Cortical Organization and Functions Module 2

Module 2: Cortical Organization and Functions

• This module covers the anatomy and functions of sensory systems, particularly the neocortex's role in higher cognitive functions, hemispheric specialization, and individual differences in cerebral asymmetry.

• Sensory systems include vision, audition, somatosensation, body senses (somatosensory, vestibular, proprioception), and chemical senses (taste and smell).

• Sensations are physical changes in sensory systems stimulated by external factors, while perception is our brain's interpretation of those sensations.

• The neocortex is a six-layered structure crucial for higher-order functions.

• Neural mechanisms underpin perception and attention.

• Hemispheric specialization and lateralization refer to the different functions performed by each brain hemisphere.

• The left hemisphere is pivotal in language processing.

• Individual differences in cerebral asymmetry are influenced by factors like handedness, sex, and genetics.

• Clinical implications and disorders linked to atypical cerebral asymmetry are discussed.

• Visual perception involves the brain converting sensory signals into meaningful experiences

• Visual illusions demonstrate the brain's role in creating perception.

• The different sensory areas are represented topographically in the brain.

• The organization and processes of mammalian sensory systems (squirrel, cat, owl monkey, and rhesus monkey) are diagrammed.

• Visual systems comprise photoreceptors like cones and rods.

• Cones are responsible for color vision in higher light levels (photopic vision).

• Rods facilitate scotopic vision (low light levels).

• The fovea, a central part of the retina, has a high cone density for sharp vision.

• The optic nerve transmits visual information to the brain.

• The optic chiasm is where optic nerves from each eye cross.

• Visual information processing involves two main pathways (geniculostriate and tectopulvinar) reaching the visual cortex.

• The geniculostriate pathway is responsible for pattern, color, and motion recognition, including conscious visual functions.

• The tectopulvinar pathway facilitates detecting spatial locations and movements of visual stimuli.

• The auditory system converts pressure waves into perceptions of sound.

• Sound is defined by its frequency (pitch), amplitude (loudness), and complexity (timbre).

• The ear's anatomy consists of the outer ear (pinna, ear canal), middle ear (eardrum, ossicles), and inner ear (cochlea).

• The middle ear amplifies sound waves to enable the inner ear to detect them.

• The cochlea has specialized sensory hair cells to transduce mechanical signals into electrical signals.

• The place representation in auditory cortex reflects sound frequency.

• Cochlear implants directly stimulate the basilar membrane regions, thus facilitating sound perception.

• Auditory pathways include nuclei in the hindbrain and midbrain, with the brain hemispheres receiving information from each ear.

• The superior and inferior colliculi are parts of the midbrain significantly involved in integrating auditory and visual information concerning the location of sound.

• Multiple nuclei relay sensory information to the auditory cortex across different brain regions.

• The somatosensory system detects body touch, pain, temperature, proprioception (body position), and movement.

• Nociceptors detect pain, temperature, and itch.

• Tactile receptors (hapsis) enable fine touch.

• Proprioceptors sense body position and movement.

• Somatosensory pathways (anterior and posterior spinothalamic tracts) carry information from sensory neurons to the brain.

• The brain regions responsive to the various parts of the body form a somatosensory homunculus.

• The vestibular system is responsible for detecting body movement and balance.

• Taste buds are the receptors for taste sensation.

• Taste and smell heavily depend on chemical factors in saliva and food.

• Taste and smell receptors are found in various areas of the body

• The olfactory system detects odours.

• Olfactory receptors are located in the nasal cavity.

• They project to the olfactory bulbs, and further to the olfactory cortex, hypothalamus, and amygdala, amongst other brain areas.

• Odors require passing through mucus to reach receptors.

• Olfactory epithelia vary across species.

• Pheromones are biochemicals released by an animal that affect another animal's behaviour or physiology.

• The brain uses sensory information in conjunction with other factors, such as memories, emotions, and experiences, to form perceptions, which are different from sensations.

• Sensory mixing (synesthesia) is the perceptual mixing of sensations from different sensory modalities.

• The cortex has a hierarchical organization of function, with specific areas responsible for various functions.

• The cortex has different levels of function, with lower ones supporting, basic behaviours, and higher ones supporting more advanced behaviors.

• Animals that lack higher brain regions, but not their midbrain, exhibit automatic motor skills, like grooming, chewing, and lapping water.

• The diencephalon, containing the thalamus and hypothalamus, regulates motivation and emotional responses.

• The basal ganglia are involved in the initiation and execution of specific motor actions.

• The neocortex is organized into distinct structural layers.

• The prefrontal cortex is an essential part of the neocortex involved in many higher functions.

• Attention networks like the ventral and dorsal networks have unique roles in different aspects of attending in individuals.

Cortical Organization

• Cortical organization involves specific regions for processing sensory information, formulating motor intentions, and generating skilled movements.
• Felleman's model illustrates a dynamic interaction within and between regions of the cortex.

Cerebral Asymmetries

• Research highlights functions lateralized to each hemisphere.
• The brain is not just composed of symmetrical structures but functions in an asymmetrical manner.
• Specific anatomical differences are evident between hemispheres (e.g., size of the planum temporale).
• Several factors contribute to individual brain asymmetries in lateralization, such as sex and handedness.

Disorders

• Disorders linked to cortical asymmetries (e.g., autism, major depressive disorder, Obsessive-Compulsive Disorder and ADHD) involve different aspects of the brain.
• These disorders may be characterized by varied brain asymmetries in terms of the organization and connection of different brain regions affecting function.