Savant syndrome: islands of genius in a sea of low intelligence
T. KODJAPASHI*, S.J. BALOYANNIS**
*Μedical Graduate of Aristotle University of Thessaloniki
**MD, PhD Director of A' Department of Neurology, Aristotelian University, (AHEPA HOSPITAL) Thessaloniki, Greece
The aim of this article is to analyze a rare, extraordinary condition, the savant syndrome. Savant syndrome is a clinical entity in which individuals with mental retardation demonstrate some special abilities. These "savant skills, (islands of genius)" concern concrete categories including music performance and composition, art (drawing, painting, sculpting), calendar calculating, mathematics, mechanical or spatial skills, prodigious language (polyglot) facility, synesthesia and are always accompanied by massive memory. According to the latest findings, savant syndrome can be congenital (associated with 15q11-q13) or it can be acquired following CNS injury, disease such as autism, epilepsy, frontotemporal dementia, visual impairment, stroke e.t.c. There are three types based on the level of the skills, the splinter skills where the level of the skills is appreciably above the general level of functioning but common in healthy population, the talented savant with a range of abilities occasionally founded in non-disable people, accompanied with a general low level of intelligence and prodigious savant with remarkable skills at levels beyond the accomplishments of even the cleverest human. Most people are aware of the existence of savant syndrome through Kim Peek, the mega-savant who was the inspiration for the movie Rain Man. A broad range of theories have been offered attempting to explain the development of such abilities. The conclusion proposed is that the emerge of savant skills is uncovered or revealed after damage to areas of the left hemisphere and right hemisphere compensation. This theory is vindicated, as the skills most often seen in the syndrome, tend to be right hemisphere in type and are released from the intendance of the injured left hemisphere. There seems to be a male predominance due to increased sensitivity of the left hemisphere to testosterone, which affects its development, during fetal life. Observing the syndrome from a neurobiology approach, excitatory or inhibitory neuron defects, influence the normal neuron-signal processing. The typical brain compresses the neural signal of an image to a few terms and silences the neurons encoding the details in the signal through inhibitory factors (GABA). Contrarily, savants’ brain does not work with a compress representation of a few blocks but with the entire neural signal due to abnormalities of the inhibitory system, resulting to the incredible levels in accuracy in their skills. In addition, it is assumed that serotonin deficiency may contribute to the disarray of the brain and the reveal of these special skills. But undeniably, the key to the explanation of the whole condition is hidden within the neurotrophic factors. This family of growth factors, especially the Brain-derived neurotrophic factor (BDNF), are involved in the growth, differentiation and viability suspending the apoptosis of neurons and accelerating the death in case of unfeasible survival. They also promote the synaptic communication and in extension the arise of savant skills by succouring the development of new synaptic relations after neural damage. Can we all have privileged access to these levels of information? Surveys have proved that savant brain processes occur in each of us but are overwhelmed by more sophisticated conceptual cognition. Scientist have managed to temporarily induce enhanced perceptual abilities in healthy volunteers, through application of repetitive Transcranial Magnetic Stimulation (rTMS), by immobilizing portions of left hemisphere function. Yet, a lot of information remain to learn not only for the syndrome itself, but also intriguing data regarding brain function, neural plasticity, compensation, recruitment, repair. The mystery of savant syndrome is indisputably a challenge for our current neuroscience capabilities and an opportunity of awareness about who we are and what we are capable of. Encephalos 2011, 48(3):93-102.
Key words: Cortical function, genius, mental retardation.
The term syndrome of "wise man" (savant syndrome) is used in order to describe an infrequent, extraordinary situation at which individuals with mental insufficiencies express exceptional mental faculties (island of genius). The individuals that present this syndrome are mainly autistic but have been reported also cases of individuals after a CNS injury or an illness. The original term was 'idiot savant', whose prefix indicates low intelligence, while the second (from the latin word sapiantia and sapere) means knowledgeable or wise, to describe someone who has an extreme memory. The term is rarely in use today and has been replaced by the term savant syndrome, and the affected person is called “savant”. An autistic who has this syndrome is called autistic savant. It is particularly noticeable the fact that every 'genius' skill is accompanied by a strange giant memory, despite a very low IQ (IQ 40-70 - cases over 114 have also been reported). This syndrome is not only a subject of research for every neuroscientist, and was a source of inspiration for film making (Rain man, Cube, Mozart and the Whale, Mercury Rising, Elling) but also influenced the literature (Funes, the Memorious by Jorge Luis Borges, Johnny Mnemonic of William Gibson, The Curious Incident of the Dog in the Night-time in Mark Haddon). In addition, the neurologist Oliver Sacks in his writings in the form of the novel refers to savant syndrome.1 Dealing with this syndrome undoubtedly raises many questions about how the brain works, the only 'in the image and likeness' organ.
