Реферат: Have We Learned Anything New About The
⚡ 👉🏻👉🏻👉🏻 ИНФОРМАЦИЯ ДОСТУПНА ЗДЕСЬ ЖМИТЕ 👈🏻👈🏻👈🏻
Functions Of The Frontal Lobe In The Last Five Years? Discuss Essay, Research Paper
The frontal lobe is thought to be the latest area of the
brain to develop and is largest in humans. It is therefore suggested that the
area plays a key role in differentiating humans from other hominids
(Crespo-Facorro et al 1999; Fuster, 1997). For well over a century research has
investigated the functioning of the frontal region of the human brain (Della
Sala et al, 1998). In 1964 Teuber wrote of the ?riddle of frontal lobe function
in man?, today it is believed that this riddle is still yet to be solved
(Darling et al, in press). Confusions arise as in the first instance, as definitions of
the frontal lobe are not universally clear. In primates the ?prefrontal cortex?
is used for the frontal lobe whilst implicitly excluding the motor cortex and
premotor cortex (Fuster, 1997). The boundaries of the frontal lobe are
therefore traced in various ways, depending on the methods and criterion for
definition. Fuster defined the prefrontal cortex as being the rostral part of
the brain, the part of the cortex that receives fibres from the mediodorsal
nucleus of the thalamus. Parcellation of the cerebral cortex into functionally
distinctive areas is by no means unanimous (Crespo-Facorro, 1999). However some
broad general areas have been discovered. These have been divided into the
motor, premotor and prefrontal areas. The premotor area may also include the
supplementary motor area on the lateral and medial surfaces of the cortex. The
third are is the prefrontal cortex has many subdivisions within itself. These
are classified as the dorsolateral prefrontal cortex, the inferior prefrontal
cortex (including the orbital frontal cortex) and the medial frontal cortex. A
recent MRI based parcellation method (Crespo-Facorro, 1999) used topographical
features of the frontal cortex to produce a map that subdivides the area into
11 subregions. These are shown in Figure 1. The areas include: supplementary
motor area (SMA), rostral anterior cingulate gyrus (rACiG), caudal anterior
cingulate gyrus (c-AciG), superior cingulate gyrus (SC iG), medial frontal
cortex (MFC), straight gyrus (SG), orbitofrontal cortex (OFC), precentral gyrus
(PCG), superior frontal gyrus (SFG), inferior frontal gyrus (IFG), and Middle
frontal gyrus (MFG).The frontal lobe is a large and highly differentiated region
of the brain that is reciprocally connected to other cortical and subcortical
brain areas. The prefrontal cortex is the only neo cortical region that
directly projects to the hypothalamus (Fuster, 1997). Different sub areas have
different connections. For example the orbital prefrontal cortex is connected
to the medial thalamus, hypothalamus, ventromedial caudate and amygdala. The
dorsolateral prefrontal cortex is connected to the lateral thalamus, dorsal
caudate neucleus, hippocampus and neocortex.The question of the functions of the frontal lobe are best
summarise by Fuster (1997, pp. 4). ??????????????? ??????????????? ?The
precise nature of apparently multiple functions of the prefrontal cortex is
still unclear and inevitably the reviewer of the subject is obliged to compile
and attempt to relate large numbers of diverse and seemingly unrelated facts?However despite this wall of problems some general themes
have emerged concerning the frontal lobe. In the last 20 years or so, evidence has converged upon the
view that frontal regions of the brain rather than themselves implementing
specific operations such as memorising, learning or reasoning, are concerned
with the deployment and co-ordination of such functions. According to Fuster, the frontal lobe itself does nothing
but coordinate with other cortices. It is only with regard to the commonality
of cognitive functions at the service of assorted actions that the prefrontal
cortex may be considered functionally ?whole?The frontal lobes have come to be viewed as having an
?executive function?. Many frontal lobe tests such as the Wisconsin Card
Sorting Test and verbal fluency test have supported the idea of an executive.
