Synaptic Plasticity, Learning, and Memory

Synaptic Rearrangment

A change in the range/effect of presynaptic neurons as a consequence of there activity

Stages of Visual System Development

Prenatal development and postnatal development

Where do the Ocular Dominance Column form

Layer 4C of V1, all the way from the Pia to White Matter

Critical Period

The period where patterns of brain circuitry is most susceptible to environmental refinement (2-4 years in humans)

Strabismus

Unaligned eyes, can cause amblyopia in binocular field if not corrected

Amblyopia

cortical blindess

2 Main mechanisms for ocular dominance columns for form

1. Competition for tissue space between eyes

2. Cooperation (synchronous bursts) between fibers from the same eye

   Balance is found through neural activity

Hebbs Postulate for Learning

Cells that fire synchronously strengthen, those that don’t are weakened

NDMA receptor mechanism

Both ligand (glutamate) and voltage gated. Lets in Ca2+ which activates protein kinase phosphorylation of AMPA receptors and recruits new AMPA receptors. (LTP) Less Ca2+ let in leads to dephosphorylation of AMPA receptors via protein phosphotases. (LTD)

Intrinsic Horizontal Connections

Horizontal connections between neurons allow tissue dedication the change due to lack of competition in lack of external stimulus.

Neighboring cells with similar purposes can more easily influence small adjustments.

Perceptual learning

Requires synaptic plasticity in cortical connections to just to the external environmental stimulus

BCM theory

Weak depolarization lets in a little Ca2+ causing LTD while strong depolorization lets in a lot of Ca2+ casing LTP

Knockout Mice

Removal of NMDA receptor gene impairs LTD and therefor learning

Declarative Memory

Facts and events. Long Term, short term, and working memory. Easy to learn, easy to forget.

2 Types of Nondeclarative Memory

1. Procedural learning and memory: memory of skills, habits, behaviors

2. Associative Learning/memory: Conditioning (Positive/Negative)

Hard to learn, hard to forget

Retrograde Amnesia

Amnesia loss of previous events

Anteriorgrade Amnesia

Inability to form new memories following brain trauma

Medial Temporal Lobe

Important for formation of memory consolidation of declarative memories. Lesion causes anteriorgrade amnesia (H.M) and failure of delayed match to sample tasks.

Hippocampus

Important for spatial learning and memory. Lesion causes rats to explore same corridor (preservation) in Radial Arm Maze and to never learn location of platform in the Morris Water Maze.

Place Cells

CA1 Pyramidal Neurons that fire when an organism pressies they are in a certain place. Bases off of visual and vestibular clues.

Head Direction Cells

Located in postsubiculum, fires when head is in a fixed location with respect to the surrounding environment. Uses visual and vestibular cues.

Grid Cells

Located in Medial Entorhinal Cortex (MEC). Responds when an animal is at multiple locations to form a hexagonal grid. Grid overlap constitutes a positional system.