Over three centuries have passed since the first syndrome's description in a German scientific journal of the time (Gnothi Sauton). It was then indicate the case of Jedediah Buxton, a pesron who performed complex arithmetic with lightning speed.
In 1789, the father of American psychiatry Benjamin Rush, described the clinical case of Thomas Fuller, who although not able to measure the numbers verbally, give answers to complex math problems. When asked how many seconds a man lived a man who is 70 years, 17 days and 12 hours, answered properly 2,210,500,800 in 90 seconds, putting in his calculations and 17 leap years!!2
A landmark point was the contribution of J. Langdon Down in 1887, where he presented 10 cases during the 30-years of his clinical experience. He recorded all his observations in his book ‘On Some of the Mental Affections of Childhood and Youth’, where he first introduced the term idiot savant-cause of which he had been criticized many times. The Down, as it turned out to be almost a century ahead of his time, classified the mentally retarded into 3 categories: genetic (Congenital) through which genes inherited intellectual disability, traumatic (Accidental) after injury, disease in pregnancy, during birth onwards. The third category included patients who did not meet the criteria for inclusion in the two previous categories. In this particular category, children expressed extreme difficulty in learning the language, developing social skills and interpersonal relationships with other people. They made stereotyped, bizarre movements, closed in themselves and manifested an indifference and lack of responsiveness to the environment, while natural-physical characteristics of the first two categories were absent. Because the symptoms started after the birth, was named Development (Developmental) and it is forerunner of the current developmental disorder syndrome of autism. Beyond these, Down distinguished the difference between early and late onset of this developmental disorder, laying in this way the foundations for subsequent named Late-Onset Autism with Regression and Early-Onset Autistic Disorder. Among patients in the latter category, some had special art, arithmetic, musical skills, which spurred the interest of the scientist in order to present them in the medical community in London. Each of these skills was always accompanied by an ability to memorize vast amounts of data.3
In 1914, Tredgold presented 20 cases of patients with a range of unique capabilities, such as they have been characterized in the syndrome.
In 1978, Rimland published a poll where from total 5400 autistic children, 531 of them manifested strange possibilities as described the syndrome.
Leo Kanner, a psychiatrist and researcher who devoted his life studying autism, reported 6 cases of children suffering from early onset autism (Early Infantile Autism) with incredible abilities in music and memorization.
Horwitz reported the remarkable case of monozygotic twins who, although not able to solve simple arithmetic operations, responded well to complex calculations with 20 digit numbers. They could even anticipated days in any calendar year in a range of 40 000 years and remembered the weather for each day of their adult life.2
Today the name of Darold Treffert is associated with savant syndrome. Treffert is professor of psychiatry at University Clinic of Wisconsin in the U.S.A. He has started his research in 1962 when he first met a savant. In his biography, as his prime research object is the savant syndrome, we can enumerate several publications, articles in journals, books (Extraordinary People, Islands of Genius), lectures and as well as he consulted in the creation of Rain Man, a film based the life of Kim Peek, a savant.4
The syndrome, depending on the skill level is divided into 3 categories:
The special skills of savants as mentioned in bibliography are categorized by content:
Pathological populations we meet in savant syndrome
According to Treffert studies, 1 in 10 autistic manifests savant skills and from the whole set of savants, 50% ail with autism. Autism is a neurodevelopmental disorder characterized by stereotyped behavior, severe delay in development of speech/talk, remaining social contact, and general lack of communication with the external environment. Two theories have been developed to justify the prevalence of the syndrome in autistic disorder. The first one supports that the development of specific skills of savants is closely connected with an identological, obsessive, self-limiting behavior of elements found also in autism. Because of the fixation on particular behavior-interests, conditions of hyperactivity in brain regions are being created, causing the emergence of separate skills. The second theory holds that reduced synthesis of cognitive information (weak central coherence) observed in autism leads to more primitive forms of memory (implicit memory) and predisposes to the development of savant skills. Neuropathological studies showed decoupling in neural networks between the anterior and posterior cortical areas in autism resulting lack of coordination in information processing by the networks of the brain. Therefore, the deficit on cognition functioning creates a suitable background for displaying unusual abilities.9
