Cumulative level test: Sensation, regulation and the brain-body boundary: what the pathways do and do not prove

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12 questions · 80% to pass · no timer. This longer test revisits both units in the level. 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.

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Question 1

A functional imaging study reports that activity in V1 varies with the orientation of a grating, and a commentary concludes that V1 is where edges are computed. Separately, a single-unit study reports that V1 cells have oriented receptive fields, and the same commentary treats the two findings as converging. Explain what is established, what is missing from the convergence argument, and why pooling and receptive-field evidence are not the same as implementation evidence.What is established is that V1 activity carries orientation information and that single units are orientation-selective; what is missing is any demonstration of the operation by which the orientation signal is produced or used, since a population response can carry a variable without the region being the site where the operation is implemented.Both findings establish the computation because a response that covaries with orientation and a receptive field tuned to orientation are two independent measurements of the same operation.

Question 2

A listener hears a complex tone whose energy lies at 200, 400 and 600 hertz and reports a pitch corresponding to 200 hertz, even though a control stimulus with energy only at 200 hertz is judged to have a slightly different quality. Design a comparison that would distinguish a place account from a timing account of the reported pitch, and state what each account predicts.Compare loudness judgements for the same complex tones, since a place account and a timing account make opposite predictions about the total energy reaching the cochlea.Compare pitch judgements for complex tones whose fundamental is below the range where phase locking is reliable with tones whose fundamental is inside that range, and add tones in which the lower harmonics are masked or removed; a timing account predicts pitch is preserved while the periodicity is available regardless of where the energy lies on the basilar membrane, whereas a place account predicts the judgement follows the position of maximal excitation.

Question 3

A study finds that the cortical territory devoted to the fingertip is much larger per square centimetre of skin than the territory devoted to the forearm, and concludes that the fingertip representation has higher spatial resolution. A second study finds that fingertip two-point discrimination thresholds are much finer than forearm thresholds. Explain how the two findings relate, and identify the step in the reasoning that is not licensed by either measurement alone.The territory difference is a magnification claim about how much cortex is allocated per unit of skin, and the threshold difference is a behavioural resolution claim; both are consistent with denser innervation and smaller receptive fields at the fingertip, but neither alone establishes that the cortical territory is what produces the finer resolution, since receptor density and peripheral convergence could account for the thresholds without any cortical contribution.The findings establish the same claim from two directions, because more cortical territory necessarily produces finer discrimination at the corresponding skin site.

Question 4

In a controlled experiment, a local anaesthetic block of a peripheral nerve in a person with chronic limb pain reduces reported pain substantially but not completely. One investigator says this proves the pain was nociceptive; another says it proves nothing about mechanism. Using the necessity and sufficiency distinction, adjudicate.The block proves the pain was nociceptive, since blocking nociceptive fibres reduced the pain and any remaining report must be measurement error.The block is evidence that input through that nerve contributed to the pain, which is a partial necessity finding for that pathway, and it does not establish the mechanistic descriptor, because the residual pain shows that other contributions are present and because a modulation framework predicts exactly this partial reduction.

Question 5

An engineer builds a balance aid that reports body tilt by averaging signals from a fluid sensor whose output decays over several seconds and from a camera that measures the visual horizon. During a long constant-velocity turn the aid reports a tilt that is not present. Explain the cause in terms of the signals available, and state why a purely reflexive correction loop cannot fix the problem on its own.The fluid sensor reports angular acceleration rather than position and its output decays with a time constant, so during prolonged motion it supplies a misleading residual signal that the average treats as evidence; a reflexive loop using that signal would generate a correction that is wrong for the same reason, so the aid needs a gravity-referenced or independent position cue to resolve the ambiguity.The averaging step is at fault because averaging two signals always produces an intermediate value, and the correct remedy is to use the camera alone at all times.

Question 6

A commentary states that an experiment recorded a scalp potential beginning several hundred milliseconds before a voluntary movement and a reported awareness of intention about 200 milliseconds before the movement, and concludes that the brain decides before the person is aware. Reconstruct the argument as the commentary states it, then identify the two inferential steps that the source material does not licence.The commentary's argument is sound because the scalp potential and the reported awareness time were measured independently of one another, which rules out any shared measurement error.The commentary infers that the onset of an averaged scalp potential marks the moment of a specific decision in each trial, and that the participant's report of awareness is an accurate timing measure; the first step ignores that averaging stochastic activity accumulating to a threshold produces a similar ramp without a discrete decision event, and the second ignores that the report derives from a subjectively judged clock position over intervals of a few hundred milliseconds.

