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Discrepancy Between Cerebral Structure
and Cognitive Functioning
AReview
Michael Nahm, PhD,* David Rousseau, PhD,†‡ and Bruce Greyson, MD*
Abstract: Neuroscientists typically assume that human mental functions are
generatedby the brain and that its structuralelements, includingthe different cell
layersand tissues that form the neocortex, play specific roles in this complex pro-
cess. Different functional units are thought to complement one another to create
an integrated self-awareness or episodic memory. Still, findings that pertain to
brain dysplasia and brain lesions indicate that in some individuals there is a con-
siderable discrepancy between the cerebral structures and cognitive functioning.
This seems to question the seemingly well-defined role of these brain structures.
This article provides a review of such remarkable cases. It contains overviews of
noteworthy aspects of hydrocephalus, hemihydranencephaly, hemispherectomy,
and certain abilities of “savants.”We add considerations on memory processing,
comment on the assumed role of neural plasticity in thesecontexts, and highlight
the importance of taking such anomalies into account when formulating
encompassing models of brain functioning.
Key Words: Hydrocephalus, hemihydranencephaly, hemispherectomy,
savant syndrome, neural plasticity
(JNervMentDis2017;205: 967–972)
Although it is generally acknowledged that current neuroscientific
models are not sufficiently developed to explain every detail of
brain functioning, neuroscientists usually suppose that human mental
functions are created by the brain and its various macro- and micro-
structures, including the different cell layers of the neocortex. These ce-
rebral components form neuronal networks and circuits and are thought
to possess and to exert specific functions that complement one another
to generate an integrated self-awareness (Hart, 2016).
Nevertheless, several cases involving brain dysplasias (abnormal
cell development) and brain lesions (cell damage) indicate that large
amounts of brain mass and its organic structures, even entire hemi-
spheres, can be drastically altered, damaged, or even absent without
causing a substantial impairment of the mental capacities of the affected
persons. These exceptional individuals display a notable discrepancy
between the condition of their cerebral structures and the quality of
their cognitive functioning (e.g., Bell and Karnosh, 1949; Lorber, 1983;
Muckli et al., 2009; Treffert, 2010). In the following, we provide a re-
view of noteworthy cases that highlight this curiosity. We present over-
views of remarkable aspects of hydrocephalus (enlarged cranium due to
excess cerebrospinal fluid pressure), hemihydranencephaly (HHE)
(complete or near-complete unilateral absence of the cerebral cortex),
and hemispherectomy (surgical removal of one cerebral hemisphere),
as well as of notable skills of some savants (persons with profound bril-
liance in certain areas of cognition, often accompanied by significant
cognitive disability in other areas). Finally, we will discuss the ques-
tions these findings pose for the commonly assumed models of brain
and memory functioning and for the assumed role of neural plasticity
in these circumstances.
REMARKABLE DISCREPANCIES BETWEEN CEREBRAL
STRUCTURE AND COGNITIVE FUNCTIONING
Remarkable Aspects of Hydrocephalus
In this first section, we will present a short overview of remark-
able hydrocephalus cases, in which the mental faculties and, some-
times, the motor faculties of the individuals are prima facie surprising
given the degree of their hydrocephalus. In one of the earliest reports
of such a case, Martel (1823) described a boy who died at the age of
10. During the first years of his life, he seemed healthy, but eventually,
his health deteriorated considerably. He had severe headaches, gradu-
ally lost all his senses except hearing, developed fits, and became con-
fined to his bed, but he nevertheless seemed mentally unimpaired until
his death. His head appeared enlarged, and upon autopsy, apart from
“residues of meninges,”“no trace of a brain”was found inside the skull
(Martel, 1823, p. 20).