Cases with savant skills are mentioned by Miller (1998) in patients suffering from frontotemporal dementia. Patients within the onset and progression of the disease, showed artistic skills which they had never expressed in previous life. The artistic creations of savants observed the savant’s criteria i.e. recommended replicas without semantic symbolism. The episodic memory (sum of past real life experiences) was maintained in contrast to the semantic (general and abstract knowledge). Selective neurodegeneration in the left anterior temporal cortex and anterior cingulate aside the suspension of optical systems associated with sensory perception, giving birth to their artistic abilities. This was also the starting point for the definition of "paradoxical functional facilitation" (improving specific skills of the person after brain injury).2
The fact that some autistics have expressed seizures, arose the question whether the savant syndrome is associated with epilepsy. In worldwide bibliography only one case of an epileptic is referred, who after the onset of the crisis showed the skills of savants.10 However, the prevalence of stimulant (glutaminergic) neurons, as we will explain below, can lead to disruption of electrical activity in the brain and release seizures, in toxicity and destruction of inhibitory Purkinje cells, inflammation and cytokine production. Such situations lead to a complete disruption of the functioning of the hemispheres of the brain.14
Reportedly, the paradoxical abilities of the syndrome have been observed after meningitis, schizophrenia, brain injuries, severe visual impairment, stroke, syndrome of Gilles de la Tourette, cerebral palsy (Little’s disease).9
Is there a gene for the syndrome?
So far we have reported acquired pathological conditions that lead to the emergence of the syndrome. Continued involvement with the pathology of the syndrome led researchers to study families who had capacities of savants. It has been discovered a correlation with the position of chromosome 15q11-q13. It seems that the genes encoded, lead in alternative activation paths that predispose to mental disorders and show talent in individual sectors. It is interestingly the fact that the Prader-Willi syndrome is caused by a deletion in the same chromosomal position. This might explain common features observed between autism and Down syndrome and in Prader-Willi (delayed development of speech and motor skills, learning difficulties). Some children with this syndrome show early puzzle solving skills for their early age despite the low intellectual level. Could anyone claim that these are savant skills? The future will hopefully reveal us a lot.2
Why syndrome "prefers" men
According to the model of Geschwind and Galaburda (1987), there is a preponderate functioning template in the two different hemispheres. The dominant hemisphere (mainly left for 75% of people) is responsible for speech output capacity, predominant use of one hand, and understanding of written and spoken language. The residual hemisphere has different functions from the dominant, such as geometric design, sense of perspective and the recognition of music. The development of various neural networks and the general plasticity of the brain are achieved by the interaction of growth factors. During embryonic development the dominant-left hemisphere lags behind the right to develop, making it vulnerable to various endometrial or not factors. Testosterone is known to affect the development of many brain areas. Both the male and the female fetuses are exposed during intrauterine life in testosterone; in males at much higher levels. So testosterone affects the development of the left hemisphere and thus affects its faculties. The remaining functions are no longer the sum of disturbances encountered in autism and the syndrome savant. Parts of the right hemisphere are compensatory overdeveloped and overactive. This theory is supported by the fact that the predominant use of his left hand is more common in men as in many savants.11
The theory that the root of the syndrome is a lesion of the left hemisphere and the prevalence of right is verified by fMRI findings. It has been discovered that activation of primary and secondary auditory cortex followed an unexpected pathway conduction stimulus localized in right, instead of the usual position in the left hemisphere. In addition, the central area of the right Broca center was greater. But striking is the fact that the pathways associated rather with the composition of the information skeleton or the pathways with the codification of information details, were localized to homologous regions of opposite hemispheres than to the ipsilateral one.14
Neurobiology of the syndrome
In light of the above, there is a hemispheric localization of the lesion that leads to the occurrence of unusual skills of savants and also various intrauterine hormonal (testosterone) and neurotrophin factors affecting the development of different brain regions. We mentioned several acquired pathologies apparently based on the left hemisphere (especially in the frontal lobe), causing degeneration and allowing the right hemisphere to get priority. But what exactly happens at molecular level?
