BIOLOGICAL BASIS OF BEHAVIOR
Psychology 321
Spring, 2005 HGH 225
Dr. John M. Morgan MWF, 8am to 9:00
Erin Averill
Prefrontal Cortex-- Neurologists Perspective
The prefrontal cortex is the most anterior portion of the
frontal lobe. It responds mostly to stimuli signaling the need
for movement, however it is also responsible for many other
specialized functions. It receives information from all sensory
systems and can integrate a large amount of information (Kalat
2004).
Studies have shown that the prefrontal cortex is
responsible for working memory. Working memory is defined as
"the information that is currently available in memory for
working on a problem" (Anderson 2005). The prefrontal cortex
(PFC) also controls behaviors that depend on context (Kalat
2004). For example, if my cell phone rings when I am at the
mall or grocery store I would answer it. If it rings while I am
at the movies or in class I wouldn't answer it. People with
frontal lobe damage often exhibit inappropriate behaviors due to
the inability to recognize context.
Other studies indicate that the PFC is also responsible for
regulating emotions and decision-making. A study was conducted
in which participants were presented with three dilemmas. One
dilemma was called the Trolley Dilemma: a trolley is headed
toward five people standing on the track. You can switch the
trolley to another track killing only one person instead of
five. Subjects were asked to decide between right and wrong.
Brain scans of the participants show that contemplating the
dilemmas activates the prefrontal cortex and other areas that
respond to emotion (Kalat 2004).
Sustaining a lesion to the prefrontal cortex produces a
wide variety of side effects. The effects range from minor to
severe. You can get a lesion by head trauma or stroke (CJ Long
2005).
Possible deficits associated with minor lesions of the
prefrontal cortex:
? Inability to respond quickly to verbal instructions
? Speech dysfluency
? Disturbances in understanding complex pictures or words
? Difficulties with problem-solving
? Deficits in complex tasks requiring inhibition of habitual
behavior patterns
With more extensive lesions the person experiences greater
behavior deficits. These deficits include: perseveration, which
is the inability to make behavioral shifts in attention,
movement and attitude, decreased creativity, poor recall of
verbal and nonverbal material, difficulty writing, and deficits
in comprehension of logical-grammatical constructions (CJ Long
2005).
Other effects of extensive lesions:
? easily distracted
? disturbances in memory
? defects in time sense
? decreased anxiety
? less critical of oneself
? difficulty with unfamiliar analogies
? impulsivity
? emotional disturbances such as: apathy, withdrawal, euphoria,
irritability, and obscene language.
Mah, Arnold, and Grafman (2004) conducted a study about the
impairment of social perception associated with lesions of the
prefrontal cortex. They used the Interpersonal Perception Task,
which consisted of several videotapes of social interaction.
For each social interaction participants were asked to judge
different aspects of behavior such as level of intimacy and
social status (Mah, Arnold, and Grafman 2004). The results of
the judgments were compared between participants with prefrontal
lesions and healthy participants. The results showed that
participants with prefrontal lesions showed poorer performance
on the Interpersonal Perception Task than the healthy
individuals. This means that participants with prefrontal
cortex lesions were less able to interpret social behavior thus
implying other cognitive deficits.
This study also found a strong correlation between
performance on the Interpersonal Perception Task and other
cognitive deficits, including deficits in working memory and
executive function. These deficits also affect decision-making
ability, which explains why subjects were having difficulty
interpreting social situations (Mah, Arnold, and Grafman 2004).
The results from this experiment also show deficits in
theory of mind. Theory of mind is the "ability to attribute
mental states to self and others" (Mah, Arnold, and Grafman
2004). The task required participants to use nonverbal cues to
pass judgments about the type of relationships shown between
individuals. This requires "accurate perception of social cues
as well as perspective-taking," which this experiment has shown
that people with prefrontal cortex lesions have trouble doing.
Impaired social perception contributes to inappropriate
responses in subjects with prefrontal lobe damage. Damage in
this brain region may also be involved in deficits in perception
of emotional cues, interpersonal judgments, and self-awareness
of cognitive ability (Mah, Arnold, Grafman 2004).
There have been several case studies done on the effects of
prefrontal lesions on children and how it affects their
development. Ackerly and Benton (1948) did a study on JP, which
is one of the most informative cases available. He had
extensive prefrontal lobe damage with a congenital onset.
However, JP seemed to be developing normally, he learned to walk
and talk by age 1. His family didn't notice a problem until he
was 3 years old when he began to wander long distances without
fear. He also had problems in school. He was boastful, bossy,
and stole money from other kids. He also had impairments in
inhibition, attention, working memory, delay of responding,
which are all typical characteristics of prefrontal cortex
damage. Because of his poor social adjustment he was extremely
disliked in school. The authors of the study determined his
primary social defect as an "immature level of differentiation
and elaboration of the cognitive and affective processes that
underlie role-taking, theory of mind, cooperation, and self-
evaluation" (Benton, Eslinger, Flaherty-Craig 2003).