More recent cases were uncovered and documented by Lorber,
who specialized in treating children with hydrocephalus and/or spina
bifida. When assessing the IQ of his patients, he used the Wechsler In-
telligence Scale for Children, and with adults who agreed to retesting,
he used the Wechsler Adult Intelligence Scale. The most remarkable
and well-known case concerns a highly intelligent student of mathemat-
ics (Lorber, 1978; Lonton, 1979) who received worldwide attention due
to an article published in Science (Lewin, 1980) that drew attention to
some of the most remarkable cases that Lorber studied.
The aforementioned student of mathematics had a global IQ of
130 and a verbal IQ of 140 at the age of 25 (Lorber, 1983), but had “vir-
tually no brain”(Lewin 1980, p. 1232). Still, the student apparently de-
veloped normally throughout his childhood. Judging from photographs
in his family album, he did have hydrocephalus from early in life, but it
was not diagnosed and thus not treated. At the age of 20, he sought
medical advice becauseof problems of endocrine maturation. Up to that
time, he had not had seizures and he had no motor handicap. Similarly,
his vision was perfect apart from a refraction error. Nevertheless, later
studies showed the apparent absence of a visual cortex, and from the
age of 23, he became subject to occasional grand mal seizures. He
was featured in a documentary film about Lorber's work in 1982, in
which he appeared behaviorally normal (Lawson, 1982). This student
belonged to the group of patients that Lorber classified as having “ex-
treme hydrocephalus,”meaning that more than 90% of their cranium
appeared to be filled with cerebrospinal fluid (Lorber, 1983).
Of the 687 patients whose brains Lorber scanned, 16 persons
belonged to this group, and half of them were regarded as cognitively
*Division of Perceptual Studies, Department of Psychiatry and Neurobehavioral Sci-
ences, University of Virginia Health System, Charlottesville, Virginia; †Centre
for Systems Philosophy, Surrey; and ‡Centre for Systems Studies, University of
Hull, Hull, East Yorkshire, UK.
Send reprint requests to Bruce Greyson, MD, Division of Perceptual Studies,
Department of Psychiatry and Neurobehavioral Sciences, University of Virginia
Health System, 210 10th Street, NE, Suite 100, Charlottesville, VA 22902–4754.
E‐mail: cbg4d@virginia.edu.
Copyright © 2017 Wolters Kluwer Health, Inc. All rights reserved.
ISSN: 002 2-3018/1 7/20512–0967
DOI: 10.1097/NMD.0000000000000752
REVIEW ARTIC LE
The Journal of Nervous and Mental Disease •Volume 205, Number 12, December 2017 www.jonmd.com 967
Copyright © 2017 Wolters Kluwer Health, Inc. All rights reserved.
normal—that is, they had an IQ of 100 or more (Lewin, 1980; Lorber,
1983). He classified patients whose cranium appeared to be filled with
cerebrospinal fluid to a degree of 50% to 90% as having “gross hydro-
cephalus”and included details regarding the most remarkable cases in
an article (Lorber, 1983). Apart from the above-mentioned student of
mathematics, he described a woman with an extreme degree of hydro-
cephalus showing “virtually no cerebral mantle”who had an IQ of
118, a girl aged 5 who had an IQ of 123 despite extreme hydrocephalus,
a 7-year-old boy with gross hydrocephalus and an IQ of 128, another
young adult with gross hydrocephalus and a verbal IQ of 144, and a
nurse and an English teacher who both led normal lives despite
gross hydrocephalus.
Lorber stressed that the heads of the patients with hydrocepha-
lus, including thosewho had a high IQ, usually had an enlarged circum-
ference and that in these cases, the brain volume would probably be
greater than the thinness of the cerebral mantle would suggest. Conse-
quently, Lorber attempted to determine the brain volume of the patients
with hydrocephalus using a method that seemed to provide realistic es-
timations (Jackson and Lorber, 1984). Regarding cases of extreme
hydrocephalus, the brain volume of the mathematics student was
determined to be 56% of the normal value. For the girl with an IQ of
123 (case 4(a) in Lorber, 1983), it was rated about 61% of normal.
