Q 1.15. Higher Cortical Functions. Gnosis and Agnosia. Praxis and Apraxia.

Q 1.15. Higher Cortical Functions. Gnosis and Agnosia. Praxis and Apraxia.

Cerebral Cortex: Structure and Functions

The cerebral cortex is the outer layer of grey matter that covers the surface of both cerebral hemispheres. It’s approximately 2 to 4 mm thick and contains an aggregation of nerve cell bodies. This layer is intricately folded, forming elevations called gyri and grooves known as sulci. The cerebral cortex plays a crucial role in various functions:

  1. Perception and Awareness: It processes sensory information, allowing us to perceive and be aware of our surroundings.
  2. Motor Activity: The cortex is involved in planning and initiating purposeful movements.
  3. Higher Cognitive Functions: These include decision-making, motivation, attention, learning, memory, problem-solving, and conceptual thinking.

The cortex is organized into distinct functional areas, including sensory, motor, and association areas. It’s the substrate for comprehension, cognition, communication, reasoning, and more.


Gnosis and Agnosia


    • Gnosis refers to knowledge or understanding.
    • In the context of the cerebral cortex, it represents our ability to recognize and understand objects, people, and sounds.
    • When gnosis is intact, we can process sensory information effectively.



    • Agnosia (from the Greek word “gnosis,” meaning “not knowing”) is a neurological condition.
    • It occurs when a person is unable to recognize and identify objects, persons, or sounds despite normally functioning senses.
    • Types of agnosia include visual agnosia (difficulty recognizing familiar faces and objects), auditory agnosia (inability to recognize sounds), and tactile agnosia (difficulty recognizing objects by touch without using sight).



Praxis and Apraxia

  • Praxis refers to the ability to formulate skilled movements based on stored complex representations and previously learned movements.
  • Apraxia is the inability to carry out a learned motor act despite having normal motor, sensory, or coordination functions.
  • There are two main types of apraxia:
    1. Ideational Apraxia: Patients struggle to perform purposeful motor acts because they no longer understand the overall concept of the task or cannot retain the idea. They may perform isolated components of a task but cannot combine them into a complete act.
    2. Limb-Kinetic Apraxia: Difficulty with precise movements of individual limbs, such as buttoning a shirt or tying shoelaces.




















Verified by Dr. Petya Stefanova