Question 7

A magazine article states that inflammation in the body causes low mood, citing a study in which people with higher circulating inflammatory markers reported more symptoms of low mood. Explain what the design supports, and correct the single-molecule framing using the idea of coordinated sickness behaviour and dose- and timing-dependence.The design supports an association between a marker of inflammation and reported mood symptoms in the sample studied, and it does not establish that inflammation causes the mood change; the single-molecule framing is also wrong because immune signals act through several routes and produce coordinated changes whose expression depends on dose, timing and context rather than on one substance producing one feeling.The design establishes causation because the inflammatory markers were measured objectively with an assay rather than being self-reported.

Question 8

Two frameworks are applied to the same data on body temperature and body weight. For temperature, a raised regulated level during fever explains why a person feels cold while their temperature climbs; for weight, a settling-point account explains why mass changes when the environment changes and then rests at a new value. A student concludes that because both frameworks use feedback, they are the same claim. Diagnose the error and state what distinguishes them observationally.They are the same claim, because any system with negative feedback necessarily has a target value at which the feedback error is zero.Both frameworks do use feedback, so similarity of mechanism is not the difference; what distinguishes them is whether a specific target value is encoded and defended, which predicts a return to the original value after the condition that produced the deviation is removed, whereas a settling account predicts rest at a new value determined by the balance of inflows and outflows.

Question 9

A study of rotating shift workers reports both reduced total sleep and disrupted circadian timing, and finds that metabolic measures are worse in the group with greater timing disruption even after statistically controlling for sleep duration. A reader objects that controlling for duration is meaningless because the two variables are correlated. Assess the objection and state what would strengthen the timing account.The objection is partly right that a statistical control in a correlated observational design cannot cleanly separate the two variables, and the timing account would be strengthened by a design that manipulates timing while holding sleep opportunity constant, or by a measure of internal phase such as a marker rhythm collected alongside sleep duration.The objection is wrong because statistical control is the definitive method for separating correlated variables, so the study already establishes that timing rather than duration is responsible.

Question 10

A grant application states that the proposed work will show how the brain computes a specific decision, and describes a plan to record activity from many neurons during the decision task and to fit a model to the recorded activity. Using the criteria for a computational claim and the processor demonstration, state what the plan can and cannot deliver, and rewrite the aim so that it is falsifiable.The plan delivers the computational account because a model fitted to neural activity is by definition the operation that the brain performs.Recording and fitting can deliver a description of how well the recorded activity predicts the decision and which variables the activity tracks, and it cannot deliver an implementation account of the operation, because a fitted model that reproduces the data is compatible with several generating mechanisms and the processor demonstration shows that a system can be structurally characterised without its function being recovered; a falsifiable aim names the prediction the computational account makes that a non-computational account does not and the manipulation that would test it.

Question 11

A clinical service wants to use a questionnaire score to decide which patients need further assessment for a condition characterised by unusual internal sensations. A statistician points out that the questionnaire measures a belief about the body rather than sensitivity, and that the underlying construct has been argued to comprise distinct components. Explain what this implies for the intended use, and why the distinction matters more for individual decisions than for group averages.If the instrument indexes a belief rather than sensitivity, then a high score identifies people who report unusual internal sensations rather than people with a particular underlying mechanism, so using it to route individuals presumes a correspondence between construct and measure that the instrument does not establish; for group averages a shared mismatch would tend to cancel less visibly than for individual decisions, where a single misclassification has a direct consequence.The distinction does not matter for either use, because a questionnaire that correlates with the construct is a valid instrument for individual decisions as well as for group comparisons.

Question 12

Design a study that could distinguish three competing accounts of a bodily sensation reported by healthy participants: a peripheral-input account, a predictive or modulatory account, and a timing account in which the sensation depends on when an internal clock signal is sampled. State for each account one prediction that at least one of the others does not make, and name the single measurement that would be most informative if only one could be taken.The peripheral account predicts that the sensation scales with the measured stimulus, while the other two accounts make no testable predictions and are therefore not scientific alternatives.The peripheral account predicts that the sensation scales with the independently measured stimulus or afferent signal; the predictive account predicts that manipulating expectation or context changes the sensation while the measured stimulus is held constant; the timing account predicts that the sensation varies with the phase at which the stimulus is delivered relative to a separately measured internal rhythm; the most informative single measurement is an independent record of the peripheral or physiological signal delivered, because without it none of the three accounts can be compared with the input that is being explained.

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