Regarding six cases with gross hydrocephalus, the calculated brain
volumes were between 70% and 90% of the median. The authors
concluded that although their data “indicated that there is more brain
mass even in very severe hydrocephalus than the ventricular enlarge-
ment suggests, it is worth considering that the measurements include
supratentorial structures other than the hemispheres,”suggesting that
the volume of the hemispheres alone was reduced to a greater extent
(Jackson and Lorber, 1984, p. 93).
Lorber (1983) also drew attention to two other groups of patients
with hydrocephalus he considered remarkable. The first of these two
groups group consisted of 54 patients who showed an extreme congen-
ital hydrocephalus in infancy (showing a cerebral mantle of 10 mm or
less). The brains of 21 of these children regenerated completely after
being shunted, showing no sign of hydrocephalus subsequently. For ex-
ample, a boy whose cerebral mantle measured 3 mm at the age of
7 weeks developed normally and had a global and verbal IQ of 135 at
the age of 10. The boy was doing exceptionally well in school and
attended a class with children who were 3 years his senior. Remarkable
cases in which the extreme hydrocephalus did not resolve completely
include a baby whose cerebral mantle measured less than 5 mm at
3 weeks of age. At the age of 18, he still showed moderate hydroceph-
alus, but his global IQ was 121. However, the extreme congenital hy-
drocephalus of an otherwise physically normal girl barely changed
over time. At the age of 18, she still had gross hydrocephalus but had
an IQ of 115. In the two latter cases, it was established that the blood
supply of the existing brain tissue was substantially reduced compared
with what would be expected in normal circumstances. Such a reduced
blood supply, and thus correspondingly reduced oxygen supply, was
also reported for the student of mathematics.
The second group comprised patients with grossly asymmetrical
hydrocephalus. In some of these cases, one ventricle was normal and
the other grossly dilated. Nevertheless, some of these patients did not
show the typical signs of paralysis or spasticity on the contralateral side
of the body. In this context, it is also of interest that Lorber (1965) re-
ported a seemingly inexplicable case of supposed hydranencephaly
(HE). In contrast to hydrocephalus, in which the brain hemispheres
are pressed toward the cranium and can become extremely thin, HE
is characterized by the absence of hemispheres (see also below). How-
ever, it later turned out that the boy concerned must have had very ex-
treme hydrocephalus during his early years rather than HE (case 2(c)
in Lorber, 1983; see also Shewmon et al., 1999, p. 372, who seemed
unaware that this case was followed up by Lorber). After a shunt treat-
ment, the boy's right hemisphere regenerated fully, whereas the left
hemisphere still showed gross hydrocephalus. He showed no hemiple-
gia (paralysis of one side of the body), but he had a global IQ of only 66.
After these publications, Lorber co-authored an article describ-
ing three children with gross hydrocephalus who, respectively, had ver-
bal IQs of 77, 82, and 92 (Berker et al., 1992). More recently, other
remarkable hydrocephalus cases were reported. A well-known case
was described by Feuillet et al. (2007). The degree of this man's hydro-
cephalus would most likely be classified as extreme or very gross in
Lorber's system. His neurological development and medical history
were otherwise normal. He married, had two children, and worked as
a civil servant. He had a global IQ of 70, a verbal IQ of 84, and a per-
formance IQ of 70. However, no further details on his brain structure
and cognitive abilities were provided.
Another interesting case is that of a 44-year-old woman with very
gross hydrocephalus described by Masdeu (2008) and Masdeu et al.
(2009). She had a global IQ of 98, worked as an administrator for a gov-
ernment agency, and spoke seven languages. In Leipzig, Germany, staff
members of the Max Planck Institute for Human Cognitive and Brain
Sciences recorded a similar case. A man was examined because of his
headache, and to his physicians' surprise, he had an “incredibly large”hy-
drocephalus. Villinger, the director of the Cognitive Neurology Depart-
ment, stated that this man had “almost no brain,”only “a very thin layer
of cortical tissue.”This man led an unremarkable life, and his hydro-
cephalus was only discovered by chance (Hasler, 2016, p. 18).
