LINK BETWEEN DYSLEXIA AND THALAMUS

Source: Hopkinsmedicine

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Context

Researchers based in Dresden, Germany say that dyslexia is linked to changes in the function and structure of a specific part of the human brain called the visual thalamus.

About Dyslexia

• Dyslexia is a learning disability that makes reading and language-related tasks harder.
• It happens because of disruptions in how your brain processes writing so you can understand it.
• Dyslexia falls under the umbrella of “specific learning disorder.” That disorder has three main subtypes:
• Reading (dyslexia).
• Writing (dysgraphia).
• Math (dyscalculia).
• Dyslexia occurs in about 5%-10% of people worldwide, making it the most common learning disorder.
• The symptoms can present as early as in infancy.
• Boys are affected two to three times more often than girls.
• Famous dyslexics include Albert Einstein, Ludwig van Beethoven, Charles Darwin, Ernest Hemingway, Agatha Christie and Whoopi Goldberg.

What causes dyslexia?

• The exact cause of dyslexia isn’t clear.
• Genetics: Dyslexia is highly genetic and runs in families. A child with one parent with dyslexia has a 30% to 50% chance of inheriting it.
• Research shows people with dyslexia have differences in brain structure, function and chemistry.
• Infections, toxic exposures and other events can disrupt fetal development and increase the odds of later development of dyslexia.

The research

• The visual thalamus is a key brain region that connects the eyes with the cerebral cortex, which is important to our ability for reasoning, emotion, thought, memory, language and consciousness.
• Visual information from the eyes is processed in two separate parts with different tasks:
• One part is larger than the other and primarily processes colors.
• The other, smaller part recognizes movements and rapidly changing images.
• The researchers found that people with dyslexia show changes in the function and structure of the movement-sensitive part of the visual thalamus.

Brain Anatomy

• The brain is a complex organ responsible for controlling thought, memory, emotion, touch, motor skills, vision, breathing, temperature regulation, hunger, and all bodily processes.
• It, along with the spinal cord, forms the central nervous system (CNS).

 Composition of the Brain

• Average weight: About 1.3-1.4 kgs in adults.
• Composition: Approximately 60% fat, with the remaining 40% comprising water, protein, carbohydrates, and salts.
• Structure: Contains blood vessels, nerves, neurons, and glial cells.
• Gray Matter:
  • • Location: Outer portion of the brain; inner portion of the spinal cord.
    • Composition: Neuron cell bodies (somas).
    • Function: Processing and interpreting information.
• White Matter:
  • • Location: Inner portion of the brain; outer portion of the spinal cord.
    • Composition: Axons wrapped in myelin.
    • Function: Transmitting information between brain regions.

Brain Function

• The brain sends and receives chemical and electrical signals.
• Signals control various processes and are interpreted by the brain.
• Some messages remain within the brain; others travel through the spinal cord and nerves.

Main Parts of the Brain

Cerebrum

• Location: Front part of the brain.
• Components: Gray matter (cerebral cortex) and white matter.
• Functions: Initiates and coordinates movement, regulates temperature, enables speech, judgment, problem-solving, emotions, learning, vision, hearing, and other senses.

Cerebral Cortex

• Structure:
  • • Outer gray matter with folds (gyri) and grooves (sulci).
    • Divided into two hemispheres connected by the corpus callosum.
• Function: Covers large surface area; involved in various higher brain functions.

Brainstem

• Components:
  • • Midbrain: Involved in hearing, movement, response calculations, and contains substantia nigra.
    • Pons: Connects midbrain to medulla; involved in functions like tear production, chewing, and facial expressions.
    • Medulla: Regulates heart rhythm, breathing, blood flow, and reflexive activities (sneezing, vomiting).

Cerebellum

• Location: Back of the head, below the cerebrum and above the brainstem.
• Functions: Coordinates voluntary muscle movements, maintains posture, balance, and equilibrium. Recent studies suggest roles in thought, emotions, and social behavior.

Meninges

• Dura Mater:
  • • Outermost layer; thick and tough.
    • Includes periosteal and meningeal layers.
• Arachnoid Mater:
  • • Thin, web-like layer.
    • Contains cerebrospinal fluid (CSF) that cushions and circulates around the CNS.
• Pia Mater:
  • • Thin membrane that closely follows brain contours.
    • Rich in blood vessels.

Lobes of the Brain

• Frontal Lobe:
  • • Location: Front of the head.
    • Functions: Personality, decision-making, movement, speech, smell recognition.
• Parietal Lobe:
  • • Location: Middle part of the brain.
    • Functions: Object identification, spatial relationships, pain and touch interpretation, language understanding.
• Occipital Lobe:
  • • Location: Back part of the brain.
    • Function: Vision.
• Temporal Lobe:
  • • Location: Sides of the brain.
    • Functions: Short-term memory, speech, musical rhythm, smell recognition.

Other Structures Within the Brain

• Pituitary Gland: Regulates other glands and hormones.
• Hypothalamus: Regulates body temperature, sleep patterns, hunger, thirst, and some aspects of memory and emotion.
• Amygdala: Regulates emotion, memory, stress, and the "fight or flight" response.
• Hippocampus: Supports memory, learning, navigation, and spatial perception.
• Pineal Gland: Secretes melatonin, regulates circadian rhythms and sleep-wake cycle.
• Ventricles and Cerebrospinal Fluid (CSF): Four open areas in the brain that manufacture CSF. CSF cushions the brain and spinal cord, removes waste, and delivers nutrients.
• Vertebral Arteries: Supply blood to the rear brain; join to form the basilar artery.
• Carotid Arteries: Extend up the neck; internal branches supply the front of the brain.
• Circle of Willis: Connects major arteries and facilitates communication between arterial systems.
• Cranial Nerves: 12 nerves originating from the brain perform various functions.

Sources:

IndianExpress

PRACTICE QUESTION  Q:Consider the following statements about the human brain: 1.The medulla oblongata controls heart rate and breathing. 2.The pineal gland is involved in the regulation of circadian rhythms and the sleep-wake cycle. Which of the above statements is/are incorrect? a) 1 only b) 2 only c) Both 1 and 2 d) Neither 1 nor 2 Answer: d Explanation: Both the statements are correct:  The medulla oblongata, located in the brainstem, is responsible for regulating vital autonomic functions such as heart rate, breathing, blood pressure, and reflexes like coughing and swallowing. The pineal gland secretes melatonin, which helps regulate circadian rhythms and sleep-wake cycles.