroscientists are suggesting that social priming influences activity and processing in the amPFC, and that this area of the prefrontal cortex modulates mimicry responses and behavior. As of recent, researchers have used neuroimaging techniques to find that along with the
basal ganglia, the prefrontal cortex is involved with learning exemplars, which is part of the
exemplar theory, one of the three main ways our mind categorizes things. The exemplar theory states that we categorize judgements by comparing it to a similar past experience within our stored memories. A 2014 meta-analysis by Professor Nicole P.Yuan from the University of Arizona found that larger prefrontal cortex volume and greater PFC cortical thickness were associated with better executive performance.
Attention and memory from representation of
spatial memory in prefrontal cortex A widely accepted theory regarding the function of the brain's prefrontal cortex is that it serves as a store of
short-term memory. This idea was first formulated by Jacobsen, who reported in 1936 that damage to the primate prefrontal cortex caused short-term memory deficits.
Karl Pribram and colleagues (1952) identified the part of the prefrontal cortex responsible for this deficit as
area 46, also known as the
dorsolateral prefrontal cortex (dlPFC). More recently,
Goldman-Rakic and colleagues (1993) evoked short-term memory loss in localized regions of space by temporary inactivation of portions of the dlPFC. Once the concept of
working memory (see also
Baddeley's model of working memory) was established in contemporary neuroscience by
Alan Baddeley (1986), these neuropsychological findings contributed to the theory that the prefrontal cortex implements working memory and, in some extreme formulations, only working memory. In the 1990s this theory developed a wide following, and it became the predominant theory of PF function, especially for nonhuman primates. The concept of working memory used by proponents of this theory focused mostly on the short-term maintenance of information, and rather less on the manipulation or monitoring of such information or on the use of that information for decisions. Consistent with the idea that the prefrontal cortex functions predominantly in maintenance memory, delay-period activity in the PF has often been interpreted as a memory trace. (The phrase "delay-period activity" applies to neuronal activity that follows the transient presentation of an instruction cue and persists until a subsequent "go" or "trigger" signal.) To explore alternative interpretations of delay-period activity in the prefrontal cortex, Lebedev et al. (2004) investigated the discharge rates of single prefrontal neurons as monkeys attended to a stimulus marking one location while remembering a different, unmarked location.
Speech production and language Various areas of the prefrontal cortex have been implicated in a multitude of critical functions regarding speech production, language comprehension, and response planning before speaking. Cognitive neuroscience has shown that the left ventrolateral prefrontal cortex is vital in the processing of words and sentences. The right prefrontal cortex has been found to be responsible for coordinating the retrieval of explicit memory for use in speech, whereas the deactivation of the left is responsible for mediating implicit memory retrieval to be used in verb generation. Recollection of nouns (explicit memory) is impaired in some amnesic patients with damaged right prefrontal cortices, but verb generation remains intact because of its reliance on left prefrontal deactivation. Many researchers now include BA45 in the prefrontal cortex because together with BA44 it makes up an area of the frontal lobe called
Broca's area. Broca's Area is widely considered the output area of the language production pathway in the brain (as opposed to
Wernicke's area in the medial temporal lobe, which is seen as the language input area). BA45 has been shown to be implicated for the retrieval of relevant semantic knowledge to be used in conversation/speech. The right lateral prefrontal cortex (RLPFC) is implicated in the planning of complex behavior, and together with bilateral BA45, they act to maintain focus and coherence during speech production. However, left BA45 has been shown to be activated significantly while maintaining speech coherence in young people. Older people have been shown to recruit the right BA45 more so than their younger counterparts. This aligns with the evidence of decreased lateralization in other brain systems during aging. In addition, this increase in BA45 and RLPFC activity in combination of BA47 in older patients has been shown to contribute to "off-topic utterances." The BA47 area in the prefrontal cortex is implicated in "stimulus-driven" retrieval of less-salient knowledge than is required to contribute to a conversation. In other words, elevated activation of the BA47 together with altered activity in BA45 and the broader RLPFC has been shown to contribute to the inclusion of less relevant information and irrelevant tangential conversational speech patterns in older subjects. ==Clinical significance==