An alleged additional case of severe hydrocephalus with nor-
mal intelligence was published by de Oliveira et al. (2012). This case
was cited in at least four sources as a second recent example of this
phenomenon, in addition to the case reported by Feuillet et al.
(2007) (see Forsdyke, 2014, 2015a, 2016; Rudrauf, 2014). However,
the publication by de Oliveira et al. (2012) has been retracted, as it
seemed to have described the same individual previously reported
by Feuillet et al. (2007).
Remarkable Aspects of HHE
A class of brain anomalies related to hydrocephalus is HE, which
differs from extreme hydrocephalus cases by the absence, rather than
the compression, of the hemispheres. Nevertheless, in these cases, rudi-
mentary bits of cortical tissue can be present. In HE, consciousness is
severely impaired and often barely recognizable. Nevertheless, there
are cases in which a surprising amount of discriminative awareness
can be detected in subjects with HE. It is assumed that the remaining
brain structures, such as cortical remnants and the brainstem, are re-
sponsible for their consciousness (Merker, 2007; Shewmon et al.,
1999). Hemihydranencephaly is a related, but much rarer, condition in
which only one hemisphere is almost or completely lacking, whereas
the meninges, basal ganglia, pons, medulla, cerebellum, and falx are
preserved (Pavone et al., 2013). The cause of HHE is generally thought
to be a unilateral vascular disruption in early developmental stages of
the brain. In the following, we will briefly introduce examples of pub-
lished HHE cases in which this drastic brain dysplasia, resulting in
the loss of one entire brain hemisphere, was not accompanied by a cor-
responding impairment in the patients' mental or motor functions.
Greco et al. (2001) described a boy who had both HHE and hy-
drocephalus. He showed right-sided hemiparesis and other signs of neu-
ronal dysfunction, including a low cognitive potential. Nevertheless, by
the age of 12 he attended a junior high school and did well with the sup-
port of a teacher (Pavone et al., 2013). Ulmer et al. (2005) presented a
case of a 36-year-old man who was examined because of left-sided
headache. It was found that his left hemisphere was almost completely
lacking. The patient reported some disabilities in his right hand con-
cerning fine motor tasks, but his intellect and language abilities were
unimpaired, and he was working in a security department. Balpande
et al. (2009) described a 13-year-old boy whose brain scans showed a
nearly complete absence of the right cerebral hemisphere, including
Nahm et al. The Journal of Nervous and Mental Disease •Volume 205, Number 12, December 2017
968 www.jonmd.com © 2017 Wolters Kluwer Health, Inc. All rights reserved.
Copyright © 2017 Wolters Kluwer Health, Inc. All rights reserved.
its basal ganglion. Nevertheless, the boy's sensorimotor and language
development during childhood was not restricted, and he attended a reg-
ular school as an average student. Similarly, Muckli et al. (2009) de-
scribed a 10-year-old girl who lacked the entire right cortical
hemisphere. The loss of this hemisphere was discovered when she
was 3½years old and underwent an magnetic resonance imaging scan
because of brief, involuntary twitching on her left side. Nevertheless,
she successfully attended a regular school and mastered activities that
require bilateral coordination, such as roller skating and bicycle riding.
In general, it is assumed that the remarkable capacity of the hu-
man brain to compensate for the loss of an entire cerebral hemisphere is
mediated via neural plasticity and that this compensation begins at early
stages of fetal development (Balpande et al., 2009; Pavone et al., 2013).
This view is supported by the fact that apart from HHE, there are also
other pathological conditions in which large parts of one hemisphere
are missing or severely damaged from childhood, but which do not
seem to have a notable effect on the intellectual capacities of the sub-
jects. For example, Baudoin (1996) described the case of a 30-year-
old woman who had a large lesion on her right cerebral hemisphere.
