Understanding the Brain: Structure and Functions

Introduction

  • Do Now: Identify at least oe thing the brain helps you to accomplish.

  • Learning Intention (L.I): To explore the functions and structures of the brain.

The Cerebrum

  • Cerebrum: The largest division of the brain, divided into two hemispheres by the longitudinal fissure.

  • Corpus Callosum: A deep structure within the cerebrum that facilitates communication between the two hemispheres of the brain.

General Cerebral Functions

  • General Cerebral Functions:

    • Basal Nuclei: Responsible for cognitive processing including thinking and planning actions/movements.

    • Basal Forebrain: Key player in learning and memory.

    • Limbic Cortex: A component of the larger limbic system involved in emotion, memory, and behavior.

The Cerebral Cortex

  • Cerebral Cortex: The gray matter forming the outermost surface of the cerebrum.

    • Gyrus/Gyri: Elevated ridges that wind around the brain.

    • Sulcus/Sulci: Small grooves that divide gyri.

    • Lateral Sulcus: Separates the temporal lobe from the parietal and frontal lobes.

    • Central Sulcus: Separates the parietal and frontal lobes.

    • Parieto-Occipital Sulcus: A small medial landmark that segregates the parietal and occipital lobes.

The Four Lobes of the Cerebral Cortex

  • Each hemisphere of the cerebral cortex is divided into four lobes:

    • Frontal Lobe

    • Parietal Lobe

    • Temporal Lobe

    • Occipital Lobe

The Frontal Lobe

  • Frontal Lobe (Motor Functions):

    • Primary Motor Cortex (Precentral Gyrus): Responsible for sending out instructions to move skeletal muscles.

    • Representation as a Homunculus: A visual guide demonstrating how different parts of the motor cortex correlate with specific body parts.

    • Premotor Area: Engaged in the thought process of movement planning.

    • Frontal Eye Fields: Essential for moving the eyes and attending to visual stimuli.

    • Broca’s Area: Critical for producing coherent speech, typically located on the left side of the brain (associated with Left and Language).

    • Prefrontal Cortex (Prefrontal Lobe): Governs personality, short-term memory, and consciousness.

Broca's Aphasia

  • Broca's Aphasia: A condition resulting from damage to Broca's area, leading to a diminished ability to speak fluently.

Prefrontal Lobotomy

  • Prefrontal Lobotomy: An outdated surgical procedure for treating personality disorders (psychiatric conditions), known for having profound effects on patient personalities.

The Parietal Lobe

  • Parietal Lobe (Sensory Functions):

    • Primary Somatosensory Cortex (Postcentral Gyrus): Processes tactile sensations like pressure, pain, vibrations, itching, and tickling.

    • Proprioception: The body's ability to sense the position of its parts without visual input.

    • Kinesthesia: The ability to perceive bodily movements.

    • Somatosensory Association Cortex: Integrates touch sensations with previous experiences for efficient processing.

    • Primary Gustatory Cortex: Processes the sense of taste.

The Temporal Lobe

  • Temporal Lobe:

    • Primary Auditory Cortex: Processes auditory information (hearing).

    • Part of the Limbic System: Involved in the processing of emotions memory and behavior.

    • Long-Term Memory Formation: Works alongside other brain structures, especially sensory areas.

    • Wernicke’s Area: Critical for language comprehension, typically localized to the left side of the brain.

Wernicke’s Aphasia

  • Wernicke's Aphasia: A condition characterized by decreased language comprehension; individuals may struggle with understanding language, resulting in nonsensical sentences despite fluent speech.

The Occipital Lobe

  • Occipital Lobe:

    • Vision: Responsible for visual processing.

    • Primary Visual Cortex: Receives and processes visual information directly from the eyes; assembles fundamental visual components such as size, color, light, motion, and dimensions.

    • Visual Association Area: Interprets information received from the primary visual cortex, aiding in recognition of faces and familiar objects.

Visual Processing Pathways

  • Visual Fields:

    • Right visual field and left visual field are processed separately before combining in the occipital lobe.

  • Important Structures in Visual Processing:

    • Nasal & Temporal Retina: Each eye's retina processes different visual fields.

    • Lateral Geniculate Nucleus: Part of the thalamus, relays visual information to the primary visual cortex.

    • Superior Colliculus: Involved in visual attention and eye movements.

    • Optic Chiasm: The crossing of optic nerves, allowing visual input from both eyes to integrate into a singular perception.

Severed Corpus Callosum

  • Impact of a severed corpus callosum: May lead to challenges in the coordination and sharing of information between the two brain hemispheres, affecting cognitive and perceptual functions (noted in the context of neuroscience studies).

  • Implications for Vision and Cognition: Understanding how visual and cognitive processes differ between two hemispheres when the connection is severed provides insight into brain function diversity.