Eslinger studied DT, who experienced a left frontal lesion
at age seven. She developed pronounced social impairment
including social alienation and uncooperative behaviors. She
was argumentative, did not share, and showed little concern for
others. In school she had poor attention control, trouble
learning, and was disorganized. Her social ineptness carried on
throughout her life. As an adult she continued to show
immature, impulsive and erratic behaviors. She could not
regulate her emotions and could not anticipate the needs of
others. She managed to get married and have a child, however
her extreme deficits seriously compromised her ability as a
mother and wife. She could not hold down a job due to
disorganization and lack of commitment. She ranked lower than
average in intelligence, working memory, executive function, and
problem-solving. Her moral development was also around that of
a 10-13 year old. Her poor regulation of emotion, lack of
empathy, argumentativeness, and disregard for social boundaries
led to severe social problems.
Among all the case studies reviewed in the article
Developmental Outcomes After Early Prefrontal Cortex Damage, the
authors noted several distinct characteristics present among all
the patients:
? impaired social cognition- uncooperative, limited perspective
taking skills
? learning deficits
? impaired cognition - decreased intellectual capacities
? deficits in personality and emotion - impatience,
irritability, egocentric, and labile moods
? deficits in moral behavior and empathy
The above mentioned deficits are consistent effects
reported for patients with lesions to the prefrontal cortex.
References
Anderson, John R. (2005) Cognitive Psychology and its
Implications. Worth Publishers: New York.
Eslinger, Paul J., Flaherty-Craig, Claire V., Benton, Arthur
L. (2004). Developmental outcomes after early prefrontal
cortex damage. Brain and Cognition, 55, 84- 103.
Kalat, James W. (2004) Biological Psychology. Ontario, Canada:
Wadsworth.
Long, C.J. Brain-Behavior Relationships: Prefrontal Cortex.
http://neuro.psyc.memphis.edu/NeuroPsyc/np-12-pref.htm.
Mah, Linda, Arnold, Miriam C., Grafman, Jordan. Impairment of
social perception associated with lesions of the prefrontal
cortex. American Journal of Psychiatry, 161, 1247-1255.
Holly Young
Psyc 321
Prefrontal Cortex Lesions from Neurosurgeon and Patient
Perspective
In this section of the paper, I will discuss lesions of the
prefrontal cortex from the perspective of the practice of
neurosurgery (in particular, the sub-field of psychosurgery) and
then I will consider some studies that look at the implications
of lesions to the prefrontal cortex to the brain and behavior,
from the perspective of the patient with the lesion. Initially,
I will start with the history and explanation of psychosurgery.
Psychosurgery is the branch of neurosurgery that involves
severing or otherwise disabling areas of the brain to treat a
personality disorder, behavior disorder, or other mental illness
(Rodgers 1992). Modern psychosurgical techniques target the
pathways between the limbic system (the portion of the brain on
the inner edge of the cerebral cortex) that is believed to
regulate emotions, and the frontal cortex, where thought
processes are seated.
The field of neurosurgery as a specialty was not defined
until the end of the 19th century. In earlier days, surgeries
had to be tailored to poor lighting and lack of magnification
(Valenstein 1986). The development and implementation of the
operating microscope in the 1960s allowed surgeons to operate
through a narrow tunnel to resect deep-seated lesions
(Valenstein 1986). Psychosurgery, and lobotomy in particular,
reached the height of use just after World War II. Between 1946
and 1949, the use of the lobotomy grew from 500 to 5,000 annual
procedures in the United States (Valenstein 1986). Lobotomy is a
psychosurgical procedure involving selective destruction of
connective nerve fibers or tissue. It is performed on the
frontal lobe of the brain and its purpose is to alleviate mental
illness and chronic pain symptoms (Valenstein 1986). At that
time, the procedure was viewed as a possible solution to the
overcrowded and understaffed conditions in state-run mental
hospitals and asylums. Known as prefrontal or transorbital
lobotomy, depending on the surgical technique used and area of
the brain targeted, these early operations were performed with
surgical knives, electrodes, suction, or ice picks, to cut or
sweep out portions of the frontal lobe.
Today's psychosurgical techniques are much more refined.
These technological advances include the use of computer-
assisted stereotaxis, intra-operative ultrasound, brain mapping
and endoscopy. Minimally invasive surgery is a major advance in
neurosurgery and refers not only to a more limited skin incision
with precise centering of a burr-hole or small craniotomy
directly over the brain lesion, but also to the planning of a
precise trajectory to the lesion that will not injure adjacent
brain (“Minimally” 2005). The least invasive treatment option
available to neurosurgeons is radiosurgery, which combines
radiotherapy techniques with sophisticated computer-assisted
stereotaxis.
Instead of going in "blind" to remove large sections on the
frontal lobe, as in the early operations, neurosurgeons use a
computer-based process called stereotactic magnetic resonance
imaging to guide a small electrode to the limbic system (brain
structures involved in autonomic or automatic body functions and
some emotion and behavior) (Spangler 1996). There an electrical
current burns in a small lesion (usually 1/2 inch in size). In a
bilateral cingulotomy, the cingulate gyrus, a small section of
brain that connects the limbic region of the brain with the
frontal lobes, is targeted. Another surgical technique uses a
non-invasive tool known as a gamma knife to focus beams of
radiation at the brain (Spangler 1996). A lesion forms at the
spot where the beams converge in the brain.
