Unit quiz: Mechanisms beneath the circuit: dendrites, glia, matrix and pruning

Check understanding, separately from reading

5 questions · 80% to pass · no timer. This quiz checks the lessons in this unit. These authored questions assess recognition and application of the taught distinctions, not professional qualification. You may review the lessons and retry. Repeat attempts reuse the question bank; a remembered answer is not proof of transfer to a new situation.

Saving a lesson records reading only. Previous lesson completions have not been converted into passing scores. You can continue reading without a pass; the assessment remains unpassed.

Question 1

A lab stimulates the same number of spines on a dendrite but rearranges them, first clustered on one branch and then split evenly across two branches, and reports that the somatic depolarisation falls when the inputs are split. Which conclusion is licensed, and what would count against it?The result supports branch-specific supralinear integration, because holding the total number of active inputs constant and changing only their arrangement changed the somatic outcome; it would count against the conclusion if blocking the regenerative conductance left the arrangement effect unchanged, or if the split condition also reduced the underlying AMPA-mediated conductance measured locally.The result shows that the number of active spines is irrelevant to somatic depolarisation, since splitting them across two branches produced a smaller response with the same total input.

Question 2

A study reports that brain-wide knockout of a metabotropic receptor that is enriched in astrocytes reduces a synaptic measure by 25 per cent, and concludes that astrocyte signalling sets the gain of synaptic transmission. A reviewer objects. What is the strongest form of the objection?The objection is that a 25 per cent effect is too small to matter biologically, so the result should be reported as a null finding about astrocyte signalling.A brain-wide knockout cannot attribute the effect to astrocytes, because the receptor may also act in neurons and glia elsewhere, and the change may be a developmental compensation; the design needs cell-type-specific disruption in adulthood plus a within-animal comparison before the astrocyte attribution holds.

Question 3

A commentary states that because digesting perineuronal nets restored plasticity in adult rodent cortex, perineuronal nets are the critical-period switch. Which qualification is most important?The digestion tool removes all chondroitin sulfate chains regardless of sulfation pattern, and adult humans already show small reversible ocular dominance shifts after hours of deprivation, so the matrix is better described as one contributor to a graded brake than as a switch, and the molecular target of the enzyme is unspecified.The qualification is that digestion experiments are invalid because knocking out three of the four lecticans leaves a stainable net, so the matrix cannot be responsible for plasticity.

Question 4

A new study reports 5 doublecortin-positive cells per square millimetre in the dentate gyrus of adult human donors and concludes that adult hippocampal neurogenesis is present and functionally significant. What is the decisive next question?Whether the donors were older than the ones used in the negative studies, because age is the variable that determines whether new neurons are present.Whether the counted cells were identified as neurons by at least two independent immaturity markers plus a morphology criterion, since adult doublecortin signal also labels small round cells in the hilus and white matter that appear non-neuronal, and whether the tissue protocol matched the protocol that produced negative results.

Question 5

A grant reviewer asks you to justify a claim that microglia are required for normal circuit refinement in the mouse visual thalamus. Which evidence would you cite, and what would you concede?Cite the engulfment of retinal terminals by microglia at the peak of the pruning window, its dependence on neural activity and on complement receptor 3 and its ligand C3, and the sustained connectivity deficits produced by disrupting that pathway; concede that the evidence is circuit-specific, that a plausible candidate signal tested negatively for the early phase, and that nothing equivalent has been measured in human tissue.Cite the general principle that immune cells remove excess synapses throughout the developing brain, since microglia carry phagocytic machinery and their engulfment of synaptic material has been documented biochemically.

Continuing does not mark this assessment passed.

Progress stays in this browser, on this device, not an account or cloud backup. Clearing browser data removes it. Visits never count as study. Previous untimed legacy completions are not invented as study days.