Lecture2_CogNeuro_SP25 - Tagged

The Neural Basis for Cognition

Lecture Overview

  • Focuses on understanding cognitive processes through the lens of neural structures and functions.

Capgras Syndrome: An Initial Example

Definition

  • A psychiatric condition where individuals recognize loved ones but believe they are impostors.

  • Can include delusions of having been kidnapped.

Cognitive and Emotional Processing

  • Normal facial recognition integrates:

    • Cognitive appraisal: Understanding and evaluating stimuli.

    • Emotional appraisal: Emotional response to stimuli.

  • In Capgras syndrome, emotional processing is disrupted, leading to a disconnection between recognition and emotional response.

Neural Basis for Capgras Syndrome

Neuroimaging Findings

  • Amygdalar Damage: Affects emotional response.

  • Prefrontal Cortex (PFC) Damage:

    • Impairs reasoning and analytical thinking, leading to illogical beliefs such as recognizing a loved one but doubting their identity.

    • Patients may struggle to discern reality due to impaired tracking of truths, resulting in unchecked strange beliefs.

Principal Structures of the Brain

Main Divisions

  • Brain consists of three main parts:

    1. Hindbrain - Basic life functions and rhythms.

    2. Midbrain - Movement coordination, especially eye movements.

    3. Forebrain - Includes cortex and subcortical structures, crucial for complex functions.

Hindbrain

  • Located atop the spinal cord.

  • Regulates vital life functions and alertness.

  • Cerebellum: Largest part of hindbrain; involved in movement, balance, and cognitive functions.

Midbrain

  • Sits above the hindbrain.

  • Coordinates movements and processes auditory information.

  • Plays a role in pain regulation.

Forebrain

  • Encompasses the cortex and subcortical structures.

  • Cortex: Comprises about 80% of the brain, involved in higher functions, consists of two hemispheres separated by the longitudinal fissure.

Directions and Terminology in Neuroscience

  • Dorsal/Ventral:

    • Dorsal: back/top

    • Ventral: below/down

  • Anterior/Posterior:

    • Anterior: front

    • Posterior: back

  • Medial/Lateral:

    • Medial: middle

    • Lateral: outside

White Matter

  • Responsible for connectivity between brain areas via tracts, facilitating communication.

Subcortical Structures of the Brain

Key Components

  • Thalamus: Relay station for sensory information.

  • Hypothalamus: Regulates bodily functions (temperature, hunger).

  • Limbic System: Emotion and memory processing

    • Amygdala: Emotion and fear responses.

    • Hippocampus: Memory formation.

Lateralization of Brain Functions

Hemispheric Specialization

  • The brain has two hemispheres linked by commissures like the corpus callosum, facilitating interhemispheric communication.

  • Each hemisphere specializes in different functions:

    • Left Hemisphere: Language and analytical tasks.

    • Right Hemisphere: Spatial awareness and context.

Split-Brain Patients

  • Patients with a severed corpus callosum due to severe epilepsy.

  • Highlight hemispheric specialization; left regulates language while the right can only point to choices without verbalizing.

The Cerebral Cortex

Structure

  • The largest brain portion, covering the cerebrum.

  • Contains:

    • Motor Areas: Control voluntary movements.

    • Sensory Areas: Process sensory input.

    • Association Areas: Integrate and interpret information.

Specific Regions of the Cortex

Association Areas

  • Comprise approximately 75% of the cortex; critical for linking ideas and sensory input.

  • Damage leads to functional impairments:

    • Apraxia: Movement errors.

    • Agnosia: Inability to recognize objects.

    • Aphasia: Language issues.

    • Unilateral Neglect: Ignoring one side of visual space.

    • Prefrontal Damage: Impaired planning and decision-making.

Brain Cells

Basic Neuron Structure

  • Dendrites: Receive signals from other neurons.

  • Cell Body: Contains nucleus; integrates signals.

  • Axon: Transmits signals to other neurons.

Glial Cells

  • Assist in nervous system development and repair.

  • Manage nutrient flow and insulate neurons.

The Synapse

Structure and Function

  • Neurotransmitters released to change the postsynaptic membrane.

  • Action potential initiated if the threshold is met, following the all-or-none principle.

  • Over 100 neurotransmitters identified, critical for neuron communication.

Synaptic Transmission

  • Integrates information from multiple neurons, adjusts responses based on incoming signals, essential for learning.

Cognitive Neuroscience Techniques

Choosing Techniques

  • Evaluate based on spatial and temporal resolution to study brain activity in relation to cognitive tasks.

Electrical Recording Methods

  • EEG: Measures overall brain activity.

  • ERP: Event-related potential linked to specific stimuli; high temporal resolution but poor spatial resolution.

Imaging Techniques

Structural vs. Functional Imaging

  • CT, MRI: For brain structure.

  • PET, fMRI: For brain function - measure neural activity linked to oxygen levels.

Metabolic Imaging

  • PET: Uses radioactive tracers; maps brain activity.

  • fMRI: Monitors blood-oxygen levels, peaks about 5 seconds after stimulation.

Causal Brain-Behavior Relationships

Neuromodulation Techniques

  • TMS: Non-invasive method affecting brain activity to explore cognitive processes.

  • tDCS: Affects neuronal excitability, with limitations in temporal and spatial resolution.

Converging Evidence

Combining Techniques

  • Enhances understanding of cognitive processes, addressing limitations of individual methods.

Evidence from Different Modalities

  • Structural MRI - correlates expertise with brain volume in navigators.

  • fMRI - links navigation performance to hippocampal activity.

Functional Localization of Brain Processes

  • Identifies regions associated with specific functions while emphasizing the importance of connectivity among regions.

  • Examines both functional and structural connectivity.