Psychosurgery is considered only after all other non-
surgical psychiatric therapies have been fully explored. Much is
still unknown about the biology of the brain and how
psychosurgery affects brain function; therefore, candidates for
psychosurgery undergo a rigorous screening process to ensure
that all possible non-surgical psychiatric treatment options
have been explored (Rodgers 1992). Psychosurgery is performed
only with the patient's informed consent. As with any type of
brain surgery, psychosurgery carries the risk of permanent brain
damage, though the advent of non-invasive neurosurgical
techniques, such as the gamma knife, has reduced the risk of
brain damage significantly.
A neurosurgeon might lesion an area of the prefrontal
cortex, either to fix a brain deficit or accidentally cause a
deficit; there are numerous deficits that can result from
prefrontal lesions. The prefrontal cortex is responsible for
“executive functions;” planning, structuring, and evaluating
voluntary goal directed behavior, which are activities requiring
the constant comparison of planned acts with the effects
achieved. It is a region of the cerebral cortex thought to be
unique to primates; the same area in rats, for example, is
thought to be used for generating movements and processing the
emotions and rewards associated with them (Rainer 2001). In
humans, the prefrontal cortex is composed of a number of highly
interconnected frontal lobe areas (Wood 2003). At the coarsest
level, researchers have differentiated between dorsolateral,
ventrolateral, orbitofrontal, and anterior prefrontal cortex.
Although it is unclear what precise functions these regions
implement, it is clear that these regions typically work in
concert to enable goal-directed behavior. The orbitofrontal
cortex lies just on top of the eyes, and seems to have a role in
adding an emotional element to planning and decisions. The
ventrolateral prefrontal cortex lies on the side of the front
bit of the forehead, and is important in working memory. The
dorsolateral prefrontal cortex is important in decision making,
and particularly in switching and maintaining 'attentional set'
(Wood 2003). Pre-frontal neurons participate in a variety of
functions, including motor planning (Manes 2003) and the
processing of auditory (Manes 2003) and somatosensory (Manes
2003) stimuli. The pre-frontal cortex also contains many neurons
that respond selectively to complex objects (Wood 2003).
One of the main functions of the prefrontal cortex
presented through the literature is in working memory. The role
of working memory seems to be in guiding and adapting behavior
through its ability to hold information (Bechara 1998). This has
been demonstrated through the impaired performance of monkeys
with prefrontal damage on delayed matching to sample, and
delayed non-matching to sample tasks (Passingham, 1998). Such
inability to adapt and change behavior is also seen in humans
with prefrontal lesions. (A lesion is any discontinuity of
tissue, often a cut or wound) (Rodgers 1992). Patients with
frontal lesions tend to be absent-minded and very easily
distracted (Shallice 1991). They do not seem to organize and
plan actions very well. For instance, patients have been known
to be completely unable to do shopping efficiently. They might
go into the shop, purchase just one item, return to their car,
re-enter the shop, buy one more item, return to their car, and
so forth (Shallice 1991). Difficulties in such "multiple sub-
goal tasks" are fairly common among frontal patients. Patients
with frontal lesions also tend to display behavioral responses
inappropriate to the situation and this can be clearly seen in
the Wisconsin Card Sort Test (where cards have to be sorted
according to color, shape, or number, depending on whether the
experimenter says "right" or "wrong"). Using this apparatus,
Milner (1963) observed that patients with frontal lesions had
difficulty in figuring out the first sorting principle, and
furthermore, were impaired in the ability to shift to a second
sorting principle when required. Shallice and Burgess (1991)
account for problems in the performance of multiple sub-goal
tasks by the lack of a "supervisory system" controlling
processes such as goal articulation, plan formulation, and the
creation and triggering of markers (a message that some future
behavior or event is significant to current goals). Rolls (1998)
attributes the problems in performing the Wisconsin Card Sort
Test, not to working memory problems, but rather to problems in
altering behavior to changes in stimulus-reinforcement
associations. Rolls suggests that the "orbitofrontal cortex is
involved in emotional responses by correcting stimulus-
reinforcement responses when they become inappropriate".
I will not detail emotional deficits
associated with prefrontal damage in this paper, but I will
state briefly that emotional disturbances fall under two
principle reactions: inhibition (apathy, narrowing of interests,
flattered affect, withdrawal) and disinhibition (euphoria,
impulsivity, irritability, anxiety, obscene language (Luria
1969). Decreased spontaneity, decreased rate of behavior,
decreased range of interests, loss of initiative, and
impulsiveness without self-corrective action may be early signs
of a lesion (Davidson 1977). These disturbances are often
related to decision making, which is another function that has
been attributed to the prefrontal cortex. A study by Bechara et
al. (1998) confirms that this process is located in the
prefrontal region, and in addition, that decision making is a
distinct process from the working memory processes that are
known to exist in prefrontal cortex. The experimenters tested
patients with various frontal lesions with delay tasks that
assessed working memory and with a gambling task that assessed
decision making. It was found that among the subjects with
ventromedial prefrontal lesions, those with more anterior
lesions had an impaired performance on the gambling, but not the
delay task, whereas those with more posterior lesions were
impaired on both tasks. Among the patients with
dorsolateral/high mesial lesions, those with right hemisphere
lesions were impaired on the delay task, but not the gambling
one, whereas those with left hemisphere lesions displayed no
impairment of either task. This experiment successfully
demonstrated a cognitive and anatomical double dissociation
between decision making deficits (localized in anterior
ventromedial prefrontal cortex) and working memory (localized in
right dorsolateral/high mesial prefrontal cortex). The authors
suggest that the decision making impairment, caused by anterior
vetromedial lesions, is linked to "insensitivity to future
consequences" (1998). In other words, such patients seem
oblivious to the future and instead are guided by immediate
prospects, whether they are positive or not. They specifically
do not link their results to an explanation by failure to
inhibit previously rewarded responses (perhaps suggesting that
Rolls' stimulus-reinforcement ideas are confined to
orbitofrontal cortex). Nor do they agree with the view that
there is an impairment in selective attention in that subjects
are unable to shift their attention to a new and beneficial
objects in the gambling task. In another interesting
experiment, done by Milne and Grafman (2001), patients with
prefrontal cortex lesions and controls were administered an
implicit association task (IAT) that measured the degree of
association between male and female names and their
stereotypical attributes of strength and weakness. They also
completed three questionnaires measuring their explicit judgment
regarding gender-related stereotypical attributes (Milne 2001).