However the idea of there being a single executive has recently been questioned
, for example Burgess (1997) has argued for the ?fractionation? of the
executive into multiple components , suggesting that there may be distinct
executives for verbal and spatial materials (Della Sala, 2000). McCarthy &
Warrington, 1990) found that lesioned patients can be impaired on one executive
test but not on others.For the purposes of this essay I have chosen two distinct
research articles. One (Duncan and Owen, 2000) attempts to tackle the general
role of the frontal lobes in cognition. The second (Stuss, 2001) examines how a
specific area of the frontal lobe has been implicated in the ability to infer
mental states in others. Both these articles examine primarily the prefrontal
cortex.I have chosen the study by Duncan and Owen (2000) because it
offers broad insight into what has been learnt over the last five years. The
importance of this paper is that from it describes the problems and questions
that researchers have come across in attempting to clearly define the functions
of the frontal lobe. Duncan & Owen (2000) believe that there must be some
regional specialisation in a brain structure as large and complex as the
prefrontal cortex. They point out that unfortunately there is only modest
evidence for this. The problem is that any small region of the frontal cortex
is connected not only to immediate surrounding regions, but also networks of
small, structured patches of cortex that are widely spread through the frontal
lobe (Pucak et al 1996). They theorise that this connectivity may suggest functional
modules. These modules rather than consisting of specific regions may consist
of widely distributed parts. They point out that such specialisation may have
not been shown in the past due to the use of course level resolutions used in
such studies not being able to pick up such a distribution of modules. They use
this theory to show how dividing prefrontal functions into components has been
hindered in past research. They point out that this over generality in current
conceptions of functions such as executive control, and working memory lead to
few strong testable predictions. It is shown that recent functional imaging techniques have
indicated a regional differentiation in the prefrontal cortex. However this
regional specificity in cognitive functions appears to take the form of
co-recruitment of the same areas rather than task dependent regional
differentiation. In this way the areas of the mid-dorsolateral (areas within
and surrounding the middle and posterior parts of the inferior frontal sulcus),
mid-ventrolateral (areas dorsal and anterior to the Sylvian fissure) and dorsal
anterior cingulate areas can be seen to form a networked module of prefrontal
regions recruited to solve diverse cognitive problems.After an initialy study finding such results, this authors
recruited studies that focused on the ?purest possible manipulations of tightly
defined demands? (pp. 477). Using a strict inclusion criterion, five types of
studies were included for analysis. These included response conflict. Frontal
executive functions is said to have a role in suppression of inappropriate
responses. Included in this was the aforementioned ?stroob? test.? Secondly task novelty was investigated. It
is suggested that the frontal executive functions are especially important in
early intentional learning rather than later automatic skills. The studies
involved the comparison of initial learning of unfamiliar tasks with the later
well practiced performance. Third and fourth were working memory tasks. As working
memory is a ?major theme in current accounts of frontal lobe funciton? (pp.
477). These study types were divided between looking at the working memory in
terms of number of elements and in terms of delay before recall. The final type
of study included was perceptual difficulty. Perceptual demand has not been
conventionally associated with executive or working memory and were included as
a comparison to more standard frontal tasks. These included studies of stimulus
degradation and of viewpoint convention. The results show tight definitions of the activation
regions. Principally on the medial surface, activations were almost entirely
restricted to the dorsal part of the anterior cingulate. Other prominate
clusters appered in the mid-dorsolateral region in both hemispheres and the
mid-ventrolateral regions especially in the right hemisphere. Importantly there was a similarity of activation for different
demands. According to Duncan and Owen ?All five demands are associated with a
similar pattern of activations in the dorsal anterior cingulate and in both
mid-dorsolateral and mid-ventrolateral regions? (pp. 479) ?whatever the functions of these regions, they seem to be
recruited by modest increases in demands as diverse as response selection,
working memory maintenance and stimulus recognition? This data is supported by the fact that each individual
experiment showed the full pattern of joint activity I the given regions.?? However the authors do not rule out the possibility of finer
specialistions within the network. The authors state that this may be the case
if finer examination was used, for example single neurone analysis. They also
theorise that specialisation may be of degree, the implication being that
broadly distributed frontal neurones have some relevance to any given activity,
but from one activity to another these neurones may have somewhat different
peaks. Some finer specialisation ? cued recall verses free recall. Have we learned anything new from such as study indeed the
data confirms that ?the understanding of Prefrontal functions is a difficult problem? (pp481)Duncan & Owen claim it is ?very hard to be precise about
the function of a region when that region is important in such a diversity of
behaviour? (pp. 481). Known before how the frontal lobe was functionally
interrelated.This is one example of how little has been learnt in the
last five yearsShallice (2001) believes that despite findings that a large
number of different subprocesses are frontally localised, this has not lead to
much closure on the nature of the individual processes involved. The problems
as has already been mentioned is the subprocesses involved may be too abstract
to map onto ?perceptual output?. Also tasks which activate prefrontal regions
may involve a number of subprocesses therefore making it hard to observe
completions of stages in normal performance. One area of recent work is that involving ?theory of mind?.
