Humans typically have five fingers on each hand, but there are cases when individuals have extra digits or polydactyly. Many find these extra digits to be fascinating while some consider them as a deformity.
Extra digits have been studied by scientists for a long time, and their neuropsychology is an interesting field of study.
What is Polydactyly?
Polydextry is a congenital condition that results in an individual having one or more extra fingers or toes. This condition may be unilateral (on one side) or bilateral (on both sides) and runs in families.
Extrapolating based on research, approximately one in 700-1000 babies worldwide are born with this condition. It may appear on any hand of the body as additional full fingers, partially formed extra fingers or additional digits fused with existing fingers.
In addition, it occurs commonly in various animal populations and allows them access to specialized adaptations that are beneficial to survival.
The Science behind Polydactyly
Extra fingers or toes appear due to a mitotic error that occurs during embryonic development. Polydactyly can involve many types of genetic mutations, including the SHH (sonic hedgehog) gene in more than half of the polydactyly cases.
An intricate developmental cascade of genes during embryogenesis dictates digit formation. The genes control the organization, elongation, and differentiation of the limb buds, culminating in the formation of bone, muscle, tendon, and skin. In polydactyly, alterations during differentiation result in the formation of extra digits.
Also, environmental factors such as drugs, radiation, and alcoholism may contribute to polydactyly.
Psychological Impacts of Polydactyly
Extra digits have been associated with stigmatization, and cultural perceptions often impact such individuals.
Historically, people view polydactyly either as a curse or a blessing, mainly depending on the traditions and beliefs of the particular culture in question. These individuals may experience harassment and bullying, especially during childhood. Social stigma is also related to concealment to avoid discrimination or suffering from anxiety and a lack of self-confidence.
Fortunately, most social stigmatization can be countered by a combination of education and exposure through mass media, leading to social acceptance eventually. However, psychotherapy can be helpful for overcoming more severe social anxiety driven by excessively negative self-perceptions associated with differences in normative anatomy.
Neurological Impacts of Polydactyly
For some individuals, having extra fingers or toes offers an opportunity to augment their ability to perform certain tasks, including music.
For instance, some renowned pianists and guitar players have extra digits that allow them to navigate instruments with more facility than those without them. This is because the brain has a flexible capacity that allows it to adapt quickly to the available resources. This adjustment mechanism becomes significant when a person has some form of polydactyly.
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Polydactyly and the Brain
Scientists have found that the brains of people with extra digits adapt in a way that synaptically maps to the extra digit.
Moreover, it possesses more considerable brain matter devoted to finger representation, as well as improved sensory and motor functions in the extra polydactylous digits. The improved digital representation is due to the brain’s re-division of the cortex, essentially making more room for each digit in the representation area within the brain.
Polydactyl Brains
The discovery of polydactyl brains has intrigued neuroscientists for decades. Scientists are yet to understand the larger effects and optimal use of the polydactyl brain.
However, such research has significant implications for medical practice, ranging from the advancement of prosthetics to treating individuals who lose a digit to an injury.
Applications of Polydactyly
Polydactyly’s study has led to an improved understanding of limb development, enabling scientists to decode the genetic pathways that regulate these processes.
Recently, basic research on the space-time control drivers and genes involved in polydactyly has led to the development of genetically modified mice. The mice have several extra toes with distinct morphological features, enabling scientists to understand the developmental pathways in detail.
Ideally, as scientists continue to decode the mechanisms behind congenital abnormalities, they can develop treatments that could help repair lost limbs. The results of polydactyl research are invaluable, significantly contributing to industry advancements in hand prosthetics and treating congenital anomalies.
Polydactyly and the Evolutionary Niche
In evolutionary terms, extra digits have proven to be advantageous, especially in animal populations. For instance, bats have a double-thumbed wing that allows them to form robust grips while hanging from vertical surfaces.
Some amphibian species, such as the African clawed frog, have an extra digit that they use as a spade to dig burrows. Wild cats use an extra toe to grasp their foraging targets and, for skiing, as an anchor. In humans, the historical use of extra fingers for musical instruments demonstrates such adaptability.
Conclusion
The study of extra digits from a neuropsychological perspective helps us understand the adaptability of the nervous system. Polydactyly has a neurological basis that stimulates the brain to adapt and benefit from the extra digits.
Additionally, animal populations display evolutionary advantages and use extra digits as adaptive mechanisms to survive. Studies focused on polydactyly has resulted in a better understanding of limb development and the genetic pathways that regulate them.
Continuing with such research could prove beneficial to the future of limb replacements and the advancements in prosthetics technologies for individuals with limb deficiencies and amputations.
