PSYC317 Biopsychology Lecture 4 – Plasticity, Memory, and LTP

Flashcards covering plasticity, memory mechanisms, hippocampal circuits, Lashley vs. Hebb, HM case, and classic LTP experiments.

Why is plasticity important in Biopsychology?

It allows us to adapt to our environment; learning provides an advantage, and learning evolves across species with varying rates of learning.

What does plasticity mean?

The ability to change or the malleability of something.

Who wrote the first textbook on psychology mentioned in the notes?

William James.

What does the red rectangle in the notes indicate?

The information in red is IMPORTANT.

What does the phrase "cells that fire together wire together" describe?

Hebb's rule: repeated co-activation strengthens the synapse.

What does LTP stand for?

Long-Term Potentiation.

Who coined the term 'synapse'?

Sherrington.

Who proposed that memory involves changes in synapse strength?

Cajal.

Who is most responsible for the field of biopsychology?

Donald Hebb.

What is an engram?

The biological trace of memory.

What were Lashley’s two controversial conclusions about memory organization?

Equipotentiality and mass action.

What does equipotentiality mean?

All areas of the cortex are equally capable of being used for learning and memory.

What does mass action mean?

Cortical neurons work together and the extent of tissue lesioned determines the learning deficit; memory is distributed across broad networks.

What was HM known for in the study of memory?

He had bilateral temporal lobe resection which stopped seizures but led to an inability to form new memories.

Was HM’s memory impairment solely due to hippocampus removal?

No; the impairment also involved surrounding cortex associated with the hippocampus.

What are the three synapses of the hippocampal trisynaptic circuit?

Perforant path to dentate gyrus; mossy fibers from dentate to CA3; Schaffer collaterals from CA3 to CA1.

Which input supplies the dentate gyrus in the hippocampus?

The perforant path from the entorhinal cortex.

What are pattern separation and pattern completion in the hippocampus?

Pattern separation keeps information separate in the dentate gyrus; pattern completion binds information together in CA regions to reconstruct memories.

Where is memory binding thought to occur in the hippocampus for recall?

In the CA regions (especially CA3 to CA1 binding).

What role does the entorhinal cortex play in the hippocampal circuit?

It provides major cortical inputs to the hippocampus via the perforant path.

In hippocampal slice experiments, what does the fibre volley (FV) represent?

Presynaptic activity (firing of axons).

What does the field EPSP (eEPSP) reflect in these experiments?

Postsynaptic excitatory response (EPSP) to glutamate.

What does a population spike indicate?

Post-synaptic action potentials from a population of neurons.

How does increasing stimulus intensity affect the fEPSP in these experiments?

It increases both the fibre volley and the magnitude (amplitude/slope) of the fEPSP.

What three components are observed in an evoked hippocampal response?

Fiber volley (pre-synaptic), eEPSP (post-synaptic), and population spike (post-synaptic action potentials).

Who demonstrated that high-frequency stimulation can induce lasting synaptic changes in the hippocampus?

Tim Bliss, Per Andersson, and Terje Lomo in Norway.

What two processes were observed in LTP that did not always correlate perfectly?

Increases in the EPSP and changes in the population spike.

Describe a typical LTP experiment.

Baseline recording, then bursts of high-frequency stimulation, then post-stimulation recording showing an increased slope of the EPSP.

In the Schaffer-CA1 LTP setup, what is stimulated and what is recorded?

Stimulate the Schaffer collateral (CA3→CA1) and record from CA1.

What property makes LTP a plausible memory mechanism?

It is activity-dependent, rapid in onset, long-lasting, and reversible with low-frequency stimulation.

Can LTP be reversed, and if so, how?

Yes—low-frequency stimulation after LTP can bring responses back toward baseline.

Are memories usually accurate, and can there be false memories?

Most memories are relied on by brain activity from external/internal experiences, but false memories can occur.