The right occipital and parietal lobes were entirely missing, as well as
the inferior part of the right temporal lobe. The brain lesion was discov-
ered only because of the patient's first seizures at the age of 30. Simi-
larly, Duyff et al. (1996) presented the case of a 32-year-old lawyer
whose brain showed a large arachnoid cyst in the right frontotemporal
region that had displaced (or replaced) the temporal lobe and parts of
the frontal and parietal lobes. His development had been completely
normal, and no abnormalities were discovered upon neurological exam-
ination. His condition was discovered only because he had a persistent
headache after a skiing accident in which he had fallen on his head.
Remarkable Aspects of Hemispherectomy
In the cases described in the previous section, people who grew
up with only one hemisphere developed all the neuronal foundations
needed for ordinary cognitive and most motor skills. Even so, it seems
additionally surprising that one hemisphere can accomplish this after
the other has been removed or was isolated anatomically and function-
ally from the rest of the brain, as it is the case of surgical hemispherec-
tomy. The first series of hemispherectomies was described by Dandy
(1928) for malignant glioma. Since then, the technique has evolved,
and it is still applied, especially for treating forms of epilepsy in which
epileptic discharges disrupt the damaged hemisphere and interfere with
the function of the normal hemisphere to a very severe degree (e.g.,van
Schooneveld et al., 2016). Although most hemispherectomies are per-
formed on young children, adults are also operated on with remarkable
success (e.g., Bates and Zadai, 2003; Bell and Karnosh, 1949;
McClelland and Maxwell, 2007; Schramm et al., 2012).
It is astonishing that many patients can lead an ordinary life after
this drastic procedure, having only minor motor disabilities that result
from mild hemiplegia. Physicians have long wondered about the sur-
prising finding that one can lead a normal life with only one hemi-
sphere. For example, McFie (1961) was astonished that “not only
does it perform motor and sensory functions for both sides of the body,
it performs the associative and intellectual functions normally allocated
to two hemispheres”(p. 248). Moreover, physicians noted decades ago
a greater improvement of the patient's condition when the entire hemi-
sphere was removed rather than only parts of the damaged area, even if
the remaining cortex appeared normal (McFie, 1961).
The discrepancy between cerebral and cognitive functioning in
these cases is strikingly highlighted by the fact that most patients, even
adults, do not seem to lose their long-term memory such as episodic
(autobiographic) memories. Even so, this puzzle, and possible explana-
tory models for this retention of long-term memory, is only rarely
discussed in the medical literature dealing with hemispherectomy. Al-
though memory features are sometimes assessed by using the Wechsler
Memory Scale (e.g., Loddenkemper et al., 2004), we were unable to
find a single peer-reviewed publication in which the peculiar retention
of the patient's autobiographic memory was explicitly addressed. That
said, this remarkable phenomenon was at least casually mentioned by
authors such as Dandy (1933) and Bell and Karnosh (1949), who stated
that their patient's memory seemed unimpaired after hemispherectomy.
Similarly, Vining et al. (1997) were surprised by the apparent retention
of memory after the removal of the left or the right hemisphere of their
patients. Dorman (1991) described the extraordinary case of a subject
who was able to perform brilliant calendar calculations, although his
left hemisphere had been removed several years before. Dorman related
this case to those of other savants who, in comparison, usually perform
their tasks with two hemispheres.