This is defined as an awareness of the likely content of other people?s minds
(Wellman and Wooley, 1990). In the past the right hemisphere damage has been
associated with actions that require inference or attribution (McDonald, 1993).
The frontal lobes have been shown to have a role in cognitive functions as well
as social behaviour, personality, memories and self-awareness. Stuss et al
(2001) mention one previous study that directly implicate the frontal lobes in
the theory of mind. This study by Stone et al (1998) used lesioned patients.
Past research has shown how damage to the left or right orbitofrontal/ ventro
medial areas consistently caused personality changes.The authors also mention functional imaging data that has
found the left medial frontal lobe to be active in theory of mind tasks.
(Fletcher et al., 1995). They point out that while imaging data shows what
areas are involved, they do not show which areas are necessary for the theory
of mind. The paper used two main tasks. Both required patients to make
inferences about the location of an object they couldn?t see based on the
direction the experimenter was pointing to. The First involved verbal
perspective taking. In this experiment patients had two people pointing to the location
of a hidden object, only one of which could actually see the location of this
object. Therefore they had to infer position from this person. It was found
that frontal patients produced a much higher error rate on this task. It was
also suggested that the right frontal lobe was the most critical region. The
second task involved deception. For this the hidden object had two possible
positions. This time, the one experimenter always pointed to the wrong
position. This time there was a striking right medial prefrontal difference
patients. Bifrontal lesions involving medial regions impaired
performance on the decetion tas. The cognitive processes of the frontal regions
are likely to play a network role in metarepesentation. The impairment in
perspective taking did not appear to be a direct consequence of such cognitive
deficits. The authors point out that cognitive features such as working
memory? and attention were controlled
for. They also point out that the ventral medial frontal regions may be so
important because connections with the amygdala and other limbic structures
give them a key role in the neural network of behavioural modulation based on
emotions and drives (Pandya and Yeterian, 1996). Further evidence for the importance of the frontal lobes in
theory of mind is from functional imaging studies. Frith and Frith (1999)
conducted a meta-analysis of such studes. An updated version of this is shown
in figure 1. Here the medial prefrontal cortex in particular the paracingulate
sulcus has been shown to be involved in reports of mental states. Indeed in one
of these studies, Gallagher et al (2000) the paracingulate cortex was the only
region activated in both story and cartoon comprehension theory of mind tasks.
This implies that the ability to attribute mental state is independent of
modality with the medial frontal cortex.Within the last five years we have discovered that the
frontal lobe is involved to some extent in wide reaching parts of behaviour.
Ten to fifteen years ago there was little knowledge of the functions of the
functions of the subregions of the human prefrontal cortex (Shallice, 2001;
Fuster 1989). With this time many activities have been found to be frontally
localised. Fuster (1997) wrote that the prefrontal cortex was a ?doer? as the
posterior cortex is a ?sensor?. In the last five years more and more areas of
activation have been discovered. For example episodic memory, humour,
aggression, TOM, (Henson et al, 1999; Stuss, xxxx, Hawkins & Trobst, 2000;
Stuss et al 2001) have now been associated with the frontal lobe in the last
five years. Undoubtedly in the next five years, more aspects of emotion and
behaviour will be associated to some extent with the frontal lobes. For example
it is entirely plausible that ?love? may be associated with the frontal cortex For example following their topographical MRI parcellation
of the frontal lobes, Crespo-Facorro et al (2000) have implicated regional
frontal abnormalities in schizophrenia. These abnormalities refer to cortical
surface size abnormalities in the right straight gyrus and left orbitofrontal
cortex. Have we learned anything new from such as study indeed the
data confirms that ?the understanding of Prefrontal functions is a difficult problem? and it is ?very
hard to be precise about the function of a region when that region is important
in such a diversity of behaviour? (Duncan and Owen, 2000 pp481)Yes we have leant new things but of function??In terms of cognition and emotion, it is clear that there
are functionally separate subregions. Defining these subregions has been linked
with function. However such is the ?Riddle of the frontal lobe? that
advancements within the last five years have simply added more to the riddle
and we are only slightly nearer the answer of how the frontal lobe functions. We now know that certain emotional and various cognitive
features are frontally clustered. It is possible in cognition that certain
subregions function as a network with other frontal regions? ? Hawkins,K & Trobst, K (2000). Frontal lobe dysfunction
and aggression: Conceptual issues and research findings. 5, 2, 147-157Hensen in shalliceWellman, HM.,? and
Wooley HD.? (1990) From simple desires
to ordinary beliefs: the early development of everyday psychology. Cognition, 35, 245-275Crespo-Facorro,
B., Kim, J., Andreasen, N., O?Leary, D., Wiser, A., Bailey, J., Harris, G.,
Magnotta, V. (1999) Human Frontal Cortex: An MRI-Based Parcellation Method. NeuroImage
10, 5,.Della Sala, S., Gray, C., Spinnler, H., Trivelli, C.
