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