Although there is no established explanatory model for the
retained memory after hemispherectomy, a suggestion was sketched
in an interview with Freeman, available on the Internet, which proposed
that memory is stored in both hemispheres, so that it is retained when
one hemisphere is removed (Zuger, 1997). It seems, however, that this
proposition is not an accepted hypothesis for explaining the storage
and recall of autobiographic memory. Numerous studies suggest that
encoding memories involves diverse areas of the brain, forming func-
tional neuronal circuits especially between the hippocampus and the dif-
ferent cortical regions (for a review and further references, see Tonegawa
et al., 2015). In particular, certain kinds of memory seem to depend on
regions specific to one of the two hemispheres. For example, the right
temporofrontal cortex seems crucial for recalling episodic memories
(Calabrese et al., 1996), whereas the prefrontal and temporal regions
of the left hemisphere seem to mediate retrieval of (context-free)
“world”knowledge (Markowitsch et al., 1999). It is noteworthy that
up to the present, no such specific memory deficits have been reported
after hemispherectomies.
It might be possible that memories cease to be stored in the hemi-
sphere that is affected by severe diseases like tumors or encephalitis
such as Rasmussen's disease and that previously encoded memories
are transferred from the affected hemisphere to the healthy hemisphere.
As a result, the memories would be retained after the removal of the
damaged hemisphere. However, apart from the lack of evidence for
such processes, patients who underwent a hemispherectomy state that
only memories from the time immediately before the operation are
missing (if any are missing) (Traufetter, 2003). This evidence appears
incompatible with the transfer of memories from a diseasedhemisphere
to a healthy one.
Moreover, both of these explanatory models fail to account for
individuals who had a sudden unilateral brain lesion that resulted in
very severe amnesia. A well-known case of this sort concerns the Rus-
sian soldier Lyova Zazetsky, who sustained a considerable brain lesion
in the left parieto-occipital area in combat (Luria, 1972). At first,
Zazetsky had no memories at all. During a consistent, 25-year-long
struggle to regain his identity, he managed to retrieve several memories,
but they predominantly concerned his childhood. A logical question
that arises as a consequence from the earlier observations is whether
Zazetsky could have had better access to his memories if his left hemi-
sphere had been completely removed.
Remarkable Aspects of the Savant Syndrome and
Memory Processing
Finally, we will present additional considerations about mem-
ory processing, especially in savants. In this respect, Kim Peek
(1951–2009) was most remarkable in that he seemed to possess a per-
fect memory: he forgot nothing he ever read and remembered com-
plete melodies, even if he heard them only once. Most remarkably,
his brain showed considerable malformations that included a deformed
cerebellum, abnormalities of the left hemisphere, and the complete lack
of the corpus callosum, as well as the anterior and posterior
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commissures. In addition, much of the skull interior comprised empty
areas that were filled with cerebrospinal fluid, as in hydrocephalic sub-
jects (Treffert and Christensen, 2005). Nevertheless, he memorized more
than 12,000 books, apparently verbatim, the contents of which
amounted to an encyclopedic knowledge in multiple areas of interest.
Typically, he would read a page in eight to ten seconds, and then turn
to the next page. He even read two pages of smaller books such as pa-
perbacks simultaneously, using one eye each for each page. Moreover,
he had impressive calendar calculating abilities (Treffert, 2010).
One may wonder about a plausible neural mechanism to explain
Peek's ability to remember practically everything. For example, it is
known that brain cells and neuronal circuits undergo characteristic activ-
ities during memory encoding (e.g., Tonegawa et al., 2015) and that the
transfer of the contents of short-term memory (sometimes also termed
“working memory”) into long-term memory is accompanied by the syn-
thesis of new proteins (e.g., Buffington et al., 2014). Many of these find-
ings are derived from conditioning studies performed with animals.
Nevertheless, it remains uncertain whether such studies can satisfactorily
explain long-term memory storing and processing in humans, especially
in savants such as Peek. In his case, everything he ever read was imme-
diately encoded in a long-term memory reservoir, seemingly bypassing
selection mechanisms of short-time memory processing.
