Have We Learned Anything New About The

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 hav

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