There were no between-group differences on the explicit
measures. On the IAT, patients with dorsolateral lesions and
controls showed a strong association, whereas patients with
ventromedial prefrontal cortex lesions had a significantly lower
association, between the stereotypical attributes of men and
women and their concepts of gender (Milne 2001). This finding
provides support for the hypothesis that patients with
ventromedial prefrontal lesions have a deficit in automatically
accessing certain aspects of overlearned associated social
knowledge (Milne 2001).
After ventromedial frontal lobe brain injury, patients
often demonstrate acquired social conduct deficits such as an
inability to respond appropriately to social cues in the
environment or failure to obey conventional social rules (Milne
2001). These deficits may be accompanied by a lack of awareness
of what is socially appropriate (Milne 2001). Because of these
deficits, the ventromedial sectors of the prefrontal cortex have
been considered the repository of social knowledge of the brain
that is required for managing interpersonal interactions
(Grafman, 1994, 1995). If this knowledge becomes inaccessible or
degraded, behavior may default to inappropriate social rules for
the situation or be guided by more instinctive or primitive
responses induced by the environment (Grafman, 1994, 1995).
Evidence from previous studies has suggested that despite
their aberrant real-life behavior, some patients with
ventromedial frontal lobe lesions do possess, and can access,
the social knowledge that they appear not to use in everyday
life. For example, patient E.V.R.-- cited because of a striking
dissociation between his preserved language, memory, and
intellectual skills and his profoundly impaired social conduct,
which developed after bilateral excision of orbital and lower
mesial cortices-has been tested on several explicit measures of
social cognition requiring means end problem solving of social
situations and prediction of social solutions and was found to
perform at levels equivalent or superior to normal controls
(Milne 2001). One explanation for his impaired social decision
making is that ventromedial frontal lobe lesions result in a
somatic marking deficit (Damasio 1998). Somatic marking is a
hypothesized mechanism that binds a positive or negative valence
to a behavioral action that facilitates the decision of what is
the correct or appropriate response in a given social situation.
On the other hand, Dimitrov et al. (1998) have demonstrated
that unlike E.V.R., some patients with ventromedial lesions
display impaired social knowledge compared with matched controls
on an inventory designed to measure a person's understanding of
the relative effectiveness of various solutions to everyday
social problems (Dimitrov et al., 1999). To further investigate
the cause of the social conduct disorder frequently observed in
patients with prefrontal cortex lesions, Milne and Grafman
(2001) adapted a task from the social cognition literature that
addresses the nature and organization of stored social
knowledge. The implicit association task (IAT) is used to
measure the automatic concept-attribute associations that are
hypothesized to underlie implicit social attitudes and
stereotypes (Milne 2001). Normal subjects typically demonstrate
relatively faster reaction times when they are asked to map
stereotypically compatible (compared with incompatible) concepts
onto a single response (known as the IAT effect). Scores on this
implicit measure are often weakly (if at all) associated with
explicit scores based on probing of attitudes or stereotypes
(Milne 2001). Stereotypes can be considered a form of social
knowledge
Patients with ventromedial prefrontal cortex lesions showed
impaired automatic priming of stereotypic social knowledge,
whereas those with dorsolateral prefrontal cortex lesions
performed like normal subjects. Social bias, such as a gender
stereotype, represents social knowledge that is acquired during
development. The content of the stereotype is dependent on
cultural factors and the environmental influences to which an
individual is subjected. Stereotypes reflect an economy of
thought (Milne 2001), an attempt to organize the world around us
into groups and categories that have certain perceived
attributes (2001). Despite the small number of subjects examined
the Milne (2001) study, the results indicate that patients who
suffered ventromedial prefrontal cortex lesions have a degraded
representation of social knowledge that can be demonstrated
through priming experiments.
References:
Bechara et al. (1998), Dissociation of working memory from
decision making within the human prefrontal cortex, Journal of
Neuroscience 18, 428-37
Damasio AR (1995) On some functions of the human prefrontal
cortex. Ann NY Acad Science 769:241-251.
Damasio AR (1998) Emotion in the perspective of an integrated
nervous system. Brain Res Brain Res Rev 26:83-86
Davidson, L.A. (1977). Syndromes of deficits by area of maximal
cortical damage. In Reitan, R.M. and Davison, L.A.,
Neuropsychological Procedures and Methods, unpublished manual.