Certain musically gifted savants display similarly perplexing
abilities. For example, blind pianist Thomas Berthune (1849–1908)
was able to repeat even complex and long piano pieces without mistake
after a single hearing, just as was blind Leslie Lemke (born in 1952)
100 years later. Every chord and note of every piece they heard were in-
delibly imprinted in their minds. Neither had had a single piano lesson
in his life (Treffert, 2010). At present, there does not seem to be a con-
vincing hypothesis that could explain how all these linguistic and musi-
cal phrases were permanently and instantly stored in the long-term
memory of Peek, Berthune, or Lemke—to name only a few such sa-
vants. For example, the synthesis of new proteins takes seconds to
minutes, and it can thus not account for the prompt and perfect re-
production of previously unknown piano pieces. Regarding the molec-
ular processes involved in short-term memory or working memory
encoding, not much is known at present. It seems that the release of cal-
cium at synapses plays a crucial role (Mongillo et al., 2008). On a more
general level, Snyder (2009) suggested that savant skills are latent in
us all but that they typically stay inaccessible during the normal func-
tioning of cognitive brain processes. Nevertheless, as indicated above,
it remains unknown how the barrier to savant skills can be overcome,
especially on a neurophysiological level, and Snyder regard his prop-
osition only as a hypothesis that needs yet to be proven. How activated
circuits of neurons, being under constant input stimuli, can mediate
the perfect memorizing of every single piano note heard is still
essentially unknown.
This is an important issue because, as Treffert noted, no model of
brain function, in particular with regard to memory, will be complete
until it can account for these remarkable feats (Treffert, 2006, p. 3). This
appraisal is, of course, also valid for memory processing with only one
hemisphere. Moreover, it is important to recall that the fundamental ques-
tion of how biochemical reactions of molecules and electrical activities
of neurons are translated into self-conscious experience, including au-
tobiographical memory, intentionality, and volition, is still unsolved
(e.g., Bennett and Hacker, 2003; Gauld, 2007; Majorek, 2012).
DISCUSSION
In the previous sections, we presented summaries of peculiar
medical findings that exemplify remarkable discrepancies between ce-
rebral and cognitive conditions of patients with hydrocephalus, HHE,
hemispherectomy, and savant syndrome. In the following, we will pres-
ent reflections by clinicians on the potential relationship between the
developmental status of the brain and cognitive abilities.
Regarding hydrocephalus, Lorber stressed that the brain of a baby
can sometimes regenerate from almost nothing to normal, provided the
increased intracranial pressure can be reduced to almost normal in early
infancy (Lorber, 1983). It might indeed be the case that most neurons of
the brain are still present even in severe hydrocephalus, despite being
stretched or damaged by the pathological cranial conditions and the di-
minished blood flow in these tissues (del Bigio, 2010). This might facil-
itate the remarkable regeneration of the hemispheres and their
functioning after shunt treatment. Indeed, in a sample of children with
hydrocephalus, the degree of global cortical thinning during the first
months of life before a shunt treatment was not related to the children's
subsequent intelligence (Dennis et al., 1981).
Similarly, in patients with grossly asymmetrical hydrocephalus,
a reorganization of the better-developed brain parts might take over
the functions of the damaged or absent structures. Lorber invoked find-
ings pertaining to hemispherectomy to support this view, stressing that
an infant rat's behavior would, several weeks after hemispherectomy,
be indistinguishable from that of normal rats (Lorber, 1983). Indeed,
humans can also recover to an almost normal condition after hemi-
spherectomy, especially with regard to their mental faculties, and even
redevelop their language center if it was removed or disconnected dur-
ing the surgical operation. In general, these processes of reorganization
work better and faster the younger the patient is, and they are attributed
to the formation of new synaptic circuits due to the brain's neural plas-
ticity (Huttenlocher, 2002), even though the specific mechanisms in-
volved remain obscure.
Lorber stressed that the imbalance between the brain size and
structure of several of his patients with hydrocephalus and their perfor-
mance should be regarded as the first step in the rethinking of some
aspects of neuroanatomy and neurology, and he recommended future
in-depth investigations (Lorber, 1983, p. 12). As of today, however,
we have only a few narrowly focused studies (Masdeu, 2008; Masdeu
et al., 2009), and no in-depth investigations along the lines suggested
by Lorberhave been undertaken. Clearly, the macro- and microanatomy
of the brain and its tissue layers differ drastically in people with severe
hydrocephalus compared with people with normally developed brains.