The brain is an organ with limitless capabilities just because of the neuronal and synaptic plasticity. During embryogenesis neurons, synapses, neural networks are formed. Various exogenous factors can influence the developmental stages (proliferation, migration, aggregation, differentiation, myelinogenesis) and consequently the architecture of the brain and the appearance of mental disorder. Noteworthy, also is the fact that shortly before birth and when neural networks have been completely formed, apoptosis takes place of the networks at nearly 50%. Perhaps this is the beginning of an underactive left hemisphere? The whole mechanism may be involved in another programmed cell death that occurs after puberty. The aim at this age stage is to reduce the synapse mainly in the frontal lobe to develop abstract thinking. However, the maturation of motor and cognitive functions and those of the emotion associated with completing the development of synapses during puberty. Therefore, the period of puberty is a critical period of the human life.12
Neurochemical studies revealed low serotonin synthesis in autism right hemisphere.2 Serotonin plays an important role in neurogenesis, differentiation and migration of neurons, possibly in axon myelination, as well as in synaptogenesis. The absence of serotonin in experiments in mice leads to permanent degeneration of neurons in the hippocampus and the cerebral cortex from early fetal period. Also, serotonin contributes to the development and maturation of dendrites. Studies in adult mice lack serotonin, observed reduction of dendrites that may be reversed by administration of the agonist 5-IT1A receptor. Lacks of serotonin in young mice reduced synapses, but are offset by the start of adulthood. And while one would expect with advancing age the reduction of the synapses, rather they are increased, particularly in the dentate gyrus. Several factors during development may affect serotonin levels e.g. viral infections, malnutrition, hypoxia, stress, alcohol, nicotine. An important finding in autism is the serotonin serum levels in childhood (autism yperserotonemia) that lead to stock depletion in the brain. It has been hypothesized that during embryonic development before the formation of the blood-brain barrier, serotonin enters at moreover levels in the brain by diverting the normal development and causing loss of serotonin receptors. In doing that, probably malfunction starts of the serotonergic system. PET studies show reduced serotonin synthesis in the cortex and the thalamus and reduced dendrite network in areas CA1 and CA4 of the hippocampus.13
How is the information transferred?
The information conveyed in the form of the action potential, are determined not by its form, but from the pathway through which the signal passes. The brain analyzes and interprets patterns of incoming electrical signals and generates in this way the everyday sensation. According to the latest theories, each complex-signal received by the brain as an image is transferred for treatment to form smaller sub-sections in the same way a computer works. Unlikely, the savants do not degrade the original signal but transfer it unchanged. Thus, a limited number of neurons is used for the transfer of excitation. In normal people, since they split the signal, mediate many neurons, where each one represents a part of the signal. Losing even a few neurons in the message transfer reduces the accurate decoding of the information. Let's take an example with two trees which are definitely not the same, even if they are of the same species. Any normal person can recognize and categorize them as 'trees' isolating the small portion of the neural signal that is common to all trees. While the savants, should recognize trees with a more difficult process, because they use whole signs. So, they cannot identify the similarities and recognize the object as a ‘tree’.
Normally, to compress the message and remove the detail responsible are applying different processes inhibitors (GABA-receptor genes, abnormalities of GABA-receptor, estrogen, autoantibodies, IGF-1).17 Therefore in the syndrome, where every detail is recorded and assigned by the person, there is a disturbance in the inhibitory system of neurons. This is evidenced by histopathological findings in autistic brains. (loss of Purkinje cells, more numerous, smaller and less compact columns of the cells of layer III. The cells of layer III as well as all the layers in the normal brain are separated by columns with white substance which consists of axons). However during the transfer of the message various stimulating agents may play a great role, such as beta-2 adrenergic receptor, inflammation cytokines, growth fibroblast factor etc. In conclusion, the whole elaborating process of each image, thought, smell stimulus, audio or any other signal is essentially the game between the inhibitory and excitatory system of the brain.
In the case of savants, let’s consider how they depict a picture in their mind, considering what we have mentioned before. The image within fractions of a second, trips through the retina, optic nerve, the lateral geniculate body (LGN) leads to the primary visual cortex (V1, located in and around the calcarine fissure in the occipital lobe), passes through V2, goes in V4 and ends in the lower temporal lobe and the prefrontal associative area in the frontal lobe. The frontal and temporal lobe feedback is inhibitory upon the V1 and V2 areas, thus in case of fail of this process, information returns in the associative cortex and becomes detailed and precise. We conclude that the brain isolates a small piece of information to primary sensory cortices and then allows making various inhibitory and excitatory connections with other systems related to information.14
The EEG activity recorded in autism is characterized by low coherence between neurons, which is justified by the reduced presence of GABA-A neurons. A second important finding is the record of high c-wave, representing the connection of different populations of neurons in a single network to carry a motion or thought. In savants, the preservation of detail is mediated by neurons different from GABA-A, making minor repairs to approach perfection of detail. Imprint of action of these neurons is elevated c waves.14
Do we all hide within us the abilities of savants?