Dimitrov M, Grafman J, Hollnagel C (1996) The effects of
frontal
lobe damage on everyday problem solving. Cortex 32:357-366.
Dimitrov M, Phipps M, Zahn TP, Grafman J (1999) A thoroughly
modern gage. Neurocase 5:345-354
Grafman J (1994) Alternative frameworks for the
conceptualization of prefrontal lobe functions. Handbook of
neuropsychology (Boller F, Grafman J, eds): 187-202. Amsterdam:
Elsevier.
Grafman J (1995) Similarities and distinctions among current
models of prefrontal cortical functions. Ann NY Acad Sci
769:337-368.
Luria, A.R. (1969). Frontal lobe syndromes. In P.J. Vinken and
G.W. Bruyn (Eds.), Handbook of Clinical Neurology II. New York:
Elsevier.
Manes, F. Sahakian, B. Clark, L. Rogers, R. Antoun, N. Aitken,
M. & Robbins, T. (2002). Decision-making processes following
damage to the prefrontal cortex. Brain, 125, No. 3: 624-639.
Milner, B. (1963). The effects of different brain lesions on
card
sorting. Archaeological Neurology 9, 90-100.
Milne E. & Grafman J. (2001). Ventromedial Prefrontal Cortex
Lesions in Humans Eliminate Implicit Gender Stereotyping. The
Journal of Neuroscience, (21): RC150:1-6
“Minimally Invasive Neurosurgery”: Department of Neurosurgery,
Singapore General Hospital. Retrieved from
http://www.sgh.com.sg/MedicalSpecialtiesnServices/ClinicalS
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y/ (28 April 2005).
Passingham, R.E. (1998), Attention to action. The Prefrontal
Cortex, Eds. Roberts, Robbins, Weiskrantz, OUP, Oxford.
Rainer, G. & Ranganath C. (2001). Coding of Objects in the
Prefrontal Cortex in Monkeys and Humans. Neuroscientist.
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Rao, S.C., Rainer, G., Miller, E.K. (1997). Integration of what
and where in the primate prefrontal cortex, Science 1997 May 2:
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Rodgers, J.E. (1992). Psychosurgery: Damaging the Brain to Save
the Mind. New York: HarperCollins.
Rolls, E.T. (1998), The orbitofrontal cortex, in; The Prefrontal
Cortex, Eds. Roberts, Robbins, Weiskrantz, OUP, Oxford.
Shallice, T., and Burgess, P.W. (1991). Deficits in strategy
application following frontal-lobe damage in man, Brain 114,
727-41
Valenstein, Elliot S. (1986). Great and Desperate Cures: The
Rise and Decline of Psychosurgery and Other Radical Treatments
for Mental Illness. New York: Basic Books.
Spangler, W.J., et al. (1996). "Magnetic Resonance Image-Guided
Stereotactic Cingulotomy for Intractable Psychiatric Disease."
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Neuropsychologist
Eric Wilcox
Lesions to the Prefrontal Cortex
Basic anatomy
The prefrontal cortex is the last part of the brain to mature,
it is considered the latest development in evolution, and it is
characteristic of the highest thinking animals. In humans, the
prefrontal cortex matures in the late teens and early twenties.
Aspects of memory dependent upon the prefrontal cortex improve
at maturation. Increase in white matter occurs while the number
of neurons decrease in a process called aptosis. This is the
maturation of the cortex, the successful connections of neurons,
and the death of neurons that fail to connect. Children have a
better chance of recovery from lesions than do adults.
There are fundamental differences between the limbic and
eulaminate cortices of the prefrontal cortex. The limbic
cortices have three distinguishable layers, more rarely four.
The eulaminate areas have six layers. The differences in these
areas are their behavioral and physiological aspects.
Projections from the thalamus extend to the prefrontal cortex.
The thalamus makes connections with all the cerebral cortex, and
sends signal from the sensory peripheral to the respective
sensory cortices. Thalamic input, though, is thought to
contribute to cognitive, mnemonic, and emotional function in the
prefrontal cortex. The eulaminate areas receive less than half
the projections, whereas the limbic cortices receive more
projections.
The hippocampus and amygdala are two limbic structures that
project tracts into the medial limbic and orbitofrontal cortices
of the prefrontal cortex targeting the limbic cortices heavily.
In general, limbic cortices are more heavily connected with
other limbic cortices, as in the occipital, temporal, and
parietal cortices, which have more modalities than the
eulaminate connections. This is in part the description of the
executive function of the prefrontal cortex, for it connects
with many parts of the brain, and is executive in the planning
with this communication, as well as many other functions.
Lesions and Effects: On Attention and Perception
Depending upon the location of the lesion in the prefrontal
cortex, there are three categories of disordered functions in
the behavioral sphere, the cognitive sphere, and the affective
sphere.
The most common cognitive disorder comes from abnormalities of
attention. When damage occurs to the dorsolateral prefrontal
convexity there is dysfunction with low alertness and low
awareness to the world around the patient. There is little
interest in the environment or the motives and activities of
other people. There is less participation in society.
There seems to be a basic lack of drive. So, they are less
spontaneous in their actions. The low arousal could be
responsible for attention difficulties. Sensory neglect is a
more specific form of attention deficit which is a lack of
awareness on one side of the body contralateral of a unilateral
prefrontal lesion. Neglect also has to do with not attending to
half the field of vision.