For example, brain structures such as the thalamus, the amygdala, and
the corpus callosum were not visible at their usual positions inthe scans
obtained from the patient described by Feuillet et al. (2007), but were
most likely pressed toward the cranium together with the layers of the
cortical mantle (Pelletier, 2008). Often, these malformations result in
impaired mental and motor skills, as should be expected, but this is
not always the case.
This raises interesting questions about how important the usual
anatomy of the brain and its cellular layers really is. It still needs to be
determined according to which principles the involved synapses, cells,
and tissues of the brain successfully organize their fine-tuned neural cir-
cuits under such abnormal anatomical and physiological conditions.
This problem is even more apparent after hemispherectomies in which,
for example, the language center was removed along with the mal-
functioning hemisphere. Assuming that a given brain structure dictates
the mental capacities of the individual, it remains difficult to explain
how the remaining brain structures and their neural activities can
“know”that a “language center”is missing now, and how these neurons
induce and guide its duplication in their own hemisphere. Majorek
(2012) argued that this activity requires the existence of a higher control
center that would be able to detect this gap in function and to initiate
steps that lead to its mending. He stressed that so far, the existence of
such a control center in the brain has not been reported and that, given
the decentralized organization of the brain, it would be difficult to imag-
ine where such a control center could be located.
Indeed, one might wonder whether such processes of reorganiza-
tion are purely self-organizing processes of neuronal tissue in response
to external stimuli, or whether the mind or “the self ”actively partici-
pates in these processes. Several studies suggest that the brain can
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indeed be altered by mental stimuli and processeson the molecular, cel-
lular, and neural circuit levels. In a review focusing on neuroimaging
studies, Beauregard (2007) summarized examples of mental influence
on brain structure from research into emotional self-regulation, psycho-
therapy, and placebo experiments. He concluded that these studies
strongly support the view that thoughts, feelings, beliefs, and volition
do exert a causal influence on brain plasticity, and he pointed to the ob-
vious fact that mental causation is an essential ingredient for successful
therapies. This is, of course, also valid for patients who train to regain
lost faculties after strokes, hemispherectomy, or brain injuries. The de-
gree of success in rewiring the brain is clearly dependent on the patients'
volition and purposeful training. According to Beauregard (2007), such
findings call into question positions in which all mental processes are
thought to be entirely reducible to biochemical processes.
In sum, the relation between the brain's structure and its functional
capacities, and the principles that govern neural rewiring processes after
or during developmental damage are still poorly understood. The cases
presented in this article highlight that there is still much to learn about
“the brain and its self”(Knoll, 2005) from a neurobiological perspec-
tive. On the basis of the different cases of discrepancy between cerebral
and cognitive functioning discussed in the present article, some authors
doubt that the brain serves as a comprehensive memory store, arguing
that its function more closely resembles a receptor or transmitter of
memory and allied cognitive processes (e.g., Forsdyke, 2009, 2015a,
2015b; Kelly et al., 2007, 2015).
CONCLUSION
Remarkable discrepancies between cerebral and cognitive condi-
tions of some patients with hydrocephalus, HHE, hemispherectomy,
and savant syndrome illustrate complexities of the neurobiological un-
derpinnings of cognition. We hope that this articlewill stimulate further
research into extraordinary cases of discrepancy between cerebral con-
ditions and mental functioning. It is research into such extraordinary
phenomena that may push scientific exploration into as yet underre-
searched topics, as well as raising important questions related to re-
search concerned with the function of normal brains.
DISCLOSURE
This work was supported by a research grant from the Society for
Psychical Research.
The authors declare no conflict of interest.
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