Modern research has now turned over to the neurobiological study in a trial of exploration and development of these skills in each of us. After all, no one can deny the innate tendency of mankind to cognitive development. According to Snyder and Mitchell (1999) these abilities are possible for any human brain, but in the normal population are simply jostled of higher cognitive functions. After a temporary disruption of function in some cortical areas of the left hemisphere, it is possible to emerge the capabilities which characterize the savant syndrome, Based on these results, Young and his colleagues, used repetitive transcranial magnetic stimulation (rTMS) and discontinued the function of frontotemporal cortex area which were involved in the development of skills. In some people, the 'narcosis' of frontotemporal cortex, as evidenced by deficits in memory tests, showed an improvement in the performance of various skills of the syndrome. Certainly, it was not comparable to the capacities of prodigious savants, but it was not the same as before the stimulation. However, it should be remembered that the stimulation lasted for a few minutes and that the capacity in as many individuals occurred, had to spend enough time period, even years. Here arises the question, whether the continued practice of the brain during this time accelerates the process of expressing savant abilities. Apart from this, there is special concern about the outcome of the frontotemporal cortex stimulation and the execution of a predetermined process from the person simultaneously. All these and as many others have already been initiated in research by Young and hopefully soon have answers.15
Neuronal plasticity and neurotrophic factors: the key to the case
We know that nerve cells cannot regenerate during various biological processes from intrauterine life to old age and that over the years the brain degenerates. But neural networks are constantly alert to the recording and analysis of information provided, the mnemonic fixation and recall, thereby triggering the filaments of higher mental functions, memory, crisis, thinking, learning, intelligence and thus, defining the functionality of the individual. Have savants discovered a way to access to these networks promoting the special abilities? The secret lies in the neurotrophic factors. Neurotrophic factors, (the most important representative is the Brain-derived neurotrophic factor-BDNF) belong to the family of growth factors. They are involved in development, differentiation and viability of neurons, in the transfer of information across synapses, in neuronal adaptation to new operating conditions, the recovery following exogenous damage. They inhibit apoptosis of neurons in maintaining a state of continuous proteinosynthesis through their retrograde trafficking, accelerate neuronal death if survival is impossible, contribute to synaptic communication with the ability of axons to project recurrent axial wires and extrapolated to create new synapses, participate in lengthy post-synaptic strengthening information. Note that in damage nerve cells, axons that normally result in them are being diverted and develop synaptic relationships with other neural cells. From this process can stem the excellent skills of savants could be generated. 16
Looking at the whole affair from a different side, savants are able to cover some of the capabilities of the brain, following different paths of thinking than everyone. By filtering the millions of exogenous performances receives daily every man, focus on essential and continuous engagement with them, evolved specific cognitive functions. Under the constant flow of information and continuous exercising of the brain, whichincrease the operational requirements of neurons, an increasing number of neurotrophic factors are released and numerous synapses are created. This is a kind of thinking that differs from the standard, rigorous thinking of the modern human whose every spontaneity is suppressed. Under this perspective, one would dare argue that savants are not mentally handicapped people, but have found different ways to communicate non-understandable by us. The perceived 'low intelligence' may be the primitive childish behavior to everyone silenced in adulthood and integration into society, as wreaked from the requisite standards of society.
Window to the brain
According to Treffert, savant syndrome, gives us a window into the brain and perhaps a window of understanding of our role as humanity. From a medical point of view, the possibility of understanding the workings of this complex circuit of neurons is a challenge for the same medicine as a science but also on a personal level for each 'thirsty' neuroscientist. By studying the syndrome in anatomical, molecular, chemical level, is expected to draw conclusions about the neuronal plasticity, neuronal communication and integration in processing systems, as well as in neurodegeneration. Hopefully as reflected by all above results, we will have treatment options or the possibility to prevent chronic neurodegenerative syndromes, such as epilepsy, vascular stroke, and psychiatric disorders. Through this mysterious syndrome would someone dare to make the speculation that expanded our ideas about who we are and what we are capable of. We have an opportunity to rethink our roles as humanity; focus on the real reason for our existence. The so called modern man is being judged to prove that he is worthy of the triumphal designation these centuries was following him, "being reasonable".