Distractibility may occur from orbitalfrontal lesions where the
person is unable to resist interference from stimuli.
Disorder of visual search and gaze control is the loss of
normal, logical order in the analysis of pictorial detail.
Visual examination is haphazard and unsystematic. The person
may gaze at the expense of gathering pertinent details.
The most consistent trait of these disorders is the difficulty
in sustaining attention. The greater the duration and
complexity of a mental operation, the more evident is the
deficit.
Internal interference results from impulses that interfere with
attention. To test function, the Wisconsin Card Sorting Test
(WCST) uses four “target cards” face up, each with a different
printed design, number of designs, and color. The subsequent
cards are to be placed according to the category principles.
After reaching ten correct choices, the clinician creates new
category principles. The patient must discard the
old principles and discover the new; they must keep the shift in
mind. Poor performance can show internal interference and that
this may be responsible for poor short-term memory tasks.
On Motility
Defective motor attention (set) may be disrupted. This can be
seen in motor tasks that are liable to internal interference
from impulses that need to be inhibited or suppressed. Although
lesions in the prefrontal cortex are not located near the
premotor or motor cortex, disorders of motility can occur.
Disorders come in two forms; general spontaneous, and goal-
directed motor behavior. Hypokinesia seems logical in its
association with apathy and lack of initiative, and reactivity
to stimuli involved with attention dysfunction. Degrees in
severity range from “aspontaneity” which affects language and
social behavior, to akinetic-abulic syndrome with mutism. These
can result from lesions to the dorsolateral, as well as the
orbitomedial areas (Fuster,1997 p.155).
Hyperkenisia is excessive motility and is common with
orbitofrontal lesions. Hyperactivity, instinctual
disinhibition, distractibility, hypomania, and irritability are
some other symptoms.
With goal-driven motor behaviors, motility disorders are more a
result of cognitive dysfunction which impedes the initiative and
temporal organization of action.
People show few deliberate acts, and lack initiative whether it
comes from general motility or goal-directed motility. However,
the patient may show an increase in automatic behaviors.
Repetitious patterns in routine behaviors are resorted to in
what is called perseveration. When faced with seemingly
insurmountable cognitive tasks, the patient regresses to routine
behavior in an attempt to solve the problem, and may seem
superstitious.
Long-term memory seems not to be affected, while recent memory
is. This is attributed to the low perceptual attention and low
motivation. In essence the person forgets to remember. Also,
there is impairment to the working short-term memory, or
provisional memory. This is needed for all planning of actions,
mental, motor, or language. There are batteries of tests for
this function. Delay task tests, and the Wisconsin Card Sorting
Task are just a couple of them, and that we as
neuropsychologists need to know how to apply them.
The WCST tests short-term memory and the ability to withstand
interference from unimportant memories. Lesions to the
dorsolateral and orbitomedial regions affect performance.
However, people with lesions in some
nonfrontal areas perform poorly, as well. There is some
question to the WCST’s validity for testing prefrontal patients.
There are difficulties in controlling for attention or deficit
factors, and attributing memory deficit to interference.
Frontal lesions can impair suppression of interference as well
as memory. Testing is difficult.
Planning
Faulty short-term memory affects a person’s ability to use their
experience of the recent past, whereas faulty foresight impairs
the ability to plan for the future. These two deficits are a
“mirror image” of each other, one being retrospective, the other
is prospective. A lesion to the dorsolateral prefrontal
convexity produces deficits in both. The inability to plan is
the most consistently recorded dysfunction.
Unlike the memory deficit, which arouses controversy, the
deficit in prospective memory is strictly associated with the
prefrontal cortex.
This is also known as executive function, and it depends upon
the ability to plan. To test this, one test called the Tower of
London consists of three wooden pegs, and three wooden rings of
different colors. One peg holds three rings, the second can hold
two, the third, one. The rings are placed one on each peg to
start. The patient must move the rings to a desired
configuration in a minimal amount of moves. This test requires
planning a series of sub-goals to reach the final goal. This
requires anticipation and visualization of the goal, and to
internally arrange the proper sequence. Lesions to the left
hemisphere perform poorly. Maze tests prove difficult as well,
probably due to poor planning.
Intelligence
It has been argued that evolution has developed the frontal lobe
last and is characteristic of the higher intelligent animals.
However, people have tested normal to above average on I.Q.
tests with prefrontal lesions. Logic dictates that deficits in
verbal expression, memory, abstraction, and the ability to
formulate behavioral plans and to pursue them to their goal
(Fuster, 1997 p.163), are components of intelligence needed for
temporal integration of behavior which is complex, original, and
creative. Therefore, a couple of I.Q. tests should be able to
determine frontal lobe damage. The Weschsler Adult Intelligence
Test is more sensitive than the Stanford-Binet Test, especially
with left lobe damage. The Spearman’s G Test tests fluid
intelligence, or the capacity to solve new problems, and is also
sensitive to goal neglect.
Language
Language is a form of sequential behavior based on the exercise
of temporal function, and the cognitive functions that support
it (Fuster, 1997 p.166). Temporal integration is similar to
executive function in organizing temporally separate items,
except it does not need a central executive. The most well
known disorder is Broca’s aphagia, this is slow and effortful
speech lacking fluidity and continuity. Lesions to Broadman’s
area 44 and 45 produce this effect. Broca’s area is responsible
for the most elementary combination of morphemes, which are the
simplest units of language. The most anterior prefrontal cortex
mediates the elaborate structures of spoken language. For
prefrontals, difficulty exists in accessing verbs over nouns, as
well.
