Brain and Neuropsychology Notes

The Structure and Function of the Brain and Nervous System

• Divisions of the Nervous System:

  • Central Nervous System (CNS): Brain and spinal cord.
  • Peripheral Nervous System (PNS): Somatic and autonomic systems.

• Functions:

  • CNS: Psychological processes and life maintenance.
  • Spinal Cord: Message transfer to/from brain and PNS; reflex actions (e.g., startle response).
  • PNS: Transmits messages to the body from the brain and vice versa.
  • Somatic System: Sensory information (e.g., visual, auditory) and directs muscle movement; consists of sensory and motor neurons.
  • Autonomic System: Transmits/receives information from organs; divided into sympathetic (increases activity) and parasympathetic (decreases activity) systems.

The Autonomic Nervous System and The Fight or Flight Response

• Fight or Flight Response:

  • Triggered by the autonomic nervous system (ANS), mainly the sympathetic branch.
  • Designed to help individuals manage physical threats and activated during stress when the body perceives a threat.
  • Enables quicker reaction by attacking or running away.

• Stages of the Fight or Flight Response:

  1. Hypothalamus recognizes a threat and sends a message to the adrenal gland.
  2. Adrenal medulla releases adrenaline into the endocrine system and noradrenaline to the brain.

• Bodily Changes Due to Adrenaline and Noradrenaline:

  • Increased heart rate.
  • Muscular tension.
  • Faster breathing rate.
  • Pupil dilation.
  • Reduced function of the digestive and immune systems.

The James-Lange Theory of Emotion

• James-Lange Theory:

  • Emotional experience is the result of perceived bodily changes.
  • Example: We are frightened because we run (not run because we are frightened).
  • We feel sad because we cry or afraid because we tremble.

• Feedback from Bodily Changes:

  • People label their subjective experience based on feedback: "I am trembling, therefore I must be afraid."

• Alternative Explanation:

  • Cannon-Bard theory: The autonomic nervous system responds in the same way to all emotional stimuli, as explained by the fight or flight response.

Neuron Structure and Function

• Types of Neurons:
  • Sensory Neurons: Inform the brain about the external and internal environment via the five senses.
  • Motor Neurons: Carry electrical signals to muscles, causing them to contract or relax.
  • Relay Neurons: Connect motor and sensory neurons within the central nervous system.

Hebb's Theory of Learning and Neuronal Growth

• Hebb's Theory:

  • When one neuron sends a signal to another neuron and that second neuron becomes activated, the connection between them is strengthened.
  • "What fires together, wires together."
  • With every new experience, the brain rewires its physical structure (Hebbian learning).

• Long-Term Potentiation (LTP):

  • Hebbian learning occurs through LTP.
  • LTP results in stronger connections between nerve cells and leads to longer-lasting changes in synaptic connections.
  • These changes are responsible for learning and memory.

• Applications and Limitations:

  • Hebb's theory has scientific support and applications in education (e.g., rehearsal to strengthen neural pathways).
  • However, it mainly focuses on structural changes in the brain during learning, ignoring cognitive processes.

The Process of Synaptic Transmission: Release and Uptake of Neurotransmitters

• Synaptic Transmission:

  • The process whereby messages are sent from one neuron to another across a specialized gap called the synapse.
  • Electrical impulse from the neuron is transmitted chemically.

• Steps of Synaptic Transmission:

  1. Electrical nerve impulse travels down the neuron.
  2. Neurotransmitters (e.g., serotonin, dopamine) are released at the pre-synaptic terminal into the synaptic fluid.
  3. Adjacent neurons take up the neurotransmitters from the fluid and convert them into an electrical impulse.
  4. The procedure is then repeated.

• Excitation and Inhibition:

  • Not all messages prompt activation in the same way because it depends on the action potential of the post-synaptic neuron and the message type received.
  • Only certain neurotransmitters can unlock a message channel in certain receptors in the post-synaptic neuron.
  • Lock and key system: the right neurotransmitter has to fit into the right receptor to open up the specific ion channel.
  • Ions flow through the membrane into the neuron along specific pathways.

• Excitatory and Inhibitory Potentials:

  • Excitatory potentials: Make it more likely for the neuron to fire; the synapse is called an excitatory synapse.
  • Inhibitory potentials: Make it less likely for the neuron to fire; the message is likely to be stopped at the post-synaptic neuron, and the synapse is called an inhibitory synapse.

Localisation of Function in the Brain

• Brain Structures:

  • Frontal Lobe: Higher functions such as thinking, decision-making, and planning.
  • Temporal Lobe: Processing auditory information from the ears (hearing).
  • Parietal Lobe: Processing sensory information associated with taste, temperature, and touch.
  • Occipital Lobe: Processing visual information from the eyes.
  • Cerebellum: Balance and coordination.

• Localisation of Function:

  • The view that particular areas of the brain are responsible for specific functions, such as vision and language.
  • Motor area: The primary motor cortex is responsible for movement, whereby it sends messages to the muscles via the brain stem and spinal cord.
  • Somatosensory area: Concerned with the sensation of the body and is situated next to the motor cortex.
  • Visual area: Two visual cortices, one in each hemisphere of the brain; the primary visual cortex is in the occipital lobe (main visual center).
  • Auditory area: Two primary auditory cortices, one in each hemisphere; receive information from both ears via two pathways that transmit information about what the sound is and its location.
  • Language area: Most language processing takes place in Broca's and Wernicke's areas (usually in the left hemisphere).

Penfield's Study of the Interpretive Cortex

• Penfield's Work:

  • Penfield mapped the brain's sensory and motor cortices using neural stimulation.
  • Discovered that the amount of cortical tissue involved in certain functions differs.
  • More sensitive areas (e.g., the face) require a larger proportion of the cortex than others (such as the trunk).

• Penfield Homunculus:

  • Represents the amount of cortical tissue required for different functions.

Cognitive Neuroscience

• Definition:

  • Focuses on the biological basis of thought processes - specifically, how neurons explain thought processes.
  • Relies on theories of cognitive science, neuropsychology, and computer modeling.

• Scanning Techniques to Identify Brain Functioning:

  • fMRI (Functional Magnetic Resonance Imaging): Records the energy produced by molecules of water (detects activity as it occurs).
  • CT or CAT (Computerized Axial Tomography) scan: Uses an X-ray beam to produce a picture of the physiology of the brain (identifies lesions and unusual physiology).
  • PET (Positron Emission Tomography) scan: Produces a moving picture of brain activity using radioactive glucose (indicates which areas are most active).

Tulving's Gold Memory Study

• Purpose:

  1. To investigate the difference in the processing of episodic memory and semantic memory tasks.
  2. To assess the effectiveness of neuroimaging as a means of investigating mental processes.

• Method:

  • Participants were injected with a small amount of radioactive gold and then asked to retrieve episodic and semantic memories.

• Results:

  • Episodic memories resulted in greater activation in the frontal lobes.
  • Semantic memories showed greater activation in the posterior region of the cortex.

Neurological Damage, Motor Abilities, and Behavior

• Impact of Brain Damage:

  • Can cause deficits in motor ability and behavior.

• Stroke:

  • Occurs when there is not enough oxygen going to the brain due to blocked blood vessels or reduced blood flow.
  • The effects depend on where in the brain the damage has occurred.

• Other Brain Damage:

  • Damage due to disease or accidents can impact brain functions, such as short-term memory.

• Case Study: KC:

  • KC suffered damage to his temporal lobes and hippocampus.
  • His semantic memory was intact, but his episodic memory was impaired.
  • Provides evidence of localization of function.