Psyc (Summary Sheet)

Chps 1-9

What is the typical resting membrane potential of a neuron?

About –70 mV.

Left-brained vs. right-brained idea

The idea is a myth; both hemispheres collaborate for most cognition.

Why resting potential is near K⁺ equilibrium potential

Because K⁺ channels are most permeable at rest (cuz the K⁺ leak channel).

Ion with highest permeability at rest

Potassium (K⁺).

Nernst potential

Voltage where net ion movement is zero.

Sodium–potassium pump

Moves 3 Na⁺ out and 2 K⁺ in.

Role of K⁺ leak channels

Let K⁺ leave the cell, making inside more negative.

Effect of increased extracellular K⁺

Depolarizes (resting potential becomes less negative).

Effect of opening Cl⁻ channels

Hyperpolarization.

Cause of rapid depolarization in action potential

Opening of voltage-gated Na⁺ channels → Na⁺ influx.

Why action potentials travel one direction

Absolute refractory period behind the spike.

Refractory period

Neuron cannot or is less likely to fire again.

Why action potentials don’t weaken

They are regenerated along the axon.

Why myelinated axons conduct faster

Myelin increases conduction speed without needing large diameter.

What white matter contains

Mostly myelinated axons.

Ion that triggers vesicle fusion

Calcium (Ca²⁺).

Ionotropic receptor characteristic

Produces fast postsynaptic responses.

Metabotropic (GPCR) receptor characteristic

Produces slower, longer-lasting responses.

Synaptic plasticity

Changes in synaptic strength due to recent activity.

Dopamine role in reinforcement learning

Signals reward prediction error.

Desensitization

Receptor stops responding even if neurotransmitter is present.

How addictive drugs affect learning

Artificially increase dopamine prediction-error signals.

Why tolerance develops

Receptor desensitization reduces response to dopamine.

Agonist definition

Activates a receptor (e.g., nicotine).

Antagonist definition

Binds without activating a receptor (e.g., naloxone).

Superior–inferior axis

Top-to-bottom orientation.

Anterior/rostral in the brain

Toward the front.

Sagittal plane

Divides brain into left and right halves.

Purpose of gyri and sulci

Increase cortical surface area.

Cytoarchitecture

Organization of neurons by shape, size, arrangement.

Comparative neuroanatomy

Studies similarities/differences across species.

What meta-analyses identify

Consistent brain activation across studies.

Why invasive animal methods are valuable

Reveal mechanisms not possible to study in humans noninvasively.

Representational space

Each neuron’s activity treated as a dimension.

Dimensionality reduction

Makes complex neural data more interpretable.

Calcium imaging

Uses fluorescent indicators to view neural activity.

Optogenetics

Uses light-sensitive channels to control neuron activity.

Goal of brain–computer interfaces

Translate neural activity into external device control.

What EEG measures

Electrical potentials from cortical neurons.

What extracellular recordings measure

Action potentials from nearby neurons.

Time–frequency analysis

Tracks changes in oscillatory power over time.

Slow EEG rhythms meaning

Reflect widespread network coordination.

Slow-wave sleep hippocampal function

Replays experiences to strengthen memory.

Function of photoreceptors (rods and cones)

Detect light and convert it into electrical signals.

Rod specialization

Night (scotopic) vision and motion detection.

Cone photopigments

Short/blue, medium/green, long/red wavelengths.

Where cones are most dense

The fovea.

Function of bipolar cells

Relay signals from photoreceptors to ganglion cells.

Receptive field

Region of sensory space influencing neuron firing.

Retinotopic map

Nearby stimuli activate nearby cortical neurons.

Location of V1

Occipital lobe.

Motor unit definition

One motor neuron + its muscle fibers.

Can one motor neuron innervate multiple fibers?

Yes.

Corticospinal tract function

Controls voluntary movement.

Basal ganglia and cerebellum function

Refine and automate motor skills.

Place Cells

Fire when an animal is in a specific location (“spatiial map”)

Found mainly in CA1 and CA3

Remapping

• Place cells can change their firing locations when the environment changes

• Global remapping: different cell population active

• Partial remapping: some cells keep place fields, others shift

• Supports flexibility in representing new spaces

Beyond Physical Space

Place cells can encode abstract “task states” — not just physical location

• Example: same task, different rules/states → different cell activity

Concept Cells

• Found in human medial temporal lobe

• Respond to specific people, places, or objects across sensory modalities

Imagination

• Hippocampal damage impairs ability to imagine new experiences or future events

• Shows hippocampus is important for constructing scenarios, not only recalling the past

Engram

• Physical substrate of a memory in the brain

• Hippocampus can trigger retrieval of cortical engrams

• Stored in distributed ensembles of neurons

System Consolidation

Gradual transfer of memory dependence from the hippocampus to

distributed networks in the neocortex; Days to years across whole-brain networks

Brain’s navi

Memory Consolidation & Replay

• Consolidation: stabilizing memories over time

• Replay: reactivation of neural sequences during sleep or quiet wakefulness

Grid Cells

• Found in medial entorhinal cortex

• Fire at multiple locations forming a grid-like pattern

• Provide a coordinate system for navigation and possibly abstract spaces

Anterior-Temporal & Posterior-Medial Systems

• Anterior-Temporal (AT): item, object, and semantic information

• Posterior-Medial (PM): context, scenes, and spatial frameworks

• Work together for rich episodic memory

Conjunctive Memory & Factorization

• Conjunctive: bind multiple features into a single memory trace

• Factorization: represent components separately for flexible recombination

• Balances memory specificity with generalization

Cognitive Maps

• Originally described as spatial maps in the hippocampus

• Extend to relational knowledge:

• Social networks

• Task structures

• Conceptual relationships

• Provide a general framework for organizing experiences

Self-control Mechanisms (dlPFC → vmPFC/OFC):

Support healthy decision-making

Common Currency

Enables comparison across qualitatively different rewards

vmPFC/OFC

Encodes subjective value, integrates information into common currency

Devaluation:

Reduced reward value after satiety or negative experience (changes the value associated with the rewards in vmPFC/OFC)

Amygdala

Weighs emotional significance of outcomes à sending inputs to vmPFC/OFC

Temporal Discounting

• Steeper drop at short delays (impulsive choice); Shallower decline at long delays

• Impulsivity = choosing smaller–sooner over larger–later rewards.

• Immediate rewards ↑Striatum; Delayed rewards & self-control ↑ dlPFC → both integrated into

vmPFC/OFC activity

Instrumental Learning

Learning the link between actions and outcomes (reward/punishment). Foundation of adaptive decision-making

Credit Assignment

• Determining which action or event caused an outcome. Misassignment → cognitive biases (e.g., gambler’s

fallacy).

Model-Free Learning (Habitual)

• Fast, automatic; choices driven by past reward history.

Model-Based Learning (Goal-Directed)

• Flexible, uses internal models to simulate outcomes before acting.

Flexible decision adaptation

• Reversal Learning Task - Test the ability to adapt when reward contingencies (%) change.

• vmPFC/OFC Lesions - Patients show impaired flexible adaptation; difficulty updating value-based choices.

Multiplexing & Mixed Selectivity

• Neurons encode multiple features depending on context; increases coding capacity.

Valuation in Gambling Disorder

• Chasing losses, skewed risk evaluation, impulsivity, and delay discounting → maladaptive decisions.

• Hijacking of the dopaminergic reward circuitry → altered sensitivity to wins, losses, and near-misses.