Emotions and Affect
Apathy, depression, and euphoria are associated with lesions.
Apathy results from extensive lesions to the prefrontal
convexity, and the medial area, as well as blunting of affect.
Depression results in damage to the anterior frontal lobe
(left), but depression could be secondary to awareness of loss
of cognition. Those who have achieved intellectual achievement
may be vulnerable, as well as those with family history.
Euphoria occurs from lesions to the orbital prefrontal cortex,
occurring sporadically, and resembling hypomania with
nervousness, irritability, and some paranoia. It is accompanied
by a childish, compulsive, shallow humor called moria, or
Witzelsucht.
Social and Emotional Behavior
Apathy and depression will adversely affect social contact with
isolation. On the other hand, euphoria can result in
disinhibition of instinctual drives, a loosening of moral
restraints, and a loss of capacity to gauge the effects of one’s
own behavior. This is similar to criminal sociopathy.
References:
Fuster, Joaquin, M.(1997). Human Neuropsychology.(3rd Ed.), The
Prefrontal Cortex Anatomy, Physiology, and Neuropsychology of
the Frontal Love.(pp.150-184). Philadelphia, NY: Lippincott-
Raven.
Levin, Harry, S. & Grafman, J.(2000). Neuroanatomic Basis for
Reorganization of Function After Prefrontal Damage in Primates.
(1st Ed). Cerebral Reorganization of Function After Brain Damage
(pp. 84-90). Oxford, NY: Oxford Press.
Kalat, James, W. (2004). Development of the Brain. (8th Ed.)
Biological
Psychology (pp. 111). Belmont, Ca: Thomas Learning, Inc.
Ruth, Ronald, M. and Barth, Jeffrey, T.(2000). Behavioral
Neuropsychology
Executive Function. Retrieved April 20, 2004 from Google:
http://nanonline.org/nandistance/mtbi/ClinNeuro/
executive.html
Shawnee Thayer
Psych 321
Lesions of the Prefrontal Cortex-
Perspective of a family member and employer
The prefrontal cortex is involved in a wide variety of
functions. It is known as the area of the brain which has
“executive control”, taking input from other areas of the brain
and combining and applying those functions (Kalat 2004).
Lesions to the prefrontal area can greatly impair overt behavior
of an inflicted individual. These deficits are dependent upon
the severity of the lesion and the specific region of the
prefrontal cortex in which the lesion resides (ventrolateral,
dorsolateral, orbitofrontal, and anterior prefrontal)(Eslinger
2003).
Individuals with prefrontal lesions usually display
emotional, social and moral deficits (Elinger 2003). Social
learning is impaired and adaptive learning does not appear to
extend beyond avoidance of punishment in most cases(Anderson
1999). Personality is marked by poor judgment, minimal insight
into/slight anticipation of consequence, a desire for autonomy
but a lack of self- initiation, lack of sense of competency,
lack of identity, a lack of relationship between self and others
and self and environment, and a deficit in motivation and goal
directed behavior(Eslinger 2003). Most cases do not appear to
experience anxiety or fear. These persons tend to be
egocentric, easily irritated, impatient, and display “shallow”
emotions(Trauner 2001). They cannot harness their emotions to
use in an adaptive manner regarding learning from experience,
and developing and maintaining relationships. Empathy, moral
decision making and comprehension are usually erratically rule-
based and self-serving. There is an inability to demonstrate
perspective taking and limited to no perception of social cues
and rules(Mah 2004).
People who suffer right hemisphere strokes can develop
difficulty comprehending or expressing emotional cues, such as
facial expressions, gestures, vocal intonation, and may be
indifferent to their disability (Trauner 2001). Persons with
left hemisphere lesions are often depressed and display
inhibition which includes apathy, flattened affect, withdrawal,
narrowing of interests(Trauner 2001). Patients with right or
left hemispheric lesions may experience disinhibition which
includes euphoria, impulsivity, and irritability, inappropriate
emotional responses and impaired judgment (Trauner 2001).
Intellectual capacities can remain preserved, and
individuals with prefrontal damage can score normal-average
intelligence on standard IQ tests (Eslinger 2003). Cognitive
deficits which do appear relate to attention, self-regulation,
inhibition, planning, problem solving, critical thinking,
organization, working memory, self-awareness and self-
monitoring, and goal-directed behavior (Eslinger 2003).
Available cases of early prefrontal cortex damage provide
evidence for the importance of this region in psychological
development (Eslinger 2003). Anderson (1999) discussed the
important cognitive and behavioral deficit differences between
childhood onset of prefrontal cortex lesions and adult onset
lesions to the prefrontal cortex. Adults who experience a
lesion to the prefrontal cortex have had years of normal
cognitive and social behavior development. A lesion to certain
regions of the prefrontal cortex will cause severe damage in
decision making abilities and social behavior, but patients tend
to retain intellectual abilities and preserve factual social
knowledge of relevant social conventions, rules and cues, even
if they find themselves unable to act on them (Anderson 1999).