(1998). Frontal Lobe Functioning in Man: The Riddle Revisited Archives
of Clinical Neuropsychology, Vol. 13, No. 8, pp. 663?682,Duncan, J & Owen, A. (2000). Common regions of the human frontal lobe
recruited by diverse cognitive demands. Trends
In Neuroscience. 23, 475-483.McCarthy, R. A., &
Warrington, E.K. (1990). Cognitive neuropsychology: A clinical introduction. London: Academic Press.Stuss, D., Gallup, G.,
Alexander, M. (2001). The frontal lobes are necessary for ?theory of mind?. Brain, 124, 279-286Shallice, T. (2001).
Editorial: ?Theory of mind and the prefrontal cortex?. Brain, 124, 279-286.Gallagher, H., Happe,
F., Brunswick, N., Fletcher, P., Frith, U., Frith, C. (2000). Neuroosychologica, 38, 11-21Fuster, J. M. (1997).
The Prefrontal Cortex: Anatomy, Physiology and Neuropsychology of the Frontal
Lobe (Third Edition). Lippincott-Raven. PhiladelphiaStone, VE, Baron-Cohen
S, Knight RT. Frontal lobe contributions to the theory of mind. In Stuss, D.,
Gallup, G., Alexander, M. (2001). The frontal lobes are necessary for ?theory
Название: Have We Learned Anything New About The
Раздел: Топики по английскому языку
Тип: реферат
Добавлен 16:50:00 27 октября 2010 Похожие работы
Просмотров: 2
Комментариев: 13
Оценило: 1 человек
Средний балл: 5
Оценка: неизвестно Скачать
Срочная помощь учащимся в написании различных работ. Бесплатные корректировки! Круглосуточная поддержка! Узнай стоимость твоей работы на сайте 64362.ru
Привет студентам) если возникают трудности с любой работой (от реферата и контрольных до диплома), можете обратиться на FAST-REFERAT.RU , я там обычно заказываю, все качественно и в срок) в любом случае попробуйте, за спрос денег не берут)
Да, но только в случае крайней необходимости.
Реферат: Have We Learned Anything New About The
Доклады На Тему Структура, Воспроизводство Населения И Особенности Миграции
Оформление Рисунка В Курсовой По Госту
Дипломная работа по теме Инвестиционный проект по развитию производства гофротары
Реферат: Домашние хозяйства и их роль в эк-ке России
Дипломная Работа На Тему Мочекаменная Болезнь
Курсовая работа по теме Фізична реабілітація після компресійних переломів
Сочинение По Дубровскому История Владимира И Маши
Практическая Работа Расчет Механизма
Анализ Способов Беспроводного Доступа Реферат
Реферат по теме Конкурс 1401-го года
Курсовая работа: Расчет и подбор выпарной установки. Скачать бесплатно и без регистрации
Курсовая работа: Разработка модели программного обеспечения для телевизора в среде Rational Rose
Курсовая работа по теме Исследование CAM-систем. Разработка имитационной модели
Курсовая работа по теме Санитарно-эпидемиологические требования к продукции общественного питания
Курсовая работа по теме Понятие трудового договора и его функции. Отличия трудового договора от гражданско-правовых договоров, предметом которых является выполнение работ или оказание услуг
Практические Работы Степень И Ее Свойства
Курсовая Работа На Тему Особенности Размещения Наружной Рекламы В Г. Челябинск
Реферат: К проблеме оптимизации межэтнических, межконфессиональных отношений
Реферат по теме Експлуатація екскаваторів ЕО-5123, ЕО-6122
Курсовая работа по теме Изменения европейской жизни и быта в Новое время
Курсовая работа: Товароведная оценка порционных блюд и мелкокусковых полуфабрикатов
Реферат: Swift Essay Research Paper Swift
Реферат: Структура экосистем