Individuals with childhood-onset lesions show a degree of
cognitive alteration, ranging from moderate to severe (Trauner
2001). A child who has a lesion to the prefrontal cortex may be
unable to obtain the needed decision making abilities and social
knowledge because the region of the brain which helps them to
process that information is damaged (Anderson 1999). Because
damage to the prefrontal area impairs the ability for a person
to learn from experience, many children afflicted have developed
behavioral deficits despite a stable home life, family and
school peers to model appropriate behavior and behavior
modification programs aimed at correcting the “problem” behavior
in childhood and adolescence(Anderon 1999).
The behavioral deficits experienced by adult-onset and
child-onset prefrontal lesion patients appear similar, but
child-onset deficits are more severe. These individuals have a
greater tendency to display antisocial behavior like stealing
and violence (Anderson 1999). Without the years of socially
relevant knowledge to recall, child-onset patients are less
likely to experience any form of remorse. Adult-onset behavior
is more constrained, although acting impulsively and the
susceptibility to act on immediate cues leaves them at risk to
harm others (Anderson 1999).
Two “case histories” of fictional characters will
illustrate the behavioral deficits experienced by individuals
with prefrontal cortex lesions. The first history is told from
the perspective of a female sibling of a 15 year old female who
has a childhood onset prefrontal cortex lesion. The second
“case history” is told from the perspective of a social worker
who works with a 44 year old male with an adult onset prefrontal
cortex lesion. All the behaviors described follow closely
actual case histories of individuals with prefrontal lesions
found in research literature.
Case History #1
“CC is my 15 year old sister. When she was 15 months old
she was run over by a car but everyone thought she was ok. When
she was a toddler our parents had her checked out by doctors
because no matter how much they punished her, she didn’t seem to
care. When she was in middle school she was way unpopular. She
didn’t ever pay attention in class and would talk back to the
teacher when she was told to do something so she got in trouble
a lot. She would interrupt kid’s conversations a lot and
sometimes she would get too close to people when she talked.
When she got mad she would throw a tantrum. A few times when
she got mad she hit someone or broke something of theirs but she
was never sorry. She didn’t care. She was selfish and always
wanted things her way, or only saw things her way. Our mom told
me that she didn’t understand how other people felt and that’s
why she acts like that. She never cared whether or not she was
going to get in trouble. She didn’t even think about it. She
always just does what she wants at that second. A couple of
years ago she got caught stealing stuff from a couple of kids,
but she didn’t care. She just “wanted” what they had. She has
no idea when someone wants her to leave or when she hurts
someone’s feelings. It’s like she just doesn’t get it. She has
no friends and still gets into fights with adults. She lies a
lot, but a lot of times she is like bragging so I know she is
lying.”
Case History #2
“DT is a 44 year old male who obtained a MA in English and
Communication and before the lesion taught students full time at
a community college. Two years prior to illness he and his wife
agreed to a divorce so he moved into a villa. Until his illness
he was in good health. He told me that after his operation,
everything seemed fine for a while, and then he began to notice
changes in his personality. He told me that he couldn’t
concentrate and had depressive thoughts. He didn’t feel like he
had any initiative to accomplish anything, and felt generally
apathetic. He returned to his job part-time. He would “forget”
to prepare his lectures for class and began to “lose control” of
the teaching process and consequently lost his students
attention. He failed to perform his share of duties at the
villa and was asked to leave, so he moved into a one bedroom
apartment. He soon after had to leave his job because he was
unable to teach and was given disability for a while but due to
budget cuts he was forced to come to me in help finding work. I
was able to find him a job at an office but he was chronically
late and would “let down” appointments. He says he is aware of
missing appointments and being late and is ashamed of it, but he
“just doesn’t do it”. An increasingly sarcastic sense of humor
that was frequently ill-timed made him unpopular around the
office. He also has a habit of making other “inappropriate”
comments, but cannot seem to regulate himself from saying them.
His personal hygiene was and is below standards which he is
aware of but does not improve (he “just doesn’t”). He was soon
asked to leave that position. He has no plans of any kind for
the future, and doesn’t seem to think out any decisions. He
tells me he spends his time in his apartment, not doing much of
anything except watching TV.”
References
Anderson, Stephen W., Antoine B., Damasio H., Tranel D., Damasio
Antonio R. (1999). Impairment of social and moral behavior
related to early damage in human prefrontal cortex. Nature
Neuroscience,2(11),1032-1036.
Eslinger, Paul J., Flaherty-Craig, Claire V., Benton, Arthur
L. (2004). Developmental outcomes after early prefrontal
cortex damage. Brain and Cognition, 55, 84- 103.
Kalat, James W. (2004) Biological Psychology. Ontario, Canada:
Wadsworth.
Lawson, C. “Social Skills and School”
www.cdl.org/resources/reading_room/social_skills.html. May 3,
2005.
Mah, Linda, Arnold, Miriam C., Grafman, Jordan. Impairment of
social perception associated with lesions of the prefrontal
cortex. American Journal of Psychiatry, 161, 1247-1255.
Thimble, Michael.H. (1990). Psychopathology of frontal lobe
syndromes. Seminars in Neurology, 10(3).
Trauner, Doris A., Nass R., Ballantyne A.(2001) Behavioural
profiles of children and adolescents after pre- or perinatal
unilateral brain damage. Brain, Vol. 124(5), 995-1002.
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Copyright © 2005, Dr. John M. Morgan, All rights
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